Unit-12-Material-Forming-Processes-機電專業(yè)英語-課件

Unit12MaterialFormingProcessesUnit12MaterialFormingProce1ContentsNewWords&Expressions

Text&TranslationComplexSentenceAnalysisKeytoExercisesContentsNewWords&Expression2NewWords&Expressionssqueeze[skwi:z]v.壓榨,擠,擠榨ingot['i?g?t]n.(冶)錠鐵,工業(yè)純鐵profile['pr?ufail] n.剖面,側(cè)面,外形,輪廓ceramic[si'r?mik]adj.陶器的sinter['sint?]v.燒結(jié)oxidation[??ksi'dei??n] n.氧化NewWords&Expressionssqueez3NewWords&Expressionssolidification[s??lidifi'kei??n]n.凝固longitudinal['l?nd?i'tju:din?l]adj.經(jīng)度的,縱向的erosive[i'r?usiv]adj.侵蝕性的,腐蝕性的dissolution[?dis?'lu:??n]n.分解,解散electrolyte[i'lektr?u?lait]n.電解,電解液sodiumchloride['s?udi?m]['kl?:raid]氯化鈉NewWords&Expressionssolidi4NewWords&Expressionssodiumnitrate['s?udi?m]['naitreit]硝酸鈉ferrous['fer?s]adj.鐵的,含鐵的,亞鐵的oxyacetylene['?ksi?'setili:n]adj.氧乙炔的acetylene[?'setili:n]n.乙炔,電石氣combustible[k?m'b?st?bl]adj.易燃的plasma['pl?zm?]n.等離子體,等離子區(qū)NewWords&Expressionssodium5Text&TranslationInthistext，ashortdescriptionoftheprocessexampleswillbegiven.Butassemblyandjoiningprocessesarenotdescribedhere.1.ForgingForgingcanbecharacterizedas:massconserving,solidstateofworkmaterial(metal),andmechanicalprimarybasicprocess-plasticdeformation.Awidevarietyofforgingprocessesareused,andFig.12-1(a)showsthemostcommonofthese:dropforging.Themetalisheatedtoasuitableworkingtemperatureandplacedinthelowerdiecavity.Theupperdieisthenloweredsothatthemetalisforcedtofillthecavity.Text&TranslationInthistext6Text&Translation[1]Excessmaterialissqueezedoutbetweenthediefacesattheperipheryasflash,whichisremovedinalatertrimmingprocess.Whenthetermforgingisused,itusuallymeanshotforging.Coldforginghasseveralspecializednames.Themateriallossinforgingprocessesisusuallyquitesmall.Normally,forgedcomponentsrequiresomesubsequentmachining,sincethetolerancesandsurfacesobtainablearenotusuallysatisfactoryforafinishedproduct.Forgingmachinesincludedrophammersandforgingpresseswithmechanicalorhydraulicdrives.Thesemachinesinvolvesimpletranslatorymotions.Text&Translation[1]Excessm7Text&Translation2.RollingRollingcanbecharacterizedas:massconserving,solidstateofmaterial,mechanicalprimarybasicprocess-plasticdeformation.Rollingisextensivelyusedinthemanufacturingofplates,sheets,structuralbeams,andsoon.Fig.12-1(b)showstherollingofplatesorsheets.Aningotisproducedincastingandinseveralstages.Itisreducedinthickness,usuallywhilehot.Sincethewidthoftheworkmaterialiskeptconstant,itslengthisincreasedaccordingtothereductions.Afterthelasthot-rollingstage,afinalstageiscarriedoutcoldtoimprovesurfacequalityandtolerancesandtoincreasestrength.Inrolling,theprofilesoftherollsaredesignedtoproducethedesiredgeometryasneeded.Text&Translation2.Rolling8Text&Translation3.PowderCompactionPowdercompactioncanbecharacterizedas:massconserving,granularstateofmaterial,mechanicalbasicprocess-flowandplasticdeformation.Inthistext,onlycompactionofmetalpowdersismentioned,butgenerallycompactionofmoldingsand,ceramicmaterials,andsoon,alsobelongtothiscategory.Text&Translation3.PowderCo9Text&TranslationInthecompactionofmetalpowders(Fig.12-1(c))thediecavityisfilledwithameasuredvolumeofpowderandcompactedatpressurestypicallyaround500N/mm2.Duringthispressingphase,theparticlesarepackedtogetherandplasticallydeformed.Typicaldensitiesaftercompactionare80%ofthedensityofthesolidmaterial.Becauseoftheplasticdeformation,theparticlesare“welded”together,givingsufficientstrengthtowithstandhandling.Aftercompaction,thecomponentsareheat-treated-sintered-normallyat70%～80%ofthemeltingtemperatureofthematerial.Theatmosphereforsinteringmustbecontrolledtopreventoxidation.Thedurationofthesinteringprocessvariesbetween30minand2h.thestrengthofthecomponentsaftersinteringcan,dependingonthematerialandtheprocessparameters,closelyapproachthestrengthofthecorrespondingsolidmaterial.Text&TranslationInthecompa10Text&TranslationThediecavity,intheclosedposition,correspondstothedesiredgeometry.Compactionmachineryincludesbothmechanicalandhydraulicpresses.Theproductionratesvarybetween6and100componentsperminute.4.CastingCastingcanbecharacterizedas:massconserving,fluidstateofmaterial,mechanicalbasicprocess-fillingofthediecavity.Castingisoneofoldestmanufacturingmethodsandoneofthebestknownprocesses.Thematerialismeltedandpouredintoadiecavitycorrespondingtothedesiredgeometry(Fig.12-1(d)).Thefluidmaterialtakestheshapeofthediecavityandthisgeometryisfinallystabilizedbythesolidificationofthematerial.Text&TranslationThediecavi11Text&TranslationFig.12-1Mass-conservingProcessesintheSolidStateoftheWorkMaterialText&TranslationFig.12-1Ma12Text&TranslationThestagesorstepsinacastingprocessarethemakingofasuitablemold,themeltingofthematerial,thefillingorpouringofthematerialintothecavity,andthesolidification.Dependingonthemoldmaterial,differentpropertiesanddimensionalaccuraciesareobtained.Equipmentusedinacastingprocessincludesfurnaces,mold-makingmachinery,andcastingmachines.Text&TranslationThestageso13Text&Translation5.TurningTurningcanbecharacterizedas：massreducing,solidstateofworkmaterial,mechanicalprimarybasicprocess-fracture.Theturningprocess,whichisthebestknownandmostwidelyusedmass-reducingprocess,isemployedtomanufacturealltypesofcylindricalshapesbyremovingmaterialintheformofchipsfromtheworkmaterialwithacuttingtool(Fig.12-2(a)).Theworkmaterialrotatesandthecuttingtoolisfedlongitudinally.Thecuttingtoolismuchharderandmorewearresistantthantheworkmaterial.Avarietyoftypesoflathesareemployed,someofwhichareautomaticinoperation.Thelathesareusuallypoweredbyelectricmotorswhich,throughvariousgears,supplythenecessarytorquetotheworkmaterialandprovidethefeedmotiontothetool.Text&Translation5.Turning14Text&TranslationAwidevarietyofmachiningoperationsorprocessesbasedonthesamemetal-cuttingprincipleareavailable;amongthemostcommonaremillinganddrillingcarriedoutonvariousmachinetools.Byvaryingthetoolshapeandthepatternofrelativework-toolmotions,manydifferentshapescanbeproduced(Fig.12-2(b)and(c)).Text&TranslationAwidevarie15Text&Translation6.EDMElectricaldischargemachining(EDM)canbecharacterizedas：massreducing,solidstateofworkmaterial,thermalprimarybasicprocess-meltingandevaporation(Fig.12-2(d)).InEDM,materialisremovedbytheerosiveactionofnumeroussmallelectricaldischarges(sparks)betweentheworkmaterialandthetool(electrode),thelatterhavingtheinverseshapeofthedesiredgeometry.Text&Translation6.EDM16Text&Translation[2]Eachdischargeoccurswhenthepotentialdifferencebetweentheworkmaterialandthetoolislargeenoughtocauseabreakdowninthefluidmedium,fedintothegapbetweenthetoolandworkpieceunderpressure,producingaconductivesparkchannel.Thefluidmedium,whichisnormallymineraloilorkerosene,hasseveralfunctions.Itservesasadielectricfluidandcoolant,maintainsauniformresistancetotheflowofcurrent,andremovestheerodedmaterial.Thesparking,whichoccursatrateofthousandsoftimespersecond,alwaysoccursatthepointwherethegapbetweenthetoolandworkpieceissmallestanddevelopssomuchheatthatasmallamountofmaterialisevaporatedanddispersedintothefluid.Thematerialsurfacehasacharacteristicappearancecomposedofnumeroussmallcraters.Text&Translation[2]Eachdisc17Text&Translation7.ECMElectrochemicalmachining(ECM)canbecharacterizedas：massreducing,solidstateofworkmaterial,chemicalprimarybasicprocess-electrolyticdissolution(Fig.12-2(e)).Electrolyticdissolutionoftheworkpieceisestablishedthroughanelectriccircuit,wheretheworkmaterialismadetheanode,andthetool,whichisapproximatelytheinverseshapeofthedesiredgeometry,ismadethecathode.Theelectrolytesnormallyusedarewater-basedsalinesolutions(sodiumchlorideandsodiumnitratein10%～30%solutions).Thevoltage,whichusuallyisintherange5V～20V,maintainshighcurrentdensities,0.5A/mm2～2A/mm2,givingarelativelyhighremovalrate,0.5cm3/min·1000A～6cm3/min·1000A,dependingontheworkmaterial.Text&Translation7.ECM18Text&Translation8.FlameCuttingFlamecuttingcanbecharacterizedas:massreducing,solidstateofworkmaterial,chemicalprimarybasicprocess-combustion(Fig.12-2(f)).Inflamecutting,thematerial(aferrousmetal)isheatedtoatemperaturewherecombustionbytheoxygensupplycanstart.Theoretically,theheatliberatedshouldbesufficienttomaintainthereactiononcestarted,butbecauseofheatlossestotheatmosphereandthematerial,acertainamountofheatmustbesuppliedcontinuously.Atorchisdesignedtoprovideheatbothforstartingandmaintainingthereaction.Mostwidelyusedistheoxyacetylenecuttingtorch,whereheatiscreatedbythecombustionofacetyleneandoxygen.Theoxygenforcuttingisnormallysuppliedthroughacenterholeinthetipofthetorch.Text&Translation8.FlameCut19Text&TranslationFig.12-2Mass-reducingProcessesintheSolidStateoftheWorkMaterialText&TranslationFig.12-2Ma20Text&TranslationTheflamecuttingprocesscanonlybyusedforeasilycombustiblematerials.Forothermaterials,cuttingprocessesbasedonthethermalbasicprocess-meltinghavebeendeveloped(arecutting,areplasmacutting,etc.).Thisisthereasoncuttingunderboththermalandchemicalbasicprocesses.Text&TranslationTheflamecu21Text&Translation本文將通過舉例簡單描述幾種金屬的切削加工工藝，不包括裝配和連接工藝。1.鍛造鍛造是對固態(tài)金屬材料進行初步機械加工，是產(chǎn)生塑性成形的質(zhì)量守恒的一種基本工藝方法。鍛造有很多類型，如圖12-1(a)所示為普通的落錘鍛造：。金屬加熱到適合加工的溫度，并放進下型腔里。上型腔與下型腔合攏，迫使金屬充滿型腔。多余的材料被從型腔接縫處擠出，并將被后續(xù)的清理型腔接縫工藝清除。當(dāng)提到鍛造術(shù)語時，通常意味熱鍛。冷鍛有幾種專門的名稱。鍛造工藝中損失的材料通常相當(dāng)少。Text&Translation本文將通過舉例簡單描述幾22Text&Translation通常，由于公差和表面粗糙度通常不能滿足最終產(chǎn)品的需要，因此對鍛造的零件要進行一些后續(xù)加工。鍛造機械包括落錘和機械或水力驅(qū)動的鍛壓。這些機械包括簡單的平移運動。2.滾軋滾軋是對固態(tài)金屬材料進行初步機械加工，使其產(chǎn)生塑性變形的質(zhì)量守恒的一種工藝方法。滾軋廣泛應(yīng)用在板材、薄板和結(jié)構(gòu)桁條等制造中。如圖12-1(b)所示為板材或薄板的滾軋。鑄造生產(chǎn)出的鐵錠加熱后，經(jīng)過幾個階段厚度上變薄。由于工件的寬度保持不變，工件的長度將隨著厚度的變薄而變長。在熱軋階段之后，最終階段是進行冷卻，以提高表面質(zhì)量、公差，并提高強度。滾軋工藝中，根據(jù)需要，軋輥的外形被設(shè)計生產(chǎn)成期望的幾何形狀。Text&Translation通常，由于公差和表面粗糙23Text&Translation圖12-1固態(tài)下的工件材料質(zhì)量不變工藝Text&Translation圖12-1固態(tài)下的工件24Text&Translation3.粉末擠壓粉末擠壓是對粒狀材料進行機械加工，使其產(chǎn)生塑性變形的質(zhì)量守恒的一種工藝方法。在這里僅提到了金屬粉末擠壓，但通常成型砂、陶瓷材料的擠壓等也屬于此加工工藝。金屬粉末擠壓時，型腔充滿標(biāo)稱體積粉末，如圖12-1(c)所示施加大約500N/mm2的壓力壓緊粉末。在擠壓過程中，粉末顆粒充滿型腔并發(fā)生塑性變形。擠壓后的典型密度是固態(tài)材料密度的80%。經(jīng)過塑性變形，粉末顆?！昂附印钡揭黄?，強度足夠經(jīng)受得住一般操作。擠壓后，零件要以融化溫度的70%～80%進行一般燒結(jié)熱處理。燒結(jié)用的空氣一定要控制好，以防止氧化。根據(jù)材料和工藝參數(shù)，燒結(jié)過程的持續(xù)時間從30分鐘到2小時不等，燒結(jié)后零件強度非常接近相應(yīng)固體材料的強度。Text&Translation3.粉末擠壓25Text&Translation閉合的型腔形狀與期望得到的零件幾何形狀相對應(yīng)。擠壓機械包括機械壓力擠壓機和水力壓力擠壓機兩種。生產(chǎn)率為每分鐘6～100個零件。4.鑄造鑄造是將液態(tài)材料充滿型腔的質(zhì)量守恒的一種基礎(chǔ)機械工藝方法。鑄造是最古老的加工方法之一，同時是最廣為人知的一種工藝。材料被融化，并灌入根據(jù)希望得到的幾何形狀制作的相應(yīng)型腔(見圖12-1(d)。液體材料充滿型腔，隨著材料凝固，零件的幾何形狀最終固定下來。Text&Translation閉合的型腔形狀與期望得到26Text&Translation鑄造工藝中的階段或步驟包括制作適當(dāng)?shù)蔫T型，熔化材料，將材料充滿或灌注進型腔和凝固。根據(jù)采用的不同鑄型材料，可獲得不同特性和尺寸精度的鑄件。鑄造工藝中使用的設(shè)備包括熔爐、鑄型制作機械和鑄造機械。Text&Translation鑄造工藝中的階段或步驟包27Text&Translation5.車削車削是通過破裂，對固態(tài)工件進行初步的基礎(chǔ)機械加工，質(zhì)量減少的一種工藝方法。車削工藝廣為人知，并且是使用最廣泛的質(zhì)量減少的工藝方法。車削工藝中使用切削刀具，從工件上以碎片形狀切去材料(見圖12-2(a))，用于生產(chǎn)各種類型的圓柱形工件。加工時，工件旋轉(zhuǎn)，切削刀具縱向進給。切削刀具比工件更加堅硬和抗磨損。可采用不同類型的車床，有些還是自動操作的。車床通常是電動機驅(qū)動的，通過不同的齒輪系統(tǒng)，向工件提供必要的扭矩，使刀具進行進給動作。Text&Translation5.車削28Text&Translation利用相同金屬切削原理，也會得到完全不同的加工操作或工藝，磨和鉆就是其中最普通的一個例子，由于采用不同的加工刀具而產(chǎn)生完全不同的兩種加工操作。不同的刀具形狀和相關(guān)加工刀具運動模式，可生產(chǎn)出許多不同的形狀(見圖12-2(b)和12-2(c))。Text&Translation利用相同金屬切削原理，也29Text&Translation6.電火花加工電火花加工(EDM)是通過融化和蒸發(fā)，對固態(tài)工件進行以熱變化為主要基礎(chǔ)，質(zhì)量減少的一種工藝方法，如圖12-2(d)所示。在電火花加工中，通過工件和工具(電極)之間許多小電火花的侵蝕動作來去除材料，工具具有希望得到的工件幾何形狀的反轉(zhuǎn)形狀。當(dāng)工件和工具之間電壓差異足夠大時，液體介質(zhì)被擊穿，并在電壓作用下，進入工具和工件之間的縫隙，形成傳導(dǎo)火花的通道，這時出現(xiàn)了放電。流體介質(zhì)通常是礦物油或煤油，它有幾種功能：作為絕緣的流體和散熱劑，為電流維持不變的電阻，去除侵蝕的材料。電火花以每秒成千上萬次的速度出現(xiàn)，且總是出現(xiàn)在工具和工件間縫隙最小的點上，產(chǎn)生大量的熱使得少量的材料給侵蝕并散入液體中。電火花加工后的材料表面具有的特點是它由許多小彈坑組成。Text&Translation6.電火花加工30Text&Translation圖12-2固態(tài)下的工件材料質(zhì)量減少工藝Text&Translation圖12-2固態(tài)下的工件31Text&Translation7.電氣化學(xué)加工電氣化學(xué)加工(ECM)是通過電解分解，對固態(tài)工件進行以化學(xué)變化為主要基礎(chǔ)、質(zhì)量減少的一種工藝方法(見圖12.-2(e))。工件的電解分解是通過一個電路實現(xiàn)的，工件作為陽極，工具作為陰極。工具具有希望得到的工件幾何形狀的近似反轉(zhuǎn)形狀。電解液通常使用水基鹽(氯化鈉10%和硝酸鈉30%)。通常使用5～20V電壓，可維持高的電流密度——0.5～2A/mm2，相對高的移動速度0.5～6cm3/min·1000A，這些都根據(jù)工件來具體確定。Text&Translation7.電氣化學(xué)加工32Text&Translation8.火焰切割火焰切割是通過燃燒，對固態(tài)工件進行以化學(xué)變化為主要基礎(chǔ)，質(zhì)量減少的一種工藝方法(見圖12-2)?；鹧媲懈钪?，材料(含鐵金屬)被加熱到供氧時可開始燃燒的溫度。理論上，一旦開始燃燒，釋放的熱量應(yīng)該足夠維持反應(yīng)，但由于熱量散失到空氣和材料中，因此要不斷地提供一定量的熱量。設(shè)計一個噴槍來提供開始和維持反應(yīng)所需的熱量。使用最廣泛的是乙炔切削噴槍，通過燃燒乙炔和氧氣產(chǎn)生熱量。切削用的氧氣通常通過噴槍頂端中心的孔提供?；鹧媲邢鞴に噧H適用于易燃材料。對于其他材料，可采用通過熔化、以熱變化為基礎(chǔ)的切削工藝(切削、等離子切削等)。這是以熱變化和化學(xué)變化為基礎(chǔ)的切削工藝的前提。Text&Translation8.火焰切割33ComplexSentenceAnalysis[1]Excessmaterialissqueezedoutbetweenthediefacesattheperipheryasflash,whichisremovedinalatertrimmingprocess.多余的材料被從型腔接縫處擠出，并將被后續(xù)的清理型腔接縫工藝清除。①which：引導(dǎo)定語從句，修飾excessmaterial②asflash：如閃電一樣快速③trimmingprocess：清理縫隙的過程ComplexSentenceAnalysis[1]34ComplexSentenceAnalysis[2]Eachdischargeoccurswhenthepotentialdifferencebetweentheworkmaterialandthetoolislargeenoughtocauseabreakdowninthefluidmedium,fedintothegapbetweenthetoolandworkpieceunderpressure,producingaconductivesparkchannel.當(dāng)工件和工具之間電壓差異足夠大時，流體介質(zhì)被擊穿，并在電壓作用下，進入工具和工件之間的縫隙，形成傳導(dǎo)火花的通道，這時出現(xiàn)了放電。①when：引導(dǎo)時間狀語從句②fedinto…：過去分詞短語做狀語修飾fluidmedium③producingaconductivesparkchannel現(xiàn)在分詞短語做伴隨狀語ComplexSentenceAnalysis[2]E35KeytoExercisesⅠ.TranslatethefollowingphrasesintoChineseorEnglish.1.材料成形工藝方法2.forging3.滾軋4.powdercompaction5.一般燒結(jié)熱處理6.casting7.車削8.electicaldischargemachining(EDM)9.電氣化學(xué)加工10.flamecuttingKeytoExercisesⅠ.Translatet36KeytoExercisesⅡ.MarkthefollowingstatementwithTrue(T)orFalse(F)accordingtothetext.1．T2.F3.T4.T5.TKeytoExercisesⅡ.Markthefo37KeytoExercisesⅢ.Fillintheblankswiththesuitablewordsorphrasesgivenbelow.1.becharacterizedas2.Awidevarietyof3.isheatedto4.fillthecavity5.alatertrimmingprocess6.severalspecializednamesKeytoExercisesⅢ.Fillinthe38KeytoExercisesⅣ.TranslatetheChinesepartsgiveninthebracketsintoEnglish.1.thefillingorpouringofthematerialintothecavity,bustionKeytoExercisesⅣ.Translateth39Theend!Theend!40Unit12MaterialFormingProcessesUnit12MaterialFormingProce41ContentsNewWords&Expressions

Text&TranslationComplexSentenceAnalysisKeytoExercisesContentsNewWords&Expression42NewWords&Expressionssqueeze[skwi:z]v.壓榨,擠,擠榨ingot['i?g?t]n.(冶)錠鐵,工業(yè)純鐵profile['pr?ufail] n.剖面,側(cè)面,外形,輪廓ceramic[si'r?mik]adj.陶器的sinter['sint?]v.燒結(jié)oxidation[??ksi'dei??n] n.氧化NewWords&Expressionssqueez43NewWords&Expressionssolidification[s??lidifi'kei??n]n.凝固longitudinal['l?nd?i'tju:din?l]adj.經(jīng)度的,縱向的erosive[i'r?usiv]adj.侵蝕性的,腐蝕性的dissolution[?dis?'lu:??n]n.分解,解散electrolyte[i'lektr?u?lait]n.電解,電解液sodiumchloride['s?udi?m]['kl?:raid]氯化鈉NewWords&Expressionssolidi44NewWords&Expressionssodiumnitrate['s?udi?m]['naitreit]硝酸鈉ferrous['fer?s]adj.鐵的,含鐵的,亞鐵的oxyacetylene['?ksi?'setili:n]adj.氧乙炔的acetylene[?'setili:n]n.乙炔,電石氣combustible[k?m'b?st?bl]adj.易燃的plasma['pl?zm?]n.等離子體,等離子區(qū)NewWords&Expressionssodium45Text&TranslationInthistext，ashortdescriptionoftheprocessexampleswillbegiven.Butassemblyandjoiningprocessesarenotdescribedhere.1.ForgingForgingcanbecharacterizedas:massconserving,solidstateofworkmaterial(metal),andmechanicalprimarybasicprocess-plasticdeformation.Awidevarietyofforgingprocessesareused,andFig.12-1(a)showsthemostcommonofthese:dropforging.Themetalisheatedtoasuitableworkingtemperatureandplacedinthelowerdiecavity.Theupperdieisthenloweredsothatthemetalisforcedtofillthecavity.Text&TranslationInthistext46Text&Translation[1]Excessmaterialissqueezedoutbetweenthediefacesattheperipheryasflash,whichisremovedinalatertrimmingprocess.Whenthetermforgingisused,itusuallymeanshotforging.Coldforginghasseveralspecializednames.Themateriallossinforgingprocessesisusuallyquitesmall.Normally,forgedcomponentsrequiresomesubsequentmachining,sincethetolerancesandsurfacesobtainablearenotusuallysatisfactoryforafinishedproduct.Forgingmachinesincludedrophammersandforgingpresseswithmechanicalorhydraulicdrives.Thesemachinesinvolvesimpletranslatorymotions.Text&Translation[1]Excessm47Text&Translation2.RollingRollingcanbecharacterizedas:massconserving,solidstateofmaterial,mechanicalprimarybasicprocess-plasticdeformation.Rollingisextensivelyusedinthemanufacturingofplates,sheets,structuralbeams,andsoon.Fig.12-1(b)showstherollingofplatesorsheets.Aningotisproducedincastingandinseveralstages.Itisreducedinthickness,usuallywhilehot.Sincethewidthoftheworkmaterialiskeptconstant,itslengthisincreasedaccordingtothereductions.Afterthelasthot-rollingstage,afinalstageiscarriedoutcoldtoimprovesurfacequalityandtolerancesandtoincreasestrength.Inrolling,theprofilesoftherollsaredesignedtoproducethedesiredgeometryasneeded.Text&Translation2.Rolling48Text&Translation3.PowderCompactionPowdercompactioncanbecharacterizedas:massconserving,granularstateofmaterial,mechanicalbasicprocess-flowandplasticdeformation.Inthistext,onlycompactionofmetalpowdersismentioned,butgenerallycompactionofmoldingsand,ceramicmaterials,andsoon,alsobelongtothiscategory.Text&Translation3.PowderCo49Text&TranslationInthecompactionofmetalpowders(Fig.12-1(c))thediecavityisfilledwithameasuredvolumeofpowderandcompactedatpressurestypicallyaround500N/mm2.Duringthispressingphase,theparticlesarepackedtogetherandplasticallydeformed.Typicaldensitiesaftercompactionare80%ofthedensityofthesolidmaterial.Becauseoftheplasticdeformation,theparticlesare“welded”together,givingsufficientstrengthtowithstandhandling.Aftercompaction,thecomponentsareheat-treated-sintered-normallyat70%～80%ofthemeltingtemperatureofthematerial.Theatmosphereforsinteringmustbecontrolledtopreventoxidation.Thedurationofthesinteringprocessvariesbetween30minand2h.thestrengthofthecomponentsaftersinteringcan,dependingonthematerialandtheprocessparameters,closelyapproachthestrengthofthecorrespondingsolidmaterial.Text&TranslationInthecompa50Text&TranslationThediecavity,intheclosedposition,correspondstothedesiredgeometry.Compactionmachineryincludesbothmechanicalandhydraulicpresses.Theproductionratesvarybetween6and100componentsperminute.4.CastingCastingcanbecharacterizedas:massconserving,fluidstateofmaterial,mechanicalbasicprocess-fillingofthediecavity.Castingisoneofoldestmanufacturingmethodsandoneofthebestknownprocesses.Thematerialismeltedandpouredintoadiecavitycorrespondingtothedesiredgeometry(Fig.12-1(d)).Thefluidmaterialtakestheshapeofthediecavityandthisgeometryisfinallystabilizedbythesolidificationofthematerial.Text&TranslationThediecavi51Text&TranslationFig.12-1Mass-conservingProcessesintheSolidStateoftheWorkMaterialText&TranslationFig.12-1Ma52Text&TranslationThestagesorstepsinacastingprocessarethemakingofasuitablemold,themeltingofthematerial,thefillingorpouringofthematerialintothecavity,andthesolidification.Dependingonthemoldmaterial,differentpropertiesanddimensionalaccuraciesareobtained.Equipmentusedinacastingprocessincludesfurnaces,mold-makingmachinery,andcastingmachines.Text&TranslationThestageso53Text&Translation5.TurningTurningcanbecharacterizedas：massreducing,solidstateofworkmaterial,mechanicalprimarybasicprocess-fracture.Theturningprocess,whichisthebestknownandmostwidelyusedmass-reducingprocess,isemployedtomanufacturealltypesofcylindricalshapesbyremovingmaterialintheformofchipsfromtheworkmaterialwithacuttingtool(Fig.12-2(a)).Theworkmaterialrotatesandthecuttingtoolisfedlongitudinally.Thecuttingtoolismuchharderandmorewearresistantthantheworkmaterial.Avarietyoftypesoflathesareemployed,someofwhichareautomaticinoperation.Thelathesareusuallypoweredbyelectricmotorswhich,throughvariousgears,supplythenecessarytorquetotheworkmaterialandprovidethefeedmotiontothetool.Text&Translation5.Turning54Text&TranslationAwidevarietyofmachiningoperationsorprocessesbasedonthesamemetal-cuttingprincipleareavailable;amongthemostcommonaremillinganddrillingcarriedoutonvariousmachinetools.Byvaryingthetoolshapeandthepatternofrelativework-toolmotions,manydifferentshapescanbeproduced(Fig.12-2(b)and(c)).Text&TranslationAwidevarie55Text&Translation6.EDMElectricaldischargemachining(EDM)canbecharacterizedas：massreducing,solidstateofworkmaterial,thermalprimarybasicprocess-meltingandevaporation(Fig.12-2(d)).InEDM,materialisremovedbytheerosiveactionofnumeroussmallelectricaldischarges(sparks)betweentheworkmaterialandthetool(electrode),thelatterhavingtheinverseshapeofthedesiredgeometry.Text&Translation6.EDM56Text&Translation[2]Eachdischargeoccurswhenthepotentialdifferencebetweentheworkmaterialandthetoolislargeenoughtocauseabreakdowninthefluidmedium,fedintothegapbetweenthetoolandworkpieceunderpressure,producingaconductivesparkchannel.Thefluidmedium,whichisnormallymineraloilorkerosene,hasseveralfunctions.Itservesasadielectricfluidandcoolant,maintainsauniformresistancetotheflowofcurrent,andremovestheerodedmaterial.Thesparking,whichoccursatrateofthousandsoftimespersecond,alwaysoccursatthepointwherethegapbetweenthetoolandworkpieceissmallestanddevelopssomuchheatthatasmallamountofmaterialisevaporatedanddispersedintothefluid.Thematerialsurfacehasacharacteristicappearancecomposedofnumeroussmallcraters.Text&Translation[2]Eachdisc57Text&Translation7.ECMElectrochemicalmachining(ECM)canbecharacterizedas：massreducing,solidstateofworkmaterial,chemicalprimarybasicprocess-electrolyticdissolution(Fig.12-2(e)).Electrolyticdissolutionoftheworkpieceisestablishedthroughanelectriccircuit,wheretheworkmaterialismadetheanode,andthetool,whichisapproximatelytheinverseshapeofthedesiredgeometry,ismadethecathode.Theelectrolytesnormallyusedarewater-basedsalinesolutions(sodiumchlorideandsodiumnitratein10%～30%solutions).Thevoltage,whichusuallyisintherange5V～20V,maintainshighcurrentdensities,0.5A/mm2～2A/mm2,givingarelativelyhighremovalrate,0.5cm3/min·1000A～6cm3/min·1000A,dependingontheworkmaterial.Text&Translation7.ECM58Text&Translation8.FlameCuttingFlamecuttingcanbecharacterizedas:massreducing,solidstateofworkmaterial,chemicalprimarybasicprocess-combustion(Fig.12-2(f)).Inflamecutting,thematerial(aferrousmetal)isheatedtoatemperaturewherecombustionbytheoxygensupplycanstart.Theoretically,theheatliberatedshouldbesufficienttomaintainthereactiononcestarted,butbecauseofheatlossestotheatmosphereandthematerial,acertainamountofheatmustbesuppliedcontinuously.Atorchisdesignedtoprovideheatbothforstartingandmaintainingthereaction.Mostwidelyusedistheoxyacetylenecuttingtorch,whereheatiscreatedbythecombustionofacetyleneandoxygen.Theoxygenforcuttingisnormallysuppliedthroughacenterholeinthetipofthetorch.Text&Translation8.FlameCut59Text&TranslationFig.12-2Mass-reducingProcessesintheSolidStateoftheWorkMaterialText&TranslationFig.12-2Ma60Text&TranslationTheflamecuttingprocesscanonlybyusedforeasilycombustiblematerials.Forothermaterials,cuttingprocessesbasedonthethermalbasicprocess-meltinghavebeendeveloped(arecutting,areplasmacutting,etc.).Thisisthereasoncuttingunderboththermalandchemicalbasicprocesses.Text&TranslationTheflamecu61Text&Translation本文將通過舉例簡單描述幾種金屬的切削加工工藝，不包括裝配和連接工藝。1.鍛造鍛造是對固態(tài)金屬材料進行初步機械加工，是產(chǎn)生塑性成形的質(zhì)量守恒的一種基本工藝方法。鍛造有很多類型，如圖12-1(a)所示為普通的落錘鍛造：。金屬加熱到適合加工的溫度，并放進下型腔里。上型腔與下型腔合攏，迫使金屬充滿型腔。多余的材料被從型腔接縫處擠出，并將被后續(xù)的清理型腔接縫工藝清除。當(dāng)提到鍛造術(shù)語時，通常意味熱鍛。冷鍛有幾種專門的名稱。鍛造工藝中損失的材料通常相當(dāng)少。Text&Translation本文將通過舉例簡單描述幾62Text&Translation通常，由于公差和表面粗糙度通常不能滿足最終產(chǎn)品的需要，因此對鍛造的零件要進行一些后續(xù)加工。鍛造機械包括落錘和機械或水力驅(qū)動的鍛壓。這些機械包括簡單的平移運動。2.滾軋滾軋是對固態(tài)金屬材料進行初步機械加工，使其產(chǎn)生塑性變形的質(zhì)量守恒的一種工藝方法。滾軋廣泛應(yīng)用在板材、薄板和結(jié)構(gòu)桁條等制造中。如圖12-1(b)所示為板材或薄板的滾軋。鑄造生產(chǎn)出的鐵錠加熱后，經(jīng)過幾個階段厚度上變薄。由于工件的寬度保持不變，工件的長度將隨著厚度的變薄而變長。在熱軋階段之后，最終階段是進行冷卻，以提高表面質(zhì)量、公差，并提高強度。滾軋工藝中，根據(jù)需要，軋輥的外形被設(shè)計生產(chǎn)成期望的幾何形狀。Text&Translation通常，由于公差和表面粗糙63Text&Translation圖12-1固態(tài)下的工件材料質(zhì)量不變工藝Text&Translation圖12-1固態(tài)下的工件64Text&Translation3.粉末擠壓粉末擠壓是對粒狀材料進行機械加工，使其產(chǎn)生塑性變形的質(zhì)量守恒的一種工藝方法。在這里僅提到了金屬粉末擠壓，但通常成型砂、陶瓷材料的擠壓等也屬于此加工工藝。金屬粉末擠壓時，型腔充滿標(biāo)稱體積粉末，如圖12-1(c)所示施加大約500N/mm2的壓力壓緊粉末。在擠壓過程中，粉末顆粒充滿型腔并發(fā)生塑性變形。擠壓后的典型密度是固態(tài)材料密度的80%。經(jīng)過塑性變形，粉末顆?！昂附印钡揭黄穑瑥姸茸銐蚪?jīng)受得住一般操作。擠壓后，零件要以融化溫度的70%～80%進行一般燒結(jié)熱處理。燒結(jié)用的空氣一定要控制好，以防止氧化。根據(jù)材料和工藝參數(shù)，燒結(jié)過程的持續(xù)時間從30分鐘到2小時不等，燒結(jié)后零件強度非常接近相應(yīng)固體材料的強度。Text&Translation3.粉末擠壓65Text&Translation閉合的型腔形狀與期望得到的零件幾何形狀相對應(yīng)。擠壓機械包括機械壓力擠壓機和水力壓力擠壓機兩種。生產(chǎn)率為每分鐘6～100個零件。4.鑄造鑄造是將液態(tài)材料充滿型腔的質(zhì)量守恒的一種基礎(chǔ)機械工藝方法。鑄造是最古老的加工方法之一，同時是最廣為人知的一種工藝。材料被融化，并灌入根據(jù)希望得到的幾何形狀制作的相應(yīng)型腔(見圖12-1(d)。液體材料充滿型腔，隨著材料凝固，零件的幾何形狀最終固定下來。Text&Translation閉合的型腔形狀與期望得到66Text&Translation鑄造