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.沖模，鍛模draw [drC:] vt.拉伸ingot [5IN^Bt] n.鑄錠，鋼錠press [pres] vt.壓，沖壓 n.沖壓，壓力機hydraulic [haI5drC:lIk] adj.水力的，液壓的roll [rEJl] vt.軋制，滾軋 n.卷軸，軋輥rolling [5rBlIN] n.軋制，滾軋roller [5rEJlE(r)] n.軋輥sheet [Fi:t] n.張，片，薄鋼板strip [strIp] n.條鋼，帶鋼，狹條impression [Im5preF(E)n] n.凹膛，壓痕，型腔stamp [stAmp] v.沖壓stamping [5stAmpIN] n.沖壓punch [pQntF] n.沖床 vt.沖孔，穿孔punching [pQntF] n.沖孔，穿孔assume [E5sju:m;(?@)E5su:m] vt.呈現(xiàn)，表現(xiàn) 為……形式rotate [rEJ5teIt;(?@)5rEJteIt] v.回轉(zhuǎn)，轉(zhuǎn)動rotation [rEJ5teIF(E)n] n.回轉(zhuǎn)，轉(zhuǎn)動bar [bB:(r)] n.條鋼，型鋼scale [skeIl] n.氧化皮 vt.測量，起氧化皮innumerable [I5nju:mErEb(E)l] adj.無數(shù)的welding [5weldIN] n.焊接oxyacetylene [BksIE5setIli:n] adj.氧乙炔的fuse [fju:z] v.熔合fahrenheit [5fArEnhaIt] adj.華氏溫度計的 n.華氏溫度計dropforging 模鍛，落錘鍛finishedpiece 完成件steamhammer 蒸汽錘hydraulicpress 液壓機，水壓機oxyacetylenewelding 氧—乙炔焊arcwelding 電弧焊spotwelding 點焊forgedweld 鍛焊NOTES1．Largeingotsarenowalmostalwaysforgedwithhydraulicpressesinsteadofwithsteamhammers,sincetheworkdonebyapressgoesdeeper.由于壓力機所做的功能夠傳遞得較深，因此，目前大鑄錠幾乎總是由液壓機代替蒸汽錘進行鍛造的?！癷nsteadof”是復(fù)合介詞，作“代替”、“而不是”解?！皊incetheworkdonebyapressgoesdeeper”是原因狀語從句，表示主句中的某一動作或狀態(tài)所發(fā)生的原因。“donebyapress”是過去分詞短語作定語，修飾名詞“thework”。EXERCISES1．DiscussthefollowingquestionsinEnglish:(1)?Whatisproduced,ifthemetalisrolledwithrollershavingnogroovesontheirsurface?(2)?Howmanykindsofrollingarethere?Namethem.Whichkindproducesmoreexactsize?(3)?Howmanykindsofwayswhichproducearoughwork?Whatarethey?2．UseEnglishforreplacingChineseoruseEnglishforreplacingEnglish.(1)模鍛(2)沖壓一個零件(3)軋制薄鋼板(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