机械毕业设计英文外文翻译163钢.docx

机械毕业设计英文外文翻译163钢.docx

《机械毕业设计英文外文翻译163钢.docx》由会员分享，可在线阅读，更多相关《机械毕业设计英文外文翻译163钢.docx（7页珍藏版）》请在冰豆网上搜索。

机械毕业设计英文外文翻译163钢

英文原文:

Steels

Steelisoneofthemostvaluablemetalsknowntoman;approximately200milliontonscanbeproducedintheUnitedStatesannually.In1900,UScapacitywasbut21milliontons.Althoughtheprocessofsteelmakingisfamiliartomostengineers,areviewofthisprocesswouldbeappropriateatthistime.

Ironore,limestone,andcoalaretheprincipalrawmaterialsusedinmakingironandsteel.Cokeisproducedbyheatingbituminouscoalinspecialovens.Skipcarsgouptheskiphoistwithloadsofironore,coke,andlimestoneanddumpthemintothetopoftheblastfurnace.Hotairfromthestoveisblownintothefurnacenearthebottom.Thiscausesthecoketoburnattemperaturesupto3000°F.Theoreischangedintodropsofmoltenironthatsettletothebottomoftheblastfurnace.Thelimestonethathasbeenaddedjoinswithimpuritiestoformaslagthatfloatsontopofthepoolofliquidiron.Periodically,themoltenironisdrainedintoaladlefortransportingtoeithertheBessemerconverter,electricfurnaceoropen-hearthfurnace.Theslagisremovedseparatelysoasmottocontaminatetheiron.

Themakingofsteelfromironinvolvesafurtherremovalofimpurities.Regardlessofwhichprocessisusedformakingsteel-open-hearth,Bessemer-converter,orelectric-furnace-steelscrapisaddedalongwithdesiredalloyingelementsandtheimpuritiesareburnedout.

Liquidsteelremovedfromthefurnaceispouredintoingotmolds.Theingotsarethenremovedto“soakingpits”wheretheyarebroughttoauniformrollingtemperature.

Attherollingmill,thewhite-hotsteelpassesthroughrollsthatformtheplasticsteelintothedesiredshape:

blooms,slabs,orbillets.Thesethreesemifinishedshapesthengotothefinishingmillswheretheyarerolledintofinishedformsasstructuralsteel,platesandsheets,rods,andpipes.

Steelisthebasicandmostvaluablematerialusedinapparatusmanufacturedtoday.Itsapplicationisbasedonyearsofengineeringexperience,whichservesasaguideinchoosingaparticulartypeofsteel.Eachvariable,suchasalloy,heattreatment,andprocessesoffabricationhasitsinfluenceonthestrength,ductility,machinability,andothermechanicalproperties,andaffectsthetypeofsteelselected.Thefollowingbasicconceptsalsoassistindeterminingwhichsteelshouldbeused:

1.Themodulusofelasticityintensionfallswithintherangeof28×106to30×106lb/in2,regardlessofcompositionorform;therefore,sizesasdeterminedbydeflectionremainthesameregardlessofthesteelchosen.

2.Carboncontentdeterminesthemaximumhardnessofsteelregardlessofalloycontent.Therefore,thestrengthdesired,whichisproportionaltohardness,candeterminethecarboncontent.

3.Theabilityofthesteeltobeuniformlyhardenedthroughoutitsvolumedependsontheamountandkindofalloy.Thisismorecomplex,butdoesnotnecessarilychangethecalculationofthesizeofthepart.

4.Ductilitydecreasesashardnessincreases.

Thepreliminarychoiceofsteelforapartaswellasforotherfactors,suchasnotchsensitivity,shrinkage,blowholes,corrosion,andwear,issimplifiedwhenbasedontheaboveprinciples.Thefinalselectionismadebymatchingthematerialwiththeprocessofmanufactureusedinordertoobtaintheshape,surface,andphysicalrequirementsofthepart.Theselectionmaybemadefromamonglow-carbonsteels,low-alloysteels,high-carbonsteels,andhigh-alloysteels.

Steelisoneofthefewcommonmetalsthathasanendurancelimit.Youwillrecallthatfatigueisthefailureofamaterialduetorepeatedloading.Mostmetalsbecometiredastheyaresubjectedtostressoverandoveragain.Thestressamaterialcanwithstandunderconstantloadingismuchlessthanunderstaticloading.Assteeliscontinuallyloaded,itwillreachalowerlimitofstrength.Thispropertyisquitepronouncedinwireshapes.Commoncopperandaluminumwirecaneasilybebrokenbyflexingthewireinalocalspot.Normallyafterafewdozenflexes,thewirebreaks.Steelwire,however,isverytoughandflexingthewiresimplycoldworksthematerialmakingtheprocessfutilefortheunknowingpersontryingtobreakasteelwire.Atsomepointsteelwillresistweakeningduetorepeatedloading.Thisisknownasan“endurancelimit”.Theendurancelimitofsteelisaround60%ofitsoriginalstrength.

Thispropertyofhavinganendurancelimitmakessteelinvaluableforuseinstructuralapplicationslikebridges,springs,struts,beams,etc.Ofcourse,therearemanyfactorsthateffecttheendurancelimitofamaterial.Aprimaryfactoristhesurfacequalityofthematerialand/orthemanufacturingprocessusedtoproducethespecimen.

Fatigueisattributabletotheinitialmaterialmotbeinganidealhomogeneoussolid.Ineachhalfcycle,irreversibleminutestrainsareproduced.Fatiguefailureusuallydevelopsfrom:

1.Repeatedcyclicstressesthatcauseincrementalslipandcoldworkinglocallyinthematerial.

2.Gradualreductionofductilityofthestrainhardenedareasthatdevelopintocracks.

3.Anotchingeffectfromsubmicroscopiccracks.

Theendurancelimitsofsteelscreatesomeverydesirablephysicalproperties.Thesepropertiescanbedetrimentaltothemanufacturabilityofthematerial.Forinstance,inthecoldrollingofsteeltheendurancelimitcreatesalimitationontheamountofcoldworkingthatcanbeinputtoanypart.Afterthislimithasbeenreachedthematerialmustbeheatedaboveitscriticaltemperaturetopermitfurthercoldworking.

Plaincarbonsteelsrepresentthemajorproportionofsteelproduction.Carbonsteelshaveawidediversityofapplication,includingcastings,forgings,tubularproducts,plates,sheetsandwireproducts,structuralshapes,bars,andtools.Plaincarbonsteels,generally,areclassifiedinaccordancewiththeirmethodofmanufactureasbasicopenhearth,acidopenhearth,oracidBessemersteels,andbycarboncontent.

Theprincipalfactorsaffectingthepropertiesoftheplaincarbonsteelsarethecarboncontentandthemicrostructure.Themicrostructureisdeterminedbythecompositionofthesteel（carbon,manganese,silicon,phosphorus,andsulfur,whicharealwayspresent,andresidualelementsincludingoxygen,hydrogen,andnitrogen）andbythefinalrolling,forging,orheat-treatingoperation.However,mostoftheplaincarbonsteelsareusedwithoutafinalheattreatmentand,consequently,therollingandforgingoperationsinfluencethemicrostructure.

Carbonsteelsarepredonminantlypearliticinthecast,rolled,orforgedconditions.Theconstituentsofthehypoeutectoidsteelsarethereforeferriteandpearlite,andofthehypereutectoidsteelsarecementiteandpearlite.

Alloysteelisanalloyofironandcarboncontainingalloyingelements,oneormoreofwhichexceedsthefollowing:

manganese,1.65percent;silicon,0.60percent;copper,0.60percent;and/orspecifiedamountsofotheralloyingelements,includingaluminum,boron,andchromiumup3.99percent;cobalt,niobium,molybdenum,nickel,tungsten,vanadium,zirconium,orotherelementsaddedinsufficientquantitytogivethedesiredpropertiesofthesteel.

Sincetherearemoreelements,someexpensive,tobekeptwithinthespecifiedrangesinalloysteelthanarerequiredincarbonsteel,alloysteelrequiresmoreinvolvedtechniquesofqualitycontroland,consequently,ismoreexpensive.

Alloysteelcangivebetterstrength,ductility,andtoughnesspropertiesthancanbeobtainedincarbonsteel.Consequently,theengineershouldconsideralloysteelsIdesignssubjectgohighstressesand/orimpactloading.

Almostallalloysteelsareproducedwithfine-grainstructures.Asteelisconsideredtobefine-grainedifitsgrainsizeisrated5,6,7,or8.Number1grainsizeshows1.5grains/in.ofsteelareaexaminedat100diametersmagnification.Fine-grainsteelshavelesstendencytocrackduringheattreatmentandhavebettertoughnessandshock-resistanceproperties.Coarsegrainedsteelsexhibitbettermachiningpropertiesandmaybehardenedmoredeeplythanfine-grainedsteels.

Toselectthealloysteelthatisbestsuitedforagivendesign,theeffectsoftheprincipalalloyingelementsmustbetakenintoaccount.Theyareasfollows.

1.Nickelprovidestoughness,corrosionresistance,anddeephardening.

2.Chromiumimprovescorrosionresistance,toughness,andhardenability.

3.Manganesedeoxidizes,contributestostrengthandhardness,decreasesthecritical-coolingrate.

4.silicondeoxidizes,promotesresistancetohigh-temperatureoxidation,raisesthecriticaltemperatureforheattreatment,increasesthesusceptivityofsteeltodecarburizationandgraphitization.

5.Molybdenumpromoteshardenability,increasestensileandcreepstrengthsathightemperatures.

6.vanadiumdeoxidizes,promotesfine-grainedstructure.

7.Copperprovidesresistancetocorrosionandactsasstrengtheningagent.

8.Aluminumdeoxidizes,promotesfine-grainedstructure,andaidsnitriding.

9.boronincreaseshardenability.

Theterm“stainlesssteel”denotesalargefamilyofsteelscontainingatleast11.5percentchromium.Theyarenotresistanttoallcorrodingmedia.

Stainlesssteelcompeteswithnonferrousalloysofcopperandnickelonacorrosion-resistanceandcostbasisandwithlightmetalssuchasaluminumandmagnesiumonthebasisofcostandstrength-weightratio.Stainlesssteelhasanumberofalloycompositionsandtherearemanysupplies.Informationonitspropertiesandfabricationcanbeobtainedreadily.Soundtechniqueshavebeenevolvedforcasting,heattreating,forming,machining,welding,assembling,andfinishingstainlesssteel.Itwillbefoundthatthismaterialusuallywork-hardens（whichmake