焊接裂纹产生及预防

WhyDoWeldsCrack?焊缝为什么会开裂？DavidWang王秀伟Duringfabrication?生产中？Inservice?运行中？Whendidthecrackoccur?何时出现裂纹？Whereisthecrack?裂纹出现在哪里？LongitudinalCrack纵向裂纹TransverseCrack横向裂纹ThroatCrack焊喉处裂纹ToeCrack焊趾裂纹CraterCracksinAluminumWeld铝焊接中的弧坑裂纹UnderbeadCracks焊道下裂纹CenterlineCracking焊缝中心裂纹UnderbeadCracking焊道下裂纹TransverseCracking横向裂纹CenterlineCracking焊道中心裂纹CenterlineCracking焊道中心裂纹(eventhoughnotincenterofjoint)即使不在中间CenterlineCracking焊道中心裂纹Cause1:SegregationCracking原因1：偏析裂纹•Lowmeltingpointconstituentssegregatetothecenterlineduringsolidification在凝固时低熔点的元素聚集到中间LowMeltingPointIngredients低熔点的元素•Carbon(C)碳•Lead(Pb)铅•Zinc(Sn)锌•Copper(Cu)铜•Phosphorous(P)磷•Sulfur(S)硫SegregationCracking偏析裂纹Solutions:解决的方法•Use“good”steel使用“好”的钢材–Lowinlowmeltingpointconstituents减少低熔点的元素TWIHotCrackingSusceptibility:TWI热裂纹敏感指数UCS=230C+190S+75P+45Nb–12.3Si-5.4Mn–1UCS10“HighResistancetoCracking不易开裂”UCS30“StrongSusceptibilitytoCracking非常容易开裂”BasedonWELDMETALComposition基于母材的成分Linnert4thEdition,Volume1TWIHotCrackingSusceptibility:UCS=230C+190S+75P+45Nb–12.3Si-5.4Mn–1CrackingContributors裂纹支持元素TWIHotCrackingSusceptibility:UCS=230C+190S+75P+45Nb–12.3Si-5.4Mn–1CrackingResistors裂纹阻止元素SegregationCracking偏析裂纹Solutions:解决方法•Use“good”steel使用“好”的钢材–Lowinlowmeltingpointconstituents减少低熔点的元素–Avoid“freemachining”steelsforweldedapplications避免使用“不需机加工”的钢材SegregationCracking偏析裂纹Solutions:解决方法•Minimizealloypickup减少合金拾取–Minimizeadmixture减少熔和比–Minimizepenetration(minimizecurrentdensity{d=I/A})减少熔深（减少电流密度）1/4”FCAW-g1/4”FCAW-gSegregationCracking偏析裂纹Solutions:解决方法•Minimizealloypickup减少合金拾取–Minimizeadmixture减少熔和比–Minimizepenetration(minimizecurrentdensity{d=I/A})减少熔深（减少电流密度）–Mayrequirejointdetailchange或许需要改变坡口形式SegregationCracking偏析裂纹Solutions:解决方法•Minimizealloypickup减少合金拾取–Minimizeadmixture减少融合比–Minimizepenetration(minimizecurrentdensity{d=I/A})减少熔深（减少电流密度）–Mayrequirejointdetailchange或许需要改变坡口形式–Useof“buttering”techniques采用“预堆边”ButteringLayer预堆边SegregationCracking偏析裂纹Solutions:解决方法•Forsteelswithhighsulfur,increasethemanganesecontentoftheelectrode.对于含高硫的母材，增加焊丝的锰含量0.060.080.100.120.140.160.18Carbon,wt%605040302010RatioofmanganesetosulfurNoCrackingCrackingMn/S20:10.060.080.100.120.140.160.18Carbon,wt%605040302010RatioofmanganesetosulfurNoCrackingCrackingMn/S850(%C)-83Mn/S20:1SegregationCracking偏析裂纹•Cause1:原因lowmeltingpointconstituentssegregatetothecenterlineduringsolidification在凝固时低熔点的元素聚集到中间•Solutions解决方法–Use“good”steel使用“好”的母材–Minimizealloypickup减少合金的拾取–Forhighsulfur,usehigherMnelectrodes对于高硫母材，采用高锰焊丝“Popsicle”Cracking凝固裂纹•Cause2:原因Improperwidth-to-depthratioleadstosolidificationproblems不当的焊缝宽深比SOLIDIFIEDLIQUIDCRACKDepth(D)Width(W)SOLIDIFIEDLIQUIDCRACK“Popsicle”Cracking凝固裂纹•Cause2:原因Improperwidth-to-depthratioleadstosolidificationproblems不当的焊缝宽深比•Solutions解决方法–Useproperjointdetail使用正确的接头WD1.4W/D1.21.0AWSD1.1Figure3.2GroovePreparationRootOpeningGrooveAngleR=1/4a=45oR=3/8a=30oR=1/2a=20oAWSD1.1Figure3.2aRProperrootgeometry正确的打底焊道aR=toosmall太小Improperrootgeometry:不正确的焊道aR=small,butaisincreased小但夹角增加了Properrootgeometry正确的焊道aRImproperrootgeometry:不正确的焊道Randaarebothtoosmall夹角和间隙都太小aRProperrootgeometry正确的焊道aissmall,butRisincreased.夹角小了，但间隙增加了“Popsicle”Cracking凝固裂纹•Cause2:原因Improperwidth-to-depthratioleadstosolidificationproblems不正确的宽深比•Solutions解决方法–Useproperjointdetail使用正确的接头–Controlpenetration(currentdensity)控制熔深（电流密度）SurfaceProfileCracking表面成形裂纹•Cause3:–Concavesurfacecracksduringsolidification内凹的焊道表面在凝固时开裂SurfaceProfileCracking表面成形裂纹SurfaceProfileCracking表面成形裂纹SurfaceProfileCracking表面成形裂纹•Cause3:–Concavesurfacecracksduringsolidification内凹表面在凝固时开裂•Solution:解决方法–Makeconvexsurfaces焊成凸的焊缝•Lowercurrents小电流•Lowervoltages低电压•Shieldinggaschanges改变气体•Ifvertical,changetoverticalup立焊时采用向上焊CenterlineCracking焊道中心裂纹Cause1:SegregationCracking偏析Cause2:“PopsicleCracking”凝固Cause3:SurfaceProfile表面成形“HOTCRACKING热裂纹”UnderbeadCracking焊道下裂纹TransverseCracking横向裂纹“COLDCRACKING冷裂纹”UnderbeadCracking焊道下裂纹UnderbeadCracking焊道下裂纹•Cause:原因Excessivehydrogenandstressandasensitivebasematerial(HAZ)太高的氢含量，应力和敏感材料Hydrogen氢Stress应力SensitiveMaterial敏感材料UnderbeadCracking焊道下裂纹•Cause:原因Excessivehydrogenandstressandasensitivebasematerial(HAZ)太高的氢含量，应力和敏感材料•Solutions解决方法–Controlhydrogen控制氢含量Hydrogen氢Stress应力SensitiveMaterial敏感材料UnderbeadCracking焊道下裂纹•Cause:原因Excessivehydrogenandstressandasensitivebasematerial(HAZ)太高的氢含量，应力和敏感材料•Solutions解决方法–Controlhydrogen控制氢含量•Selectionoffillermetals焊材的选择•Storageandexposureoffillermetals存储和使用•Controlofbasemetalcleanliness母材的清洁•Maximizediffusionofhydrogen加快氢的扩散Maximizediffusionofhydrogen加快氢的扩散•Increasedpreheat增加预热•Increasedinterpasstemperature增加层间温度•Higherheatinput增加热输入•Thinnerweldlayers薄的焊道•Increasedtimebetweenpasses增加前后两道的时间•Slowercoolingafterwelding焊后缓冷•Postheat后热UnderbeadCracking焊道下裂纹•Cause:原因Excessivehydrogenandstressandasensitivebasematerial(HAZ)太高的氢含量，应力和敏感材料•Solutions解决方法–Controlhydrogen控制氢含量–ControlStress控制应力Hydrogen氢Stress应力SensitiveMaterial敏感材料UnderbeadCracking焊道下裂纹•Cause:原因Excessivehydrogenandstressandasensitivebasematerial(HAZ)太高的氢含量，应力和敏感材料•Solutions解决方法–ControlStress控制应力•Matchin