锻造铸造模具类外文文献翻译中英文翻译外文翻译.docx
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锻造铸造模具类外文文献翻译中英文翻译外文翻译.docx
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锻造铸造模具类外文文献翻译中英文翻译外文翻译
附录A英文原文
A.1FORGING
Bulkdefirnnationofmetalsreferstovariousprocesses,suchasforging,rolling,orextruding,wherethereisacontrolledplasticfloworworkingofmetalsintousefulshapes.Themostwellknownoftheseprocessesisforgingwheredeformationisaccomplishedbymeansofpressure,impactblows,oracombinationofboth.
HammerForging
Hanunerforgingconsistsofstrikingthehotmetalwithalargesemiautomatichammer.Ifnodiesareinvolved,theforgingwillbedependentmainlyontheskilloftheoperator.Ifclosedorimpressiondiesareused,oneblowisstruckforeachofseveral(liecavities.A-gain,productivityandqualitydependtoalargedegreeontheskillofthehanimeroperatorandthetooling.
PressForging
Pressforgingischaracterizedbyaslowsqueezingaction.Again,openorcloseddiesmaybeused.Theopendiesareusedchieflyforlarge,simple-geometrypartsthatarelatermachinedtoshape.Closed-dieforgingrelieslessonoperatorskillawlmoreonthedesignofthepreformandforgingdies.2Asanexampleoftheversatilityoftheprocess,newerdevelopmentshavemadeitpossibletoproducebevelgearswithstraightorhelicalteeth.Rotationofthedie(luringpenetrationwillpressbevelgearswithspiralteeth.
Open-dieForging
Open-dieforgingisdistinguishedbythefactthatthemetalisnevercompletelyconfinedasitisshapedbyvariousdies.Mostopen-dieforgingsareproducedonflat,V,orswagingdies.Roundswaging(liesandVdiesareusedinpairsorwithaflatdie.Thetop(lieisattachedtotheramofthepress,andthebottomdieisattachedtothehammeranvilor,inthecaseofpressopen-dieforging,tothepressbed.
Astheworkpieceishammeredorpressed,itisrepeatedlymanipulatedbetweenthediesuntilhotworkingforcesthemetaltothefinaldimensions,as-showninFig.1.Afterforging,thepartisrough-andfinished-machined.Asanexampleoftheamountofmaterialallowedformachining,a6.5in.diametershaftwouldhavetobeforgedto7.4in.dianieter.
Inopen-dieforgingofsteel,aruleofthumbsaysthat50lboffallingweightisrequiredforeachsquareinchofcrosssection.
Impression-dieForging
Inthesimplestexampleofimpression-dieforging,twodiesarebroughttogether,andtheworkpieceundergoesplasticdeformationuntilitsenlargedsidestouchthesidewallsofthedie(Fig.2).Asmallamountofmaterialisforcedoutsidethedieimpression,formingflashthatisgraduallythinned.Theflashcoolsrapidlyandpresentsincreasedresistancetodeformation,effectivelybecomingapartofthetool,andhelpsbuildupl)ressUreinsidethebulkofthework-piecethataidsmaterialflowintounfilledimpressions.
Closed-dieforgings,aspecialformofimpression-dieforging,doesnotdependontheformationofflashtoachievecompletefillingofthe(lie.Thusclosed-dieforgingisconsiderablymoredemandingondiedesign.Sincepressingisoftencompletedinonestroke,carefulcontroloftheworkpieeevolumeisnecessaiytoachievecompletefillingwithoutgeneratingextremepressuresinthediesfromoverfilling.
ExtrusionForging
Aswithupsetting,extrusionforgingisoftenaccomplishedbycoldworking.Threeprincipaltypesofmetaldisplacementbyplasticflowareinvolved.Backwardandforward,tube,andimpactextrusionareshowninFig.3.Themetalisplacedinacontainerandcorn-pressedbyarammovementuntilpressureinsidethemetalreachesflow-stresslevels.Theworkpiececompletelyfillsthecontainer,andadditionalpressurecausesittoleavethroughanorificeandformtheextrudedproduct.
Extrudedproductsmaybeeithersolidorhollowshapes.Tubeextrusionisusedtoproducehollowshapessuchascontainersandpipes.Reverse-impactextrusionisusedformassproductionofaluminumcans.Theramhitsaslugofmetalinthedieathighimpact,usually15timestheyieldstrengthofthemetal,whichcausesittoflowinstantaneouslyupthewallsofthedie.Othercommonhollowextrusionproductsareaerosolcans,lipstickcases,flashlightcases,andvacuumbottles.Secondaryoperations,suchasheading,threadrolling,dimpling,andmachining,areoftenneededtocompletetheitems.
Generallysteelimpactsarelimitedto2.5timesthepunchdiameter.Hydraulicpressesareusedforloadsofover2000tonsbecausetheyhaveagreatervariationinstrokelength,speed,andothereconomicadvantages.Tolerancesvarywithmaterialsariddesign,hutproductionrunscallingfor0.002-to0.005-in,toleranceareregularlymade.
RollForging
Rollforginginitssimplestformconsistsofaheatedbilletpassingbetweenapairofrollsthatdeformitalongitslength(Fig.8-4).Comparedtoconventionalrollingprocesses,therollsarerelativelysmallindiameterandserveasanarborintowhichtheforgingtoolsaresecured.Theactivesurfaceofthetooloccupiesonlyaportion(usuallyhalf)oftherollcircumferencetoaccommodatethefullcrosssectionofthestock.
Thereductionofthecrosssectionobtainableinonepassislimitedbythetendencyofthematerialtospreadandformanundesirableflashthatmaybeforgedintothesurfaceasadefectinthesubsequentoperations.Theworkpieceisintroducedrepeatedlywith
rota-tionbetweenpasses.
RingRolling
Ringrollingoffersahomogeneouscircumferentialgrainflow,easeoffabricationandmachining,andversatilityofmaterialsize.Manu-factureofarolledringstartswithashearedblank,whichisforgedtoapancake,punched,andpierced.
Thereisnolimittothesizeoftherolledrings,rangingfromroller-bearingsleevestoFig.4Rollforgingrings25ftindiameterwithfaceheightsof80in.Variousprofilesmayberolledbysuitablyshapingthedriven,idlingrolls.
CAD/CAMinForging
CAD/CAMisbeingincreasinglyappliedtofrging.Usingthethree-dimensionaldescriptionofamachinedpart,whichmayhavebeencomputerdesigned,itispossibletogeneratethegeometryoftheassociatedforging.Thustheforgingsectionscanbeobtainedfromacommon(laiRbase.Usingwell-knowntechniques,forgingloadsandstressescanbeobtainedandflashdimensionscanbeselectedforeachsectionwheremetalflowisapproximatedasrodimensional(planestrainoraxisymmetric).Insomerelativelysimplesectiongeomethes,computersimulationcanbeconductedtoevaluateinitialguessesonpreformsections.Oncethepreformgeometryhasbeendevelopedtothedesigner¡¯ssatisfaction,thisgeometricdatabasecanutilizedtowriteNCpartprogramstoobtaintheNCtapesordisksformachining.
A.2HEATTREATMENTOFMETAL
Annealing
Thewordannealhasbeenusedbeforetodescribeheat-treatingprocessesforsofteningandregainingductilityinconnectionwithcoldworkingofmaterial.Ithasasimilarmeaningwhenusedinconnectionwiththeheattreatingofallotropicmaterials.Thepurposeoffullannealingistodecreasehardness,increaseductility,andsometimesimprovemachinabilityofhighcarbonsteelsthatmightotherwisebedifflculttocut.Thetreatmentisalsousedtorelievestresses,refinegrainsize,andpromoteuniformityofstructurethroughoutthematerial.
Machinabilityisnotalwaysimprovedbyannealing.Thewordmachinabilityisusedtodescribeseveralinterrelatedfactors,includingtheabilityofamaterialtobecutwithagoodsurfacefinish.Plainlowcarbonsteels,whenfullyannealed,aresoftandrelativelyweak,offeringlittleresistancetocutting,butusuallyhavingsufficientductilityandtoughnessthatacutchiptendstopuliandtearthesurfacefromwhichitisremoved,leavingacomparativelypoorqualitysurface,whichresultsinapoormachinabilityrating.Forsuchsteelsannealingmaynotbethemostsuitabletreatment.Themachinabilityofmanyofthehigherplaincarbonandmostofthealloysteelscanusuallybegreatlyimprovedbyannealing,astheyareoftentoohardandstrongtobeeasilycutatanybuttheirsoftestcondition.
Theprocedureforannealinghypoeutectoidsteelistoheatslowlytoapproximately60
abovetheAc3line,tosoakforalongenoughperiodthatthetemperatureequalizesthroughoutthematerialandhomogeneousausteniteisformed,andthentoallowthesteeltocoolveryslowlybycoolingitinthefurnaceorburyingitinlimeorsomeotherinsulatingmaterial.Theslowcoolingisessentialtotheprecipitationofthemaximumferriteandthecoarsestpearlitetoplacethesteelinitssoftest,mostductile,andleaststrainedcondition.
Normalizing
Thepurposeofnormalizingissomewhatsimilartothatofannealingwiththeexceptionsthatthesteelisnotreducedtoitssoftestconditionandthepearliteisleftratherfineinsteadofcoarse.Refinementofgrainsize,reliefofinternalstresses,andimprovementofstructuraluniformitytogetherwithrecoveryofsomeductilityprovidehightoughnessqualitiesinnormalizedsteel.Theprocessisfrequentlyusedforimprovementofmachinabilityandforstressnlieftoreducedistortionthatmightoccurwithpartialmachiningoraging.
Theprocedurefornormalizingistoaustenitizebyslowlyheatingtoapproximately
abovetheAc3orAccm3temperatureforhypoeutectoidorhypereuteetoidsteels,respectively;providingsoakingtimefortheformationofaustenite;andcoolingslowlyinstillair.NotethatthesteelswithmorecarbonthantheeutectoidcompositionareheatedabovetheAominsteadoftheAcusedforannealing.Thepurposeofnormalizingistoattempttodissolveallthecementiteduringaustenitizationtoeliminate,asfaraspossible,thesettlingofhani,brittleironcarbideinthegrainboundaries.Thedesireddecompositionproductsaresmallgrained,finepearlitewithamin
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