锻造、铸造、焊接外文翻译1

毕业设计(论文)外文翻译学生姓名：系别：机械工程系专业：机械设计制造及其自动化班级：学号:译文出处：ScienceandTechnologyEngl-ishforMechanicalEngineering毕业设计(论文)参考文献译文Casting、ForgingandWelding1.CastingMetalcastingisoneoftheoldestofallindustries,bothancientandmedievalhistoryofferingexamplesofthemanufactureanduseofcasting.Fromsimpleaxeheadspouredfromcopperinopenmouldssome5000yearsage,castinginthepre-Christianworlddevelopedtoapointatwhichelaboratebronzestatuarycouldbeproducedintwo-pieceandcoredmoulds.Bytheendofthemedievalperiod,decoratedbronzeandpewtercastinghadbeguntobeusedinEuropeanchurchanddomesticlife.ThewidespreadadoptionofcastironasengineeringmaterialawaitedthesuccessofAbrahamDarbyin1790insmeltinginthecokeblastfurnace;thispavedthewayforthemassiveuseofcastironinconstructionduringtheyearsfollowingtheindustrialrevolution.Manyfoundriessprangupaftertheindustrialrevolution,thevastmajoritybeingforthemanufactureofthecastironthenbeingusedasastructuralmaterial.Thequantityproductionofironcastingsinthenineteenthcenturywasnotmatchedbyauniversaladvanceinqualityandtheengineeringuseoftheproductsencounteredmoreseriousrisksinanon-ductilematerial.Despitetheskillofthemolderinproducingcomplexforms,therewaslittlechangeinthemetallurgicalandengineeringsituationuntilthemodernerabroughtabetterunderstandingofthefactorsdeterminingquality.Withmoderntechniquesofprocesscontroltherudimentaryjudgmentoftheoperatorcouldgivewaytoobjectivemeasurementsofmetaltemperature,moldingmaterialpropertiesandotherproductionvariables.Theseimprovementshavebeenappliednotonlytocastironbuttoawiderangeofcastalloys.Therearefourbasiccastingmethods:sand-casting,die-casting,investment-casting,andcentrifugalcasting.Sand-castingisthemostwidelyusedmethodemployedinfoundry.Inthisprocess,sandmouldsarecontainedinmetalmoldingboxesthathavefoursides毕业设计(论文)参考文献译文butnotoporbottom.Duringthemoldingoperationtheboxesarelocatedtogetherbypinssothattheycanbeseparatedtoremovethepattern,andreplacedinthecorrectpositionbeforethemetalispouredin.Theboxesareclampedtogether,orthecope(topsection)weighteddownwhenpouringtopreventthecopefrom“floatingaway”fromthedrag(lowersection)whenthemouldisfullofmoltenmetal.Thesequencewhenmoldingthesimpletwo-partmouldtocastabracketisillustratedasfollows.Atthefirststagethepatternisseatedonthemouldingboard.Thepatterniscoveredwithfacingsand,whichisaspeciallypreparedsandofgoodquality,whichcantakeacleanandsmoothimpression,andcanresisttheheatfromthemoltenmetalthatwillbeincontactwithit.Thefacingsandisbackedupwithmoldingsand,whichisoldfacingsandfrompreviousmoulds.Themoldingsandiscarefullyrammedupsothatitisfairlytightaroundthepatterntoproduceagoodsolidmould,yetpermeableenoughtoallowthegasesproducedduringcastingtoescape.Thesandisfinallyleveledoff.Atthesecondstagethemouldwiththepatternstillinpositionisinverted;theexposedsandlightlycoveredwithpartingsand,andtheexposedpatternwithfacingsand.(Thepartingsandhasnocohesion,andisintroducedtopermitacleanseparationwhenthemouldisopeneduptoremovethepattern.)Thesecondmoldingboxislocatedinpositiononthefirstboxandfilledwithmoldingsand.Twoormoreplugsareintroducedwhenthesecondboxisbeingfilled(theseareremovedlater,leavingchannelsinthesand).Oneoftheseplugsispositionedtoonesideofthepattern.Thesandisrammedupandleveledoff.Now,atstage3,toallowthepatterntoberemoved.Thisisdonebyscrewingabarwithathreadedendintoasuitableinsertinthepattern,dampingthesandaroundthepattern,andgentlyrappingthebarinalldirectionssothatthepatterncanbecarefullywithdrawn.Tofacilitatetheremovalofthepatternwithoutscuffingthesidesoftheimpression,allsurfacesthatlieinthedirectionofpatternremovalareinclinedslightlybyasmallamount(thedraw毕业设计(论文)参考文献译文angle).Agroovecalledagateiscutinthesandfacetoallowthechannelproducedbytheplugthatisoutsidethepatterntoconnectwiththeimpression.Themetalispouredthroughthischannel(calledtherunner),andthegatepreventsitfromdroppingstraightintotheimpressionanddamagingit.Thecross-sectionofthegateisslightlysmallerthanthatofchannelsothatafullrunnerwillalwayssupplymetaltothegateataslightpressure.Finally,themouldisreassembled,carefullylocatingandsecuringthetwosections.Thetopsectionisknownasthecope,andthelowersectionisknownasthedrag.Thesandinthecopeisvented.Theseventsallowthesandtoberammedupmoretightlyattheearlierstageswithouttheriskofgasesbeingtrappedinthemoltenmetalandformingblowholesinthesolidmetal.Asand-feedinggate(alsocalledapouringorbowl)isaddedtomakeiteasiertopourthemetalintotherunner.Themoltenmetalispouredthroughtherunnerandtheairwillescapethroughtheriser.Theimpressionwillbefilledwithmoltenmetalwhenitiscompletelyfilled.Gasescanescapethroughtherunnerandtheriser,whichalsoactasheaderstosupplytheimpressionwithmoremetaltocompensateforthecontractionofthemetalwhencoolinginthemoltenstate.2.ForgingForgingistheplasticworkingofmetalbymeansoflocalizedcompressiveforcesexertedbymanualorpowerhammers,presses,orspecialforgingmachines.Itmaybedoneeitherhotorcold.however,whenitisdonecold,specialnamesusuallyaregiventotheprocesses.Consequently,theterms“forging”usuallyimplieshotforgingdoneabovetherecrystallizationtempera