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1、Relationshipsbetweentensileandfracturemechanicspropertiesandfatiguepropertiesoflargeplasticmouldsteelblocks大型塑料模具钢模块的拉伸、断裂机制和疲劳性能之间的关系DonatoFirraoa,∗,PaoloMatteisa,GiorgioScavinoa,GrazianoUbertallia,MariaGiuseppinaIencob,MariaRosaPinascob,EnricaStagnob,RiccardoGerosac,Bar
2、baraRivoltac,AntonioSilvestric,GiuseppeSilvac,AndreaGhidinidaDip.ScienzadeiMaterialieIngegneriaChimica,PolitecnicodiTorino,IT-10129,Torino,ItalybDip.ChimicaeChimicaIndustriale,Universit`adiGenova,IT-16146,Genova,ItalycDip.Meccanica,PolitecnicodiMilano,IT-23900,Lecco,Italy
3、dLucchiniSidermeccanicaS.p.A.,IT-24065,Lovere(BG),ItalyReceived31March2006;receivedinrevisedform5July2006;accepted7July2006摘要生产汽车塑料部件——比如保险扛和仪表盘，的模具通常是由大型预硬化钢模块加工而来。由于它们的尺寸原因，热处理过程中混合着各种微观结构，它们随着与淬火表面距离不同而不断变化，并且在这一过程中的断面强韧性变化和疲劳性能变化并不为人们所知，但此时这两种性能通常比完全淬火和退火态时低。服役过程中模具对于
4、缺陷（如由不恰当的焊层沉积物引起的微裂纹）和应力的反应取决于模具钢的性能，这就相应地依赖于热处理和所得到的微观组织。在一个大模块上进行了逐点拉力测试，夏比V型缺口冲击韧性测试，断面韧性测试和回转弯曲疲劳强度测试。高周疲劳通过台阶法进行研究。试样从模块的不同深度选取。另外，力学性能，断面形态和微观结构之间的关系也将被研究。关键词：塑料模具钢；金相学；机械性能；断裂韧性；高周疲劳；断口金相AbstractMouldsforplasticautomotivecomponentssuchasbumpersanddashboardsareusual
5、lymachinedfromlargepre-hardenedsteelblocks.Duetotheirdimensions,theheattreatmentproducesmixedmicrostructures,continuouslyvaryingwiththedistancefromthequenchedsurface,atwhichfracturetoughnessandfatiguepropertiesarenotwellknownandgenerallylowerthanthosecorrespondingtoafully
6、quenchedandtemperedcondition.Theresponseofthemouldtodefects(forexample,microcracksduetoimproperweldbeddeposition)andstressesduringservicedependsonsteelproperties,thatinturndependupontheheattreatmentandthemicrostructure.Apointwisedeterminationofthetensile,CharpyV-notched,f
7、racturetoughnessandrotatingbendingfatiguepropertieswascarriedoutinalargeblock.Highcyclefatiguewasinvestigatedbythestair-casemethod.Thesampleswereobtainedfromdifferentdepthsoftheblooms.Therelationshipbetweenmechanicalproperties,fracturesurfacesmorphologyandmicrostructurewa
8、salsoinvestigated.Keywords:Plasticmouldsteel;Metallography;Mechanicalproperties;Fracturetoughnes
