Remote Laser Welding of AA6xxx Fusion-TM Material - LATEST2
Remote Laser Welding of AA6xxx Fusion-TM Material - LATEST2
Remote Laser Welding of AA6xxx Fusion-TM Material - LATEST2
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<strong>Remote</strong> <strong>Laser</strong> <strong>Welding</strong> <strong>of</strong> <strong>AA6xxx</strong>Multi-Layer <strong>Fusion</strong> <strong>TM</strong> <strong>Material</strong>Novelis Innovation Center Sierre, SwitzerlandCyrille BezençonPierre-David AndréCorrado Bassi24.11.2011
Presentation content► Introduction►►<strong>Remote</strong> <strong>Laser</strong> welding & cracking issue with <strong>AA6xxx</strong>Multi-Layer <strong>Fusion</strong> Solution► Hot-Cracking modeling►►►Hot-Cracking Susceptibility, HCSSolid-fraction calculation vs. alloy compositionApplication <strong>of</strong> the model to weldable <strong>Fusion</strong>► <strong>Laser</strong> remote welding results►►<strong>Remote</strong> laser welding trials on various geometryImproved processing window2
Issue with 6xxx Aluminum Alloyduring remote laser welding
<strong>Remote</strong> <strong>Laser</strong> <strong>Welding</strong>► Scanner Technology►►►Versatile and quick processImproved “accessibility”High-Speed and cost effective► Drawback►►No filler metalNo gas protection<strong>Remote</strong> <strong>Laser</strong> <strong>Welding</strong>[Google source]4
<strong>Welding</strong> Issue with 6xxx Aluminium AlloysHot-cracking sensitiveness during laser welding► 6xxx alloys are known to be difficult material for welding►►The columnar grain structure in the welded zone linked with the slightamount <strong>of</strong> Mg, Si and/or Cu lead to high hot-cracking susceptibility (HCS)<strong>Welding</strong> can only be successfully performed with filler material and/orlow welding speedAA6014 <strong>Laser</strong> welded without fillerBarker etched500 m5
Novelis Solution for <strong>Remote</strong> <strong>Laser</strong> <strong>Welding</strong><strong>Fusion</strong> Technology with specific clad for improve weldability►►►►►►Novelis <strong>Fusion</strong> Alloy 8840 is weldable without filler metalNo hot cracking in the weld<strong>Remote</strong> <strong>Laser</strong> <strong>Welding</strong> compatible (no gas protection)Cost effectiveMaintains all advantages <strong>of</strong> 6xxx monolithic alloysFully approved for automotive applications6
<strong>Fusion</strong> Casting Process : Clad / Core simultaneous casting7
Hot-Cracking Modeling
Hot-tearing / hot-cracking►DefinitionHot tears are cracks which occur duringsolidification►Two conditions leading to hot tearing1. Stress in the mushy zone2. Shrinkage during solidification isnot (enough) compensated byfeeding with residual liquid►Parameters influencing hot tears:Composition and Solidification intervalTemperature gradients and solidif. rateStress state and strain rateMorphology <strong>of</strong> solidification (columnar,equiaxed, dendritic, planar, …)9
HCSHot-Cracking modeling► Alloy sensitivity analysis► HCS : Hot-Cracking Susceptibility► Low hot-cracking risk► Small solidification interval(i.e. pure alloy)► High eutectic volume fraction(i.e. close to eutectic composition, few backdiffusion)► High hot-cracking risk► Large solidification interval with fewresidual liquid between dendrites (lowcoherency temperature)Binary Al-MgSource : ASM <strong>Welding</strong> Handbook, Vol.6 200710
Hot-Cracking modeling : Criteria and equation► Criteria►►Some liquid must flow between dendrites tocompensate for solidification shrinkage andthermal strainIf permeability is too small or strain too large, liquidpressure will be reduced below a critical cavitationpressure, p c , leadings to pores or cracks.► Interdendritic liquid flow►Darcy laws through the mushy zone, with a mushpermeability, K, given by the Carman-Kosenyequation► Pressure calculation►Pressure reduction at the root <strong>of</strong> a columnardendritic front from Rappaz et al.Criteria :p = p + p > p c[Feurer 1976]with[Carman-Koseny permeability]11DeformationSolidificationshrinkage[Rappaz et al. 1999]
Hot-Cracking Susceptibility as a function <strong>of</strong> alloy compositionCracking Criterion< p cAlloy ParametersSolid fraction, f s (T)Liquidus temperature, T lCoherency temperature : T cohSolidification ParametersThermal Gradient : GSolidification speed : VDeformation rate : ’12
Solid fraction, fs (T)A (T) ~ HCSSolid fraction evolution and A parameter .vs. temperature►Solid fraction, fs(T)A2 : 2Si-0.2Mg-0.2Cu-0.6Mn-0.3Fefs(T)TcohTliqA►multiphase thermodynamiccalculation (MTData) taking intoaccount Al, Fe, Si, Mg, Cu, Mn1.00.90.8T cohT liq1.E+049.E+038.E+03►Gulliver-Scheil’s rule (no back-diff.)► Coherency temperature, T coh ,equivalent to 96% solid0.70.60.50.40.37.E+036.E+035.E+034.E+033.E+03►Hot-Cracking assessmentHCS ~ A integral(High A = Severe cracking risk)0.22.E+030.11.E+030.00.E+00540 560 580 600 620 640 660Temperature [°C]Solid fraction, f s (T)Liquidus temperature, T lCoherency temperature : T coh13
<strong>Laser</strong> <strong>Remote</strong> <strong>Welding</strong> <strong>of</strong>Multi-Layer <strong>Fusion</strong> Solution
<strong>Remote</strong> welding <strong>of</strong> various geometryCollaboration Trumpf - Novelis: Tests <strong>of</strong> various geometriesI-Naht - overlapStumpf -Naht - Butt WeldKehl-Naht - Edge OverlappI - Naht Kanten - EdgeT- Naht - T JointBlech-Pr<strong>of</strong>il - Extrusion-Sheet15
<strong>Remote</strong> welding <strong>of</strong> various geometryKehl-Naht and Butt welding gives good welds with <strong>Fusion</strong>New <strong>Fusion</strong> 6xxxMonolithic Standard AA6014 : Ac-170 / Ac-170Kehl-NahtNew <strong>Fusion</strong> 6xxxMonolithic Standard AA6014 : Ac-170 / Ac-170Butt-<strong>Welding</strong>16
<strong>Remote</strong> <strong>Laser</strong> Processing Window►►►Minimum Flange DistanceHigh-speed weldingMaximum allowed gap
ottomtop<strong>Laser</strong> processing windowMinimum Flange Weld Distance & Alloy Combination (<strong>Fusion</strong>, Monolithic)<strong>Remote</strong> welding on various alloycombination with reduced flange width(middle weld to edge distance) :3 mm6 mm10 mm►<strong>Fusion</strong>/<strong>Fusion</strong>►Ac-170/Ac-170►<strong>Fusion</strong>/Ac-170 and Ac-170/<strong>Fusion</strong>Trials configuration :►I-Naht configuration with a fixed gap <strong>of</strong> 0.1mm►►Speed adjusted for each alloy combinationNo adjustment for start/end <strong>of</strong> the weld20x5-pt_backside.jpg20x5-pt_backside.jpg18
DPIStructureMonolithic 6xxx : Ac-170 - 10 mm from edgeMonolithic Ac-170/Ac-170 is cracking at 100 mm from edgeTop side23x5-pt.jpgBack side23x5-pt_backside.jpgN°23N°23- Cracks in the weld, at grain boundary- Columnar grain on the weld border19
DPIStructure<strong>Fusion</strong> / <strong>Fusion</strong> - 10 mm from edge - good weldTop sideBack side21x5-pt_backside.jpg21- No Cracks observed- Smaller and more equiaxed grain20
DPIStructure<strong>Fusion</strong> / <strong>Fusion</strong> - 6 mm from flange - good weldTop sideBack side31x5-pt_backside.jpgCoreWeldCladNo crack observed21
Novelis <strong>Fusion</strong> - Flange <strong>Remote</strong> <strong>Welding</strong> Possible > 5 mm2.556 7.510 mm22
6170/<strong>Fusion</strong><strong>Fusion</strong>/<strong>Fusion</strong><strong>Fusion</strong>/61706170/6170toptoptopbottomtopbottombottombottomProcessing window for Monolithic-<strong>Fusion</strong> SheetCombination6 mm flange weld is possible with <strong>Fusion</strong> & <strong>Fusion</strong>-Monolithic combination10 mm6 mm3 mm20x5-pt_backside.jpg20x5-pt_backside.jpgN°22-22x5-pt.jpg20x5-pt_backside.jpg21x5-pt_backside.jpg22x5-pt_backside.jpg31x5-pt_backside.jpg31x5-pt.jpg30x5-pt_backside.jpg30x5-pt.jpg32x5-pt.jpg32x5-pt_backside.jpg35x5-pt.jpg33x5-pt_backside.jpg34x5-pt.jpg34x5-pt_backside.jpg35x5-pt_backside.jpg25x5-pt.jpg23x5-pt_backside.jpg23x5-pt.jpg24x5-pt_backside.jpg24x5-pt.jpg25x5-pt_backside.jpg23
<strong>Welding</strong> Speed [m/min]<strong>Fusion</strong> Novelis 8840 - Extreme <strong>Remote</strong> <strong>Laser</strong> Processing WindowInvestigation <strong>of</strong> speed and joint gap2220Crack free weld with <strong>Fusion</strong> alloy can beachieved up to :Speed <strong>of</strong> :Gaps <strong>of</strong> :22 m/min0.4 mmThis is not <strong>of</strong> direct use for production butshow the potential robustness <strong>of</strong> weld in realenvironment or by technical issues inassembly12100 0.3 0.4 0.5 0.6 0.7Gap [mm]24
ConclusionsAn analytical model has been used for the evaluation <strong>of</strong> the hot-crackingsusceptibility, HCS, as a function <strong>of</strong> the alloy (Al, Mg, Mn, Fe, Cu, Si)AlloycompositionSolidFraction(MTData)Integral AcalculationHCSevaluationThis model show a good correlation with the new <strong>AA6xxx</strong> <strong>Fusion</strong> <strong>TM</strong> claddedmaterial where <strong>Remote</strong> <strong>Laser</strong> <strong>Welding</strong>, without filler, become possible.Monolithic AA601 with a HCS<strong>of</strong> 3.5 = High Cracking Risk<strong>Fusion</strong> alloy with a HCS< 1 = Low Cracking Risk25
Thanks to :University Stuttgart – IFSW - <strong>Laser</strong> TrialsAxel Hess and Dr. Rudolf WeberTRUMPF <strong>Laser</strong> und Systemtechink GmbHDr. R.Brockmann, H. Melbert, Dr. T. Harrer, D. Mock
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