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机械制造专业英语毕业考核任课老师：吴海生班级：11303姓名：陈利永学号：11021650ReadingComprehension(1)HeatTreatmentofDieSteelsAlthoughalloysteelscontainelementssuchaschromium,molybdenumandvanadium.Twoconstituentsareessentialforheattreatment:iron,termedferriteinmetallography,andcarbon,whichcombineswithirontoformcementite,thehardintermetalliccompoundFe3C.Thesetwoconstituentsformaeutectoidstructureknownaspearlitewhenthesteeliscooledslowlyenoughtoreachequilibrium,butbyrapidcoolingthesteelishardened.Whensuchaquenchedsteelistempered,structureswithmechanicalpropertiesintermediatebetweenthoseoftheslowlycooledandthequenchedconditionsareformed.Inrecentyearstherehasbeenagreaterunderstandingofthecomplexstructuralchangestakingplaceduringheattreatment,withthehelpofphasetransformationdiagrams.Useofthesediagramscanleadtobettercontroloftheheattreatmentcyclewhichinturnwillensurethatoptimumpropertiesandmaximumdielifeareachieved.SurfaceTreatmentsforSteelsDuringthepast20years,severalprocesseshavebeenintroducedtoobtainenhancedsurfacehardnessofsteels.Someofthemhavedevelopedfromcasecarburizingandnitriding,toobtainshorterprocessingtimeswithbetterenvironmentalcontrolandimprovedproperties.Varioussaltbathprocesseshavebeenusedandnowawiderangeofnewmethodsisavailable.Inthediecastingindustrysurfacetreatmentsareappliedtosteelstoimprovethepropertiesofnozzles,ejectorpins,coresandshotsleeves,toprovidemaximumresistancetoerosion,pittingandsoldering..Treatmentofdiecavitieshasreceivedonlylimitedacclaim,becausethecomplexthermalpattern,producedonlargediecomponentsleadtostresseswhicharesufficientlyhightobreakthroughthethinsurfacetreatedlayers,leadingtoprematurefailure.Experienceindropforginghasalsoindicatedthatsurfacetreatmentsoftheirdieshavenotbeenparticularlysuccessful.Thermochemicaltreatmentsarcappliedtodiecastingdiecomponents;thesurfacechemistryofthesteelismodifiedbytheintroductionofnitrogen,carbonandsometimesotherelements;theprocessesareoi'themaintypeslistedbelow.l.Nitriding.2.NitrocarburizingsuchasTufftride,SulfinuzandSuraulf.3.MetallizingsuchasboronizlngandtheToyotadiffusionprocess.4.Carburizingandcarbonitriding.译文：模具钢的热处理虽然合金钢包含元素如铬，钼和钒。热处理的两种必要成分：铁，称为铁素体的金相，和碳，与铁相结合形成渗碳体，硬的金属化合物Fe3C。这两个成分形成的结构称为珠光体共析钢时的冷却得足够缓慢达到平衡，但快速冷却钢硬化。当这样的淬火钢回火，机械性能的缓慢冷却和淬火条件之间的中间结构的形成。在最近几年有了更深入的了解的复杂的结构的变化发生在热处理过程中，借助于相位变化图。使用这些图可以导致更好的热处理周期，这反过来将确保最佳性能和最大的模具寿命达到控制。钢的表面处理在过去的20年里，一些工艺被引入用来提高钢的表面硬度。其中有一些是从表面渗碳和渗氮的开发，以获得更好的环境控制和改进的性能，缩短处理时间。各种各样的盐浴工艺已被使用，现在更广泛的新方法是有效的。在压铸行业表面处理的钢喷嘴性能的提高，顶针，芯和镜头套筒，以提供最大的抗点蚀和侵蚀，焊接。模腔的处理只获得了有限的好评，因为复杂的热模式，对大型模具元件引起的压力太大突破处理层的薄的表面，导致过早的失败。在落锤锻造经验也表明它们的模具表面处理也不是特别成功。热化学处理电弧应用于压铸模零件；钢的表面化学改性是通过引入氮，碳和其他元素的过程有时；博爱的主要类型如下。1.渗氮。2。氮碳共渗盐浴软氮化渗硫等，并suraulf。3。金属如boronizlng和丰田扩散过程。4。渗碳和碳氮共渗。(2)LocatingPrinciplesToinsuresuccessfuloperationofaworkholdingdevice,theworkpiecemustbeaccuratelylocatedtoestablishadefiniterelationshipbetweenthecuttingtoolandsomepointsorsurfacesoftheworkpiece.Thisrelationshipisestablished'oylocatorsintheworkholdingdevicewhichpositionandrestricttheworkpiecetopreventitsmovingfromitspredeterminedlocation.'Theworkholdingdevicewillthenpresenttheworkpiecetothecuttingtoolintherequiredrelationship.Thelocatingdeviceshouldbesodesignedthateachsuccessiveworkpiece,whenloadedandclamped,willoccupythesamepositionintheworkholdingdevice.Variousmethodshavebeendevisedtoeffectivelyrestrictthemovementofworkpieces.Thelocatingdesignselectedforagivenworkholdingdevicewilldependonthenatureoftheworkpiece,therequirementsofthemetal-removingoperationtobeperformed,andotherrestrictionsontheworkholdingdevice.译文：为确保夹紧装置的成功操作，工件必须准确定位在刀具和工件表面的点建立一个明确的关系，这种关系在夹紧装置中建立oy定位器，来定位和限制工件以防它脱离预定的位置，这种夹紧装置将提供所需的刀具在工件的关系。定位装置应设计,每一个工件,当加载和夹紧时,工件夹紧装置将占据相同的位置。各种方法已经制定有效地限制工件的运动。定位设计选择对于一个给定的工件夹紧装置将取决于工件的性质,metal-removing操作执行的要求,和其他限制工件夹紧装置。