【模具与数控专业英语】教学内容1103

UnitOneTheDie&MoldMaterialsandHeatTreatment模具与数控专业英语11.3HeatTreatmentofDie&MoldMaterials

模具与数控专业英语1.3.1ThePurposesofHeatTreatmentThemainpurposeofheattreatmentfordie-makingandmold-makingmaterialsistocontrolthepropertiesofaspecificmetaloralloythroughthealterationofthestructureofthespecificmetaloralloybyheatingittodefinitetemperaturesandcoolingatvariousrates．Thiscombinationofheatingandcontrolledcoolingdeterminesnotonlythenatureanddistributionofthemicroconstituents，whichinturndeterminetheproperties，butalsothegrainsize［2］.2模具与数控专业英语Heattreatingshouldimprovethealloyormetalfortheserviceintended．Someofvariouspurposesofheattreatingareasfollows：l.Toremovestrainsaftercoldworkingsuchasforging,rolling.2.Toremoveinternalstressessuchasproducedbydrawing,bending,extrudingorwelding.3.Toincreasethehardnessofthematerialandwear-resistingproperties.3模具与数控专业英语4.Toimprovemachinability.5.Toimprovethecomprehensiveperformanceofmaterialonpurpose,suchasnormalizing.6.Tosoftenthematerial，asinannealing.7.Toimproveorchangepropertiesofamaterialsuchascorrosionresistance，heatresistance，orothersasrequired.4模具与数控专业英语1.3.2TypesofHeatTreatmentHeattreatmentofferrousmaterialsinvolvesseveralimportantoperationswhicharecustomarilyreferredtoundervariousheadings,suchasannealing,normalizing,tempering,hardening,casehardening,spheroidizing,stressrelieving,surfacetreatmentsandsoon.

Annealing---Theprocessofannealingconsistsofheatingthesteeltoanelevatedtemperatureforadefiniteperiodoftimeand，usually，coolingitslowly．

5模具与数控专业英语Annealingisdonetoproducehomogenizationandtoestablishnormalequilibriumconditions，withcorrespondingcharacteristicproperties．Inviewthatdieandmoldsteelisgenerallypurchasedintheannealedcondition,sometimesitisnecessarytoreworkadieormoldthathasbeenhardened，andthedieormoldmustthenbeannealed．Forthistypeofanneal,thesteelisheatedslightlyaboveitscriticalrangeandthencooledveryslowly.6模具与数控专业英语

Normalizing---Involvesheatingthematerialtoatemperatureofabout55～100℃abovethecriticalrangeandcoolinginstillair．Thisisabout55℃overtheregularhardeningtemperature．Thepurposeofnormalizingisusuallytorefinegrainstructuresthathavebeencoarsenedinforging．Withmostofthemedium－carbonforgingsteels，alloy，normalizingishighlyrecommendedafterforgingandbeforemachiningtoproducemorehomogeneousstructures，andinmostcases，improvedmachinability［3］.7模具与数控专业英语High－alloyair－hardenedsteelsarenevernormalized，sincetodosowouldcausethemtohardenanddefeattheprimarypurpose．

Tempering---Thisistheprocessofheatingquenchedandhardenedsteelsandalloystosometemperaturebelowthelowercriticaltemperaturetoreduceinternalstressessetupinhardening．

Hardening---Thisistheprocessofheatingtoatemperatureabovethecriticalrange,andcoolingrapidlyenoughthroughthecriticalrangetoreducetoappreciablyhardenthesteel．8模具与数控专业英语

CaseHardening---Theadditionofcarbontothesurfaceofsteelpartsandthesubsequenthardeningoperationsareimportantphasesinheattreating．Theprocessmayinvolvetheuseofmoltensodiumcyanidemixtures，packcarburizingwithactivatedsolidmaterialsuchascharcoalorcoke,gasoroilcarburizing,anddrycyaniding．9模具与数控专业英语

Spheroidizing--isaformofannealingwhich，intheprocessofheatingandcoolingsteel，producesaroundedorglobularformofcarbide—thehardconstituentinsteel．Steelsarenormallyspheroidizedtoimprovemachinability.Thisisaccomplishedbyheatingtoatemperatureto749～760℃forcarbonsteelsandhigherformanyalloytoolsteels，holdingatheatonetofourhours，andcoolingslowlyinthefurnace.10模具与数控专业英语

Stress

Relieving--Thisisamethodofrelievingtheinternalstressessetupinsteelduringforming，coldworking，andcoolingafterweldingormachining．Itisthesimplestheattreatmentandisaccomplishedmerelybyheatingto649～732℃followedbyairorfurnacecooling．Largediesareusuallyroughedout，thenstress－relievedandfinish－machined．Thiswillminimizechangeofshapenotonlyduringmachiningbutduringsubsequentheattreatingaswell．11模具与数控专业英语Weldedsectionswillalsohavelocked－instressesowingtoacombinationofdifferentialheatingandcoolingcyclesaswellastochangesincrosssection．Suchstresseswillconsiderablemovementinmachiningoperations．12模具与数控专业英语

Surface

Treatments---Duringthepast20years，severalprocesseshavebeenintroducedtoobtainenhancedsurfacehardnessofsteels．Someofthemhavedevelopedfromcasecarburizingand

nitriding，toobtainfasterprocessingtimeswithbetterenvironmentalcontrolofandimprovedproperties．Varioussaltbathprocesseshavebeenusedandnowawiderangeofnewmethodsisavailable．13模具与数控专业英语Inthediecastingindustrysurfacetreatmentsareappliedtosteelstoimprovethepropertiesofnozzles，ejectorpins,coresandshotsleeves，toprovidemaximumresistancetoerosion，pittingandsoldering．Treatmentofdiecavitieshasreceivedonlylimited“acclaim，becausethecomplexthermalpatterns