铸造和铸造过程外文文献翻译中英文翻译材料加工铸造外文翻译.docx

铸造和铸造过程外文文献翻译中英文翻译材料加工铸造外文翻译.docx

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铸造和铸造过程外文文献翻译中英文翻译材料加工铸造外文翻译

铸造和铸造过程外文文献翻译、中英文翻译、材料加工铸造外文翻译

外文原文

Castinganditsprocesses

Introduction

ManufacturingprocesscanbeclassifiedintotwogeneralgroupsknownasprimaryandsecondaryprocessesTheprimaryprocessesnamelycastingforgingcoldheadingcoldextrudingbrakeformingandsoonarethosethatconvertrawmaterialintoshapesTheseformingmethodsincludebothhotandcoldworkingprocessesandingeneralwillstillrequirefurtherfinishingoperationsinordertoobtainanendproduct

ThesecondaryprocessesarethosethatbringtheparttothedimensionsandsurfacefinishspecifiedOnemayalsoincludeinthesecondaryprocessessuchoperationsasheattreatingandsurfacetreatmentsforcorrosionresistancehardnessandappearanceSecondaryprocessesareplanningturningmillingdrillingboringreamingbroachinggrindinghoninglappingpolishingandspecialmethodsofmetalremovalsuchaselectrochemicalmachiningOperationslikescrewcuttingtappingthreadmillinggearcuttingandsoonaresecondaryprocessesthataremerelyadaptationsofoneoftheaforementionedprocessesthataremerelyadaptionofoneoftheaforementionedprocesses

AcompletediscussionoftheseproceduresisbeyondthescopeofthistextThereforewewillconfineourselvestosuccinctdescriptionsofthemostprominenttechniques

12Castings

CastingsareidentifiedbythetypeofmoldortheforcerequiredtoyfillthemoldMoldsareeitherpermanentorexpendableThepatternofsandshellandplastermoldshowevercanbeusedrepeatedlyformakingnewmoldsAsthemetalcoolsittakestheshapeofthecavityThebasiccastingmethodsaredescribedbelow

Sandcastings

1ThegreensandprocessisoneinwhichmostbondedsandspackedaroundawoodormetalpatternThepatternisthenremovedandmoltenmetalispouredintothecavityWhenthemetalsolidifiesthemoldisbrokenandthecastingisremovedAlmostanymetalcanbeusedwithvirtuallynolimitastothesizeorshapeofthepartThemethodpermitscastingcomplexcomponentsatalowtoolingcostandisthemostdirectroutefrompatterntocasting

SomemachiningisalwaysnecessarywiththegreensandprocessandlargecastingshaveroughsurfacefinishClosetolerancesaredifficulttoachieveandlongthinprojectionsshouldnotbecastItispossiblehowevertodesignforbossesundercutsandinsertsTheminimumcoreholediameteradvisablearealuminum31614inandtheminimumsectionthicknessesadvisablearealuminum316incooper332iniron332inmagnesium5332inandsteel1412in

2ThedrysandprocessissimilartothegreensandprocessexceptthatcoreboxesareusedinplaceofpatternsThismethodisusuallylimitedtosmallerpartsthanmethod1Thesandisbondedwithasettingbinderandthecoreisthenovenbakedat300400toremovethemoisture

3ThecarbendioxidesandprocessisoneinwhichthesandmoldsarebondedwhitsodiumsilicatesolutionsandsetbyforcingcarbondioxidegasthroughthesandThistypeofmoldisstrongandpermitstheproductionofbetterdimensionallycontrolledcastingsthaneithermethod1or2

4Thecoresandmoldprocessisonewherethemoldsareputtogethercompletelyfromovenbakedcoressetwithorganicbinderssuchasoilordextrines

ShellMoldCastingThisisaprocesswherethemoldsaremadebycoatingthesandwithathermosettingplasticThemoldisthensupportedontheoutsaidbysandorshotandmoltenmetalispouredWhenthemetalhassolidifiedthemoldisbrokenawayfromthefinishedcasting

ShellmoldingproducescastingwithsmoothsurfacesuniformgrainstructurehighdimensionalaccuracyrapidproductionrateandminimalamountoffinishingoperationsTheminimumsectionthicknisscastableis11614inbutsectiondifferenceswheretheimum–minimumratioisgreaterthan5to1shouldbeavoidedBossesundercutsandinsertsareeasilycastandtheminimumcoredholediameteris1814inThemethodisrelativelycostlyislimitedtofewmetals

Full-MoldCastingAprocessinwhichagreensandorcold-settingresinbondedispackedaroundafoamedplasticpatternforexamplepolystyreneTheplasticpatternisvaporizedwiththepouringofthemoltenmetalintothemoldAnimprovedcastingsurfacecanbeobtainedbyputtingarefractorytypeofcoatingonthepatternsurfacebeforesandpackingThepatterncanbeonepieceorseveralpiecesdependinguponthecomplexityoftheparttobecast

TheplasticpatternsarehandledeasilyTheydonotrequireanydraftandproducenoflashonthecastingForsmallquantityproductionthismethodcanbeexpensivedependinguponthesizeandcomplexityofthecastingTheminimumrecommendedsectionthicknessis01inandtheimumsectionthicknessisunlimitedBossesundercutsandinsertspresentnoprobleminthistypeofcastingTheminimumcoredholediameteris14in

PermanentMoldCastingsTheseareformedbyamoldthatcanbeusedrepeatedlySomeapplicationshavereportedasmanyas25000castingsbeingmadefromthesamemoldUsuallythemoldrequiressomeredressingafterabout3000usesThemoldsaremachinedofmetalforexamplegrayironforcastingnonferrousmetalsandcastitonsMachinedgraphitemoldsareusedtocaststeel

ThismethodproducescastingsthathaveagoodsurfacefinishaswellasagoodgrainstructurelowporosityandhighdimensionalaccuracyTheinitialmoldcostisrelativelyexpensivebutcastingsweighingaslittleasseveralouncestocastingsarelimitedtorelativelysimpleshapesandformsTheimumrecommendedsectionthicknessisabout20inTheminimumthicknesshoweverdependsuoonthematerialbeingcastasfollows316inforiton33218inforaluminum532informagnesiumand332–516inforcopperTheminimumcastableholesare31614inindiameter

DieCastingAprocessusedextensivelyinthequantityproductionofintricatelyshapedzincalumimumleadandmagnesiumalloysThemethodislimitedinusewithtinandcopperalloys

Castingsareformedbyforcingmoltenmetalunderpressuresof1500-25000psiintoanaccuratelymachinedsteeldieThesteeldiewhichiswatercooledisheldtogetherbyahydraulicpressuntilthemetalcastingssolidifiesToeasetheejectionofthecastpartsalubricantissprayedonthedieformingsurfaceandtheejectionpinsForsmalldiecastcomponentsmultiplecavitydiesareused

ThesurfacefinishoftheresultingcastingsisquitesmoothandhasexcellentdimensionalaccuracyAlthoughthecostofproductionisrelativelycheaptheinitialdiecostishighDiecastingislimitedtononferrousmetalsandbythesizeofthepartthatcanbecastTheimumwallsectionthicknessisusuallyrestrictedto316inbutcertainlytonogreaterthan050in

PlasterMoldCastingThesearemadebypouringanonferrousalloyforexamplealuminumcopperorzincalloyintoaplastermoldwhichisthenbrokentoremovethesolidifiedcastingThecastingsproducedbythisprocessaresmoothhavehighdimensionalaccuracylowporosityandcanbemadeinmanyintricateshapesThemethodhoweverhasdisadvantagesinthatislimitedtononferrousmetalssmallcastingsandalsorequiresarelativelylongtimetomakethemoldsTheminimumwallsectionthicknessis0040-0060inforacastareathatislessthan2sqinForlargercastareastheminimumwallthicknessincreasedaccordingly

TheshowprocessdevelopedwithinthelastdecadeisacostpromisingmethodItemploystheuseofplastermoldsThisprocedureproducescastingswithfinedetailandexcellentdimensionalaccuracyandsurfacefinish

CeramicMoldCastingThisprocessusesamoldmadeofaceramicpowderbinderandgellingagentThemoldcanalsobemadeofaceramicfacingreinforcedwithasandbackingThemethodisrestrictedtocastingintricatepartsrequiringfinedetailclosetolerancesandsmoothfinishesTheminimumwallthicknessrecommendedis0025-0050inThereishowevernolimittotheimumwallthickness

InvestmentCastingThesearemadewhenpartsaredesiredthatareintricateinshapehaveexcellentsurfacefinishandrequireahighdegreeofdimensionalaccuracyInadditionthismethodofcastingpermitstheuseofavarietyofmetalalloysanddoesnothaveInadditionthismethodofcastingpermitstheuseofavarietyofmetalalloysanddoesnothaveanymetalflashingtoberemovedfromthefinishescasting

ThetechniqueofinvestmentcastingrequirescarefulworkmanshipandexpensivepatternsandmothsTheminimumcastablewallthicknessisabout0025-0050inandtheimumthicknessshouldnotexceed3in

CentrifugalCastingThisisamethodofcastingashapebypoutingthemoltenmetalintoarotatingfladkcontainingthemoldThemoldsaremadeofsandmetalorgraphitedependingonthemetalcastandarerotatedabouttheiraxialcenterseitherinahorizontalorverticalposition

RelativelylargediameterandbulkycomponentsaremadearepipegunbarrelshollowshaftsmachinerydriverollslongsleevestubingandsoonWherethediametertolengthratioisratherlargetherotationalaxiscanbeverticallymountedmoldsthemethodiscalledsemmicentrifugalcastinganditisusedtomakepartssuchaswheelsturbosuperchargerdiaphragmsdisksflywheelsandsoonFigure1-5-2showsaschematicsectionofasemicentrifugalcastingofacoredflywheel

GenerallythemethodofcentrifugalcastingisexpensiveandisalsolimitedintheshapeswhichcanbecastHoweverthecastingsmadebythismehodareverysoundandhavegooddimensionalaccuracyItshouldalsobenotedthatthismethodistheonlywaytoobtainalargecylindricalpart

ContinuousCastingThisisamethodwherebyamoltenmetaliscontinuouslygravityfedfromaladleintoaningotmoldofadesiredshapewhichisopenatbothendsAs