Steel Bumper Systems For Passenger Cars And Light Trucks Product

STEEL BUMPER
SYSTEMS
for PASSENGER
VEHICLES
and LIGHT
TRUCKS
Fifth Edition, May 2013
An in-depth report on
steel bumper systems,
including information on:
• Material Properties
• Manufacturing
• Product Design
www.autosteel.org

Steel Bumper Systems for
Passenger Cars and Light Trucks
Fifth Edition
May 2013
Steel Market Development Institute

Copyright © Steel Market Development Institute
This publication is for general information only. The information in it
should not be used without first securing competent advice with
respect to its suitability for any given application. The publication of
the information is not intended as a representation or warranty on
the part of Steel Market Development Institute - or any other person
named herein - that the information is suitable for any general or
particular use or freedom from infringement of any patent or patents.
Anyone making use of the information assumes all liability from such
use.
First Edition, June 1998
First Edition (revision), March 2001
Second Edition, February 2003
Third Edition, June 2006
Fourth Edition, May 2011
Fifth Edition, May 2013

Contents
Contents
Figures
Tables
Preface
Introduction
Objective
i
vi
viii
ix
x
xiii
1. Bumper systems and components
1.1 Bumper systems 1-1
1.1.1 System selection
1.1.2 Metal facebar system
1.1.3 Plastic fascia and reinforcing beam system
1.1.4 Plastic fascia, reinforcing beam and energy absorption system
1.2 Bumper components 1-3
1.2.1 Fascia
1.2.2 Energy absorbers
1.2.3 Facebar
1.2.4 Reinforcing beam
1.3 Types of Bumper Beams 1-5
1.3.1 Steel Reimforcing Beams
1.3.2 Steel Facebars
1.3.3 Plastic Reinforcing Beams
1.3.4 Aluminum Reinforcing Beams
2. Steel materials 2-1
2.1 Introduction 2-1
2.2 Typical properties of steel grades for facebars 2-2
2.3 Typical properties of steel grades for brackets, supports, and reinforcing beams 2-2
2.4 FutureSteelVehicle Materials Portfolio for Automotive Applications 2-5
2.5 Elongation versus tensile strength 2-5
2.6 Elongation versus after-fabrication yield strength 2-6
2.7 Elongation versus tensile strength for hot-formed steel 2-11
2.8 Yield strength versus strain rate 2-12
2.9 Sheet steel descriptors 2-14
2.10 SAE J2329 Low-carbon sheet steel 2-15
2.10.1 Steel grade
2.10.2 Types of cold rolled sheet
2.10.3 Types of hot rolled sheet
i

Contents
2.11 SAE J2340 Dent resistant, high-strength and ultra high-strength sheet steel 2-16
2.11.1 Steel grade
2.11.2 Steel type
2.11.3 Hot rolled, cold reduced and metallic coated sheet
2.11.4 Surface conditions for cold reduced and metallic coated sheet
2.11.5 Conditions for hot rolled sheet
2.12 SAE J1562 Zinc and zinc-alloy coated sheet steel 2-18
2.12.1 Galvanizing processes
2.12.2 Types of coatings
2.12.3 Coating mass
2.12.4 Surface quality
2.12.5 Coated sheet thickness
2.12.6 Coating designations
2.13 SAE J403 Carbon steel chemical compositions 2-20
2.13.1 Carbon sheet steel
2.13.2 Boron sheet steel
2.14 SAE J405 Wrought stainless steels 2-21
2.15 SAE Specification and ordering descriptions 2-22
2.16 ASTM A463 Aluminized sheet steel 2-24
3. Manufacturing processes
3.1 Stamping 3-1
3.1.1 Stretching
3.1.2 Drawing
3.1.3 Bending
3.1.4 Bending and straightening
3.1.5 Forming limits
3.2 Roll forming 3-4
3.3 Hydroforming 3-6
3.4 Hot forming 3-7
ii

Contents
3.5 Bumper beam coatings 3-8
3.5.1 Zinc or zinc-iron coatings
3.5.2 Aluminum coating
3.5.3 Polishing
3.5.4 Chromium coating
3.5.5 Conversion coating
3.5.6 Electrocoating (E-coating)
3.5.7 Paint coating
3.5.8 Autodeposition coating
3.5.9 Powder coating
4. Manufacturing considerations
4.1 Forming considerations 4-1
4.1.1 Guidelines for roll forming high-strength steel
4.1.2 Guidelines for roll forming ultra high-strength steel
4.1.3 General guidelines for stamping high-strength
and ultra high-strength steels
4.1.4 Guidelines for hat sections stamped from
high-strength or ultra high-strength steels
4.1.5 Rules of thumb for high-strength steel stampings
4.2 Welding considerations 4-21
4.2.1 Steel chemistry
4.2.2 High-strength and ultra high-strength steels
4.2.3 Welding processes
4.2.3.1 Gas metal arc welding (GMAW)
4.2.3.2 Flux cored arc welding (FCAW)
4.2.3.3 Resistance spot welding (RSW)
4.2.3.4 Resistance projection welding (RPW)
4.2.3.5 Resistance seam welding (RSeW)
4.2.3.6 Resistance projection seam welding (RPSeW)
4.2.3.7 High frequency and induction resistance seam welding (RSeW-HF&I)
4.2.3.8 Upset welding (UW)
4.2.3.9 Friction welding (FRW)
4.2.3.10 Laser beam welding (LBW)
4.2.3.11 Laser beam and plasma arc welding (LBW/PAW)
4.2.4 Weldability of bumper materials
4.2.5 Ranking of welding processes
iii

Contents
5. Design concepts
5.1 Sweep (roll formed sections) and depth of draw (stampings) 5-1
5.2 Tailor products 5-1
5.3 Latest benchmark bumper beams 5-7
5.4 Bumper weights, materials and coatings 5-14
5.5 Current steel bumper design - passenger cars 5-32
5.5.1 Typical bumper design - North American passenger cars
5.5.2 Typical bumper design - North American and Europe passenger cars
5.6 Current steel bumper design - pickups, full size vans and sport utilities 5-34
5.7 Auto/Steel Partnership high speed steel bumper design - North American passenger cars 5-36
5.7.1 Quantech design criteria for high speed steel bumper system
5.7.2 Flow Chart for high speed system
5.8 Bumper design for pedestrian impact 5-39
5.8.1 Impact tests
5.8.2 EuroNCAP leg to bumper impacts with a “leg-form” impactor
5.8.3 Government regulations
5.8.4 Design approaches
5.8.4.1 Cushioning the impact
5.8.4.2 Supporting the lower limb
5.8.5 Design solutions
6. Relevant safety standards in North America and Europe 6-1
6.1 United States National Highway Traffic Safety Administration (49CFR),
Part 581 Bumper Standard 6-2
6.1.1 Requirements
6.1.2 Vehicle
6.1.3 Pendulum corner impacts
6.1.4 Pendulum longitudinal impacts
6.1.5 Impacts into a fixed collision barrier
6.2 Canadian Motor Vehicle Safety Regulations Section 615 of Schedule IV 6-6
6.2.1 Requirements
6.3 United National Economic Commissions for Europe – ECE Regulation 42 6-6
6.3.1 Requirements
6.3.2 Test Vehicle
6.3.3 Impact device
6.3.4 Longitudinal test procedure
6.3.5 Corner test procedure
iv

Contents
6.4 Insurance Institute for Highway Safety: Bumper Test Protocol (Version VII) 6-9
6.4.1 Requirements
6.4.2 Test vehicles
6.4.3 Impact barrier
6.4.4 Full-overlap impact
6.4.5 Corner impact
6.5 Consumers Union bumper-basher tests 6-13
6.6 Research Council for Automotive Repairs (RCAR) Low-Speed Offset Crash Test 6-13
6.6.1 Requirements
6.6.2 Test vehicle
6.6.3 Front impact
6.6.4 Rear impact
6.7 Research Council for Automotive Repairs (RCAR) Bumper Test 6-17
6.7.1 Requirements
6.7.2 Bumper barrier
6.7.3 Full overlap impact
7. Summary/Conclusions 7-1
8. References 8-1
v

Figures
NORTH AMERICAN BUMPER SYSTEM MARKET SHARE
BY UNITS FOR KNOWN SYSTEMS
xii
1.1 COMMON BUMPER SYSTEMS 1-2
1.2 COMMON REINFORCING BEAM CROSS SECTIONS 1-6
2.1 ELONGATION VERSUS TENSILE STRENGTH 2-9
2.2 INCREASE IN YIELD STRENGTH THROUGH WORK HARDENING AND BAKE
HARDENING 2-10
2.3 TRANSITIONS IN HF STEEL 2-11
2.4 STRESS VERSUS STRAIN AT DIFFERENT STRAIN RATES FOR DP 600 2-13
2.5 STRESS VERSUS STRAIN AT DIFFERENT STRAIN RATES FOR DP 600 2-13
3.1 TYPICAL CIRCLE GRID PATTERN 3-2
3.2 REPRESENTATION OF STRAINS BY ETCHED CIRCLES 3-2
3.3 TYPICAL FORMING LIMIT DIAGRAM 3-5
4.1 a) RULES OF THUMB - SPRINGBACK 4-4
4.1 b) RULES OF THUMB - SPRINGBACK 4-5
4.1 c) RULES OF THUMB - SPRINGBACK 4-6
4.2 RULES OF THUMB - DIE FLANGE STEELS 4-7
4.3 RULES OF THUMB - HAT SECTION 4-8
4.4 RULES OF THUMB - RADIUS SETTING 4-9
4.5 a) RULES OF THUMB
- COMBINATION FORM AND FLANGE DIE 4-10
4.5 b) RULES OF THUMB
- COMBINATION FORM AND FLANGE DIE 4-11
4.6 RULES OF THUMB - FORMING BEADS 4-12
4.7 RULES OF THUMB - FORMING AN EMBOSS 4-13
4.8 RULES OF THUMB - EDGE SPLITTING 4-14
4.9 RULES OF THUMB - PART DESIGN 4-15
4.10 RULES OF THUMB - DIE CONSTRUCTION 4-16
4.11 RULES OF THUMB - DEVELOPED BLANKS 4-17
4.12 RULES OF THUMB - TRIMMING 4-18
4.13 RULES OF THUMB - DIE SHEAR 4-19
4.14 GAS METAL ARC WELDING (GMAW) 4-24
4.15 FLUX CORED ARC WELDING (FCAW) 4-27
4.16 RESISTANCE SPOT WELDING (RSW) 4-29
4.17 RESISTANCE PROJECTION WELDING (RPW) 4-29
4.18 RESISTANCE SEAM WELDING (RSeW) 4-33
4.19 RESISTANCE PROJECTION SEAM WELDING (RPSeW) 4-33
4.20 HIGH FREQUENCY AND INDUCTION RESISTANCE SEAM WELDING
(RSeW-HF&I) 4-36
4.21 UPSET WELDING (UW) 4-36
4.22 FRICTION WELDING (FRW) 4-40
4.23 LASER BEAM WELDING (LBW) 4-40
4.24 HARDNESS IN HEAT-AFFECTED ZONE OF ARC WELDS 4-46
4.25 RESISTANCE SPOT WELDING COMPARISON 4-47
5.1 DEFINITION OF SWEEP 5-2
5.2 DEFINITION OF DEPTH OF DRAW 5-5
5.3 EXAMPLES OF TAILOR WELDED BLANKS 5-6
5.4 ROLL FORMED BEAMS 5-8
5.5 STAMPED FACEBARS 5-9
5.6 HOT-STAMPED BEAMS 5-10
vi

Figures
5.7 SHEET HYDROFORMED FACEBAR 5-11
5.8 TYPICAL BUMPER DESIGN FOR PASSENGER CARS AND MINIVANS 5-35
5.9 AUTO/STEEL PARTNERSHIP BUMPER DESIGN FOR HIGH SPEED SYSTEM
NORTH AMERICAN PASSENGER CARS 5-38
5.10 EuroNCAP PEDESTRIAN TESTS 5-42
5.11 EuroNCAP LEG FORM IMPACTOR 5-43
5.12 EuroNCAP “LEG FORM” IMPACT CRITERIA (2010) 5-44
6.1 IMPACT PENDULUM 6-4
6.2 PENDULUM 6-4
6.3 SAMPLE IMPACT APPARATUS 6-5
6.4 IMPACT DEVICE 6-8
6.5 IIHS IMPACT BARRIER 6-10
6.6 STEEL BUMPER BARRIER 6-11
6.7 STEEL BACKSTOP 6-11
6.8 OVERLAP FOR FRONT CORNER TEST 6-12
6.9 RCAR FRONT CRASH PROCEDURE 6-15
6.10 RCAR REAR CRASH PROCEDURE 6-16
6.11 RELEVANT BUMPER ENGAGEMENT 6-18
6.12 BUMPER BARRIER 6-19
6.13 BUMPER BARRIER WITH BACKSTOP AND ENERGY ABSORBER 6-19
vii

Tables
2.1 STEEL GRADES FOR POWDER COATED, PAINTED AND CHROME PLATED
FACEBARS 2-3
2.2 STEEL GRADES FOR BRACKETS, SUPPORTS AND REINFORCING BEAMS 2-4
2.3 FSV MATERIALS PORTFOLIO 2-7
2.4 FSV MATERIALS PORTFOLIO (continued) 2-8
2.5 SAE J2329 LOW-CARBON COLD ROLLED SHEET — MECHANICAL
PROPERTIES 2-25
2.6 SAE J2329 LOW-CARBON HOT ROLLED SHEET – MECHANICAL
PROPERTIES 2-25
2.7 SAE J2329 LOW-CARBON HOT & COLD ROLLED SHEET –
CHEMICAL COMPOSITION 2-26
2.8 SAE J2340 DENT RESISTANT SHEET STEEL 2-26
2.9 SAE J2340 HIGH-STRENGTH SOLUTION STRENGTHENED AND LOW-ALLOY
SHEET STEEL 2-27
2.10 SAE J2340 HIGH-STRENGTH RECOVERY ANNEALED SHEET STEEL 2-27
2.11 SAE J2340 ULTRA HIGH-STRENGTH DUAL PHASE & MARTENSITE SHEET STEEL 2-28
2.12 SAE J1562 COATING MASS FOR GALVANIZED SHEET STEEL 2-29
2.13 SAE J403 CARBON STEEL COMPOSITIONS FOR SHEET 2-30
2.14 SAE J405 CHEMICAL COMPOSITIONS OF WROUGHT STAINLESS STEELS 2-30
4.1 SAE J2340 STEELS AND STRENGTH GRADES 4-23
4.2 SAE J2340 CHEMICAL LIMITS ON UNSPECIFIED ELEMENTS. 4-23
4.3 RANKING OF WELDING PROCESSES BY BUMPER MATERIAL 4-44
5.1 SWEEP NUMBERS (CAMBER, X, INCHES). 5-3
5.2 SWEEP NUMBERS (CAMBER, X, MILLIMETERS). 5-4
5.3 LATEST BENCHMARK BUMPER BEAMS. 5-12
5.4 ROLL FORMED BUMPER BEAMS - 2009 MODEL YEAR 5-15
5.5 STAMPED FACEBARS - 2009 MODEL YEAR 5-23
5.6 HOT FORMED BUMPER BEAMS - 2009 MODEL YEAR 5-27
viii

Preface
This publication is the fourth revision of Steel Bumper Systems for
Passenger Cars and Light Trucks. It is a living document. As
experience in its use is gained, further revisions and expansions
will be issued. The standards discussed in this document refer to
the editions of the standards as of January 2013.
Please note in the event that these standards are replaced by
newer editions, users of this document are encouraged to
investigate the possibility of using the most recent standards. In
some cases new vehicles may adopt new edition standards,
while current venicles may continue to use the standard edition
in place at the time of vehicle development.
This publication brings together materials properties, product design
information, manufacturing information and cost information. It
has been prepared to suit the needs of OEM bumper stylists,
bumper engineers and bumper purchasers. It is also intended to
suit the needs of the Tier 1 and Tier 2 bumper suppliers and steel
industry marketing personnel.
This publication was prepared by the Bumper Project Group of the
Steel Market Development Institute. The efforts of the following
members are acknowledged:
AK Steel Corporation
AGS Automotive Systems
Amino North America Corporation
ArcelorMittal USA LLC
Benteler Automotive
Cosma International
Chrysler Group LLC
Flat Rock Metal Inc.
Flex-N-Gate
Ford Motor Company
General Motors Company
Multimatic Engineering Services
Nucor Corporation
Shape Corporation
ThyssenKrupp Steel USA
United States Steel Corporation
Steel Market Development Institute
May 2013
ix

Introduction
In 2012, approximately 12.8 million vehicles were sold in North
America with 25.6 million bumpers attached. Approximately
83% of these bumpers were steel, approximately 16% were
aluminum, and less than 1% were composites. Today there is an
increased use of ultra high strength steels (UHSS) which make
steel bumpers more mass competitive while also making it more
difficult to justify the additional cost of alternative materials.
Bumper systems have changed dramatically over the last 30
years. More demanding government regulations and different
styling concepts have resulted in new designs.
Steel bumper systems fall into two categories: beams and facebars.
Bumper beams are either roll-formed, hot-stamped, or use
a combination of both manufacturing processes. For example,
the 2011 Ford Mustang bumper beams have roll-formed closed
sections that are subsequently hot-stamped and direct water
quenched. Unlike bumper beams, facebars are exposed and
have an internal supporting structure. They are all stamped
except for the 2011 Ford Raptor bumper which is sheet
hydroformed.
Roll-formed bumpers are the most common type in North
America with approximately 72% of the steel bumper market.
They are usually manufactured from cold rolled uncoated UHSS
with a tensile strength range of 860 to 1500 MPa and a thickness
range of 1.1 to 2.0 mm. The most common UHSS grades
currently used for roll-formed bumpers are recovery annealed,
DP980, and Martensitic Steel.
Hot-stamped bumpers make up approximately 10% of the steel
bumper market in North America. However, they are expected
to gradually gain market share with increased hot-stamping
capacity. Hot-stamped bumpers can be manufactured from
either aluminized coated or uncoated MnB steel with a minimum
tensile strength of 1500 MPa after hot-stamping. Both hot rolled
and cold rolled MnB steels are used for hot-stamped bumpers
with a thickness range of 1.0 to 4.0 mm. Hot stamped bumpers
have the lowest average mass of all steel bumper systems.
Facebars are most commonly used on light-, medium- and heavyduty
trucks. Facebars account for 18% percent of the steel
bumper market and have an internal supporting structure.
Facebars are typically stamped from mild- or high-strength
low-alloy steels with tensile strengths up to 500 MPa and a
thickness range of 1.6 to 2.3 mm. Since facebars are exposed,
cold-rolled steel is typically used to improve surface quality and
coating appearance. Facebars are polished either prior to or after
stamping, or both, and then chromed or painted on the exposed
surfaces, depending on customer preference.
x

Steel is well positioned in the bumper system market with 83%
market share. However, the graphs on page xii show that aluminum
is starting to gain ground as mass reduction becomes more
important to automotive OEMs. Steel bumpers must be further optimized
due to the strong focus on weight reduction and improving
vehicle fuel economy. This can be accomplished by increasing the
strength levels of UHSS. In the near future, stronger UHSS will be
available with minimum tensile strengths up to 1900 MPa. Work is
also underway evaluating the use of AHSS in bumper facebar
applications. Bumper suppliers will also be looking harder at
advanced manufacturing technologies to reduce mass. These
include, but are not limited to, tailored blanks, tailor welded coils,
tailor rolled blanks, tailor rolled coils, 3D roll-forming, and sheet
hydroforming.
The steel bumper market, at approximately 400,000 tons per year, is
important to the North American steel industry. For this reason, the
Automotive Applications Council of the Steel Market Development
Institute (SMDI) established a Bumper Project Team. SMDI’s Bumper
Project Team is a group of experts from the steel industry, Tier-1
bumper suppliers, and OEMs. The Team is dedicated to keeping
steel the material of choice for bumper applications. They
accomplish this by sharing information related to Bumper
manufacturing processes, steel grades, and regulations, solving
problems associated with steel bumper development, and
completing R&D projects that address new design challenges for
bumpers and/or make them more cost and mass efficient. The
Bumper Project Team prepared this technical information bulletin to
provide fundamental background information on North American
bumper systems.
xi

NORTH AMERICAN BUMPER SYSTEM MARKET
SHARE BY MATERIAL
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
1996 1999 2002 2006 2009
ALUMINUM
2012
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
1996 1999 2002 2006 2009
COMPOSITES
2012
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
1996 1999 2002 2006 2009
STEEL
2012
xii
Source: Ducker Worldwide (Reference 1.1)

Objective
The purpose of this publication is to increase the reader’s
understanding of passenger car and light truck bumper systems.
It is an overview of an automotive component system, which has
undergone significant change in recent years. The information
provided is aimed at automotive industry design, manufacturing,
purchasing and safety related staffs; and steel industry sales and
marketing groups. The emphasis is on materials, design,
manufacturing, government regulations and cost. This
document is intended to give the reader in depth knowledge
regarding the bumper industry. While the attempt is made to
cover all materials, manufacturing methods and bumper
designs, some information may not be present. An emphasis
has been placed on presenting the most common practices and
materials, however additional information has also been
presented to give the reader some ideas for possible future
bumper designs, manufacturing methods and materials. It is a
living document and revisions and additions will be made as
experience is gained. The Bumper Project Group hopes this
publication will increase the reader’s knowledge of bumper
systems and help overcome engineering challenges.
xiii

1. Bumper systems and components
1.1 Bumper systems
1.1.1 System selection
1.1.2 Metal facebar system
There are several factors that an engineer must consider when
selecting a bumper system. The most important factor is the ability
of the bumper system to absorb enough energy to meet the OEMs
internal bumper standard. Weight, manufacturability and cost are
also important factors that engineers consider during the design
phase. The formability of materials is important for high-sweep
bumper systems. Another factor considered is
recyclability of materials, which is a definite advantage for steel.
As shown in Figure 1.1, there are five bumper systems in common
use today:
A. Metal facebar
B. Plastic fascia and reinforcing beam
C.Plastic fascia, reinforcing beam and mechanical
energy absorbers
D.Plastic fascia, reinforcing beam and foam or
honeycomb energy absorber
E. Plastic fascia, reinforcing beam, foam, and mechanical
energy absorbers
A metal facebar system, as shown in Figure 1.1 A, consists of a
single metallic bumper that decorates the front or rear end of a
vehicle and acts as the primary energy absorber in a collison.
The bumper regulations in the United States require passenger cars
to withstand a 2.5 mph (4 km/h) impact at the curb position plus or
minus two inches (50mm) with no visual damage and no damage
to safety related items. The North American OEMs voluntarily
design their passenger car bumpers to withstand a 5 mph (8
km/h) impact with no visual damage and no damage to safety
items. Current facebar systems can only withstand a 2.5 mph (4
km/h) impact at the curb position plus or minus 2 inches (50mm)
with no visual damage and no damage to safety items. For this
reason, the use of current facebar systems is restricted to light
trucks, often to meet voluntary internal OEM design standards.
The aesthetics of facebars match the styling trend for full size
vans, pickups and sport utilities. Thus, most facebars are presently
being applied to these vehicles.
If the voluntary internal OEM design standard for light truck
bumpers were to rise to the 5 mph (8 km/h) voluntary passenger
car standard, then the facebar systems used on full size vans,
pickups and sport utilities would have to be redesigned. For the
reason of weight, such redesigns would likely revert to systems
that employ a reinforcing beam.
1-1

FIGURE 1.1
COMMON BUMPER SYSTEMS
A.
B.
C.
D.
E.
1-2

1.1.3 Plastic fascia and reinforcing beam system
This system, as shown in Figure 1.1 B, consists of a plastic fascia
and a reinforcing beam that is fastened directly to the vehicle frame
or motor compartment rails. It is primarily used for rear bumper
systems in passenger cars since the crash requirements are less
severe and there is less need for mechanical energy absorbers
and foam.
1.1.4 Plastic fascia, reinforcing beam and energy absorption system
Bumper systems with a plastic fascia, reinforcing beam and energy
absorption systems are the most common type of bumper system
in North America. They are used on both front and rear bumper
systems and readily meet the 5 mph (8 km/h) voluntary bumper
standard set by North American OEMs. While most passenger cars,
SUVs, crossovers, and minivans, have this type of bumper system,
the energy absorption method varies. The reinforcing beam always
absorbs a significant amount of energy while additional energy can
be absorbed by mechanical energy absorbers (Fig. 1.1C), foam or
honeycomb (Fig. 1.1D), or both (Fig. 1.1E).
1.2 Bumper components
1.2.1 Fascia
Bumper fascias (Figure 1.1) are designed to meet several
requirements. They must be aerodynamic to control the flow of the
air around the car and the amount of air entering the engine
compartment. They must be aesthetically pleasing to the consumer.
Typical fascias are styled with many curves and ridges to give
bumpers dimension and to distinguish vehicles from competing
models. Another requirement of bumper fascias is that they be easy
to manufacture and light in weight. Virtually all fascias are made
from one of three materials: polypropylene, polyurethane or
polycarbonate.
1.2.2 Energy absorbers
Energy absorbers (Figure 1.1) are designed to absorb a portion of
the kinetic energy from a vehicle collision. Energy absorbers are
very effective in a low speed impact, where the bumper springs
back to its original position. Energy absorber types include foam,
honeycomb and mechanical devices. All foam and honeycomb
absorbers are made from one of three materials: polypropylene,
polyurethane or low-density polyethylene. Mechanical energy
absorbers, also referred to as crush cans, are metallic and sometimes
resemble shock absorbers. Although mechanical energy
absorbers have several times the weight of a foam energy
absorber, they are also capable of absorbing several times the
energy. Most front bumper systems use mechanical energy
absorbers due to higher energy absorption requirements.
1-3

1.2.3 Facebar
Facebars (Figure 1.1) are usually stamped from steel with plastic
or stainless steel trim to dress them up. Steel facebars, for formability
reasons, are usually made from steels with a low to medium yield
strength. Higher strength steels are being investigated for facebars
to reduce the thickness and weight. After stamping, steel facebars
are chrome plated or painted for appearance and corrosion
protection reasons.
1.2.4 Reinforcing beam
The reinforcing beams (Figure 1.1) are key components of the
bumper systems that employ them. Reinforcement beams help
absorb the kinetic energy from a collision and provide protection to
the rest of the vehicle. By staying intact during a collision, beams
preserve the frame. Design considerations for reinforcing beams
include strength, manufacturability, weight, recyclability and cost.
Steel reinforcing beams are usually roll formed or hot stamped
using ultra high-strength steel. Typical cross sections are shown in
Figure 1.2. Roll formed beams are the most common but hot
stamped beams have the lowest average mass of all steel bumper
systems and are becoming more popular as a result. The most
common cross section for roll formed beams is the B-section and
the most common sections for hot stamped beams are box and
hat sections. Sometimes a stamped or roll formed face or back
plate is welded to a roll formed or hot stamped C-section to create
a boxed section. Additional reinforcements are sometimes welded
to reinforcing beams, such as pole protectors and bulkheads.
All steel reinforcing beams receive corrosion protection. Some
beams are made from hot-dip galvanized or electrogalvanized
sheet. The zinc coating on these products provides excellent
corrosion protection. Other beams are protected after fabrication
with a paint system such as E-coat. Since steel reinforcing beams
are becoming stronger and lighter with thinner gauges being
used, more beams are using both zinc coating and E-coating to
meet corrosion protection requirements.
1-4

1.3 Types of bumper beams
1.3.1 Steel Reinforcing Beams
1.3.2 Steel Facebars
1.3.3 Plastic Reinforcing Beams
Steel reinforcing beams are produced using the cold stamping,
hot forming or roll forming processes. The tensile strength of
cold stamped and roll formed beams ranges from 900-1500
MPa (130-218 ksi). The tensile strength of hot stamped beams,
after heating and quenching, ranges from 1200-1400 MPa
(174-203 ksi). All steel beams have an elastic modulus of
207,000 MPa (30,000 ksi). Steel reinforcing beams are protected
from corrosion by zinc coatings, aluminum coatings or
electrocoatings. After mounting to a vehicle frame, reinforcing
beams are covered by cosmetic or energy absorbing fascias.
Steel facebars are typically cold stamped from low-carbon and
high-strength steels having tensile strengths from 350-500 MPa
(50-72 ksi) and an elastic modulus of 207,000 MPa (30,000 ksi).
They are either chrome plated or painted for corrosion protection
and appearance before being mounted to a vehicle’s frame.
Most facebars are dressed up with plastic trim.
There are two types of plastic beams — glass reinforced plastic
or unreinforced plastic. Examples of glass reinforced plastic
beams include polypropylene (compression molded),
unsaturated polyester (compression molded) and polyurethane
(reaction injection molded). Examples of unreinforced plastic
beams include polycarbonate/polybutylene (injection or blow
molded), polyethylene (blow molded) and polypropylene (blow
molded). Plastic beams have tensile strengths up to 275 MPa
(40 ksi) and flexural moduli up to 15,000 MPa (2,200 ksi).
1.3.4 Aluminum Reinforcing Beams
Typically, aluminum beams are made by stretch or press forming
extruded shapes made from the 6000 and 7000 aluminum
series. After forming and heat treating, the beams have tensile
strengths up to 550 MPa (80 ksi) and an elastic modulus of
69,000 MPa (10,000 ksi).
1-5

FIGURE 1.2
COMMON REINFORCING BEAM CROSS SECTIONS
Roll Formed Box Section
Hat Section
Roll Formed ‘C’
Channel Section
Hat Section Welded
to Face or Back Plate
Roll Formed ‘B’ Section
1-6

2. Steel materials
2.1 Introduction
Flat rolled steels are versatile materials. They provide strength and
stiffness with favorable mass-to-cost ratios, and they allow high
speed fabrication. In addition, they offer excellent corrosion
resistance when coated, high energy absorption capacity, good
fatigue properties, high working hardening rates, aging capability,
excellent paintability, and complete recyclability. These characteristics,
plus the availability of high-strength and ultra high-strength steels,
have made sheet steel the material of choice in the automotive
industry.
Numerous steel types and grades offer designers a wide choice for
any given application. Bumper steels with elongations up to 50%
facilitate forming operations. Bumper steels with tensile strengths
over 1900 MPa (280 ksi) facilitate mass reduction.
Low-carbon steels have excellent ductility. They are widely used
for body and underbody components that are formed by stamping,
roll forming or hydroforming. However, in order to reduce
component mass, low-carbon steels are gradually being replaced
by steels of greater strength. As the name implies, dent resistant
steels are commonly used for body panels such as quarter, door
and hood. Their relatively low as-received yield strength facilitates
forming. Cold work of forming and bake hardening during the
automotive paint cycle increase their yield strength and dent
resistance. Microalloy steels usually have less ductility than lowcarbon
and dent resistant steels. However, they can be supplied
with the necessary ductility to produce most automotive parts.
Carbon-Boron steel has good formability and high yield strength
after heat treating. Dual phase steel also offers good formability. Its
strength increases significantly through cold work during the
fabrication process. Recovery annealed and martensitic steels have
ultra high yield strengths. However, their formability limits their use
to roll formed sections and less severe stampings. Stainless steels
offer excellent corrosion resistance, excellent formability and high
yield strength.
2-1

2.2 Typical properties of steel grades for facebars
The steel grades that are commonly used for facebars are shown with
their typical properties in Table 2.1. Most facebars are made from highstrength
steel [minimum yield strength higher than 240 MPa (35 ksi)].
Although dual phase steels are not listed in Table 2.1, successful trials
have been completed and facebars are expected to switch over to this
grade for mass reduction.
For comparative purposes, Table 2.1 also includes similar SAE grades.
The Society of Automotive Engineers (SAE) designates SAE steel
grades. These are four digit numbers which represent chemical
composition standards for steel specifications. It is important to note
that the similar SAE grades are not equivalent grades. That is, there are
minor differences between the SAE grades and the common grades to
which they are similar. The differences might be significant in some
applications. Some OEM’s specify grades that can be proprietary in
nature.
Facebars, due to their depth of draw and complex shape, are
produced by the stamping process. Steels of high formability are
required and all of the grades shown in Table 2.1 can be supplied to
meet the demanding requirements of a facebar stamping. Facebars are
either powder coated, painted or chrome plated and a high-quality
surface is required on the steel sheet. In addition, the majority of
the sheet steel used for plated facebars is flat polished prior to the
stamping operation.
2.3 Typical properties of steel grades for brackets, supports and reinforcing beams
The steel grades that are commonly used for brackets, supports and
reinforcing beams, are shown with their typical properties in Table 2.2.
Most reinforcing beams are made from ultra high-strength steel
[minimum tensile strength greater than 550 MPa (80 ksi)].
For comparative purposes, Table 2.2 also includes similar SAE grades.
It is important to note that the similar SAE grades are not equivalent
grades. That is, there are minor differences between the SAE grades
and the common grades they are similar to. The differences might be
significant in some applications.
All of the high-strength steel grades in Table 2.2 can be supplied with
sufficient formability for the production of stamped brackets, supports
and reinforcing beams. They can also be readily roll formed into
reinforcing beams.
Generally speaking, the ultra high-strength steel grades in Table 2.2
have less formability than the high-strength grades listed. However,
they offer significant weight reduction opportunities and are
commonly used for less severe stampings and roll formed reinforcing
beams. Grades 120XF and 135XF have sufficient ductility to produce
stampings, including reinforcing beams, provided the amount of draw
is minimal. Grade 140T has a relatively low as-delivered yield strength,
which facilitates stamping and roll forming operations. An advantage
of this grade is the fact it work-hardens significantly during forming. In
fact, the yield strength after forming approaches 965 MPa (140 ksi).
Thus, 140T offers sufficient formability to produce roll formed beams
with a large sweep and it provides high yield strength in the finished
part. Grades 140XF and M130HT through M250HT have low formability
and their use is generally restricted to roll formed reinforcing beams
since roll forming is a process of gradual bending without drawing.
The Carbon-Boron grades can be used to produce complex parts
through the hot stamping process. After quenching, the parts have
yield strengths up to 1300 MPa (190 ksi) and tensile strengths up to
2000 MPa (290 ksi). The stainless steel grades are readily stamped or
roll formed. Their excellent corrosion resistance eliminates the need
for protective coatings.
2-2

TABLE 2.1
STEEL GRADES FOR POWDER COATED, PAINTED & CHROME PLATED FACEBARS
TYPICAL PROPERTIES AS-SHIPPED FROM THE STEEL MILL
MATERIAL
GRADE
(COMMON
NAME)
DESCRIPTION
TYPICAL
YIELD
STRENGTH
MPa (ksi)
TYPICAL
TENSILE
STRENGTH
MPa (ksi)
TYPICAL
ELONG
(%)
TYPICAL
"n"
VALUE
SIMILAR SAE
GRADE
HR
HR
HR
HR
HR
HR
HR
1008/1010
35XLF
50XLF
55XLF
60XLF
70XLF
80XLF
Low-carbon
Microalloy
Microalloy
Microalloy
Microalloy
Microalloy
Microalloy
269 (39.0)
331 (48.0)
403 (58.5)
439 (63.7)
475 (68.9)
527 (76.5)
587 (85.1)
386 (56.0)
407 (59.0)
480 (69.6)
505 (73.2)
531 (77.0)
600 (87.0)
673 (97.6)
35
35
31
29
27
26
22
0.19
0.17
0.17
0.16
0.15
0.13
0.12
J403 1010
J2329 Grade 2
J2340 340X
J2340 380X
J2340 420X
J2340 490X
J2340 550X
CR
CR
CR
CR
CR
CR
CR
CR
CR
1008/1010
DR210
35XLF
40XLF
50XLF
55XLF
60XLF
70XLF
80XLF
Low-carbon
Dent resistant
Microalloy
Microalloy
Microalloy
Microalloy
Microalloy
Microalloy
Microalloy
296 (42.9)
220 (31.9)
285 (41.3)
315 (45.7)
376 (54.5)
418 (60.6)
459 (66.5)
530 (76.8)
592 (85.8)
331 (48.0)
360 (52.2)
400 (58.0)
425 (61.6)
475 (68.9)
501 (72.7)
527 (76.5)
614 (89.1)
690 (100.0)
35
40
35
33
28
27
26
20
19
0.20
0.20
0.17
0.16
0.15
0.14
0.14
0.12
0.08
J403 1010
J2340 210A
J2329 Grade 2
J2340 300X
J2340 340X
J2340 380X
J2340 420X
J2340 490X
J2340 550X
SS
SS
T301
T204
Austenitic
Austenitic
276 (40)
370 (53.8)
758 (110.0)
689 (100.0)
60
59
0.45
0.44
J405 S30100
J405 S20400
NOTES:
HR
Hot rolled sheet
CR
Cold rolled sheet
1008/1010 Low-carbon commercial quality (CQ). Mechanical properties are not certified.
DR
XLF
SS
Dent resistant quality. Strength increases due to work hardening during forming.
Designation number (e.g. 210) is minimum yield strength in MPa.
Microalloy quality. Strength is obtained through small quantities of alloying elements such as vanadium
and niobium. Designation number (e.g. 50) is minimum yield strength in ksi.
Stainless steel
2-3

TABLE 2.2
STEEL GRADES FOR BRACKETS, SUPPORTS AND REINFORCING BEAMS
TYPICAL PROPERTIES AS-SHIPPED FROM THE STEEL MILL
MATERIAL GRADE DESCRIPTION TYPICAL TYPICAL TYPICAL TYPICAL SIMILAR SAE
SAE
( ((COMMON
YIELD YIELD TENSILE TENSILE ELONG ELONG "n" "n" GRADE GRADE
N NAME) STRENGTH STRENGTH (%) (%) VALUE
VALUE
MPa M (ksi) MPa (ksi)
H
( )
( )
HIGH-STRENGTH STEEL GRADES
HR 50XLF Microalloy 403 403 (58.5) 480 (69.6) 31 0.17 J2340 340X
HR 55XLF Microalloy 439 439 (63.7) 505 (73.2) 29 0.16 J2340 380X
HR 60XLF Microalloy 475 475 (68.9) 531 (77.0) 27 0.15 J2340 420X
HR 70XLF Microalloy 527 527 (76.5) 600 (87.0) 26 0.13 J2340 490X
HR 80XLF Microalloy 587 587 (85.1) 673 (97.6) 22 0.12 J2340 550X
CR
CR
CR
CR
CR
50XLF
55XLF
60XLF
70XLF
80XLF
Microalloy
Microalloy
Microalloy
Microalloy
Microalloy
376 376 (54.5)
418 418 (60.6)
459 459 (66.5)
530 530 (76.8)
592 592 (85.8)
HDG (CR)
HDG (CR)
HDG (CR)
HDG (CR)
50XLF
55XLF
60XLF
80XLF
Microalloy
Microalloy
Microalloy
Microalloy
379 379 (54.9)
415 415 (60.2)
452 452 (65.5)
641 641 (93.0)
ULTRA HIGH-STRENGTH STEEL GRADES
HR 10B21(M) Carbon-Boron
320 (46.4)
475 (68.9) 28 0.15 J2340 340X
501 (72.7) 27 0.14 J2340 380X
527 (76.5) 26 0.14 J2340 420X
614 (89.1) 20 0.12 J2340 490X
690 (100.0) 19 0.08 J2340 550X
453 (65.7) 30 0.17 J2340 340X
492 (71.4) 28 0.16 J2340 380X
531 (77.0) 26 0.15 J2340 420X
662 (96.0) 15 0.11 J2340 550X
480 (69.6) 18 N/A J403 10B21
CR 15B21(M) Carbon-Boron
CR 15B24 Carbon-Boron
330 (47.9)
330 (47.9)
500 (72.5) 27 N/A J403 15B21
500 (72.5) 27 N/A J403 15B24
A Aluminized (CR) 15B21(M) Carbon-Boron
330 (47.9) 500 (72.5) 27 N/A J403 15B21
CR 120XF Recovery Annealed 8698
(126) 883 (128) 12 N/A J2340 830R
CR 135XF Recovery Annealed 9699
(141) 985 (143) 7.0 N/A --
C CR 140XF Recovery Annealed 1010 1 (147) 1028 (149) 5.6 N/A --
HDG (CR) 120XF Recovery Annealed 8768
(127)
889 (129) 11 N/A J2340 700R
CR
CR
CR
140T
590T
780T
Dual Phase
Dual Phase
Dual Phase
CR M130HT Martensitic
CR M160HT Martensitic
CR M190HT Martensitic
CR M220HT Martensitic
EG (CR) M130HT Martensitic
EG (CR) M160HT Martensitic
EG (CR) M190HT Martensitic
EG (CR) M220HT Martensitic
634 (92)
371 (54)
518 (75)
923 (134)
1020 (148)
1214 (176)
1420 (206)
923 (134)
1020 (148)
1214 (176)
1420 (206)
1034 (150)
634 (92)
834 (121)
13
24
18
N/A
N/A
N/A
J2340 950DL
–
–
1055 (153) 5.4 N/A J2340 900M
1179 (171) 5.1 N/A J2340 1100M
1420 (206) 5.1 N/A J2340 1300M
1627 (236) 4.7 N/A J23401500M
1055 (153) 5.4 N/A J2340 900M
1179 (171) 5.1 N/A J2340 1100M
1420 (206) 5.1 N/A J2340 1300M
1627 (236) 4.7 N/A J23401500M
NOTES:
SS T301 1/4 Hard Condition
517 (75)
SS T204 20% Cold Worked 7797
(113)
862 (125) 25 0.25 J405 S30100
1193 (173) 25 0.22 J405 S20400
HR
Hot rolled sheet
CR
Cold rolled sheet
HDG (CR) Hot-dip galvanized (cold rolled base) sheet
EG (CR) Electrogalvanized (cold rolled base) sheet
Aluminized (CR) Hot dip aluminized (cold rolled base) sheet
SS
Stainless steel
XLF
Microalloy quality. Strength is obtained through small quantities of alloying elements such as
vanadium and niobium. Designation number (e.g. 50) is mimimum yield strength in ksi.
..B..(M) Carbon-Boron quality (Modified). Properties are for the steel as-shipped from the steel mill. Strength
is achieved through heating and quenching. After quenching, the yield strength is about 1140 MPa
(165ksi)
..B..
Carbon-Boron quality. Properties are for the steel as-shipped from the steel mill. Strength is achieved
through heating and quenching. After quenching, the yield strength is about 1140 MPa (165ksi)
XF
Recovery annealed quality. Strength is achieved primarily through cold work during cold rolling at
the steel mill. Designation number (e.g. 120) is minimum yield strength in ksi.
140T Dual phase quality. Structure contains martensite in ferrite matrix. Properties are for the steel
as-shipped from the steel mill. Designation number (e.g. 140) is the minimum tensile strength in ksi.
M...HT Martensitic quality. Strength is determined by carbon content. Designation number (e.g. 130) is the
minimum tensile strength in ksi.
N/A Not applicable. The Carbon-Boron steels listed are intended for hot forming. The Recovery
Annealed and Martensitic steels are primarily used in roll forming operations. However, they may be
used for stampings provided the amount of draw is minimal. The “n” value for dual phase steels is
very dependent on the range over which it is calculated.
2-4

2.4 FutureSteelVehicle Materials Portfolio for Automotive Applications
The Future Steel Vehicle (FSV) materials portfolio (Reference 2.1)
summarizes steel grades considered in the design of FSV. All are
commercially available now or will be in the near future. The
AHSS family of products in the portfolio provides a key role for
future automotive applications. The combination of new design
technologies along with emerging steel grades and advanced steel
processing technologies enable optimal component and vehicle
lightweighting. AHSS grade development has been driven by the
need to achieve better performance in crash energy management
with material gauge reduction and subsequent lower mass.
Tables 2.3 and Table 2.4 show the steel grades and their generalized
properties available for future steel vehicle design including facebars,
brackets, supports, and reinforcing beams. There are currently sufficient
worldwide steel products available globally from steel producers to
meet demand.
Detailed information about AHSS grades is available in the
WorldAutoSteel AHSS Applications Guidelines document online at
http://www.worldautosteel.org.
2.5 Elongation versus tensile strength
AHSS (advanced high-strength steel) Guidelines published by
World Auto Steel (www.worldautosteel.org) (Reference 2.2)
provide a comparison between the various families of steel
products in the form of tensile strength versus percent total elongation
(Figure 2.1). The latter is a good measure of the formability for
each material class. Each bubble in the graph represents the
typical properties of all steel products in each category of steels, as
produced by most of the major steel makers around the world.
The steel grades shown in the bubbles are:
• IF (interstitial free) products
• IS (isotropic) products
• Mild (mild steel) products
• BH (bake hardenable) products
• CMn (carbon-manganese and carbon-boron) products
• HSLA (high-strength low-alloy) products
• TRIP (transformation induced plasticity) products
• DP, CP (dual phase, complex phase) products
• AUST. SS (austenitic stainless steel)
• MART (martensitic) products
• Boron (hot stamped steel)
• L-IP (liquid-induced plasticity)
• TWIP (twinning-induced plasticity)
The above bubbles may be placed into four groups: Conventional
HSS (high-strength steel), Stainless Steels, AHSS (advanced highstrength
steel), and UHSS (ultra high-strength steel). A fifth group,
3rd Generation AHSS, is expected to emerge in the near future,
offering ultra high-strengths with higher elongation.
2-5

2.5 Elongation versus tensile strength (continued)
It is clear from the graph that most of the traditional steel products
obey an inverse relationship between strength and ductility.
Bucking this trend are the dual phase and complex phase families
of steel products. These products, although available for at least
twenty-five years, have just recently attracted the attention they
deserve for their excellent combination of higher strength and very
good ductility, making them suitable for energy-absorption
applications. Carrying this concept a step further are the TRIP
(TRansformation Induced Plasticity) steels. Although the principles
underlying these steel products were available and understood at
least thirty years ago, only now are these steels becoming available
for automotive body applications. TRIP steels provide further
enhanced potential for energy absorption at thinner gauges, thus
making it possible for a vehicle structure to provide improved
safety at lower mass.
2.6 Elongation versus after-fabrication yield strength
The above data are all based on tensile properties obtained from
undeformed materials. In actual service the steel sheets are
strained during fabrication, which is known to increase their
strength and decrease their ductility. Many of the formed parts are
also subsequently painted and baked to cure the paint. Although
not all steels respond to the straining and baking process many of
them do. Key among them are the so-called Bake Hardening (BH),
Dual Phase (DP) and TRIP steels. Figure 2.2 shows the yield
strength increase from straining and baking for several steel grades.
This has no significant effect on forming of the steel but it can
certainly affect its performance in service. The effect is usually
beneficial as straining and baking increase the stress levels at which
permanent deformation begins.
2-6

2-7
TABLE 2.3
FSV MATERIALS PORTFOLIO

2-8
TABLE 2.4
FSV MATERIALS PORTFILIO (Continued)

FIGURE 2.1
ELONGATION VERSUS TENSILE STRENGTH
0 300 600 900 1200 2000
Tensile Strength (MPa)
*See Page 2-11 for MnB
2-9

FIGURE 2.2
INCREASE IN YIELD STRENGTH THROUGH WORK HARDENING (WH)
AND BAKE HARDENING (BH)
2-10

2.7 Elongation versus tensile strength for hot-formed steel
The implementation of press-hardened applications and the utilization
of hardenable steels are promising alternatives for optimized part
geometries with complex shapes and no springback issues. Hot
stamped or press hardened steels typically use blanks that are
heated up, formed in a press and rapidly cooled. Hot Formed (HF)
steel is typically boron-based, containing 0.002-0.005 percent
boron, and is usually referred to as “boron steel.” (Reference 2.3)
The processes used to produce boron steel bestow a unique
combination of properties. “Direct hot-forming” may be used to
deform the blank in the austenitic state (at high temperatures) or
“indirect hot-forming” may be used to heat and finish the piece after
most forming is completed at room temperature. In either case, the
steel undergoes a series of transitions in elongation and strength (as
shown in Figure 2.3 below), finishing with a rapid cooling to
achieve the final desired mechanical properties.
Figure 2.3: Boron steel property transitions in direct hot forming
process.
1: Initial, room temperature state where the steel is blanked.
2: Raised temperature state prior to forming.
3: Final strength-elongation achieved after forming and rapid cooling.
In direct hot-forming, the boron-based steel is blanked at room
temperature and then heated to high enough temperature for
austenization. The steel is then formed while hot and quenched in
the forming tool, developing the martensitic microstructure. Some
special post-forming work may be required to finish the pieces,
which are exceptionally high-strength. For indirect-hot forming, the
steel is blanked and pre-formed at room temperature. The part is
then heated and forming is completed while the steel is in this low
strength, high elongation state. A final quench in the die produces
the final properties and shape.
Parts made from boron steel benefit from several material advantages,
including ultra high-strength and improved (reduced) springback.
The part remains in the die through the cooling phase, and so springback
is virtually nonexistent. The use of hot formed boron steel is
growing rapidly due to its ultra high-strength and good forming
properties.
2-11

2.8 Yield strength versus strain rate
More recently, consideration was given to the impact of the rate of
straining of a particular material or component on its performance.
Since steel is a strain rate sensitive material, its yield and tensile
strength increases as the loading rate increases. This provides
further benefits in its ability to sustain and absorb higher loads and
higher input energy, such as in the case of deformation of a
bumper or other structural component. Again, this is not a new
discovery but it was only through the introduction of the advanced
vehicle concepts phase of the ULSAB (UltraLight Steel Auto Body)
development that this benefit of steel began to be introduced in
structural design of automobile components. Considerable effort
was then expended in various laboratories around the world to
generate tensile data at straining rates ranging from quasi-static
(10-3 s-1) to 103 s-1 for many of the above steel grades. The effect
of the higher strain rate on the strength and ductility for TRIP 600
and DP 600 steels is provided in Figures 2.4 and 2.5, respectively.
The data for these steels and other products of interest for bumper
construction are available from many steel producers and can be
made available for use in the design of bumpers and other
energy-absorbing components.
Use of the tensile properties of steels at higher rates of loading has
begun in automotive design and is expected to be universally used
as more data for more steel grades become available and as
automotive designers become more comfortable with the reliability
of this data.
2-12

FIGURE 2.4
STRESS VERSUS STRAIN AT DIFFERENT STRAIN RATES FOR TRIP 600.
THE DATA AT 1000 s -1 WERE OBTAINED USING THE
SPLIT HOPKINSON BAR (SHB) METHOD
FIGURE 2.5
STRESS VERSUS STRAIN AT DIFFERENT STRAIN RATES FOR DP 600.
THE DATA AT 1000 s -1 WERE OBTAINED USING THE
SPLIT HOPKINSON BAR (SHB) METHOD
2-13

2.9 Sheet steel descriptors
Sheet steel is a complex product and there are many methods
used to describe it. The following descriptors are often associated
with automotive sheet steel:
a) Type Chemical composition, microstructure
processing method or end use are all
used to describe the type of steel.
Examples include low-carbon, dent
resistant, microalloy, high-strength low
alloy, recovery annealed, dual phase,
bainitic and martensitic sheet.
b) Grade Physical properties such as yield strength,
tensile strength or elongation are used to
denote a grade. Examples include 180
MPa minimum yield strength and 1500
MPa minimum tensile strength.
c) Steel Product The final process that steel receives
before shipment from a steel mill is often
used to describe a steel product.
Examples include hot rolled, cold rolled
and coated sheet.
d) Metallic Coating The process used to apply a metallic
coating or the type of metal in the
metallic coating are used to describe
steel. Examples include hot-dip
galvanized, electrogalvanized and zinc
coated sheet.
e) Surface Condition Surface smoothness is used to describe
sheet steel. Examples are exposed,
semi-exposed or unexposed body sheet.
In practice, when specifying sheet steel, most (if not all) of the
above descriptors are required to fully describe the desired steel
product. Published documents, such as those of the Society of
Automotive Engineers (SAE) greatly facilitate the correct
specification of sheet steel. In this context, the relevant SAE
documents are:
• Categorization and Properties of Low-Carbon Automotive Sheet
Steels, SAE J2329 (Reference 2.5)
• Categorization and Properties of Dent Resistant, high-strength
and Ultra high-strength Automotive Sheet Steel, SAE J2340
(Reference 6.4)
• Selection of Galvanized (Hot Dipped and Electrodeposited) Steel
Sheet, SAE J1562 (Reference 2.6)
• Chemical Compositions of SAE Carbon Steels, SAE J403
(Reference 2.7)
• Chemical Compositions of SAE Wrought Stainless Steels, SAE
J405 (Reference 2.8)
2-14

2.10 SAE J2329 Low-carbon sheet steel
This SAE Recommended Practice furnishes a categorization
procedure to aid in selecting low-carbon sheet steel. The system
employs four characters. The first two alphabetic characters
denote hot rolled (HR) or cold rolled (CR) method of manufacture.
The third character defines grade (one through five) based on yield
strength range, minimum tensile strength, minimum percent
elongation, minimum rm value, and minimum n-value.
The fourth alphabetic character (E,U,R,F,N or M) classifies the steel
type with regards to surface quality and/or aging character. An
optional fifth character may be used to restrict carbon content to a
minimum of 0.015%. If the sheet steel is a metallic coated
product, then the E-coating would be specified in accordance with
SAE J1562 (see Section 2.10).
Examples of typical specification and ordering descriptions for
automotive sheet steel are given in Section 2.13.
2.10.1 Steel grade
There are five grades of cold rolled sheet and three grades of hot
rolled sheet. Mechanical properties are shown in Tables 2.5 and
2.6, while chemical composition is shown in Table 2.7 (page 2-26).
2.10.2 Types of cold rolled sheet
There are two types of cold rolled sheet, either in the bare or
coated condition:
• E
• U
Exposed. Intended for critical exposed applications where
painted surface appearance is of primary importance.
Unexposed. Intended for unexposed applications.
2.10.3 Types of hot rolled sheet
There are four types of hot rolled sheet, either bare or in the
metallic coated condition:
• R
• F
• N
• M
A coiled product straight off the hot mill, typically known
as hot roll black band.
A processed product in coils or cut lengths. The product
may be susceptible to aging and coil breaks.
A processed product in coils or cut lengths. The product
is non-aging at room temperature but is susceptible to coil
breaks.
A processed product in coils or cut lengths. This product
is non-aging at room temperature and free from coil
breaks.
When specifying a hot rolled sheet, the surface condition should
also be indicated (E or U as per Section 2.8.2).
2-15

2.11 SAE J2340 Dent resistant, high-strength and ultra high-strength sheet steel
2.11.1 Steel grade
This SAE Recommended Practice defines mechanical properties for
dent resistant, high-strength and ultra high-strength sheet steel. The
properties for dent resistant steels are shown in Table 2.8, the
properties for high-strength steels in Tables 2.9 and 2.10, and the
properties for ultra high-strength steels in Table 2.11 (page 2-28).
It should be noted that the yield and tensile strength values for the
ultra high-strength steels covered by J2340 (Table 2.11) are those
commonly used in Europe. For example, J2340 and Europe use
values such as 600, 800, 1000 and 1200. On the other hand,
values such as 590, 780, 980 and 1180 are widely used in North
America and Japan. Currently, SAE’s Iron and Steel Technical
Committee is revising J2340 to cover ultra high-strength steel
grades widely used not only in Europe but also in North America
and Japan.
SAE J2340 also furnishes a categorization procedure to aid in
selecting dent resistant, high-strength and ultra high-strength steels.
The system employs several characters:
• The first two characters denote hot rolled (HR) or cold rolled
(CR) method of manufacture.
• The next three or four characters denote the grade of steel.
Minimum yield strength in MPa is used for dent resistant and
high-strength steels and minimum tensile strength in MPa is used
for ultra high-strength steels. Refer to Tables 2.8 - 2.11. The final
set of characters denotes the steel type. Refer to Section 2.9.2.
If the sheet steel is a metallic coated product, then the E-coating
would be specified in accordance with SAE J1562 (see Section
2.10).
Examples of typical specification and ordering descriptions for
automotive sheet are given in Section 2.13.
In Tables 2.8, 2.9 and 2.10 (dent resistant and high-strength steels)
grade is the minimum yield strength in MPa. In Table 2.11, (ultra
high-strength steels) grade is the minimum tensile strength in MPa.
2-16

2.11.2 Steel type
In Tables 2.6 to 2.9, type is defined by one or two letters as
follows:
• A
• B
• AT, BT
• S
• X
• Y
• SF,XF,YF
• R
• DL
• DH
• M
A non-bake hardenable dent resistant steel in
which increase in yield strength due to work
hardening results from strain during forming.
A bake hardenable dent resistant steel in which
increase in yield strength due to work hardening
results from strain during forming and an
additional increase in yield strength that occurs
during the paint-baking process.
These types are similar to Types A and B
respectively, except that the steel is interstitial
free.
A high-strength steel, which is solution
strengthened using C and Mn in
combination with P or Si.
A high-strength steel typically referred to as HSLA.
It is alloyed with carbide and nitride forming
elements (commonly Nb (Cb), Ti and V) in
combination with C, Mn, P and Si.
A high-strength steel similar to Type X, except the
spread between the minimum yield and tensile
strengths is larger (100 MPa versus 70 MPa).
These types are similar to types S, X and Y
respectively, except they are sulphide inclusion
controlled.
A high-strength steel that has been recovery
annealed or stress-relief annealed. Its strength is
primarily achieved through cold work during cold
rolling at the steel mill.
A dual phase ultra high-strength steel. Its
microstructure is comprised of ferrite and
martensite. The strength level is dictated by the
volume of low-carbon martensite. DL dual phase
has a low ratio of yield-to-tensile strength (less
than or equal to 0.7).
A dual phase ultra high-strength steel similar to
Type DL, except it has a high ratio of yield to
tensile strength (greater than 0.7).
A martensitic ultra high-strength steel whose
carbon content determines the strength level.
2.11.3 Hot rolled, cold reduced and metallic coated sheet
The steels in Tables 2.8 to 2.11 can be specified as either hot rolled
sheet or cold rolled sheet in either the bare or metallic coated
condition. Hot-dipped or electrogalvanized coated sheets are
covered by SAE J1562 (Section 2.12). All of the steels shown in
Tables 2.8 to 2.11 may not be commercially available in all types of
coatings. Consult your steel supplier. Also, hot rolled sheet for the
steels shown in Tables 2.8 to 2.11 may not be commercially
available in thicknesses below 1.5-2.5 mm. Again, consult your
steel supplier.
2-17

2.11.4 Surface conditions for cold reduced and metallic coated sheet
Cold reduced and metallic coated sheet steel is available in three
surface conditions:
• E
• U
• Z
Exposed. Intended for critical exposed applications where
painted surface appearance is of primary importance.
Unexposed. Intended for unexposed applications.
Semi-exposed. Intended for non-critical exposed
applications.
2.11.5 Conditions for hot rolled sheet
Four conditions of hot rolled sheet are available:
• P
• W
• N
• V
A coiled product straight off the hot mill, typically known
as hot roll black band.
A processed product in coils or cut lengths. The product
may be susceptible to aging.
A processed product in coils or cut lengths. The
mechanical properties do not deteriorate at room
temperature.
A processed product in coils or cut lengths. The
mechanical properties do not deteriorate at room
temperature. The product is free of coil breaks.
When specifying a hot rolled sheet, the desired surface condition
should also be indicated (E,U or Z as per Section 2.11.4).
2.12 SAE J1562 Zinc and zinc-alloy coated sheet steel
2.12.1 Galvanizing processes
This SAE Recommended Practice defines preferred product
characteristics for galvanized coatings applied to sheet steel. A
galvanized coating is defined as a zinc or zinc-alloy metallic
coating.
Two generic processes for metallic coated sheets are currently
used in the automotive industry:
• Hot-dip process. A coil of sheet steel is passed continuously
through a molten metal bath. Upon emergence from the bath,
the molten metal coating mass is controlled by air (or other gas)
knives or mechanical wipers before the coating solidifies. This
process produces a sheet with a coating on two sides.
• Electrodeposition process. This continuous coating process uses
cells in which the metallic coating is electrodeposited on a coil of
sheet steel. This process can produce a sheet with a coating on
either one or two sides.
2-18

2.12.2 Types of coatings
2.12.3 Coating mass
The types of commercially produced metallic coatings include:
• Hot-dip galvanized. Essentially a pure zinc coating applied by
the hot-dip galvanizing process.
• Electrogalvanized. Essentially a pure zinc coating applied by the
electrodeposition galvanizing process.
• Galvannealed. A zinc-iron alloy coating applied by the hot-dip
galvanizing process. The coating typically contains 8-12% iron
by weight.
• Alloy. Aluminum-zinc silicon alloy (55%, 43% and 2% by weight
respectively) and zinc-aluminum alloy (5% aluminum by weight)
coatings are applied by the hot-dip galvanizing process.
Zinc-iron alloy (

2.12.6 Coating designations
SAE J2329 uses a nine-character designation system to identify the
galvanizing process, the E-coating type and mass of each side of
the sheet and surface quality.
• The first and second characters denote the galvanizing process:
HD = hot-dip galvanized
EG = electrogalvanized (electrodeposition)
• The third and fourth characters denote the coating mass of the
unexposed side in accordance with Table 2.12 (page 2-30).
• The fifth character denotes the E-coating type of the unexposed
side:
G = pure zinc
A = zinc-iron
N = zinc-nickel
X = other than G, A or N
• The sixth and seventh characters denote the E-coating mass of
the exposed side in accordance with Table 2.12
• The eighth character denotes the E-coating type of the exposed
side:
G = pure zinc
A = zinc-iron
N = zinc-nickel
X = other than G, A or N
• The ninth character denotes surface quality:
E = Exposed
Z = Semi-exposed
U = Unexposed
2.13 SAE J403 Carbon steel chemical compositions
Examples of typical specification and ordering descriptions for
automotive sheet steel are given in Section 2.15.
This SAE Recommended Practice provides chemical composition
ranges for carbon steels supplied to certified chemical composition
rather than to certified mechanical properties. SAE J403 uses a
four or five character system to designate steel grade:
• The first two characters are the number “10”, which indicate that
the grade is carbon steel.
• The last two characters represent the nominal carbon content of
the grade in points of carbon. One point of carbon is 0.01%
carbon by weight. Five points would be shown as “05”, fifteen
points as “15”, etc.
• If boron is added to a carbon steel to improve hardenability, the
letter “B” is inserted between the first two characters and the last
two characters.
Examples of typical specification and ordering descriptions for
automotive sheet are given in Section 2.15.
2-20

2.13.1 Carbon sheet steel
SAE J403 provides compositions for carbon grade sheet steels.
Table 2.13 (page 2-30) shows the compositions for grades 1006
through 1025. SAE J403 provides compositions for grades 1006
through 1095. However, grades above 1025 have relatively low
formability and weldability due to their relatively high carbon
content. Thus, grades above 1025 are seldom used for automotive
sheet applications.
It is important to note that sheet steels specified or ordered to SAE
J403 are not supplied with certified mechanical properties. If
certified mechanical properties are required, automotive sheet
steel should be specified or ordered in accordance with SAE J2329
(Section 2.10) or SAE J2340 (Section 2.11).
2.13.2 Boron sheet steel
The addition of boron to carbon sheet steel improves its
hardenability. For this reason, boron sheet steel is an ideal material
for hot stampings. As an example, 10B21 (Modified) is used for
hot stamped bumper reinforcing beams. As received, this steel has
a yield strength in the range 345-515 MPa. Following hot stamping
and quenching in liquid-cooled dies, the yield strength is raised to
about 1140 MPa.
Currently, SAE’s Iron and Steel Technical Committee is revising
J403 to more appropriately cover sheet steel used for hot
stampings.
2.14 SAE J405 Wrought stainless steels
This SAE Standard provides chemical composition requirements for
wrought stainless steels supplied to chemical composition rather
than to certified mechanical properties. The standard uses three
series to designate stainless steel grades: S20000, S30000 and
S40000. S20000 designates nickel-chromium-manganese,
corrosion resistant types that are nonhardenable by thermal
treatment. S30000 designates nickel-chromium, corrosion resistant
steels, nonhardenable by thermal treatment. S40000 includes both
a hardenable, martensitic-chromium steel and nonhardenable,
ferritic-chromium steel.
Table 2.14 (page 2-30) shows the chemical compositions for two
stainless steel grades that are appropriate not only for bumper
facebars but also for bumper reinforcing beams.
2-21

2.15 SAE Specification and ordering descriptions
The following examples represent typical specification and
ordering descriptions for automotive sheet steel:
a) SAE J2329 CR2E Cold rolled sheet steel, grade 2
(Tables 2.5 & 2.7), exposed
surface condition.
b) SAE J2329 HR3MU Hot rolled sheet steel, grade 3
(Tables 2.6 & 2.7), non-aging at
room temperature and free from
coil breaks, unexposed surface
condition.
c) SAE J2329 CR4C EG60G60GE Cold rolled sheet
steel, grade 4 (Tables 2.5 & 2.7),
minimum carbon 0.015%, each
side electrogalvanized coated to
60g/m 2 , critical exposed surface
condition.
d) SAE J2329 HR2M 45A45AU Hot rolled sheet steel, grade 2
(Tables 2.6 & 2.7), non-aging at
room temperature and free from
coil breaks, each side
galvannealed coated to 45g/m 2 ,
unexposed surface condition.
e) SAE J2340 CR 180A Cold reduced sheet steel, grade
HD70G70GZ
180 non-bake hardenable dent
resistant (Table 2.8), each side
hot-dip galvanized coated to
70g/m 2 , semi-exposed surface
condition.
f) SAE J2340 CR 250B Cold reduced sheet steel, grade
EG70G70GE
250 bake hardenable dent
resistant (Table 2.8), each side
electrogalvanized coated to
70g/m 2 , critical exposed surface
condition.
g) SAE J2340 HR 340XU Hot rolled sheet steel, grade 340
high-strength low-alloy (Table
2.9), unexposed surface
condition.
h) SAE J2340 CR 1300MU Cold reduced sheet steel, grade
1300 ultra high-strength
martensitic (Table 2.11),
unexposed surface condition.
i) SAE J1562 EG70G70GE Electrogalvanized sheet having a
70 g/m 2 minimum zinc coating
(Table 2.12) on each side for an
exposed application.
2-22

j) SAE J1562 HD70G20AE Hot-dip galvanized sheet having
a 70g/m 2 minimum zinc coating
(Table 2.12) on the unexposed
side and a 20g/m 2 minimum
zinc-iron coating (Table 2.12) on
the exposed side for an exposed
application.
k) SAE J1562 HD90G90GU Hot-dip galvanized sheet having
a 90g/m 2 minimum coating
(Table 2.12) on each side for an
unexposed application.
l) SAE J1562 HD45A45AU Hot-dip galvanized sheet having
a 45g/m 2 minimum zinc-iron
coating (Table 2.12) on each side
for an unexposed application.
m) SAE J1562 EG30N30NE Electrogalvanized sheet having a
30g/m 2 minimum zinc-nickel
coating (Table 2.12) on each side
for an exposed application.
n) SAE J1562 EG70G00XE Electrogalvanized sheet having a
70g/m 2 minimum zinc coating
(Table 2.12) on the unexposed
side and no coating on the
exposed side for an exposed
application.
o) SAE J403 HR1010U Hot rolled sheet steel, grade
1010 (Table 2.13), unexposed
surface condition.
p) SAE J403 Hot rolled sheet steel, grade
HR1008HD90G90GU 1008 (Table 2.13), having a
90g/m 2 minimum coating on
each side for an unexposed
application.
2-23

2.16 ASTM A463 Aluminized sheet steel
Aluminized sheet steel is intended principally for heat resisting
applications and for uses where corrosion resistance and heat are
involved. One application is hot formed bumper beams.
Aluminized sheet has an aluminum-silicon alloy on each side
applied by a continuous hot-dip process. The coated sheet has the
surface characteristics of aluminum with the superior strength and
lower cost of steel.
One specification, which describes aluminized steel, is ASTM
A463 (Reference 2.8). The quality of the sheet steel can be
commercial (CS Types A, B and C), forming (FS), deep drawing
(DDS), extra deep drawing (EDDS), structural (SS), high-strength
low-alloy (HSLAS), high-strength low-alloy with improved
formability (HSLAS-F) and ferritic stainless steel (FSS Types 409 and
439). Chemical and mechanical properties are given for all
qualities. A463 also defines the type of aluminum-zinc coating and
coating weights.
For hot formed bumper beams (see Section 3.4), boron steel with
a Type 1 coating is commonly used. The mechanical properties of
the boron steel are discussed in Section 2.13.2. The Type 1
aluminum coating contains about 10% silicon. The coating weight
(total both sides) is typically 120-160 g/m 2 (0.4-0.5 oz/ft 2 ).
2-24

TABLE 2.5
SAE J2329 LOW-CARBON COLD ROLLED SHEET
MECHANICAL PROPERTIES
GRADE YIELD MINIMUM MINIMUM MINIMUM MINIMUM
STRENGTH TENSILE ELONGATION r m VALUE n-VALUE
(MPa) STRENGTH (%)
(MPa)
1 N/R N/R N/R N/R N/R
2 140-260 270 34 N/R 0.16
3 140-205 270 38 1.5 0.18
4 140-185 270 40 1.6 0.20
5 110-170 270 42 1.7 0.22
N/R = Not Required
TABLE 2.6
SAE J2329 LOW-CARBON HOT ROLLED SHEET
MECHANICAL PROPERTIES
GRADE YIELD MINIMUM MINIMUM MINIMUM
STRENGTH TENSILE ELONGATION n-VALUE
(MPa) STRENGTH (%)
(MPa)
1 N/R N/R N/R N/R
2 180-290 270 34 0.16
3 180-240 270 38 0.18
N/R = Not Required
2-25

TABLE 2.7
SAE J2329 LOW-CARBON HOT & COLD ROLLED SHEET
CHEMICAL COMPOSITION
GRADE MAXIMUM MAXIMUM MAXIMUM MAXIMUM MINIMUM
CARBON MANGANESE PHOSPHORUS SULPHUR ALUMINUM
(%) (%) (%) (%) (%)
1 0.13 0.60 0.035 0.035 —
2 0.10 0.50 0.035 0.030 0.020
3 0.10 0.50 0.030 0.030 0.020
4 0.08 0.40 0.025 0.025 0.020
5 0.02 0.30 0.025 0.025 0.020
TABLE 2.8
SAE J2340 DENT RESISTANT SHEET STEEL
GRADE & AS RECEIVED AS RECEIVED AS RECEIVED YIELD YIELD
TYPE YIELD TENSILE n-VALUE STRENGTH STRENGTH
STRENGTH STRENGTH AFTER AFTER
(MPa) (MPa) 2% STRAIN STRAIN & BAKE
(MPa)
(MPa)
180A 180 310 0.20 215
180B 180 300 0.19 245
210A 210 330 0.19 245
210B 210 320 0.17 275
250A 250 355 0.18 285
250B 250 345 0.16 315
280A 280 375 0.16 315
280B 280 365 0.15 345
Type A = Non-bake Hardenable
Type B = Bake Hardenable
2-26

TABLE 2.9
SAE J2340 HIGH-STRENGTH SOLUTION STRENGTHENED
AND LOW-ALLOY SHEET STEEL
GRADE &
TYPE
MINIMUM
YIELD
STRENGTH
(MPa)
MAXIMUM
YIELD
STRENGTH
(MPa)
MINIMUM
TENSILE
STRENGTH
(MPa)
COLD
REDUCED
MINIMUM
ELONGATION
(%)
HOT
ROLLED
MINIMUM
ELONGATION
(%)
300S
300
400
390
24
26
300X
300
400
370
24
28
300Y
300
400
400
21
25
340S
340
440
440
22
24
340X
340
440
410
22
25
340Y
340
440
440
20
24
380X
380
480
450
20
23
380Y
380
480
480
18
22
420X
420
520
490
18
22
420Y
420
520
520
16
19
490X
490
590
560
14
20
490Y
490
590
590
12
19
550X
550
680
620
12
18
550Y
550
680
650
12
18
Type S = Solution strengthened using C and Mn in combination with P or Si.
Type X = HSLA. Alloyed with carbide and nitride forming elements (commonly Nb, Ti and V) in combination with
C, Mn, P and Si.
Type Y = Similar to Type X, except the spread between minimum yield and tensile strengths is larger
(100 MPa versus 70 MPa).
TABLE 2.10
SAE J2340 HIGH-STRENGTH RECOVERY ANNEALED SHEET STEEL
GRADE &
TYPE
MINIMUM
YIELD
STRENGTH
(MPa)
MAXIMUM
YIELD
STRENGTH
(MPa)
MINIMUM
TENSILE
STRENGTH
(MPa)
MINIMUM
ELONGATION
(%)
490R
550R
700R
830R
490
550
700
830
590
650
800
960
Type R = Recovery annealed or stress-relief annealed.
500
560
710
860
13
10
8
2
2-27

TABLE 2.11
SAE J2340 ULTRA HIGH-STRENGTH DUAL PHASE & MARTENSITE SHEET STEEL
GRADE &
TYPE
MINIMUM
YIELD
STRENGTH
(MPa)
MINIMUM
TENSILE
STRENGTH
(MPa)
MINIMUM
ELONGATION
(%)
500 DL
300
500
22
500 DH
500
600
14
600 DL1
350
600
16
600 DL2
280
600
20
700 DH
550
700
12
800 DL
500
800
8
950 DL
550
950
8
1000 DL
700
1000
5
800 M
600
800
2
900 M
750
900
2
1000 M
750
1000
2
1100 M
900
1100
2
1200 M
950
1200
2
1300 M
1050
1300
2
1400 M
1150
1400
2
1500 M
1200
1500
2
Type DL = Dual phase with a yield-to-tensile ratio less than or equal to 0.7.
Type DH = Dual phase with a yield-to-tensile ratio greater than 0.7.
Type M = Martensitic.
2-28

TABLE 2.12
SAE J1562 COATING MASS FOR GALVANIZED SHEET STEEL
CATEGORY
(DESIGNATION)
MINIMUM MASS
PER SIDE 1
FOR HOT-DIP OR
ELECTROGALVANIZED
(g/m 2 )
MAXIMUM MASS
PER SIDE 1
FOR HOT-DIP
(g/m 2 )
MAXIMUM MASS
PER SIDE 1 FOR
ELECTROGALVANIZED
(g/m 2 )
00
00
NA 2
00
20
20
50
30
30
30
60
45
40
40
70
55
45
45
75
60
50
50
80
70
55
55
85
75
60
60
90
80
70
70
100
90
90
90
120
110
98
98
130
130
1. Single spot test. Approximate thickness in microns equals coating mass in g/m 2
multiplied by 0.14. Approximate thickness in mils = coating mass in g/m 2 multiplied
by 0.006.
2. Not applicable.
2-29

TABLE 2.13
SAE J403 CARBON STEEL COMPOSITIONS FOR SHEET
GRADE
CARBON
(%)
MANGANESE
(%)
PHOSPHOROUS
(Max %)
SULFUR
(Max %)
1006
0.08 Max
0.45 Max
0.030
0.035
1008
0.10 Max
0.50 Max
0.030
0.035
1009
0.15 Max
0.60 Max
0.030
0.035
1010
0.08-0.13
0.30-0.60
0.030
0.035
1012
0.10-0.15
0.30-0.60
0.030
0.035
1015
0.12-0.18
0.30-0.60
0.030
0.035
1016
0.12-0.18
0.60-0.90
0.030
0.035
1017
0.14-0.20
0.30-0.60
0.030
0.035
1018
0.14-0.20
0.60-0.90
0.030
0.035
1019
0.14-0.20
0.70-1.00
0.030
0.035
1020
0.17-0.23
0.30-0.60
0.030
0.035
1021
0.17-0.23
0.60-0.90
0.030
0.035
1022
0.17-0.23
0.70-1.00
0.030
0.035
1023
0.19-0.25
0.30-0.60
0.030
0.035
1025
0.22-0.28
0.30-0.60
0.030
0.035
Max = Maximum
TABLE 2.14
SAE J405 CHEMICAL COMPOSITIONS OF WROUGHT STAINLESS STEELS, %
(maximum unless a range is indicated)
DESIGNATION
C
Mn
P
S
Si
Cr
Ni
N
S20400
0.030
7.00-9.00
0.040
0.030
1.00
15.00-17.00
1.50-3.00
0.15-0.10
S30100
0.15
2.00
0.045
0.030
1.00
16.00-18.00
6.00-8.00
0.10
2-30

3. Manufacturing processes
3.1 Stamping
The art of science of sheet metal stamping processes are
challenged daily to accommodate higher strength and thinner
materials. Further, these materials must be transformed into more
complex shapes with fewer dies and increased quality in the final
part. And, of course, all must be accomplished while reducing
costs. Such pressures require a rigorous approach to assessing the
current state of a stamping process. A detailed discussion on
stamping operations is given in Reference 4.2. However, an
overview is outlined below.
3.1.1 Stretching
The concept of major and minor strain can be used to describe
different kinds of sheet forming processes. In cases where the sheet
is stretched over a punch, the major strain is always positive. For
stretching, the minor strain is usually positive as well. Different
punch and clamping configurations can create a variety of major
and minor strain levels.
For stretching, a pulling load in the major strain direction is paired
with a zero or positive load applied in the minor strain direction.
The minor strain can vary from slightly negative (no applied load in
the minor strain direction, as in stretching a strip by pulling on its
ends) to positive strain equal to the level of the major strain. A
minor strain of zero is a special case, which is often called plane
strain. In plane strain, all deformation takes place in only two
dimensions; the major strain direction and the thickness direction.
All stretching is accommodated by thinning of the material.
In circle grid analysis (CGA), small circles are etched on the surface of
the steel sheet prior to stamping (Figure 3.1). After stamping, the
deformed circles are compared to the original circles (Figure 3.2).
For the condition of plane strain, the deformed circle is an ellipse
with the minor strain diameter equal to the original diameter of the
underformed circle. A minor strain equal to the major strain is
indicated by an original circle, which remains circular after
deformation. However, the diameter of the circle after deformation
is larger than the diameter before deformation. This condition is
called equi-biaxial stretch because the amount of the stretch is
equal regardless of the direction in the plane of the sheet.
3-1

FIGURE 3.1
TYPICAL CIRCLE GRID PATTERN
FIGURE 3.2
REPRESENTATION OF STRAINS BY ETCHED CIRCLES
3-2

3.1.2 Drawing
When a sheet is pulled into a die cavity, and must contract to flow
into the cavity in areas such as at a corner or in the flange of a
circular cup, the sheet is said to be undergoing drawing. Drawing,
also known as deep drawing, generates compressive forces in the
flange area being drawn into the die cavity. Negative minor strains
are generated. In contrast to failures in stretching, failures in
drawing do not normally occur in the flange area where the
compression and flow of sheet metal is occurring. Instead, necking
and fracture occur in the wall of the stamping near the nose of the
punch. Failure occurs here because the force causing the
deformation in the flange must be transmitted from the punch
through this region. If the force required to deform the flange is too
great, it cannot be transmitted by the wall without overloading the
wall.
3.1.3 Bending
Bending differs from drawing and stretching, because the
deformation present in bending is not homogeneous through the
thickness of the material. For pure bending, where there is no
superimposed tension or compression on the bending process, the
center of the sheet has zero strain. The outer surface is elongated,
with a tensile strain equal to t/2r (t=steel thickness, r=bend radius to
the midpoint of the steel thickness). The inner surface is
compressed, with a compressive strain equal to t/2r. The strain
varies from compressive at the inner radius, through zero at the
midpoint of the thickness, to tensile at the outside radius. In pure
bending, the compressive and tensile strains are equal.
Because the strain varies through the thickness, forming limit
analysis (Section 3.1.5) does not directly apply. Materials with very
little capacity to be formed can frequently undergo bending
operations successfully. The tendency to thin locally, with necking
and fracture, is not present in bending. Cold working of the
material does take place. However, the amount of work hardening
depends on the radius of the bend and the thickness of the material.
A sharper radius (smaller r) or thicker material (greater t) causes an
increase in strain at the surface. Bending is a plane strain
operation. The length of the bend does not change during bending,
except for localized distortion at the edge of the sheet.
3.1.4 Bending and straightening
As material passes through a draw bead or over a die lip, it is bent,
straightened, and sometimes re-bent in the opposite direction. The
net strain at the end of this process is small, although cold work has
occurred and the material is harder than it was before the process
began. As a result, the ability to deform the material in subsequent
operations is decreased.
3-3

3.1.5 Forming limits
The measurement of strain provides an important tool for
determining the local deformation that occurs in a complicated
process. Sharply changing levels of strain usually indicate a
localization of deformation and a higher likelihood of necking and
failure during forming. For sheet metal, it has been found that a
limit to the major strain exists for each level of minor strain. This
phenomenon has been studied in the laboratory and has resulted in
the creation of forming limit diagrams.
First, flat sheets of a given material are etched with circles as shown
in Figure 3.1. The flat sheets are then deformed in a variety of
configurations to develop a large range of major and minor strains.
If the forming process for any given configuration is continued until
failure (as defined by localized necking), the major and minor
strains at failure, as shown in Figure 3.2, can be measured for that
configuration.
By plotting the failure strains of the various configurations, a
boundary line indicating the major strain limit for each minor strain
is obtained (Figure 3.3). While this limit is not absolute, there is a
very high probability of failure above this boundary line and a low
probability of failure below this line. The boundary line is
frequently called the forming limit curve, and the entire graph, the
forming line diagram (FLD). A second forming limit curve, plotted
with major strains 10% below those of the boundary line, is
sometimes used to provide a safety factor. Each combination of
material properties and thickness results in a different FLD.
3.2 Roll forming
Cold roll forming is a process whereby a sheet or strip of metal is
formed into a uniform cross section by feeding the stock
longitudinally through a roll forming mill. The mill consists of a
train with pairs of driven roller dies, which progressively form the flat
strip until the finished shape is produced.
The number of pairs of rolls depends on the type of material being
formed, the complexity of the shape being produced, and the
design of the particular mill being used. A conventional roll
forming mill may have as many as 30 pairs of roller dies mounted
on individually driven horizontal shafts.
Roll forming is one of the few sheet metal forming processes that is
confined to a single primary mode of deformation. Unlike most
forming operations that have various combinations of stretching,
drawing, bending, bending and straightening, and other forming
modes, the roll forming process is nothing more than a carefully
designed series of bends. In roll forming, metal thickness is not
changed except for a slight thinning at the bend radii.
3-4

3-5
FIGURE 3.3
TYPICAL FORMING LIMIT DIAGRAM

The roll forming process is particularly suited to the production of
long lengths of complex shapes held to close tolerances. Large
quantities of these parts can be formed with a minimum of handling
and manpower. The process can be continuous by coil feeding and
exit cutting to length. Operations such as notching, slotting,
punching, embossing and curving can easily be combined with contour
roll forming to produce finished parts off the exit end of the roll
forming mill. In fact, ultra high-strength steel reinforcing beams,
with sweeps up to 50, only need to have the mounting brackets
welded to them before shipment to the assembly line.
3.3 Hydroforming
There are two types of hydroforming - sheet and tubular. Sheet
hydroforming is typically a process where only a female die is
constructed and a bladder membrane performs as the punch. High
pressure fluid (usually water) forces the bladder against the steel
sheet until it takes the shape of the female die. Sheet hydroforming
has several advantages versus stamping such as lower tooling costs
and less friction during forming. However, it is limited to lower volume
applications due to its higher cycle time.
In tubular hydroforming, a straight or pre-bent tube is laid into a
lower die. The upper and lower dies are then clamped together.
Next, conical nozzles are inserted and clamped into each end of
the tube. Finally, a fluid (usually water) is forced at a high pressure
into the tube until it takes the shape of the die. While tube
hydroforming technology has been around for decades, the mass
production of automotive parts only became cost effective in
about 1984.
The benefits of hydroforming are usually found via part
consolidation and the elimination of engineered scrap. Box
sections, consisting of two hat sections welded together, lend
themselves to cost-effective replacement by a single hydroformed
part. Punches, mounted in the forming dies, are used to pierce
holes during forming, eliminating subsequent machine operations.
The structural integrity of a hydroformed part, made from a single
continuous tube, is superior to that of a part made from two or
more components. Weight savings of 10 to 20% can be achieved
via both reducing gauge and eliminating weld flanges. If flanges
are necessary for attachment, they can be created by pinching the
tube during the hydroforming process.
High volume tubular hydroformed parts are currently incorporated
into automotive components such as subframes, ladder frames,
IP beams, roof rails, and exhaust components.
3-6

3.4 Hot forming
Generally speaking, as the strength of steel increases, its ductility
decreases. One method used to overcome the reduced formability
of ultra high-strength steel is hot forming. Hot formed bumper
beams have very high-strength. They offer not only mass reduction
but also large and compound sweeps. Highly complex beams can
be produced in one piece. The repeatability of dimensions is very
good and there is no springback, a phenomenon which is common
with cold forming processes.
The hot forming process involves the following steps:
• Blanking
• Heating
• Forming/Quenching
• De-scaling (if required)
The typical material used for hot stamping is boron steel having
0.22% carbon, 0.002% boron, an as-delivered yield strength of
330 MPa (47.9 ksi), an as-delivered tensile strength of 500 MPa
(72.5 ksi) and a 15-20% elongation. The boron steel may be bare
or aluminized. If aluminized, a hot dip Type 1 coating (10% silicon)
and a coating mass of 120-160 g/m2 (0.7-1.0 mils) are common.
After heating and quenching, a hot formed part has very high
hardness (470 HV). Thus, it is best to punch any required holes
into the blank.
The developed blanks or pre-formed parts are continuously fed
into a furnace. They are heated to austenitizing temperatures,
approximately 900ºC (1650ºF). If bare steel is used, the furnace
usually has a non-oxidizing atmosphere to suppress scale
formation. However, on transfer to the forming/quenching press,
some scale will form. If aluminized steel is used, a Fe-Al alloy forms
in the furnace on the surface of the steel sheet and scaling is
avoided.
In the forming/quenching press, the blank/pre-formed section is
formed to its final shape using dies maintained at room
temperature. The part is held in the die until it is sufficiently
quenched. Some tempering is usually required. Tempering may be
accomplished by ejecting the part from the forming/quenching
dies while it is still fairly hot or by baking the quenched part in an
oven. The yield strength of the final hot formed part for a common
10B21 boron steel has increased to about 1140 MPa (165 ksi) and
the tensile strength to about 1520 MPa (220 ksi). Elongation has
decreased to less than 6%.
A part made from aluminized sheet has a hard Fe-Al-Si coating
system and is scale free, eliminating the need for de-scaling.
Further, this coating system provides corrosion protection for the
finished part. A part made from bare sheet does have scale and
de-scaling is often employed.
3-7

3.5 Bumper beam coatings
Steel bumper beams are coated for one or more of the following
reasons:
• To improve appearance
• To slow or prevent corrosion
• To increase resistance to wear
The frontside of a facebar is an exposed automotive part and
appearance is critical. However, in addition to appearance, the
coatings applied to facebars made from hot or cold rolled sheet
must also provide adequate corrosion protection and resistance to
rock chipping. Zinc coated sheet is not commonly used for
facebars. One exception, though, is when the thickness of a
facebar is less than 1.00 mm (0.039 inches). In such cases, the zinc
provides the extra corrosion protection and rock-chip resistance
needed to meet design requirements. Successful trials have been
conducted on facebars made from stainless steel. An inherent
advantage of such facebars is their corrosion resistance. Thus,
stainless steel facebars need only be coated to meet appearance
and rock-chip requirements.
3.5.1 Zinc or zinc-iron coatings
3.5.2 Aluminum coating
A reinforcing beam is an unexposed part and the main reason for
coating it is to improve corrosion resistance. Sometimes, however,
reinforcing beams are given a coating to provide not only
corrosion resistance but also appropriate underbody appearance.
Steel reinforcing beams are made from hot rolled, cold rolled or
zinc coated sheet.
Bumper beam coatings may be applied by a steel mill, an
automotive supplier or an OEM. Steel mills supply sheet with
metallic coatings (e.g., zinc, zinc-iron) that have been applied by
hot dipping or electrocoating. Automotive suppliers apply metallic
(e.g., chromium), organic (e.g., E-coat, paint), autodeposition and
powder coatings. The OEMs often apply E-coat on their assembly
lines.
The coatings applied to current bumper beams are shown in
Tables 5.4, 5.5 and 5.6. It may be seen that facebars are typically
coated with chromium or paint, while reinforcing beams typically
receive E-coat.
These coatings are described in Section 2.12.
This coating is described in Section 3.4.
3-8

3.5.3 Polishing
In order to achieve a high quality surface after painting or
chromium coating, the steel blanks used to stamp facebars must
be smooth and free of surface defects. Traditionally, hot rolled
sheet has been used for facebars and the following steps taken for
the blanks:
• Ordering to special surface and flatness requirements
• Pickling
• Polishing
• Phosphating and lubricating
3.5.4 Chromium coating
Chromium coatings are applied using the electroplating process,
which places a thin layer of metal on an object through the use of
electricity. Although there are variations, the following steps are
typically used to place a chromium coating on a fabricated facebar:
• Polishing manually or automatically to remove die marks, orange
peel and shock lines introduced during the stamping process.
• Cleaning to remove lubricants, polishing compounds and shop soils.
• Pickling to remove oxides, rust, scale and weld smoke.
• Rinse.
• Semi-bright nickel electroplating.
• Rinse.
• Bright nickel electroplating.
• Rinse.
• Decorative chromium electroplating.
• Rinse.
In the electroplating steps described above, the metal coating is
deposited onto the facebar by applying an electrical potential
between the facebar (cathode) and a suitable anode in the
presence of an electrolyte. The electrolyte usually consists of a
water solution containing a salt of the metal to be deposited and
various other additions that contribute to the electroplating
process. When the metallic salt dissolves in the water, the metal
atoms are freed to move about. The atoms lose one or more
electrons and become positively charged ions. The metallic ions
are attracted to the negatively charged facebar. They coat the
facebar and regain their lost electrons to become metal once again.
Typical coating thickness applied to the significant (visible)
surfaces of steel facebars is:
Total nickel 30 micrometers (1.2 mils) min.
Semi-bright nickel
Bright nickel
Chromium
40-60% of total nickel
40-60% of total nickel
0.25 micrometers (0.01 mils) min.
0.40 micrometers (0.016 mils) max.
3-9

3.5.5 Conversion coating
During electroplating, the process is tightly controlled to place the
required thickness of nickel and chromium on the surfaces with
high visibility. The frontside of a facebar must have excellent
appearance and corrosion resistance. Often, a corrosion
resistance of 44 hours using the CASS test outlined in ASTM B368
is specified. To avoid unnecessary cost, the electroplating process
is designed to place an absolute minimum of nickel and chromium
on the hidden surfaces.
Phosphate conversion coatings are employed to enhance paint
adhesion. By enhancing paint adhesion, they indirectly enhance
corrosion resistance. There are several varieties of phosphate
coatings (e.g., iron, zinc or manganese).
Prior to the application of a conversion coating, the metal surface
must be free of shop soils, oil, grease, lubricants and rust. The
metal surface must be receptive to the formation of a uniform,
adherent chemical film or coating. Surfaces may be cleaned by
mechanical methods or, more commonly, by immersion or spray
cleaner systems.
A phosphate coating is applied by immersing a clean metal part in
a hot processing solution for 4-6 minutes, depending on bath
chemistry. The weight (thickness) of the conversion coating is
dependent on the manner in which the part is cleaned, the
immersion time, the composition of the processing bath and the
composition of the metal itself.
3.5.6 Electrocoating (E-coating)
E-coat is an organic coating applied by the electrocoating method.
Electrocoating has the ability to coat all areas of complex parts
including recessed areas and edges. E-coat is a durable, lasting
coating. It is used as a primer, top coat or both.
Parts are usually E-coated via a conveyor system in one continuous
process. Although there are variations, the usual steps in applying
E-coat to a steel part are: alkaline cleaner, water rinse, surface
conditioner, zinc phosphate coating (see Section 3.5.4), rinse, seal
coating, de-ionized water rinse, E-coat application, permeate rinse,
final de-ionized water rinse, and curing oven.
E-coating systems are known as anodic or cathodic depending on
whether the part is the anode or the cathode in the electrochemical
process. Cathodic systems are common since they require less
surface preparation and they provide better corrosion resistance.
The E-coat process requires a coating tank or bath in which to
immerse the part. The bath, containing water and paint, is given a
positive charge (cathodic system). The part, with a negative
charge, when immersed in the bath, attracts the positively charged
paint particles. The paint particles coalesce as a coating (E-coat)
on the part surface. E-coat thickness typically applied to bumper
beams ranges from 20 to 25 micrometers (0.8 to 1.0 mils).
3-10

3.5.7 Paint coating
Paint is a cost effective corrosion protection method. It acts as a
barrier to a corrosive solution or electrolyte and it prevents, or
retards, the transfer of electrochemical charge from a corrosive
solution to the metal beneath the paint.
Paint is a complex mixture of materials designed to protect the
substrate and to enhance appearance. It is composed of binders,
carriers, pigments and additives. Binders provide the major
properties to the paint while the carriers (solvents and/or water)
adjust the viscosity of the paint for the application. Pigments
impart specific properties such as corrosion resistance and color.
The type of pigment and its volume are critical to the optimization
of properties such as adhesion, permeability, resistance to
blistering and gloss. Additives include thickeners, flow agents,
catalysts and inhibitors.
Paints are often identified by the type of polymers employed.
Commonly used paint coatings include:
• Alkyd and epoxy ester (air dried or baked)
• Two-part coatings such as urethane
• Latex coatings such as vinyl, acrylic or styrene polymer
combinations
• Water soluble coatings (versions of alkyd, epoxy ester or polyester)
Baked enamel basecoat/rigid clearcoat systems are commonly
applied to the frontside of facebars. The process steps include:
• Conversion coating (see Section 3.5.3)
• E-coating (see Section 3.5.4)
• Enamel basecoating
• Enamel clearcoating
• Baking.
3.5.8 Autodeposition coating
Autodeposition is a waterborne process that depends on chemical
reactions to achieve deposition. The composition of an
autodeposition bath includes a mildly acidic latex emulsion
polymer, de-ionized water and proprietary ingredients. The
chemical phenomenon consists of the mildly acidic bath attacking
the steel parts being immersed and causing an immediate surface
reaction that releases iron ions. These ions react with the latex in
solution causing a deposition on the surface of the steel parts. The
newly deposited organic film is adherent yet quite porous. Thus,
the chemical activators can rapidly diffuse to reach the surface of
the metal, allowing continued coating formation.
The coating thickness is time and temperature related. Initially, the
process is quite rapid, but slows down as the film begins to build.
As long as the parts being coated are in the bath, the process will
continue. Typically, film thickness is from 15 to 25 micrometers
(0.6 to 0.8 mils).
Autodeposition will coat any metal the liquid touches. Thus, an
advantage of this coating is its ability to coat the inside of tubing
and deep cavities. Autodeposition does not require a conversion
coating and the coating cures at a relatively low temperature.
3-11

3.5.9 Powder coating
In the powder coating process, a dry powder is applied to a clean
object. After application, the coated object is heated, fusing the
powder into a smooth continuous film. Powders are available in a
wide range of chemical types, coating properties and colors. The
most widely used types include acrylic, vinyl, epoxy, nylon,
polyester and urethane. Modern application techniques for
applying powders fall into four basic categories: fluidized bed
process, electrostatic bed process, electrostatic spray process and
plasma spray process.
The electrostatic spray process is the most commonly used
method for applying powders. In this process, the electrically
conductive and grounded object is sprayed with charged,
non-conducting powder particles. The charged particles are
attracted to the substrate and cling to it. Oven heat then fuses the
particles into a smooth continuous film. Coating thicknesses in the
range of 25 to 125 micrometers (1 to 5 mils) are obtained.
3-12

4. Manufacturing considerations
4.1 Forming considerations
High-strength and ultra high-strength steels have less ductility, and
hence less formability, than lower strength steels. Thus, care must
be taken in part design and forming method selection. In addition,
springback increases with yield strength and it must be accounted
for in the process design. Sections 4.1.1 through 4.1.5 provide
“Guidelines” and “Rules of Thumb” for the roll forming and stamping
processes. The Guidelines and Rules of Thumb are based on practical
experience. Their use will help alleviate formability and springback
issues associated with the roll forming and stamping of high-strength
and ultra high-strength steels.
4.1.1 Guidelines for roll forming high-strength steel
All of the high-strength steels in Table 2.2 can be roll formed,
pre-pierced and swept after roll forming.
The following Guidelines apply (Reference 4.3):
Do:
• Select the appropriate number of roll stands for the material
being formed. Remember that the higher the steel strength,
the greater the number of stands required on the roll former.
• Use the minimum allowable bend radius for the material in
order to minimize springback.
• Position holes away from the bend radius to help achieve
desired tolerances.
• Establish mechanical and dimensional tolerances for
successful part production.
• Use appropriate lubrication.
• Use a suitable maintenance schedule for the roll
forming line.
• Anticipate end flare (a form of springback). End flare is
caused by stresses that build up during the roll forming
process.
• Recognize that as a part is being swept (or reformed after
roll forming), the compression of metal can cause sidewall
buckling, which leads to fit-up problems.
Don’t:
• Do not roll form with worn tooling, as the use of worn tools
increases the severity of buckling.
• Do not expect steels of similar yield strength from
different steel sources to behave similarly.
• Do not over-specify tolerances.
4-1

4.1.2 Guidelines for roll forming ultra high-strength steel.
All of the ultra high-strength steels in Table 2.3 can be roll formed,
pre-pierced and swept after roll forming.
The following Guidelines apply (Reference 6.1):
1. The minimum bend radius should be two times the
thickness of the steel to avoid fracture.
2. Springback magnitude can range from ten degrees for
120X steel to 30 degrees for M220HT steel, as compared
to one to three degrees for mild steel. Springback
should be accounted for when designing the roll
forming process.
3. Due to the higher spingback, it is difficult to achieve
reasonable tolerances on sections with large radii (radii
greater than 20 times the thickness of the steel).
4. Rolls should be designed with a constant radius and an
evenly distributed overbend from pass to pass.
5. About 50% more passes (compared to mild steel) are
required when roll forming ultra high-strength steel.
The number of passes required is affected by the
mechanical properties of the steel, section depth-to-steel
thickness ratio, tolerance requirements, pre-punched
holes and notches.
6. Due to the higher number of passes and higher material
strength, the horsepower requirement for forming is
increased.
7. Due to the higher material strength, the forming
pressure is also higher. Larger shaft diameters should
be considered. Thin, slender rolls should be avoided.
8. During roll forming, avoid undue permanent elongation
of portions of the cross section that will be compressed
during the sweeping process.
4.1.3 General guidelines for stamping high-strength and ultra high-strength steels.
All of the high-strength streels in Table 2.1 may be stamped into
bumper beams. Additionally, some ultra high-strength steels in Table
2.2, such as 120X, 590T, 780T and 140T, may be stamped, bend
stretched, drawn and flanged.
The following guidelines apply (Reference 6.2):
PRODUCT DESIGN
• Avoid designing parts that require a draw forming operation
(i.e., metal must flow or stretch off the binder).
• Maintain gentle shape changes and constant cross sections
wherever possible in part design. These factors become
more important as material strength is increased.
4-2

• Keep the depth of the part to a minimum when the part
has excessive sweeps in the plan view or elevation.
• Avoid designing parts with closed corners that require
draw die operations.
• Keep the flanges as short as possible when there is a
deep-formed offset flange.
DIE PROCESS
• Try to form the parts completely to the depth desired in
the first forming operation.
• Minimize stretch and compression of metal to reduce
residual strains that cause springback and twist in the part.
• Use high pressure on the draw binder and balancing blocks.
They allow the sheet metal to flow without wrinkling.
• Keep the side walls perpendicular (90 degrees to the base
of the die).
• Avoid open-angle forming. Overbend the flanges 6 to 10
degrees.
• On straight channel-shaped parts, consider a solid form die.
• Pre-forming the sheet steel is a method commonly used to
accumulate enough material to ensure that adequate
metal is available for forming without splitting or
excessive thinning.
DIE DESIGN
• Maintain die forming radii as sharp as possible. Try to
fold the metal rather then stretch it over a radius. Folding
reduces curl of the sidewalls and springback of the weld
flanges.
• Maintain an even draw depth and length of line.
• Design robust dies to minimize flexing of the die
components.
DIE CONSTRUCTION / TRYOUT
• Sidewalls should be as tight as possible to lessen
springback.
• To reduce shock and press tonnage requirements, a
minimum shear of four to six times metal thicknesses
is required for cutting dies. This minimum shear also
reduces noise on break through.
• Trim and pierce dies should have 7% to 10% die clearance.
4-3

FIGURE 4.1 a)
RULES OF THUMB - SPRINGBACK
2
The techniques shown in Figures 4.1 a) through 4.1 c) can help
compensate for springback when forming a 90-degree bend if
a sharp radius or a tight flange (see Figure 4.3) is not adequate.
Refer to Figure 4.1a)
1) Restrike the flange at an overbend angle between
3 and 7 degrees, depending on the material strength and/or
thickness.
2) Set up part in die to allow for overbend.
3) Undercut the lower die steel and let the metal overbend.
4) Pre-form the top part surface prior to flanging
and flatten the part using the die pad.
4-4

FIGURE 4.1 b)
RULES OF THUMB - SPRINGBACK
Refer to Figure 4.1b)
5) The addition of stiffening darts helps maintain a 90-degree flange.
6) Coining a flange radius as the die bottoms will help maintain
form and helps prevent springback.
7) An extension of the upper flange steel allows for extra pressure
to be applied on the formed radius. This is a difficult process to
control, but it could help in special conditions, particularly on
heavier gauge steels.
4-5

FIGURE 4.1 c)
RULES OF THUMB - SPRINGBACK
Refer to Figure 4.1c)
8) Providing a vertical step in the flange stiffens and straightens the
flange, stopping sidewall curl as well as springback.
9) Rotary benders are used by many manufacturers
to control springback, as the metal is rolled
around the radius instead of flanging. Positive comments on this
method promote its ability to overbend the flange.
10) Place a 90 durometer urethane behind flanging steels in a free
state (not compressed). Clearance holes through the flanging
steels allow the screws to hold the urethane in place. Please
note the urethane must stay 0.25 inches (6.4 mm) off the bottom
of the pocket. This space leaves room for the urethane deflection.
Tighten clearance until desired effect is achieved.
11) By adding a horizontal step along the flange, the flange is stiffened,
resulting in reduced springback.
4-6

FIGURE 4.2
RULES OF THUMB - DIE FLANGE STEELS
Refer to Figure 4.2
1) Flange steel clearance should be 90% of metal thickness, but
no greater than metal thickness. Maintaining a tight condition
helps to prevent springback.
2) Because of the tight clearance, the die steels should be as hard
as possible. Therefore, it is recommended that air-hardened
tool steel or harder material be used, and a surface coating be
applied to increase hardness and improve lubricity.
3) Air-hardened tool steel (D2) is recommended for flange steel
(Rockwell 58 - 62 on the C-scale). However, other materials may
be used as long as they have a surface coating applied which
resists scoring.
4) All flanging radii should be as sharp as possible without fracturing
the sheet metal during forming. The flange radii should be something
less than metal thickness. Start by just breaking the sharp
corner and work from there until you can make the flange without
splitting the sheet metal.
4-7

FIGURE 4.3
RULES OF THUMB - HAT SECTION
Refer to Figure 4.3
1) Maintain a constant depth on hat sections, if at all possible.
2) The size of the radius is to be kept as small as possible, normally
less than metal thickness.
3) Form 90-degree side walls on the hat section whenever possible.
4) If the sidewall is not 90 degrees, try to balance the forming with
the same angle on the opposite side of the hat section.
5) Unequal residual strain and/or compression on opposite sidewalls
has a tendency to twist the entire rail.
4-8

FIGURE 4.4
RULES OF THUMB - RADIUS SETTING
When forming a hat section, the action of the die can aid the
retention of shape by setting the corner radii.
Refer to Figure 4.4
1) As the flange steels make contact with the sheet metal blank, an
initial crown is formed.
2) The flange steels then enter over the die-post radii and force the
metal to conform to the lower die. The crown remains in the
part. It is best if both sides enter simultaneously.
3) The die is now very close to its home position. The crown
remains and the lower flanges are starting to form.
4) As the die is closed, the lower flanges are formed with corner
radii as sharp as possible. The top corners are forced outward
as the crown is hit home by the upper die. If the part retains a
crown, then a negative crown can be incorporated to minimize
springback.
4-9

FIGURE 4.5 a)
RULES OF THUMB - COMBINATION FORM & FLANGE DIE
Using a combination form-and-flange die is basic to meeting
high-strength steel requirements. A general idea of how this die
works follows.
The die initially forms the contour in the developed blank using the
upper pressure pad. The metal is then locked, using the lock beads
to prevent feeding the metal in from the ends. The metal is allowed
to flow in freely from the sides without restrictions within the ring,
just a metal thickness apart to stop wrinkling.
The flange steels are maintained as sharp as possible, and the side
walls are tight. This procedure controls the springback and sidewall
curl in order to produce a quality part. If the part is straight, see
Figure 4.4 for more information.
The four-piece form and flange die shown above incorporates
features that lend themselves to the production of hat section
parts. Remember that in order for this type of die to work, the
finished part must be off the ring when the part is completely
formed in order to avoid upstroke deformation. The unique
features of this die are as follows:
Refer to Figure 4.5a)
1) The upper pressure pad gives the sheet metal blank its initial
contour and holds the blank in location.
2) The lower ring (known also as a lower pressure pad) controls
the flow of the metal and prevents wrinkling as the part is being
formed (See 5 and 6 on Figure 4.5 b).
4-10

FIGURE 4.5 b)
RULES OF THUMB - COMBINATION FORM & FLANGE DIE
AIR PINS
Refer to Figure 4.5a) and Figure 4.5b)
3) Flange steels should be kept tight to the lower post to help
prevent sidewall curl.
4) A smaller-than-metal thickness radius on the lower post helps
prevent springback.
5) Restraining beads are used to restrain the flow in at the ends of
the rail. The metal must flow off the ring and on to the die post to
prevent the panel from being deformed by the upstroke of the die.
6) Metal thickness clearance between the upper and lower ring
under high pressure is needed to allow the metal to flow in from
the sides without buckling.
7) Balancing blocks (leveling blocks, kiss blocks or spacer blocks)
are used to control the clearance between the upper form steels
and the lower ring surfaces in order to adjust for metal flow.
8) If the rail is open-ended, there is no need to restrict metal flow
unless stretch is required to help prevent twist.
4-11

FIGURE 4.6
RULES OF THUMB - FORMING BEADS
Refer to Figure 4.6
1) Half-round draw beads are used to control metal flow. They
restrict the flow and force the metal to stretch or control feed as
required to produce the draw shape of the part.
2) Lock beads are generally used to stop the metal from moving.
This condition is pure stretch. In general, it is recommended that
this type of bead be avoided in dies used to form high-strength
steel material.
3) Start lock bead configurations with radii small enough to shear
the sheet metal blank. Then uniformly dress the radii to eliminate
cutting, but still locking the metal flow. When the beads need
reworking, repeat this procedure.
4-12

FIGURE 4.7
RULES OF THUMB - FORMING AN EMBOSS
When forming an emboss or surface formation into a relatively flat
high-strength steel part, the break lines need to be sharp and crisp.
You must coin these lines into the part to set them and reduce any
springback or distortion. Sidewalls of the embossment must be
45 degrees or less from the surface.
Refer to Figure 4.7
1) This formation is totally within the part’s perimeter and does not
extend to the trim.
2) This example shows the formation open to the part’s trim edge.
This formation causes excess or loose metal along the edge.
Therefore, it is recommended that a short flange and/or small
bead be added to stiffen and eliminate this condition.
4-13

FIGURE 4.8
RULES OF THUMB - EDGE SPLITTING
It is important that the trim quality be maintained to prevent edgesplitting
from work hardening.
Refer to Figure 4.8
1) When forming an outside corner, the trim edge has a tendency
to wrinkle. In order to minimize this wrinkling condition, it is
recommended that the flange in the area of the wrinkle be as
short as possible.
2) Inside corners have a tendency to split. Therefore, try to make
the trim line as long as possible by scalloping the edge.
A combination of shortening the flange and lengthening the
trim line should help stop the splitting.
If not, a formation change has to be made to add material to the
split area.
4-14

FIGURE 4.9
RULES OF THUMB - PART DESIGN
Refer to Figure 4.9
1) The following are general characteristics of high-strength steel
(HSS) that should be taken into consideration during the part
design phase:
• HSS will stretch, generally in the range of 2% to 6%.
• HSS will resist compression due to the hardness of the material.
These characteristics of HSS generally require that parts be designed
for form and flange die processes rather than draw dies.
2) In some cases, it is necessary to compensate for these material
characteristics by designing in darts and/or notches to equalize
the length of line and to help maintain part dimensional integrity.
3) The above diagram shows how these darts and notches could be
applied to an HSS part.
4-15

FIGURE 4.10
RULES OF THUMB - DIE CONSTRUCTION
Refer to Figure 4.10
1) Due to the forces exerted during the forming process of
high-strength steel, dies must be built with extra strength.
Extra strength is necessary to prevent die flexing. The following
are ways to compensate for the unwanted flexing in the die:
• Block in or heel cam drivers.
• Use heavy-duty guide pins and bushings.
• Key in the sections and use large fasteners.
• Provide for positive returns.
• Provide heavy-duty die shoes with appropriate reinforcement.
2) Provide for die adjustability during construction. It is important
to provide these adjustments because it is undesirable to
machine the hardened and coated die details.
3) It is of prime importance to balance the forces exerted on the
die during forming. When practical, form two parts at a time, or
produce the right and left hand part in the same die.
4-16

FIGURE 4.11
RULES OF THUMB - DEVELOPED BLANKS
Refer to Figure 4.11
1) When using high-strength steel material for BIW (Body-In-White)
structural parts, testing has demonstrated that the recommended
type of forming is with a flange or form die. This type of die utilizes
a developed blank.
2) This blank should be as close to finish trim as possible. Only in
areas where the trim is critical should a finish trim operation be
added.
4-17

FIGURE 4.12
RULES OF THUMB - TRIMMING
Refer to Figure 4.12
1) Because high-strength steel (HSS) is more brittle and harder than
mild steel, and because it is not as ductile as a result of the
strengthening mechanisms in the metallurgy, it is more difficult to
trim. HSS requires approximately the same die clearance between
the upper and lower trim steels as mild sheet steel. This clearance
is approximately 7% to 10% of metal thickness per side. The range
of the hardness and the thickness determines the exact amount.
2) Dies must be sharpened more frequently when trimming HSS.
They also require rigidity to prevent the die from flexing, which
can cause dulling of the trim steels.
3) It is recommended that extremely hard cutting edges be provided
on trim steels. Therefore, use of S-7 or other shock-resistant steel
with a minimum of 58-62 Rockwell (C-scale) is recommended.
4-18

FIGURE 4.13
RULES OF THUMB - DIE SHEAR
Refer to Figure 4.13
1) Due to excessive shock during blanking or trimming of highstrength
steel, a full four times (4x) metal thickness shear is
recommended to protect both press and die.
In order to prolong the die life of either a blank or trim die, die
shear must be added.
Advantages of the die shear
1) Lessens tonnage requirements.
2) Saves the press; reduces shock on the press.
3) Lengthens the die life between tune-ups and sharpening.
4-19

4.1.4 Guidelines for hat sections stamped from high-strength or ultra high-strength steels.
Basic guidelines for designing and processing hat section parts of
high-strength or ultra high-strength steel are (Reference 6.3):
Do:
• Form channels as close to finished shape as possible.
• Avoid closed ends on channels.
• Utilize small die radii.
• A combination of low pad pressure and tight clearance
minimizes curl and springback.
• Allow for extra development time.
Don’t:
• Assume high-strength and ultra high-strength steel will
behave like mild steel.
• Depend on traditional die design criteria.
4.1.5 Rules of Thumb for high-strength steel stampings.
Common concerns associated with the use of high-strength steel in
a stamping operation include springback, splitting, tolerances, die
design, die life and blank design. The automotive industry routinely
produces stamped high-strength steel parts. Over the past several
years, many lessons have been learned through extensive practical
experience. These lessons have been summarized in the form of
Rules of Thumb in Figures 4.1 through 4.14 (Reference 6.2). The
application of the Rules of Thumb will alleviate issues associated with
high-strength steel at the part design and die design stages. They will
shorten die development time and help ensure production success
in the stamping of high-strength steel parts.
4.2 Welding considerations
High-strength and ultra high-strength steels are routinely welded on a
production basis. Most assemblies can be welded with conventional
equipment using weld cycles similar to conventional ones. In most
applications, high-strength or ultra high-strength steel is welded to
mild steel using gas metal arc or high-frequency welding. When
welding ultra high-strength steels, specific weld windows should be
developed. With nominal modification to standard weld procedures,
weight reduction may be achieved with high-strength and ultra highstrength
bumper beam assemblies.
4-20

4.2.1 Steel chemistry
4.2.2 High-strength and ultra high-strength steels.
4.2.3 Welding processes
Welding procedures must suit the chemistry of the steel grade being
welded. Steel specifications traditionally set limits on the main elements
in a steel grade (e.g., carbon, manganese). However, most steel
grades contain additional elements that have not been specified.
Thus, when selecting suitable welding procedures, it is important to
identify the levels of any unspecified elements in a bumper steel
grade. Recommended Practice, SAE J2340 (Reference 6.4), recognizes
this fact and places limits on unspecified elements. The high-strength
and ultra high-strength steels covered by SAE J2340 are shown in
Table 4.1. The unspecified elements permitted in the SAE J2340
grades are shown in Table 4.2.
When welding high-strength and ultra high-strength steels, it is
important to consider several factors usually not considered when
welding low-strength steels (e.g., welding process, welding parameters
and material combinations). Integration of these considerations can
result in a successful welding system. For instance, a low heat input
resistance seam welding method has been successfully employed for
commercial production of bumper beams made from M190HT steel.
Various welding methods (arc welding, resistance welding, laser
welding and high-frequency welding) all have unique advantages
for the welding of specific sheet steel combinations. Factors such
as production rate, heat input, weld metal dilution and weld location
access may make one welding system more desirable than another
system. For instance, a high-strength steel that is problematic for
spot welding may not exhibit the same difficulty in arc or highfrequency
welding.
It is important to consider material combinations when employing
welding processes that solidify from a molten pool, or that are
constrained by thickness ratio. In general, caution should be
exercised when spot welding a high-strength or ultra high-strength
steel to itself because of possible weld metal interfacial fracture
tendencies. However, even a problematic higher strength steel can
be spot welded to a mild steel.
On behalf of the Bumper Project of the American Iron and Steel
Institute, David Dickinson, The Ohio State University, conducted a
survey on bumper component welding (Reference 4.5). The survey
identified the welding processes that are currently used in bumper
manufacturing, or were used to produce prototype bumpers. The
processes are:
1. Gas metal arc welding (GMAW)
2. Flux cored arc welding (FCAW)
3. Resistance spot welding (RSW)
4. Resistance projection welding (RPW)
5. Resistance seam welding (RSeW)
6. Resistance projection seam welding (RPSeW)
7. High frequency and induction resistance seam welding
(RSeW-HF&I)
8. Upset welding (UW)
9. Friction welding (FRW)
10. Laser beam welding (LBW)
11. Laser beam and plasma arc welding (LBW/PAW)
A brief description of each welding process is given in Sections
4.2.3.1. to 4.2.3.11.
4-21

TABLE 4.1
SAE J2340 STEELS AND STRENGTH GRADES
Steel Description Grade Type Available Strength Grade - MPa
Dent Resistant Non Bake Hardenable A 180, 210, 250, 280
Dent Resistant Bake Hardenable B 180, 210, 250, 280
High-Strength Solution Strengthened S 300, 340
High-Strength low-alloy X & Y 300, 340, 380, 420, 490, 550
High-Strength Recovery Annealed R 490, 550, 700, 830
Ultra High-Strength Dual Phase DH & DL 500, 600, 700, 800, 950, 1000
Ultra High-Strength Low Carbon Martensite M 800, 900, 1000, 1100, 1200, 1300, 1400, 1500
TABLE 4.2
SAE J2340 CHEMICAL LIMITS ON UNSPECIFIED ELEMENTS
Maximum Percent Allowed
Element Type A, B & R Type S Type X & Y Type D & M
P 0.100 0.100 0.060 0.020
S 0.015 0.020 0.015 0.015
Cu 0.200 0.200 0.200 0.200
Ni 0.200 0.200 0.200 0.200
Cr 0.150 0.150 0.150 0.150
Mo 0.060 0.060 0.060 0.06
Notes: 1) P= phosphorus S= sulphur Cu= copper Ni= nickel Cr= chromium
Mo= molybdenum
2) Maximum phosphorus shall be less than 0.050 on grades 180A & 180B.
3) The sum of Cu, Ni, Cr and Mo shall not exceed 0.50% when none of these elements are specified.
When one or more of Cu, Ni, Cr or Mo are specified, the sum limit of 0.50% does not apply. However,
the individual limits for the unspecified elements apply.
4-22

4.2.3.1 Gas metal arc welding (GMAW)
This process, schematically illustrated in Figure 4.15a), utilizes a
direct current electrical power supply with the electrode positive
(DCEP). The positive electrode attracts electrons flowing in the circuit.
The electrons act to melt the electrode wire that deposits within
the weld metal, mixing with molten material from the base metal.
Shielding to prevent oxidation of the hot wire and molten weld
pool region is provided by an inert shielding gas directed into the
weld region by the gas nozzle. The consumable electrode material
is selected to match the strength (and other important characteristics)
of the base metal. The wire guide and contact tube must be
periodically replaced in order to maintain good electrical contact.
Also, the gas nozzle must be occasionally cleaned of spattered
material.
The welding current is varied by changing the wire feed speed.
Higher wire feed speeds produce higher welding currents. The arc
length can be varied by changing the voltage setting. Higher voltages
produce longer arcs.
As illustrated in Figure 4.15b), there are four basic methods in
which the wire is transferred to the molten weld pool: short-circuiting,
globular, pulsed spray and spray transfer. These transfer modes
have been used to describe the GMAW process itself. Terms such
as “short arc”, “dip transfer MIG” and “spray” are all common
non-standard terms used to describe the GMAW process and the
mode of operation.
Short-circuiting transfer characteristics At low current and voltage,
short circuit transfer occurs. The weld is a shallow, penetrating one
with low heat input. Using GMAW in this mode allows welding in
all positions since the weld puddle is small. In comparison to the
other three modes of transfer, this method is slowest (low productivity).
This mode produces large amounts of spatter if welding variables
are not optimized. This mode, also know as short arc or dip transfer,
is used primarily for sheet metal applications.
Globular transfer characteristics This mode of transfer is obtained
at intermediate current and voltage levels or at high current and
voltage levels with 100% CO 2 shielding gas. It has higher heat
input and penetration than short circuit transfer. A larger weld pool
makes it more difficult to weld in the over-head position. It produces
significant amounts of spatter.
Pulsed spray and spray transfer characteristics Spray is achieved
at higher welding current and voltage with argon or helium based
shielding gas (over 80%Ar). This high-heat, deep-penetrating weld
limits the application to the flat position. This mode produces little
or no spatter and is known for the high deposition rate (higher
productivity). Pulsing the current where spray transfer occurs
allows for better control for out-of-position welding.
4-23

FIGURE 4.14
GAS METAL ARC WELDING (GMAW)
a) SCHEMATIC
b) METHODS OF WIRE TRANSFER
c) EFFECT OF SHIELDING GAS
4-24

In GMAW, the shielding gas (used for atmospheric shielding) also
affects the type of metal transfer in the process, penetration depth,
and the bead shape. These factors are schematically illustrated in
Figure 4.14c). The ionization potential of the gas is the ability of the
gas to give up electrons and is the characteristic that determines the
plasma characteristics of the arc. The ionization potential (IP) of the
gas can have an effect on welding characteristics such as arc heat,
stability, & starting:
• Helium, with high ionization potential, inhibits spray
transfer in steels.
• CO 2 , with moderate ionization potential also has limited
spray transfer.
• Argon, with low IP, promotes the spray mode - particularly
at higher currents.
Surface tension of the weld pool and metal droplets are also affected
by the type of shielding gas. Surface tension affects:
• The drop size.
• Puddle flow.
• Spatter
Argon results in high surface tension with shallower penetration.
CO 2 results in low surface tension with deeper penetration.
The advantages and limitations of GMAW are:
Advantages
• High deposition rates
• High Productivity
• No slag removal
• Continuous welding
• Easily automated
• Joint fit-up tolerance
Limitations
• Equipment is more expensive and
complex than some manual welding
processes
• Process variants/metal transfer
mechanisms make the process more
complex and the process window more
difficult to control
• Restricted access (the GMAW gun is
larger than other electrode holders)
• Spatter
• Porosity (especially with coated materials)
• Higher heat input than some processes
In summary, the GMAW process is ideally suited for many bumper
beam applications because of its high deposition rate that results in
high weld productivity. It is a process that is used on automated and
continuous welding lines and is often linked with robots and robotic
manufacturing cells. It is tolerant to moderate joint misalignment and
thus is suited for welding materials that might experience some
forming springback. It is a relatively clean process requiring no slag
removal from the weldment as do other types of welding processes.
It requires only occasional tip and gas cap maintenance.
4-25

4.2.3.2 Flux cored arc welding (FCAW)
GMAW equipment is more expensive than most manual welding
equipment. The complexity of process variants makes process
control more difficult, thus requiring experienced personnel. The
weld gun may have difficulty reaching into restricted spaces; thus,
design of parts and supplemental machinery must be considered.
Spatter and porosity discontinuities may occur if process parameters
are not fairly accurately controlled, leading to the need for weldment
inspection and possibly clean up and post weld repair. Finally,
heat input may need to be controlled, particularly when welding
high-strength and ultra high-strength bumper steels.
A useful reference document for GMAW is ANSI/AWS/SAE
Specification for Automotive and Light Truck Component Weld
Quality - Arc Welding (Reference 6.7).
As illustrated in Figure 4.15a), FCAW uses a tubular wire that is
filled with a flux. The arc is initiated between the continuous wire
electrode and the workpiece. The flux, which is contained within
the core of the tubular electrode, melts during welding, supplying
some cleaning action for the weld metal. It resolidifies as a slag
behind the weld shielding the hot weld from oxidation. Vapor
formant materials, contained in the flux core, decompose and
additionally shield the weld pool from the atmosphere. Direct
current, electrode positive (DCEP) is commonly employed as the
FCAW process.
There are two basic variants of the FCAW process as shown in
Figure 4.15b):
1. Self-shielded (without shielding gas).
2. Gas-shielded (with shielding gas).
Each variant uses different agents in the flux core. Usually, selfshielded
FCAW contains significant quantities of gas forming powder
that make this variant useful in outdoor conditions where wind
would blow away a shielding gas. The fluxing agents in self-shielded
FCAW are designed not only to shield the weld pool and metal
droplets from the atmosphere, but also to deoxidize the weld pool.
In gas-shielded FCAW, supplemental shielding gas is provided.
Thus, the flux generates only a secondary source of gas shielding
from the atmosphere. The main role of the flux is to support the
weld pool for out-of-position welds. Gas-shielded FCAW is often
used to increase the productivity of out-of-position welding and to
achieve deeper penetration welds.
The advantages and limitations of FCAW are:
Advantages
• High deposition rates
• Deep penetration
• High-quality
• Less pre-cleaning
than GMAW
• Slag covering helps
with larger
out-of-position welds
• Self-shielded FCAW
is draft tolerant
Limitations
• Slag must be removed
• More smoke and fumes than GMAW
• Spatter
• FCAW wire is expensive
• Equipment is more expensive and
complex than that for manual
welding
4-26

FIGURE 4.15
FLUX CORED ARC WELDING (FCAW)
a) SCHEMATIC
b) PROCESS VARIANTS (Reference 4.6)
4-27

4.2.3.3 Resistance spot welding (RSW)
In summary, the FCAW process offers deeper penetration and
higher deposition rates than the GMAW process, particularly in
out-of-position welds. Perhaps one of the most important advantages
of FCAW, particularly in bumper welding, is a tolerance for material
that has not been rigorously cleaned as the flux aids in the cleaning
operation during welding. However, slag must be removed from
the weldment, and smoke must be removed from the
manufacturing environment. If weld parameters are not set properly,
spatter on the weldment may become a problem.
A useful reference document for FCAW is ANSI/AWS/SAE
Specification for Automotive and Light Truck Component Weld
Quality – Arc Welding (Reference 6.7).
Resistance spot welding is the most common of the resistance
welding processes. It is used extensively in the automotive,
appliance, furniture, and aircraft industries to join sheet materials.
In this process, water-cooled, copper electrodes, as illustrated in
Figure 4.16a), are used to clamp the sheets to be welded into
place. The force applied to the electrodes insures intimate contact
between all the parts in the weld configuration. A current is then
passed across the electrodes through the sheets. The contact
resistances, which are relatively high compared to the bulk material
resistance, cause heating at the contact surfaces. The combination
of heat extraction by the chilled electrodes and rapid contact
surface heating causes the maximum temperature to occur roughly
around the faying surface. As the material near the faying surface
heats, the bulk resistance rises rapidly while the contact resistance
falls. Again, the peak resistance is near the faying surface, resulting
in the highest temperatures in that region. Eventually melting
occurs at the faying surface, and a molten nugget develops. On
termination of the welding current, the weld cools rapidly under
the influence of the chilled electrodes and causes the nugget to
solidify, joining the two sheets.
Acceptable-sized weld nuggets can be produced over a range of
currents as illustrated in the operating window or “lobe curve” presented
in Figure 4.16b). At the lower end of the current range is the minimum
nugget size, which can be found in a resistance-welding manual and
is based on the diameter of the electrode face. At the upper end
of the current range is the expulsion limit. Expulsion is a condition
in which the weld nugget grows to a size that cannot be contained
by the electrode force; molten metal bursts out of the weld seam.
The current range over which an acceptable nugget size is
obtained is a measure of the robustness of the welding process. A
wide current range indicates that significant variations in the
process can occur while maintaining some minimum weld quality.
A narrow range, on the other hand, indicates that minor variations
in process conditions can result in unacceptable weld quality.
The lobe curve graphically represents the range of acceptable
welding currents as a function of welding time. The minimum and
expulsion currents are determined for a number of welding times
at a particular electrode force. Separate lines are drawn to connect
the minimum weld size currents and the expulsion currents.
The required current level for making a consistently sized weld
(presumably just below expulsion) is probably the simplest method
of defining weldability. This measure of weldability is an indication
of the size of welding transformers required to weld the materials
of interest.
4-28

FIGURE 4.16
RESISTANCE SPOT WELDING (RSW)
a) SCHEMATIC
b) LOBE CURVE
FIGURE 4.17
RESISTANCE PROJECTION WELDING (RPW)
SEQUENCE OF PROJECTION COLLAPSE
4-29

The advantages and limitation of RSW are:
Advantages
Limitations
• High speed, (

Projection welding is not limited to sheets. Any joint whose projection
(contact area) is small compared to the thickness of the parts being
welded is a candidate for projection welding.
The purpose of a projection is to localize the heat and pressure at a
specific location in a joint. The projection design determines the
current density required. Projections in sheet metal parts are
generally made by embossing, as opposed to projections in solid
metal pieces that are made by either machining or forging. In the
case of stamped parts, projections are generally located on the
edge of the stamping.
The advantages and limitations of RPW are:
Advantages
Limitations
• Satisfactory heat • Requires an additional operation to
balance for welding form projections
difficult combinations • Requires accurate control of projection
• Uniform results height and precise alignment of the
• Increased output welding dies with multiple welds
because welds are • Requires higher capacity equipment
being made
than spot welding
simultaneously • Sheet metal thickness limited by ability
• Longer electrode life to form projections
• Welds may be closely
spaced
• Parts easily welded in
assembly fixture
• Improved surface
appearance
• Parts welded that
cannot be resistance
spot welded
RPW offers significant production advantages. The welding electrodes
are flat and contact a large surface area on the parts being joined.
Also, electrode life is improved and the electrodes require less
attention and maintenance that those used in resistance spot welding.
In resistance spot welding, if the welds are too closely spaced, the
welding current is shunted through a previously finished weld. In
RPW, multiple welds may be made simultaneously. Thus, shunting
is less of an issue and welds may be more closely spaced than in
resistance spot welding. However, if more that three projections
are welded simultaneously, the height of the projections must be
uniform to avoid some projections fusing before others have made
contact. Alternately, ample pressure in conjunction with a double
weld cycle (one schedule) may be run. The first weld should be
short in time and high in current. The first hit buries and evens out
the projections. The second weld should be longer in time and
lower in current. The second hit tempers the welds.
In conventional spot welding, parts may be located by an assembly
fixture and moved to make a second or third spot-weld. When
using projection welding, the parts are simply placed in a nest and,
with one operation of the machine; all welds are made at once.
One part may be located in relation to the other by punching holes
in one and matching them with semi-punchings from the other.
4-31

4.2.3.5 Resistance seam welding (RSeW)
Small parts, such as brackets or handles, are difficult to locate in a
spot welding machine, which results in misplaced spots or extruded
metal. Neat embossing would be less unsightly and a fitted electrode
would not mark the exposed surface.
RPW has some limitations. The formation of projections may
require an additional operation unless the parts are press-formed to
design shape. With multiple welds, accurate control of projection
height and precise alignment of the welding dies are necessary to
equalize the electrode force and welding current. With sheet
metal, the RPW process is limited to the thickness in which projections
with acceptable characteristics can be formed.
RSeW is a variation on resistance spot welding. In this case, the
welding electrodes are motor driven wheels, which produce a
“rolling” resistance or seam weld. There are three independent
parameters: power supply and control, welding wheel configuration
and sheet configuration.
Power supply and control governs the frequency with which current
is applied to the workpiece. Depending on this frequency and the
speed with which the material is being welded, the weld will be a
continuous seam weld, an overlapping seam weld or a roll spot
weld as illustrated in Figure 4.18a).
Seam welds are typically used to produce continuous gas-tight or
liquid-tight joints in sheet assemblies, such as automotive fuel tanks.
The process is also used to weld longitudinal seams in structural
tubular sections such as bumper beams. In fuel tanks, the use of
overlapping or continuous seam welds is mandatory. However,
bumper beams do not require leak-tight seams and roll spot welds
may be used.
Typical lobe curves for RSeW are presented in Figures 4.18b) and
c)(Reference 4.7). The major variables that control the quality of
seam welds are current (impulse or continuous), speed and force.
These variables are plotted for both uncoated and hot-dip galvanized
steels. It can be noted that as the speed increases, a limit is
reached where a non-continuous seam is produced. Likewise, as
the current is increased, a point is reached where surface eruptions
or expulsion occurs and the copper from the electrodes melts and
may cause additional cracking. In general, increased electrode
force tends to increase the acceptable lobe size and move it to
higher current levels. For coated steels, the speed tends to be
reduced and the current increased.
The advantages and limitations of RSeW are:
Advantages
Limitations
• High Speed • Higher equipment costs than arc welding
• Excellent for sheet • Power line demands
metal applications • Nondestructive testing
[

FIGURE 4.18
RESISTANCE SEAM WELDING (RSeW)
Surface Eruption, Cu Contamination Cracking
Lower Speed
Higher Current
CURRENT, kA
Non-Continuous
Seam
CURRENT, kA
Units
as per
b
FORCE N
FORCE lb.
SPEED, in./min.
SPEED, mm/sec
a) SEAM VARIATIONS b) LOBE CURVE FOR UNCOATED
LOW CARBON STEEL
FORCE N
FORCE lb.
SPEED, in./min.
SPEED, mm/sec
c) LOBE CURVE FOR HOT-DIP
GALVANIZED LOW CARBON STEEL
FIGURE 4.19
RESISTANCE PROJECTION SEAM WELDING (RPSeW)
a) SCHEMATIC b) SEAM GEOMETRY
4-33

4.2.3.6 Resistance projection seam welding (RPSeW)
The advantages of high speed, applicability to sheet materials and
no need for filler metal make RSeW ideally suited for the closure
welding of bumper beam tubes in a high speed automated fabrication
line. Often these lines consist of a steel coil (slit to the proper
width) being fed from a pay-off reel into a continuous roll forming
line. The line forms the required tubular cross section. The seam
welder then closes the open tube. The formed and welded tubular
section may then go through an induction heat-treating device or
into a sweep forming device, and finally into a cutter, which cuts
the beam to length.
The limitations of RSeW include higher initial equipment costs
compared to arc welding and higher power costs compared to arc
welding. In addition, electrode wear and maintenance and the lack
of non-destructive testing techniques to assure good welds must be
addressed. Finally, because RSeW is suited to lap joints (rather than
butt joints as used in arc welding), a slight increase in part weight
occurs.
In conventional projection welding (RPW), the current is concentrated
exactly at the weld location. A relatively new process, resistance
projection seam welding as illustrated in Figure 4.19a), does the
same thing in seam welding (Reference 4.8). In RSeW, a projection
is rolled into one of the sheets to be welded on a roll forming line.
The sheet with the projection, and the sheet to which it is to be
welded, are presented into the resistance seam-welding machine
where current is passed through two opposed rolls. The current
must flow through the projection thus concentrating its density as
in conventional projection welding.
The shape of the projection has been studied and both the continuous
projection geometry and the dimple projection geometry (as
illustrated in Figure 4.19b), have been successfully used. The
continuous projection makes a continuous weld, but requires more
total energy input. The dimple projection makes an intermittent
seam; but requires less total energy input.
The advantages and limitations of RPSeW are:
Advantages
• Satisfactory heat
balance for welding
difficult combinations
• Uniform results
• Reduced total energy
consumption
• Longer electrode life
• Parts easily welded
in assembly fixture
surface
• Improved surface
appearance
• Parts welded that
cannot be resistance
spot welded
Limitations
• Requires an additional operation to form
projections
• Requires accurate control of projection
height and precise alignment of the
welding dies
• Sheet metal thickness limited by
ability to form projections
4-34

The advantages of RPSeW are: heat balance problems are solved,
the welds are uniform, welding speed is increased and total energy
consumption is reduced. The preparation of the projection, however,
requires an additional step. This issue may not be too great a
concern if the projection is formed on the same roll forming line
used to make a part. However, control of the projection size and
design is still an issue.
4.2.3.7 High frequency and induction resistance seam welding (RSeW - HF&I)
High frequency welding includes those processes in which the
coalescence of metals is produced by the heat generated from the
electrical resistance of the work to high frequency current, usually
with the application of an upsetting force to produce a forged
weld.
There are two processes (Reference 4.9) that utilize high frequency
current to produce the heat for welding: high frequency resistance
welding (HFRW), as illustrated in Figure 4.20a), and high frequency
induction welding (HFIW), sometimes called induction resistance
welding, as illustrated in Figure 4.20b). The heating of the work in
the weld area and the resulting weld are essentially identical with
both processes. With HFRW, the current is conducted into the
work through electrical contacts that physically touch the work.
With HFIW, the current is induced in the work by coupling with an
external induction coil. There is no physical electrical contact with
the work. A characteristic of high frequency current is that it travels
as close to the “vee” edge as possible, thus treating only the
surfaces that are to be welded.
Although the welding process depends upon the heat generated
by the resistance of the metal to high frequency current, other
factors must also be considered for successful high frequency welding.
Because the concentrated high frequency current heats only a
small volume of metal (just where the weld is to take place), the
process is extremely energy efficient, and welding speeds can by
very high. Materials handling, forming and cutting limit the
maximum line speed. Minimum line speed is set by material
properties and weld quality requirements.
The fit of the surfaces to be joined and the manner in which they
are brought together is important if high-quality joints are to be
produced. Flux is not usually used but can be introduced to the
weld area in an inert gas stream. Inert gas shielding of the welding
area is generally needed only for joining reactive metals such as
titanium and certain stainless steel products.
The advantages and limitations of high frequency welding processes
are:
Advantages
• Produces welds with
very narrow heataffected
zones
• High welding speed
and low power
consumption
• Able to weld very
thin wall tubes
• Minimizes oxidation
and discoloration as
well as distortion
Limitations
• Special care must be taken to avoid
radiation interference in the plant’s
vicinity
• Uneconomical for products required
in small quantities
• Needs proper fit-up
• Hazards of high frequency current
4-35

FIGURE 4.20
HIGH FREQUENCY AND INDUCTION RESISTANCE SEAM WELDING (RSeW-HF&I)
a) HIGH FREQUENCY RESISTANCE WELDING b) HIGH FREQUENCY INDUCTION WELDING
FIGURE 4.21
UPSET WELDING (UW)
a) SCHEMATIC b) PLATEN MOTION
4-36

High frequency welding processes offer several advantages over
low frequency and direct current resistance welding processes.
One characteristic of the high frequency processes is that they can
produce welds with very narrow heat-affected zones. The high
frequency welding current tends to flow only near the surface of
the metal because of the “skin effect” and along a narrow
controlled path because of the “proximity effect”. The heat for
welding, therefore, is developed in a small volume of metal along
the surfaces to be joined. A narrow heat-affected zone is generally
desirable because it tends to give a stronger welded joint than the
wider zone produced by many other welding processes. With
some alloys, the narrow heat-affected zone and absence of cast
structure may eliminate the need for post-weld heat treatment to
improve the metallurgical characteristics of the welded joint. The
shallow and narrow current flow path results in extremely high
heating rates and therefore, high welding speeds and low-power
consumption. A major advantage of the continuous high frequency
welding processes is their ability to weld at very high speeds. high
frequency welding can also be used to weld very thin wall tubes.
Wall thicknesses down to 0.13mm(0.005 inches) is presently being
welded on continuous production mills. The processes are
adaptable to many steels including low carbon, low-alloy and
stainless steels. Because the time at welding temperature is very
short and the heat is localized, oxidation and discoloration of the
metal as well as distortion of the part are minimal.
As with all processes, there are limitations. Because the equipment
operates in the radio frequency range, special care must be taken
in its installation, operation, and maintenance to avoid radiation
interference in the plant’s vicinity. As a general rule, the minimum
speed for carbon steel is about 7.6m/min(25 feet/min). For
products that are only required in small quantities, the high
frequency processes may be uneconomical unless the technical
advantages justify the application. Because the high frequency
processes utilize localized heating in the joint area, proper fit-up is
important. Equipment is usually incorporated into mill or line
operation and must be fully automated. The process is limited to
the use of coil, flat, or tubular stock with a constant joint symmetry
throughout the length of the part. Any disruption in the current
path or change in the shape of the vee can cause significant
problems. Special precautions must be taken to protect plant
personnel from the hazards of high frequency. The high frequency
processes have found applications in the seam welding of bumper
reinforcement beams on continuous lines.
4-37

4.2.3.8 Upset welding (UW)
UW is a resistance welding process that produces coalescence
over the entire area of faying surfaces, or progressively along a
butt joint, by the heat obtained from the resistance to the flow of
welding current through the area where those surfaces are in
contact. Usually DC current is used for the heating, with the
parts clamped in electrical contacting dies, one stationary and
the other movable as illustrated in Figure 4.21a). Pressure is used
to complete the weld.
The movable clamping die (or platen motion) is presented in
Figure 4.21b). At first, the motion brings the parts into intimate
contact. Then the weld current is energized. In joints with
normal fit-up, some thermal expansion may be seen as the parts
heat. Joints with poor fit-up tend to experience a joint seating
motion during this period. At a point in time when sufficient
heating has occurred, a rapid forging force is applied and the
abutting parts are rapidly forced into each other, causing some
outward material flow.
With this process, welding is essentially done in the solid state.
The metal at the joint is resistance heated to a temperature
where recrystallizaion can rapidly take place across the faying
surfaces. A force is applied to the joint to bring the faying
surfaces into intimate contact and then upset the metal. Upset
hastens recrystallization at the interface and, at the same time,
some metal is forced outward from this location. This tends to
purge the joint of oxidized metal.
Upset welding has two variations:
1. Joining two sections of the same cross section end-to-end
(butt joint).
2. Joining of sections with differing cross sections such as a
stud to a plate.
The first variation can also be accomplished by flash welding.
The second variation is also done with resistance projection
welding.
The advantages and limitations of UW are:
Advantages
Limitations
• Some flexibility in • Produces unbalance on three-phase
cross section shape primary power lines so often DC
• Rapid process, can current is used
be automated • Requires special equipment for
• Impurities can be removal of flash metal
removed during • Difficult alignment for workpieces
upset
with small cross sections
• Can weld rings and • Requires part cross section
various cross sections consideration
The upset welding of butt joints is fast and can be automated.
There is some flexibility in joint design. However, control of the
joint tolerances is critical. The process requires large amounts of
current so DC rectified current is usually used to improve
efficiency. In some applications, the weld flash must be
removed.
The upset butt process involves relatively slow heating and no
measures are taken to protect the joint from air. Consequently, a
generous upset is required to exude oxidized metal. For this reason,
other butt welding processes such as flash, percussion or friction
welding are often preferred.
4-38

4.2.3.9 Friction welding (FRW)
FRW is a process that produces a weld under a compressive
force (Reference 4.10). As illustrated in Figure 4.22a), the work
pieces are brought into contact and rotated very rapidly to
produce heat. Usually one piece is rotated against a stationary
piece to produce the heat at the junction. The rotation time and
force are adjusted until the temperature in the joint reaches the
forging temperature of the material at which time the rotation is
stopped and an axial force is applied to forge weld the pieces
together. As such, the process is a solid-state bonding process.
Geometries that have a rotational symmetry are particularly
suitable for friction welding. Applications include round bars and
tubes to each other, as well as bars or tubes to sheet steel.
Linear friction welding is used for parts with non-rotational
symmetry. In this application, one part is oscillated back and
forth against the other (Figure 4.22b).
The advantages and limitations of FRW are:
Advantages
• Faster than most
other processes
• Can join dissimilar
material together
(e.g.) Copper to
steel
• Easily automated
for high-volume
production
Limitations
• Start-up cost is high
• Parts must be able to rotate about an
axis of symmetry
• Free machining alloys are difficult to
weld
• Non-forgeable materials cannot be
friction welded
4.2.3.10 Laser beam welding (LBW)
FRW is fast and can join many different materials. It is one of
only a few welding processes that has this material variability. It
is easily automated. However, part geometry can be a limitation;
and, in general, the materials to be joined must be hot forgeable.
“LASER” is an acronym for “light amplification by stimulated
emission of radiation.” A laser beam that becomes highly
focused is an excellent source of concentrated energy. This energy
is used for many welding applications and also for cutting and
heat treating.
Two basic types of lasers are used in welding: solid-state and gas
(Reference 4.10). Solid-state lasers are made of a single elongated
crystal rod. Nd:YAG (a doped crystal of neodymium with yttrium,
aluminum, and garnet) is the most common solid-state laser used
for welding today. The end surfaces of the rod are ground flat
and parallel. These ends usually have a reflectivE-coating placed
on them. While one end is totally reflective, the other end is partially
reflective, leaving a small area for photons to escape. The Nd
ions excite their electrons to a higher energy level. By doing this,
photons are emitted at a wavelength of 1.06 microns. After the
photons are emitted, the electrons are allowed to return to their
original state.
4-39

FIGURE 4.22
FRICTION WELDING (FRW)
a) PART ROTATION b) PART OSCILLATION
FIGURE 4.23
LASER BEAM WELDING (LBW)
a) CARBON DIOXIDE LASER
b) BEAM FOCUS
4-40

The most common gas laser is the carbon dioxide laser (see
Figure 4.23a). It is also the laser used for most welding applications.
An electrical charge excites the carbon dioxide molecules, which
on their return to their normal energy state emit some photons.
Much like solid-state lasers, reflective surfaces are placed at the
ends of the tube in which the gas is contained. The one end is
totally reflective, while the other allows a small amount of light to
pass. This light is emitted at a wavelength of 10.6 microns.
Factors affecting the choice between gas and solid-state lasers are:
Nd:YAG lasers: most metals absorb its wavelength better than
the CO 2 laser wavelength, versatile fiber-optic delivery, easy
beam alignment, easier maintenance, smaller equipment, and
more expensive safety measures than CO 2 because of its wavelength.
CO 2 lasers: higher power, better beam quality in terms of focus
ability, higher speeds and deeper penetration for materials that
don’t reflect its light, and lower start-up and operation.
In laser welding, the beam can be focused for different applications
as illustrated in Figure 4.23b). Usually, a small focus size is used
for cutting and welding, while a larger focus is used for heat treatment
or surface modification. The focal spot of the beam can also be
varied based on the application.
The advantages and limitations of LBW are:
Advantages
Limitations
• Single pass weld • High initial start-up costs
penetration in • Part fit-up and joint tracking are
steel up to 19mm critical
(0.75 inches) thick • Not portable
• Materials need • High cooling rates may lead to
not be conductive material problems
• No filler metal
required
• Low heat input
produces low
distortion
LBW advantages include the very rapid weld travel speed and
the low heat input that results in very little distortion. However,
initial equipment costs for laser welding are high. Additional
costs to assure good part fit-up may be of some disadvantage.
Coatings on steel can be a problem in plume formation through
which the laser beam cannot adequately penetrate. Fume control
shielding gas may be required.
4.2.3.11 Laser beam and plasma arc welding (LBW/PAW)
There have been a number of experimental developments in
welding processes using the laser welding process as a base and
coupling a second welding process (such as plasma arc welding)
with it. The benefit is that the high travel speed associated with
the laser process is combined with the metal fill, the less stringent
part fit-up and the favorable bead shape associated with the plasma
arc process. Two variations of the LBW/PAW process are
described in two patents (References 4.11 and 4.12).
4-41

4.2.4 Weldability of bumper materials
The heat of welding causes changes in the microstructures and
mechanical properties in a region of heated steel that is referred
to as the heat-affected zone (HAZ). The resulting microstructure
in the HAZ will depend on the composition of the steel and the
rate at which the steel is heated and cooled. The degree of
hardening in the HAZ is an important consideration determining
the weldability of a carbon or low-alloy steel. Weldability and
resistance to hydrogen cracking generally decrease with increasing
carbon or martensite in the weld metal or the HAZ, or both.
Although carbon is the most significant alloying element affecting
weldability, the effects of other elements can be estimated by
equating them to an equivalent amount of carbon. Therefore,
the effect of total alloy content can be expressed in terms of a
carbon equivalent (CE). One empirical formula that may be used
for judging the risk of underbead cracking in carbon steel is:
CE = C + Mn + Cr + Mo + V + Ni + Cu
6 5 15
Generally, steels with low CE values (e.g., 0.2 to 0.3) have excellent
weldability; however, the susceptibility to underbead cracking
from hydrogen increases when the CE exceeds 0.40.
4.2.5 Ranking of welding processes
David Dickinson, The Ohio State University, used his experience
and the results of a State-of-the-Art Welding Survey (Reference
4.5), to rank the suitability of various welding processes for
joining bumper steels. His “poor”, “acceptable”, “better” and
“best” rankings are given in Table 4.3. Note: The rankings for
10B21 Modified were added to the Table by the American Iron
and Steel Institute’s Bumper Project Group. The rankings are
subjective and should not be taken as absolute. However, they
do provide a starting point for the selection of a welding process.
The welding processes in Table 4.3 were all identified in
Dickinson’s SOA Survey as ones that are currently used in
bumper manufacture, or were used to produce prototype
bumpers. The processes, described in Sections 4.2.3.1 to
4.2.3.11, are:
1. Gas metal arc welding (GMAW)
2. Flux cored arc welding (FCAW)
3. Resistance spot welding (RSW)
4. Resistance projection welding (RPW)
5. Resistance seam welding (RSeW)
6. Resistance projection seam welding (RPSeW)
7. High frequency and induction resistance seam welding
(RSW-HF&I)
8. Upset welding (UW)
9. Friction welding (FRW)
10. Laser beam welding (LBW)
11. Laser beam and plasma arc welding (LBW/PAW)
4-42

TABLE 4.3
RANKING OF WELDING PROCESSES BY BUMPER MATERIAL
BUMPER
MATERIAL 1
WELDING PROCESSES 3, 4
MATERIAL
STANDARD 2
GMAW
FCAW
RSW
RPW
RSeW
RPSeW
RSeW-HF&1
UW
FRW
LBW
LBW/PAW
UNCOATED
CQ
SAEJ2329 (Grade 1)
B
B
B
B
B
B
B
b
b
b
b
DQSK
SAEJ2329 (Grades 2 & 3)
B
B
B
B
B
B
B
b
b
b
b
DQAK
SAEJ2329 (Grades 2 & 3)
B
B
B
B
B
B
B
b
b
b
b
35XLF
SAEJ1392 (035XLF)
B
B
B
B
B
B
B
b
b
b
b
50XLF
SAEJ1392 (050XLF)
B
B
B
B
B
B
B
b
b
b
b
55XLF
SAEJ1392 Modified
B
B
B
B
B
B
B
b
b
b
b
80XLF
SAEJ1392 (080XLF)
B
B
B
B
B
B
B
b
b
b
b
120XF
SAEJ2340 (830R)
b
b
B
B
B
B
B
b
b
b
b
135XF
SAEJ2340 Modified
b
b
B
B
B
B
B
b
b
b
b
140T
SAEJ2340 (950DL)
b
b
B
B
B
b
B
b
b
b
b
M190HT
SAEJ2340 (1300M)
b
b
b
b
b
b
b
b
b
b
b
10B21 (Modified)
SAEJ403 (10B21 Modified)
B
B
g
g
b
g
B
b
b
b
b
COATED
HDG/EG
—
b
b
g
g
g
g
g
b
b
p
p
1. Refer to Section 4.2.5 and Tables 2.1, 2.2, 2.3, 5.4 and 5.5 for bumper material definitions and properties.
2. See References 4.13, 4.14, 4.15 and 6.4.
3. Refer to Section 4.2.3 for welding process definitions.
4. p = poor g = acceptable b = better B = best
4-43

All of the materials in Table 4.3 are commonly used for production
bumpers. Examples are given in Tables 5.4 and 5.5 along with a
description of each bumper material. In Table 4.3, the welding
processes are ranked for the following materials:
Hot rolled or cold rolled (uncoated) sheet steel
1. CQ Commercial quality
2. DQSK Drawing quality, special killed de-oxidation
practice.
3. DQAK Drawing quality, aluminum killed.
4. 35XLF High-strength low-alloy with sulphide inclusion
control, low carbon, 240 MPa (35 ksi) yield
strength.
5. 50XLF High-strength low-alloy with sulphide inclusion
control, low carbon, 345MPa (50ksi) yield
strength.
6. 55XLF High-strength low-alloy with sulphide inclusion
control, low carbon, 380MPa(55ksi) yield
strength.
7. 80XLF High-strength low-alloy with sulphide inclusion
control, low carbon, 550MPa (80ksi) yield
strength.
8. 120XF High-strength low-alloy with sulphide inclusion
control, low carbon 830MPa (120ksi) yield
strength.
9. 135XF High-strength low-alloy with sulphide inclusion
control, low carbon 920MPa (135ksi) yield
strength.
10. 140T Dual phase structure contains martensite in
ferrite matrix, excellent formability prior to strain
aging, 965MPa (140ksi) tensile strength.
11. M190HT Martensitic quality, 1310MPa (190ksi) tensile
strength.
12. 10B21 Carbon-Boron steel, 1140MPa (165ksi) yield
(Modified) strength after hot forming and quenching.
hot-dip galvanized or electrogalvanized sheet steel
13. HDG/EG Includes materials one through 12 (above) that
have been hot-dip galvanized or electrogalvanized.
The ranking of the welding processes for
individual materials (one through 12) in the
galvanized condition becomes quite complex
because of the dual effect of steel grade and
metallic coating on weld ability. Thus, one
overall ranking is given for each of materials one
through 12 in either the hot-dip galvanized or
the electrogalvanized condition for each
welding process.
4-44

The following is an overall explanation of the rankings assigned in
Table 4.3:
Arc welding (GMAW and FCAW)
In general, all steel bumper materials may be arc welded without
difficulty. Selection of an appropriate filler metal with proper
strength is all that is required. Welding consumable manufacturers
can assist with this selection.
Consideration should be given to the heat-affected zone in arc
welded joints. The graphs in Figure 4.24 are diagrammatic
representations of the heat-affected zone for arc welded steel
bumper materials. Actual plots are available from steel suppliers
and welding consumable manufacturers.
Figure 4.24 indicates that as the carbon content in the steel
increases, the hardness at the fusion line increases. For example,
the carbon content of a martensitic steel depends on its strength
level. A higher strength level has a higher carbon content. Figure
4.24 indicates that a martensitic steel with a higher carbon content
has increased hardness at the fusion line. Dual phase steel is
another example. The carbon content of dual phase steel depends
on its production process - as rolled, batch annealed or continuous
annealed. All three have different carbon levels and different
fusion line hardness.
Figure 4.24 also indicates that some steel materials undergo softening
and a loss of strength in the heat-affected zone (e.g., microalloy,
dual phase, recovery annealed and martensitic materials). Lower
heat input during welding helps reduce the degree of softening.
Higher strength materials are slightly more difficult to weld than
lower strength materials because of the springback associated with
higher strength parts. Fixturing, to hold the parts firmly in place
during welding, is often required to get defect free welds.
Galvanized coatings on steel can cause minor difficulties with arc
welding. For example, zinc has a much lower melting and
vaporization point than steel. Thus, during welding, zinc fumes are
generated. They may be captured by a ventilation system. Also,
intermetallic zinc inclusions may be formed during welding.
However, inclusions may be minimized by using the FCAW
process. The flux scavenges the inclusions and they are removed
along with the flux.
Resistance welding (RSW, RPW, RSeW and RPSeW)
A comparison of resistance spot weldabilty is given in Figure 4.25
for hot rolled, cold rolled and galvanized sheets. Welding lobes
are given for representative bumper materials. The lobes are somewhat
arbitrary. However, they do allow a rough comparison of the
spot weldability of steel materials. For a given material, a welding
lobe is expressed as weld time verses weld current at a constant
electrode force level.
4-45

FIGURE 4.24
HARDNESS IN HEAT-AFFECTED ZONE OF ARC WELDS
Hardness
Distance From Fusion Line
4-46

FIGURE 4.25
RESISTANCE SPOT WELDING COMPARISON
a) HOT ROLLED SHEET
b) COLD ROLLED SHEET
c) GALVANIZED SHEET
4-47

Each lobe is a three dimensional diagram. The larger rectangular
plane in a lobe represents the base line of weldability. This
base line diminishes into the depth of the page to a smaller
plane. The reduction in plane size represents sensitivity to
some weld parameter such as electrode force. Thus, when
the two planes are almost the same size, the material is weldable
over a wide range of parameters. On the other hand, if one
plane is considerably smaller than the other, weldability losses
are expected with a change in parameter. For galvanized sheets,
the coating has a marked effect on weldability. To represent
the effect of the coating, a square has been placed onto the
smaller plane.
The lobes in Figure 4.25 are sometimes referred to as operating
windows. Weld current and time must be within an operating
window to achieve a sound weld. A small operating window
means a high degree of control is required in the welding
process. Thus, materials with small operating windows are
regarded as less weldable than materials with large windows.
CQ and DQ hot and cold rolled materials are weldable over a
wide range of welding currents and times. Their excellent
weldability is often taken as the base against which other
materials are compared. CQ and DQ are only minimally
affected by electrode force (A high electrode force reduces
contact resistance. Thus, either more current or a longer weld
time is required). Weld nuggets in CQ and DQ materials are
ductile and strong.
The hot and cold rolled XLF materials have excellent weldability.
They closely match the weldability of CQ and DQ. The XLF
materials obtain their strength from microalloying elements
(precipitation hardening) and controlled rolling (fine grain
size). During welding, loss of precipitation hardening and
grain growth may occur, resulting in strength loss in the heataffected
zone. Usually, the effect is minimal and does not hinder
the application of XLF materials.
120XF and 135XF hot and cold rolled sheets generally obtain
their strength through cold work and recovery annealing.
While there is no problem welding these materials, a reduction
in hardness and strength in the heat-affected zone can occur.
Using the lowest current and shortest weld time prevents over
welding and improves heat-affected zone strength.
Weldability tests on hot and cold rolled dual phase (e.g. 140T)
steels show they respond very similar to other steels at their
strength level.
Martensitic hot or cold rolled sheet (e.g., M190HT) obtains its
strength through the quench hardening of somewhat higher
carbon steel to martensitic steel. Resistance weld nuggets
tend to be brittle and subject to cracking failure. Also,
strength loss, through tempering of the base metal, can occur
in the heat-affected zone. Regardless, martensitic steels are
resistance weldable provided some precautions are taken during
welding.
4-48

Galvanized coatings add a complexity to welding. In general, as
the strength level of the base steel increases, weldability decreases.
Also, as strength increases, the required electrode force increases.
The effect of the coating on the electrode, plus the higher welding
force, cause reduced weldability as indicated by the smaller
operating windows for galvanized materials. Coatings also
reduce electrode life; thus, the condition of the electrodes must
be closely monitored during welding. Frequent dressing or
replacement of the electrodes is required.
High-frequency welding (RSeW-HF&I)
All of the current bumper materials are readily joined by high
frequency welding. High frequency welds have only a small
heat-affected zone because the welding current is concentrated
on the surfaces to be welded. In addition, the squeeze at the
point of weld consummation forces any inclusions in the molten
weld metal out of the weld zone. Galvanized coatings have little
affect on weldability since the heated region of a joint is small.
Also, there is little vaporization of the coating and fuming.
Upset and friction welding (UW and FRW)
Upset and friction welding both result in relatively low heating.
Thus, the heat-affect zone not only is small but also contains
minimal softening. It is very difficult to align sheet steel parts
with these processes. Thus, they are mainly used for bar stock
and thicker steel.
Laser welding (LBW and LBW/PAW)
A laser beam is finely focused and usually associated with higher
travel speed, therefore, a laser weld has a very small heat-affected
zone due to the higher cooling rate. Thus, any loss of strength in
the welded materials, even higher strength ones, is minimal. This
process requires excellent fit-up, which is sometimes difficult to
achieve during production, especially with higher strength materials
due to springback. The vaporization of galvanized coatings can
cause a plume, which blocks the laser beam. In such a case, a
fume control shielding gas may be used.
4-49

5. Design concepts
5.1 Sweep (roll formed sections) and depth of draw (stampings)
The current styling trend for vehicles is toward rounded,
aerodynamic shapes. This trend has impacted bumper design and
challenged bumper manufacturers to provide the highly rounded
shapes desired by vehicle stylists. Steel bumper manufacturers have
met the challenge and are providing the contours required for both
reinforcing beams and facebars.
A convenient way of defining the degree of roundness for a
stamped or roll formed reinforcing beam is to use the concept of
sweep. Sweep expresses the degree of curvature of the outer
bumper face, or the face farthest removed from the inside of the
vehicle. Sweep is defined in Figure 5.1 and Tables 5.1 and 5.2.
Sweep in the camber, X, for a 60 inch (1524 mm) chord length, L,
of a given circle of radius, R. Sweep is expressed as the number of
one-eighth inches (3.18 mm). For example, if X is 5 inches (127
mm) for an L of 60 inches (1524 mm), the sweep would be 40.
Tables 5.1 and 5.2 indicate that a sweep number of 40 corresponds
to a radius of curvature of 92.5 inches or 2350 mm. Tables 5.1 and
5.2 also list the cambers for chord lengths smaller than 60 inches
(1524 mm). For example, if the camber is 2.711 inches (68.9 mm)
and the chord length is 40 inches (1016 mm), the sweep number is
50. The concept of sweep applies well to a reinforcing beam
because it has a near constant radius of curvature and no wrap
arounds at the end of the reinforcing beam.
Depth of draw is often used to describe the amount of rounding
and wrap around on a bumper section, and in particular, a stamped
facebar. As shown in Figure 5.2, depth of draw is the distance, X,
between the extreme forward point on a bumper and the extreme
aft point on a bumper. This distance has a physical significance in
that it cannot exceed the opening available with a given stamping
press. X is usually stated in inches (millimeters).
5.2 Tailored Products
There are two types of tailored products used for bumper beams:
laser welded blanks and tailor rolled blanks.
A laser welded blank joins two or more flat steel blanks together
with laser welding prior to forming. The blanks can have different
strengths and thicknesses so that the formed end product has
extra thickness and/or strength where it is needed. Examples of
laser welded blanks are shown in Figure 5.3.
A tailor rolled blank is created by sending a steel coil through a tailor
rolling process where the thickness is reduced in certain areas with
compressive rollers. The variable thickness coil can then be
blanked to create a tailor rolled blank. The tailor rolled blank can
then be stamped or hot formed into a component that has extra
thickness where it is needed. In the future, it may even be possible
to send a tailor rolled coil through a roll forming line to produce
roll formed parts with variable thicknesses.
Both laser welded blanks and tailor rolled blanks have been
implemented into production for bumper beams and are considered
a viable method of mass reduction for steel bumper systems.
5-1

5-2
FIGURE 5.1
DEFINITION OF SWEEP

TABLE 5.1
SWEEP NUMBERS (CAMBER, X, INCHES)
SWEEP
NO.
CHORD LENGTH, L, INCHES
30 35 40 45 50 55 60
RADIUS
(inches)
1
0.031
0.043
0.056
0.070
0.087
1.105
0.125
3600.0
10
0.311
0.424
0.554
0.701
0.866
1.048
1.250
360.6
15
0.466
0.635
0.830
1.050
1.297
1.569
1.875
240.9
20
0.622
0.847
1.107
1.402
1.732
2.098
2.500
181.3
25
0.773
1.052
1.374
1.749
2.164
2.621
3.125
145.6
30
0.926
1.263
1.652
2.095
2.592
3.143
3.750
121.9
35
1.072
1.474
1.924
2.445
3.023
3.673
4.375
104.9
40
1.224
1.670
2.188
2.776
3.442
4.182
5.000
92.5
45
1.373
1.872
2.455
3.167
3.867
4.701
5.625
82.8
50
1.513
2.067
2.711
3.449
4.282
5.214
6.250
75.1
55
1.659
2.264
2.973
3.782
4.703
5.731
6.875
68.9
60
1.790
2.449
3.218
4.103
5.106
6.236
7.500
63.8
5-3

TABLE 5.2
SWEEP NUMBERS (CAMBER, X, MILLIMETERS)
SWEEP
NO.
CHORD LENGTH, L, MILLIMETERS
762 889 1016 1143 1270 1397 1524
RADIUS
(mm)
1
0.79
1.09
1.42
1.78
2.21
2.67
3.18
91440
10
7.90
10.8
14.1
17.8
22.0
26.6
31.8
9159
15
11.8
16.1
21.1
26.7
32.9
39.9
47.6
6119
20
15.8
21.5
28.1
35.6
44.0
53.3
63.5
4605
25
19.6
26.7
34.9
44.4
55.0
66.6
79.4
3698
30
23.5
32.1
42.0
53.2
65.8
79.8
95.3
3096
35
27.2
37.4
48.9
62.1
76.8
93.3
111
2664
40
31.1
42.4
55.6
70.5
87.4
106
127
2350
45
34.9
47.5
62.4
80.4
98.2
119
143
2103
50
38.4
52.5
68.9
87.6
109
132
159
1908
55
42.1
57.5
75.5
96.1
119
146
175
1750
60
45.5
62.2
81.7
104
130
158
191
1619
5-4

5-5
FIGURE 5.2
DEFINITION OF DEPTH OF DRAW

5-6
FIGURE 5.3
EXAMPLES OF TAILOR WELDED BLANKS

5.3 Latest benckmark bumper beams
Examples of recent bumper beams are given in Table 5.3 and Figures
5.4 and 5.5. The examples clearly illustrate that steel bumper beams
readily meet the challenges faced by bumper designers -styling,
weight, cost and structural integrity.
5-7

FIGURE 5.4
ROLL FORMED BEAMS
A.) 2012 NISSAN JUKE (REAR)
M190 BOX SECTION
B.) 2012 HONDA CRV (FRONT)
M190 B-SECTION
C.) 2012 LINCOLN NAVIGATOR (FRONT)
120XF BOX SECTION
D.) 2013 FORD ESCAPE (REAR)
M190 BOX SECTION
5-8

FIGURE 5.5
STAMPED FACEBARS
E.) 2012 DODGE RAM 1500 (FRONT)
35XLF
F.) 2012 TOYOTA TUNDRA (REAR)
MILD STEEL
5-9

FIGURE 5.6
HOT-FORMED BEAMS
G.) 2012 FORD MUSTANG (FRONT)
1500 MPA BORON STEEL BOX SECTION
H.) 2012 JAGUAR XF (REAR)
1500 MPA BORON STEEL BOX SECTION
I.) 2012 FORD FOCUS (FRONT)
1500 MPA BORON STEEL HAT SECTION WITH FACE PLATE
J.) 2012 FORD ESCAPE (FRONT)
1500 MPA BORON STEEL HAT SECTION WITH FACE PLATE
5-10

FIGURE 5.7
SHEET HYDROFORMED FACEBAR
K.) 2010 FORD RAPTOR (FRONT)
MILD STEEL
5-11

TABLE 5.3
LATEST BENCHMARK BUMPER BEAMS
VEHICLE DESCRIPTION MASS PRODUCTION LOCATION MATERIAL THICKNESS FEATURES
(model year, make, model) METHOD (front or rear) (mm)
2012 Nissan Juke 3.3 kg Roll Forming Rear 190T / 1.1 mm Lightweight roll formed bumper with
1300MPa UHSS M190
2012 Honda CRV 5.8 kg Roll Forming Front 190T / 1.2 mm Variable radii roll formed UHSS B-section
1300MPa
2010 Ford Raptor Facebar = 9.7 kg Sheet Front Mild Steel 1.6 mm Industry first sheet hydroformed facebar
Assembly = 18.7 kg Hydroforming
2012 Dodge Ram 1500 28.2 kg Stamping Front 035XLF 1.8 mm The EA system is specially designed and tuned
to allow multiple front bumper modules
2012 Toyota Tundra 25.9 kg Stamping Rear Mild Steel 1.6 mm Full-size, deep-drawn bumper with lightweight
bracing
2012 Lincoln Navigator Beam = 2.6 kg Roll Forming Front 120XF 1.7 mm Low cost design with crash compatibility
2012 Ford Mustang 4.5 kg Roll/Hot Front MnB 1500 1.2 mm 1500 MPa boron steel with closed section,
Forming (ACCRA) aluminized coating, and variable sweep / section
2012 Jaguar XF 5.6 kg Roll/Hot Rear 22MnB5 1.2 mm 1500 MPa boron steel with closed section,
Forming (ACCRA) aluminized coating, and variable sweep / section
2012 Ford Focus (C346) 9.48 kg Hot Stamped Front 10B21MnB 1.8 mm Global design produced in North America,
Europe, Russia and China
2013 Ford Escape (C520) 10.47 kg Hot Stamped Front 10B21MnB 1.7 mm Carry over press parts from C346
2013 Ford Escape 7.4 kg Roll Forming Rear M190T 1.8 mm Lightweight, ultra high-strength steel bumper
solution
5-12

TABLE 5.3 (continued)
LATEST BENCHMARK BUMPER BEAMS
DEFINITIONS
XF
XLF
T
MPa
MnB
— High-strength low-alloy (HSLA). Designation number is yield strength in ksi.
— High-strength low-alloy (HSLA) with low carbon. Formability of this quality is superior to XF quality.
Designation number is yield strength in ksi.
— Martensitic quality.
— Mega Pascal.
— Manganese Boron
5-13

5.4 Bumper weights, materials and coatings
Beams produced by the roll forming production method are
shown in Table 5.4, beams produced by the cold stamping
method are shown in Table 5.5 and beams produced by the hot
forming method are shown in Table 5.6. This data may be used to
establish bumper beam benchmarks.
In Tables 5.4, 5.5 and 5.6, the bumper beams are grouped by
steel grade. The steel grades are defined in the Notes at the end
of each table (see also Tables 2.1 and 2.2). For any given steel
grade, the bumper beams are listed in decreasing order of steel
beam thickness. The vehicle make and model is given for each
beam.
There are five weight columns in Tables 5.4, 5.5 and 5.6. The first
column indicates the weight of the roll formed, cold stamped or
hot formed beam itself. For facebars, the weight is that of a
painted beam. Chrome facebars are 0.37 kg (1.0 pound) heavier.
The second column is the weight of any reinforcements welded to
the plain beam. The third column is the combined weight of the
plain beam and attached reinforcements. The fourth column
tabulates the weight of mounting brackets. The fifth column is the
weight of a plain bumper beam, its reinforcements and its
mounting brackets. It should be noted that many spaces in the
five weight columns are left blank. A blank space indicates that
the weight being tabulated is unavailable.
The steel products used to manufacture the bumper beams are
listed in Tables 5.4, 5.5 and 5.6. Note that both hot rolled (HR)
and cold rolled (CR) sheets are delivered in the bare condition.
For hot-dip galvanized (HDG) and electrogalvanized (EG) sheets,
the coating type and weight are shown. See Section 2.14 for a
description of aluminized (CR) sheet.
Corrosion protection coatings may be applied by the bumper
supplier or by the OEM on the assembly line. The corrosion
resistance of a bumper beam depends on all of the coatings
applied to it. Thus, the coatings applied by both the bumper
supplier and OEM are included in Tables 5.4, 5.5 and 5.6.
Sweep or curvature is often imparted to bumper beams during
roll forming. For the roll formed beams in Table 5.4, the amount of
sweep is shown. A small sweep radius indicates a large amount of
curvature to help achieve a high degree of styling.
5-14

TABLE 5.4
ROLL FORMED BUMPER BEAMS
2009 MODEL YEAR

STEEL THICKNESS
GRADE 1 [mm (inches)]
590R
3.20 (0.126)
80XLF
1.60 (0.063)
1.73 (0.068)
3.50 (0.138)
120XF
1.10 (0.043)
1.10 (0.043)
1.14 (0.045)
1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
1.20 (0.067)
1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
Honda
Ridgeline
rear
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
Total
Chev
Jeep
Chev
Pontiac
Saturn
Nissan
Ford
Chrysler
Chrylser
Chrysler
Chrysler
Dodge
Dodge
Dodge
Dodge
Tahoe
Wrangler
Tahoe
Solstice
Sky
Sentra
P150 Ranger
Sebring
Sebring Conv
300
300
Caliber
Caliber
Charger
Charger
front
front
rear
rear
rear
front
front
front
front
front
rear
front
rear
front
rear
7.79
(17.16)
6.20
(13.68)
7.40
(16.32)
5.85
(12.90)
5.85
(12.90)
5.74
(12.65)
2.70
(5.94)
5.71
(12.60)
5.71
(12.60)
6.71
(14.80)
6.75
(14.88)
4.99
(11.00)
6.03
(13.30)
6.71
(14.80)
6.75
(14.88)
1.88
(4.14)
4.58
(10.08)
15.20
(33.51)
2.44
(5.36)
2.55
(5.61)
2.55
(5.61)
2.9
(6.38)
7.79
(17.16)
6.20
(13.68)
22.60
(49.83)
5.85
(12.90)
5.85
(12.90)
5.74
(12.65)
7.02
(15.44)
8.26
(18.21)
8.26
(18.21)
6.71
(14.80)
6.75
(14.88)
7.89
(17.36)
6.03
(13.30)
6.71
(14.80)
6.75
(14.88)
STEEL
PRODUCT
HR
HR
CR
HR
CR
CR
CR
60G60G
CR
CR
CR
CR
CR
CR
CR
CR
TABLE 5.4
ROLL FORMED BUMPER BEAMS
2009 MODEL YEAR
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
SWEEP
NUMBER
SWEEP
RADIUS
mm (inches)
E-coat
none
E-coat
none
35
2673
(105)
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
none
none
none
none
none
none
none
28
36
36
39
42
40
40
43
28
40
40
43
28
3295
(10)
2628
(103)
2628
(103)
2400
(95)
2243
(88)
2350
(93)
2350
(93)
2200
(87)
3348
(132)
2348
(92)
2348
(92)
2200
(87)
3348
(132)
5-15

1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
1.30 (0.051)
1.40 (0.055)
1.40 (0.055)
STEEL THICKNESS
GRADE 1 [mm (inches)]
120XF
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
Jeep
Jeep
Jeep
Jeep
Buick
Chev
Chev
GMC
GMC
Saturn
Saturn
Saturn
Chev
Chev
Chev
Compass
Compass
Patriot
Patriot
Enclave
Malibu
Impala
Acadia
Acadia
Aura
Outlook
Outlook
Impala
Malibu
Camaro
front
rear
front
rear
rear
rear
rear
front
rear
rear
front
rear
front
front
front
4.99
(11.00)
6.03
(13.30)
5.23
(11.53)
6.03
(13.30)
6.56
(14.47)
5.53
(12.19)
6.31
(13.91)
4.63
(10.20)
6.56
(14.47)
5.53
(12.19)
4.63
(10.20)
6.56
(14.47)
6.84
(15.07)
6.19
(13.64)
6.74
(14.85)
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
2.17
(4.78)
1.15
(2.25)
2.17
(4.78)
1.15
(2.55)
2.17
(4.78)
8.73
(19.25)
5.78
(12.75)
8.73
(19.25)
5.78
(12.85)
8.73
(19.25)
5.46
(12.04)
6.53
(14.40)
7.11
(15.67)
2.44
(5.39)
2.42
(5.34)
5.81
(12.81)
7.11
(15.67)
2.44
(5.39)
5.81
(12.81)
7.11
(15.67)
0.25
(0.54)
1.20
(2.66)
Total
10.45
(23.04)
6.03
(13.30)
11.76
(25.93)
6.03
(13.30)
15.84
(34.92)
7.97
(17.58)
8.73
(19.25)
11.59
(25.56)
15.84
(34.92)
7.97
(17.58)
11.59
(25.66)
15.84
(34.92)
7.09
(15.61)
7.39
(16.30)
6.74
(14.85)
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
STEEL
PRODUCT
TABLE 5.4 (continued)
ROLL FORMED BUMPER BEAMS
2009 MODEL YEAR
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
SWEEP
NUMBER
SWEEP
RADIUS
[mm (inches)]
none
none
none
none
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
none
E-coat
40
40
40
40
49
34
37
36
49
34
59
49
36
27
27
2349
(93)
2349
(93)
2349
(93)
2348
(93)
1926
(76)
2743
(108)
2550
(100)
2624
(103)
1925
(76)
2743
(108)
1624
(64)
1926
(76)
2620
(103)
340
(136)
3441
(136)
5-16

STEEL THICKNESS
GRADE 1 [mm (inches)]
120XF
1.40 (0.055)
1.40 (0.055)
1.50 (0.059)
1.50 (0.059)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.70 (0.067)
1.73 (0.068)
1.80 (0.071)
1.80 (0.071)
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
Buick
Saturn
Chev
Enclave
Aura
Corvette
front
front
front
5.49
(12.11)
6.19
(13.64)
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
1.15
(2.55)
6.64
(14.66)
5.81
(12.81)
1.20
(2.66)
Chev
Corvette
rear
Chrysler
Chrysler
Dodge
Chev
Nissan
Subaru
Ford
Sebring
Sebring Conv
Challenger
Camaro
Sentra
Tribecca
Escape
rear
rear
rear
rear
rear
rear
front
7.76
(17.11)
7.26
(16.01)
9.77
(21.54)
8.07
(17.79)
7.61
(16.78)
6.29
(13.88)
1.88
(4.14)
9.95
(21.93)
3.87
(8.53)
Ford
Escape
rear
Ford
Subaru
Mitsubishi
Mitsubishi
U222
Navigator
Tribecca
Galant
Eclipse
front
front
front
front
6.92
(15.25)
7.39
(16.29)
6.60
(14.54)
6.60
(14.54)
0.36
(0.79)
Total
12.45
(27.47)
7.39
(16.30)
7.76
(17.11)
7.26
(16.01)
9.77
(21.54)
13.82
(30.46)
7.61
(16.78)
6.29
(13.88)
7.28
(16.04)
7.39
(16.29)
6.60
(14.54)
6.60
(14.54)
STEEL
PRODUCT
CR
CR
70G70G EG
70G70G EG
CR
CR
CR
CR
CR
CR
60G60G EG
60G60G EG
CR
CR
CR
CR
TABLE 5.4 (continued)
ROLL FORMED BUMPER BEAMS
2009 MODEL YEAR
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
SWEEP
NUMBER
SWEEP
RADIUS
[mm (inches)]
E-coat
E-coat
E-coat
E-coat
none
none
none
E-coat
none
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
none
none
none
none
none
59
27
0
0
46
46
28
57
38
25
28
48
44
35
26
26
1624
(64)
3441
(136)
0
(0)
0
(0)
2061
(81)
2061
(81)
3348
(132)
1689
(67)
2500
(98)
3659
(144)
3310
(130)
1981
(78)
2160
(85)
2710
(107)
3602
(142)
3602
(142)
5-17

STEEL THICKNESS
GRADE 1 [mm (inches)]
120XF
1.80 (0.071)
1.90 (0.075)
1.90 (0.075)
1.91 (0.075)
140T
1.20 (0.047)
1.40 (0.055)
1.50 (0.059)
1.50 (0.059)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.80 (0.071)
1.80 (0.071)
1.80 (0.071)
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
Mitsubishi
Ford
Lincoln
Ford
Mitsubishi
Eclipse Spyder
D258 Taurus
Town Car
Crown
Victoria
Endeavor
front
rear
rear
rear
front
6.60
(14.54)
6.60
(14.54)
10.26
(22.58)
10.26
(22.58)
5.65
(12.45)
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
3.66
(8.05)
Chev
Cobalt
front
Ford
MKS
rear
Ford
Taurus
rear
Toyota
Mitsubishi
Mitsubishi
MItsubishi
Solara
Galant
Eclipse
Endeavor
rear
rear
rear
rear
6.58
(14.50)
7.34
(16.19)
6.84
(15.08)
6.84
(15.08)
0.11
(0.24)
Honda
Accord
front
Honda
Honda
Accord
Crossover
Accord
front
rear
Total
6.60
(14.54)
11.57
(25.46)
10.26
(22.58)
10.26
(22.58)
5.65
(12.45)
6.69
(14.74)
7.34
(16.19)
6.84
(15.08)
6.84
(15.08)
STEEL
PRODUCT
CR
CR
60G60G EG
60G60G EG
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
TABLE 5.4 (continued)
ROLL FORMED BUMPER BEAMS
2009 MODEL YEAR
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
SWEEP
NUMBER
SWEEP
RADIUS
[mm (inches)]
E-coat
none
E-coat
E-coat
E-coat
E-coat
E-coat
none
none
none
26
37
18
18
26
3602
(142)
2530
(100)
5109
(201)
5109
(201)
3600
(142)
E-coat
none
E-coat
none
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
none
none
none
none
32
35
35
35
65
2908
(115)
2700
(106)
2700
(106)
2700
(106)
1509
(59)
E-coat
26
3558
(140)
5-18

STEEL THICKNESS
GRADE 1 [mm (inches)]
140T
1.80 (0.071)
2.00 (0.079)
2.00 (0.079)
2.00 (0.079)
2.00 (0.079)
M190HT
1.10 (0.043)
1.10 (0.043)
1.10 (0.043)
1.10 (0.043)
1.10 (0.043)
1.10 (0.043)
1.14 (0.045)
1.14 (0.045)
1.14 (0.045)
1.14 (0.045)
1.20 (0.047)
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
Honda
Honda
Acura
Accord
Crossover
Element
MDX
rear
rear
front
5.73
(12.64)
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
1.22
(2.68)
6.95
(15.32)
1.31
(2.88)
Acura
Honda
MDX
Crossover
Pilot
front
front
Chev
Pontiac
Nissan
Nissan
Nissan
Suzuki
Ford
Lincoln
Mercury
Suzuki
Ford
Equinox
Torrent
Altima
Altima Coupe
Maxima
XL-7
Fusion
MKZ
Milan
XL-7
Taurus
front
front
front
front
front
front
rear
rear
rear
rear
front
3.81
(8.40)
3.81
(8.40)
4.92
(10.85)
4.92
(10.85)
5.85
(12.90)
3.81
(8.40)
5.74
(12.65)
5.74
(12.65)
5.74
(12.65)
4.00
(8.82)
7.26
(15.97)
1.00
(2.21)
2.58
(5.68)
2.58
(5.68)
0.83
(1.84)
4.81
(10.61)
6.39
(14.08)
6.39
(14.08)
4.83
(10.66)
0.11
(0.24)
0.48
(1.06)
Total
8.26
(18.17)
4.81
(10.61)
6.39
(14.08)
4.92
(10.82)
5.03
(11.07)
5.85
(12.90)
6.39
(14.08)
5.74
(12.65)
5.74
(12.65)
5.74
(12.65)
4.83
(10.66)
7.74
(17.03)
STEEL
PRODUCT
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
30G30G
TABLE 5.4 (continued)
ROLL FORMED BUMPER BEAMS
2009 MODEL YEAR
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
SWEEP
NUMBER
SWEEP
RADIUS
[mm (inches)]
E-coat
none
E-coat
E-coat
none
42
2240
(88)
E-coat
none
E-coat
none
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
none
none
none
E-coat
none
E-coat
23
23
38
38
38
23
34
34
34
23
19
3994
(157)
3994
(157)
2500
(98)
2500
(98)
2500
(98)
3994
(157)
2740
(108)
2740
(108)
2740
(108)
4006
(158)
4843
(191)
5-19

STEEL THICKNESS
GRADE 1 [mm (inches)]
M190HT
1.20 (0.047)
1.20 (0.047)
1.30 (0.051)
1.30 (0.051)
1.30 (0.051)
1.33 (0.052)
1.33 (0.052)
1.40 (0.055)
1.40 (0.055)
1.40 (0.055)
1.40 (0.055)
1.40 (0.055)
1.40 (0.055)
1.40 (0.055)
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
Chev
Pontiac
Nissan
Nissan
Nissan
Dodge
Chrysler
Ford
Ford
Lincoln
Lincoln
Pontiac
Acura
Equinox
Torrent
Altima
Altima
Maxima
Caravan
Town &
Country
Flex
Edge
MKX
MKT
G8
MDX
rear
rear
rear
rear
rear
rear
rear
front
rear
rear
front
front
rear
4.79
(10.55)
4.79
(10.55)
6.22
(13.70)
6.22
(13.70)
6.22
(13.70)
8.14
(17.95)
8.14
(17.95)
2.79
(6.15)
5.13
(11.30)
5.13
(11.30)
2.79
(6.15)
5.78
(12.73)
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
1.00
(2.21)
0.83
(1.83)
0.31
(0.69)
3.90
(8.59)
3.90
(8.59)
5.79
(12.76)
5.62
(12.38)
6.53
(14.39)
6.69
(14.74)
6.69
(14.74)
3.59
(7.92)
3.59
(7.92)
3.59
(7.92)
1.22
(2.68)
Honda
Odyssey
rear
Total
5.79
(12.76)
5.62
(12.38)
9.81
(21.62)
9.81
(21.62)
10.12
(22.31)
8.14
(17.95)
8.14
(17.95)
6.69
(14.74)
6.35
(13.98)
5.13
(11.30)
6.69
(14.74)
5.78
(12.73)
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
STEEL
PRODUCT
TABLE 5.4 (continued)
ROLL FORMED BUMPER BEAMS
2009 MODEL YEAR
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
SWEEP
NUMBER
SWEEP
RADIUS
[mm (inches)]
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
none
none
none
none
23
23
23
23
23
37
37
41
27
27
41
12
4006
(158)
4006
(158)
4000
(158)
4000
(158)
4000
(158)
2543
(100)
2543
(100)
2325
(92)
3500
(138)
3500
(138)
2325
(92)
7934
(312)
E-coat
none
5-20

STEEL THICKNESS
GRADE 1 [mm (inches)]
M190HT
1.54 (0.061)
1.54 (0.061)
1.54 (0.061)
1.54 (0.061)
1.50 (0.059)
1.50 (0.059)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.80 (0.071)
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
Chrysler
Dodge
Honda
Honda
Ford
Lincoln
Town &
Country
Caravan
CR-V
CR-V
Crown
Victoria
Town Car
front
front
front
rear
front
front
7.72
(17.02)
7.72
(17.02)
3.34
(7.36)
3.41
(7.52)
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
0.94
(2.07)
2.29
(5.06)
4.28
(9.43)
5.70
(12.58)
3.23
(7.12)
3.23
(7.12)
1.09
(2.41)
1.77
(16.49)
Ford
Lincoln
Lincoln
Mercury
Chev
Fusion
MKZ
MKT
Milan
Cobalt
front
front
rear
front
rear
4.42
(9.74)
4.42
(9.74)
5.49
(12.11)
4.42
(9.74)
0.54
(1.18)
Chev
HHR
front
Chev
HHR
rear
Ford
Explorer
front
Honda
Ridgeline
front
5.40
(11.90)
4.69
(10.34)
Total
10.95
(24.14)
10.95
(24.14)
5.37
(11.84)
7.47
(16.49)
4.42
(9.74)
4.42
(9.74)
6.03
(13.29)
4.42
(9.74)
10.09
(22.24)
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
STEEL
PRODUCT
TABLE 5.4 (continued)
ROLL FORMED BUMPER BEAMS
2009 MODEL YEAR
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
SWEEP
NUMBER
SWEEP
RADIUS
[mm (inches)]
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
E-coat
none
none
none
44
44
38
27
30
30
27
27
18
27
2148
(85)
2148
(85)
2500
(98)
3400
(134)
3096
(122)
3096
(122)
3403
(134)
3403
(134)
5000
(197)
3403
(134)
E-coat
none
E-coat
none
E-coat
E-coat
none
42
43
1981
(78)
2181
(86)
5-21

TABLE 5.4 (continued)
ROLL FORMED BUMPER BEAMS
2009 MODEL YEAR
STEEL THICKNESS
GRADE 1 [mm (inches)]
M190HT
M220HT
1.80 (0.071)
1.45 (0.057)
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
Honda
Cadillac
Odyssey
CTS
front
front
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
Total
CR
CR
STEEL
PRODUCT
BUMPER SUPPLIER
COATING
E-coat
E-coat
ASSEMBLY
LINE
COATING
none
none
SWEEP
NUMBER
43
SWEEP
RADIUS
[mm (inches)]
2181
(86)
1.45 (0.057) Cadillac CTS
rear
CR
E-coat
none
1.70 (0.067)
Ford
MKS
rear 6.76
(14.88)
1.12
(2.46)
7.88
(17.34)
1.06
(2.34)
8.94
(19.68)
60G60G
none
E-coat
44
2148
(86)
NOTES:
1. A blank cell means that data is unavailable for that cell.
2. A zero (0) sweep number means the beam is straight/flat.
3. Sweep numbers are rounded to the nearest whole number. Sweep radii are actual radii.
DEFINITIONS:
590R Ferrite-bainite transformation strengthening grade. Minimum tensile strength is 590 MPa.
XF Recovery annealed quality. Strength is achieved primarily through cold work during cold rolling at the steel mill. Designation number (e.g. 50) is minimum yield
strength in ksi.
XLF Microalloy quality. Strength is obtained through small quantities of alloying elements such as vanadium and niobium. Designation number (e.g. 120) is
minimum yield strength in ksi.
T Dual phase quality. Structure contains martensite in ferrite matrix. Designation number (e.g. 140) is minimum tensile strength in ksi.
M..HT Martensitic quality. Strength is determined by carbon content. Designation number (e.g. 190) is minimum tensile strength in ksi.
CR Cold rolled sheet.
HR Hot rolled sheet.
EG Electrogalvanized sheet. The six-character descriptor designates coating type and weight. Two numeric characters (e.g. 60) denote coating weight in
g/m 2 . An alphabetic character denotes coating type. The first three characters denote coating weight and type on one side of the sheet and the last
three characters denote coating weight and type on the opposite side of the sheet.
G Hot-dip galvanized sheet. The six-character descriptor designates coating type and weight. Two numeric characters (e.g. 90) denote coating weight in
g/m 2 . An alphabetic character denotes coating type. The first three characters denote coating weight and type on one side of the sheet and the last
three characters denote coating weight and type on the opposite side of the sheet.
5-22

TABLE 5.5
STAMPED FACEBARS
2009 MODEL YEAR

STEEL THICKNESS
GRADE 1 [mm (inches)]
1008/
1010
1.40 (0.055)
1.60 (0.063)
1.60 (0.063)
1.60 (0.063)
1.80 (0.071)
1.80 (0.071)
1.80 (0.071)
1.80 (0.071)
1.80 (0.071)
1.90 (0.071)
2.00 (0.079)
2.00 (0.079)
2.00 (0.079)
2.01 (0.079)
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
Toyota
Toyota
Toyota
Nissan
Dodge
Mitsubishi
Nissan
Nissan
Nissan
Nissan
GM
Tundra
Tundra
Tacoma
Frontier
Dakota
Raider
Frontier
Titan
Xterra
Titan
Hummer 3
front
rear
rear
front
rear
rear
rear
front
rear
rear
rear
10.59
(23.33)
10.28
(22.65)
8.53
(18.80)
9.11
(20.08)
9.66
(21.30)
9.66
(21.30)
8.26
(18.20)
14.56
(32.08)
6.94
(15.30)
10.93
(24.09)
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
Ford
Mazda
Ford
Ranger
B-series
Econoline
(Step)
rear
rear
rear
7.12
(15.7)
7.12
(15.7)
13.42
(29.6)
4.17
(10.4)
4.17
(10.4)
5.42
(11.95)
11.29
(26.1)
11.29
(26.1)
18.84
(41.55)
6.35
(14.0)
Total
10.59
(23.33)
10.28
(22.65)
8.53
(18.80)
9.11
(20.08)
9.66
(21.30)
9.66
(21.30)
8.26
(18.20)
14.56
(32.08)
6.94
(15.30)
10.93
(24.09)
11.29
(26.1)
11.29
(26.1)
25.17
(55.5)
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
STEEL
PRODUCT
TABLE 5.5
STAMPED FACEBARS
2009 MODEL YEAR
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
DEPTH
OF DRAW
[mm (inches)]
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - paint
back side - none
none
none
none
none
none
none
none
none
none
none
none
front side - chrome or paint
back side - paint
none
front side - chrome or paint
back side - paint
none
front side - chrome or paint
back side - paint
none
5-23

STEEL THICKNESS
GRADE 1 [mm (inches)]
1008/
1010
2.29 (0.090)
2.29 (0.090)
2.29 (0.090)
2.29 (0.090)
2.30 (0.090)
2.50 (0.098)
DR210
1.80 (0.071)
1.80 (0.071)
1.80 (0.071)
BH210
1.60 (0.063)
35SLK
1.90 (0.075)
1.90 (0.075)
35XLF
1.64 (0.065)
1.80 (0.071)
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
Chev
Chev
Chev
GMC
Ford
GM
Tahoe
Suburban
Silverado
Sierra 400
Econoline
Hummer 3
rear
rear
rear
rear
rear
front
21.19
(46.71)
21.19
(46.71)
21.19
(46.71)
21.19
(46.71)
13.15
(29.0)
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
13.15
(29.0)
1.77
(3.9)
Ford
Ford
Ford
Chev
Super Duty
Super Duty
Econoline
Silverado
front
rear
front
front
17.05
(37.59)
8.44
(18.60)
14.43
(31.81)
GMC
Chev
Dodge
Dodge
Canyon
Colorado
Ram 1500
Ram HD
rear
rear
rear
rear
20.23
(44.60)
20.23
(44.60)
9.54
(20.99)
13.28
(29.29)
13.28
(29.29)
9.55
(21.06)
Total
21.19
(46.71)
21.19
(46.71)
21.19
(46.71)
21.19
(46.71)
14.92
(32.9)
17.05
(37.59)
8.44
(18.60)
14.43
(31.81)
20.23
(44.60)
20.23
(44.60)
9.54
(20.99)
22.83
(50.35)
HR
HR
HR
HR
CR
CR
CR
CR
CR
CR
CR
CR
CR
CR
STEEL
PRODUCT
TABLE 5.5 (continued)
STAMPED FACEBARS
2009 MODEL YEAR
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
DEPTH
OF DRAW
[mm (inches)]
front side - chrome or paint
back side - none
front side - chrome
back side - none
front side - chrome or paint
back side - none
front side - chrome or paint
back side - none
front side - chrome or paint
back side - paint
none
none
none
none
none
135
(5.3)
135
(5.3)
135
(5.3)
135
(5.3)
front side - paint
back side - none
none
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - acrylic compound
none
none
none
none
front side - chrome or paint
back side - acrylic compound
front side - chrome or paint
back side - acrylic compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - paint
none
none
none
none
165
(6.5)
165
(6.5)
92
(3.6)
5-24

STEEL THICKNESS
GRADE 1 [mm (inches)]
35XLF
1.80 (0.071)
1.80 (0.071)
1.80 (0.071)
1.80 (0.071)
1.91 (0.075)
1.91 (0.075)
1.91 (0.075)
2.01 (0.079)
2.01 (0.079)
50XLF
1.80 (0.071)
1.91 (0.075)
1.91 (0.075)
1.91 (0.075)
2.00 (0.079)
2.00 (0.079)
2.00 (0.079)
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
Chev
GMC
Dodge
Dodge
Chev
Silverado
Sierra
Ram 1500
Ram HD
Colorado
rear
rear
front
front
front
7.42
(16.35)
7.42
(16.35)
13.91
(30.66)
15.30
(33.71)
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
Mazda
Ford
Chev
GMC
Dodge
Ford
Ford
Ford
GMC
Chev
GMC
B Series Pickup
Ranger
Express 600
Savana 600
Ram 2DR
F-150
F-150 Styleside
(5000 lb. tow)
F-150 Styleside
(10500 lb. tow)
Sierra
Express
Savana
front
front
rear
rear
front
front
rear
rear
front
front
front
7.26
(16.00)
7.26
(16.00)
10.94
(24.12)
10.94
(24.12)
17.24
(38.00)
13.51
(29.8)
6.44
(14.2)
6.44
(14.2)
9.61
(21.18)
16.32
(35.96)
16.32
(35.96)
3.57
(7.86)
3.57
(7.86)
1.97
(4.36)
8.97
(19.79)
9.90
(21.83)
10.83
(23.86)
10.83
(23.86)
15.49
(34.16)
15.41
(33.99)
16.34
(36.03)
1.19
(2.62)
1.19
(2.62)
6.38
(14.07)
6.38
(14.07)
5.67
(12.50)
5.8
(12.8)
4.55
(10.04)
5.87
(12.96)
Total
7.42
(16.35)
7.42
(16.35)
13.91
(30.66)
15.30
(33.71)
12.01
(26.48)
12.01
(26.48)
17.32
(38.2)
17.32
(38.2)
22.91
(50.5)
27.09
(59.60)
19.97
(44.03)
22.21
(48.99)
9.61
(21.18)
16.32
(35.96)
16.32
(35.96)
CR
CR
CR
CR
CR
CR
CR
HR
HR
CR
CR
CR
CR
CR
CR
CR
STEEL
PRODUCT
TABLE 5.5 (continued)
STAMPED FACEBARS
2009 MODEL YEAR
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
DEPTH
OF DRAW
[mm (inches)]
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - acrylic compound
front side - chrome or paint
back side - paint
front side - chrome or paint
back side - paint or E-coat
front side - chrome or paint
back side - none
front side - chrome or paint
back side - none
front side - chrome or paint
back side - acrylic compound
front side - chrome or paint
back side - paint
front side - chrome or paint
back side - paint
front side - chrome or paint
back side - paint
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
none
none
none
none
none
none
none
none
none
none
none
none
none
none
none
none
140
(5.5)
117
(4.6)
117
(4.6)
132
(5.2)
132
(5.2)
191
(7.5)
140
(5.5)
160
(6.3)
160
(6.3)
5-25

TABLE 5.5 (continued)
STAMPED FACEBARS
2009 MODEL YEAR
STEEL THICKNESS
GRADE 1 [mm (inches)]
50XLF
55XLF
80XLF
2.00 (0.079)
2.00 (0.079)
2.00 (0.079)
2.26 (0.089)
2.26 (0.089)
2.26 (0.089)
2.26 (0.089)
2.26 (0.089)
2.26 (0.089)
1.32 (0.050)
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
Dodge
Dodge
Dodge
Chev
Chev
Chev
GMC
Chev
GMC
Honda
Ram
Ram 1500
Ram HD
Suburban
Suburban 430
Tahoe
Yukon
Silverado
Sierra HD
Element
front
front
front
front
front
front
front
front
front
front
13.28
(29.29)
13.91
(30.66)
15.30
(33.71)
15.30
(33.71)
14.29
(31.50)
14.29
(31.50)
14.29
(31.50)
14.29
(31.50)
14.29
(31.50)
14.29
(31.50)
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
13.28
(29.29)
9.55
(21.06)
Total
22.84
(50.35)
13.91
(30.66)
15.30
(33.71)
15.30
(33.71)
14.29
(31.50)
14.29
(31.50)
14.29
(31.50)
14.29
(31.50)
14.29
(31.50)
14.29
(31.50)
CR
CR
CR
HR
HR
HR
HR
HR
HR
STEEL
PRODUCT
BUMPER SUPPLIER
COATING
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome or paint
back side - paint
front side - chrome or paint
back side - thermplastics, water
based compound
front side - chrome or paint
back side - thermoplastics, water
based compound
front side - chrome
back side - none
front side - chrome
back side - none
front side - chrome or paint
back side - none
front side - chrome or paint
back side - none
front side - chrome or paint
back side - none
front side - chrome or paint
back side - none
ASSEMBLY
LINE
COATING
none
none
none
none
none
none
none
none
none
none
DEPTH
OF DRAW
[mm (inches)]
127
(5.0)
127
(5.0)
127
(5.0)
127
(5.0)
127
(5.0)
127
(5.0)
NOTES:
1. A blank cell means that data are unavailable for that cell.
2. Beam weight is for a painted beam. Add 0.37 kg (1.0 pound) for a chrome beam.
DEFINITIONS
1008/1010 — Low carbon quality. Mechanical properties are not certified.
DR210 — Dent resistant quality. Minimum yield strength of 210MPa (30 ksi) as-shipped from the steel mill. Strength increases due to work hardening during forming.
BH 210 — Bake hardenable quality. Minimum yield strength of steel is 210 MPa (30 ksi) as-shipped from the steel mill. Strength increases due to work hardening during
forming and baking during coating.
SLK — Structural quality. Killed, fine grain practice. Designation numbr (e.g. 35) is minimum yield strength in ksi.
XLF — Microalloy quality. Strength is obtained through small additions of alloying elements such as vanadium and niobium. Designation number (e.g. 50) is minimum
yield strength in ksi.
CR — Cold rolled sheet.
HR — Hot rolled sheet.
5-26

TABLE 5.6
HOT FORMED BUMPER BEAMS
2009 MODEL YEAR

6.00
(13.23)
7.20
(15.87)
8.00
(17.64)
5.00
(11.03)
5.00
(11.03)
5.00
(11.03)
4.00
(8.82)
4.00
(8.82)
6.00
(13.23)
11.6
(25.52)
STEEL THICKNESS
GRADE 1 [mm (inches)]
10B21(M)
4.0 (0.157)
3.50 (0.138)
3.00 (0.118)
2.75 (0.108)
2.70 (0.108)
2.70 (0.106)
2.50 (0.098)
2.50 (0.098)
2.50 (0.098)
2.50 (0.098)
2.35 (0.093)
2.14 (0.084)
2.14 (0.084)
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
BMW
6 Series
rear
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
Total
VW
VW
SEAT
A4 Jetta USA
C1 USA
New Beetle
Ibiza
rear
rear
rear
6.00
(13.23)
VW
VW
VW
VW
Seat
VW
VW
VW
VW
B5 USA Passat
B5 USA Passat
PQ24 Brazil
New Polo
PQ24 A04
New Polo
PQ24 S04
New Ibiza
Tiguan
Scirocco
Golf
Jetta
front
rear
rear
rear
rear
front
front
rear
front
6.50
(14.33)
8.00
(17.64)
2.00
(4.41)
2.80
(6.17)
2.80
(6.17)
4.00
(8.82)
4.20
(9.26)
3.50
(7.72)
6.00
(13.23)
3.1
(6.82)
0.70
(1.54)
3.00
(6.61)
2.20
(4.85)
2.20
(4.85)
2.50
(5.51)
HR
HR
HR
HR
HR
HR
HR
HR
HR
STEEL
PRODUCT
TABLE 5.6
HOT FORMED BUMPER BEAMS
2009 MODEL YEAR
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
DEPTH
OF DRAW
[mm (inches)]
E-coat
none
65 (2.6)
E-coat
none
80 (3.1)
E-coat
none
82 (3.2)
E-coat
none
105 (4.1)
E-coat
none
70 (2.8)
E-coat
none
70 (2.8)
E-coat
none
70 (2.8)
E-coat
yes
50 (2.0)
E-coat
yes
60 (2.4)
E-coat
none
65 (2.6)
E-coat
none
65 (2.6)
5-27

STEEL THICKNESS
GRADE 1 [mm (inches)]
10B21
2.14 (0.084)
2.00 (0.079)
2.00 (0.079)
1.80 (0.071)
1.80 (0.071)
1.80 (0.071)
1.80 (0.071)
1.80 (0.071)
1.80 (0.071)
1.75 (0.069)
1.60 (0.063)
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
VW/
Skoda
Opel
Smart
VW
Saab
Saab
VW-
China
VW-
Seat
VW
VW
VW
T5 New 307
Zafira
Pure Coupe
SE241
New Cordoba
602 New 9-5
440 New 9-3
X4 (X41, X42)
New Xantia
W456 Brasil
former (SUV)
C1 USA New
Beetle
C1 ECE New
Beetle
D1 (Phaeton)
rear
rear
rear
front
front
front
front
rear
front
front
front
3.30
(7.28)
4.30
(9.48)
4.09
(9.02)
2.00
(4.41)
2.80
(6.17)
2.80
(6.17)
2.80
(6.17)
2.80
(6.17)
3.60
(7.94)
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
1.80
(3.97)
0.50
(1.10)
3.13
(11.62)
3.00
(6.61)
2.20
(4.85)
2.20
(4.85)
2.20
(4.85)
3.20
(7.05)
6.60
(14.55)
Total
5.10
(11.24)
4.80
(10.58)
7.22
(15.92)
5.00
(11.03)
5.00
(11.03)
5.00
(11.03)
5.00
(11.03)
6.00
(13.23)
4.97
(10.96)
10.20
(22.49)
HR
HR
HR
HR
HR
HR
HR
HR
HR
STEEL
PRODUCT
TABLE 5.6 (continued)
HOT FORMED BUMPER BEAMS
2009 MODEL YEAR
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
DEPTH
OF DRAW
[mm (inches)]
E-coat
none
E-coat
none
85 (3.3)
Zinc coated
none
40 (1.6)
E-coat
none
60 (2.4)
E-coat
none
60 (2.4)
E-coat
yes
60 (2.4)
E-coat
yes
60 (2.4)
E-coat
none
75 (3.0)
raw/CB-Zinc
yes
85 (3.3)
5-28

STEEL THICKNESS
GRADE 1 [mm (inches)]
10B21
1.50 (0.059)
1.50 (0.059)
1.50 (0.059)
1.50 (0.059)
1.25 (0.049)
1.20 (0.047)
1.20 (0.047)
1.20 (0.047)
1.20 (0/047)
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
VW
Ford
BMW
W456 Brasil
former (SUV)
Mondeo
5 Series
front
front
rear
2.10
(4.63)
2.85
(6.28)
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
7.20
(15.88)
Chrysler
A-Class
rear
VW
Polo A05
rear
Toyota
Toyota
Ford
Auris
Verso
Mustang
rear
rear
front
1.82
(4.01)
1.8
(3.96)
2.0
(4.4)
2.0
(4.4)
Ford
Mustang
rear
VW
BMW
D1 (Phaeton)
3 Series
rear
front
4.15
(9.15)
3.00
(6.61)
BMW
MINI
front
BMW
MINI
rear
BMW
BMW
MINI
Countryman
X5
front
front
Total
10.05
(22.16)
10.33
(22.77)
3.6
(7.92)
5.47
(11.90)
3.12
(6.88)
3.82
(8.41)
3.80
(8.36)
4.3
(9.46)
4.2
(9.24)
7.15
(15.76)
4.95
(10.91)
5.5
(12.13)
6.1
(13.42)
8.9
(19.58)
8.1
(17.82)
HR
HR
HR
HR
STEEL
PRODUCT
TABLE 5.6 (continued)
HOT FORMED BUMPER BEAMS
2009 MODEL YEAR
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
DEPTH
OF DRAW
[mm (inches)]
Zinc coated
none
E-coat
yes
27 (1.1)
E-coat
none
80 (3.1)
E-coat
none
80 (3.1)
E-coat
70 (2.8)
none
5-29

STEEL THICKNESS
GRADE 1 [mm (inches)]
10B21
1.8mm
2.0mm
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
BMW
X5
rear
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
Chrysler
E-class
rear
Ford
Fiesta
front
Ford
Fiesta
rear
Ford
Focus C-Max
front
Ford
Focus C-Max
rear
Ford
S-Max/Galaxy
front
Ford
S-Max/Galaxy
rear
Ford
Mondero
rear
PSA
Peugeot 3-7
rear
Saab
9-3
front
Saab
9-3 Convert
front
Saab
9-5
front
SEAT
Ibiza
front
SEAT
Leon
front
SEAT
Leon
rear
Total
5.5
(12.1)
8.93
(19.69)
8.6
(18.92)
3.3
(7.26)
10.0
(22.0)
4.53
(10.0)
10.0
(22.05)
5.00
(11.03)
5.00
(11.03)
10.4
(22.88)
5.00
(11.03)
6.00
(13.23)
4.97
(10.96)
10.20
(22.49)
10.20
(22.49)
7.,27
(16.03)
STEEL
PRODUCT
TABLE 5.6 (continued)
HOT FORMED BUMPER BEAMS
2009 MODEL YEAR
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
DEPTH
OF DRAW
[mm (inches)]
5-30

TABLE 5.6 (continued)
HOT FORMED BUMPER BEAMS
2009 MODEL YEAR
STEEL THICKNESS
GRADE 1 [mm (inches)]
10B21
MAKE MODEL FRONT OR
REAR
BUMPER Beam Performance
SEAT
Altea
front
WEIGHT [kg (pounds)]
Reinforcements Subtotal Mounting
Brackets
Total
STEEL
PRODUCT
BUMPER SUPPLIER
COATING
ASSEMBLY
LINE
COATING
DEPTH
OF DRAW
[mm (inches)]
SEAT
Altea
rear
AUDI
A3
rear
VOLVO
VOLVO
MERCEDES
VW
VW
Mazda
Mazda
VW
XC60
S60
GL
SLW Caddy
Touran
Mazda 6
Mazda 6
Russland
rear
rear
rear
front
front
front
rear
front
5.1
(11.22)
6.0
(13.2)
5.68
(12.5)
3.84
(8.4)
7.1
(15.62)
2.6
(5.72)
5.4
(11.88)
FIAT
FIAT
FIAT 500
FIAT 500
front
rear
4.5
(9.9)
3.9
(8.58)
NOTES:
1. A blank cell means that data are unavailable for that cell.
DEFINITIONS
10B21 — Carbon-Boron quality (SAE 10B21 modified). Beams are hot formed. After quenching, the yield strength is about 1140 MPa (165ksi).
5-31

5.5 Current steel bumper design - passenger cars
A flow chart for designing passenger car bumpers is shown in
Figure 5.8. There are two paths. One path is for vehicles sold only
in North America and the other path is for vehicles sold in both
North America and Europe.
Two types of standards influence bumper design: mandatory
government standards and voluntary insurance industry standards.
In the United States, the federal standard regulating bumper
design is referred to as the National Highway Traffic Safety
Administration standard (see Section 6.1). The federal standard
that regulates bumper design in Canada (see Section 6.2) allows
the use of the NHTSA standard. Thus, the NHTSA standard covers
vehicles to be sold in both Canada and the United States.
In Europe, the Economic Commissions for Europe standard (see
Section 6.3), which is similar to the NHTSA standard, regulates
bumper design. In addition, front bumpers must conform to
Pedestrian Protection regulations (see Section 5.8).
The Insurance Institute for Highway Safety (IIHS) in an effort to
reduce the cost of passenger vehicle bumper repairs, has developed
a test standard that simulates a broader range of impacts occurring
in actual on-the-road crashes (see Section 6.4). The voluntary IIHS
tests are more severe than the NHTSA tests. The IIHS standard
provides a weighted damage estimate that is used when determining
overall rating for a vehicle to be sold in North America. This target
is used when designing the vehicle’s bumpers.
Similar to IIHS, the European insurance industry publishes two
voluntary tests to prevent unnecessary damage in low speed
crashes. These tests are referred to as the RCAR Structural Test
(see Section 6.6) and the RCAR Bumper Test (see Section 6.7).
5.5.1 Typical bumper design - North American passenger cars
In Figure 5.8, the designer’s first step is to determine the OEM
Internal design requirements. For example, are the IIHS tests to
be included in the design process Are there OEM requirements,
such as packaging, that are not included in the flow chart If the
answer to the latter question is yes, the designer must modify the
flow chart.
If there are no IIHS requirements, the designer moves directly to
a NHTSA Base Design. Thus, it is suggested the corner impact
be used to establish the base design. The designer then moves
on to the longitudinal pendulum and barrier impacts. If the
NHTSA damage and A+B planes force criteria have been
satisfied, a final design has been reached.
If the OEM has specified IIHS requirements, it is suggested the
designer start by satisfying the OEM IIHS requirements. Usually,
these requirements are more demanding than the NHTSA
criteria, especially if the IIHS target is a zero or minimal damage
estimate.
5-32

The designer may be designing a front bumper, a rear bumper or
both bumpers. If only a front or rear bumper is being designed,
the designer must establish the IIHS damage estimate desired by
the OEM for the bumper. If both a front and rear bumper are
being designed, the designer must establish the desired IIHS
weighted damage estimate. In the flow chart, the only difference
between the “front or rear” and the “front and rear” paths is the
acceptance criterion. The criterion for a single bumper is the damage
estimate for that bumper. The criterion if both bumpers are being
designed is the weighted damage estimate, which is calculated
using the damage estimate for each of the two bumpers.
Once an acceptable IIHS design has been achieved, the designer
verifies that the NHTSA criteria have been met before reaching a
final design.
5.5.2 Typical bumper design - North American and Europe passenger cars
In Figure 5.8, the designer’s first step is to determine the OEM
internal design requirements. For example, are the IIHS and RCAR
tests to be included in the design process Are there OEM
requirements, such as packaging, that are not included in the flow
chart If the answer to the latter question is yes, the designer must
modify the flow chart.
In general, the NHTSA and ECE requirements are similar as are the
IIHS and RCAR Bumper Test Requirements. However, the
requirements associated with the RCAR Structural Test are more
demanding than the NHTSA, ECE and RCAR Bumper Test
requirements. For this reason, plus the fact a European front
bumper must have pedestrian protection, the flow chart goes
through the European path before the North American path.
A European front bumper must meet Pedestrian Protection
requirements. Thus, a design concept that will provide the
required Pedestrian Protection must be selected and it is logical to
commence the design process here for a front bumper. After
preparing a Base Design that satisfies Pedestrian Protection
requirements, and if there are no RCAR requirements, the designer
addresses the ECE requirements. Often, the pendulum corner
impact is the most demanding ECE case. Thus, it is suggested the
corner impact be used first to verify the Base Design. After the
designer has satisfied the ECE requirements, the designer would
proceed through the North American bumper path as outlined in
Section 5.5.1 to reach a Final Design.
For a front bumper, if RCAR requirements are to be met, it is
suggested the RCAR requirements be addressed before the ECE
requirements because the RCAR requirements are more
demanding. The RCAR Structural Test is more demanding than the
RCAR Bumper Test. Thus, if the RCAR Structural Test is a
requirement, it should be addressed before the RCAR Bumper Test.
Once a design that is acceptable from the RCAR point of view has
been achieved, the designer moves through the ECE requirements
and then the North American bumper path as outlined in Section
5.5.1 to reach a Final Design.
5-33

A rear bumper would essentially follow the same path as a front
bumper. However, one major difference is that Pedestrian
Protection is not a requirement and this step in the design process
is bypassed.
5.6 Current steel bumper design - pickups, full size vans and sport utilities
There are no federal regulations in the United States or Canada
for bumpers on pickups, full size vans or SUVs. These bumpers
are designed to meet OEM internal specifications. Thus, a designer
should develop a design flow chart using Figure 5.8 as a model.
5-34

NO
DETERMINE OEM
INTERNAL DESIGN
REQUIREMENTS
N. AMERICA
OR
N. AMERICA
& EUROPE
YES
IIHS
REQUIREMENTS
N.A.
NO
FRONT OR REAR
OR
FRONT & REAR
FRONT OR REAR FRONT & REAR
ESTABLISH DESIRED
IIHS
DAMAGE ESTIMATE
ESTABLISH DESIRED
IIHS WEIGHTED
DAMAGE ESTIMATE
FRONT OR REAR
BASE DESIGN
•IIHS 10km/h OVERLAP
•IIHS 5km/h CORNER
FRONT
BASE DESIGN
•IIHS 10km/h OVERLAP
•IIHS 5km/h CORNER
ACCEPTABLE
DAMAGE
ESTIMATE
REAR
BASE DESIGN
•IIHS 10km/h OVERLAP
•IIHS 5km/h CORNER
YES
N.A. &
EUROPE
FRONT
OR
REAR
REAR
YES
YES
ACCEPTABLE
WEIGHTED
DAMAGE
ESTIMATE
NO
PEDESTRIAN
PROTECTION
BASE DESIGN
NHTSA
BASE DESIGN
PENDULUM –
• 2.5 mph LONG
• 1.5 mph CORNER
BARRIER –
• 2.5 mph
NON-BUMPER
VISUAL OR SAFETY
8 FUNCTIONAL ITEM
DAMAGE
NO
2000 lbs. <
A + B PLANES
FORCE
NO
NO
ACCEPTABLE
YES
RCAR
REQUIREMENTS
NO
YES
ESTABLISH
DESIRED
DAMAGEABILITY &
REPAIRABILITY
REQUIREMENTS
BASE DESIGN
STRUCTURAL TEST –
• 15 km/h FRONT
•15 km/h REAR
BUMPER TEST –
• 10 km/h FRONT
• 10km/h REAR
ACCEPTABLE
NO DAMAGEABILITY YES
& REPAIRABILITY
REQUIREMENTS
FINAL DESIGN
FIGURE 5.8 5.6
TYPICAL BUMPER
DESIGN FOR
PASSENGER CARS
AND MINIVANS
ECE
BASE DESIGN
• 2.5 mph LONG
• 1.5 mph CORNER
YES
NON-BUMPER
SAFETY &
FUNCTIONAL
DAMAGE
NO
5-35 5-37

5.7 Auto/Steel Partnership high speed bumper design - North American passenger cars
The Auto/Steel Partnership (A/SP) commissioned Quantech
Global Services to conduct a study on the front-end of a four-door,
mid-size sedan. The objective was to reduce the cost and mass of
the front end structure through the use of advanced high-strength
steels. The study included the development of a high speed
bumper system.
Current North American passenger cars have low speed bumper
systems. Thus, Quantech’s first task for the high speed bumper
system was to establish design criteria and a design process.
Sections 5.7.1 and 5.7.2 outline the results of Quantech’s research
into these two areas.
5.7.1 Quantech design criteria for high speed steel bumper system
Quantech, in consultation with A/SP, established the design
criteria for a high speed bumper system as:
1. No bumper damage or yielding after a 5mph (8km/h)
frontal impact into a flat, rigid barrier. Note: This
criterion does not apply to low speed bumpers, where
controlled yielding and deformation are beneficial.
2. No intrusion by the bumper system rearward of the
engine compartment rails for all impact speeds less than
9mph (15km/h).
3. Minimize the lateral loads during impacts in order to
reduce the possibility of lateral buckling of the rails.
4. Full collapse of the system during Danner (RCAR),
NCAP, and IIHS high speed crash without inducing
buckling of the rails.
5. Absorb 1% of the total energy every millisecond.
6. Absorb 15% of the total energy in the NCAP crash,
including engine hit.
7. Use the front-end crush space efficiently.
8. Meet the air bag sensor requirements in low, medium
and high speed impacts.
9. No detrimental affect on baseline body-in-white static or
dynamic stiffness.
Bumpers should protect car bodies from damage in low
speed collisions - the kind that frequently occurs in congested
urban traffic. The IIHS Low Speed Crash Test Protocol (see
Section 6.4) addresses this issue. For marketing reasons,
many current bumper systems are designed to ensure no or
minimal “cost of repair” after the IIHS 5mph (8km/h) barrier
impact. A/SP believes all future vehicles should meet this
requirement. Thus, Criterion 1 was set to achieve zero
damage and no or minimal “cost of repair” after the IIHS
5mph (8km/h) barrier impact.
Criterion 4 addresses three high speed load cases:
1. 40%-9mph Danner (RCAR Test - see Section 6.6 and
Reference 6.10). This load is a 9mph (15km/h) impact at
a 40% offset into a rigid barrier. The A/SP objective is
to have no damage to the radiator and other costly
equipment in the front-end and to have no damage to
the rail beyond 300mm (12inches).
5-36

5.7.2 Flow Chart for high speed system
2. 35 mph NCAP (NHTSA New Car Assessment Program,
Reference 5.2). This load is a 35mph (56km/h) impact
into a rigid barrier. The A/SP objective is to maximize
the energy absorbed in the bumper system.
3. 40%-40mph IIHS (Reference 5.3). This load case is a
40mph (64km/h) impact at a 40% offset into a
deformable barrier. The A/SP objective is to ensure the
bumper system does not break and is capable of
transferring the load to the right rail, thereby minimizing
the damage.
A major objective of A/SP is to reduce vehicle weight using
steel as the material of choice. Criterion 6 addresses this
objective. Traditional bumper systems absorb about 8-11% of
the energy in the 35mph (56km/h) NCAP crash. If bumper
systems were to dissipate higher levels, there would be an
opportunity for mass savings in the front end structure. To
capitalize on this opportunity, A/SP set 15% energy absorption
as a stretch goal for future bumper systems.
For the reason of low cost with lightweight, steel is the material
of choice for future, as well as current, bumper beams. The
flow chart in Figure 5.8 outlines the design process developed
by Quantech for a high speed bumper system having a steel
beam. The process is a logical route to satisfying the design
criteria outlined in Section 5.7.1.
First, a base design is prepared. It is checked against the IIHS
low speed [5mph (8km/h)] flat frontal barrier load case. If
there is damage or yielding, the base design is modified. If
not, the three high speed load cases are analyzed in the following
sequence:
1. 40% offset - 9mph (15km/h) Danner.
2. 35mph (56km/h) NCAP.
3. 40% offset - 40mph (64km/h) IIHS.
The results from the analyses of the three high speed load
cases are compared to the design criteria in Section 5.7.1. If
all of the criteria are met, the designer assesses the amount of
energy absorption. Energy absorption should be maximized
because the higher the amount, the greater the opportunity
to reduce mass in the front end structure. If the designer
believes energy absorption has been maximized, a viable
design has been captured. If not, the learning from the three
high speed load cases is used to improve the base design and
reach a viable design.
Usually, three or four viable design alternatives are developed
using the above process. The designer then selects one of
the alternatives as the Preferred Design. The Preferred
Design should be lightweight and easy to manufacture. Also,
it should be easy to assemble and integrate with the rails.
Cost is also a consideration when selecting the Preferred
Design.
5-37

FIGURE 5.9
AUTO/STEEL PARTNERSHIP BUMPER DESIGN FOR HIGH SPEED SYSTEM
NORTH AMERICAN PASSENGER CARS
AIR BAG SENSOR
REQUIREMENTS
BASE DESIGN
AIR BAG G
LOW SPEED
5 mph
DANNER
40% OFFSET
15 km/h (9 mph)
HIGH SPEED
35 mph (NCAP)
40%-40 mph (IIHS)
NO
ACCEPTABLE
NO/MINIMUM
DAMAGEABILITY
OF RAIL
ENERGY
ABSORPTION
MAXIMIZED
YES
CAPTURE A
VIABLE DESIGN
YES
NO
USE LEARNING
FOR AN IMPROVED
DESIGN
PREFERRED
DESIGN
Source: Auto/Steel Partnership and Quantech Global Services
5-38

5.8 Bumper design for pedestrian impact
Pedestrian safety is a globally recognized safety concern. Efforts
towards modifying vehicle designs to offer some protection for
pedestrians began in earnest in the 1970s. At the same time, test
procedures to evaluate the performance of new designs
developed. Pedestrian safety has improved significantly since
then.
The Steel Market Development Institute wished to learn how
pedestrian safety might affect steel bumper systems. Thus, it
retained Dr. Peter Schuster, California Polytechnic State University,
to study this topic. The following information is based on his work
(Reference 5.4).
5.8.1 Impact tests
The European Union has been subjecting select vehicles to a
battery of tests (frontal, side and pedestrian) as part of its
new car assessment program (EuroNCAP, Reference 5.5). The
EuroNCAP pedestrian tests (Figure 5.9) consist of:
• leg to bumper impacts with a “leg-form” impactor,
• upper leg to hood edge impacts with an upper “leg-form”
impactor,
• head to hood top impacts with two different “head-form”
impactors.
The European Union typically subjects a vehicle to three leg
to bumper impacts, three upper leg to hood edge impacts
and up to 18 head to hood top impacts. The results are
reported with a four-star rating system, similar to that used in
the United States NCAP program.
Japan’s NCAP program includes tests that simulate pedestrian
head to hood top impacts. However, leg to bumper and
upper leg to hood edge impacts are not included.
Currently, North American NCAP programs do not include
pedestrian requirements. However, the high number of
pedestrian accidents in North America and the trend to
global vehicle design, likely mean that pedestrian impact
requirements will come to North America in the longer term.
5.8.2 EuroNCAP leg to bumper impacts with a “leg-form” impactor
This test significantly influences bumper design. Thus, a brief
discussion of the requirements is in order. First, it should be
stated that the purpose of this test is to reduce severe lower
limb injuries in pedestrian accidents. The most common
lower limb injuries are intra-articular bone fractures, ligament
ruptures and comminuted fractures.
In this test, a “leg-form” impactor is propelled toward a
stationary vehicle at a velocity of 40 km/h (25 mph) parallel
to the vehicle’s longitudinal axis. The test can be performed
at any location across the face of the vehicle, between the
30° bumper corners.
5-39

5.8.3 Government regulations
The “leg-form” impactor is shown in Figure 5.10. It consists of two
semi-rigid 70mm (27.6 inches) diameter core cylinders (the “tibia”
and “femur”) connected by a deformable “knee joint.” This core
structure is wrapped in 25mm (1 inch) of foam “flesh” covered by
6mm (0.24 inches) of neoprene “skin.”
The performance criteria proposed for 2010 are shown in Figure
5.11. The maximum acceleration of the tibia is intended to
prevent fracture of the tibia due to bumper contact. The
maximum knee bend angle and shear deformation are intended
to prevent severe knee joint injuries such as ligament ruptures and
intra-articular bone fractures.
As of June 2005, there were no government regulations for
pedestrian impact. However, the European Union and major
vehicle associations have negotiated an agreement
(Reference 5.6). The agreement states that new vehicles will
achieve a limited level of pedestrian impact performance
starting in 2005, with an increased performance in 2010. The
limits shown in Figures 5.9 and 5.11 are the targets for 2010.
For 2005, the leg to bumper targets are:
• knee bending < 20°
• knee shear < 6mm (0.24 inches)
• acceleration < 200g
5.8.4 Design approaches
There are two general approaches to designing a front
bumper system for pedestrian safety:
• Provide front end vehicle components to cushion the
impact and support the lower limb
• Provide sensors and external airbags to cushion the impact
and support the lower limb
5.8.4.1 Cushioning the impact
Cushioning reduces the severity of bone fractures. It is
directly related to the acceleration impact criterion shown in
Figure 5.11. Limiting the lower limb acceleration to 150g
requires a bumper stiffness lower than that usually provided
to satisfy the damageability criteria associated with low-speed
[8 km/h (5 mph)] vehicle impact. Thus, a pedestrian friendly
bumper system must be capable of limiting “leg-form”
acceleration without sacrificing vehicle damageability in a
low-speed impact.
5.8.4.2 Supporting the lower limb
Supporting the lower limb reduces the risk of knee joint
injuries such as ligament ruptures and intra-articular fractures.
It is directly related to the knee bend angle criterion in Figure
5.11. Enough support must be provided below the main
bumper to limit the bending angle to 15°. Any support
provided must not conflict with styling requirements or result
in unacceptable low-speed [8 km/h (5 mph)] impact damage.
5-40

5.8.5 Design solutions
As bumper systems meeting the requirements of pedestrian
leg impact are only beginning to hit the marketplace in
Europe, Australia and Japan, it is too early to identify the
most popular designs. However, a thorough review of articles
and patents does indicate the most popular design solutions
for passenger cars. There is limited production of vehicles
with exposed bumper beams (facebars) in these areas.
Hence, there has been little activity devoted to adapting
facebars to meet pedestrian impact requirements. For
passenger cars with reinforcing beams, the most commonly
proposed design solutions are:
1. Front End Vehicle Component Solutions
a) Lower stiffener. A new component called a stiffener or
spoiler may be located below the bumper system to
prevent the lower part of the leg form from moving
further toward the vehicle than the knee. The stiffener
may be a fixed component or a component that deploys
based on impulse or speed.
b) Energy absorbers. To cushion impact, an energy
absorber may be placed between the bumper beam and
the pedestrian. Alternately, an energy absorber may be
placed behind the bumper beam. The most commonly
proposed energy absorbers are plastic foams (single or
multi-density) and molded plastic “egg crates”. However,
several proposed design solutions incorporate “spring
steel”, composite steel/foam and crush can absorbers.
c) Beam design. A tall front-view bumper height may be
used to provide leg support.
d) “Bull-bars”. Structures may be added to the front of an
existing bumper system to provide energy absorption
and to support the lower limb.
2. Sensor and Airbag Solution
Any current bumper system may be covered with an
airbag. In this way, the energy absorption capability of the
bumper becomes irrelevant. The key disadvantages to this
design approach are cost and sensor capability.
All of the Front End Vehicle Component Solutions listed
above may be used in conjunction with steel reinforcing
beam bumper systems. The Sensor and Airbag Solution
would appear to have the greatest potential for use with steel
facebar bumper systems such as those used on pickup trucks.
5-41

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5-43
FIGURE 5.11
EuroNCAP LEG FORM IMPACTOR

FIGURE 5.12
EuroNCAP “LEG FORM” IMPACT CRITERIA (2010)
5-44

6. Relevant safety standards in
North America and Europe
The bumpers on passenger cars sold in the United States must
conform to United States National Highway Traffic Safety
Administration (NHTSA) 49 C.F.R. Part 581 – Bumper Standard
(see Section 6.1).
The bumpers on passenger cars sold in Canada must conform to
Canadian Motor Vehicle Safety Regulations Section 615 of
Schedule IV (see Section 6.2). This regulation states a bumper must
meet the United States NHTSA Bumper Standard or ECE
Regulation 42 as explained in Section 6.2 of this publication.
Typically, although not mandatory, the bumpers on minivans sold in
the United States and Canada meet the NHTSA requirements for
passenger car bumpers. There are no federal regulations in the
United States or Canada for bumpers on pickups, full size vans or
SUVs. These bumpers are designed to meet OEM internal
specifications.
The Insurance Institute for Highway Safety (IIHS), in an effort to
reduce the cost of passenger vehicle bumper repairs, has
developed a test protocol that stimulates a broader range of impacts
occurring in actual on-th-road crashes (see Section 6.4). The IIHS
tests, conducted on passenger cars and minivans, are more severe
that the NHTSA tests. The IIHS protocol is not a pass or fail
protocol. Rather, it provides a weighted damage estimate that is
used to determine the overall rating for a passenger vehicle. Many
OEMs select a target overall rating for a vehicle to be sold in the
United States and Canada. This target is used when designing the
vehicle’s bumpers. IIHS is currently conducting research and testing
in order to develop a test protocol for SUVs and pickups.
Most passenger vehicles sold in Europe have bumpers that
conform to United Nations Economic Commission for Europe –
ECE Regulation 42 (see Section 6.3). Euro NCAP provides an
independent assessment of the safety performance of cars sold in
Europe. Pedestrian protection is an integral part of NCAP’s overall
rating scheme. Of particular significance in bumper design is the
leg to bumper impact requirements in the Euro NCAP Pedestrian
Protection Test (see Section 5.8.2). In addition, many European
bumpers are voluntarily designed to perform well in Research
Council for Automotive Repairs (RCAR) tests. RCAR’s Low-Speed
Offset Insurance Crash Test (see Section 6.6) was developed to
prevent unnecessary damage to the structure of passenger cars in
low- speed crashes. This test is now referred to as the RCAR
Structural Test. Even if a vehicle performs well in the RCAR
Structural Test, it may not exhibit good crash behaviour in real
world accidents (often due to override or underride). To overcome
this possibility, RCAR developed a test to assess how well a
vehicle’s bumper system protects the vehicle from damage in lowspeed
impacts. This test is the RCAR Bumper Test (see Section 6.7).
6-1

6.1 United States National Highway Traffic Safety Administration (49 C.F.R.),
Part 581 - Bumper Standard
6.1.1 Requirements
This standard (Reference 6.8) is summarized in Sections 6.1.1
through 6.1.5. The reader is cautioned that these sections are
only a summary. The reader must refer to the actual regulatory
document in order to obtain a complete understanding of the
standard.
The Bumper Standard only applies to passenger cars.
A passenger vehicle is subjected to three impact procedures:
1. The pendulum corner impacts - front and rear.
2. The pendulum longitudinal impacts - front and rear.
3. The impacts into a fixed collision barrier - front and rear.
Following the three impact procedures, the vehicle shall meet
the following damage criteria:
1. Each lamp or reflective device except license plate lamps
shall be free of cracks and shall comply with applicable
visibility requirements. The aim of each headlamp shall be
adjustable to within the beam aim inspection limits.
2. The vehicle’s hood, trunk and doors shall operate in the
normal manner.
3. The vehicle’s fuel and cooling systems shall have no leaks
or constricted fluid passages and all sealing devices and
caps shall operate in the normal manner.
4. The vehicle’s exhaust system shall have no leaks or
constrictions.
5. The vehicle’s propulsion, suspension, steering and braking
systems shall remain in adjustment and shall operate in the
normal manner.
6. A pressure vessel used to absorb impact energy in an
exterior protection system by the accumulation of gas or
hydraulic pressure shall not suffer loss of gas or fluid
accompanied by separation of fragments from the vessel.
7. The vehicle shall not touch the test device, except on the
impact ridge shown in Figures 6.1 and 6.2, with a force that
exceeds 2000 pounds (907kg) on the combined surfaces of
Planes A and B (see Figure 6.3) of the test device.
8. The exterior surfaces shall have no separations of surface
materials, paint, polymeric coatings, or other covering
materials from the surface to which they are bonded, and
no permanent deviations from their original contours
30 minutes after completion of each pendulum and barrier
impact, except where such damage occurs to the bumper
face bar and the components and associated fasteners that
directly attach the bumper face bar to the chassis frame.
9. Except as provided in Criterion 8 (above), there shall be no
breakage or release of fasteners or joints.
6-2

6.1.2 Vehicle
6.1.3 Pendulum corner impacts
6.1.4 Pendulum longitudinal impacts
1. The vehicle is at unloaded vehicle weight.
2. Trailer hitches, license plate brackets, and headlamp
washers are removed. Running lights, fog lamps and
equipped mounted on the bumper face bar are removed
if they are optional equipment.
1. See Figure 6.3.
2. Impact speed of 1.5mph (2.4km/h).
3. Impact one front corner at a height of 20 inches (500mm)
using Figure 6.1 pendulum.
4. Impact other front corner at a height from 16 to 20 inches
(400 to 500mm) using Figure 6.2 pendulum.
5. Impact one rear corner at a height of 20 inches (500mm)
using Figure 6.1 pendulum.
6. Impact other rear corner at a height from 16 to 20 inches
(400 to 500mm) using Figure 6.2 pendulum.
7. The plane containing the pendulum swing shall have a
60 degree angle with the longitudinal plane of the vehicle.
8. Impacts must be performed at intervals not less than
30 minutes.
9. Effective impacting mass of pendulum equals mass of
vehicle.
1. See Figure 6.3.
2. Impact speed of 2.5mph (4km/h).
3. Two impacts on front surface, inboard of corner.
4. Two impacts on rear surface, inboard of corner.
5. Impact line may be any height from 16 to 20 inches (400 to
500mm). If height is 20 inches (500mm), use Figure 6.1
pendulum. If height is between 20 and 16 inches (500 and
400mm), use Figure 6.2 pendulum.
6. Pendulum Plane A (see Figures 6.1 and 6.2) is
perpendicular to the longitudinal plane of the vehicle.
7. For each impact, the impact line must be at least 2 inches
(50mm) in the vertical direction from its position in any
prior impact, unless the midpoint of the impact line is more
than 12 inches (300mm) apart laterally from any prior
impact.
8. Impacts must be performed at intervals not less than
30 minutes apart.
9. Effective impacting mass of pendulum equals mass of
vehicle.
6-3

FIGURE 6.1
IMPACT PENDULUM
(20” Impact Height)
(Source: Reference 6.8)
FIGURE 6.2
PENDULUM
(20-16” Impact Height)
(Source: Reference 6.8)
6-4

FIGURE 6.3
SAMPLE IMPACT APPARATUS
Source: Transport Canada, Safety and Security
Sample impact apparatus
with supports
Sample impact apparatus
without supports
Plane B
Impact
Surface• •
Plane A
•
Weight equals
unloaded vehicle
weight +0, -10kg
NOTES:
1. Drawing not to scale.
2. The arc described by any point on impact line shall be constant with a minimum
radius of 3.3m and lie in a plane perpendicular to Plane A.
6-5

6.1.5 Impacts into a fixed collision barrier
1. Impact speed of 2.5mph (4km/h).
2. Impact into a fixed collision barrier perpendicular to line of
travel while travelling longitudinally forward.
3. Impact into a fixed collision barrier perpendicular to line of
travel while travelling longitudinally rearward.
6.2 Canadian Motor Vehicle Safety Regulations Section 615 of Schedule IV
This regulation (Reference 6.9) is summarized in Section 6.2.1.
The reader is cautioned that this section is only a summary. The
reader must refer to the actual regulatory document in order to
obtain a complete understanding of the regulation.
6.2.1 Requirements
A passenger car shall be equipped with bumpers that conform
to either:
a) the requirements set out in title 49, part 581 of the United
States Regulations or
b) the requirements set out in paragraph 6, and the low-speedimpact
test procedure set out in Annex 3, except for
paragraph 4 of that Annex, of ECE Regulation No. 42.
6.3 United National Economic Commissions for Europe – ECE Regulation 42
6.3.1 Requirements
This regulation (Reference 6.10) is summarized in Sections 6.3.1
through 6.3.5. The reader is cautioned that these sections are only
a summary. The reader must refer to the actual regulatory
document in order to obtain a complete understanding of the
regulation.
The requirements apply to a vehicle with at least four wheels for
the carriage of passengers comprising not more than eight seats in
addition to the driver’s seat. A passenger vehicle is subjected to
two impact procedures:
1. The longitudinal test procedure with an impact device - two
impacts at 4 km/h on the front surface and two impacts at
4 km/h on the rear surface.
2. The corner test procedure with an impact device - one
impact at 2.5 km/h on a front corner and one impact at
2.5 km/h on a rear corner.
After each impact test, the vehicle shall meet the following
requirements:
1. The lighting and signalling devices shall continue to operate
correctly and to remain visible. Bulbs may be replaced in the
event of filament failure.
2. The hood, trunk lid, and doors shall be operable in the normal
manner. The side doors shall not open during the impact.
3. The vehicle’s fuel and cooling systems shall have neither leaks
nor constricted fluid passages, which prevent normal
functioning. Sealing devices and caps shall be operable in the
normal manner.
4. The vehicle’s exhaust system shall not suffer any damage or
displacement, which would prevent its normal function.
5. The vehicle’s propulsion, suspension (including tires), steering
and braking systems shall remain in adjustment and shall
operate in a normal manner.
6-6

6.3.2 Test vehicle
6.3.3 Impact device
1. The protective devices and the mountings attaching them to
the vehicle structure may be repaired or replaced between
tests.
2. A vehicle of the same type may be used for each test.
3. “Unladen weight” means the weight of the vehicle in running
order, unoccupied and unladen but complete with fuel,
coolant, lubricant, tools and a spare wheel (if provided as
standard equipment by the vehicle manufacturer.
1. The impact device is shown in Figure 6.4.
2. The impact device may be either secured to a carriage
(moving barrier) or form part of a pendulum.
3. The effective mass shall be equal to the mass corresponding
to the “unladen weight” of the vehicle.
4. With Plane A of the impact device vertical, the reference line
shall be horizontal.
5. The reference line height is 445mm.
6.3.4 Longitudinal test procedure
6.3.5 Corner test procedure
Number of
Number of
Seating Positions Passengers Distribution
2 and 3 2 2 in the front seats
4 and 5 3 2 in the front seats
1 in the back seat
6 and 7 4 2 in the front seats
2 in the rearmost seats
8 and 9 5 2 in the front seats
3 in the rearmost seats
When the rear row of seats has
only two seating positions, one
person shall be on the second
row from the rear.
1. This procedure consists of four impacts at 4 km/h.
2. Two impacts are on the front surface and two impacts are on
the rear surface.
3. On each surface, one impact is made with the vehicle under
“unladen weight” and the other is made with the vehicle
under “laden weight.”
4. The choice of impact location for the first impact on each
surface is free. The second should be at least 300mm from
the first, provided the impact device does not overhang the
corner of the vehicle.
5. Plane A of the impact device shall be vertical and the
reference line horizontal at a height of 445mm.
1. This procedure consists of our impacts at 2.5 km/h.
2. Two impacts are on the front surface and two impacts are on
the rear surface.
3. On each surface, one impact is at one corner with the vehicle
under “unladen weight” and the second impact is at the other
corner with the vehicle under “laden weight.”
4. The choice of impact location for the first impact on each
surface is free. The second should be at least 300mm from
the first, provided the impact device does not overhang the
corner of the vehicle.
5. Plane A of the impact device shall be vertical and the
reference line horizontal at a height of 445mm./
6-7

6-8
FIGURE 6.4
IMPACT DEVICE
(Source: Reference 6.10)

6.4 Insurance Institute for Highway Safety: Bumper Test Protocol (Version VII)
6.4.1 Requirements
6.4.2 Test vehicles
This protocol (Reference 6.11) is summarized in Sections 6.4.1
through 6.4.4. The reader is cautioned that these sections are only
a summary. The reader must refer to the actual protocol document
in order to obtain a complete understanding of the protocol.
Four tests (a front and a rear full-overlap test at 10 km/h and a front
and a rear corner test at 5 km/h) are conducted. After each test, a
damage estimate is prepared as it would be done in a repair shop.
A weighted damage estimate is calculated by adding the front
full-overlap damage estimate to the rear full-overlap damage
estimate and multiplying the total by two; adding to this amount
the front corner damage estimate and the rear corner damage
estimate; then dividing the grand total by six to get a weighted
average damage estimate. The weighted average damage estimate
is used to determine the overall rating for a vehicle. The
good/acceptable boundary is $500, the acceptable/marginal
boundary is $1,000 and the marginal/poor boundary is $1,500.
However, no vehicle can earn a rating of good or acceptable if the
vehicle is deemed undrivable or unsafe because of severe
headlamp or tail lamp damage, hood buckling, coolant loss or the
like.
1. Two vehicles are purchased to conduct the four tests.
2. The front and rear license plate brackets (if provided) and all
associated fasteners are removed. Bolt-on trailer hitch
reinforcement members that are supplied as optional
equipment are removed, but their fasteners are reattached to
the vehicle where possible.
6.4.3 Impact barrier
6.4.4 Full-overlap impact
1. The Impact Barrier is shown in Figure 6.5.
2. The bumper barrier is constructed of 12.5mm steel plate
(Figure 6.6) and mounted to a block of reinforced concrete
weighing 145,150 kg.
3. A steel backstop is constructed of 12.5mm steel plate (Figure
6.7). It is mounted to the upper surface of the bumper barrier
rearward from the impact face of the bumper barrier.
4. A plastic energy absorber is affixed by nylon push-pin rivets to
the impact face of the bumper barrier.
5. An overlying plastic cover is mounted over the plastic energy
absorber on the bumper barrier.
6. An overlying plastic cover is mounted over the steel backstop.
1. Two tests - front into barrier and rear into barrier.
2. Impact speed of 10 km/h.
3. The forwarding portion of the bottom edge of the bumper
barrier is 457mm from the floor.
4. At impact, the vehicle centerline is aligned with the bumper
barrier centerline.
6-9

6-10
FIGURE 6.5
IIHS IMPACT BARRIER
(Source: Reference 6.4)

FIGURE 6.6
STEEL BUMPER BARRIER
(Source: Reference 6.4)
FIGURE 6.7
STEEL BACKSTOP
(Source: Reference 6.4)
6-11

6-12
FIGURE 6.8
OVERLAP FOR FRONT CORNER TEST
(Source: Reference 6.4)

6.4.5 Corner impact
1. Two tests - front corner into barrier and rear corner into
barrier.
2. Impact speed of 5 km/h.
3. The forwardmost portion of the bottom edge of the bumper
barrier is 406mm from the floor.
4. At impact, the vehicle overlaps the lateral edge of the barrier
by 15% of the vehicle’s width at the wheel wells (including
moldings and sheet metal protrusions) at the corresponding
axle - front axle for front corner test (Figure 6.8) and rear axle
for rear corner test.
6.5 Consumers Union bumper basher tests
This test (Reference 6.12), which is no longer used, consisted of
impacting the front and rear bumpers of a vehicle three times
each. An impact bar, similar to that shown in Figure 6.4, was
hydraulically propelled into the center, off-center and corner of
the front and rear bumpers. Following the six impacts, the total
cost for parts and labor to repair the damage to the body and
bumper for both the front and rear of the vehicle were published
in Consumer Reports magazine.
The Consumers Union now relies on the IIHS Bumper Test
Protocol (see Section 6.4).
6.6 Research Council for Automotive Repairs (RCAR) Low-Speed Offset Crash Test (Low-Speed Structural Test)
This test (Reference 6.13) is summarized in Sections 6.6.1 through
6.6.4. The reader is cautioned that these sections are only a
summary. The reader must refer to the actual test document in
order to obtain a complete understanding of the test.
RCAR states its purpose of this test is to determine a vehicle’s
damageability and repairability features.
6.6.1 Requirements
6.6.2 Test vehicle
Two impacts are conducted. The first is a 15 km/h (9mph) impact
by the front of the test vehicle into a fixed barrier with a 40%
offset. The second is a 15km/h (9mph) impact by a mobile barrier,
with a 40% offset, into the rear of the test vehicle. After each
impact, the replacement parts required to reinstate the vehicle to
its pre-accident condition are recorded. Also, the number of hours
required to replace the damaged parts and to repair those items
capable of repair, such that the vehicle is reinstated to the pre-accident
condition are recorded. The cost of the replacement parts and the
number of hours are estimated. Thus, the results of the crash test
indicate the repairability and damageability status of the test vehicle.
The test procedure applies to people driven passenber vehicles of
up to 2.5 times mass. The test vehicle shall be previously
undamaged and representative of the series production. The test
vehicle for the rear impact may be the same vehicle used for the
front impact, provided the damage sustained during the front
impact has no effect on the results of the rear impact.
6-13

6.6.3 Front impact
1. One impact into a non-deformable barrier/former (see Figure
6.5). The former can be adjusted laterally to accommodate
various vehicle widths. The former may be secured to a fixed
barrier or placed on the ground with arresting devices to
restrict its movement. The front face of the former is
perpendicular to the direction of travel of the test vehicle.
The mass of the barrier/former exceeds twice that of the test
vehicle. The steering column side of the vehicle contacts the
former. The test vehicle overlaps the former by 40%.
2. The test vehicle impact speed is 15km/h (9mph).
6.6.4 Rear impact
1. One impact by a mobile barrier into the test vehicle (Figure
6.6). The mobile barrier has a mass of 1000kg (2205 pounds).
2. The mobile barrier contacts the side of the vehicle opposite
to the steering column side. The barrier overlaps the test
vehicle by 40%. The barrier impact speed is 15 km/h (9mph).
6-14

6-15
FIGURE 6.9
RCAR FRONT CRASH PROCEDURE
(Source: Reference 6.13)

6-16
FIGURE 6.10
RCAR REAR CRASH PROCEDURE
(Source: Reference 6.13)

6.7 Research Council for Automotive Repairs (RCAR) Bumper Test
This test is summarized in Sections 6.7.1 through 6.7.3. The reader
is cautioned that these sections are only a summary. The reader
must refer to the actual test documents (References 6.14 and 6.15)
in order to obtain a complete understanding of the test.
The RCAR Bumper Test encourages vehicle manufacturers to
produce effective bumper systems that feature tall energy
absorbing beams and crash boxes, that are fitted at common
heights and can effectively protect the vehicle in low speed
crashes. To this end, RCAR also publishes a Design Guide
(Reference 6.16) to ensure good design practice for repairability
and limitation of damage.
The RCAR test applies to passenger cars, pickups and SUVs.
6.7.1 Requirements
Bumper beams that have insufficient height will be presumed to fail
the test. Also, bumper beams that use the barrier system backstop
for energy management will be regarded as unacceptable.
Bumper beams are likely to have insufficient height if the relevant
bumper engagement is less than 75mm as shown in Figure 6.11.
For a front bumper, the distance from the floor to the underside of
the bumper barrier is 455mm. For a rear bumper, the distance from
the floor to the underside of the bumper barrier is 405mm.
Bumper beams with a relevant engagement less than 75mm will be
tested if the qualifying bumper beam height is 100mm or more.
Bumper beam height is measured in the center of the vehicle, in
front of the left siderail and in front of the right siderail. The center
of the vehicle bumper height is weighted 50%. The left and right
siderail bumper heights are each weighted 25%. The sum of the
three weighted heights is the qualifying bumper beam height.
The test involves either the front or rear of a moving car striking a
fixed bumper barrier at 10 km/h. The centerline of the car is aligned
with the center of the bumper.
RCAR does not assign vehicle ratings. It states that results from the
RCAR Bumper Test may be used by RCAR members (or the
associated test organizations) for rating or consumer information
purposes to suit local market conditions.
6.7.2 Bumper Barrier
1. The bumper barrier is shown in Figures 6.11 - 6.14.
2. The rigid bumper barrier is made from steel. It is 100mm deep
and 1500mm wide. The flat front face has a radius of
3400mm. The bumper barrier can be mounted at various
heights to the unyielding and immovable crash wall.
3. A rigid steel backstop is fixed on top of the barrier. It has the
same radius and width as the bumper barrier.
4. An energy absorber is firmly affixed to the face of the bumper
barrier.
5. A cover over the energy absorber is wrapped around the
bumper barrier and fastened to the top and bottom plane of
the barrier.
6-17

6-18
FIGURE 6.11
RELEVANT BUMPER ENGAGEMENT
(Source: Reference 6.14)

FIGURE 6.12
BUMPER BARRIER
(Source: Reference 6.14)
FIGURE 6.13
BUMPER BARRIER WITH BACKSTOP AND ENERGY ABSORBER
(Source: Reference 6.15)
6-19

6.7.3 Full overlap impact
1. Both the front and rear of a moving vehicle strike the fixed
bumper barrier at 10 km/h.
2. The vehicle should be at normal curb weight plus a 75kg
dummy or equivalent in the driver’s seat. In addition, the fuel
tank should be filled to 90% of capacity or weight equivalent.
3. The centerline of the vehicle is aligned with the center of the
bumper.
4. For a front bumper test, the distance from the floor to the
underside of the bumper barrier is 455mm. For a rear bumper
test, the distance from the floor to the underside of the
bumper barrier is 405mm. The distance for a rear bumper test
on a pickup or SUV may be 455mm.
6-20

7. Summary/Conclusions
• STEEL BUMPER MARKET - Steel bumper systems currently make
up 83% of the market, Aluminum bumper systems have 16%
market share, and the remaining 1% are composite bumper
systems.
• BUMPER SYSTEM CATEGORIES - Steel bumper systems fall into
two categories: beams and facebars.
- Bumper beams are not visible on the vehicle because they are
surrounded by plastic fascia. Most bumper beams are currently
manufactured from roll-forming, hot-stamping, or a combination
of both processes. These advanced manufacturing processes
enable the use of ultra high strength steels, which are essential
for mass reduction.
- Facebars, also referred to as truck bumpers, are clearly visible
on the vehicle and are painted or chromed to improve surface
appearance. Most facebars are manufactured by stamping mild
or conventional high strength steels. However, facebars are
expected to transition to advanced high strength steels in the
future to facilitate mass reduction.
• ROLL FORMED BUMPER BEAMS - The roll-forming process can
be used to make complex cross sections out of ultra high
strength steels with very low elongation. Approximately 72% of
steel bumper beams in North America are currently roll-formed
and the most common cross sections are B-sections, box
sections, and C-sections. The most common steel grades
currently used for roll-formed bumper beams are Recovery
Annealed (XF), DP980, and M190 Martensitic Steel. However,
more roll-formed bumpers are expected to transition to higher
strength Martensitic Steels, with over 1700 MPa minimum tensile
strength, in the future to facilitate mass reduction.
• HOT FORMED BUMPER BEAMS - In the hot-forming process,
steel is heated up to 900 ˚C for several minutes prior to forming.
This enables the steel to be formed into deep complex shapes
just prior to quenching. The quenching operation transforms the
microstructure of the steel into martensite, thus transforming it
into ultra high strength steel. Only Manganese-Boron (MnB)
steels are used in the hot-forming process. But these steels can
be hot-rolled, cold-rolled, bare, or coated. The most common
MnB steel grade currently used for hot-formed bumper beams is
10B21 with a 1500 MPa minimum tensile strength after forming.
However, more hot-formed bumpers are expected to transition to
higher strength MnB steels, with over 1900 MPa minimum tensile
strength, in the future to facilitate mass reduction. Most hotformed
beams are either hat-sections or hat-sections with front or
back plates welded on to create a closed box section. But
seamless closed box sections without weld flanges are also
available from limited suppliers. Hot-formed beams are currently
estimated to have 10% of the steel bumper market. However,
this number is expected to rise in the future since hot-forming
manufacturing facilities are steadily increasing and also because
hot-formed bumpers have the lowest average mass of all steel
bumper systems.
7-1

• BUMPER CORROSION PROTECTION - The coatings used
influence the corrosion life of the bumper system. Metal
facebars use bare steel which is e-coated and then painted or
chromed. Most roll-formed bumper beams also use bare steel
and are e-coated after forming. However, zinc coated steels (GI,
GA, and EG) are increasingly being used to improve corrosion
life since the gauges of the steel used are decreasing as the
strength of the steel used is increasing. Most hot-formed bumper
beams have an aluminized coating which eliminates the need for
shot blasting after forming and also provides barrier protection
from corrosion. In addition, they are usually e-coated. However,
the use of zinc coated MnB steels is expected to increase since
they provide improved corrosion protection.
• BUMPER STEEL GRADE AND MANUFACTURING PROCESS
COMPATIBILITY - It is important to consider the manufacturing
process with the steel grade selection. For facebars, it is essential
to use a steel grade with decent elongation so that it can be
stamped without splitting. In addition, the steel grade used must
have good surface quality after forming and polishing. For rollformed
beams, elongation is not very important. However,
higher elongation steel grades will allow tighter radii and higher
sweep capability. For hot-formed beams, only MnB steels are
used. However, different gauges, strength levels, and coatings
are available that will affect the manufacturing process. For
example, most hot-formed bumper beams with gauges over 2.0
mm use bare hot-rolled MnB steels that require a shot blasting
operation after forming and quenching to remove the scale.
• BUMPER WELDING - Most front bumper beams, and to a lesser
extent, rear bumper beams, have mechanical energy absorbers,
also referred to as crush cans, attached to them by welding. MIG
welding is the preferred attachment method for most bumper
beams. However, other welding methods described in this
document can also be used. It is important that the welding
method is compatible with the steel grades and coatings
selected. For example, laser welding is not a preferred
attachment method for aluminized hot-formed beams.
• BUMPER SWEEP - Bumper beam sweep is affected by the styling
of the vehicle. The greater the curvature or the plastic fascia,
especially at the front of the vehicle, the greater the amount of
bumper beam sweep is desired. If the fascia curvature does not
match the bumper beam sweep, then more foam will be required
to fill in the gap between the beam and fascia and this will
increase the system cost.
• BUMPER DESIGN REQUIREMENTS - The main objective of the
bumper system is to absorb energy during low speed impacts
and minimize damage taken by more expensive components like
the headlights, radiator, and sheet metal of the fender and hood.
Most bumper design requirements, regardless of country of
origin, reflect this objective. However, some tests are more
severe than others and are also set up differently. Furthermore,
Europe recently introduced pedestrian protection and corrosion
life requirements. These factors lead to a very large number of
design requirements for a bumper system that is sold in several
different countries on a global platform. Unfortunately, more
design requirements leads to greater bumper system mass. A
global bumper system can weigh up to twice as much as a
bumper system on a vehicle sold in only North America.
7-2

• BUMPER MASS REDUCTION - Mass reduction is critical to the
future of steel bumper systems and can be accomplished in
several ways:
- Eliminate global bumper system platforms. Because all bumper
systems are bolt-on components, it is possible to manufacture
bumper systems specific to the country in which the vehicle is
manufactured and sold.
- Use higher strength steels. 3rd Generation AHSS will be
available soon and higher strength MnB and Martensitic UHSS
grades are available now to help bumper systems meet design
requirements at lower gauges and mass.
- Use tailored products. Both tailored blanks and tailor rolled
blanks have been implemented into production for steel
bumper systems. They reduce mass by allowing the bumper
designer to put higher gauges only where they are needed to
meet design requirements.
- Geometry evolution. Continue to enhance geometries for
facebars, bumper beams, and crush cans so they can absorb
more energy at lower mass. Advanced manufacturing
technologies such as 3D roll-forming and sheet hydroforming
enable more radical geometries.
7-3

8. References
1.1 North American Bumper System Market study, 2008/2009 and 2012
estimates, Ducker Worldwide, 1250 Maplelawn Drive, Troy, MI
48084.
2.1 WorldAutoAsteel. (2011) FutureSteelVehicle – Final engineering
report. Retrieved from
http://www.autosteel.org/Programs/Future%20Steel%20Vehicle.aspx
2.2 www.worldautosteel.org, AHSS Guidelines, AHSS Descriptions,
Definitions
2.3 WorldAutoSteel. http://www.workdautosteel.org/[Web resources].
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Online.
http://www.i-car.com/pdf/advantage/online/2004/051004.pdf.
2.5 SAE J2329, Categorization and Properties of Low-Carbon
Automotive Sheet Steels, Society of Automotive Engineers, Inc., 400
Commonwealth Drive, Warrendale, PA 15096-0001.
2.6 SAE J1562, Selection of Zinc and Zinc-Alloy (Hot-Dipped and
Electrodeposited) Coated Sheet Steel, Society of Automotive
Engineers, Inc., 400 Commonwealth Drive, Warrendale, PA 15096-
0001.
2.7 SAE J403, Chemical Compositions of SAE Carbon Steels, Society of
Automotive Engineers, Inc., 400 Commonwealth Drive, Warrendale,
PA 15096-0001.
2.8 SAE J405, Chemical Compositions of SAE Wrought Stainless Steels,
Society of Automotive Engineers, Inc., 400 Commonwealth Drive,
Warrendale, PA 15096-0001.
2.9 www.astm.org, ASTM A463, Standard Specification for Sheet Steel,
Aluminum-Coated, by the Hot Dip Process.
4.1 Sheet Steel Availability and Property Guide, insert to High-Strength
Steel Bulletin, Edition 10, Auto/Steel Partnership, 2000 Town Center,
Suite 320, Southfield, MI 48075-1123.
4.2 Automotive Steel Design Manual, American Iron and Steel Institute,
2000 Town Center, Suite 320, Southfield, MI 48075-1199.
4.3 High-Strength Steel Bulletin, Edition 5, Auto/Steel Partnership, 2000
Town Center, Suite 320, Southfield, MI 48075-1123.
4.4 Inland Ultra-High-Strength Steels Selection Guide, Inland Steel, Ultra
High-Strength Steel Marketing, telephone 1-800-422-9422.
4.5 David W. Dickinson, Final Report to AISI Bumper Group, Bumper
Component Welding, State-of-the-Art Survey, December 31,2000.
4.6 Linnert, Welding Metallurgy, American Welding Society, 1994.
4.7 American Welding Society, Welding Handbook, Volume 4, 1998.
4.8 Peterson High Speed Seam Welding, American Welding Society
Metal Welding Conference VI, 1994.
4.9 Appreciating high-frequency welding, Welding Journal, July 1996.
4.10 American Welding Society, Welding Handbook, 8th Edition, Volume 2.
4.11 Walduck, R., Enhanced Laser Beam Welding, U.S. Patent 5886870,
February 2, 1999.
4.12 Dykhno, I., et al, Combined Laser and Plasma Arc Welding Torch, U.S.
Patent 5700989, December 23, 1997.
4.13 Categorization and Properties of Low-Carbon Automotive Sheet
Steels, SAE J2329, Society of Automotive Engineers, Inc., 400
Commonwealth Drive, Warrendale, PA 15096-0001.
4.14 Steel, high-strength, Hot Rolled Sheet and Strip, Cold Rolled Sheet
and Coated Sheet, SAE J1392, Society of Automotive Engineers, Inc.,
400 Commonwealth Drive, Warrendale, PA 15096-0001.
4.15 Chemical Compositions of SAE Carbon Steels, SAE J403, Society of
Automotive Engineers, Inc., 400 Commonwealth Drive, Warrendale,
PA 15096-0001.
8-1

5.1 High-Strength Steel Bulletin, Edition 9, Auto/Steel Partnership, 2000
Town Center, Suite 320, Southfield, MI 48075-1123.
5.2 NHTSA New Car Approval Program, Frontal-crash Test, web site
NHTSA.gov/NCAP.
5.3 Crashworthiness Evaluation of Offset Barrier Crash Test Protocol,
(Version IX), May, 2002, Insurance Institute for Highway Safety, web
site carsafety.org
5.4 Schuster, Dr. Peter, “Current Trends in Bumper Design for Pedestrian
Impact”, December 31, 2004, www.autosteel.org
5.5 EuroNCAP (European New Car Assessment Program),
www.euroncap.com
5.6 European Union/Vehicle Associations Pedestrian Safety Agreement,
www.acea.be/ACEA/11072.001.pdf
6.1 High-Strength Steel Bulletin, Edition 17, Auto/Steel Partnership, 2000
Town Center, Suite 320, Southfield, MI 48075-1123.
6.2 High-Strength Steel (HSS) Stamping Design Manual, Auto/Steel
Partnership, 2000 Town Center, Suite 320, Southfield, MI 48075-1123.
6.3 High-Strength Steel Bulletin, Edition 4, Auto/Steel Partnership, 2000
Town Center, Suite 320, Southfield, MI 48075-1123.
6.4 SAE J2340, Categorization of Dent Resistant, High-Strength and
Ultra High-Strength Automotive Sheet Steel, Society of
Automotive Engineers, Inc., 400 Commonwealth Drive,
Warrendale, PA, 15096-0001.
6.5 Weld Quality Test Method Manual, Auto/Steel Partnership, 2000
Town Center, Suite 320, Southfield, MI 48075-1123.
6.6 ANSI/AWS/SAE Standard D8.9-97, Standard Recommended
Practices for Test Methods for Evaluating the Resistance Spot
Welding Behavior of Automotive Sheet Steel Materials, Society of
Automotive Engineers, Inc. 400 Commonwealth Drive, Warrendale,
PA, 15096-0001.
6.7 ANSI/AWS/SAE Standard D8.8-97, Specification for Automotive and
Light Truck Component Weld Quality - Arc Welding, Society of
Automotive Engineers, Inc. 400 Commonwealth Drive, Warrendale,
PA, 15096-0001.
6.8 United States, Code of Federal Regulations, Title 49 - Transportation,
Part 581 - Bumper Standard, 2006.
6.9 Government of Canada, Motor Vehicle Safety Regulations, Section
215 of Schedule IV, June 12, 2008.
6.10 United Nations Economic Commission for Europe, ECE Regulation
No. 42 - Uniform Provisions Concerning the Approval of Vehicles
with regard to Their Front and Rear Protective Devices (Bumpers,
etc.), Addendum 41, Corrigendum 1, Amendment 1, June 12, 2001.
6.11 Insurance Institute for Highway Safety, Bumper Test Protocol (Version
VII), June 2009.
6.12 Consumer Reports, April 1990
6.13 RCAR Procedure for Conducting a Low Speed 15 km/h Offset
Insurance Crash Test to Determine the Damageability and
Repairability Features of Motor Vehicles, Issue 2.1, September 2006,
www.rcar.org/papers
6.14 RCAR Bumper Test, Issue 1.02, November 2008, www.rcar.org/papers
6.15 15 Appendix 1, Dimensions and Specifications of the RCAR Bumper
Barrier System, Issue 1, September 2007, www.rcar.org/papers
6.16 RCAR Design Guide, www.rcar.org/papers
8-2

Steel Market Development Institute
2000 Town Center, Suite 320
Southfield, Michigan 48075