Unit-12-Material-Forming-Processes-机电专业英语-课件

Unit12MaterialFormingProcessesUnit12MaterialFormingProce1ContentsNewWords&Expressions

Text&TranslationComplexSentenceAnalysisKeytoExercisesContentsNewWords&Expression2NewWords&Expressionssqueeze[skwi:z]v.压榨,挤,挤榨ingot['iŋgət]n.(冶)锭铁,工业纯铁profile['prəufail] n.剖面,侧面,外形,轮廓ceramic[si'ræmik]adj.陶器的sinter['sintə]v.烧结oxidation[͵ɔksi'deiʃən] n.氧化NewWords&Expressionssqueez3NewWords&Expressionssolidification[sə͵lidifi'keiʃən]n.凝固longitudinal['lɔndʒi'tju:dinəl]adj.经度的,纵向的erosive[i'rəusiv]adj.侵蚀性的,腐蚀性的dissolution[͵disə'lu:ʃən]n.分解,解散electrolyte[i'lektrəu͵lait]n.电解,电解液sodiumchloride['səudiəm]['klɔ:raid]氯化钠NewWords&Expressionssolidi4NewWords&Expressionssodiumnitrate['səudiəm]['naitreit]硝酸钠ferrous['ferəs]adj.铁的,含铁的,亚铁的oxyacetylene['ɔksiə'setili:n]adj.氧乙炔的acetylene[ə'setili:n]n.乙炔,电石气combustible[kəm'bʌstəbl]adj.易燃的plasma['plæzmə]n.等离子体,等离子区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本文将通过举例简单描述几种金属的切削加工工艺，不包括装配和连接工艺。1.锻造锻造是对固态金属材料进行初步机械加工，是产生塑性成形的质量守恒的一种基本工艺方法。锻造有很多类型，如图12-1(a)所示为普通的落锤锻造：。金属加热到适合加工的温度，并放进下型腔里。上型腔与下型腔合拢，迫使金属充满型腔。多余的材料被从型腔接缝处挤出，并将被后续的清理型腔接缝工艺清除。当提到锻造术语时，通常意味热锻。冷锻有几种专门的名称。锻造工艺中损失的材料通常相当少。Text&Translation本文将通过举例简单描述几22Text&Translation通常，由于公差和表面粗糙度通常不能满足最终产品的需要，因此对锻造的零件要进行一些后续加工。锻造机械包括落锤和机械或水力驱动的锻压。这些机械包括简单的平移运动。2.滚轧滚轧是对固态金属材料进行初步机械加工，使其产生塑性变形的质量守恒的一种工艺方法。滚轧广泛应用在板材、薄板和结构桁条等制造中。如图12-1(b)所示为板材或薄板的滚轧。铸造生产出的铁锭加热后，经过几个阶段厚度上变薄。由于工件的宽度保持不变，工件的长度将随着厚度的变薄而变长。在热轧阶段之后，最终阶段是进行冷却，以提高表面质量、公差，并提高强度。滚轧工艺中，根据需要，轧辊的外形被设计生产成期望的几何形状。Text&Translation通常，由于公差和表面粗糙23Text&Translation图12-1固态下的工件材料质量不变工艺Text&Translation图12-1固态下的工件24Text&Translation3.粉末挤压粉末挤压是对粒状材料进行机械加工，使其产生塑性变形的质量守恒的一种工艺方法。在这里仅提到了金属粉末挤压，但通常成型砂、陶瓷材料的挤压等也属于此加工工艺。金属粉末挤压时，型腔充满标称体积粉末，如图12-1(c)所示施加大约500N/mm2的压力压紧粉末。在挤压过程中，粉末颗粒充满型腔并发生塑性变形。挤压后的典型密度是固态材料密度的80%。经过塑性变形，粉末颗粒“焊接”到一起，强度足够经受得住一般操作。挤压后，零件要以融化温度的70%～80%进行一般烧结热处理。烧结用的空气一定要控制好，以防止氧化。根据材料和工艺参数，烧结过程的持续时间从30分钟到2小时不等，烧结后零件强度非常接近相应固体材料的强度。Text&Translation3.粉末挤压25Text&Translation闭合的型腔形状与期望得到的零件几何形状相对应。挤压机械包括机械压力挤压机和水力压力挤压机两种。生产率为每分钟6～100个零件。4.铸造铸造是将液态材料充满型腔的质量守恒的一种基础机械工艺方法。铸造是最古老的加工方法之一，同时是最广为人知的一种工艺。材料被融化，并灌入根据希望得到的几何形状制作的相应型腔(见图12-1(d)。液体材料充满型腔，随着材料凝固，零件的几何形状最终固定下来。Text&Translation闭合的型腔形状与期望得到26Text&Translation铸造工艺中的阶段或步骤包括制作适当的铸型，熔化材料，将材料充满或灌注进型腔和凝固。根据采用的不同铸型材料，可获得不同特性和尺寸精度的铸件。铸造工艺中使用的设备包括熔炉、铸型制作机械和铸造机械。Text&Translation铸造工艺中的阶段或步骤包27Text&Translation5.车削车削是通过破裂，对固态工件进行初步的基础机械加工，质量减少的一种工艺方法。车削工艺广为人知，并且是使用最广泛的质量减少的工艺方法。车削工艺中使用切削刀具，从工件上以碎片形状切去材料(见图12-2(a))，用于生产各种类型的圆柱形工件。加工时，工件旋转，切削刀具纵向进给。切削刀具比工件更加坚硬和抗磨损。可采用不同类型的车床，有些还是自动操作的。车床通常是电动机驱动的，通过不同的齿轮系统，向工件提供必要的扭矩，使刀具进行进给动作。Text&Translation5.车削28Text&Translation利用相同金属切削原理，也会得到完全不同的加工操作或工艺，磨和钻就是其中最普通的一个例子，由于采用不同的加工刀具而产生完全不同的两种加工操作。不同的刀具形状和相关加工刀具运动模式，可生产出许多不同的形状(见图12-2(b)和12-2(c))。Text&Translation利用相同金属切削原理，也29Text&Translation6.电火花加工电火花加工(EDM)是通过融化和蒸发，对固态工件进行以热变化为主要基础，质量减少的一种工艺方法，如图12-2(d)所示。在电火花加工中，通过工件和工具(电极)之间许多小电火花的侵蚀动作来去除材料，工具具有希望得到的工件几何形状的反转形状。当工件和工具之间电压差异足够大时，液体介质被击穿，并在电压作用下，进入工具和工件之间的缝隙，形成传导火花的通道，这时出现了放电。流体介质通常是矿物油或煤油，它有几种功能：作为绝缘的流体和散热剂，为电流维持不变的电阻，去除侵蚀的材料。电火花以每秒成千上万次的速度出现，且总是出现在工具和工件间缝隙最小的点上，产生大量的热使得少量的材料给侵蚀并散入液体中。电火花加工后的材料表面具有的特点是它由许多小弹坑组成。Text&Translation6.电火花加工30Text&Translation图12-2固态下的工件材料质量减少工艺Text&Translation图12-2固态下的工件31Text&Translation7.电气化学加工电气化学加工(ECM)是通过电解分解，对固态工件进行以化学变化为主要基础、质量减少的一种工艺方法(见图12.-2(e))。工件的电解分解是通过一个电路实现的，工件作为阳极，工具作为阴极。工具具有希望得到的工件几何形状的近似反转形状。电解液通常使用水基盐(氯化钠10%和硝酸钠30%)。通常使用5～20V电压，可维持高的电流密度——0.5～2A/mm2，相对高的移动速度0.5～6cm3/min·1000A，这些都根据工件来具体确定。Text&Translation7.电气化学加工32Text&Translation8.火焰切割火焰切割是通过燃烧，对固态工件进行以化学变化为主要基础，质量减少的一种工艺方法(见图12-2)。火焰切割中，材料(含铁金属)被加热到供氧时可开始燃烧的温度。理论上，一旦开始燃烧，释放的热量应该足够维持反应，但由于热量散失到空气和材料中，因此要不断地提供一定量的热量。设计一个喷枪来提供开始和维持反应所需的热量。使用最广泛的是乙炔切削喷枪，通过燃烧乙炔和氧气产生热量。切削用的氧气通常通过喷枪顶端中心的孔提供。火焰切削工艺仅适用于易燃材料。对于其他材料，可采用通过熔化、以热变化为基础的切削工艺(切削、等离子切削等)。这是以热变化和化学变化为基础的切削工艺的前提。Text&Translation8.火焰切割33ComplexSentenceAnalysis[1]Excessmaterialissqueezedoutbetweenthediefacesattheperipheryasflash,whichisremovedinalatertrimmingprocess.多余的材料被从型腔接缝处挤出，并将被后续的清理型腔接缝工艺清除。①which：引导定语从句，修饰excessmaterial②asflash：如闪电一样快速③trimmingprocess：清理缝隙的过程ComplexSentenceAnalysis[1]34ComplexSentenceAnalysis[2]Eachdischargeoccurswhenthepotentialdifferencebetweentheworkmaterialandthetoolislargeenoughtocauseabreakdowninthefluidmedium,fedintothegapbetweenthetoolandworkpieceunderpressure,producingaconductivesparkchannel.当工件和工具之间电压差异足够大时，流体介质被击穿，并在电压作用下，进入工具和工件之间的缝隙，形成传导火花的通道，这时出现了放电。①when：引导时间状语从句②fedinto…：过去分词短语做状语修饰fluidmedium③producingaconductivesparkchannel现在分词短语做伴随状语ComplexSentenceAnalysis[2]E35KeytoExercisesⅠ.TranslatethefollowingphrasesintoChineseorEnglish.1.材料成形工艺方法2.forging3.滚轧4.powdercompaction5.一般烧结热处理6.casting7.车削8.electicaldischargemachining(EDM)9.电气化学加工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.压榨,挤,挤榨ingot['iŋgət]n.(冶)锭铁,工业纯铁profile['prəufail] n.剖面,侧面,外形,轮廓ceramic[si'ræmik]adj.陶器的sinter['sintə]v.烧结oxidation[͵ɔksi'deiʃən] n.氧化NewWords&Expressionssqueez43NewWords&Expressionssolidification[sə͵lidifi'keiʃən]n.凝固longitudinal['lɔndʒi'tju:dinəl]adj.经度的,纵向的erosive[i'rəusiv]adj.侵蚀性的,腐蚀性的dissolution[͵disə'lu:ʃən]n.分解,解散electrolyte[i'lektrəu͵lait]n.电解,电解液sodiumchloride['səudiəm]['klɔ:raid]氯化钠NewWords&Expressionssolidi44NewWords&Expressionssodiumnitrate['səudiəm]['naitreit]硝酸钠ferrous['ferəs]adj.铁的,含铁的,亚铁的oxyacetylene['ɔksiə'setili:n]adj.氧乙炔的acetylene[ə'setili:n]n.乙炔,电石气combustible[kəm'bʌstəbl]adj.易燃的plasma['plæzmə]n.等离子体,等离子区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本文将通过举例简单描述几种金属的切削加工工艺，不包括装配和连接工艺。1.锻造锻造是对固态金属材料进行初步机械加工，是产生塑性成形的质量守恒的一种基本工艺方法。锻造有很多类型，如图12-1(a)所示为普通的落锤锻造：。金属加热到适合加工的温度，并放进下型腔里。上型腔与下型腔合拢，迫使金属充满型腔。多余的材料被从型腔接缝处挤出，并将被后续的清理型腔接缝工艺清除。当提到锻造术语时，通常意味热锻。冷锻有几种专门的名称。锻造工艺中损失的材料通常相当少。Text&Translation本文将通过举例简单描述几62Text&Translation通常，由于公差和表面粗糙度通常不能满足最终产品的需要，因此对锻造的零件要进行一些后续加工。锻造机械包括落锤和机械或水力驱动的锻压。这些机械包括简单的平移运动。2.滚轧滚轧是对固态金属材料进行初步机械加工，使其产生塑性变形的质量守恒的一种工艺方法。滚轧广泛应用在板材、薄板和结构桁条等制造中。如图12-1(b)所示为板材或薄板的滚轧。铸造生产出的铁锭加热后，经过几个阶段厚度上变薄。由于工件的宽度保持不变，工件的长度将随着厚度的变薄而变长。在热轧阶段之后，最终阶段是进行冷却，以提高表面质量、公差，并提高强度。滚轧工艺中，根据需要，轧辊的外形被设计生产成期望的几何形状。Text&Translation通常，由于公差和表面粗糙63Text&Translation图12-1固态下的工件材料质量不变工艺Text&Translation图12-1固态下的工件64Text&Translation3.粉末挤压粉末挤压是对粒状材料进行机械加工，使其产生塑性变形的质量守恒的一种工艺方法。在这里仅提到了金属粉末挤压，但通常成型砂、陶瓷材料的挤压等也属于此加工工艺。金属粉末挤压时，型腔充满标称体积粉末，如图12-1(c)所示施加大约500N/mm2的压力压紧粉末。在挤压过程中，粉末颗粒充满型腔并发生塑性变形。挤压后的典型密度是固态材料密度的80%。经过塑性变形，粉末颗粒“焊接”到一起，强度足够经受得住一般操作。挤压后，零件要以融化温度的70%～80%进行一般烧结热处理。烧结用的空气一定要控制好，以防止氧化。根据材料和工艺参数，烧结过程的持续时间从30分钟到2小时不等，烧结后零件强度非常接近相应固体材料的强度。Text&Translation3.粉末挤压65Text&Translation闭合的型腔形状与期望得到的零件几何形状相对应。挤压机械包括机械压力挤压机和水力压力挤压机两种。生产率为每分钟6～100个零件。4.铸造铸造是将液态材料充满型腔的质量守恒的一种基础机械工艺方法。铸造是最古老的加工方法之一，同时是最广为人知的一种工艺。材料被融化，并灌入根据希望得到的几何形状制作的相应型腔(见图12-1(d)。液体材料充满型腔，随着材料凝固，零件的几何形状最终固定下来。Text&Translation闭合的型腔形状与期望得到66Text&Translation铸造