锻造铸造焊接外文翻译.docx
- 文档编号:13336185
- 上传时间:2023-06-13
- 格式:DOCX
- 页数:14
- 大小:29.22KB
锻造铸造焊接外文翻译.docx
《锻造铸造焊接外文翻译.docx》由会员分享,可在线阅读,更多相关《锻造铸造焊接外文翻译.docx(14页珍藏版)》请在冰点文库上搜索。
锻造铸造焊接外文翻译
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
Casting、ForgingandWelding
1.Casting
Metalcastingisoneoftheoldestofallindustries,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,sandmouldsarecontainedinmetalmoldingboxesthathavefoursidesbutnotoporbottom.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(thedrawangle).
Agroovecalledagateiscutinthesandfacetoallowthechannelproducedbytheplugthatisoutsidethepatterntoconnectwiththeimpression.Themetalispouredthroughthischannel(calledtherunner),andthegatepreventsitfromdroppingstraightintotheimpressionanddamagingit.Thecross-sectionofthegateisslightlysmallerthanthatofchannelsothatafullrunnerwillalwayssupplymetaltothegateataslightpressure.
Finally,themouldisreassembled,carefullylocatingandsecuringthetwosections.Thetopsectionisknownasthecope,andthelowersectionisknownasthedrag.Thesandinthecopeisvented.Theseventsallowthesandtoberammedupmoretightlyattheearlierstageswithouttheriskofgasesbeingtrappedinthemoltenmetalandformingblowholesinthesolidmetal.Asand-feedinggate(alsocalledapouringorbowl)isaddedtomakeiteasiertopourthemetalintotherunner.Themoltenmetalispouredthroughtherunnerandtheairwillescapethroughtheriser.
Theimpressionwillbefilledwithmoltenmetalwhenitiscompletelyfilled.Gasescanescapethroughtherunnerandtheriser,whichalsoactasheaderstosupplytheimpressionwithmoremetaltocompensateforthecontractionofthemetalwhencoolinginthemoltenstate.
2.Forging
Forgingistheplasticworkingofmetalbymeansoflocalizedcompressiveforcesexertedbymanualorpowerhammers,presses,orspecialforgingmachines.Itmaybedoneeitherhotorcold.however,whenitisdonecold,specialnamesusuallyaregiventotheprocesses.Consequently,theterms“forging”usuallyimplieshotforgingdoneabovetherecrystallizationtemperature.
Modernforgingisadevelopmentformtheancientartpracticedbythearmormakersandtheimmortalizedvillageblacksmith.High-poweredhammersandmechanicalpresseshavereplacedthestrongarm,thehammer,andtheanvilandmodernmetallurgicalknowledgesupplementstheartskillofthecraftsmanincontrollingtheheatingandhandlingofthemetal.
Forgeabilityisthetermusedintheindustrytodenoteamaterialrelativeresistancetodeformationanditsplasticity.Whileconsiderabledisagreementexistsastopreciselywhatcharacteristicstheword“forgeability”shouldinclude,thetermasusedhereisdefinedasthetoleranceofametaloralloyfordeformationwithoutfailure,regardlessofforgingpressurerequirements.
Rawmaterialusedforforgingisgenerallybarorbilletstockhotrolledfromingotsmeltedinopen-hearth,electricarc,orvacuumarcfurnace.otherformsandshapessuchasrolledslabs,plats,andstockproducedbycontinuouscastingtechniquesareoccasionallyused.forcertaingrades,vacuumarcmeltingimpartsbetterforgeabilitythandoesconventionalarcmelting.However,themajorpurposeofvacuummeltingistheimprovementofmechanicalpropertiesandcleanliness,notforgingbehavior.
Equipmentbehaviorinfluencestheforgingprogresssinceitdeterminesthefeasibilityofforgingapartandaffectstherateofdeformationandthetemperatureconditions.
Thehammeristhemosteconomicaltypeofequipmentforgeneratingloadandenergynecessarytocarryoutaforgingprocess,providedthatthematerialbeingforgedcansupporthighdeformationvelocities.Itismostcommonlyusedhotforgingequipmentforrepeatedblowsonthesameworkpieceandcannotbeoverloaded.
Therearevarioustypesofhammers:
air-liftgravitydrophammers,powerdrophammers,powerdrophammers,Counterblowhammersect.Inasimplegravitydrophammertheupperramispositivelyconnectedtoaboard,abelt,achainorapiston.Whenforgingtheramisliftedtoacertainheightandthendroppedonthestockplacedontheanvil.Duringthedownstroke,therainisacceleratedbygravityandbuildsuptheblowenergy.Theupstroketakesplaceimmediatelyaftertheblow,theforcenecessarytoensurequicklift-upoftheramcanbe3to5timestheramweight.Theoperationprincipleofapower-drophammerissimilartothatofanairdrophammer.Duringthedownstroke,inadditiontogravity,theramisacceleratedbysteam,coldairorhotairpressure.Inanelectrohydraulicgravity-drophammer,theramisliftedwithoilpressureagainstanaircushion.Thecompressedairslowsdowntheupstrokeoftheramandcontributestoitsaccelerationduringthedownstroke.thus;theelectrohydraulichammeralsohasaminorpowerhammeraction.
Pressforgingemploysaslowsqueezingactionindeformingtheplasticmetal,ascontrastedwiththerapid-impactblowsofahammer.Hydraulicforgingpressisoperatedbylargepistonsdrivenbyhigh-pressurehydraulicorhydrometricsystem.Thesqueezingactioniscarriedcompletelytothecenterofthepartbeingpressed,thoroughlyworkingtheentiresection.Thesepressesaretheverticaltypeandmaybeeithermechanicallyorhydraulicallyoperated.Themechanicalpresses,whicharefasteroperatingandmostcommonlyused,rangeincapacityfrom5000to10000tons.
Intheforgingpressagraterproportionofthetotalworkputintothemachineistransmittedtothemetalthaninadrophammer.Themachineandfoundationabsorbmuchoftheimpactofthedrophammer.pressreductionofthemetalisfaster,andthecostofoperationisconsequentlylower.mostpressforgingsaresymmetricalinshape,havingsurfaces,whicharequitesmooth,andprovideaclosertolerancethanisobtainedbyadrophammer.however,dropforgingcanforgemanypartsofirregularandcomplicatedshapesmoreeconomically.Forging
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 锻造 铸造 焊接 外文 翻译
![提示](https://static.bingdoc.com/images/bang_tan.gif)