《機械專業(yè)英語》課件第15章

Unit15TEXT

LEARNTOSPEAKNEWWORDSANDPHRASESNOTESEXERCISES

READINGMATERIALPROFESSIONALWORDSANDPHRASES Forging,StampingandRollingIndropforging,apieceofmetal,roughlyorapproximatelyofthedesiredshape,isplacedbetweendiefaceshavingtheexactformofthefinishedpiece,andforcedtotakethisformbydrawingthediestogether.Thismethodiswidelyusedforthemanufactureofpartsbothofsteelandbrass.Largeingotsarenowalmostalwaysforgedwithhydraulicpressesinsteadofwithsteamhammers,sincetheworkdonebyapressgoesdeeper.Fig.15-1ForgingmachineryMetalintheformofhot-rolledorcold-rolledsheetsorstripsmaybeformedintomanyshapesbyforcingthesheetintotheimpressionsinmetaldies.Thisprocessisknownasstamping,orpressingofmetals,andinvolvesmanydifferentoperations,suchasbending,drawing,punching,etc.Theseoperationsaresuccessfullycarriedoutthroughtheproperdiedesignandproperoperationofthepressinwhichthediesareplaced.Sheetsorstripsofsteel,brass,copper,aluminum,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. NOTES

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。

“insteadof”是復(fù)合介詞，作“代替”、“而不是”解。

“sincetheworkdonebyapressgoesdeeper”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”。

EXERCISES

1．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-piecehavebeenforged

3．Placea“T”aftersentencesthataretrueandan“F”afterthosethatarefalse.

(1)?Allferrousandnon-ferrousmetalsmaybeforged.()

(2)?Indropforging,thediefacesmusthavetheexactformofthefinishedpieces.()

(3)?Ingotsofmetalarerolledbyforcingthembetweentworollersrotatinginthesamedirection,thuspressingthemetalintotherequiredshape.()

(4)?Allmethodsofforgingarebasicallyrelatedtohammeringorpressingofmetal,themaindifferencebetweentwobeingthespeedofpressureapplication.()

(5)?Pressingcausesmetaltomoveastheresultofarapidlyappliedforce.()READINGMATERIAL

SolderingandBrazing

Thereareanumberofmethodsofjoiningmetalarticlestogether,dependingonthetypeofmetalandthestrengthofthejointwhichisrequired.

Solderinggivesasatisfactoryjointforlightarticlesofsteel,copperorbrass,butthestrengthofsolderedjointisratherlessthanajointwhichisbrazed,rivetedorwelded.Thesemethodsofjoiningmetalarenormallyadoptedforstrongpermanentjoint.Solderingistheprocessofjoiningtwometalsbyathirdmetaltobeappliedinthemoltenstate.Solderconsistsoftinandlead,whilebismuthandcadmiumareoftenincludedtolowerthemeltingpoint.Oneofthemostimportantoperationsinsolderingisthatofcleaningsurfacestobejoined,thismaybedonebysomeacidcleaner.Althoughtheoxidesareremovedbythecleaningoperation,anewoxidecoatingformsimmediatelyaftercleaning,thuspreventingthesoldertounitewiththesurfaceofthemetal.Fluxisusedtoremoveandpreventoxidationofthemetalsurfacetobesoldered,allowingthesoldertoflowfreelyandunitewiththemetal.Zincchlorideisthebestfluxtouseforsolderingmostferrousandnonferrousmetals,forsolderingaluminumstearineorVaselineistobeusedasfluxes.Thesolderingcopper