机械专业英语董建国第13章

TEXTREADINGMATERIALUnit13TEXTForging,StampingandRollingIndropforging,apieceofmetal,roughlyorapproximatelyofthedesiredshape,isplacedbetweendiefaceshavingtheexactformofthefinishedpiece,andforcedtotakethisformbydrawingthediestogether.Thismethodiswidelyusedforthemanufactureofpartsbothofsteelandbrass.Largeingotsarenowalmostalwaysforgedwithhydraulicpressesinsteadofwithsteamhammers,sincetheworkdonebyapressgoesdeeper.Fig.13-1ForgingmachinerMetalintheformofhot-rolledorcold-rolledsheetsorstripsmaybeformedintomanyshapesbyforcingthesheetintotheimpressionsinmetaldies.Thisprocessisknownasstamping,orpressingofmetals,andinvolvesmanydifferentoperations,suchasbending,drawing,punching,etc.Theseoperationsaresuccessfullycarriedoutthroughtheproperdiedesignandproperoperationofthepressinwhichthediesareplaced.Sheetsorstripsofsteel,brass,copper,aluminium,orothermetalareplacedbetweendies,andaslowactionofthepowerpressbringsthediestogether,forcingthemetaltoassumetherequiredshape.Rollingistheprocessofshapingmetalinamachinecalledrollingmill.Ingotsofmetalarerolledbyforcingthembetweentworollersrotatinginoppositedirections,thuspressingthemetalintotherequiredshape.Iftherollershavenogroovesontheirsurfaces,themetalisrolledintotheformofasheetorplate.Iftherollershavegroovesofacertainshape,themetalwilltaketheformofthesegrooves,thusitmaybeshapedintotheformofbarsorrods.Therearetwokindsofrolling:hotrollingandcoldrolling.Beforecoldrolling,thescalecoveringthesurfaceofthehot-rolledobjectshouldberemoved.Coldrollingproducesahighersurfacefinishingsheetandgivesitaveryexactsize.Theprocesshasinnumerableadvantages.Manyshapesmaybemanufacturedinquantitiesatarapidrateandatarelativelylowcost.LEARNTOSPEAKMissCandy: Hello,Mr.Smith.Nicetomeetyou!Mr.Smith: Hi.MissCandy.Nicetomeetyou,too.MissCandy: Whatareyoudoing?Mr.Smith: Iampreparingforsomeweldingexperiments.MissCandy: Iknowyourmajorisweldingengineering.Couldyoutellmehowmanykindsofweldingmethodthereareincommonuse?Mr.Smith: Therearefourkinds.MissCandy: Whatarethey?Mr.Smith:Theyareoxyacetylenewelding,arcwelding,spotweldingandforgedweld.MissCandy: Howdotheweldingwork?Mr.Smith:Weldingisthejoiningoftwometalpiecesbysofteningwithheatandthenpressing,hammering,orfusingthemtogether.MissCandy: Howdoesthearcweldingworkindetail?Mr.Smith:Arcweldingistheheatingoftwopiecesofmetaltobeweldedbyelectricity.Thisheatisthehottestthatcanbeobtainedforengineeringpurposes;itisabout7,232degreesfahrenheit.Theendsarethusmeltedtogether,makingaweldedjoint.MissCandy: I’mreallyverygratefultoyou.Mr.Smith:Notatall.NEWWORDSANDPHRASESdie [daI] n.冲模，锻模draw [drC:] vt.拉伸ingot [5IN^Bt] n.铸锭，钢锭press [pres] vt.压，冲压 n.冲压，压力机hydraulic [haI5drC:lIk] adj.水力的，液压的roll [rEJl] vt.轧制，滚轧 n.卷轴，轧辊rolling [5rBlIN] n.轧制，滚轧roller [5rEJlE(r)] n.轧辊sheet [Fi:t] n.张，片，薄钢板strip [strIp] n.条钢，带钢，狭条impression [Im5preF(E)n] n.凹膛，压痕，型腔stamp [stAmp] v.冲压stamping [5stAmpIN] n.冲压punch [pQntF] n.冲床 vt.冲孔，穿孔punching [pQntF] n.冲孔，穿孔assume [E5sju:m;(?@)E5su:m] vt.呈现，表现 为……形式rotate [rEJ5teIt;(?@)5rEJteIt] v.回转，转动rotation [rEJ5teIF(E)n] n.回转，转动bar [bB:(r)] n.条钢，型钢scale [skeIl] n.氧化皮 vt.测量，起氧化皮innumerable [I5nju:mErEb(E)l] adj.无数的welding [5weldIN] n.焊接oxyacetylene [BksIE5setIli:n] adj.氧乙炔的fuse [fju:z] v.熔合fahrenheit [5fArEnhaIt] adj.华氏温度计的 n.华氏温度计dropforging 模锻，落锤锻finishedpiece 完成件steamhammer 蒸汽锤hydraulicpress 液压机，水压机oxyacetylenewelding 氧—乙炔焊arcwelding 电弧焊spotwelding 点焊forgedweld 锻焊NOTES1．Largeingotsarenowalmostalwaysforgedwithhydraulicpressesinsteadofwithsteamhammers,sincetheworkdonebyapressgoesdeeper.由于压力机所做的功能够传递得较深，因此，目前大铸锭几乎总是由液压机代替蒸汽锤进行锻造的。“insteadof”是复合介词，作“代替”、“而不是”解。“sincetheworkdonebyapressgoesdeeper”是原因状语从句，表示主句中的某一动作或状态所发生的原因。“donebyapress”是过去分词短语作定语，修饰名词“thework”。EXERCISES1．DiscussthefollowingquestionsinEnglish:(1) Whatisproduced,ifthemetalisrolledwithrollershavingnogroovesontheirsurface?(2) Howmanykindsofrollingarethere?Namethem.Whichkindproducesmoreexactsize?(3) Howmanykindsofwayswhichproducearoughwork?Whatarethey?2．UseEnglishforreplacingChineseoruseEnglishforreplacingEnglish.(1)模锻(2)冲压一个零件(3)轧制薄钢板(4) Weldawork-piecebyoxyacetylenewelding(5) Punchaholeofawork-piece(6) Awork-piecehavebeenforged3．Placea“T”aftersentencesthataretrueandan“F”afterthosethatarefalse.(1) Allferrousandnon-ferrousmetalsmaybeforged.()(2) Indropforging,thediefacesmusthavetheexactformofthefinishedpieces.()(3) Ingotsofmetalarerolledbyforcingthembetweentworollersrotatinginthesamedirection,thuspressingthemetalintotherequiredshape.()(4) Allmethodsofforgingarebasicallyrelatedtohammeringorpressingofmetal,themaindifferencebetweentwobeingthespeedofpressureapplication.()(5) Pressingcausesmetaltomoveastheresultofarapidlyappliedforce.()READINGMATERIAL

SolderingandBrazingThereareanumberofmethodsofjoiningmetalarticlestogether,dependingonthetypeofmetalandthestrengthofthejointwhichisrequired.Solderinggivesasatisfactoryjointforlightarticlesofsteel,copperorbrass,butthestrengthofsolderedjointisratherlessthanajointwhichisbrazed,rivetedorwelded.Thesemethodsofjoiningmetalarenormallyadoptedforstrongpermanentjoint.Solderingistheprocessofjoiningtwometalsbyathirdmetaltobeappliedinthemoltenstate.Solderconsistsoftinandlead,whilebismuthandcadmiumareoftenincludedtolowerthemeltingpoint.Oneofthemostimportantoperationsinsolderingisthatofcleaningsurfacestobejoined,thismaybedonebysomeacidcleaner.Althoughtheoxidesareremovedbythecleaningoperation,anewoxidecoatingformsimmediatelyaftercleaning,thuspreventingthesoldertounitewiththesurfaceofthemetal.Fluxisusedtoremoveandpreventoxidationofthemetalsurfacetobesoldered,allowingthesoldertoflowfreelyandunitewiththemetal.Zincchlorideisthebestfluxtouseforsolderingmostferrousandnonferrousmetals,forsolderingaluminumstearineorvaselineistobeusedasfluxes.Thesolderingcopperisapieceofcopperattachedtoasteelrodhavingahandle.Solderingcoppersaremadeindifferentlengths,formsandweights.Thequalityofsolderingdependstoagreatdegreeontheformandsizeofthesolderingcopper.Twopartsmaybeperfectlysolderedonlywhenthesurfacestobejoinedhaveabsorbedenoughheattokeepsoldermeltedforsometime.Insomecasesitmaybenecessarytoconnectmetalsurfacesbymeansofahardspeltersolderwhichfusesathightemperature.Thiskindofso