Die Steels - Buderus Edelstahl Gmbh

Die Steels
I Production Technology I Properties I Applications

Buderus Edelstahl – The Specialist for Die Steel
State-of-the-art metallurgy
and forging technology
55 MN open die forging press, finish forging of 1400x750x8500 mm die block weighing 70 tonnes
Customized steels and
mould parts for
manufacturing dies
• Producing high purity electric steel
melts using secondary and vacuum
metallurgical processes
• Producing tool steels of Buderus ISO-B
quality, i.e. special melts with extremely
low sulfur content and high percentage
purity
• Bottom ingot pouring and special hood
type plant for making low-segregation
raw ingots
• Hot forming using programmed forging
sequences for ingots up to 150 tonnes
and a maximum forging weight of 80
tonnes
• All heat treatment processes in continuous
furnaces, bogie hearth furnaces
and batch furnaces and under protective
gas, vacuum atmosphere with
compressed gas tempering and salt
bath hardening
• Efficient machining to customer
specification and drawing
• Stocking the complete range of tool
steels, round, square and flat,
immediate delivery ex stock
• Blanks split longitudinally or across:
Prompt delivery from material in stock
• Custom heat treating, including post
rough machined moulds
Forging round bar on the
55 MN open die forging press Annealing Individually heat treated disks for die inserts

• Rough machining
• Full service in-house technical
resources to assist with questions
regarding material selection, heat
treatment or die design.
• Assistance with developing new
dies and die materials for special
requirements
• Failure analysis assistance, with
objective enhanced tool life
recommendations
Fully automatic 80 MN closed-die forging press
Truck steering knuckle die insert Truck steering knuckle blank

The material concept
The right material for all
application profiles
Optimal use of a die steel is closely linked to understanding its stress
profile (Figure 1). The right die steel for forging-die and press-die
units and secondary tools is selected bearing in mind economic
and qualitative aspects. One major factor is the die’s service life
or estimated tool life quantity (see Tables 1 and on page 8). The
tool life quantity is generally limited by wear, or by cracking in the
case of complicated impressions (see Table 1 on page 8+9).
Die wear is significantly reduced as the alloy content of carbide
formers such as vanadium, molybdenum, tungsten and chromium
is increased, as shown in Figure . One qualitative measure of this
is the alloy coefficient (AC) used to rate steel. Higher-grade steels
produce favourable results when an optimum relationship between
tool life quantity and tool costs is achieved.
The tool life quantity can be further optimized by increasing hardness,
balanced with the necessary toughness characteristics. Key
here is uniform quenching and tempering of the dies throughout
their cross-section. Comparing the hardness distribution of the
standard die steel 2714 ISO-B to the recently developed new die
steel 2714ISO-Bmod. confirms this modified composition improves
hardening and tempering characteristics (see Figure and Table
on page 10).
Figure 1
Die tool stress profile
Mechanical
stress
Thermal
stress
Mechanically induced
state of tension
Mechanical die load
Relative movement
die/forging
Deformation • Cracking • Fracture
Wear • Deformation • Temperature fatigue cracking
Thermally induced
state of tension
Thermal die load
Loss of cohesion
Matched material characteristics
ensure high tool life quantities
This special steel is effective for forging dies with high volumes,
regardless of the die size and impression depth.
Heat resistance and hardness retention are key material indicators
for die steels. Loss of hardness and even transformation of the
microstructure at the impression surface is the most frequent cause
of wear, deformation and cracking.
Figure 2
Effect of alloy content on die wear
Die wear (µm)
µm
350
300
250
200
150
100
50
2713
2714
2744
2714mod.
2766
2343
2606
2365
2344
2367
Temperature 250°C
Alloy coefficient
2Cr + 5W + 10Mo + 40V
0
0 10 20 30 40 50 60 70 80 90 100 110 120
Alloy coefficient

Die steels can be divided into two groups according to their tempering
behaviour as illustrated in Figure :
Group 1
The low hardness retention of these nickel alloy steels makes
them unsuitable for applications involving high temperature load
(> 500 °C) with relatively long or frequent contact phases, as for
example in presses.
Group 2
These steels are much more resistant to thermal load than those
in Group 1, and also more wear resistant, in line with the higher
carbide content in the matrix. In addition to hardness retention,
the level of the Ac1 conversion temperature is significant for the
temperature capacity of a die steel (cf. Table on page 10). Steels
with lower Ac1 temperatures can be more easily converted and
hardened after extended press contact phases. The consequences
are premature local wear and cracking in the impression. Measures
to improve wear resistance however generally result in higher
susceptibility to cracking of the forging die.
The tougher nickel alloy steels in group 1 (see table ) are less susceptible
to stress cracking than the higher alloyed steels, containing
special carbides, described in Group .
A low level of thermal conductivity (Table ) can be taken as an
indicator of increasing danger of cracking when exposed to critical
temperature fluctuations.
Figure 3
Comparative hardness profile curve
Hardness (HB)
HB
400
375
350
325
2714 ISO-B
2714 ISO-B mod.
300
0 100 200 300 400 500 600 700 800 900 1000
Rod diameter (mm)
mm
Pre-heating the die to 280 °C
The best known measures for reducing susceptibility to cracking
are increasing material toughness by means of moderate strength
when assembled, and sufficiently high pre-heating temperature
(see Figure 5).
Figure 5
Effect of pre-heating temperature on notch impact energy
Notch impact energy ISO-V (J)
Figure 4
Hardness retention of the Group 1 and Group 2 die steels
Hardness (HRc)
J
100
80
60
40
20
HRc HB
60
55
50
45
40
Group 2 die steels,
hardness 415 HB
0 200 400
Test temperature (°C )
600
Alloy groups
1
2
NiCrMoV
die steels
CrMoV
hot working steels
Pre-heating
temperature for dies
~565
~485
~425
~375
35
~330
0 200
400 600 800
Tempering temperature (°C )
°C
°C
Hardness (HB)
5

We do not want your dies to look old –
but we do want them to last
Operating conditions
Die design, forging conditions and die maintenance
are important factors in long service life,
in addition to the optimum material concept.
Crack formation in critical zones of the impression
can be restricted by design measures
such as:
• Allowing large radii (> mm)
• Avoiding extremely steep impression
side walls > 80°
• Allowing large enough wall thicknesses
in one-part dies > 1. x impression
depth
• Use of – part dies with shrunk inserts
• Ensuring there is a ratio > 1: between
the wall thickness of the insert and that
of the basic die
• Using adequate shrinkage
allowance > ‰
• Making smooth impression surfaces,
surface roughness < 5 µm
Crankshaft die
The following rules are important to avoid
cracks and increased wear in operation:
• Homogeneous die preheating to 80 °C
• Using intensive cooling to avoid die base
temperatures > 00 °C
• Using optimum lubricants and coolants
with thermally insulating effect to avoid
critical surface temperatures > 50 °C
• Achieving the shortest possible pressure
contact times, e.g. by optimized ejection
system
• Allowing long enough cooling phases
between forging sequences
• Measures to avoid extremely damaging
“die stickers”
Truck front axle die
with forging blank
• Avoiding unnecessarily high forging
temperatures (> 1 70 °C)
• Predetermined preventive maintenance
schedule for all critical dies
• Remove by grinding, surfaces impaired
by wear or heat check (depth ~ 0.1 mm /
1000 pieces)
• Adequate pre-heating ( 50° C) and
stress relief (550 °C) with all welding
repairs

Extreme dimensions
for extreme demands
Quality for safety and success
The operational capacity of our plant enables
us to produce even the largest die steel
dimensions.
The sequence of work for manufacturing die
steels is supported by the embedded quality
management system, and is strictly monitored.
The heart of the quality assurance
system is our modern laboratory with test
equipment for determining characteristics
such as hardness, strength, toughness, fracture
toughness, microstructure and percentage
purity. Ultrasonic testing of each individual
die block eliminates internal defects,
Die blank for aluminium aircraft parts
and mobile spectrometer equipment is used
to prevent material substitution.
As well as our internal requirements, external
specifications and customer requirements
can be taken into account at any
point within the process chain.
Inspection and testing results are confirmed
to the customer on request with each
delivery, in the form of a certificate.
Quality monitoring and quality assurance
are carried out in accordance with the
certified quality assurance system ISO
9001: 000, which satisfies the most stringent
requirements including those of power
generation and defence technology.
ISO 9001:2000
650 MN closed-die forging press
Photo: Aubert & Duval, Interforge
Die impression for a crankshaft Heat treatment of a die block
7

Table 1 Selection of material for forging dies and press dies
Strength range: ±50 N/mm
Brinell hardness range: ± 0 HB
Rockwell hardness range: ± HRc
Table 2 Material selection for secondary tools
(Die holder, tool cassettes, punching and trimming dies, ejectors, upper dies)
8
Forging unit
Tool Die holder,
Casings,
Tool cassettes
Punching and trimming dies Ejectors,
Upper dies
Field of application Presses and hammers Cold cutting Hot cutting Presses
Stress
Tool steel
Recom.
strength / hardness
2714 ISO-B
2714 ISO-B mod.
Small quantities,
Normal wear
Large quantities,
High wear
Strength
when assembled
Hardness
Small tools
Large quantity
Large tools,
Small quantity
2842 2379 ISO-B 1730 * 2714 ISO-B
2767 ISO-B
2344 ISO-B
* Cutting edges stellite armoured
Hammer unit
Tool type Full die
Stress and tool life quantity criterion
Forging quantity – batch size
Die steel and impression typology
Flat dies rotationally symmetrical and asymmetrical
Solid dies symmetrical and asymmetrical
Pivots and hubs dies rotationally symmetrical and asymmetrical
Mandrel dies rotationally symmetrical, deep impression
Material number 2714
ISO-B
Cracking
low high
2714
ISO-Bmod.
2344 ISO-B
2365 ISO-B
1000 N/mm 58 HRc 0 HRc 750 N/mm 50 HRc 50 HRc
Wear
low high
2714
ISO-B
N/mm 1 00 1 00 1 50 1 50
Hardness HB 85 85 00 00
Material number 2714
ISO-B
2714
ISO-Bmod.
2714
ISO-B
N/mm 1 00 1 00 1 50 1 50
Hardness HB 85 85 00 00
Material number 2714
ISO-Bmod.
2714
ISO-Bmod.
2714
ISO-Bmod.
N/mm 1 00 1 00 1 50 1 50
Hardness HB 85 85 00 00
Material number 2714
ISO-Bmod.
2365
ISO-B
2714
ISO-Bmod.
2714
ISO-Bmod.
2714
ISO-Bmod.
2714
ISO-Bmod.
2365
ISO-B
N/mm 1 00 1 50 1 00 1 50
Hardness HB 85 00 85 00

Cracking
low high
2714
ISO-Bmod.
2344
ISO-B
Press unit
Die inserts Full die Die inserts
Wear
low high
2714
ISO-Bmod.
2344
ISO-B
Cracking
low high
2714
ISO-Bmod.
2344
ISO-B
Wear
low high
2714
ISO-Bmod.
Cracking
low high
Die tools with different impressions
for the motor industry
Wear
low high
1 50 1 00 1 50 1 00 1 00 1 50 1 00 1 50 1 50 1 50 1 50 1500
00 85 00 10 10 5 10 5 5 5 5 0
2714
ISO-Bmod.
2714
ISO-Bmod.
2714
ISO-Bmod.
2344
ISO-B
2714
ISO-Bmod.
2367
ISO-B
1 50 1 50 1 50 1 00 1 00 1 50 1 50 1 50 1 50 1500 1 50 1550
00 00 00 10 10 5 5 5 5 0 5 50
2714
ISO-Bmod.
2365
ISO-B
2714
ISO-Bmod.
2365
ISO-B
2344
ISO-B
2367
ISO-B
1 00 1 00 1 50 1 00 1 00 1 50 1 00 1 00 1500 1550 1 50 1550
85 10 00 10 10 5 10 10 0 50 5 50
2365
ISO-B
2365
ISO-B
2365
ISO-B
2365
ISO-B
2344
ISO-B
2365
ISO-B
1 50 1 50 1 50 1 50 1 50 1500 1500 1500 1 50 1500 1500 1550
5 5 5 5 5 0 0 0 5 0 0 50
2344
ISO-B
2344
ISO-B
2365
ISO-B
2367
ISO-B
2367
ISO-B
2367
ISO-B
2365
ISO-B
2344
ISO-B
2344
ISO-B
2344
ISO-B
2365
ISO-B
2365
ISO-B
2367
ISO-B
2367
ISO-B
2365
ISO-B
2344
ISO-B
2344
ISO-B
2344
ISO-B
2365
ISO-B
2367
ISO-B
2367
ISO-B
2367
ISO-B
2367
ISO-B
Forging die
9

Table 3 Tool steels for forging dies – characteristics and applications
Steel group Material number Code designation
to DIN
Nickel alloy die steels
Lever parts
10
2713 ISO-B * 55NiCrMoV 0,50-
0, 0
2714 ISO-B 55NiCrMoV7 0,50-
0, 0
2714 ISO-B mod. ** ~ 57NiCrMoV7-7
2744 ISO-B * 57NiCrMoV7-7 0,50-
0, 0
2766 ISO-B * 5NiCrMo1 0, -
0, 8
High alloy CrMoV hot working steels containing special carbide
2344 ISO-B X 0CrMoV5-1 0, 5-
0,
2360 ISO-B * X 8CrMoV8-1-1 0, 5-
0,50
2365 ISO-B CrMoV1 - 8 0, 8-
0, 5
2367 ISO-B X 8CrMoV5- 0, 5-
0, 0
2606 ISO-B * X 7CrMoW5-1 0, -
0, 0
* On request only
** For larger dimensions with optimum full quenching and tempering
DIN analysis
Figures in %
C Si Mn P S*** Cr Ni Mo V W
0,10-
0, 0
0,10-
0, 0
0, 5-
0,95
0, 0-
0,90
TYPICAL ANALYSIS
≤
0,0 0
≤
0,0 0
≤
0,0 0
≤
0,0 0
Forging dies Hammer head Forging die for 40 mto
hammer
0, 0-
0,80
0,80-
1, 0
1,50-
1,80
1,50-
1,80
0, 5-
0, 5
0, 5-
0,55
0,07-
0,1
0,05-
0,15
0,55 0, 5 0,95 0,015 0,00 1,10 ,00 0,75 0,1
0,15-
0, 5
0,15-
0, 0
0,80-
1, 0
0,70-
0,90
0,10-
0, 0
0, 0-
0,50
0,90-
1, 0
0, 0-
0,80
0, 0-
0, 0
0, 5-
0,50
0, 5-
0, 5
0,15-
0, 5
0, 0-
0,50
0, 0-
0, 0
≤
0,0 5
≤
0,0 5
≤
0,0 0
≤
0,0 0
≤
0,0 0
≤
0,0 0
≤
0,0 5
≤
0,0 5
≤
0,0 5
≤
0,0 0
≤
0,005
≤
0,0 0
≤
0,0 0
≤
0,0 5
0,90-
1, 0
1, 0-
1,50
,80-
5,50
7, 0-
7,80
,70-
, 0
,80-
5, 0
5,00-
5, 0
1,50-
1,80
,80-
, 0
0,70-
0,90
0, 0-
0, 0
1, 0-
1,50
1, 0-
1,50
,50-
,00
,70-
, 0
1, 0-
1, 0
*** Buderus ISO-B steels are melted only with a maximum of 0.00 % sulfur content
0,07-
0,1
0,85-
1,15
1, 0-
1,50
0, 0-
0,70
0, 0-
0, 0
0,15-
0, 0
1, 0-
1, 0

Material characteristic Important material data
Ni alloy die steel with good toughness in the hardness range
1100 - 1 00 N/mm =^ 5 - 85 HB
As 71 ISO-B, but with higher hardness retention and better through hardening
properties for hardnesses up to around 15 HB
Optimized composition for significantly improved through hardening, tempering
properties, thermal strength characteristics and increased wear resistance
compared to 71 ISO-B for large forging dies and press dies
As 71 ISO-B, but higher heat resistance, hardness retention
and wear resistance
Air quenching, very tough die steel for dynamic stress with short contact
times, can be used even for very large dies
Hot working steel with high heat resistance, hardness retention
and wear resistance
As ISO-B, but even better hardness retention and wear resistance, highly
temperature resistant, good nitriding qualities
Hot working steel with good toughness, suitable for high temperature stress
and alternating stress, tolerates water cooling
As ISO-B, but greater heat resistance and hardness retention,
high thermal endurance, good wear resistance
Hot working steel with very good heat resistance, high hardness retention and
good toughness, can be water cooled to a limited extent
Hammer head, 22 tonnes unit weight
Ac 1 Ac Ms Hardening
temperature
°C °C °C °C °C
Annealing
temperature
705 780 50 880 90 ,5
710 790 70 880 90 ,5
710 790 80 880 700 ,8
7 0 770 10 880 700 5,0
95 770 10 880 50 ,0
855 9 5 00 10 0 8 0 7,0
8 951 0 1080 8 0 5,0
790 875 50 10 0 780 ,0
785 985 0 10 0 780 ,8
810 885 00 10 0 800 8,0
Thermal conductivity
W
mK at 500 °C
Die holder
with inserts
11

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Buderus Edelstahl, a name that stands for the production and refinement
of high-grade special steels. Buderus Edelstahl is a global front
runner in this sophisticated sector. Outstanding quality, efficiency
and speed are as much a matter of course response for Buderus
Edelstahl GmbH as flexibility and service. More than 50 agents with
stockholding and service centres provide close customer support
and market coverage.
Legal notice: Buderus Edelstahl GmbH has taken the greatest care in compiling the information in this leaflet.
It is nevertheless possible that data may have changed in the meantime. Buderus Edelstahl GmbH disclaims
all liability or warranty as regards the accuracy, currency, correctness and completeness of the information
provided, and any consequences arising from the use of the information. The information provided is
merely indicative, and is binding only if it is expressly made a condition in a contract concluded with Buderus
Edelstahl GmbH. Buderus Edelstahl GmbH moreover reserves the right to make changes at any time without
notice. Buderus Edelstahl GmbH repudiates all liability for loss of any kind, including consequential loss,
arising in connection with use of the information provided. © Buderus Edelstahl GmbH, Wetzlar, 10 / 2006
We supply quality products that are used in automotive and drive
technology, in plant engineering and machine building, and in die
and mould making.
I Rolled billets
I Open die forgings from ingots weighing up to 150 tonnes
I Tool steels for mould and die making
I Special engineering steels for plant and gear engineering
Buderus Edelstahl GmbH
Vertriebssparte Stabstahl/Lagerservice
Buderusstr. 5
D- 557 Wetzlar
Tel.: + 9 (0) 1 / 7 - bis - 7
Fax: + 9 (0) 1 / 7 -
E-Mail: sv-l@buderus-steel.com
www.buderus-steel.com
11/0 /FX/B/H