钢材种类和变形的基础知识

BasicKnowledgeofSteelandPlasticMechanics基础钢和塑性变形知识Contents1.SteelMechanicalpropertiesWorldwidesteelgradesAdvancedhighstrengthsteel(AHSS)2.PlasticmechanicsSheetdeformationmodesForminglimitsYieldcriteria2Introductiontoelasticityandplasticity固体材料受外力作用产生变形，从变形开始到破坏一般要经历两个阶段：弹性变形(elasticdeformation)和塑性变形(plasticdeformation)。外力卸载后，弹性变形能够完全消失，而塑性变形不能消失。弹性变形和塑性变形的机理：材料原子之间的作用力平衡。位错(dislocation)理论。强化机制(workhardeningmechanism)。Dislocationmovement3UniaxialtensiletestGB/T228金属材料室温拉伸试验方法EN10002-1Metallicmaterials-Tensiletest-Part1:testmethod(inambienttemperature)Typicaltensiletestpiece4Engineeringstress-straincurve5Engineeringstress-straincurve6StrengthandDuctilityStrengthparametersEngineeringstressEngineeringstrainElongationReductionofareaDuctility7Truestress-straincurveTruestressTruestrain8Workinghardening(strainhardening)Strainhardeningexponent(n-value)9Influenceofstrain-hardeningexponent

n3n2n110Anisotropy(R-value)Widthstrain:εw=ln(w/w0)Thicknessstrain:εt=ln(t/t0)R=

εw/εtPlanaranisotropyratioNormalplasticanisotropyratio11StrainratesensitivityStrainrateStrainratesensitivityexponentStrainratesensitivityhasacrucialinfluenceontheresearchofcrashresistanceandhigh-speedstampingformability.12Worldwidesteelgrades13Worldwidesteelgrades14CommonsteeltypesandevolvingAHSStypesInterstitialfree(IF)steelsMildsteelsBakehardenable(BH)steelsIsotropic(IS)steelsCarbon-manganese(CM)steelsHigh-strengthlow-alloy(HSLA)steelsDualphase(DP)steelsTransformationinducedplasticity(TRIP)steelsComplexphase(CP)steelsMartensitic(Mart)steels15Strengtheningmechanism16HSLAsteel17GradesofHSLAsteelinEU18ApplicationofHSLAsteel19Dualphase(DP)steel20EUsteelgradesComparisonEuropeansteelgrades(Mildsteel,HSLA,Dual-Phase)Legend:ColdRolledHotRolledDualPhase

coldrolled

(valuesfromARCELOR)Notfornewproducts!:Availibility

tobeclarifiedFromClausUnruh21DimensionavailabilityAvailabilitycheckmaterialsEuropeversusUS–updateNov2006

(onlyacc.myinformation;mustbecheckedandconfirmedbyPurchasingdepartment)

Materialavailibilityofstandardmaterialsisgiven.

MaterialavailibilityofS460MCisdecreasingeveninEurope.

MaterialavailibilityofDualPhaseandotherspecialgradesmustcheckedforeachdimensionsFromClausUnruh22DimensionavailabilityAvailabilitycheckmaterialsEuropeversusChina–updateNov2006

(onlyacc.myinformation;mustbecheckedandconfirmedbyPurchasingdepartment)

Materialavailibilityofstandardmaterialsisgiven.

MaterialavailibilityofS460MCisdecreasingevenEurope.

MaterialavailibilityofDualPhaseandotherspecialgradesmustcheckedforeachdimensionsFromClausUnruh23StandardthicknessChinavs.JapanChinaJapan24HSLAsteelgradesoverviewOverviewsteelgrades:HSLA(highstrengthlowalloyed)Steelfamilycold

rolledhotrolledLegend:ExistinggradesafterstandardisationUseonlystandardHSLAsteel(worldwideavailable)

H240LAandS460MCwascancelledcausedbysourcingproblemsworldwide!FromClausUnruh25MildsteelgradesoverviewOverviewsteelgrades:MildsteelSteelfamilycold

rolledhotrolledLegend:ExistinggradesbeforestandardisationExistinggradesafterstandardisationOnly2gradesareallowed:

DC01/CS:softsteelforsimplelowstrengthpressparts

DC04/DDS:softsteelwithgooddeepdrawingproperties;forcomplexlowstrengthpressparts

Brandnamesandothermaterialdesignationswillnotbeaccepted.FromClausUnruh26DPsteelgradesoverviewOverviewsteelgrades:Dual-PhasesteelSteelfamilycold

rolledhotrolledLegend:(*)JapanesegradesnotexactlycomparableDP400andDP500arenotrelevantforseatstructures.DP1400indevelopment.StandardisationofDualPhasegradesisdifficult,causedbymissingEuropeanstandard.

Availabilityhastobeclarifiedforeachgradeanddimension.Purchasingdepartmentmustsupporttheprocess.FromClausUnruh27ProductsfromBaoSteelforautomobilestructuresMildsteels28ProductsfromBaoSteelforautomobilestructuresDPsteelsHotrolledmild&HSLAsteels29ProductsfromBaoSteelforautomobilestructuresColdrolledHSLAsteelsHotrolledHSLAsteels30VHSScategoryatArcelor31MetallurgyofVHSSatArcelor32ApplicationofVHSS33ApplicationofVHSS34Engineeringstress-straincurveofDPsteelHighertensilestrengthofDPsteel(largern-value)BetterstampingformabilityandcrashresistanceperformanceofDPsteel35n-valueofDPsteel36ApplicationofDPsteel37FEAresultsofDPsteel38FEAresultsofDPsteel39Sheetmetalformingprocessesblanking&piercingbendingBendinginafoldingmachineBendinginavee-dieSectionofasetofrollsinarollformerWipingdownaflange40SheetmetalformingprocessesflangingstretchingAshrinkflangewithbucklingAstretchflangewithcrackingFlangingacurvedsheetSectionbendingStretchingadomeinasheetAdomedpunchanddiesetforstretchingasheet41Sheetmetalformingprocesseshole-extrusionstamping(drawing)Typicalpartformedinastampingordrawdieshowingthediering,butnotthepunchorblankholderSectionoftoolinginadrawdieshowingthepunchandblankholder42SheetmetalformingprocessesToolingfordeepdrawingacylindricalcupToolingforforwardredrawingacylindricalcupTubeformingExpandingtheendofatubewithaflaringtoolReducingthediameterofatubebypressingitthroughasinkingdie43SheetmetalformingprocessesHydroformingashallowpartExpandingaroundtubetoasquaresectionbyhydroformingUsingcombinedaxialforceandfluidpressuretoformaT-jointThinningasheetlocallyusingacoiningtool44Sheetmetaldeformationmodes-stretchingstretching塑性变形局限在某一固定区域内。成形依靠材料表面积增大实现，因此变形区域材料厚度变薄。变形区域的应力状态是双向拉伸。材料不起皱，变形区域表面质量好。Strainstatus:biaxialtension试验方法：杯突评估指标：IE试验方法：极限拱顶高评估指标：LDH045Sheetmetaldeformationmodes-drawingdrawing(cupdrawing)坯料外部环形区域是变形区，坯料内部圆形区域不变形。在径向的应力是拉应力，在切向的应力是压应力。因此，坯料在径向可能出现破裂（拉裂），在切向可能出现起皱（压缩）。StrainstatusRadial:tensionTangential:compression试验方法：圆筒拉深评估指标：LDR46Sheetmetaldeformationmodes-bendingbending曲率发生变化的区域是变形区。坯料圆角和直边部分参与变形，变形过程和卸载过程很复杂。卸载后零件容易发生回弹，导致达不到尺寸精度。试验方法：V形弯曲评估指标：Rmin/t47Sheetmetaldeformationmodes-flangingShrinkflangingStretchflanging试验方法：扩孔评估指标：λ圆锥冲头平底冲头48Principalstrainstatusduringdeformationdrawingplanestrainstretching49ForminglimitsTestprocedureofmaterialforminglimits(forminglimitcurve,FLC)Forminglimitdiagram(FLD)50ApplicationofFLDAnalysisofsheetmetalformingprocessbasedonFLD51YieldinginplanestressPlanestressσ1,σ2≠0,σ3=0MaximumshearstressandmaximumshearstressplanesThereareonshearstressesonthefacesoftheprincipalelement.Onafaceinclinedatanyotherangle,bothnormalandshearstresseswillact.Onfacesofdifferentorientationitisfoundthattheshearstresseswilllocallyreachamaximumforthreeparticulardirections.Theyareinclinedat