机械工程英语 (叶邦彦 著) 机械工业出版社 课后答案 56页

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第一单元TypesofMaterials材料的类型Materialsmaybegroupedinseveralways.Scientistsoftenclassifymaterialsbytheirstate:solid,liquid,orgas.Theyalsoseparatethemintoorganic(onceliving)andinorganic(neverliving)materials.材料可以按多种方法分类。科学家常根据状态将材料分为：固体、液体或气体。他们也把材料分为有机材料(曾经有生命的)和无机材料(从未有生命的)。Forindustrialpurposes,materialsaredividedintoengineeringmaterialsornonengineeringmaterials.Engineeringmaterialsarethoseusedinmanufactureandbecomepartsofproducts.就工业效用而言，材料被分为工程材料和非工程材料。那些用于加工制造并成为产品组成部分的就是工程材料。Nonengineeringmaterialsarethechemicals,fuels,lubricants,andothermaterialsusedinthemanufacturingprocess,whichdonotbecomepartoftheproduct.非工程材料则是化学品、燃料、润滑剂以及其它用于加工制造过程但不成为产品组成部分的材料。Engineeringmaterialsmaybefurthersubdividedinto:①Metal②Ceramics③Composite④Polymers,etc.工程材料还能进一步细分为：①金属材料②陶瓷材料③复合材料④聚合材料，等等。•MetalsandMetalAlloyskhdaw.com金属和金属合金Metalsareelementsthatgenerallyhavegoodelectricalandthermalconductivity.Manymetalshavehighstrength,highstiffness,andhavegoodductility.金属就是通常具有良好导电性和导热性的元素。许多金属具有高强度、高硬度以及良好的延展性。Somemetals,suchasiron,cobaltandnickel,aremagnetic.Atlowtemperatures,somemetalsandintermetalliccompoundsbecomesuperconductors.某些金属能被磁化，例如铁、钴和镍。在极低的温度下，某些金属和金属化合物能转变成超导体。课后答案网Whatisthedifferencebetweenanalloyandapuremetal?Puremetalsareelementswhichcomefromaparticularareaoftheperiodictable.Examplesofpuremetalsincludecopperinelectricalwiresandaluminumincookingfoilandbeveragecans.www.hackshp.cn合金与纯金属的区别是什么？纯金属是在元素周期表中占据特定位置的元素。例如电线中的铜和制造烹饪箔及饮料罐的铝。Alloyscontainmorethanonemetallicelement.Theirpropertiescanbechangedbychangingtheelementspresentinthealloy.Examplesofmetalalloysincludestainlesssteelwhichisanalloyofiron,nickel,andchromium;andgoldjewelrywhichusuallycontainsanalloyofgoldandnickel.合金包含不止一种金属元素。合金的性质能通过改变其中存在的元素而改变。金属合金的例子有：不锈钢是一种铁、镍、铬的合金，以及金饰品通常含有金镍合金。Whyaremetalsandalloysused?Manymetalsandalloyshavehighdensitiesandareusedinapplicationswhichrequireahighmass-to-volumeratio.为什么要使用金属和合金？许多金属和合金具有高密度，因此被用在需要较高质量体积比的场合。Somemetalalloys,suchasthosebasedonaluminum,havelowdensitiesandareusedinaerospaceapplicationsforfueleconomy.Manyalloysalsohavehighfracturetoughness,whichmeanstheycanwithstandimpactandaredurable.某些金属合金，例如铝基合金，其密度低，可用于航空航天以节约燃料。许多合金还具有高断裂韧性，这意味着它们能经得起冲击并且是耐用的。Whataresomeimportantpropertiesofmetals?DensityDensDensityityisdefinedasamaterial’smassdividedbyitsvolume.Mostmetalshaverelativelyhighdensities,especiallycomparedtopolymers.金属有哪些重要特性？密度定义为材料的质量与其体积之比。大多数金属密度相对较高，尤其是和聚合物相比较而言。Materialswithhighdensitiesoftencontainatomswithhighatomicnumbers,suchasgoldorlead.However,somemetalssuchasaluminumormagnesiumhavelowdensities,andareusedinapplicationsthatrequireothermetallicpropertiesbutalsorequirelowweight.高密度材料通常由较大原子序数原子构成，例如金和铅。然而，诸如铝和镁之类的一些金属则具有低密度，并被用于既需要金属特性又要求重量轻的场合。khdaw.comFractureFracFractureFracturetoughnessturetougtoughnesshnesscanbedescribedasamaterial’sabilitytoavoidfracture,especiallywhenaflawisintroduced.Metalscangenerallycontainnicksanddentswithoutweakeningverymuch,andareimpactresistant.Afootballplayer若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com countsonthiswhenhetruststhathisfacemaskwon’tshatter.断裂韧性可以描述为材料防止断裂特别是出现缺陷时不断裂的能力。金属一般能在有缺口和凹痕的情况下不显著削弱，并且能抵抗冲击。橄榄球运动员据此相信他的面罩不会裂成碎片。PlasticPlasPlasticPlasticdeformationticdefodeformationrmationistheabilityofbendordeformbeforebreaking.Asengineers,weusuallydesignmaterialssothattheydon’tdeformundernormalconditions.Youdon’twantyourcartoleantotheeastafterastrongwestwind.塑性变形就是在断裂前弯曲或变形的能力。作为工程师，设计时通常要使材料在正常条件下不变形。没有人愿意一阵强烈的西风过后自己的汽车向东倾斜。However,sometimeswecantakeadvantageofplasticdeformation.Thecrumplezonesinacarabsorbenergybyundergoingplasticdeformationbeforetheybreak.然而，有时我们也能利用塑性变形。汽车上压皱的区域在它们断裂前通过经历塑性变形来吸收能量。Theatomicbondingofmetalsalsoaffectstheirproperties.Inmetals,theoutervalenceelectronsaresharedamongallatoms,andarefreetotraveleverywhere.Sinceelectronsconductheatandelectricity,metalsmakegoodcookingpansandelectricalwires.金属的原子连结对它们的特性也有影响。在金属内部，原子的外层阶电子由所有原子共享并能到处自由移动。由于电子能导热和导电，所以用金属可以制造好的烹饪锅和电线。Itisimpossibletoseethroughmetals,sincethesevalenceelectronsabsorbanyphotonsoflightwhichreachthemetal.Nophotonspassthrough.因为这些阶电子吸收到达金属的光子，所以透过金属不可能看得见。没有光子能通过金属。khdaw.comAlloysAlloAlloysysarecompoundsconsistingofmorethanonemetal.Addingothermetalscanaffectthedensity,strength,fracturetoughness,plasticdeformation,electricalconductivityandenvironmentaldegradation.合金是由一种以上金属组成的混合物。加一些其它金属能影响密度、强度、断裂韧性、塑性变形、导电性以及环境侵蚀。Forexample,addingasmallamountofirontoaluminumwillmakeitstronger.Also,addingsomechromiumtosteelwillslowtherustingprocess,butwillmakeitmorebrittle.例如，往铝里加少量铁可使其更强。同样，在钢里加一些铬能减缓它的生锈过程，但也将使它更脆。课后答案网•CeramicsandGlasses陶瓷和玻璃Aceramicisoftenbroadlydefinedasanyinorganicnonmetallicmaterialwww.hackshp.cn．Bythisdefinition,ceramicmaterialswouldalsoincludeglasses;however,manymaterialsscientistsaddthestipulationthat“ceramic”mustalsobecrystalline.陶瓷通常被概括地定义为无机的非金属材料。照此定义，陶瓷材料也应包括玻璃；然而许多材料科学家添加了“陶瓷”必须同时是晶体物组成的约定。Aglassisaninorganicnonmetallicmaterialthatdoesnothaveacrystallinestructure.Suchmaterialsaresaidtobeamorphous.玻璃是没有晶体状结构的无机非金属材料。这种材料被称为非结晶质材料。PropertiesofCeramicsandGlassesSomeoftheusefulpropertiesofceramicsandglassesincludehighmeltingtemperature,lowdensity,highstrength,stiffness,hardness,wearresistance,andcorrosionresistance.陶瓷和玻璃的特性高熔点、低密度、高强度、高刚度、高硬度、高耐磨性和抗腐蚀性是陶瓷和玻璃的一些有用特性。Manyceramicsaregoodelectricalandthermalinsulators.Someceramicshavespecialproperties:someceramicsaremagneticmaterials;somearepiezoelectricmaterials;andafewspecialceramicsaresuperconductorsatverylowtemperatures.Ceramicsandglasseshaveonemajordrawback:theyarebrittle.许多陶瓷都是电和热的良绝缘体。某些陶瓷还具有一些特殊性能：有些是磁性材料，有些是压电材料，还有些特殊陶瓷在极低温度下是超导体。陶瓷和玻璃都有一个主要的缺点：它们容易破碎。Ceramicsarenottypicallyformedfromthemelt.Thisisbecausemostceramicswillcrackextensively(i.e.formapowder)uponcoolingfromtheliquidstate.陶瓷一般不是由熔化形成的。因为大多数陶瓷在从液态冷却时将会完全破碎(即形成粉末)。Hence,allthesimpleandefficientmanufacturingtechniquesusedforglassproductionsuchascastingandblowing,whichinvolvethemoltenstate,cannotbeusedfortheproductionofcrystallineceramics.Instead,“sintering”or“firing”istheprocesstypicallyused.因此，所有用于玻璃生产的简单有效的—诸如浇铸和吹制这些涉及熔化的技术都不能用于由晶体物组成的陶瓷的生产。作为替代，一般采用“烧结”或“焙烧”工艺。khdaw.comInsintering,ceramicpowdersareprocessedintocompactedshapesandthenheatedtotemperaturesjustbelowthemeltingpoint.Atsuchtemperatures,thepowdersreactinternallytoremoveporosityandfullydensearticlescanbe若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com obtained.在烧结过程中，陶瓷粉末先挤压成型然后加热到略低于熔点温度。在这样的温度下，粉末内部起反应去除孔隙并得到十分致密的物品。Anopticalfibercontainsthreelayers:acoremadeofhighlypureglasswithahighrefractiveindexforthelighttotravel,amiddlelayerofglasswithalowerrefractiveindexknownasthecladdingwhichprotectsthecoreglassfromscratchesandothersurfaceimperfections,andanoutpolymerjackettoprotectthefiberfromdamage.光导纤维有三层：核心由高折射指数高纯光传输玻璃制成，中间层为低折射指数玻璃，是保护核心玻璃表面不被擦伤和完整性不被破坏的所谓覆层，外层是聚合物护套，用于保护光导纤维不受损。Inorderforthecoreglasstohaveahigherrefractiveindexthanthecladding,thecoreglassisdopedwithasmall,controlledamountofanimpurity,ordopant,whichcauseslighttotravelslower,butdoesnotabsorbthelight.为了使核心玻璃有比覆层大的折射指数，在其中掺入微小的、可控数量的能减缓光速而不会吸收光线的杂质或搀杂剂。Becausetherefractiveindexofthecoreglassisgreaterthanthatofthecladding,lighttravelinginthecoreglasswillremaininthecoreglassduetototalinternalreflectionaslongasthelightstrikesthecore/claddinginterfaceatananglegreaterthanthecriticalangle.由于核心玻璃的折射指数比覆层大，只要在全内反射过程中光线照射核心/覆层分界面的角度比临界角大，在核心玻璃中传送的光线将仍保留在核心玻璃中。Thetotalinternalreflectionphenomenon,aswellaskhdaw.comthehighpurityofthecoreglass,enableslighttotravellongdistanceswithlittlelossofintensity.全内反射现象与核心玻璃的高纯度一样，使光线几乎无强度损耗传递长距离成为可能。•CompositesCompCompositesosites复合材料Compositesareformedfromtwoormoretypesofmaterials.Examplesincludepolymer/ceramicandmetal/ceramiccomposites.Compositesareusedbecauseoverallpropertiesofthecompositesaresuperiortothoseoftheindividualcomponents.复合材料由两种或更多材料构成。例子有聚合物课后答案网/陶瓷和金属/陶瓷复合材料。之所以使用复合材料是因为其全面性能优于组成部分单独的性能。Forexample:polymer/ceramiccompositeshaveagreatermodulusthanthepolymercomponent,butaren’tasbrittleasceramics.www.hackshp.cnTwotypesofcompositesare:fiber-reinforcedcompositesandparticle-reinforcedcomposites.例如：聚合物/陶瓷复合材料具有比聚合物成分更大的模量，但又不像陶瓷那样易碎。复合材料有两种：纤维加强型复合材料和微粒加强型复合材料。Fiber-reinforcedCompositesReinforcingfiberscanbemadeofmetals,ceramics,glasses,orpolymersthathavebeenturnedintographiteandknownascarbonfibers.Fibersincreasethemodulusofthematrixmaterial.纤维加强型复合材料加强纤维可以是金属、陶瓷、玻璃或是已变成石墨的被称为碳纤维的聚合物。纤维能加强基材的模量。Thestrongcovalentbondsalongthefiber’slengthgivethemaveryhighmodulusinthisdirectionbecausetobreakorextendthefiberthebondsmustalsobebrokenormoved.沿着纤维长度有很强结合力的共价结合在这个方向上给予复合材料很高的模量，因为要损坏或拉伸纤维就必须破坏或移除这种结合。Fibersaredifficulttoprocessintocomposites,makingfiber-reinforcedcompositesrelativelyexpensive.把纤维放入复合材料较困难，这使得制造纤维加强型复合材料相对昂贵。Fiber-reinforcedcompositesareusedinsomeofthemostadvanced,andthereforemostexpensivesportsequipment,suchasatime-trialracingbicycleframewhichconsistsofcarbonfibersinathermosetpolymermatrix.纤维加强型复合材料用于某些最先进也是最昂贵的运动设备，例如计时赛竞赛用自行车骨架就是用含碳纤维的热固塑料基材制成的。Bodypartsofracecarsandsomeautomobilesarecompositesmadeofglassfibers(orfiberglass)inathermosetmatrix.竞赛用汽车和某些机动车的车体部件是由含玻璃纤维(或玻璃丝)的热固塑料基材制成的。Fibershaveaveryhighmodulusalongtheiraxis,buthavealowmodulusperpendiculartotheiraxis.Fibercompositemanufacturersoftenrotatelayersoffiberstoavoiddirectionalvariationsinthemodulus.纤维在沿着其轴向有很高的模量，但垂直于其轴向的模量却较低。纤维复合材料的制造者往往旋转纤维层以防模量产生方向变化。khdaw.comParticle-reinforcedcompositesParticlesusedforreinforcingincludeceramicsandglassessuchassmallmineralparticles,metalparticles若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com suchasaluminum,andamorphousmaterials,includingpolymersandcarbonblack.微粒加强型复合材料用于加强的微粒包含了陶瓷和玻璃之类的矿物微粒，铝之类的金属微粒以及包括聚合物和碳黑的非结晶质微粒。Particlesareusedtoincreasethemodulusofthematrix,todecreasethepermeabilityofthematrix,todecreasetheductilityofthematrix.Anexampleofparticle-reinforcedcompositesisanautomobiletirewhichhascarbonblackparticlesinamatrixofpolyisobutyleneelastomericpolymer.微粒用于增加基材的模量、减少基材的渗透性和延展性。微粒加强型复合材料的一个例子是机动车胎，它就是在聚异丁烯人造橡胶聚合物基材中加入了碳黑微粒。•PolymersPolyPolymersmers聚合材料Apolymerhasarepeatingstructure,usuallybasedonacarbonbackbone.Therepeatingstructureresultsinlargechainlikemolecules.Polymersareusefulbecausetheyarelightweight,corrosionresistant,easytoprocessatlowtemperaturesandgenerallyinexpensive.聚合物具有一般是基于碳链的重复结构。这种重复结构产生链状大分子。由于重量轻、耐腐蚀、容易在较低温度下加工并且通常较便宜，聚合物是很有用的。Someimportantcharacteristicsofpolymersincludetheirsize(ormolecularweight),softeningandmeltingpoints,crystallinity,andstructure.Themechanicalpropertiesofpolymersgenerallyincludelowstrengthandhightoughness.Theirstrengthisoftenimprovedusingreinforcedcompositestructures.khdaw.com聚合材料具有一些重要特性，包括尺寸(或分子量)、软化及熔化点、结晶度和结构。聚合材料的机械性能一般表现为低强度和高韧性。它们的强度通常可采用加强复合结构来改善。ImportantCharacteristicsofPolymersSize.SizeSize..Singlepolymermoleculestypicallyhavemolecularweightsbetween10,000and1,000,000g/mol—thatcanbemorethan2,000repeatingunitsdependingonthepolymerstructure!聚合材料的重要特性尺寸：单个聚合物分子一般分子量为课后答案网10,000到1,000,000g/mol之间，具体取决于聚合物的结构—这可以比2,000个重复单元还多。Themechanicalpropertiesofapolymeraresignificantlyaffectedbythemolecularweight,withbetterengineeringpropertiesathighermolecularweights.www.hackshp.cn聚合物的分子量极大地影响其机械性能，分子量越大，工程性能也越好。ThermalTherThermalmaltrantransitions.sitions.Thesofteningpoint(glasstransitiontemperature)andthemeltingpointofapolymerwilldeterminewhichitwillbesuitableforapplications.Thesetemperaturesusuallydeterminetheupperlimitforwhichapolymercanbeused.热转换性：聚合物的软化点(玻璃状转化温度)和熔化点决定了它是否适合应用。这些温度通常决定聚合物能否使用的上限。Forexample,manyindustriallyimportantpolymershaveglasstransitiontemperaturesneartheboilingpointofwater(100℃,212℉),andtheyaremostusefulforroomtemperatureapplications.Somespeciallyengineeredpolymerscanwithstandtemperaturesashighas300℃(572℉).例如，许多工业上的重要聚合物其玻璃状转化温度接近水的沸点(100℃,212℉)，它们被广泛用于室温下。而某些特别制造的聚合物能经受住高达300℃(572℉)的温度。Crystallinity.CrysCrystallinity.tallinity.Polymerscanbecrystallineoramorphous,buttheyusuallyhaveacombinationofcrystallineandamorphousstructures(semi-crystalline).结晶度：聚合物可以是晶体状的或非结晶质的，但它们通常是晶体状和非结晶质结构的结合物(半晶体)。InterchainInteInterchainInterchaininteractions.rchaininteinteractions.ractions.Thepolymerchainscanbefreetoslidepastoneanother(thermo-plastic)ortheycanbeconnectedtoeachotherwithcrosslinks(thermosetorelastomer).Thermo-plasticscanbereformedandrecycled,whilethermosetsandelastomersarenotreworkable.原子链间的相互作用：聚合物的原子链可以自由地彼此滑动(热可塑性)或通过交键互相连接(热固性或弹性)。热可塑性材料可以重新形成和循环使用，而热固性与弹性材料则是不能再使用的。IntrachainIntIntrachainIntrachainstructure.rachainstrustructure.cture.Thechemicalstructureofthechainsalsohasatremendouseffectontheproperties.Dependingonthestructurethepolymermaybehydrophilicorhydrophobic(likesorhateswater),stifforflexible,crystallineoramorphous,reactiveorunreactive.链内结构：原子链的化学结构对性能也有很大影响。根据各自的结构不同，聚合物可以是亲水的或憎水的(喜欢或讨厌水)、硬的或软的、晶体状的或非结晶质的、易起反应的或不易起反应的。khdaw.com若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 第二单元Theunderstandingofheattreatmentisembracedbythebroaderstudyofmetallurgy.Metallurgyisthephysics,chemistry,andengineeringrelatedtometalsfromoreextractiontothefinalproduct.对热处理的理解包含于对冶金学较广泛的研究。冶金学是物理学、化学和涉及金属从矿石提炼到最后产物的工程学。Heattreatmentistheoperationofheatingandcoolingametalinitssolidstatetochangeitsphysicalproperties.Accordingtotheprocedureused,steelcanbehardenedtoresistcuttingactionandabrasion,oritcanbesoftenedtopermitmachining.热处理是将金属在固态加热和冷却以改变其物理性能的操作。按所采用的步骤，钢可以通过硬化来抵抗切削和磨损，也可以通过软化来允许机加工。Withtheproperheattreatmentinternalstressesmayberemoved,grainsizereduced,toughnessincreased,orahardsurfaceproducedonaductileinterior.Theanalysisofthesteelmustbeknownbecausesmallpercentagesofcertainelements,notablycarbon,greatlyaffectthephysicalproperties.khdaw.com使用合适的热处理可以去除内应力、细化晶粒、增加韧性或在柔软材料上覆盖坚硬的表面。因为某些元素(尤其是碳)的微小百分比极大地影响物理性能，所以必须知道对钢的分析。Alloysteelowetheirpropertiestothepresenceofoneormoreelementsotherthancarbon,namelynickel,chromium,manganese,molybdenum,tungsten,silicon,vanadium,andcopper.Becauseoftheirimprovedphysicalpropertiestheyareusedcommerciallyinmanywaysnotpossiblewithcarbonsteels.合金钢的性质取决于其所含有的除碳以外的一种或多种元素，如镍、铬、锰、钼、钨、硅、钒和铜。由于合金钢改善的物理性能，它们被大量使用在许多碳钢不适用的地方。课后答案网Thefollowingdiscussionappliesprincipallytotheheattreatmentofordinarycommercialsteelsknownasplaincarbonsteels.Withthisprocesstherateofcoolingisthecontrollingfactor,rapidcoolingfromabovethecriticalrangeresultsinhardstructure,whereasverywww.hackshp.cnslowcoolingproducestheoppositeeffect.下列讨论主要针对被称为普通碳钢的工业用钢而言。热处理时冷却速率是控制要素，从高于临界温度快速冷却导致坚硬的组织结构，而缓慢冷却则产生相反效果。•ASimplifiedIron-carbonDiagram简化铁碳状态图Ifwefocusonlyonthematerialsnormallyknownassteels,asimplifieddiagramisoftenused.如果只把注意力集中于一般所说的钢上，经常要用到简化铁碳状态图。Thoseportionsoftheiron-carbondiagramnearthedeltaregionandthoseabove2%carboncontentareoflittleimportancetotheengineerandaredeleted.Asimplifieddiagram,suchastheoneinFig.2.1,focusesontheeutectoidregionandisquiteusefulinunderstandingthepropertiesandprocessingofsteel.铁碳状态图中靠近三角区和含碳量高于2%的那些部分对工程师而言不重要，因此将它们删除。如图2.1所示的简化铁碳状态图将焦点集中在共析区，这对理解钢的性能和处理是十分有用的。Thekeytransitiondescribedinthisdiagramisthedecompositionofsingle-phaseaustenite(γ)tothetwo-phaseferritepluscarbidestructureastemperaturedrops.在此图中描述的关键转变是单相奥氏体(γ)随着温度下降分解成两相铁素体加渗碳体组织结构。Controlofthisreaction,whicharisesduetothedrasticallydifferentcarbonsolubilityofausteniteandferrite,enablesawiderangeofpropertiestobeachievedthroughheattreatment.控制这一由于奥氏体和铁素体的碳溶解性完全不同而产生的反应，使得通过热处理能获得很大范围的特性。Tobegintounderstandtheseprocesses,considerasteeloftheeutectoidcomposition,0.77%carbon,beingslowcooledalonglinex-x’inFig.2.1.Attheuppertemperatures,onlyausteniteispresent,the0.77%carbonbeingdissolvedinsolidsolutionwiththeiron.Whenthesteelcoolsto727℃(1341℉),severalchangesoccursimultaneously.为了理解这些过程，考虑含碳量为0.77%的共析钢，沿着图2.1的x-x’线慢慢冷却。在较高温度时，只存在奥氏体，0.77%的碳溶解在铁里形成固溶体。当钢冷却到727℃(1341℉)时，将同时发生若干变化。TheironwantstochangefromtheFCCaustenitestructuretotheBCCferritestructure,buttheferritecanonlycontain0.02%carboninsolidsolution.khdaw.com铁需要从面心立方体奥氏体结构转变为体心立方体铁素体结构，但是铁素体只能容纳固溶体状态的0.02%的碳。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com Therejectedcarbonformsthecarbon-richcementiteintermetallicwithcompositionFe3C.Inessence,thenetreactionattheeutectoidisaustenite0.77%C→ferrite0.02%C+cementite6.67%C.被析出的碳与金属化合物Fe3C形成富碳的渗碳体。本质上，共析体的基本反应是奥氏体0.77%的碳→铁素体0.02%的碳+渗碳体6.67%的碳。Sincethischemicalseparationofthecarboncomponentoccursentirelyinthesolidstate,theresultingstructureisafinemechanicalmixtureofferriteandcementite.Specimenspreparedbypolishingandetchinginaweaksolutionofnitricacidandalcoholrevealthelamellarstructureofalternatingplatesthatformsonslowcooling.由于这种碳成分的化学分离完全发生在固态中，产生的组织结构是一种细致的铁素体与渗碳体的机械混合物。通过打磨并在弱硝酸酒精溶液中蚀刻制备的样本显示出由缓慢冷却形成的交互层状的薄片结构。Thisstructureiscomposedoftwodistinctphases,buthasitsownsetofcharacteristicpropertiesandgoesbythenamepearlite,becauseofitsresemblancetomother-of-pearlatlowmagnification.这种结构由两种截然不同的状态组成，但它本身具有一系列特性，且因与低倍数放大时的珠母层有类同之处而被称为珠光体。Steelshavinglessthantheeutectoidamountofcarbon(lessthan0.77%)areknownashypo-eutectoidsteels.Considernowthetransformationofsuchamaterialrepresentedbycoolingalongliney-y’inFig.2.1.含碳量少于共析体(低于0.77%)的钢称为亚共析钢。现在来看这种材料沿着图2.1中y-y’线冷却的转变情况。Athightemperatures,thematerialisentirelyaustenite,butuponcoolingentersaregionwherethestablephasesareferriteandaustenite.Tie-lineandlevel-lawcalculationsshowthatlow-carbonferritenucleatesandgrows,leavingthekhdaw.comremainingaustenitericherincarbon.在较高温度时，这种材料全部是奥氏体，但随着冷却就进入到铁素体和奥氏体稳定状态的区域。由截线及杠杆定律分析可知，低碳铁素体成核并长大，剩下含碳量高的奥氏体。At727℃(1341℉),theausteniteisofeutectoidcomposition(0.77%carbon)andfurthercoolingtransformstheremainingaustenitetopearlite.Theresultingstructureisamixtureofprimaryorpro-eutectoidferrite(ferritethatformedabovetheeutectoidreaction)andregionsofpearlite.在727℃(1341℉)时，奥氏体为共析组成课后答案网(含碳量0.77%)，再冷却剩余的奥氏体就转化为珠光体。作为结果的组织结构是初步的共析铁素体(在共析反应前的铁素体)和部分珠光体的混合物。Hypereutectoidsteelsaresteelsthatcontaingreaterthantheeutectoidamountofcarbon.Whensuchsteelcools,asshowninz-z’ofFig.2.1theprocessissimilartothehypo-eutectoidcase,exceptthattheprimaryorpro-eutectoidwww.hackshp.cnphaseisnowcementiteinsteadofferrite.过共析钢是含碳量大于共析量的钢。当这种钢冷却时，就像图2.1的z-z’线所示，除了初步的共析状态用渗碳体取代铁素体外，其余类似亚共析钢的情况。Asthecarbon-richphaseforms,theremainingaustenitedecreasesincarboncontent,reachingtheeutectoidcompositionat727℃(1341℉).Asbefore,anyremainingaustenitetransformstopearliteuponslowcoolingthroughthistemperature.随着富碳部分的形成，剩余奥氏体含碳量减少，在727℃(1341℉)时达到共析组织。就像以前说的一样，当缓慢冷却到这温度时所有剩余奥氏体转化为珠光体。Itshouldberememberedthatthetransitionsthathavebeendescribedbythephasediagramsareforequilibriumconditions,whichcanbeapproximatedbyslowcooling.Withslowheating,thesetransitionsoccurinthereversemanner.应该记住由状态图描述的这种转化只适合于通过缓慢冷却的近似平衡条件。如果缓慢加热，则以相反的方式发生这种转化。However,whenalloysarecooledrapidly,entirelydifferentresultsmaybeobtained,becausesufficienttimeisnotprovidedforthenormalphasereactionstooccur,insuchcases,thephasediagramisnolongerausefultoolforengineeringanalysis.然而，当快速冷却合金时，可能得到完全不同的结果。因为没有足够的时间让正常的状态反应发生，在这种情况下对工程分析而言状态图不再是有用的工具。•HardeningHardHardeningening淬火Hardeningistheprocessofheatingapieceofsteeltoatemperaturewithinoraboveitscriticalrangeandthencoolingitrapidly.淬火就是把钢件加热到或超过它的临界温度范围，然后使其快速冷却的过程。Ifthecarboncontentofthesteelisknown,thepropertemperaturetowhichthesteelshouldbeheatedmaybeobtainedbyreferencetotheiron-ironcarbidephasediagram.However,ifthecompositionofthesteelisunknown,alittlepreliminaryexperimentationmaybenecessarytodeterminetherange.khdaw.com如果钢的含碳量已知，钢件合适的加热温度可参考铁碳合金状态图得到。然而当钢的成分不知道时，则需做一些预备试验来确定其温度范围。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com Agoodproceduretofollowistoheat-quenchanumberofsmallspecimensofthesteelatvarioustemperaturesandobservetheresult,eitherbyhardnesstestingorbymicroscopicexamination.Whenthecorrecttemperatureisobtained,therewillbeamarkedchangeinhardnessandotherproperties.要遵循的合适步骤是将这种钢的一些小试件加热到不同的温度后淬火，再通过硬度试验或显微镜检查观测结果。一旦获得正确的温度，硬度和其它性能都将有明显的变化。Inanyheat-treatingoperationtherateofheatingisimportant.Heatflowsfromtheexteriortotheinteriorofsteelatadefiniterate.Ifthesteelisheatedtoofast,theoutsidebecomeshotterthantheinterioranduniformstructurecannotbeobtained.在任何热处理作业中，加热的速率都是重要的。热量以一定的速率从钢的外部传导到内部。如果钢被加热得太快，其外部比内部热就不能得到均匀的组织结构。Ifapieceisirregularinshape,aslowrateisallthemoreessentialtoeliminatewarpingandcracking.Theheavierthesection,thelongermustbetheheatingtimetoachieveuniformresults.如果工件形状不规则，为了消除翘曲和开裂最根本的是加热速率要缓慢。截面越厚，加热的时间就要越长才能达到均匀的结果。Evenafterthecorrecttemperaturehasbeenreached,thepieceshouldbeheldatthattemperatureforasufficientperiodoftimetopermititsthickestsectiontoattainauniformtemperature.即使加热到正确的温度后，工件也应在此温度下保持足够时间以让其最厚截面达到相同温度。Thehardnessobtainedfromagiventreatmentdependsonthequenchingrate,thecarbonkhdaw.comcontent,andtheworksize.Inalloysteelsthekindandamountofalloyingelementinfluencesonlythehardenability(theabilityoftheworkpiecetobehardenedtodepths)ofthesteelanddoesnotaffectthehardnessexceptinunhardenedorpartiallyhardenedsteels.通过给定的热处理所得到的硬度取决于淬火速率、含碳量和工件尺寸。除了非淬硬钢或部分淬硬钢外，合金钢中合金元素的种类及含量仅影响钢的淬透性(工件被硬化到深层的能力)而不影响硬度。Steelwithlowcarboncontentwillnotrespondappreciablytohardeningtreatment.Asthecarboncontentinsteelincreasesuptoaround0.60%,thepossiblehardnessobtainablealsoincreases.课后答案网含碳量低的钢对淬火处理没有明显的反应。随着钢的含碳量增加到大约0.60%，可能得到的硬度也增加。Abovethispointthehardnesscanbeincreasedonlyslightly,becausesteelsabovetheeutectoidpointaremadeupentirelyofpearliteandcementiteintheannealedstate.Pearliterespondsbesttoheat-treatingoperations;andsteelwww.hackshp.cncomposedmostlyofpearlitecanbetransformedintoahardsteel.高于此点，由于超过共析点钢完全由珠光体和退火状态的渗碳体组成，硬度增加并不多。珠光体对热处理作业响应最好；基本由珠光体组成的钢能转化成硬质钢。Asthesizeofpartstobehardenedincreases,thesurfacehardnessdecreasessomewhateventhoughallotherconditionshaveremainedthesame.Thereisalimittotherateofheatflowthroughsteel.即使所有其它条件保持不变，随着要淬火的零件尺寸的增加其表面硬度也会有所下降。热量在钢中的传导速率是有限的。Nomatterhowcoolthequenchingmediummaybe,iftheheatinsidealargepiececannotescapefasterthanacertaincriticalrate,thereisadefinitelimittotheinsidehardness.However,brineorwaterquenchingiscapableofrapidlybringingthesurfaceofthequenchedparttoitsowntemperatureandmaintainingitatorclosetothistemperature.无论淬火介质怎么冷，如果在大工件中的热量不能比特定的临界速率更快散发，那它内部硬度就会受到明确限制。然而盐水或水淬火能够将被淬零件的表面迅速冷却至本身温度并将其保持或接近此温度。Underthesecircumstancestherewouldalwaysbesomefinitedepthofsurfacehardeningregardlessofsize.Thisisnottrueinoilquenching,whenthesurfacetemperaturemaybehighduringthecriticalstagesofquenching.在这种情况下不管零件尺寸如何，其表面总归有一定深度被硬化。但油淬情况就不是如此，因为油淬时在淬火临界阶段零件表面的温度可能仍然很高。•TemperingTempTemperingering回火Steelthathasbeenhardenedbyrapidquenchingisbrittleandnotsuitableformostuses.Bytemperingordrawing,thehardnessandbrittlenessmaybereducedtothedesiredpointforserviceconditions．快速淬火硬化的钢是硬而易碎的，不适合大多数场合使用。通过回火，硬度和脆性可以降低到使用条件所需要的程度。Asthesepropertiesarereducedthereisalsoadecreaseintensilestrengthandanincreaseintheductilityandtoughnessofthesteel.Theoperationconsistsofreheatingquench-hardenedsteeltosometemperaturebelowthecriticalrangefollowedbyanyrateofcooling.khdaw.com随着这些性能的降低，拉伸强度也降低而钢的延展性和韧性则会提高。回火作业包括将淬硬钢重新加热到低于临界范围的某一温度然后以任意速率冷却。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com Althoughthisprocesssoftenssteel,itdiffersconsiderablyfromannealinginthattheprocesslendsitselftoclosecontrolofthephysicalpropertiesandinmostcasesdoesnotsoftenthesteeltotheextentthatannealingwould.Thefinalstructureobtainedfromtemperingafullyhardenedsteeliscalledtemperedmartensite.虽然这过程使钢软化，但它与退火是大不相同的，因为回火适合于严格控制物理性能并在大多数情况下不会把钢软化到退火那种程度。回火完全淬硬钢得到的最终组织结构被称为回火马氏体。Temperingispossiblebecauseoftheinstabilityofthemartensite,theprincipalconstituentofhardenedsteel.Low-temperaturedraws,from300℉to400℉(150℃~205℃),donotcausemuchdecreaseinhardnessandareusedprincipallytorelieveinternalstrains.由于马氏体这一淬硬钢主要成分的不稳定性，使得回火成为可能。低温回火，300℉到400℉(150℃~205℃)，不会引起硬度下降很多，主要用于减少内部应变。Asthetemperingtemperaturesareincreased,thebreakdownofthemartensitetakesplaceatafasterrate,andatabout600℉(315℃)thechangetoastructurecalledtemperedmartensiteisveryrapid.Thetemperingoperationmaybedescribedasoneofprecipitationandagglomerationorcoalescenceofcementite.随着回火温度的提高，马氏体以较快的速率分解，并在大约600℉(315℃)迅速转变为被称为回火马氏体的结构。回火作业可以描述为渗碳体析出和凝聚或聚结的过程。Asubstantialprecipitationofcementitebeginsat600℉(315℃),whichproducesadecreaseinhardness.Increasingthetemperaturecausescoalescenceofthecarbideswithcontinueddecreaseinhardness.渗碳体的大量析出开始于khdaw.com600℉(315℃)，这使硬度下降。温度的上升会使碳化物聚结而硬度继续降低。Intheprocessoftempering,someconsiderationshouldbegiventotimeaswellastotemperature.Althoughmostofthesofteningactionoccursinthefirstfewminutesafterthetemperatureisreached,thereissomeadditionalreductioninhardnessifthetemperatureismaintainedforaprolongedtime.在回火过程中，不但要考虑温度而且要考虑时间。虽然大多数软化作用发生在达到所需温度后的最初几分钟，但如果此温度维持一段延长时间，仍会有些额外的硬度下降。Usualpracticeistoheatthesteeltothedesiredtemperatureandholditthereonlylongenoughtohaveituniformlyheated.课后答案网通常的做法是将钢加热到所需温度并且仅保温到正好使其均匀受热。Twospecialprocessesusinginterruptedquenchingareaformoftempering.Inboth,thehardenedsteelisquenchedinasaltbathheldataselectedlowertemperaturebeforebeingallowedtocool.Theseprocesses,knownaswww.hackshp.cnaustemperingandmartempering,resultinproductshavingcertaindesirablephysicalproperties.两种采用中断淬火的特殊工艺也是回火的形式。这两种工艺中，淬硬钢在其被允许冷却前先在一选定的较低温度盐浴淬火。这两种分别被称为奥氏体回火和马氏体回火的工艺，能使产品具有特定所需的物理性能。•AnnealingAnneAnnealingaling退火Theprimarypurposeofannealingistosoftenhardsteelsothatitmaybemachinedorcoldworked.退火的主要目的是使坚硬的钢软化以便机加工或冷作。Thisisusuallyaccomplishedbyheatingthesteeltooslightlyabovethecriticaltemperature,holdingitthereuntilthetemperatureofthepieceisuniformthroughout,andthencoolingataslowlycontrolledratesothatthetemperatureofthesurfaceandthatofthecenterofthepieceareapproximatelythesame.通常是非常缓慢地将钢加热到临界温度以上，并将其在此温度下保持到工件全部均匀受热，然后以受控的速率慢慢地冷却，这样使得工件表面和内部的温度近似相同。Thisprocessisknownasfullannealingbecauseitwipesoutalltraceofpreviousstructure,refinesthecrystallinestructure,andsoftensthemetal.Annealingalsorelievesinternalstressespreviouslysetupinthemetal.这过程被称为完全退火，因为它去除了以前组织结构的所有痕迹、细化晶粒并软化金属。退火也释放了先前在金属中的内应力。Thetemperaturetowhichagivensteelshouldbeheatedinannealingdependsonitscomposition;forcarbonsteelsitcanbeobtainedreadilyfromthepartialiron-ironcarbideequilibriumdiagram.Whentheannealingtemperaturehasbeenreached,thesteelshouldbeheldthereuntilitisuniformthroughout.给定的钢其退火温度取决于它的成分；对碳钢而言可容易地从局部的铁碳合金平衡图得到。达到退火温度后，钢应当保持在此温度等到全部均匀受热。Thisusuallytakesabout45minforeachinch(25mm)ofthicknessofthelargestsection.Formaximumsoftnessandductilitythecoolingrateshouldbeveryslow,suchasallowingthepartstocooldownwiththefurnace.Thehigherthecarboncontent,theslowerthisratemustbe.加热时间一般以工件的最大截面厚度计每英寸(25mm)大约需45min。为了得到最大柔软性和延展性冷却速率应该很khdaw.com慢，比如让零件与炉子一起冷下来。含碳量越高，冷却的速率必须越慢。Theheatingrateshouldbeconsistentwiththesizeanduniformityofsections,sothattheentirepartisbroughtupto若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com temperatureasuniformlyaspossible.加热的速率也应与截面的尺寸及均匀程度相协调，这样才能使整个零件尽可能均匀地加热。•NormalizingNormNormalizingNormalizingandalizingandanandSpheroidizingdSpheSpheroidizingroidizing正火和球化Theprocessofnormalizingconsistsofheatingthesteelabout50℉to100℉(10℃~40℃)abovetheuppercriticalrangeandcoolinginstillairtoroomtemperature.正火处理包括先将钢加热到高于上临界区50℉到100℉(10℃~40℃)然后在静止的空气中冷却到室温。Thisprocessisprincipallyusedwithlow-andmedium-carbonsteelsaswellasalloysteelstomakethegrainstructuremoreuniform,torelieveinternalstresses,ortoachievedesiredresultsinphysicalproperties.Mostcommercialsteelsarenormalizedafterbeingrolledorcast.退火主要用于低碳钢、中碳钢及合金钢，使晶粒结构更均匀、释放内应力或获得所需的物理特性。大多数商业钢材在轧制或铸造后都要退火。Spheroidizingistheprocessofproducingastructureinwhichthecementiteisinaspheroidaldistribution.Ifsteelisheatedslowlytoatemperaturejustbelowthecriticalrangeandheldthereforaprolongedperiodoftime,thisstructurewillbeobtained.球化是使渗碳体产生成类似球状分布结构的工艺。如果把钢缓慢加热到恰好低于临界温度并且保持较长一段时间，就能得到这种组织结构。Theglobularstructureobtainedgivesimprovedmachinabilitytothesteel.Thistreatmentisparticularlyusefulforkhdaw.comhypereutectoidsteelsthatmustbemachined.所获得的球状结构改善了钢的可切削性。此处理方法对必须机加工的过共析钢特别有用。•SurfaceSurfSurfaceSurfaceHardeningaceHardHardeningening表面硬化CarburizingCarbCarburizingurizingTheoldestknownmethodofproducingahardsurfaceonsteeliscasehardeningorcarburizing.Ironattemperaturesclosetoandaboveitscriticaltemperaturehasanaffinityforcarbon.课后答案网渗碳最早的硬化钢表面的方法是表面淬火或渗碳。铁在靠近并高于其临界温度时对碳具有亲合力。Thecarbonisabsorbedintothemetaltoformasolidsolutionwithironandconvertstheoutersurfaceintohigh-carbonwww.hackshp.cnsteel.Thecarbonisgraduallydiffusedtotheinteriorofthepart.Thedepthofthecasedependsonthetimeandtemperatureofthetreatment.碳被吸收进金属与铁形成固溶体使外表面转变成高碳钢。碳逐渐扩散到零件内部。渗碳层的深度取决于热处理的时间和温度。Packcarburizingconsistsofplacingthepartstobetreatedinaclosedcontainerwithsomecarbonaceousmaterialsuchascharcoalorcoke.Itisalongprocessandusedtoproducefairlythickcasesoffrom0.03to0.16in.(0.76~4.06mm)indepth.固体渗碳的方法是将要处理的零件与木炭或焦炭这些含碳的材料一起放入密闭容器。这是一个较长的过程，用于产生深度为0.03到0.16英寸(0.76~4.06mm)这么厚的硬化层。Steelforcarburizingisusuallyalow-carbonsteelofabout0.15%carbonthatwouldnotinitselfrespondsappreciablytoheattreatment.Inthecourseoftheprocesstheouterlayerisconvertedintohigh-carbonsteelwithacontentrangingfrom0.9%to1.2%carbon.用于渗碳的一般是含碳量约为0.15%、本身不太适合热处理的低碳钢。在处理过程中外层转化为含碳量从0.9%到1.2%的高碳钢。Asteelwithvaryingcarboncontentand,consequently,differentcriticaltemperaturesrequiresaspecialheattreatment.含碳量变化的钢具有不同的临界温度，因此需要特殊的热处理。Becausethereissomegraingrowthinthesteelduringtheprolongedcarburizingtreatment,theworkshouldbeheatedtothecriticaltemperatureofthecoreandthencooled,thusrefiningthecorestructure.Thesteelshouldthenbereheatedtoapointabovethetransformationrangeofthecaseandquenchedtoproduceahard,finestructure.由于在较长的渗碳过程中钢内部会有些晶粒生长，所以工件应该加热到核心部分的临界温度再冷却以细化核心部分的组织结构。然后重新加热到高于外层转变温度再淬火以生成坚硬、细致的组织结构。Thelowerheat-treatingtemperatureofthecaseresultsfromthefactthathypereutectoidsteelsarenormallyaustenitizedforhardeningjustabovethelowercriticalpoint.Athirdtemperingtreatmentmaybeusedtoreducestrains.由于恰好高于低临界温度通常使过共析钢奥氏体化而硬化，所以对外层采用较低的热处理温度。第三次回khdaw.com火处理可用于减少应变。CarbonitridingCarbCarbonitridingonitriding若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com Carbonitriding,sometimesknownasdrycyanidingornicarbing,isacase-hardeningprocessinwhichthesteelisheldatatemperatureabovethecriticalrangeinagaseousatmospherefromwhichitabsorbscarbonandnitrogen.碳氮共渗碳氮共渗，有时也称为干法氰化或渗碳氮化，是一种表面硬化工艺。通过把钢放在高于临界温度的气体中，让它吸收碳和氮。Anycarbon-richgaswithammoniacanbeused.Thewear-resistantcaseproducedrangesfrom0.003to0.030inch(0.08~0.76mm)inthickness.Anadvantageofcarbonitridingisthatthehardenabilityofthecaseissignificantlyincreasedwhennitrogenisadded,permittingtheuseoflow-coststeels.可以使用任何富碳气体加氨气，能生成厚度从0.003到0.030英寸(0.08~0.76mm)的耐磨外层。碳氮共渗的优点之一是加入氮后外层的淬透性极大增加，为使用低价钢提供条件。CyanidingCyanCyanidingidingCyaniding,orliquidcarbonitridingasitissometimescalled,isalsoaprocessthatcombinestheabsorptionofcarbonandnitrogentoobtainsurfacehardnessinlow-carbonsteelsthatdonotrespondtoordinaryheattreatment.氰化氰化，有时称为液体碳氮共渗，也是一种结合了吸收碳和氮来获得表面硬度的工艺，它主要用于不适合通常热处理的低碳钢。TheparttobecasehardenedisimmersedinabathoffusedsodiumcyanidesaltsatatemperatureslightlyabovetheAc1range,thedurationofsoakingdependingonthedepthofthecase.Thepartisthenquenchedinwateroroiltoobtainakhdaw.comhardsurface.需表面硬化的零件浸没在略高于Ac1温度熔化的氰化钠盐溶液中，浸泡的持续时间取决于硬化层的深度。然后将零件在水或油中淬火。Casedepthsof0.005to0.015in.(0.13~0.38mm)maybereadilyobtainedbythisprocess.Cyanidingisusedprincipallyforthetreatmentofsmallparts.通过这样处理可以容易地获得0.005到0.015英寸(0.13~0.38mm)的硬化深度。氰化主要用于处理小零件。NitridingNitrNitridingiding课后答案网Nitridingissomewhatsimilartoordinarycasehardening,butitusesadifferentmaterialandtreatmenttocreatethehardsurfaceconstituents.渗氮www.hackshp.cn渗氮有些类似普通表面硬化，但它采用不同的材料和处理方法来产生坚硬表面成分。Inthisprocessthemetalisheatedtoatemperatureofaround950℉(510℃)andheldthereforaperiodoftimeincontactwithammoniagas.Nitrogenfromthegasisintroducedintothesteel,formingveryhardnitridesthatarefinelydispersedthroughthesurfacemetal.这种工艺中金属加热到约950℉(510℃)，然后与氨气接触一段时间。氨气中的氮进入钢内，形成细微分布于金属表面又十分坚固的氮化物。Nitrogenhasgreaterhardeningabilitywithcertainelementsthanwithothers,hence,specialnitridingalloysteelshavebeendeveloped.氮与某些元素的硬化能力比其它元素大，因此开发了专用的渗氮合金钢。Aluminumintherangeof1%to1.5%hasprovedtobeespeciallysuitableinsteel,inthatitcombineswiththegastoformaverystableandhardconstituent.Thetemperatureofheatingrangesfrom925℉to1,050℉(495℃~565℃).在钢中含铝1%到1.5%被证明特别合适，它能与氨气结合形成很稳定坚固的成分。其加热温度范围为925℉到1,050℉(495℃~565℃)。Liquidnitridingutilizesmoltencyanidesaltsand,asingasnitriding,thetemperatureisheldbelowthetransformationrange.Liquidnitridingaddsmorenitrogenandlesscarbonthaneithercyanidingorcarburizingincyanidebaths.液体渗氮利用熔化的氰化物盐，就像气体渗氮，温度保持在低于转化范围内。液体渗氮时在氰化物溶液中加入比氰化及渗碳都较多的氮和较少的碳。Casethicknessof0.001to0.012in.(0.03~0.30mm)isobtained,whereasforgasnitridingthecasemaybeasthickas0.025in.(0.64mm).Ingeneraltheusesofthetwo-nitridingprocessesaresimilar.液体渗氮可以获得厚度为0.001到0.012英寸(0.03~0.30mm)的硬化层，然而气体渗氮则能获得厚0.025英寸(0.64mm)的硬化层。一般而言两种渗氮方法的用途是类似的。Nitridingdevelopsextremehardnessinthesurfaceofsteel.Thishardnessrangesfrom900to1,100Brinell,whichisconsiderablyhigherthanthatobtainedbyordinarycasehardening.khdaw.com渗氮在钢表面获得远远超出正常标准的硬度。其硬度范围为900到1,100布氏硬度，这远高于普通表面硬化所获得的硬度。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com Nitridingsteels,byvirtueoftheiralloyingcontent,arestrongerthanordinarysteelsandrespondreadilytoheattreatment.Itisrecommendedthatthesesteelsbemachinedandheat-treatedbeforenitriding,becausethereisnoscaleorfurtherworknecessaryafterthisprocess.由于渗氮钢的合金比例，它们比普通钢更强，也容易热处理。建议对这种钢在渗氮前先机加工和热处理，因为渗氮后没有剥落并不需要更多的加工。Fortunately,theinteriorstructureandpropertiesarenotaffectedappreciablybythenitridingtreatmentand,becausenoquenchingisnecessary,thereislittletendencytowarp,developcracks,orchangeconditioninanyway.Thesurfaceeffectivelyresistscorrosiveactionofwater,saltwaterspray,alkalies,crudeoil,andnaturalgas.值得庆幸的是由于渗氮处理一点都不影响内部结构和性能，也无需淬火，所以几乎没有任何产生翘曲、裂缝及变化条件的趋势。这种表面能有效地抵御水、盐雾、碱、原油和天然气的腐蚀反应。第三单元Castingisamanufacturingprocessinwhichmoltenmetalispouredorinjectedandallowedtosolidifyinasuitablyshapedmoldcavity.Duringoraftercooling,thecastpartisremovedfromthemoldandthenprocessedfordelivery.铸造是一种将熔化的金属倒入或注入合适的铸模腔并且在其中固化的制造工艺。在冷却期间或冷却后，把铸件从铸模中取出，然后进行交付。khdaw.comCastingprocessesandcast-materialtechnologiesvaryfromsimpletohighlycomplex.Materialandprocessselectiondependsonthepart’scomplexityandfunction,theproduct’squalityspecifications,andtheprojectedcostlevel.铸造工艺和铸造材料技术从简单到高度复杂变化很大。材料和工艺的选择取决于零件的复杂性和功能、产品的质量要求以及成本预算水平。Castingsarepartsthataremadeclosetotheirfinaldimensionsbyacastingprocess.Withahistorydatingback6,000years,thevariouscastingprocessesare课后答案网inastateofcontinuousrefinementandevolutionastechnologicaladvancesarebeingmade.通过铸造加工，铸件可以做成很接近它们的最终尺寸。回溯6,000年历史，各种各样的铸造工艺就如同科技进步一样处于一个不断改进和发展的状态。www.hackshp.cn•SandCasting砂型铸造Sandcastingisusedtomakelargeparts(typicallyiron,butalsobronze,brass,aluminum).Moltenmetalispouredintoamoldcavityformedoutofsand(naturalorsynthetic).砂型铸造用于制造大型零件(具有代表性是铁，除此之外还有青铜、黄铜和铝)。将熔化的金属倒入由型砂(天然的或人造的)做成铸模腔。Theprocessesofsandcastingarediscussedinthissection,includingpatterns,spruesandrunners,designconsiderations,andcastingallowance.本节讨论砂型铸造工艺，包括型模、浇注口、浇道、设计考虑因素及铸造余量。Thecavityinthesandisformedbyusingapattern(anapproximateduplicateoftherealpart),whicharetypicallymadeoutofwood,sometimesmetal.Thecavityiscontainedinanaggregatehousedinaboxcalledtheflask.砂型里的型腔是采用型模(真实零件的近似复制品)构成的，型模一般为木制，有时也用金属制造。型腔整个包含在一个被放入称为砂箱的箱子里的组合体内。Coreisasandshapeinsertedintothemoldtoproducetheinternalfeaturesofthepartsuchasholesorinternalpassages.Coresareplacedinthecavitytoformholesofthedesiredshapes.Coreprintistheregionaddedtothepattern,core,ormoldthatisusedtolocateandsupportthecorewithinthemold.砂芯是插入铸模的砂型，用于生成诸如孔或内通道之类的内部特征。砂芯安放在型腔里形成所需形状的孔洞。砂芯座是加在型模、砂芯或铸模上的特定区域，用来在铸模内部定位和支撑砂芯。Ariserisanextravoidcreatedinthemoldtocontainexcessivemoltenmaterial.Thepurposeofthisistofeedthemoltenmetaltothemoldcavityasthemoltenmetalsolidifiesandshrinks,andtherebypreventsvoidsinthemaincasting.冒口是在铸模内部增加的额外空间，用于容纳过多的熔化金属。其目的是当熔化金属凝固和收缩时往型腔里补充熔化金属，从而防止在主铸件中产生孔隙。Inatwo-partmold,whichistypicalofsandcastings,theupperhalf,includingthetophalfofthepattern,flask,andcoreiscalledcopeandthelowerhalfiscalleddrag,asshowninFig.3.1.Thepartinglineorthepartingsurfaceislineorsurfacethatseparatesthecopeanddrag.khdaw.com在典型砂型铸造的两箱铸模中，上半部分(包括型模顶半部、砂箱和砂芯)称为上型箱，下半部分称为下型箱，见图3.1所示。分型线或分型面是分离上下型箱的线或面。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com Thedragisfirstfilledpartiallywithsand,andthecoreprint,thecores,andthegatingsystemareplacednearthepartingline.Thecopeisthenassembledtothedrag,andthesandispouredonthecopehalf,coveringthepattern,coreandthegatingsystem.首先往下型箱里部分地填入型砂和砂芯座、砂芯，并在靠近分型线处放置浇注系统。然后将上型箱与下型箱装配在一起，再把型砂倒入上型箱盖住型模、砂芯和浇注系统。Thesandiscompactedbyvibrationandmechanicalmeans.Next,thecopeisremovedfromthedrag,andthepatterniscarefullyremoved.Theobjectistoremovethepatternwithoutbreakingthemoldcavity.型砂通过振动和机械方法压实。然后从下型箱上撤掉上型箱，小心翼翼地取出型模。其目的是取出型模而不破坏型腔。Thisisfacilitatedbydesigningadraft,aslightangularoffsetfromtheverticaltotheverticalsurfacesofthepattern.Thisisusuallyaminimumof1.5mm(0.060in.),whicheverisgreater.Therougherthesurfaceofthepattern,themorethedrafttobeprovided.通过设计拔模斜度—型模垂直相交表面的微小角度偏移量—来使取出型模变得容易。拔模斜度最小一般为1.5mm(0.060in.)，只能比此大。型模表面越粗糙，则拔模斜度应越大。Themoltenmaterialispouredintothepouringcup,whichispartofthegatingsystemthatsuppliesthemoltenmaterialtothemoldcavity.熔化的金属从浇注杯注入型腔，浇注杯是浇注系统向型腔提供熔化金属的部分。Theverticalpartofthegatingsystemconnectedtothepouringcupisthesprue,andthehorizontalportioniscalledthekhdaw.comrunnersandfinallytothemultiplepointswhereitisintroducedtothemoldcavitycalledthegates.将浇注系统的垂直部分与浇注杯连接的是浇注口，浇注系统的水平部分称为浇道，最后到多点把熔化金属导入型腔的称为闸道。Additionallythereareextensionstothegatingsystemcalledventsthatprovidethepathforthebuilt-upgasesandthedisplacedairtoventtotheatmosphere.除此之外，还有称为排放口的浇注系统延长段，它为合成气体和置换空气排放到大气提供通道。Thecavityisusuallymadeoversizetoallowforthemetalcontractionasitcoolsdowntoroomtemperature.课后答案网Thisisachievedbymakingthepatternoversize.Toaccountforshrinking,thepatternmustbemadeoversizebythesefactorsontheaverage.Thesearelinearfactorsandapplyineachdirection.型腔通常大于所需尺寸以允许在金属冷却到室温时收缩。这通过把型模做得大于所需尺寸来达到。为解决www.hackshp.cn收缩效应，一般而言型模做得比所需尺寸大，必须考虑线性因素并作用于各个方向。Theseshrinkageallowancesareonlyapproximate,becausetheexactallowanceisdeterminedbytheshapeandsizeofthecasting.Inaddition,differentpartsofthecastingmightrequiredifferentshrinkageallowances.收缩余量仅仅是近似的，因为准确的余量是由铸件的形状和尺寸决定的。另外，铸件的不同部分也可能需要不同的收缩余量。Sandcastingsgenerallyhavearoughsurfacesometimeswithsurfaceimpurities,andsurfacevariations.Amachining(finish)allowanceismadeforthistypeofdefect.砂型铸件一般表面粗糙，有时还带有表面杂质和表面变异。对这类缺陷采用机加工(最后一道工序)的余量。Ingeneral,typicalstagesofsandcastingoperationinclude(asshowninFig.3.2):1.Patternsaremade.Thesewillbetheshapeusedtoformthecavityinthesand.一般而言，砂型铸造作业的典型阶段包括(如图3.2所示)：1.制作型模。做成用于在型砂中形成型腔的形状。2.Coresmayalsobemadeatthistime.Thesecoresaremadeofbondedsandthatwillbebrokenoutofthecastpartafteritiscomplete.3.Sandismulled(mixed)thoroughlywithadditivessuchasbentonitetoincreasebondingandoverallstrength.2.同时还要制作砂芯。这些砂芯用粘结砂做成，等铸件完成后将被打碎取出。3.型砂与膨润土之类的添加剂充分地混合以增强连接及整体强度。4.Sandisformedaboutthepatterns,andgates,runners,risers,ventsandpouringcupsareaddedasneeded.Acompactionstageistypicallyusedtoensuregoodcoverageandsolidmolds.4.型砂在型模周围成形，并根据需要安放闸道、浇道、冒口、排放口和浇注杯等。通常要采取压紧步骤来保证良好的覆盖和坚固的铸型。Coresmayalsobeaddedtomakeconcaveorinternalfeaturesforthecastpart.Alignmentpinsmayalsobeusedformatingthemoldslater.Chillsmaybeaddedtocoollargemassesfaster.安放砂芯来制成铸件的凹形结构或内部特征。为了以后铸模匹配还要用到定位销。对大质量铸件可能需要加入冷却khdaw.com物来使其较快冷却。5.Thepatternsareremoved,andthemoldsmaybeputthroughabakingstagetoincreasestrength.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 6.Moldhalvesarematedandpreparedforpouringmetal.5.取走型模，将铸模烘焙以增加强度。6.匹配上下铸模，做好浇铸金属的准备。7.Metalispreheatedinafurnaceorcrucibleuntilisabovetheliquidustemperatureinasuitablerange(wedon’twantthemetalsolidifyingbeforethepouriscomplete).Theexacttemperaturemaybecloselycontrolleddependingupontheapplication.7.金属在熔炉或坩埚中预热到高于液化温度的一个合适范围内(不希望金属在浇铸完成前凝固)。确切的温度要根据应用场合严格控制。Degassing,andothertreatmentprocessesmaybedoneatthistime,suchasremovalofimpurities(i.e.slag).Someportionofthismetalmayberemeltedscrapfrompreviouslycastparts—10%isreasonable.在此期间还要进行排气和其它处理步骤，例如去除杂质(即熔渣)。可以加入一定量原先是这种金属铸件的废料再融化—10%是适当的。8.Themetalispouredslowly,butcontinuouslyintothemolduntilthemoldisfull.9.Asthemoltenmetalcools(minutestodays),themetalwillshrinkandthevolumewilldecrease.Duringthistimemoltenmetalmaybackflowfromthemoltenriserstofeedthepartandmaintainthesameshape.8.将金属缓慢而连续地注满型模。9.随着熔化金属的冷却(几分钟到几天)，金属收缩体积减小。在此期间熔化金属可能从冒口回流供给零件以保持其形状不变。khdaw.com10.Oncethepartstartstosolidifysmalldendritesofsolidmaterialforminthepart.Duringthistimemetalpropertiesarebeingdetermined,andinternalstressesarebeinggenerated.Ifapartisallowedtocoolslowlyenoughataconstantratethenthefinalpartwillberelativelyhomogenousandstressfree.10.在零件开始凝固其内部形成固态金属的小型树枝状结晶期间金属性能被确定，同时也产生了内应力。如果零件以恒定速率冷却得足够缓慢，最终零件将相对均质并释放内应力。11.Oncetheparthascompletelysolidifiedbelowtheeutecticpointitmayberemovedwithnoconcernforfinalmetalproperties.Atthispointthesandissimplybrokenup,andthepartremoved.Atthispointthesurfacewillhaveaquantity课后答案网ofsandadheringtothesurface,andsolidcoresinside.11.一旦零件在共析点以下完全凝固，可以不考虑金属的最后性能而将其取出。这时可以简单地打碎砂型并取出零件，但零件表面会有大量型砂粘附着，内部还有实心的砂芯。www.hackshp.cn12.Abulkoftheremainingsandandcorescanberemovedbymechanicallystrikingthepart.Otheroptionsaretouseavibratingtable,sand/shotblaster,handlabor,etc.12.大量的剩余型砂和砂芯要通过机械敲击零件来去除。其它的选择还有采用振动台、喷砂/喷丸机、手工作业等等。13.Thefinalpartiscutofftherunnergatesystem,andisnearfinalshapeusingcutters,torches,etc.Grindingoperationsareusedtoremoveanyremainingbulk.14.Thepartistakendowntofinalshapeusingmachiningoperations.Andcleaningoperationsmaybeusedtoremoveoxides,etc.13.最后零件要用刀具、喷枪等切掉浇道闸道系统，这样就接近最终形状了。再用磨削作业去除多余的部分。14.通过机加工将零件切削到最终形状。可能还要用清洗作业去除氧化物等。•Investmentcasting熔模铸造Investmentcastingisalsoknownasthelostwaxprocess.Thisprocessisoneoftheoldestmanufacturingprocesses.TheEgyptiansuseditinthetimeofthePharaohstomakegoldjewelry(hencethenameInvestment)some5,000yearsago.熔模铸造也称为失蜡加工。这是最古老的制造工艺之一。大约在5,000年前的法老王时代，埃及人就用它制造黄金饰品(因此而得名投资)。Intricateshapescanbemadewithhighaccuracy.Inaddition,metalsthatarehardtomachineorfabricatearegoodcandidatesforthisprocess.Itcanbeusedtomakepartsthatcannotbeproducedbynormalmanufacturingtechniques,suchasturbinebladesthathavecomplexshapes,orairplanepartsthathavetowithstandhightemperatures.复杂的形状能被高精度地制造。另外较难机加工或制作的金属都能用此工艺。它还能用于生产一般制造技术无法生产的零件，例如有复杂形状的涡轮叶片或必须耐得住高温的飞机零件。Themoldismadebymakingapatternusingwaxorsomeothermaterialthatcanbemeltedaway.Thiswaxpatternisdippedinrefractoryslurry,whichcoatsthewaxpatternandformsaskin.Thisisdriedandtheprocessofdippingintheslurryanddryingisrepeateduntilarobustthicknessisachieved.khdaw.com制作铸型的型模采用石蜡或其它一些能被融化掉的材料做成。石蜡型模浸泡在耐热浆里，让它覆盖型模并形成外壳，然后使其变干。重复这个浸泡、变干的过程直至获得足够的厚度。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com Afterthis,theentirepatternisplacedinanovenandthewaxismeltedaway.Thisleadstoamoldthatcanbefilledwiththemoltenmetal.Becausethemoldisformedaroundaone-piecepattern(whichdoesnothavetobepulledoutfromthemoldasinatraditionalsandcastingprocess),veryintricatepartsandundercutscanbemade.完成后把整个型模放在烤箱里融化石蜡。这样就做成了能填充熔化金属的铸型。由于这种铸型是环绕整块型模形成的(无需像传统的砂型铸造工艺那样拔模)，能制作十分复杂的零件和浮雕。Thewaxpatternitselfismadebyduplicatingusingastereolithographyorsimilarmodel—whichhasbeenfabricatedusingacomputersolidmodelmaster.石蜡型模本身能用立体制版或类似的模型复制—这可以采用计算机立体模型原版制作。Thematerialsusedfortheslurryareamixtureofplaster,abinderandpowderedsilica,arefractory,forlowtemperaturemelts.Forhighertemperaturemelts,sillimaniteoralumina-silicateisusedasarefractory,andsilicaisusedasabinder.对较低熔化温度而言，用于耐热浆的材料是石膏作粘合剂和用粉末状硅石作耐温材料的混合物。对较高熔化温度而言，则采用硅线石或氧化铝硅酸盐作耐温材料、无水硅酸作粘合剂。Dependingonthefinenessofthefinishdesiredadditionalcoatingsofsillimaniteandethylsilicatemaybeapplied.Themoldthusproducedcanbeuseddirectlyforlightcastings,orbereinforcedbyplacingitinalargercontainerandreinforcingitmoreslurry.根据最后所需光洁度也可采用硅线石和乙烷基硅酸盐。这样生成的铸模可直接用于薄壁铸件或通过将其放在较大容器内用更多耐热浆加强。khdaw.comJustbeforethepour,themoldispre-heatedtoabout1,000℃(1,832℉)toremoveanyresiduesofwax,hardenthebinder.Thepourinthepre-heatedmoldalsoensuresthatthemoldwillfillcompletely.在正要浇铸之前，将型模预热到约1,000℃(1,832℉)以去除剩余石蜡、硬化粘合剂。在预热的型模中浇铸也能保证型模完全充满。Pouringcanbedoneusinggravity,pressureorvacuumconditions.Attentionmustbepaidtomoldpermeabilitywhenusingpressure,toallowtheairtoescapeasthepourisdone.浇铸可采用重力、压力或真空条件来实现。当使用压力时必须注意渗透性，以便在浇铸的同时让空气逸出课后答案网。Tolerancesof0.5%oflengthareroutinelypossible,andaslowas0.15%ispossibleforsmalldimensions.Castingscanweighfromafewgramsto35kg(0.1ozto80lb),althoughthenormalsizerangesfrom200gtoabout8kg(7ozto15lb).Normalminimumwallthicknessesareabout1mmtoabout0.5mm(0.040~0.020www.hackshp.cnin.)foralloysthatcanbecasteasily.一般公差可能为长度的0.5%，小尺寸可能低到0.15%。虽然通常尺寸的铸件重量范围为200g到约8kg(7oz到15lb)，但实际可从几克到35kg(0.1ozto80lb)。对容易铸造的合金而言，通常壁厚约为1mm到0.5mm(0.040~0.020in.)。Thetypesofmaterialsthatcanbecastarealuminumalloys,bronzes,toolsteels,stainlesssteels,stellite,hastelloys,andpreciousmetals.Partsmadewithinvestmentcastingsoftendonotrequireanyfurthermachining,becauseoftheclosetolerancesthatcanbeachieved.可以用于铸造的材料类型有：铝合金、青铜、工具钢、不锈钢、钨铬钴合金、镍基合金和贵金属。采用熔模铸造的零件常常不需要进一步加工，因为熔模铸造能达到精密的公差。•CentrifugalCasting离心铸造Centrifugalcasting(Fig.3.3)asacategoryincludescentrifugalcasting,semi-centrifugalcastingandcentrifuging.Incentrifugalcasting,apermanentmoldisrotatedaboutitsaxisathighspeeds(300to3,000rpm)asthemoltenmetalispoured.离心铸造(图3.3)作为一个种类包括了离心铸造、半离心铸造和离心法铸造。离心铸造中，永久性的型模在熔化金属浇铸时以较高速度(300到3,000rpm)绕其轴线旋转。Themoltenmetaliscentrifugallythrowntowardstheinsidemoldwall,whereitsolidifiesaftercooling.Thecastingisusuallyafinegraincastingwithaveryfine-grainedouterdiameter,whichisresistanttoatmosphericcorrosion,atypicalsituationwithpipes.Theinsidediameterhasmoreimpuritiesandinclusions,whichcanbemachinedaway.受离心力作用熔化金属被抛向型模的内壁，在那里冷却后固化。这种铸件通常为外径处晶粒非常细小的细晶粒铸件，能耐大气腐蚀，典型的情况是管子。内径处则有较多的杂质和内含物，但可用机加工去除。Onlycylindricalshapescanbeproducedwiththisprocess.Sizelimitsareupto3m(10feet)diameterand15m(50feet)length.Wallthicknesscanbe2.5mmto125mm(0.1~5.0in.).ThetolerancesthatcanbeheldontheODcanbeasgoodas2.5mm(0.1in.)andontheIDcanbe3.8mm(0.15in.).Thesurfacefinishrangesfrom2.5mmto12.5mm(0.1~0.5in.)rms(root-mean-square).khdaw.com只有圆柱形才能用此工艺生产。尺寸限制为直径大到3m(10feet)、长度大到15m(50feet)。壁厚为2.5mm到125mm(0.1~5.0in.)。外径公差保持在2.5mm(0.1in.)以内，内径公差保持在3.8mm(0.15in.)以内。表面粗糙度的有效值若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com (均方根)范围为2.5mm到12.5mm(0.1~0.5in.)。Typicalmaterialsthatcanbecastwiththisprocessareiron,steel,stainlesssteels,andalloysofaluminum,copperandnickel.Twomaterialscanbecastbyintroducingasecondmaterialduringtheprocess.Typicalpartsmadebythisprocessarepipes,boilers,pressurevessels,flywheels,cylinderlinersandotherpartsthatareaxis-symmetric.可用此工艺铸造的典型材料有：铁、钢、不锈钢以及铝、铜和镍的合金。通过在生产过程中加入第二种材料能进行两种材料铸造。采用这种工艺制造的典型零件有：管子、锅炉、压力容器、飞轮、汽缸衬垫和其它轴对称零件。Semi-centrifugalSemiSemi-centrifugalSemi-centrifugalcasting.-centrifugalcastcasting.ing.Themoldsusedcanbepermanentorexpendable,canbestackedasnecessary.Therotationalspeedsarelowerthanthoseusedincentrifugalcasting.半离心铸造：型模可以是永久性的或是消耗性的，可根据需要叠加。它的旋转速度比离心铸造低。Thecenteraxisoftheparthasinclusiondefectsaswellasporosityandthusissuitableonlyforpartswherethiscanbemachinedaway.Thisprocessisusedformakingwheels,nozzlesandsimilarpartswheretheaxisofthepartisremovedbysubsequentmachining.零件的中心轴附近存在缺陷和孔隙，因此仅适用于能将这些机加工去除的零件。这种工艺被用于制造车轮、管嘴及类似的随后可用机加工去除中心轴部分的零件。Centrifuging.CentCentrifuging.rifuging.Centrifugingisusedforforcingmetalfromacentralaxisoftheequipmentintoindividualmoldcavitiesthatareplacedonthecircumference.Thisprovidesameansofincreasingthefillingpressurewithineachmoldandallowsforreproductionofintricatedetails.Thismethodisoftenusedforthepouringofinvestmentcastingpattern.khdaw.com离心法铸造：离心法铸造用于迫使金属从设备的中心轴进入分布在圆周上的单独型腔。它为每个型腔提供了一种增加填充压力方法并允许再现复杂细节。这种方法常用于浇铸熔模铸型。Full-moldFullFull-moldFull-moldcasting-moldcastcastingingisatechniquesimilartoinvestmentcasting,butinsteadofwaxastheexpendablematerial,polystyrenefoamisusedasthepattern.Thefoampatterniscoatedwitharefractorymaterial.Thepatternisencasedinaone-piecesandmold.Asthemetalispoured,thefoamvaporizes,andthemetaltakesitsplace.实型铸造是与熔模铸造类似的技术，但它用做型模的消耗材料是聚苯乙烯泡沫而不是石蜡。泡沫型模用难熔材料覆盖。型模装入整体砂模中。当金属浇入时，泡沫材料蒸发，金属取代其位置。课后答案网Thiscanmakecomplexshapedcastingswithoutanydraftorflash.However,thepatterncostcanbehighduetotheexpendablenatureofthepattern.Minimumwallthicknessesare2.5mm,tolerancescanbeheldto0.3%ondimensions.Surfacefinishcanbeheldfrom2.5μmto25μm(0.1μin.to1.0μin.)rms(root-mean-square).www.hackshp.cn它能制造没有拔模斜度和缝脊的复杂形状铸件。然而由于型模的消耗特性，型模成本可能较高。最小壁厚为2.5mm，公差能保持在尺寸的0.3%之内。表面粗糙度的有效值(均方根)能保持在2.5μm至25μm(0.1μin.至1.0μin.)之间。Sizelimitsarefrom400g(1lb)toseveraltons.Nodraftallowanceisrequired.Typicalmaterialsthatcanbecastwiththisprocessarealuminum,iron,steel,nickelalloys,copperalloys.Typesofpartsthatcanbemadeusingtheseprocessesarepumphousings,manifolds,andautobrakecomponents.重量限制从400g(1lb)到数吨。无需留拔模余量。这种工艺所用的典型材料有：铝、铁、钢、镍合金、铜合金。可以采用这些工艺制造的零件类型有泵壳、复式接头和自动刹车部件。第四单元•Introduction引言Forgingisanimportanthot-formingprocess.Itisusedinproducingcomponentsofallshapesandsizes,fromquitesmallitemstolargeunitsweighingseveraltons.锻造是一种重要的热成型工艺。它能用于生产各种形状和尺寸、从很小到重量数吨的零件。Forgingistheprocessbywhichmetalisheatedandisshapedbyplasticdeformationbysuitablyapplyingcompressiveforce.Usuallythecompressiveforceisintheformofhammerblowsusingapowerhammerorapress,asshowninFig.4.1.在锻造过程中先将金属加热，然后施加合适的压力使其塑性变形。通常压力都是以由如图4.1所示的动力锤或压力机提供的锤击形式出现。Handforgingtoolscomprisevariouslyshapedhammers.Thebaseonwhichtheworkissupportedduringforgingistheanvil.手工锻造工具包括各种不同形状的锤子。在锻造中用于支撑工件的基础是铁砧。Forthesemimechanizedforgingofsmalltomedium-sizedcomponents,forginghammerspoweredbyvariousmeansareemployed.Thefeaturecommontoallofthemisthat,likethehandforginghammer,theyutilizetheenergyofafallingweighttodevelopthepressureneededforshapingthemetal.khdaw.com对小到中等尺寸零件的半机械化锻造而言，锻锤可采用多种动力。就其一般特性而言，都象手工锻锤一样，它们均利用落重能量来产生金属成型所需的压力。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com Largercomponentsareforgedbymeansofforgingpressesoperatedbysteamorcompressedairorbyhydraulicorelectricpower.Largelyautomaticforgingmachinesareusedforthequantityproductionofengineeringparts.锻造大零件则要用到蒸汽、压缩空气、液力或电力驱动的锻压机。大型的自动化锻机用于工程零件的批量生产。Adistinctionmaybemadebetweenopen-dieforging,usuallyintheformofhammerforging,andclosed-dieforging.Inhammerforging,thecomponentisshapedbyhammerblowsaidedbyrelativelysimpletools.Thesemayincludeopendiesi.e.,diesthatdonotcompletelyenclosethemetaltobeshaped.锤锻中常用的开式模锻与闭式模锻是有区别的。在锤锻中零件通过锤击辅之以相对简单的工具成型。其中包括开式锻模，就是不完全封闭被成型金属的模具。Oneofthebasicoperationsofhammerforgingistheelongationofapieceofmetalbystretchingwithhammerblows,causingittobecomethinnerandlonger.Inhandforgingthework-pieceisusuallyturned90°aftereachblow,inordertoforgeitthoroughlyandpreventitslateralexpansion.锤锻的基本操作之一就是通过锤击使金属伸长，促成其变细变长。手工锻造时一般在每次锤击后都转过90°以充分锻打工件并防止横向膨胀。Theoppositeofelongationisupsetting,whichproducescompressiveshortening.Forexample,thediameterofabarcanbeincreasedbyheatingandhammeringaxially.与伸长相反的是镦粗，即产生压缩性缩短。例如，棒料的直径可以通过加热和轴向锤击而增大。Moreimportantisclosed-dieforging,verywidelyusedformassproductioninindustry,inwhichthemetalisshapedbypressingbetweenapairofforgingdies.Theupperdieisusuallyattachedtotheramofaforgingpressorakhdaw.comforginghammer,whilethelowerdieisstationary.更重要的是闭式模锻，在工业上广泛用于规模生产。闭式模锻中金属在一对锻模之间挤压成型。顶模通常放在锻压机的撞头或锻锤上，而底模则是固定的。Togethertheyformacloseddie.Closed-dieforgingcanproducecomponentsofgreatercomplexityandaccuracy,withabettersurfacefinishthanthemoretraditionalmethodsnotusingcloseddies.Thediesaremadeofspecialheat-resistantandwear-resistanttoolsteels.两者合在一起形成闭式锻模。闭式模锻能生产高度复杂和精确的零件，而且表面光洁度要比不用闭式锻模的更传统课后答案网方法好。闭式锻模采用特殊的耐热、耐磨工具钢制成。Apieceofhotmetalsufficienttoslightlyoverfillthedieshapeisplacedinthebottomdie,andthetopdieisforcedagainstit,sothatthemetaltakestheinternalshapeofthedie.www.hackshp.cn将一块大小足以充填模腔并能稍有溢出的加热金属放入底模，并将顶模加压合拢，这块金属便获得该模腔的形状。Closed-dieforgingisusedfortherapidproductionoflargenumbersoffairlysmallpartsandalsoforverylargecomponents.Forthelatter,e.g.,modernjet-aircraftcomponents,gianthydraulicallyoperatedpressesareused,whichcandevelopforcesof50,000tonsandmore.闭式模锻用于相当小的零件大批量快速生产，也可用于很大的零件。对后者而言，例如现代喷气飞机零件，使用能产生50,000吨以上压力的巨型液力锻压机。Onevaluablefeatureofforgingisthatitimprovesthestrengthofthemetalbyrefiningthestructureandmakingituniform;soforheavyforgings,suchasmarinepropellershafts,animmenselypowerfulhydraulicpresssqueezesthemetalwithaforcesometimesasgreatas10,000tonnes.锻造有价值的特性之一是它通过使金属组织均匀而改善强度，因此对诸如船舶螺旋桨轴之类的重型锻件，要用能达10,000吨压力的庞大而有力的液压机来挤压金属。Althoughthehydraulicforgingpressisamoreexpensivepieceofequipmentthanadrop-forge,ithasadvantagesbesidethoseofgivinggreaterstrengthandmoreuniformstructuretolargecomponents.Onaccountofthehighpressureandsqueezingaction,itoperateswithlessnoiseandvibrationthanadrop-forge.虽然这种液压锻机比落锤锻造要昂贵得多，但它除了能给予大零件较高的强度和更均匀的组织外还有其它优点。由于较高的压力和挤压作用，它比落锤锻造噪声及振动都小得多。Asingotsofsteelweighing30tonnesormoreareforgedinthisway,manualoperationisimpossibleanditisessentialthatallthemanipulationoftheingotisdonemechanically.由于这种情况下被锻钢坯重量大于30吨，人工操作是不可能的，钢坯的所有操作都必须是机械化的。Forgingrefinesthegrainstructureandimprovesphysicalpropertiesofthemetal.Withproperdesign,thegrainflowcanbeorientedinthedirectionofprincipalstressesencounteredinactualuse.铸造细化金属的晶粒组织、改善其物理性能。通过适当的设计，可以使晶粒流动方向与实际使用时的主应力方向一致。AsshowninFig.4.2,grainflowisthedirectionofthepatternthatthecrystalstakeduringplasticdeformation.Physicalkhdaw.comproperties(suchasstrength,ductilityandtoughness)aremuchbetterinaforgingthaninthebasemetal,whichhascrystalsrandomlyoriented.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 如图4.2所示，晶粒流动的方向就是在塑性变形期间结晶排列的方向。锻件的物理性能(如强度、延展性和韧性)远好于基础金属，因为基础金属的晶粒是无序排列的。Forgingsareconsistentfrompiecetopiece,withoutanyoftheporosity,voids,inclusionsandotherdefects.Thus,finishingoperationssuchasmachiningdonotexposevoids,becausetherearen’tany.Alsocoatingoperationssuchasplatingorpaintingarestraightforwardduetoagoodsurface,whichneedsverylittlepreparation.锻件各部分是连贯一致的，没有孔隙、空洞、杂质及其它缺陷。因此像机加工之类的精加工工序不会受空洞的影响，因为根本就不存在。另外由于锻件良好的表面，像电镀或油漆之类的涂装工序就很简单，几乎不需要做准备工作。Forgingsyieldpartsthathavehighstrengthtoweightratio,thusareoftenusedinthedesignofaircraftframemembers.Aforgedmetalcanresultinthefollowing:锻造生产的零件具有较高的强度重量比，所以常被用在飞机结构零件的设计中。锻造金属可以导致下列结果：•Increaselength,decreasecross-section,calleddrawingoutthemetal.•Decreaselength,increasecross-section,calledupsettingthemetal.•Changelength,changecross-section,bysqueezinginclosedimpressiondies.Thisresultsinfavorablegrainflowforstrongparts.●增加长度、减小横截面，称为延伸金属。khdaw.com●减小长度、增加横截面，称为镦粗金属。●通过用封闭锻模挤压，改变长度和横截面。这导致有利的晶粒流使零件坚固。•CommonForgingProcesses常用的锻造工艺Themetalcanbeforgedhot(aboverecrystallizationtemperatures)orcold.金属既可热锻(高于再结晶温度课后答案网)也可冷锻。OpenOOpendiependiedidieforgings/Handeforgforgings/Handforgings/Handforgings.ings/Handforgforgings.ings.Opendieforgingsorhandforgingsaremadewithrepeatedblowsinanopendie,wheretheoperatormanipulatestheworkpieceinthedie.Thefinishedproductisaroughapproximationofthedie.Thisiswhatatraditionalblacksmithdoes,andisanoldmanufacturingprocess.www.hackshp.cn开式模锻/手工锻：开式模锻或手工锻就是操作者操纵工件在开式锻模中反复击打。完成的产品是锻模的粗糙近似物。这就是传统铁匠干的活，是较古老的制造工艺。ImpressionImprImpressionImpressiondieessiondiedidieforgings/Precisioneforgforgings/Precisionforgings/Precisionforgings.ings/Precisionforgforgings.ings.Impressiondieforgingsandprecisionforgingsarefurtherrefinementsoftheblockerforgings.Thefinishedpartmorecloselyresemblesthedieimpression.压模锻/精密锻：压模锻和精密锻是雏形模锻的进一步改进。完成的零件与模膛更相似。PressPresPressPressforgings.sforgforgings.ings.Pressforgingsuseaslowsqueezingactionofapress,totransferagreatamountofcompressiveforcetotheworkpiece.Unlikeanopen-dieforgingwheremultipleblowstransferthecompressiveenergytotheoutsideoftheproduct,pressforgingtransferstheforceuniformlytothebulkofthematerial.压锻：压锻通过压力机缓慢的挤压动作将巨大的压力传递给工件。不像开式模锻那样需要多次击打把压缩能量传递到零件外表面，压锻能将力均匀地传递给材料的主体。Thisresultsinuniformmaterialpropertiesandisnecessaryforlargeweightforgings.Partsmadewiththisprocesscanbequitelargeasmuchas125kg(260lb)and3m(10feet)long.这使材料性能一致，对大重量锻件而言是十分必要的。采用此工艺生产的零件重量可达125kg(260lb)而长度可达3m(10feet)。UpsetUpseUpsetUpsetforgings.tforgforgings.ings.Upsetforgingincreasescross-sectionbycompressingthelength,thisisusedinmakingheadsonboltsandfasteners,valvesandothersimilarparts.顶锻：顶锻通过压缩长度增加横截面，用于在螺栓等紧固件、柱塞及类似零件上制造头部。RollRRollforgings.ollforgforgings.ings.Inrollforging,abarstock,roundorflatisplacedbetweendierollerswhichreducesthecross-sectionandincreasesthelengthtoformpartssuchasaxles,leafspringsetc.Thisisanessentialformofdrawforging.滚锻：在滚锻时，圆的或是扁平的棒料放在模辊之间缩小横截面增加长度制成诸如轮轴、板簧之类的零件。这是轧锻的基本形式。Swaging.SwagSwaging.ing.Swaging—atubeorrodisforcedinsideadieandthediameterisreducedasthecylindricalobjectisfed.Thediehammersthediameterandcausesthemetaltoflowinwardcausingtheouterdiameterofthetubeortherodtotaketheshapeofthedie.khdaw.com型锻：型锻—将圆管或圆棒强制压入锻模，随着圆柱形物体的被压入其直径减小。锻模锤击横断面使金属向内流动导致圆管或圆棒的外径变为锻模的形状。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com NetNetshape/Near-netshapshape/Near-netshape/Near-netshapee/Near-netshapshapeshapeforging.eforgforging.ing.Innetshapeornear-netshapeforging,forgingresultsinwastageofmaterialintheformofmaterialflashandsubsequentmachiningoperations,asshowninFig.4.3.Thiswastagecanbeashighas70%forgearblanks,andeven90%inthecaseofaircraftstructuralparts.纯型/近似纯型锻：采用纯型锻或近似纯型锻，产生材料损耗的主要形式是飞边以及随后的机加工，如图4.3所示。齿轮毛坯材料损耗为70%，而飞机结构零件的材料损耗甚至达90%。Net-shapeandnear-net-shapeprocessesminimizethewastebymakingprecisiondies,producingpartswithverylittledraftangle(lessthan1°).Thesetypesofprocessesofteneliminateorreducemachining.纯型锻和近似纯型锻工艺通过制作精密模具并生产锻模斜角很小(小于1°)的零件能使材料损耗最小化。此类工艺通常可以省去或减少机加工。Theprocessesarequiteexpensiveintermsoftoolingandthecapitalexpenditurerequired.Thus,theseprocessescanbeonlyjustifiedforcurrentprocessesthatareverywastefulwherethematerialsavingswillpayforthesignificantincreaseintoolingcosts.从模具的角度而言这些工艺是相当昂贵的，需要资金投入。因此这些工艺只有对目前很浪费的生产过程，在材料节约足以补偿模具成本的大量增加时才是合理的。•DieDesignConsideration锻模设计的考虑因素•Partingsurfaceshouldbealongasingleplaneifpossible,elsefollowingthecontourofthepart.Thepartingsurfaceshouldbethroughthecenterofthepart,notneartheupperorloweredges.khdaw.com•如果可能分模面应沿着单一平面，否则就顺着零件轮廓方向。分模面应经过零件中心，而不要靠近上下边缘。Ifthepartinglinecannotbeonasingleplane,thenitisgoodpracticetousesymmetryofthedesigntominimizethesidethrustforces.Anypointonthepartingsurfaceshouldbelessthan75°fromtheprincipalpartingplane.如果分模面不能在单一平面，利用设计的对称性来减小侧向推力不失为一种好方法。分模面上任意点与主分模面的夹角应小于75°。•Asinmostformingprocesses,useofundercutsshouldbeavoidedasthesewillmaketheremovalofthepart课后答案网difficult,ifnotimpossible.•如同大多数成型工艺，如果不是非用不可，尽量避免采用凹槽，因为凹槽会使零件难以取出。•Generousfilletsandradiusshouldbeprovidedtoaidinmaterialflowduringtheforgingprocess.Sharpcornerswww.hackshp.cnarestress-risersintheforgings,aswellasmakethediesweakinservice.•Ribsshouldnotbehighornarrow;thismakesitdifficultforthematerialtoflow.•应提供尽可能大的倒角和半径以帮助材料在锻造过程中流动。锐角会增加锻件中的应力，同时在使用时削弱锻模。•加劲肋不要过高、过窄，因为这会造成材料流动困难。•Tolerances公差•Dimensiontolerancesareusuallypositiveandareapproximately0.3%ofthedimension,roundedofftothenexthigher0.5mm(0.020in.).•尺寸公差通常为正，大约取为该尺寸的0.3%，并圆整到较大的0.5mm(0.020in.)。•Dieweartolerancesarelateraltolerances(paralleltothepartingplane)andareroughly+0.2%forcopperalloysto+0.5%foraluminumandsteel.•锻模磨损公差为侧向公差(平行于分模面)，对铜合金大约为+0.2%，对铝和钢大约为+0.5%。•Dieclosuretolerancesareinthedirectionofopeningandclosing,andrangefrom1mm(0.040in.)forsmallforgings,dieprojectionarea＜150cm2(23in.2),to6.25mm(0.25in.)forlargeforgings,dieprojectionarea＞6,500cm2(100in.2).•锻模的闭合公差处于开闭的方向上，范围从对较小锻件[其投影面积＜150cm2(23in.2)]取为1mm(0.040in.)，到较大锻件[其投影面积＞6,500cm2(100in.2)]取为6.25mm(0.25in.)。•Diematchtolerancesaretoallowforshiftintheupperdiewithrespecttothelowerdie.•锻模的配合公差是为了允许上模能根据下模替换。Aproperlubricantisnecessaryformakinggoodforgings.Thelubricantisusefulinpreventingstickingoftheworkpiecetothedie,andalsoactsasathermalinsulatortohelpreducediewear.制造良好的锻件必须有合适的滑润剂。滑润剂对防止工件粘住锻模很有用，还可以作为绝热体帮助减少锻模磨损。第五单元khdaw.com若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com Powdermetallurgy(Fig.5.1)usessinteringprocessformakingvariouspartsoutofmetalpowder.Themetalpowderiscompactedbyplacinginaclosedmetalcavity(thedie)underpressure.粉末冶金(图5.1)采用烧结工艺将金属粉末制成各种各样的零件。金属粉末放在封闭的金属腔(模具)中在压力下被压实。Thiscompactedmaterialisplacedinanovenandsinteredinacontrolledatmosphereathightemperaturesandthemetalpowderscoalesceandformasolid.ASecondpressingoperation,repressing,canbedonepriortosinteringtoimprovethecompactionandthematerialproperties.被压实的材料置于炉内烧结，在高温下炉内环境可控，金属粉末熔合形成固体。在烧结前可以进行二次挤压作业(再挤压)以改善压实状态和材料性能。Powdermetallurgyisahighlydevelopedmethodofmanufacturingreliableferrousandnonferrousparts.Madebymixingelementaloralloypowdersandcompactingthemixtureinadie,theresultantshapesarethensinteredorheatedinacontrolledatmospherefurnace.粉末冶金是一种高度发达的制造可靠铁或非铁零件的方法。通过混合元素或合金粉末并在模具中压实混合物，再烧结或在环境可控炉内加热制成最终形状。•Material材料Themajorityofthestructuralcomponentsproducedbyfixeddiepressingareiron-based.Thepowdersareelemental,pre-alloyed,orpartiallyalloyed.大多数用固定模压制的结构件都是铁基的。粉末可以是单一元素、预先合金或部分合金。khdaw.comElementalpowders,suchasironandcopper,areeasytocompresstorelativelyhighdensities,producepressedcompactswithadequatestrengthforhandlingduringsintering,butdonotproduceveryhighstrengthsinteredparts.诸如铁、铜之类的单一元素粉末较容易被压得相对密度较高、生产具备足够强度的压制物供烧结处理，但是无法制造出很高强度的烧结零件。Pre-alloyedpowdersareharder,lesscompressibleandhencerequirehigherpressingloadstoproducehighdensitycompacts.However,theyarecapableofproducinghighstrengthsinteredmaterials.预先合金粉末比较硬、不容易压实，因此需要较高的挤压力来产生高密度的压制物。然而它们能生成高强课后答案网度烧结材料。Pre-alloyingisalsousedwhentheproductionofahomogeneousmaterialfromelementalpowdersrequiresveryhightemperaturesandlongsinteringtimes.Thebestexamplesarethestainlesssteels,whosechromiumandnickelcontentswww.hackshp.cnhavetobepre-alloyedtoalloweconomicproductionbypowdermetallurgy.如果用单一元素粉末生产均匀材料需要很高温度和较长烧结时间，也可用预先合金。最好的例子是不锈钢，因含有铬和镍成分，所以粉末冶金必须用预先合金才经济。Partiallyalloyedpowdersareacompromiseapproach.Elementalpowders,e.g.ironwith2wt.%copper,aremixedtoproduceanhomogeneousblendwhichisthenpartiallysinteredtoattachthecopperparticlestotheironparticleswithoutproducingafullydiffusedpowderbutretainingthepowderform.部分合金粉末是一种折衷的方法。单一元素粉末，例如铁与2%的铜(重量百分比)混合均匀，经部分烧结后铜微粒粘附到铁微粒上而没有产生充分扩散的粉末却保留了粉末的形态。Inthiswaythecompressibilitiesoftheseparatepowdersintheblendaremaintainedandtheblendwillnotsegregateduringtransportationanduse.用这种方法混合物中单独粉末的可压缩性得以维持，在运送和使用期间结合将不会分离。Asimilartechniqueisto“glue”thesmallpercentageofalloyingelementontotheironpowder.This“glueing”techniqueissuccessfullyusedtointroducecarbonintotheblends,atechniquewhichpreventscarbonsegregationanddusting,producingso-called“clean”powders.另一种类似的技术是把小百分比的合金元素“粘合”到铁微粒上。这种“粘合”技术已成功用于将碳引入结合物，一种防止碳分离并起尘的技术，生产所谓的“清洁”粉末。•PowderConsolidation粉末合成Componentsorarticlesareproducedbyformingamassofpowderintoashape,thenconsolidatingtoforminter-particlemetallurgicalbonds.通过将大量的粉末放入模具成型为零件或物品，然后合成为内有微粒的冶金结合物。Anelevatedtemperaturediffusionprocessreferredtoassintering,sometimesassistedbyexternalpressure,accomplishesthis.Thematerialisneverfullymolten,althoughtheremightbeasmallvolumefractionofliquidpresentduringthesinteringprocess.Sinteringcanberegardedasweldingtheparticlespresentintheinitialusefulshape.khdaw.com提升温度扩散工艺被称为烧结，有时还辅之以外界的压力来达到目的。虽然在烧结过程中可能会有少量液态出现，但材料决不是全熔化。烧结可以被看作是把微粒焊接成初始的有用形状。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com Asageneralrulebothmechanicalandphysicalpropertiesimprovewithincreasingdensity.Thereforethemethodselectedforthefabricationofacomponentbypowdermetallurgywilldependonthelevelofperformancerequiredfromthepart.Manycomponentsareadequatewhenproducedat85~90%oftheoreticalfulldensitywhistothersrequirefulldensityforsatisfactoryperformance.作为普遍规律，随着密度的增加机械和物理性能均改善。因此选择何种粉末冶金方法来制作零件取决于其所需的性能级别。许多零件只需理论全密度的85~90%而其它的则需全密度才能满足要求。Somecomponents,inparticularbushtypebearingsoftenmadefromcopperanditsalloys,areproducedwithsignificantandcontrolledlevelsofporosity,theporositybeingsubsequentlyfilledwithalubricant.Fortunatelythereisawidechoiceofconsolidationtechniquesavailable.有些零件，尤其是衬套式轴承常用铜及其合金制作，控制多孔性程度的意义重大，因为这些孔随后要填充润滑剂。还好有多种合成技术可供选择。ColdUniaxialPressingElementalmetal,oranatomizedpre-alloyedpowderismixedwithalubricant,typicallylithiumstearate(0.75wt.%),andpressedatpressuresofsay,600MPa(87,000lb/in.2)inmetaldies.冷单向挤压单一元素金属，或极小颗粒的预先合金粉末与润滑剂(一般是锂硬脂酸盐，重量百分比0.75%)混合，然后在金属模具中施加压力khdaw.com[比如600MPa(87,000lb/in.2)]挤压。Coldcompactionensuresthattheas-compacted,or“green”,componentisdimensionallyveryaccurate,asitismouldedpreciselytothesizeandshapeofthedie.冷挤压能保证被压制或“未加工”的零件尺寸十分精确，因为它被精确地按模具的尺寸和形状成型。Onedisadvantageofthistechniqueisthedifferencesinpresseddensitythatcanoccurindifferentpartsofthecomponentduetoparticle/particleanddiewall/particlefrictionaleffects.Typicalas-presseddensitiesforsoftironcomponentswouldbe7.0g/cc,i.e.about90%oftheoreticaldensity.这种技术的缺点之一是由于微粒课后答案网/微粒和模壁/微粒间的摩擦效应，零件不同部位的压实密度存在差异。典型的软铁零件压制密度为7.0g/cc，即大约是理论密度的90%。Compactionpressurerisessignificantlyifhigheras-presseddensitiesarerequired,andthispracticebecomesuneconomicduetohighercostsforthelargerpressesandstrongertoolstowithstandthehigherpressures.www.hackshp.cn如果需要较高的压实密度则压实压力要显著提高，因为大型压力机成本较高并且在较高压力下模具强度要更高这样就不合算。ColdIsostaticPressingMetalpowdersarecontainedinanenclosuree.g.arubbermembraneorametalliccanthatissubjectedtoisostatic,whichisuniforminalldirections,externalpressure.Asthepressureisisostatictheas-pressedcomponentisofuniformdensity.冷均衡挤压金属粉末装入均衡受压的橡胶膜或金属罐内，其所受外压力在各个方向都是均匀的。由于压力是均衡的，所以压制零件密度是均匀的。Irregularlyshapedpowderparticlesmustbeusedtoprovideadequategreenstrengthintheas-pressedcomponent.Thiswillthenbesinteredinasuitableatmospheretoyieldtherequiredproduct.必须采用不规则形状粉末微粒为压制零件提供足够的未加工强度。然后放入合适的环境中烧结成所需产品。Normallythistechniqueisonlyusedforsemi-fabricatedproductssuchasbars,billets,sheet,androughlyshapedcomponents,allofwhichrequireconsiderablesecondaryoperationstoproducethefinal,accuratelydimensionedcomponent.通常这种技术只用于制作诸如棒料、坯段、薄板及粗糙成型零件之类的半成品，所有这些都需要大量进一步加工才能生产出最终尺寸精确的零件。Again,ateconomicalworkingpressures,productsarenotfullydenseandusuallyneedadditionalworkingsuchashotextrusion,hotrollingorforgingtofullydensitythematerial.此外使用经济工作压力的产品不是充分致密的，一般需要增加诸如热挤压、热轧或锻之类的额外工序来使材料达到全密度。SinteringSinteringistheprocesswherebypowdercompactsareheatedsothatadjacentparticlesfusetogether,thusresultinginasolidarticlewithimprovedmechanicalstrengthcomparedtothepowdercompact.khdaw.com烧结烧结就是通过把粉末压制物加热使邻近的微粒熔合在一起的工艺，它能生成比粉末压制物机械强度更好的若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 固体物。This“fusing”ofparticlesresultsinanincreaseinthedensityofthepartandhencetheprocessissometimescalleddensification.Therearesomeprocessessuchashotisostaticpressingwhichcombinethecompactionandsinteringprocessesintoasinglestep.微粒的“熔合”导致零件密度增加，因此该工艺有时被称为致密化。还有一些工艺如热均衡挤压，将压实和烧结工艺合并为单一步骤。Aftercompactionthecomponentspassthroughasinteringfurnace.Thistypicallyhastwoheatingzones,thefirstremovesthelubricant,andthesecondhighertemperaturezoneallowsdiffusionandbondingbetweenpowderparticles.零件压实后通过烧结炉。一般有两个加热区，第一个去除润滑剂，第二个温度更高的区域让粉末微粒之间扩散并结合。Arangeofatmospheres,includingvacuum,areusedtosinterdifferentmaterialsdependingontheirchemicalcompositions.Asanexample,preciseatmospherecontrolallowsiron/carbonmaterialstobeproducedwithspecificcarboncompositionsandmechanicalproperties.根据不同材料的化学成分，烧结的环境包括真空状态也各不相同。例如精确的环境控制可使铁/碳材料生成特殊碳化物和机械性能。Thedensityofthecomponentcanalsochangeduringsintering,dependingonthematerialsandthesinteringtemperature.Thesedimensionalchangescanbecontrolledbyanunderstandingandcontrolofthepressingandsinteringparameters,khdaw.com根据材料和烧结温度的不同，零件的密度在烧结过程中也会改变。因为尺寸的变化可以通过了解并调节挤压及烧结参数进行控制，andcomponentscanbeproducedwithdimensionsthatneedlittleornorectificationtomeetthedimensionaltolerances.Notethatinmanycasesallofthepowderusedispresentinthefinishedproduct,scraplosseswillonlyoccurwhensecondarymachiningoperationsarenecessary.所以零件尺寸几乎无需校正就能满足尺寸公差。可以看到在很多情况下所有使用的粉末都包含在制成品中，废料损失仅产生于需要辅助机加工时。课后答案网HotIsostaticPressingPowdersareusuallyencapsulatedinametalliccontainerbutsometimesinglass.Thecontainerisevacuated,thepowderout-gassedtoavoidcontaminationofthematerialsbyanyresidualgasduringtheconsolidationstageandsealed-www.hackshp.cnoff.热均衡挤压粉末通常封装在金属容器内有时也装在玻璃容器内。把容器抽真空，粉末抽气是为了防止材料在合成阶段和密封时被残留气体污染。Itisthenheatedandsubjectedtoisostaticpressuresufficienttoplasticallydeformboththecontainerandthepowder.再加热并施加均衡压力足以使容器和粉末都塑性变形。Therateofdensificationofthepowderdependsupontheyieldstrengthofthepowderatthetemperaturesandpressureschosen.Atmoderatetemperaturetheyieldstrengthofthepowdercanstillbehighandrequirehighpressuretoproducedensificationinaneconomictime.粉末致密率取决于该粉末在选定温度和压力下的屈服强度。中等温度下粉末的屈服强度仍然较高，因此需要较高压力使其在经济时间内致密化。Typicalvaluesmightbe1120℃and100MPaforferrousalloys.Bypressingatverymuchhighertemperatureslowerpressuresarerequiredastheyieldstrengthofthematerialislower.Usingaglassenclosureatmosphericpressure(15psi)isusedtoconsolidatebarsandlargerbillets.对铁合金典型的数值为1120℃和100MPa。由于很高温度下材料的屈服强度较低，因此只需较低压力就能挤压。采用玻璃容器时可用大气压力(15psi)合成棒料和较大坯段。Thetechniquerequiresconsiderablefinancialinvestmentasthepressurevesselhastowithstandtheinternalgaspressureandallowthepowdertobeheatedtohightemperatures.因为压力容器必须经受住内气压并允许粉末加热到较高温度，所以这种技术需要相当可观的资金投入。Aswithcoldisostaticpressingonlysemi-finishedproductsareproduced,eitherforsubsequentworkingtosmallersizes,orformachiningtofinisheddimensions.此工艺与采用冷均衡挤压一样只能生产半成品，可以通过后续加工至较小尺寸，也能用机加工到最终尺寸。HotForging(PowderForging)Coldpressedandsinteredcomponentshavethegreatadvantageofbeingclosetofinalshape(near-netshape),khdaw.combutarenotfullydense.Wheredensificationisessentialtoprovideadequatemechanicalproperties,thetechniqueofhotforging,orpowderforging,canbeused.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 热锻(粉末锻造)冷挤压和烧结零件主要优点是接近最终形状(近似纯形)，但不是充分致密的。当为了提供足够的机械性能而致密化是必须时，可以采用热锻或粉末锻造技术。Inpowderforginganas-pressedcomponentisusuallyheatedtoaforgingtemperaturesignificantlybelowtheusualsinteringtemperatureofthematerialandthenforgedinacloseddie.Thisproducesafullydensecomponentwiththeshapeoftheforgingdieandappropriatemechanicalproperties.在粉末锻造中，压制零件一般加热到远低于该材料通常烧结温度的锻造温度，然后在闭模中锻造。这能生产具有锻模形状和合适机械性能的充分致密零件。Powderforgedpartsgenerallyarenotasclosetofinalsizeorshapeascoldpressedandsinteredparts.Theseresultsfromtheallowancesmadeforthermalexpansioneffectsandtheneedfordraftanglesontheforgingtools.Further,minimalmachiningisrequiredbutwhenallthingsareconsideredthisrouteisoftenverycost-effective.粉末锻造零件通常不像冷挤压和烧结零件那样接近最终尺寸或形状。这是由于为热膨胀效应而设置允差以及在锻模上需要拔模斜角所致。此外还需少量机加工，但全面考虑这种方法通常还是很划算的。MetalInjectionMoulding(MIM)Injectionmouldingisverywidelyusedtoproducepreciselyshapedplasticcomponentsincomplexdies.Asinjectionpressuresarelowitispossibletomanufacturecomplexcomponents,evensomewithinternalscrewthreads,bytheuseofsidecoresandsplittools.金属注塑成型khdaw.com(MIM)注塑成型被很广泛地用于在复杂模具中生产形状精确的塑料零件。注塑压力较低使得制作复杂零件成为可能，通过采用侧面型芯和分离工具甚至可以带有内螺纹。Bymixingfine,typicallylessthan20μmdiameter,sphericalmetalpowderswiththermoplasticbinders,metalfilledplasticcomponentscanbeproducedwithmanyofthefeaturesavailableininjectionmouldedplastics.Afterinjectionmoulding,theplasticbindermaterialisremovedtoleaveametalskeletonwhichisthensinteredathightemperature.将细小(直径一般小于课后答案网20μm)球形金属粉末与热塑性粘合剂混合，能生产具有多数注塑成型塑料特征的金属充满塑料零件。注塑成型后，去除塑料粘合材料剩下金属骨架，然后在高温下烧结。Dimensionalcontrolcanbeexercisedontheas-sinteredcomponentastheinjecteddensityissensiblyuniformsoshrinkageonsinteringisalsouniform.www.hackshp.cn烧结零件可以实现尺寸控制，因为注塑密度明显均匀，所以烧结收缩也是均匀的。Shrinkagecanbelarge,duetoboththefineparticlesizeofthepowdersandthesubstantialproportionofpolymerbinderused.由于所用粉末细小微粒的尺寸和聚合物粘合剂的真实比例，收缩可以比较大。•Features特征•Forhightoleranceparts,asinteringpartisputbackintoadieandrepressed.Ingenerathismakesthepartmoreaccuratewithabettersurfacefinish.•对较大公差的零件，烧结后可放回模具重新挤压。一般而言这会使零件更精确同时具有更好的表面光洁度。•Aparthasmanyvoidsthatcanbeimpregnated.Onemethodistouseanoilbath.Anothermethodusesvacuumfirst,thenimpregnation.•零件有许多可供填充的空间。一种方法是采用油浴。另一种方法是先抽真空然后再充满。•Apartsurfacecanbeinfiltratedwithalowmeltingpointmetaltoincreasedensity,strength,hardness,ductilityandimpactresistance.•Plating,heattreatingandmachiningoperationscanalsobeused.•零件表面能被低熔点金属渗透以增大密度、强度、硬度、延展性和抗冲击能力。•仍然可以进行电镀、热处理和机加工作业。•Advantages优点•Goodtolerancesandsurfacefinish•Highlycomplexshapesmadequickly•Canproduceporouspartsandhardtomanufacturematerials(e.g.cementedoxides)•良好的公差和表面光洁度•高度复杂的形状能快速制作•能制作多孔零件和难以加工材料(如粘结氧化物)•Poresinthemetalcanbefilledwithothermaterials/metalskhdaw.com•Surfacescanhavehighwearresistance•Porositycanbecontrolled若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com •Lowwaste•Automationiseasy•金属中的气孔可用其它材料/金属填充•表面能具有较高的耐磨性•孔隙率可以控制•较低损耗•容易自动化•Physicalpropertiescanbecontrolled•Variationfromparttopartislow•Hardtomachinemetalscanbeusedeasily•Nomoltenmetals•物理性能可以控制•零件之间的变化较小•难以机加工的金属能被容易使用•无需熔化金属•Noneedformany/anyfinishingoperations•Permitshighvolumeproductionofcomplexshapes•Allowsnon-traditionalalloycombinationskhdaw.com•Goodcontroloffinaldensity•不需要很多/任何修整作业•允许加工复杂形状的大体积产品•允许非传统合金结合•对最终密度能很好地控制•Disadvantages缺点•Metalpowdersdeterioratequicklywhenstoredimproperly课后答案网•Fixedandsetupcostsarehigh•Partsizeislimitedbythepressandcompressionofthepowderused•如果存放不当金属粉末质量很快降低www.hackshp.cn•安装和调整的成本较高•零件尺寸受压力机和所用粉末压缩的限制•Sharpcornersandvaryingthicknesscanbehardtoproduce•Non-moldablefeaturesareimpossibletoproduce•锐角和变厚度较难加工•不适合模压的东西不可能生产第六单元Injectionmolding(Fig.6.1)isthepredominantprocessforfabricationofthermoplasticsintofinishedforms,andisincreasinglybeingusedforthermosettingplastics,fiber-filledcomposites,andelastomers.注塑成型(图6.1)是将热塑性塑料制成最终形状的主要工艺，并且越来越多地用于热硬化性塑料、纤维填充合成物和人造橡胶。Itistheprocessofchoicefortremendousvarietyofpartsranginginweightfrom5gto85kg.Itisestimatedthat25%ofallthermoplasticsareinjectionmolded.它是重量范围为5g到85kg极大一类零件可选用的工艺。估计所有热塑性塑料中有25%是采用注塑成型的。Ifnewermodifications,suchasreactioninjectionmolding,andthegreatlyincreasedrateofadoptionofplasticsassubstitutesformetalsareconsidered,itislikelythattheworldwideindustrialimportanceofinjectionmoldingwillcontinuetoincrease.如果考虑到新近的改进(例如反作用注塑成型)和采用塑料替代金属的高增长率，注塑成型在世界范围的工业重要性很可能将继续增加。Currently,probablyclosetohalfofallmajorprocessingunitsisinjectionmoldingmachines.In1988,adollarsaleofnewinjectionmoldingmachineryintheU.S.wasapproximately65%oftotalmajorpolymermachinerysalesvolume;thisincluded4,600injectionmoldingunits.当前，大概所有主要处理设备的近一半是注塑成型机。1988年，美国新的注塑成型机械销售约占全部主要聚合物机khdaw.com械销售量的65%，其中包括4,600台注塑成型设备。Themachinesandtheirproductsareubiquitousandaresynonymouswithplasticsformanypeople.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 这类机械和它们的产品普遍存在，对许多人来说与塑料是同义的。Areciprocatingscrewinjectionmoldingmachinecombinesthefunctionsofanextruderandacompressivemoldingpress.往复螺旋注射成型机把压出机和成型压力机的功能结合起来。Ittakessolidgranulesofthermoplasticresin,meltsandpressurizesthemintheextrudersection,forcesthemeltathighvelocityandpressurethroughcarefullydesignedflowchannelsintoacooledmold,thenejectsthefinishedpart(s),andautomaticallyrecycles.把热塑性塑料树脂的固体颗粒在压出部分融化并增压，迫使其高速融化并通过仔细设计的流动通道进入冷却模具，喷射成最终零件，然后自动再循环。Thismachineisadescendantoftheplungertype“stuffingmachine”patentedbytheHyattbrothersin1872tomoldcelluloid.In1878,theHyattsdevelopedthefirstmulticavitymold,butitwasnotuntil1938thatQuillery(France)patentedamachineincorporatingascrewtoplasticizetheelastomerbeingmolded.这种机械是1872年Hyatt兄弟获得专利权的融化赛璐珞的活塞型“填充机”的派生物。1878年Hyatt兄弟开发了第一个多槽模具，但直到1938年Quillery(法国)才发明了用螺旋增塑人造橡胶并使其成型的一体化机械。In1956,AnkerwerkNurembergcommercializedthemodernreciprocatingscrewinjectionmoldingmachineforthermoplastics.Today,over50machinemanufacturersarelistedinModernPlasticsEncyclopedia,offeringmachinestotheU.S.marketrangingfrom2to6,000tonsclampingcapacity.1956年，AnkerwerkNurembergkhdaw.com使用于热塑性塑料的现代往复螺旋注塑成型机商业化。今天，已有超过50家制造商列入现代塑料制品百科全书，能为美国市场提供压制能力从2到6,000吨的机械。(Amachinewitha10,000-toncapacityhasbeenbuilttomold264-gallonHDPEtrashcontainers.)Ahostofsuppliersofauxiliaryequipment,molds,instruments,andcontrolsservicethismajorsegmentofthepolymerindustry.(一台能力为10,000吨用于成型264加仑高密度聚乙烯垃圾箱的机械也已制成)。许多辅助设备、模具、仪器和控制系统供应商在为聚合物工业的这一主要部分服务。Injectionmoldingisparticularlyworthyofintensivestudybecauseitcombinesmanyareasofinterestextrusion,molddesign,rheology,sophisticatedhydraulicandelectroniccontrols,roboticaccessories,designof课后答案网complexproducts,and,ofcourse,theintegrationofmaterialsscienceandprocessengineering.注塑成型对深入研究很有价值，因为它结合了许多重要领域，如挤压、模具设计、流变学、完备的液压和电子控制、机器人配件、复杂产品的设计，当然还有材料科学与加工工程的综合。www.hackshp.cnTheobjectivesofinjectionmoldingengineersaresimpleenough:toobtainminimumcycletimewithminimumscrap,toattainspecifiedproductperformancewithassurance,tominimizeproductioncostsduetodowntimeoranyotherreasons,andtosteadilyincreaseinexpertiseandcompetitiveness.注塑成型工程师的目标很简单：在最少废料的情况下取得最小循环时间，在有保证的情况下获得指定产品性能，将由停工或其它原因产生的生产成本最小化，还有稳定地增加专门知识和竞争力。Profitmarginsforcustominjectionmoldersaresaidtobegenerallyskimpy;anestablishedwaytoimproveprofitsistobeselectedformoredemanding,highermarginjobsthatdemandthehighestlevelofefficiencyandcompetence.传统的注塑成型机利润盈余据说一般是不足的；为了更多需求及更高盈余工作需要选择一种改善利润的确定方法，它要求最高水平的效率和能力。Thistextwillconcentrateonthereciprocatingscrewmachineforthermoplastics,whichhaslargelyreplacedtheolderreciprocatingplungertypesexceptforverysmall-capacitymachines.本文将集中论述热塑性塑料用的往复螺旋机，除了小容量机械外它已在很大程度上取代了较老的往复活塞式机械。•InjectionMoldingMaterials注塑成型材料Itisnotpossibletoinjection-moldallpolymers.SomepolymerslikePTFE(Poly-tetra-fluoro-ethylene),cannotbemadetoflowfreelyenoughtomakethemsuitableforinjectionmolding.要注塑成型所有聚合物是不可能的。像聚四氟乙烯之类的聚合物就不能自由流动得足以适合注塑成型。Otherpolymers,suchasamixtureofresinandglassfiberinwovenormatform,areunsuitablebytheirphysicalnatureforuseintheprocess.Ingeneral,polymerswhicharecapableofbeingbroughttoastateoffluiditycanbeinjection-molded.其它聚合物，例如树脂和编织的或垫子形的玻璃纤维的混合物，由于它们的物理性质不适合使用此工艺。一般而言，能进入流动状态的聚合物都可以注塑成型。Thevastmajorityofinjectionmoldingisappliedtothermoplasticpolymers.Thisclassofmaterialsconsistsofkhdaw.compolymerswhichalwaysremaincapableofbeingsoftenedbyheatandofhardeningoncooling,evenafterrepeatedcycling.注塑成型的绝大多数都用于热塑性聚合物。这类材料由具有加热软化、冷却硬化甚至可重复循环能力的聚若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 合物组成。Thisisbecausethelong-chainmoleculesofthematerialalwaysremainasseparateentitiesanddonotformchemicalbondstooneanother.Ananalogycar,bemadetoablockoficethatcanbesoftened(i.e.turnedbacktoliquid),pouredintoanyshapecavity,andthencooledtobecomeasolidagain.这是由于这类材料的长链分子总是保持分离的实体并不相互形成化学连结。一辆由冰块制成的模拟汽车，可以融化(即转化为液态)，倒入任何形状的空腔，然后冷却重新变成固体。Thispropertydifferentiatesthermoplasticmaterialsfromthermosettingones.Inthelattertypeofpolymer,chemicalbondsareformedbetweentheseparatemoleculechainsduringprocessing.Inthiscasethechemicalbondingreferredtoascrosslinkingisthehardeningmechanism.这个特性将热塑性材料与热硬化性材料区分开。后者在加工过程中分离的分子链之间形成化学连结。在此情况下作为交联的化学连结是硬化机制。Ingeneral,mostofthethermoplasticmaterialsofferhighimpactstrength,corrosionresistance,andeasyprocessingwithgoodflowcharacteristicsformoldingcomplexdesigns.Thermoplasticsaregenerallydividedintotwoclasses:namelycrystallineandamorphous.一般而言，大多数热塑性材料具有较高的抗冲击强度、耐腐蚀性以及良好流动性使其容易加工而适于复杂成型设计。热塑性塑料通常分为两类：即结晶质的和非结晶质的。Crystallinepolymershaveanorderedmoleculararrangement,withasharpmeltingpoint.Duetotheorderedarrangementatmolecules,thecrystallinekhdaw.compolymersreflectmostincidentslightandgenerallyappearopaque.结晶质聚合物具有规则的分子排列及明显的熔点。由于规则的分子排列，结晶质聚合物能反射大多数特定光线并一般表现为不透明的。Theyalsoundergoahighshrinkageorreductioninvolumeduringsolidification.Crystallinepolymersusuallyaremoreresistanttoorganicsolventsandhavegoodfatigueandwear-resistantproperties.Crystallinepolymersalsogenerallyaredenserandhavebettermechanicalpropertiesthanamorphouspolymers.它们在固化过程中收缩较大或体积减少较多。结晶质聚合物通常多能抵御有机溶剂并具有良好的抗疲劳和磨损特性。结晶质聚合物通常也比非结晶质聚合物更致密并且具有更好的机械性能。课后答案网Themainexceptiontothisruleispolycarbonate,whichistheamorphouspolymerofchoiceforhighqualitytransparentmoldings,andhasexcellentmechanicalproperties.其中主要例外是聚碳酸酯，它是可选用做高质量透明注塑件的非结晶质聚合物，并具有卓越的机械性能。www.hackshp.cnThemechanicalpropertiesofthermoplastics,whilesubstantiallylowerthanthoseofmetals,canbeenhancedforsomeapplicationsthroughtheadditionofglassfiberreinforcement.Thistakestheformofshort-choppedfibers,afewmillimetersinlength,whicharerandomlymixedwiththethermoplasticresin.就本质而言，热塑性塑料的机械性能低于金属，但可以通过加入玻璃纤维强化予以增强来适应某些运用。常用几毫米长的短碎纤维随机地与热塑性树脂混合。Thefiberscanoccupyuptoonethirdofthematerialvolumetoconsiderablyimprovethematerialstrengthandstiffness.Thenegativeeffectofthisreinforcementisusuallyadecreaseinimpactstrengthandanincreaseinabrasiveness.纤维可占材料体积的三分之一以极大改善材料的强度和硬度。这种加强的负作用通常是抗冲击强度降低及磨损性增加。Thelatteralsohasaneffectonprocessingsincethelifeofthemoldcavityistypicallyreducedfromabout1,000,000partsforplainresinpartstoabout300,000forglass-filledparts.后者对加工过程也有影响，因为模具腔的寿命从典型的普通树脂零件大约1,000,000件减少到玻璃纤维填充树脂零件的约300,000件。Perhapsthemainweaknessofinjection-moldedpartsistherelativelylowservicetemperaturestowhichtheycanbesubjected.Thermoplasticcomponentscanonlyrarelybeoperatedcontinuouslyabove250℃,withanabsoluteupperservicetemperatureofabout400℃.注塑成型零件的主要缺点或许是它们能承受的工作温度相对较低。热塑性塑料零件只有很少能连续运行在250℃以上，其绝对最高工作温度约为400℃。Thetemperatureatwhichathermoplasticcanbeoperatedunderloadcanbedefinedqualitativelybytheheatdeflectiontemperature.Thisisthetemperatureatwhichasimplysupportedbeamspecimenofthematerial,withacentrallyappliedload,reachesapredefineddeflection.热塑性塑料带载运行温度可从质量上定义为热偏差温度。这是中心承载的该材料简支梁达到预定偏差的温度。Thetemperaturevalueobviouslydependsupontheconditionsofthetestandthealloweddeflectionandforthisreason,thetestvaluesareonlyreallyusefulforcomparingdifferentpolymers.khdaw.com其温度值明显取决于试验条件和允许偏差，因此对比较不同的聚合物而言只有试验数据是真正有用的。•CycleofOperation若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 作业循环Thereciprocatingscrewinjectionmoldingmachineisconsideredasconsistingoftwohalves:afixedinjectionside,andamovableclampside.往复螺旋注塑成型机被认为由两部分组成：一个固定注塑端和一个活动夹具端。Theinjectionsidecontainstheextruderthatreceivessolidresininpelletorgranularformandconvertsitintoaviscousliquidormeltthatcanbeforcedthroughtheconnectingnozzle,spine,andrunnerstothegatesthatleadintothemoldcavities.注塑端包含压出机，它接受小球或粒状的固体树脂，然后将其转化为粘性液体或称为融化，再强迫其通过连接喷嘴、中心和浇道到闸道进入模具腔。Themoldistightlyclampedagainstinjectionpressureandiscooledwellbelowthemelttemperatureofthethermoplastic.Whenthepartsinthecavitieshavecooledsufficientlythemoldhalvesareopenedatthemoldpartingplaneandthepartsejectedbyaknockoutsystemdropintoareceivingbinbelow.模具被紧紧地夹住以抵抗注塑压力，并在热塑性塑料的融化温度以下很好地冷却。当模腔内的零件充分冷却，剖分模在模具分模面处打开，推出系统将零件推出落入下面的接收容器内。Thissummarizestheoverallcycle,butleavesoutmuchvitaldetailthatisnecessaryforunderstandingtheprocess.However,withthisintroduction,itispossibletounderstandtheadvantagesanddisadvantagesoftheprocess.这概述了整个循环，但省略了许多对理解此工艺所必需的很重要细节。然而通过本介绍，了解这种工艺的优缺点仍是可能的。khdaw.com•EffectsofProcessVariablesonOrientation加工变量对方向性的影响Ininjectionmolding,anyvariationinprocessingthatkeepsthemoldingresinhotthroughoutfillingallowsincreasedrelaxationand,therefore,decreasedorientation.Someofthestepsthatcanbetakentoreduceorientationareasfollows.在注塑成型时，整个填料过程始终保持成型树脂高温的任何加工变化都会增加松弛作用而减少方向性。下面是可以用于减少方向性的若干措施。课后答案网•Fasterinjection(uptoapoint):lesscoolingduringfilling,henceathinnerinitialfrozenlayer,lowerviscosityduetoshearthinning;betterflowtocorners;andlesscrystallinityallfavorlowersubsurfaceorientation.Theprimaryeffectisthatthegatewillfreezemorequickly.Atthatpoint,orientationstopsandrelaxationstarts.www.hackshp.cn•较快注塑(到点)：在填料过程中冷却较少，因此初始固化层较薄，由于剪应变稀少而粘性较低；能较好地流到角落；结晶度较小；所有这些促成表面下的方向性也较低。主要效果是闸道将较快固化。这样使得方向性停止产生而松弛作用开始增加。•Highermeltandmoldtemperatures:lowermeltviscosity,easierfilling,andgreaterrelaxationfavorreducedorientation.•Reducedpackingtimeandpressure:overpackinginhibitsrelaxationprocesses.•较高的融化和成型温度：融化粘性较低，更容易填充，较大松弛作用促成方向性减少。•减少挤压时间和压力：过度挤压会抑制松弛过程。•Reducedgatesize:largergatestakelongertofreezeoffandpermitincreasedorientation.•减小闸道尺寸：闸道越大则固化时间越长并会使方向性增加。Excessivelyhighinjectionspeedcancausehighsurfaceorientationandincreasesusceptibilitytostresscracking.Forexample,moldingsthataretobeelectroplated,andwillbesubjecttoacidsolutionsduringplating,mustbemadeusingveryslowinjectionspeedstominimizesurfaceorientation.过高的注塑速度会引起较高的表面方向性及增加应力破裂的敏感性。例如，要电镀的注塑件在电镀时会经受酸溶液，必须采用很低的注塑速度制造以使表面方向性最小化。Ontheotherhand,thetransversemotioncomponentofthemeltfrontinmostmoldingscancausetransversesubsurfaceorientationsuperimposedontheprimaryorientation,givingadesirablebiaxialorientationeffect.另一方面，大多数注塑件的融化前部横向运动部分能导致在主要方向性上有层理的表面下横向方向性，产生需要的双轴方向性效应。Orientationcanbeseriouslyincreasedbyobstructionstoflowduringfillingofthecavity.Flowaroundanobstructioncausesadecreaseinmeltfrontspeedandleadstohighlocalviscosityandreducedrelaxation.Thisisalsolikelytooccurneartheendofthefillingphaseifgatingisinadequate.在填充模腔时流动受到阻碍会极大地增加方向性。围绕障碍物流动使融化前部的速度下降并产生较高的局部粘性而减少松弛作用。如果闸道不适当，这也很可能发生在接近填充结束阶段。khdaw.comThemoldermustrecognizethedangersofexcessivefillspeed,insufficientinjectionpressure,excessivemelttemperature,andinadequatepacking.Thesedangersareweighedagainsttheopposingeffectsonorientationdiscussed若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com above.注塑工必须认识过快填充速度、不足注塑压力、过高融化温度和不充分挤压的危害性。这些危害性要与上述方向性的反向效应相权衡。Thickerpartsdelaycoolingandincreaserelaxationtimeandtendtoresultinlowerorientation.Thickerpartsalsotendtowarpless.Therefore,aminimumwallthicknesscanbeestablishedbyexperienceforvariousshapes,materials,andprocesscombinations.较厚零件会延迟冷却并且增加松弛时间，趋向于导致较低的方向性。较厚零件也有助于减少翘曲。因此，对各种形状、材料和工艺组合能通过经验来确定最小壁厚。Lowermolecularweightandbroadermolecularweightdistributioninthermoplasticsfavorlowerorientationandreducedinternalstressinmoldings.在热塑性塑料中较小的分子量以及较宽泛的分子量分布促成方向性减少同时降低注塑件中的内应力。Theskinthicknessratioisaffectedbyprocessvariablesinthesamewayasonewouldpredictfortheorientation;thatis,itdecreasesasthemeltormoldtemperaturesandcavitypressureincreases.Tensilestrengthandstiffnessincreaseasskinthicknessratioincreases.Microscopicexaminationthusprovidesanotherwayofstudyingtheprocessefficiently.外壳厚度比受加工变量影响的方式与方向性预测一样；也就是它能随融化或成型温度及模腔压力的增加而减少。拉伸强度和硬度随外壳厚度比增加而增加。因而显微镜检查提供了有效研究该工艺的另一方法。•Advantages优点1.Highproductionrates.Forexample,aCDdiskcanbeproducedwitha10~12scycleinhighmeltflowindexPC.khdaw.com1.高生产率：例如，一张CD盘在高融体流动指数生产控制中只需10~12s一个循环就能生产出来。2.Relativelylowlaborcontent.Oneoperatorcanfrequentlytakecareoftwoormoremachines,particularlythemoldingsareunloadedautomaticallyontoconveyors.2.相对较少的工作内容：一个操作者经常可以照看两台以上机械，尤其是当成品能自动卸到输送机上时。3.Partsrequirelittleornofinishing.Forexample,flashcanbeminimizedandmoldscanbearrangedtoautomaticallyseparaterunnersandgatesfromthepartitself.4.Verycomplexshapescanbeformed.Advancesinmoldtoolingarelargelyresponsible.课后答案网3.零件几乎不需要修整：例如，飞边可以最小化并且模具能被设计成自动将浇道和闸道从零件本身分离。4.非常复杂的形状也能成型：模具的进步很大程度上是可靠的。5.Flexibilityofdesign(finishes,colors,www.hackshp.cninserts,materials).Morethanonematerialcanbemoldedthroughco-injection.Foamcorematerialswithsolidskinsareefficientlyproduced.Thermosettingplasticsandfiber-reinforcedshapesareinjectionmolded.5.设计的灵活性(光洁度、颜色、插入物、材料)：通过复合注塑可以成型多于一种材料。可以高效地生产带有固体外壳的泡沫型芯材料。热硬化性塑料和纤维加强形状都可以注塑成型。6.Minimumscraploss.Runners,gates,andscrapcanusuallybereground.Recycledthermoplasticscanbeinjectionmolded.6.废料损失最小化：浇道、闸道和废料通常可以重新研磨。循环热塑性塑料可以注塑成型。7.Closetolerancesareobtainable.Modernmicroprocessorcontrols,fittedtoprecisionmolds,andelaboratehydraulics,facilitatetolerancesinthe0.1%rangeondimensionsandweights(butnotwithoutahighlevelofoperationalskillsinconstantattendance).7.能得到接近的公差：现代微处理器控制、合适的精密模具和精心制作的液压设备使得尺寸和重量的公差保持在0.1%的范围内(但不是没有在持续照看时的高水平操作技能)。8.Makesbestuseoftheuniqueattributesofpolymers,suchasflowability,lightweight,transparency,andcorrosionresistance.Thisisevidentfromthenumberandvarietyofmoldedplasticproductsineverydayuse.8.充分利用聚合物诸如流动能力、重量轻、透明和耐腐蚀等独特属性：从日常使用成型塑料产品的数量和种类就能明显看到。•DisadvantagesandProblems缺点和问题1.Highinvestmentinequipmentandtoolsrequireshighproductionvolumes.2.Lackofexpertiseandgoodpreventivemaintenancecancausehighstartupandrunningcosts.1.较高的设备和模具投资需要较高生产量才合算。2.缺少专门技术和良好的预防性维修会导致较高的启动和运行成本。3.Qualityissometimesdifficulttodetermineimmediately.Forexample,post-moldwarpagemayrenderpartsunusablebecauseofdimensionalchangesthatarenotcompletedforweeksormonthsaftermolding.khdaw.com3.质量有时难以马上确定。例如，成型后的翘曲会导致零件不能用，因为在成型后几星期甚至几个月尺寸变化都不能完成。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 4.Attentionisrequiredonmanydetailsrequiringawidevarietyofskillsandcross-disciplinaryknowledge.5.Partdesignsometimesisnotwellsuitedtoefficientmolding.4.对许多需要广泛多样性技能和交叉学科知识的细节必须加以注意。5.零件设计有时不能很好地适应有效率的成型。6.Leadtimeformolddesign,moldmanufactureanddebuggingtrialsissometimesverylong.6.模具设计、模具制造和调试试验这些先导工作有时要花费很长时间。第七单元Theimportanceofmachiningprocessescanbeemphasisedbythefactthateveryproductweuseinourdailylifehasundergonethisprocesseitherdirectlyorindirectly.(1)InUSA,morethan$100billionsarespentannuallyonmachiningandrelatedoperations.机加工过程的重要性可通过日常生活使用的每件产品都直接或间接经历这一过程的事实来强调。(1)在美国，每年花在机加工及其相关作业上的费用都多于千亿美元。(2)Alargemajority(above80%)ofallthemachinetoolsusedinthemanufacturingindustryhaveundergonemetalcutting.(3)Anestimateshowedthatabout10to15%ofallthemetalproducedinUSAwasconvertedintochips.(2)用于制造业的全部机床中的大多数(多于80%)都经历过金属切削。(3)有估计显示美国生产的所有金属中约khdaw.com10到15%转变成了切屑。Thesefactsshowtheimportanceofmetalcuttingingeneralmanufacturing.Itisthereforeimportanttounderstandthemetalcuttingprocessinordertomakethebestuseofit.这些事实说明了金属切削在常规制造中的重要性。因此了解金属切削过程以充分利用它是重要的。Anumberofattemptshavebeenmadeinunderstandingthemetalcuttingprocessandusingthisknowledgetohelpimprovemanufacturingoperationswhichinvolvedmetalcutting.在了解金属切削过程并运用这些知识帮助改善与金属切削有关的制造作业方面已经做了许多努力。AtypicalcuttingtoolinsimplifiedformisshowninFig.7.1.Theimportantfeaturestobeobservedarefollows.课后答案网典型切削刀具的简化形式如图7.1所示。要注意的重要特征如下。1.RakeRRakeangle.akeanglangle.e.Itistheanglebetweenthefaceofthetoolcalledtherakefaceandthenormaltothemachiningdirection.Highertherakewww.hackshp.cnangle,betteristhecuttingandlessarethecuttingforces,increasingtherakeanglereducesthemetalbackupavailableatthetoolrakeface.1.前角：它是被称为前倾面的刀具面与垂直机加工方向的夹角。前角越大，则切削越好且切削力越小，增加前角可以减少刀具前倾面上产生的金属阻塞。Thisreducesthestrengthofthetooltipaswellastheheatdissipationthroughthetool.Thus,thereisamaximumlimittotherakeangleandthisisgenerallyoftheorderof15°forhighspeedsteeltoolscuttingmildsteel.Itispossibletohaverakeanglesatzeroornegative.但这会和减少通过刀具散发的热量一样减少刀尖强度。因此前角有一最大限制，用高速钢刀具切削低碳钢通常为15°。前角取零度或负值也是可能的。2.Clearanceangle.Thisistheanglebetweenthemachinedsurfaceandtheundersideofthetoolcalledtheflankface.Theclearanceangleisprovidedsuchthatthetoolwillnotrubthemachinedsurfacethusspoilingthesurfaceandincreasingthecuttingforces.Averylargeclearanceanglereducesthestrengthofthetooltip,andhencenormallyanangleoftheorderof5~6°isused.2.后角：这是机加工面与被称为后侧面的刀具底面夹角。后角使刀具不产生会损坏机加工面的摩擦和增加切削力。很大的后角会削弱刀尖的强度，因此一般采用5~6°的后角。Theconditionswhichhaveanimportantinfluenceonmetalcuttingareworkmaterial,cuttingtoolmaterial,cuttingtoolgeometry,cuttingspeed,feedrate,depthofcutandcuttingfluidused.对金属切削有重要影响的条件有工件材料、刀具材料、刀具几何形状、切削速度、进给率、切削深度和所用的切削液。Thecuttingspeed,v,isthespeedwithwhichthecuttingtoolmovesthroughtheworkmaterial.Thisisgenerallyexpressedinmetrespersecond(ms-1).切削速度v指切削刀具经过工件材料的移动速度。通常用米每秒(ms-1)表示。Feedrate,f,maybedefinedasthesmallrelativemovementpercycle(perrevolutionorperstroke)ofthecuttingtoolinadirectionusuallynormaltothecuttingspeeddirection.Depthofcut,d,isthenormaldistancebetweentheunmachinedsurfaceandthemachinedsurface.khdaw.com进给率f可定义为每循环(每转或每行程)切削刀具在通常为垂直于切削速度方向的次要相对运动。切削深度d是未加工面与已加工面之间的垂直距离。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com •ChipFormation切屑的形成Metalcuttingprocessisaverycomplexprocess.Fig.7.2showsthebasicmaterialremovaloperationschematically.金属切削过程是一个很复杂的过程。图7.2用图的形式显示了基本材料去除作业。Themetalinfrontofthetoolrakefacegetsimmediatelycompressed,firstelasticallyandthenplastically.Thiszoneistraditionallycalledshearzoneinviewoffactthatthematerialinthefinalformwouldberemovedbyshearfromtheparentmetal.在刀具前倾面前的金属直接受到压缩，首先弹性变形然后塑性变形。考虑到最终形状中的材料是通过剪切从母体金属去除的，此区域传统上称为剪切区。Theactualseparationofthemetalstartsasayieldingorfracture,dependinguponthecuttingconditions,startingfromthecuttingtooltip.Thenthedeformedmetal(calledchip)flowsoverthetool(rake)face.金属的实际分离始于屈服或断裂(视切削条件而定)，从切削刀尖开始。然后变形金属(称为切屑)流过刀具(前倾)面。Ifthefrictionbetweenthetoolrakefaceandtheundersideofthechip(deformedmaterial)isconsiderable,thenthechipgetsfurtherdeformed,whichistermedassecondarydeformation.Thechipafterslidingoverthetoolrakefaceisliftedawayfromthetool,andtheresultantcurvatureofthechipistermedaschipcurl.如果刀具前倾面与切屑(变形金属)底面之间的摩擦相当大，那么切屑进一步变形，这也叫做二次变形。滑过刀具前倾面的切屑被提升离开刀具，切屑弯曲的结果被称为切屑卷。Plasticdeformationcanbecausedbyyielding,inwhichcasestrainedlayersofmaterialwouldgetdisplacedoverotherlayersalongtheslip-planeswhichcoincidewiththedirectionofmaximumshearstress.khdaw.com屈服能导致塑性变形，在这种情况下材料变形层沿着与最大剪应力方向一致的滑移面被其它层所取代。Achipisvariablebothinsizeandshapeinactualmanufacturingpractice.Studyofchipsisoneofthemostimportantthingsinmetalcutting.Aswouldbeseenlater,themechanicsofmetalcuttingaregreatlydependentontheshapeandsizeofthechipsproduced.在实际加工过程中切屑的尺寸和形状都是变化的。对切屑的研究是金属切削最重要的事情之一。如同后面将要看到的那样，金属切削力学极大地依赖于所产生切屑的形状和尺寸。Chipformationinmetalcuttingcouldbebroadlycategorisedintothreetypes:(Fig.7.3)课后答案网(1)Discontinuouschip(2)Continuouschip(3)ContinuouschipwithBUE(Builtupedge)www.hackshp.cn金属切削中的切屑形成可以宽泛地分成三个类型(图7.3)：(1)间断切屑(2)连续切屑(3)带切屑瘤的连续切屑DiscontinuousDiscDiscontinuousDiscontinuousChip.ontinuousChipChip..Thesegmentedchipseparatesintoshortpieces,whichmayormaynotadheretoeachother.Severedistortionofthemetaloccursadjacenttotheface,resultinginacrackthatrunsaheadofthetool.间断切屑：分段的切屑分散成小碎片，既可能相互附着也可能不相互附着。在靠近切削面处发生金属的剧烈变形，导致在运动刀具前方金属层产生裂缝。Eventually,theshearstressacrossthechipbecomesequaltotheshearstrengthofthematerial,resultinginfractureandseparation.Withthistypeofchip,thereislittlerelativemovementofthechipalongthetoolface,Fig.7.3a.最后，横过切屑的剪切应力与材料的剪切强度相等，造成断裂和分离。生成这类切屑时，切屑沿刀具面几乎没有相对运动，见图7.3a。ContinuousContContinuousContinuouschip.inuouschipchip..Thecontinuouschipischaracterizedbyageneralflowoftheseparatedmetalalongthetoolface.Theremaybesomecrackingofthechip,butinthiscaseitusuallydoesnotextendfarenoughtocausefracture.连续切屑：连续的切屑一般具有分离金属沿刀具面流动的特征。切屑可能有一些破裂，但在这种情况下切屑通常不会延长到足以引起断裂。Thischipisformedatthehighercuttingspeedswhenmachiningductilematerials.Thereislittletendencyforthematerialtoadheretothetool.Thecontinuouschipusuallyshowsagoodcuttingratioandtendstoproducetheoptimumsurfacefinish,butitmaybecomeanoperatinghazard,Fig.7.3b.这种切屑形成于用较高切削速度机加工有延展性的材料时。材料几乎没有粘附刀具的倾向。连续切屑通常具有良好的切削率和趋向于产生最适宜的表面光洁度，但可能成为操作的危险之源，见图7.3b。ContinuousContContinuousContinuouswithinuouswithwwithaithaabuilt-upbuilbuilt-upbuilt-upedge.t-upedgeedge..Thischipshowstheexistenceofalocalized,highlydeformedzoneofmaterialattachedor“welded”onthetoolface.带切屑瘤的连续切屑：这种切屑显示了粘合或“焊接”在刀具面上材料局部高度变形区的存在。khdaw.comActually,analysisofphotomicrographsshowsthatthisbuilt-upedgeisheldinplacebythestaticfrictionforceuntilitbecomessolargethattheexternalforcesactingonitcauseittodislodge,withsomeofitremainingonthemachined若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com surfaceandtherestpassingoffonthebacksideofthechip,Fig.7.3c.实际上，对显微照片的分析显示这种切屑瘤受到静摩擦力抑制直至它变得大到作用在它上面的外力使其移动，一些留在机加工表面上而另一些延伸到切屑的背面，见图7.3c。•ShearZone剪切区Therearebasicallytwoschoolsofthoughtintheanalysisofthemetalremovalprocess.OneschoolofthoughtisthatthedeformationzoneisverythinandplanarasshowninFig.7.4a.TheotherschoolthinksthattheactualdeformationzoneisathickonewithafanshapeasshowninFig.7.4b.在对金属去除过程的分析中主要存在两种思想学派。一种思想学派认为变形区如图7.4a所示那样非常薄而平坦。另一学派则认为真实变形区象图7.4b所示那样为一厚的带有扇形的区域。Thoughthefirstmodel(Fig.7.4a)isconvenientfromthepointofanalysis,physicallyitisimpossibletoexist.Thisisbecauseforthetransitionfromundeformedmaterialtodeformtotakeplacealongathinplane,theaccelerationacrosstheplanehastobeinfinity.虽然第一种模型(图7.4a)从分析的角度看是方便的，但实际上是不可能存在的。这是由于未变形的材料沿着剪切面发生变形，而且越过剪切面的加速度无穷大。Similarlythestressgradientacrosstheshearplanehastobeverylargetobepractical.同样在实际运用中越过剪切面的应力梯度必须很大才行。Inthesecondmodel(Fig.7.4b)bymakingtheshearzoneoveraregion,thetransitionsinvelocitiesandshearstressescouldberealisticallyaccountedkhdaw.comfor.在第二种模型(图7.4b)中让剪力区分布于一个范围，速度和剪应力的转变能说明得更符合实际。Theanglemadebytheshearplanewiththecuttingspeedvector,Φisaveryimportantparameterinmetalcutting.Highertheshearanglebetteristhecuttingperformance.FromaviewoftheFig.7.4a,itcanbeobservedthatahigherrakeanglesgiverisetohighershearangles.由剪切面和切削速度矢量形成的角度Φ在金属切削中是一个十分重要的参数。剪切角越大，切削作业越好。从图7.4a观察，可以看到较大的前角能增大剪切角。•CuttingToolMaterials课后答案网切削刀具材料Variouscuttingtoolmaterialshavebeenusedintheindustryfordifferentapplications.Anumberofdevelopmentshaveoccurredinthecurrentcentury.www.hackshp.cn在工业中为了不同的应用可以使用各种各样的切削刀具材料。在最近的百年里产生了许多进展。Alargevarietyofcuttingtoolmaterialshasbeendevelopedtocatertothevarietyofmaterialsusedintheseprogrammes.Beforewediscussthepropertiesofthesematerials,letuslookattheimportantcharacteristicsexpectedofacuttingtoolmaterial.多种切削刀具材料被开发出来以满足这些方案中使用材料的多样性。讨论这些材料性能之前，先看一下作为切削刀具材料应具备哪些重要特性。1.Higherhardnessthanthatoftheworkpiecematerialbeingmachined,sothatitcanpenetrateintotheworkmaterial.2.Hothardness,whichistheabilityofthematerialtoretainitshardnessatelevatedtemperaturesinviewofthehightemperaturesexistinginthecuttingzone.1.硬度要比被切削工件材料高，这样它才能进入工件材料。2.热硬度，即材料由于存在于切削区的高温而升温时仍能保持其硬度的能力。3.Wearresistance—Thechip-toolandchip-workinterfacesareexposedtosuchsevereconditionsthatadhesiveandabrasionwearisverycommon.Thecuttingtoolmaterialshouldthereforehavehighabrasionresistancetoimprovetheeffectivelifeofthetool.3.耐磨性—切屑-刀具与切屑-工件的接触界面处于如此严酷的状态，粘附和磨损是很普遍的。因此切削刀具材料应具有高耐磨性以提高刀具的有效寿命。4.Toughness—Eventhoughthetoolishard,itshouldhaveenoughtoughnesstowithstandtheimpactloadsthatcomeinthebeginningofcutorforcefluctuationsduetoimperfectionsintheworkmaterial.Thisrequirementisgoingtobemoreusefulfortheinterruptedcutting,e.g.milling.4.韧性—虽然刀具是坚硬的，但也应有足够的韧性以经受住冲击载荷，这些载荷来自于切削的开始或由于工件材料的缺陷而产生的作用力波动。这个要求对如铣削之类的间断切削更有用。5.Lowfriction—Thecoefficientoffrictionbetweenthechipandtoolshouldbelow.Thiswouldallowforlowerwearratesandbetterchipflow.khdaw.com5.低摩擦系数—切屑与刀具间的摩擦系数应当较低。这会使磨损率较小及切屑流动更好。6.Thermalcharacteristics—Sincealotofheatisgeneratedatthecuttingzone,thetoolmaterialshouldhave若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com higherthermalconductivitytodissipatethisheatintheshortesttime,otherwisethetooltemperaturewouldbecomehigh,reducingitslife.6.热特性—因为大量的热产生在切削区，刀具材料应当具有较高的热传导性以在最短的时间内散发热量，否则刀具温度会升高，寿命会减少。Allthesecharacteristicsmaynotbefoundinasingletoolmaterial.Improvedtoolmaterialshavebeengivingabettercuttingperformance.所有这些特性不可能存在于单一刀具材料中。改进的刀具材料已经被赋予较好的切削性能。•SurfaceFinish表面光洁度Machiningoperationsareutilizedinviewofthebettersurfacefinishthatcouldbeachievedbyitcomparedtoothermanufacturingoperations.由于机加工能获得比其它制造作业更好的表面光洁度，所以机加工作业具有实用价值。Thusitisimportanttoknowwhatwouldbetheeffectivesurfacefinishthatcanbeachievedinamachiningoperation.Thesurfacefinishinagivenmachiningoperationisaresultoftwofactors:因而了解能在机加工作业中获得怎样的实际表面光洁度是重要的。给定机加工作业中的表面光洁度是两个因素共同作用的结果：(1)theidealsurfacefinish,whichisaresultofthegeometryofthemanufacturingprocesswhichcanbedeterminedbyconsideringthegeometryofthemachiningoperation,and(2)thenaturalcomponent,whichisaresultkhdaw.comofanumberofuncontrollablefactorsinmachining,whichisdifficulttopredict.(1)理想的表面光洁度，是通过考虑机加工作业的几何体系所决定的制造工艺几何学的结果，和(2)自然要素，即在机加工中一些难以预测的不可控因素作用的结果。IdealSurfaceFinishinTurningTheactualturningtoolusedwouldhaveanoseradiusinplaceofthesharptoolpoint,whichmodifiesthesurfacegeometryasshowninFig.7.5a.Ifthefeedrateisverysmall,asisnormalinfinishturning,thesurfaceisproducedpurelybythenoseradiusaloneasshowninFig.7.5.课后答案网车削中的理想表面光洁度实际使用的车削刀具有一个刀尖半径取代锋利刀尖，它将表面几何形状加工为如图7.5a所示。如果进给率很小，象精车中很正常的那样，工件表面则完全是由刀尖半径单独产生的，如图www.hackshp.cn7.5所示。ForthecaseinFig.7.5,thesurfaceroughnessvalueistobeR2a=8f/(18R√3)Where:RaisthesurfaceroughnessvalueRisthenoseradiusfisthefeedrate对图7.5这种情况，表面粗糙度值为R2a=8f/(18R√3)式中：Ra是表面粗糙度值R是刀尖半径f是进给率Theaboveareessentiallygeometricfactorsandthevaluesrepresentanidealsituation.Theactualsurfacefinishobtaineddependstoagreatextentuponanumberoffactorssuchas:上述基本为几何要素，其值代表了理想情况。而实际获得的表面光洁度很大程度上还取决于下列一些因素：(1)thecuttingprocessparameter,speed,feedanddepthofcut(2)thegeometryofthecuttingtool(3)applicationofcuttingfluid(4)workandtoolmaterialcharacteristics(5)rigidityofthemachinetoolandtheconsequentvibrations.(1)切削工艺参数、速度、进给和切削深度(2)切削刀具的几何形状(3)切削液的运用(4)工件和刀具的材料特性(5)机床的刚度及其伴随发生的振动Themajorinfluenceonsurfacefinishisexertedbythefeedrateandcuttingspeed.Asthefeeddecreases,fromthekhdaw.comaboveequations,wecanseethattheroughnessindexdecreases.对表面光洁度产生主要影响的是进给率和切削速度。从上述公式可以看到，随着进给的减少，粗糙度指标若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 会降低。Similarlyasthecuttingspeedincreases,wehavebettersurfacefinish.Thuswhilemakingachoiceofcuttingprocessparametersforfinish,itisdesirabletohavehighcuttingspeedandsmallfeedrates.同样随着切削速度的增大，能得到较好表面光洁度。因此在为光洁度而选择切削工艺参数时，采用较高的切削速度和较小的进给率是适当的。•CuttingFluids切削液Thefunctionsofcuttingfluids(whichareoftenerroneouslycalledcoolants)are:•Tocoolthetoolandworkpiece•Toreducethefriction切削液(经常误称为冷却液)的功能如下：•冷却刀具和工件•减少摩擦•Toprotecttheworkagainstrusting•Toimprovethesurfacefinish•Topreventtheformationofbuilt-upedge•Towashawaythechipsfromthecuttingzone•保护工件不生锈•改善表面光洁度khdaw.com•防止切屑瘤的形成•从切削区冲掉切屑However,theprimefunctionofacuttingfluidinametalcuttingoperationistocontrolthetotalheat.Thiscanbedonebydissipatingtheheatgeneratedaswellasreducingit.Themechanismsbywhichacuttingfluidperformsthesefunctionsare:coolingactionandlubricatingaction.然而，在金属切削作业中切削液的主要功能是控制总热量。这可通过既散发又减少所产生的热量来达到。切削液实现这些功能的机理是：冷却作用和润滑作用。课后答案网CoolingCoolCoolingCoolingaction.ingactiaction.on.Originallyitwasassumedthatcuttingfluidimprovesthecuttingperformancebyitscoolingpropertiesalone.Thatiswhythenamecoolantwasgiventoit.冷却作用：最初设想切削液仅仅是通过冷却特性来改善切削作业。这也是它曾被称为冷却液的原因。www.hackshp.cnSincemostofthetoolwearmechanismsarethermallyactivated,coolingthechiptoolinterfacehelpsinretainingtheoriginalpropertiesofthetoolandhenceprolongsitslife.由于大多数刀具的磨损机理都是由热引起的，冷却切屑刀具接触界面有助于保持刀具的原有特性，从而延长其使用寿命。However,areductioninthetemperatureoftheworkpiecemayundercertainconditionsincreasetheshearflowstressoftheworkpiece,therebydecreasingtoollife.Ithasbeenshownthroughanumberofinvestigationsthatcoolinginfactisoneofthemajorfactorsinimprovingthecuttingperformance.可是工件温度的降低在特定条件下会增加工件的剪切流动应力，从而降低刀具寿命。通过一些研究已经表明实际上冷却只是改善切削作业的主要因素之一。LubricatingLubrLubricatingLubricatingaction.icatingactiaction.on.Thebestimprovementincuttingperformancecanbeachievedbythelubricatingactionsincethisreducestheheatgenerated,thusreducingtheenergyinputtothemetalcuttingoperation.润滑作用：切削作业的最大改善可通过润滑作用来达到，由于它减少了热量的产生因而减少了金属切削作业的能量输入。However,ifthecuttingfluidistobeeffective,itmustreachthechiptoolinterface.Butitisnoteasytovisualizehowitisaccomplishedinthecaseofacontinuousturningwithasinglepointturningtool,speciallywhenthechip-toolcontactpressureisashighas70MPa.可是，如果要使切削液起作用就必须让它到达切屑刀具接触界面。但如何在采用单尖刀具连续车削的场合尤其是切屑-刀具接触压力高达70MPa时实现并非易事。Merchantthoughtthatminuteasperitiesexistedatthechip-toolinterfaceandthefluidwasdrawnintotheinterfacebythecapillaryactionoftheinterlockingnetworkofthesesurfaceasperities.Merchant认为：在切屑与刀具接触界面上存在微小的粗粒，切削液通过这些表面的微小粗粒组成连锁的网络的毛细管被吸入到切屑与刀具的接触界面上。第八单元khdaw.comGrindingisamanufacturingprocessthatinvolvestheremovalofmetalbyemployingarotatingabrasivewheel.Thelattersimulatesamillingcutterwithanextremelylargenumberofminiaturecuttingedges.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 磨削是通过采用旋转磨轮去除金属的制造工艺。磨轮用非常大量的微型切削刃模仿铣刀进行切削。Generally,grindingisconsideredtobeafinishingprocessthatisusuallyusedforobtaininghigh-dimensionalaccuracyandbettersurfacefinish.Grindingcanbeperformedonflat,cylindrical,oreveninternalsurfacesbyemployingspecializedmachinetools,whicharereferredtoasgrindingmachines.一般而言，磨削被认为是一种通常用于获得高尺寸精度和较好表面光洁度的精加工作业。磨削通过采用被称为磨床的特殊机床能在平面、圆柱面甚至内表面上进行。Obviously,grindingmachinesdifferinconstructionaswellascapabilities,andthetypetobeemployedisdeterminedmainlybythegeometricalshapeandnatureofthesurfacetobeground,e.g.,cylindricalsurfacesaregroundoncylindricalgrindingmachines.显然，磨床根据结构和功能的不同有所区别，使用何种形式的磨床主要取决于被磨削表面的几何形状和物理性质。例如，圆柱面在外圆磨床上磨削。•TypeofGrindingOperations磨削作业的类型1.SurfaceSurfSurfaceSurfacegrinding.acegringrinding.ding.Asthenamesurfacegrindingsuggests,thisoperationinvolvesgrindingofflatorplanesurfaces.Fig.8.1indicatesthetwopossiblevariations,eitherahorizontalorverticalmachinespindle.1.表面磨削：就像其名称暗示的那样，表面磨削和平面磨削直接有关。图8.1表示了两种可能的变化：卧式磨床主轴或立式磨床主轴。Inthefirstcase(horizontalspindle),themachineusuallyhasaplaner-typereciprocatingtableonwhichtheworkpieceiskhdaw.comheld.However,grindingmachineswithverticalspindlescanhaveeitheraplanertypetablelikethatofthehorizontal-spindlemachineorarotatingworktable.在第一种情况(卧式主轴)，卧式磨床通常具有安装工件的刨床式往复工作台。而立式主轴磨床既可以像卧式主轴磨床那样具有刨床式工作台也可以具有旋转工作台。Also,thegrindingactioninthiscaseisachievedbytheendfaceofthegrindingwheel(Fig.8.1b),contrarytothecaseofhorizontal-spindlemachines,wheretheworkpiecesgroundbytheperipheryofthegrindingwheel.而且在这种情况下，磨削动作是通过砂轮端面完成的课后答案网(图8.1b)，这与通过砂轮周边磨削工件的卧式主轴磨床正好相反。Fig.8.1aandbalsoindicatetheequationstobeusedforestimatingthedifferentparametersofthegrindingoperation,suchasthemachiningtimeandtherateofmetalremoval.www.hackshp.cn图8.1a和b同时简述了用于估计诸如加工时间和金属去除率之类的磨削作业不同参数的方程式。Duringthesurface-grindingoperations,heavyworkpiecesareeitherheldinfixturesorclampedonthemachinetablebystrapclampsandthelike,whereassmallerworkpiecesareusuallyheldbymagneticchucks.在平面磨削时，重的工件用夹具固定或用压板等夹紧在磨床工作台上，而小的工件则通常是用电磁卡盘固定的。2.CylindricalCyliCylindricalCylindricalgrinding.ndricalgringrinding.ding.Incylindricalgrinding,theworkpieceisheldbetweencentersduringthegrindingoperation,andthewheelrotationisthesourceandcausefortherotarycuttingmotion,asshowninFig.8.2.Infact,cylindricalgrindingcanbecarriedoutbyemployinganyofthefollowingmethods:2.圆柱面磨削：在圆柱面磨削中，作业时工件支撑在两顶尖之间，砂轮转动是导致回转切削运动的动力源，如图8.2所示。实际上，圆柱面磨削能通过采用下列任意方法来实现：(1)Thetransversemethod,inwhichboththegrindingwheelandtheworkpiecerotateandlongitudinallinearfeedisappliedtoenablegrindingofthewholelength.Thedepthofcutisadjustedbythecrossfeedofthegrindingwheelintotheworkpiece.(1)横向方法：这种方法中砂轮与工件均旋转且采用线性纵向进给以保证能磨削整个长度。切削深度通过改变砂轮对工件的横向进给来进行调整。(2)Theplunge-cutmethod,inwhichgrindingisachievedthroughthecrossfeedofthegrindingwheelandnoaxialfeedisapplied.Asyoucansee,thismethodcanbeappliedonlywhenthesurfacetobegroundisshorterthanthewidthofthegrindingwheelused.(2)插入-切削方法：这种方法通过砂轮的横向进给完成磨削而不采用轴向进给。正如料想的那样，这种方法只在要磨削表面比所用砂轮宽度短时才使用。(3)Thefull-depthmethod,whichissimilartothetransversemethodexceptthatthegrindingallowanceisremovedinasinglepass.Thismethodisusuallyrecommendedwhengrindingshortrigidshafts.(3)全深度方法：这种方法除了一次加工就能去除磨削余量外其它与横向方法相同。这种方法通常在磨削较短刚性轴时推荐使用。InternalInteInternalInternalgrinding.rnalgringrinding.ding.Internalgrindingisemployedforgrindingrelativelyshortholes,asshowninFig.8.3.Thekhdaw.comworkpieceisheldinachuckoraspecialfixture.Boththegrindingwheelandtheworkpiecerotateduringtheoperationandfeedisappliedinthelongitudinaldirection.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 内表面磨削：内表面磨削用于相对较短的孔，如图8.3所示。工件安装在卡盘或特殊夹具上。作业时砂轮和工件都回转并且采用纵向进给。Anydesireddepthofcutcanbeobtainedbythecrossfeedofthegrindingwheel.Avariationfromthistypeisplanetaryinternalgrinding,whichisrecommendedforheavyworkpiecesthatcannotbeheldinchucks.通过砂轮的横向进给能得到任意所需的切削深度。这种方法的一个变体是行星式内表面磨削，当工件较重不能用卡盘固定时推荐使用。Inthatcase,thegrindingwheelnotonlyspinsarounditsownaxisbutalsorotatesaroundthecenterlineoftheholethatisbeingground.在这种情况下，砂轮不但绕自身轴线回转，同时还绕被磨削孔的中心线旋转。CenterlessCentCenterlessCenterlessgrinding.erlessgringrinding.ding.Centerlessgrindinginvolvespassingacylindricalworkpiece,whichissupportedbyarestblade,betweentwowheels,i.e.,thegrindingwheelandtheregulatingorfeedwheel.无心磨削：无心磨削用于加工圆柱形工件，工件由托板支撑，在两轮即砂轮和调节或进给轮之间通过去。Thegrindingwheeldoestheactualgrinding,whiletheregulatingwheelisresponsibleforrotatingtheworkpieceaswellasgeneratingthelongitudinalfeed.Thisispossiblebecauseofthefrictionalcharacteristicsofthatwheel,whichisusuallymadeofrubber-bondedabrasive.砂轮完成实际磨削，而调节轮负责旋转工件和产生纵向进给。由于调节轮通常用橡胶粘结的磨料制成，其摩擦特性使这成为可能。AscanbeseeninFig.8.4,theaxisoftheregulatingwheelistiltedataslightanglewiththeaxisofthegrindingwheel.khdaw.comConsequently,theperipheralvelocityoftheregulatingwheelcanberesolvedintotwocomponents,namely,workpiecerotationalspeedandlongitudinalfeed.正如在图8.4中所看到的那样，调节轮的轴与砂轮轴倾斜一个微小角度。因此调节轮的圆周速度可以分解为两个分量，即工件回转速度和纵向进给。Thesecanbegivenbythefollowingequations:Vworkpiece＝Vregulatingwheel×cosαAxialfeed＝Vregulatingwheel课后答案网×c×sinαWherecisaconstantcoefficienttoaccountfortheslipbetweentheworkpieceandtheregulatingwheel(c=0.94~0.98).其值可由下列公式给出：V工件＝V调节轮×www.hackshp.cncosα轴向进给＝V调节轮×c×sinα式中c是考虑工件和调节轮之间滑动的恒定系数(c=0.94~0.98)。Thevelocityoftheregulatingwheeliscontrollableandisusedtoachieveanydesiredrotationalspeedoftheworkpiece.Theangleαisusuallytakenfrom1°to5°andthelargertheangle,thelargerthelongitudinalfeedwouldbe.调节轮的速度是可控的并被用于实现工件任意所需的转动速度。α角通常取1到5°，这角度越大则纵向进给也将越大。Whenαistakenas0°,i.e.,thetwoaxesofthegrindingandregulatingwheelsareparallel,thereisnolongitudinalfeedoftheworkpiece.当α取0°时，即砂轮和调节轮轴线平行时，则工件没有纵向进给。•GrindingWheels砂轮Grindingwheelsarecomposedofabrasivegrainshavingsimilarsizeandabinder.Theactualgrindingprocessisperformedbytheabrasivegrains.Poresbetweenthegrainswithinthebinderenablethegrainstoactasseparatesingle-pointcuttingtools.砂轮由具有相近尺寸的磨料颗粒和粘合剂组成。实际磨削作业由磨粒完成。在粘合剂中磨粒之间的孔隙使磨粒能象独立的单刃切削刀具一样工作。Theseporesalsoprovidespaceforthegeneratedchips,thuspreventingthewheelfromclogging.Inaddition,poresassisttheeasyflowofcoolantstoenableefficientandpromptremovaloftheheatgeneratedduringthegrindingprocess.这些孔隙同时还为产生的切屑提供空间以防砂轮堵塞。另外孔隙帮助冷却液容易流动，从而使在磨削作业中产生的热量能有效而迅速地散发。Grindingwheelsareidentifiedbasedontheirshapeandsize,kindofabrasive,grainsize,binder,grade(hardness),andstructure.砂轮根据它们的形状和尺寸、磨料的类型、磨粒的大小、粘合剂、等级(硬度)和结构组织来分类。ShapeShapShapeShapeandeandanandsizedsizessizeofizeofofgrindingggrindinggrindingwheels.rindingwheewheels.ls.Grindingwheelsdifferinshapeandsize,dependinguponthepurposeforwhichtheyaretobeused.VariousshapesareshowninFig.8.5andincludethefollowingtypes:khdaw.com砂轮的形状和尺寸：根据砂轮的用途，它们的形状和尺寸是不同的。各种形状如图8.5所示，其中包括：1)Straightwheelsusedforsurface,cylindrical,internal,andcenterlessgrinding.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 2)Bevelled-faceortaperedwheelsusedforgrindingthreads,gearteeth,andthelike.3)Straightrecessedwheelsforcylindricalgrindingandfacing.1)用于表面、圆柱面、内部和无心磨削的直轮。2)用于磨削螺纹、齿轮轮齿之类的斜面或锥形轮。3)用于圆柱面和端面磨削的直凹轮。4)Abrasivedisksforcutoffandslottingoperations.(thickness0.02upto0.2in.(0.5to5mm)).5)Cylinders,straightcups,andflaringcupsareusedforsurfacegrindingwiththeendfaceofthewheel.4)用于切断和开槽作业的砂轮片(其厚度从0.02到0.2英寸(0.5到5毫米))。5)用其端面进行表面磨削的圆柱、直杯及外展杯状砂轮。ThemaindimensionsofagrindingwheelaretheoutsidediameterD,theborediameterd,andtheheightH.Thesedimensionsvarywidely,dependinguponthegrindingprocessforwhichthewheelistobeused.砂轮的主要尺寸有外径D、孔径d和厚度H。根据采用砂轮的磨削工艺，这些尺寸变化很大。KindKKindofindofofabrasive.aabrasive.brasive.Grindingwheelscanbemadeofnaturalabrasivessuchasquartz,emery,andcorundumorofindustriallypreparedchemicalcompoundssuchasaluminumoxideorsiliconcarbide(knownascarborundum).磨料的类型：砂轮可以由象石英、金刚砂、刚玉之类的自然磨料制成，或者由象氧化铝或碳化硅(也称人造金刚砂)之类的工业制备的化学化合物制成。Generally,siliconcarbidegrindingwheelsareusedwhengrindinglow-tensile-strengthmaterialslikecastiron,whereasaluminumoxidewheelsareemployedforgrindinghigh-strengthmetalssuchasalloysteel,hardenedsteel,andthelike.khdaw.com当磨削象铸铁类低拉伸强度材料时，一般采用碳化硅砂轮，而磨削合金钢、淬火钢等高强度金属则要用氧化铝砂轮。GrainGraiGrainGrainsizensizessizeofizeofofabrasiveaabrasiveabrasiveused.brasiveusedused..Asyoumayexpect,thegrainsizeoftheabrasiveparticlesofthewheelplaysafundamentalroleindeterminingthequalityofgroundsurfaceobtained.所用磨粒的尺寸：正如料想的那样，砂轮磨粒的尺寸对决定所得磨削表面的质量起着根本的作用。Thefinerthegrains,thesmootherthegroundsurfaceis.Therefore,coarse-grainedgrindingwheelsareusedforroughingoperations,whereasfine-grainedwheelsareemployedinfinalfinishingoperations.磨粒越细，磨削表面越光滑。所以，粗粒砂轮用于粗加工，而细粒砂轮则用于最后精加工。课后答案网TheThThegradeegradgradegradeofeofofthetththebond.heebondbond..Thegradeofthebondisactuallyanindicationoftheresistanceofthebondtopullingofftheabrasivegrainsfromthegrindingwheel.Generally,wheelshavinghardgradesareusedforgrindingsoftmaterialsandviceversa.www.hackshp.cn粘结体的等级：粘结体的等级实际上是其抵抗将磨粒从砂轮上拉脱的指标。一般而言，具有较硬等级的砂轮用于磨削较软材料，反之亦然。Ifahard-gradewheelweretobeusedforgrindingahardmaterial,thedullgrainswouldnotbepulledofffromthebondquicklyenough,thusimpedingtheself-dressingprocessofthesurfaceofthewheelandfinallyresultingincloggingofthewheelandburnsonthegroundsurface.如果较硬等级的砂轮用于磨削较硬材料，磨钝的磨粒将不能足够快地脱离粘结体，这会妨碍砂轮表面的自修复，最终导致砂轮的堵塞并在被磨表面留下灼斑。Infact,thecuttingpropertiesofallgrindingwheelsmustberestoredperiodicallybydressingwithacementedcarbiderolleroradiamondtooltogivethewheeltheexactdesiredshapeandremoveallwornabrasivegrains.实际上，所有砂轮的磨削性能都必须定期地通过使用硬质合金滚轮或金刚石修整器修整而被恢复，以求很准确地把砂轮加工成要求的形状，并去除已磨钝的磨粒。Structure.StrStructure.ucture.Structurereferstotheamountofvoidspacebetweentheabrasivegrains.Whengrindingsoftermetals,largervoidspaceareneededtofacilitatetheflowoftheremovedchips.结构组织：结构组织与磨粒间的空隙量有关。当磨削较软金属时，需要较大的空隙以便去除切屑的流动。TheThThebinder.ebindbinder.er.Abrasiveparticlesarebondedtogetherinmanydifferentways.Theseincludebond,silicate,rubber,resinoid,shellac,andoxychloride.Nevertheless,thebondisthemostcommonlyusedone.粘合剂：磨粒可用多种不同方法粘结在一起。其中包括粘合剂、硅酸盐、橡胶、树脂、虫胶和氯氧化物。然而，粘合剂是最常用的。Infact,thestandardmarkingsystemisemployedfordistinguishinggrindingwheels,byprovidingalltheprecedingparametersinaspecificsequence.在实际生产中，为了区分砂轮采用标准标注系统，通过用一特定顺序将所有上述参数都表示出来。第九单元khdaw.com•Lapping研磨Lappingisafinishingoperationusedonflatandcylindricalsurfaces.Thelap,showninFig.9.1a,isusuallymadeof若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com castiron,copper,leather,orcloth.研磨是一种用于平面和圆柱面的精加工作业。研具，如图9.1a所示，通常用铸铁、铜、皮革或布制成。Theabrasiveparticlesareembeddedinthelap,ortheymaybecarriedthroughslurry.Dependingonthehardnessoftheworkpiece,lappingpressuresrangefrom7kPato140kPa(1to20psi).研磨微粒嵌入研具内，或者可以通过液体携带。根据工件硬度，研磨压力可在7kPa到140kPa(1到20psi)范围中取。Lappinghastwomainfunctions.Firstly,itproducesasuperiorsurfacefinishwithallmachiningmarksbeingremovedfromthesurface.Secondly,itisusedasamethodofobtainingveryclosefitsbetweenmatingpartssuchaspistonsandcylinders.研磨有两个主要作用。首先，它通过去除所有机加工痕迹能产生较好的表面光洁度。其次，它能用作获得像活塞与气缸之类配件间过盈配合的方法。Thelappedworkpiecesurfacemaylooksmoothbutitisactuallyfilledwithmicroscopicpeaks,valleys,scratchesandpits.Fewsurfacesareperfectlyflat.Lappingminimizesthesurfaceirregularities,therebyincreasingtheavailablecontactarea.研磨后的工件表面可能看似平滑，其实布满着微观峰、谷、划痕和凹陷。几乎没有表面是完全平整的。研磨使表面不规则最小化，因而增加了有效接触面积。ThedrawinginFig.9.1ashowstwosurfaces.Theupperoneishowasurfacemightlookbeforelappingandtheloweroneafterlapping.Lappingremovesthemicroscopicmountaintopsandproducesrelativelyflatplateaus.Entiremicroscopicmountainrangesmayneedtobegrounddowninordertoincreasetheavailablecontactarea.khdaw.com图9.1a上显示了两个表面。上面是研磨前表面可能的外观模样而下面则是研磨后的模样。研磨去除了微观峰顶从而产生相对平坦的平台。整个微观山脉范围都需要磨去以增加有效接触面积。ProductionlappingonflatorcylindricalpiecesisdoneonmachinessuchasthoseshowninFig.9.1band9.1c.Lappingisalsodoneoncurvedsurfaces,suchassphericalobjectsandlenses,usingspeciallyshapedlaps.研磨平面或圆柱面工件的生产过程是在如图9.1b和9.1c那样的机器上完成的。研磨也可采用特殊成型研具在诸如球形物体和透镜之类的曲面上进行。•Polishing抛光课后答案网Polishingisaprocessthatproducesasmooth,lustroussurfacefinish.Twobasicmechanismsareinvolvedinthepolishingprocess:(a)fine-scaleabrasiveremoval,and(b)softeningandsmearingofsurfacelayersbyfrictionalheatingduringpolishing.www.hackshp.cn抛光是生成平滑、有光泽表面光洁度的工艺。抛光工艺涉及两种基本机理：(a)精细等级磨粒去除，和(b)在抛光中通过摩擦生热软化并抹光表面层。ElectropolishingElectropolishingisanelectrochemicalprocesssimilarto,butthereverseof,electroplating.Theelectropolishingprocesssmoothesandstreamlinesthemicroscopicsurfaceofametalobject.Mirror-likefinishescanbeobtainedonmetalsurfacesbyelectropolishing.电解抛光电解抛光是一种与电镀相似的电化学工艺，但过程与电镀正好相反。电解抛光工艺使金属物体的微观表面平滑和简单化。通过电解抛光能在金属表面得到镜面光洁度。Inelectropolishing,themetalisremovedionbyionfromthesurfaceofthemetalobjectbeingpolished.Electrochemistryandthefundamentalprinciplesofelectrolysis(Faraday’sLaw)replacetraditionalmechanicalfinishingtechniques.在电解抛光中，金属是逐个离子地从被抛光金属物体表面去除的。电化学和电解基本原理(Faraday定理)取代了传统的机械精加工技术。Inbasicterms,theobjecttobeelectropolishedisimmersedinanelectrolyteandsubjectedtoadirectelectricalcurrent.Theobjectismaintainedanodic,withthecathodicconnectionbeingmadetoanearbymetalconductor.用基本术语说，要电解抛光的物体被浸没在电解液中并且通上直流电。该物体为阳极，阴极连接到附近的金属导体上。Smoothnessofthemetalsurfaceisoneoftheprimaryandmostadvantageouseffectsofelectropolishing.Duringtheprocess,afilmofvaryingthicknesscoversthesurfaceofthemetal.Thisfilmisthickestovermicrodepressionsandthinnestovermicroprojections.金属表面的平滑是电解抛光主要的和最有优势的效应之一。在此过程中，一变化着厚度的膜覆盖在金属表面上。该膜在微观凹陷处最厚而在微观凸出处最薄。Electricalresistanceisataminimumwhereverthefilmisthinnest,resultinginthegreatestrateofmetallicdissolution.khdaw.comElectropolishingselectivelyremovesmicroscopichighpointsor“peaks”fasterthantherateofattackonthecorrespondingmicro-depressionsor“valleys”.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 电阻在膜最薄处最小，导致最大金属分解率。电解抛光选择性地去除微观高点或“峰”快于对相应微观凹陷处或“谷”的侵蚀速率。Stockisremovedasmetallicsalt.Metalremovalundercertaincircumstancesiscontrollableandcanbeheldto0.0001to0.0025mm.原材料以金属盐的形式被去除。在特定环境下金属的去除是可控的并且保持在0.0001到0.0025mm范围内。ChemicalMechanicalPolishingChemicalmechanicalpolishingisbecominganincreasinglyimportantstepinthefabricationofmulti-levelintegratedcircuits.Chemicalmechanicalpolishingreferstopolishingbyabundantslurrythatinteractsbothchemicallyandmechanicallywiththesurfacebeingpolished.化学机械抛光化学机械抛光正在多层集成电路制造领域成为日益重要的步骤。化学机械抛光是指大量抛光液与被抛光表面产生化学和机械作用的抛光。Duringthechemicalmechanicalpolishingprocess,arotatingwaferispressedfacedownontoarotating,resilientpolishingpadwhilepolishingslurrycontainingabrasiveparticlesandchemicalreagentsflowsinbetweenthewaferandthepad.在化学机械抛光过程中，旋转晶片面向下压在旋转、有回弹力的抛光衬垫上，而同时含有研磨微粒和化学反应物的抛光液流过晶片与衬垫之间。Thecombinedactionofpolishingpad,abrasiveparticlesandchemicalreagentsresultsinmaterialremovalandpolishingofkhdaw.comthewafersurface.Chemicalmechanicalpolishingcreatesflat,damage-freeonavarietyofbrittlematerialsanditisusedextensivelyonsiliconwafersinthemanufactureofintegratedcircuits.抛光衬垫、研磨微粒和化学反应物的共同作用导致晶片表面的材料去除并抛光。化学机械抛光可使多种易碎材料平整且不受损害，因此在集成电路制造中被广泛地用在硅晶片上。Chemicalmechanicalpolishingisacomplicatedmultiphaseprocess.Itmainlyincludesthefollowingtwodynamics.First,theactivecomponentinpolishingslurryreactswiththeatomsofthewafer,andtheprocessischemicalreactionstepwithoxidation-reductivereaction.课后答案网化学机械抛光是一种复杂的多相工艺。它主要包括下列两个动态过程：第一，抛光液中活性成分与晶片的原子发生反应，这是带有氧化-还原反应的化学反应步骤。Thesecondstepistheprocessofdesorption,thatistowww.hackshp.cnsay,theresultantsgraduallyseparatefromthewafersurfaceandnewsurfaceisexposedtopolishingslurry.Ifchemicalreactiverateissmaller,thetotalremovalrateofthewaferisalsosmall;furthermore,thesurfacedegreeoffinishisnotgood.第二步是解吸附过程，即反应产物逐渐从晶片表面分离并将新表面暴露给抛光液。如果化学反应速率较小，晶片的总去除率也较小，而且表面光洁程度不够好。Onthecontrary,evenifchemicalreactionisveryrapid,butdesorptionisveryslow,thetotalremovalrateisnotgood.Becauseresultantsconnotseparatefromthewafersurface,theactivecomponentinthepolishingslurrycannotexposeandreactwiththeatomsonthenewsurface,whichholdsupchemicalreaction.与之相反，即使化学反应很快，但解吸附很慢，则总去除率也不够好。因为反应产物不能从晶片表面分离，抛光液中活性成分就不能暴露并与新表面上的原子起反应，这会抑制化学反应。Thebalanceandcompositiveeffectsoftwostepsdecidethetotalremovalrateanditssurfacedegreeoffinish.这两个步骤的平衡与合成效应决定了总去除率和表面光洁程度。第十单元Theprocessesofsurfacesurfsurfacesurfaceengineeringaceengiengineeringneering,orsurfacesurfsurfacesurfacetreatmentsacetreatreatmentstments,tailorthesurfacesofengineeringmaterialsto:(1)controlfrictionandwear,(2)improvecorrosionresistance,(3)changephysicalproperty,e.g.,conductivity,resistivity,andreflection,(4)alterdimension,(5)varyappearance,e.g.,colorandroughness,(6)reducecost.进行表面工程或表面处理的目的是：(1)控制摩擦和磨损，(2)改善抗腐蚀性，(3)改变物理性能，例如，传导率、电阻系数和反射率，(4)修改尺寸，(5)变更外观，例如颜色和粗糙程度，(6)降低成本。Commonsurfacetreatmentscanbedividedintotwomajorcategories:treatmentsthatcoverthesurfacesandtreatmentsthatalterthesurfaces.通常的表面处理可以分为两个主要类型：覆盖表面的处理和改变表面的处理。•CoveringtheSurface覆盖表面khdaw.comThetreatmentsthatcoverthesurfacesincludeorganiccoatingsandinorganiccoatings.覆盖表面的处理包括有机涂层和无机涂层。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com Theinorganiccoatingsperformelectroplatings,conversioncoatings,thermalsprayings,hotdippings,furnacefusings,orcoatthinfilms,glass,ceramicsonthesurfacesofthematerials.无机涂层有电镀、转化层、热喷涂、热浸渍、熔炉熔融、或在材料表面涂上薄膜、玻璃、陶瓷。ElectroplatingElecElectroplatingtroplatingisanelectrochemicalprocessbywhichmetalisdepositedonasubstratebypassingacurrentthroughthebath.电镀是一种在电镀槽通上电流使金属沉淀在基体上的电化学过程。Usuallythereisananode(positivelychargedelectrode),whichisthesourceofthematerialtobedeposited;theelectrochemistrywhichisthemediumthroughwhichmetalionsareexchangedandtransferredtothesubstratetobecoated;andacathode(negativelychargedelectrode)whichisthesubstratetobecoated.通常有一个阳极(正电极)，是要沉淀材料的来源；电化学反应是使金属离子交换并迁移到要覆盖基体上的中间过程；以及一个阴极(负电极)，即要覆盖的基体。Platingisdoneinaplatingbathwhichisusuallyanon-metallictank(usuallyplastic).Thetankisfilledwithelectrolytewhichhasthemetal,tobeplated,inionicform.电镀在通常为非金属容器(一般是塑料)的电镀槽中进行。该容器装满了含有离子态被镀金属的电解液。Theanodeisconnectedtothepositiveterminalofthepowersupply.Theanodeisusuallythemetaltobeplated(assumingthatthemetalwillcorrodeintheelectrolyte).Foreaseofoperation,themetalisintheformofnuggetsandplacedinaninertmetalbasketmadeoutnon-corrodingmetal(suchastitaniumorstainlesssteel).阳极与电源正极相连。阳极通常为被镀金属khdaw.com(假定该金属能在电解液中腐蚀)。为了操作容易，该金属呈固体小块形式并置于由抗腐蚀金属(如钛或不锈钢)制成的惰性金属筐内。Thecathodeistheworkpiece,thesubstratetobeplated.Thisisconnectedtothenegativeterminalofthepowersupply.Thepowersupplyiswellregulatedtominimizeripplesaswelltodeliverasteadypredictablecurrent,undervaryingloadssuchasthosefoundinplatingtanks.阴极是工件，即要镀的基体，连接到电源的负极。很好地调节电源使波动最小化并在载荷变化情况(如同电镀容器中看到的那样)下提供稳定的可预知电流。Asthecurrentisapplied,positivemetalionsfromthesolutionareattractedtothenegativelychargedcathodeand课后答案网depositonthecathode.Asareplenishmentforthesedepositedions,themetalfromtheanodeisdissolvedandgoesintothesolutionandbalancestheionicpotential.一旦通上电流，来自溶液的正的金属离子被吸引到带负电的阴极并沉淀在其上。作为这些沉淀离子的补充www.hackshp.cn，来自阳极的金属被溶解并进入溶液平衡离子势能。Thermalsprayingprocess.Thermalsprayingmetalcoatingsaredepositionsofmetalwhichhasbeenmeltedimmediatelypriortoprojectionontothesubstrate.Themetalsusedandtheapplicationsystemsusedvarybutmostapplicationsresultinthincoatingsappliedtosurfacesrequiringimprovementtotheircorrosionorabrasionresistanceproperties.热喷涂工艺：热喷涂金属涂层是金属熔化后立即投射到基体上形成的金属沉积层。所用的金属和应用系统都可以变化，但大多数应用都是在要求改善抗腐蚀或耐磨性能的表面涂上薄层。Thermalsprayisagenerictermforabroadclassofrelatedprocessesinwhichmoltendropletsofmetals,ceramics,glasses,and/orpolymersaresprayedontoasurfacetoproduceacoating,toformafree-standingnear-net-shape,ortocreateanengineeredmaterialwithuniqueproperties.热喷涂是用于很大一类相关工艺的一个通用术语，喷涂到表面产生涂层的熔化小滴可以是金属、陶瓷、玻璃和/或聚合物，形成独立的近似纯形或产生具有独特性能的设计材料。Inprinciple,anymaterialwithastablemoltenphasecanbethermallysprayed,andawiderangeofpureandcompositematerialsareroutinelysprayedforbothresearchandindustrialapplications.Depositionratesareveryhighincomparisontoalternativecoatingtechnologies.大体上，有稳定熔化状态的任何材料都可以热喷涂，范围宽阔的纯净和合成材料一般都能喷涂用于研究及工业目的。其沉积率与可供选择的涂层技术比较是很高的。Depositthicknessof0.1to1mmiscommon,andthicknessgreaterthan1cmcanbeachievedwithsomematerials.沉淀厚度普遍为0.1到1mm，对某些材料则沉淀厚度可以达到1cm以上。Theprocessforapplicationofthermalspraymetalisrelativelysimpleandconsistsofthefollowingstages.(1)Meltingthemetalatthegun.(2)Sprayingtheliquidmetalontothepreparedsubstratebymeansofcompressedair.热喷涂金属的应用工艺相对简单并由下列阶段组成：(1)在喷枪内熔化金属。khdaw.com(2)通过压缩空气将液态金属喷涂在准备好的基体上。(3)Moltenparticlesareprojectedontothecleanedsubstrate.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com Therearetwomaintypesofwireapplicationavailabletodaynamelyarcsprayandgasspray.(3)熔化微粒投射在清洁过的基体上。现在有两种主要的金属丝应用类型可选用，也就是电弧喷涂和气体喷涂。ARCARARCC—Apairofwiresareelectricallyenergizedsothatanarcisstruckacrossthetipswhenbroughttogetherthroughapistol.Compressedairisblownacrossthearctoatomiseandpropeltheautofedmetalwireparticlesontothepreparedworkpiece.电弧喷涂—当一对金属丝通过手持喷枪连到一起时，通上电横过其末端划燃电弧。压缩空气吹过电弧使其雾化并驱使自动送料金属丝微粒到准备好的工件上。GASGAGASS—Incombustionflamesprayingthecontinuouslymovingwireispassedthroughapistol,meltedbyaconicaljetofburninggas.Themoltenwiretipentersthecone,atomisesandispropelledontothesubstrate.气体喷涂—连续移动的金属丝在燃烧火焰喷射中通过手持喷枪，并被燃烧气体的锥形喷嘴所熔化。熔化后的金属丝顶端进入锥体雾化并驱使其到基体上。Thin-FilmThinThin-FilmThin-FilmCoatings.-FilmCoatCoatings.ings.PhysicalVaporDeposition(PVD)andChemicalVaporDeposition(CVD)aretwomostcommontypesofthin-filmcoatingmethods.薄膜涂层：物理蒸发沉淀(PVD)和化学蒸发沉淀(CVD)是两种最常见薄膜涂层方法的类型。PVDPVDcoatingsinvolveatom-by-atom,molecule-by-molecule,oriondepositionofvariousmaterialsonsolidsubstratesinvacuumsystems.物理蒸发沉淀khdaw.com涂层涉及到在真空装置内各种各样的材料原子紧靠原子、分子紧靠分子或离子沉淀于固态基体上。Thermalevaporationusestheatomiccloudformedbytheevaporationofthecoatingmetalinavacuumenvironmenttocoatallthesurfacesinthelineofsightbetweenthesubstrateandthetarget.Itisoftenusedinproducingthin,0.5μm,decorativeshinycoatingsonplasticparts.热蒸发利用涂层金属在真空环境中蒸发形成的微粒子雾将基体和靶材之间可见范围内所有表面覆盖。在塑料零件上生成较薄(0.5μm)的、装饰性的、有光泽的涂层时常常用到它。Thethincoating,however,isfragileandnotgoodforwearapplications.Thethermalevaporationprocesscanalso课后答案网coataverythick,1mm,layerofheat-resistantmaterials,suchasMCrAIY—ametal,chromium,aluminum,andyttriumalloys,onjetengineparts.然而，这种薄涂层是易碎的并不适合用于磨损场合。热蒸发工艺也能在喷气发动机零件上覆盖很厚www.hackshp.cn(1mm)的耐热材料涂层，例如MCrAIY—一种金属、铬、铝和钇合金。Sputteringapplieshigh-technologycoatingssuchasceramics,metalalloys,organicandinorganiccompoundsbyconnectingtheworkpieceandthesubstancetoahigh-voltageDCpowersupplyinanargonvacuumsystem.反应溅射法通过在氩真空设备中连接工件和具有特定成分的材料到高压直流电来应用诸如陶瓷、金属合金、有机和无机化合物之类的高技术涂层。Theplasmaisestablishedbetweenthesubstrate(workpiece)andthetarget(donor)andtransposesthesputteredofftargetatomstothesurfaceofthesubstrate.等离子区形成于基体(工件)和靶材(原料物质)之间并将被溅射的靶材原子转移到基体的表面上。Whenthesubstrateisnon-conductive,e.g.,polymer,aradio-frequency(RF)sputteringisusedinstead.Sputteringcanproducethin,lessthan3μm(120μin),hardthin-filmcoatings,e.g.,titaniumnitride(TIN)whichisharderthanthehardestmetal.如果基体不导电，例如聚合物，则采用射频(RF)溅射代替。反应溅射法可以生成较薄(小于3μm(120μin))的、坚硬薄膜涂层，像比最硬金属还硬的氮化钛(TIN)。Sputteringisnowwidelyappliedoncuttingtools,formingtools,injectionmoldingtools,andcommontoolssuchaspunchesanddies,toincreasewearresistanceandservicelife.现在反应溅射法已被广泛应用于切削刀具、成型工具、注射模具和诸如冲头和冲模之类的通用器具，以增强其耐磨性和使用寿命。CVDCVDiscapableofproducingthick,dense,ductile,andgoodadhesivecoatingsonmetalsandnon-metalssuchasglassandplastic.ContrastingtothePVDcoatinginthe“lineofsight”,theCVDcancoatallsurfacesofthesubstrate.化学蒸发沉淀能在金属和像玻璃和塑料之类的非金属上生成较厚的、致密的、有延伸性的和带良好粘性的涂层。与物理蒸发沉淀在“可见范围”对比，化学蒸发沉淀能将基体的所有表面都覆盖。ConventionalCVDcoatingprocessrequiresametalcompoundthatwillvolatilizeatafairlylowtemperatureanddecomposetoametalwhenitcontactswiththesubstrateathighertemperature.常规的化学蒸发沉淀涂层工艺需要一种容易在相当低温度下挥发并且在较高温度下与基体接触时能分解成khdaw.com纯金属的金属化合物。ThemostwellknownexampleofCVDisthenickelcarbonyl(NiCO4)coatingasthickas2.5mm(0.1in.)onglasswindows若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com andcontainerstomakethemexplosionorshatterresistant.最为人熟知的化学蒸发沉淀例子是在玻璃窗和容器上镀厚为2.5mm(0.1in.)的羰基镍(NiCO4)涂层使它们能抵抗爆裂或破碎。DiamondCVDcoatingprocessisintroducedtoincreasethesurfacehardnessofcuttingtools.However,theprocessisdoneatthetemperatureshigherthan700℃(1300℉)whichwillsoftenmosttoolsteel.为增加切削刀具表面硬度引入了钻石化学蒸发沉淀涂层工艺。可是此工艺要在高于700℃(1300℉)的温度下才能实现，这温度会软化大多数工具钢。Thus,theapplicationofdiamondCVDislimitedtomaterialswhichwillnotsoftenatthistemperaturesuchascementedcarbides.因而钻石化学蒸发沉淀的应用受到材料限制，要求材料在此温度下不软化例如硬质合金。Plasma-AssistedCVDcoatingprocesscanbeperformedatlowertemperaturethandiamondCVDcoatings.ThisCVDprocessisusedtoapplydiamondcoatingsorsiliconcarbidebarriercoatingsonplasticfilmsandsemiconductors,includingthestateoftheart0.25μmsemiconductors.等离子体辅助化学蒸发沉淀涂层工艺可以在比钻石化学蒸发沉淀涂层低的温度下操作。这种化学蒸发沉淀用于在塑料膜和半导体(包括人工0.25μm半导体的情况)上覆盖钻石涂层或碳化硅隔离涂层。•AlteringtheSurfaces改变表面Thetreatmentsthatalterthesurfacesincludehardeningtreatments,high-energyprocessesandspecialtreatments.khdaw.com改变表面的处理包括淬火处理、高能加工和特殊处理。High-energyprocessesarerelativelynewsurfacetreatmentmethods.Theycanalterthepropertiesofsurfaceswithoutchangingthedimensionofthesurface.Commonhigh-energyprocesses,includingelectronbeamtreatment,ionimplantation,andlaserbeamtreatment,arebrieflydiscussedasfollows:高能加工是相对较新的表面处理方法。它们能在不改变表面尺寸的情况下改变表面性能。通用的高能加工包括电子束处理、离子注入和激光束处理简要讨论如下：ElectronElecElectronElectronbeamtronbeambbeamtreatment.eamtreatreatment.课后答案网tment.Electronbeamtreatmentaltersthesurfacepropertiesbyrapidheating—usingelectronbeamandrapidcooling—intheorderof106℃/seeinaveryshallowregion,100μm,nearthesurface.Thistechniquecanalsobeusedinhardfacingtoproduce“surfacealloys”.电子束处理：电子束处理在靠近表面很浅www.hackshp.cn(100μm)的区域通过用电子束快速加热并以106℃/秒等级快速冷却来改变表面性能。这种技术也被用于表面硬化产生“表面合金”。IonIoIonimplantation.nimplimplantation.antation.Ionimplantationuseselectronbeamorplasmatoimpingegasatomstoionswithsufficientenergy,andembedtheseionsintoatomiclatticeofthesubstrate,acceleratedbymagneticcoilsinavacuumchamber.Themismatchbetweenionimplantandthesurfaceofametalcreatesatomicdefectsthathardenthesurface.离子注入：离子注入采用电子束或等离子体通过真空室内磁性线圈加速以足够的能量将气体原子撞击为离子，并把这些离子嵌入基体的原子点阵中。离子注入和金属表面之间的错配产生了硬化表面的原子瑕疵。LaserLaseLaserLaserbeamrbeambbeamtreatment.eamtreatreatment.tment.Similartoelectronbeamtreatment,laserbeamtreatmentaltersthesurfacepropertiesbyrapidheatingandrapidcoolinginaveryshallowregionnearthesurface.Itcanalsobeusedinhardfacingtoproduce“surfacealloys”.激光束处理：与电子束处理类似，激光束处理通过在靠近表面很浅的区域快速加热和快速冷却来改变表面性能。它也可以用于表面硬化产生“表面合金”。Theresultsofhigh-energyprocessesarenotwellknownorverywellcontrolled.Butthepreliminaryresultslookpromising.Furtherdevelopmentisneededinhigh-energyprocesses,especiallyinimplantdosagesandtreatmentmethods.高能加工的结果不能充分地了解或很好地控制。但初步结果看来是有前途的。高能加工需要进一步的开发，特别是注入剂量和处理方法。第十一单元•TheLatheandItsConstruction车床及其结构Alatheisamachinetoolusedprimarilyforproducingsurfacesofrevolutionandflatedges.车床是主要用于生成旋转表面和平整边缘的机床。Basedontheirpurpose,construction,numberoftoolsthatcansimultaneouslybemounted,anddegreeofautomation,lathes-or,moreaccurately,lathe-typemachinetoolscanbeclassifiedasfollows:khdaw.com根据它们的使用目的、结构、能同时被安装刀具的数量和自动化的程度，车床—或更确切地说是车床类的机床，可以被分成以下几类：若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com (1)Enginelathes(2)Toolroomlathes(3)Turretlathes(4)Verticalturningandboringmills(5)Automaticlathes(6)Special-purposelathes(1)普通车床(2)万能车床(3)转塔车床(4)立式车床(5)自动车床(6)特殊车床Inspiteofthatdiversityoflathe-typemachinetools,theyallhavecommonfeatureswithrespecttoconstructionandprincipleofoperation.Thesefeaturescanbestbeillustratedbyconsideringthecommonlyusedrepresentativetype,theenginelathe.Followingisadescriptionofeachofthemainelementsofanenginelathe,whichisshowninFig.11.1.虽然车床类的机床多种多样，但它们在结构和操作原理上具有共同特性。这些特性可以通过普通车床这一最常用的代表性类型来最好地说明。下面是关于图11.1所示普通车床的主要部分的描述。LatheLathLatheLathebed.khdaw.comebed.bbed.ed.Thelathebedisthemainframe,involvingahorizontalbeamontwoverticalsupports.Itisusuallymadeofgreyornodularcastirontodampvibrationsandismadebycasting.车床床身：车床床身是包含了在两个垂直支柱上水平横梁的主骨架。为减振它一般由灰铸铁或球墨铸铁铸造而成。Ithasguidewaystoallowthecarriagetoslideeasilylengthwise.Theheightofthelathebedshouldbeappropriatetoenablethetechniciantodohisorherjobeasilyandcomfortably.它上面有能让大拖板轻易纵向滑动的导轨。车床床身的高度应适当以让技师容易而舒适地工作。Headstock.HeadHeadstock.stock.Theheadstockisfixedatthelefthandsideofthelathebedandincludesthespindlewhoseaxisis课后答案网paralleltotheguideways(theslidesurfaceofthebed).Thespindleisdriventhroughthegearbox,whichishousedwithintheheadstock.主轴箱：主轴箱固定在车床床身的左侧，它包括轴线平行于导轨的主轴。主轴通过装在主轴箱内的齿轮箱www.hackshp.cn驱动。Thefunctionofthegearboxistoprovideanumberofdifferentspindlespeeds(usually6upto18speeds).Somemodernlatheshaveheadstockswithinfinitelyvariablespindlespeeds,whichemployfrictional,electrical,orhydraulicdrives.齿轮箱的功能是给主轴提供若干不同的速度(通常是6到18速)。有些现代车床具有采用摩擦、电力或液压驱动的无级调速主轴箱。Thespindleisalwayshollow,i.e.,ithasathroughholeextendinglengthwise.Barstockscanbefedthroughthatholeifcontinuousproductionisadopted.主轴往往是中空的，即纵向有一通孔。如果采取连续生产，棒料能通过此孔进给。Also,thatholehasataperedsurfacetoallowmountingaplainlathecenter.Theoutersurfaceofthespindleisthreadedtoallowmountingofachuck,afaceplate,orthelike.同时，此孔为锥形表面可以安装普通车床顶尖。主轴外表面是螺纹可以安装卡盘、花盘或类似的装置。Tailstock.TailTailstock.stock.Thetailstockassemblyconsistsbasicallyofthreeparts,itslowerbase,anintermediatepart,andthequill.Thelowerbaseisacastingthatcanslideonthelathebedalongtheguideways,andithasaclampingdevicetoenablelockingtheentiretailstockatanydesiredlocation,dependinguponthelengthoftheworkpiece.尾架：尾架总成基本包括三部分，底座、尾架体和套筒轴。底座是能在车床床身上沿导轨滑动的铸件，它有一定位装置能让整个尾架根据工件长度锁定在任何需要位置。Theintermediatepartisacastingthatcanbemovedtransverselytoenablealignmentoftheaxisofthetailstockwiththatoftheheadstock.Thethirdpart,thequill,isahardenedsteeltube,whichcanbemovedlongitudinallyinandoutoftheintermediatepartasrequired.尾架体为一能横向运动的铸件，它可以调整尾架轴线与主轴箱轴线成一直线。第三部分，套筒轴是一淬硬钢管，它能根据需要在尾架体中纵向进出移动。Thisisachievedthroughtheuseofahandwheelandascrew,aroundwhichanutfixedtothequillisengaged.Theholeintheopensideofthequillistaperedtoenablemountingoflathecentersorothertoolsliketwistdrillsorboringbars.Thequillcanbelockedatanypointalongitstravelpathbymeansofaclampingdevice.khdaw.com这通过使用手轮和螺杆来达到，与螺杆啮合的是一固接在套筒轴上的螺母。套筒轴开口端的孔是锥形的，能安装车床顶尖或诸如麻花钻和镗杆之类的工具。套筒轴通过定位装置能沿着它的移动路径被锁定在任何点。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com TheThecarriage.carrcarriage.iage.Themainfunctionofthecarriageismountingofthecuttingtoolsandgeneratinglongitudinaland/orcrossfeeds.ItisactuallyanH-shapedblockthatslidesonthelathebedbetweentheheadstockandtailstockwhilebeingguidedbytheV-shapedguidewaysofthebed.大拖板：大拖板的主要功能是安装刀具和产生纵向和/或横向进给。它实际上是一由车床床身V形导轨引导的、能在车床床身主轴箱和尾架之间滑动的H形滑块。Thecarriagecanbemovedeithermanuallyormechanicallybymeansoftheapronandeitherthefeedrodortheleadscrew.大拖板能手动或者通过溜板箱和光杆(进给杆)或丝杆(引导螺杆)机动。Whencuttingscrewthreads,powerisprovidedtothegearboxoftheapronbytheleadscrew.Inallotherturningoperations,itisthefeedrodthatdrivesthecarriage.Theleadscrewgoesthroughapairofhalfnuts,whicharefixedtotherearoftheapron.在切削螺旋时，动力通过丝杆提供给溜板箱上的齿轮箱。在其余车削作业中，都由光杆驱动大拖板。丝杆穿过一对固定在溜板箱后部的剖分螺母。Whenactuatingacertainlever,thehalfnutsareclampedtogetherandengagewiththerotatingleadscrewasasinglenut,whichisfed,togetherwiththecarriage,alongthebed.Whentheleverisdisengaged,thehalfnutsarereleasedandthecarriagestops.当开动特定操作杆时，剖分螺母夹在一起作为单个螺母与旋转的丝杆啮合，并带动拖板沿着床身提供进给。当操作杆脱离时，剖分螺母释放同时大拖板停止运动。khdaw.comOntheotherhand,whenthefeedrodisused,itsuppliespowertotheapronthroughawormgear.Thelatteriskeyedtothefeedrodandtravelswiththeapronalongthefeedrod,whichhasakeywayextendingtocoveritswholelength.另一方面，当使用光杆时则通过蜗轮给溜板箱提供动力。蜗轮用键连接在光杆上，并与溜板箱一起沿光杆运动，光杆全长范围开有键槽。Amodernlatheusuallyhasaquick-changegearboxlocatedundertheheadstockanddrivenfromthespindlethroughatrainofgears.Itisconnectedtoboththefeedrodandtheleadscrewandenablesselectingavarietyoffeedseasilyandrapidlybysimplyshiftingtheappropriatelevers.课后答案网现代车床一般在主轴箱下装备快速变换齿轮箱，通过一系列齿轮由主轴驱动。它与光杆和丝杆连接，能容易并快速地通过简单转换适当的操作杆选择各种进给。Thequick-changegearboxisemployedinplainturning,facingandthreadcuttingoperations.Sincethatgearboxislinkedtowww.hackshp.cnthespindle,thedistancethattheapron(andthecuttingtool)travelsforeachrevolutionofthespindlecanbecontrolledandisreferredtoasthefeed.快速变换齿轮箱可用于普通车削、端面切削和螺旋切削作业中。由于这种齿轮箱与主轴相连，主轴每转一圈溜板箱(和切削刀具)运动的距离能被控制，这距离就可以被认为是进给。•LatheCuttingTools车床切削刀具Theshapeandgeometryofthelathetoolsdependuponthepurposeforwhichtheyareemployed.车床刀具的形状和几何参数取决于它们的使用目的。Turningtoolscanbeclassifiedintotwomaingroups,namely,externalcuttingtoolsandinternalcuttingtools.Eachofthesetwogroupsincludethefollowingtypesoftools:车削刀具可以分为两个主要组别，即外部切削刀具和内部切削刀具。这两组中的每一组都包括以下类型刀具：TurningTurnTurningTurningtools.ingtootools.ls.Turningtoolscanbeeitherfinishingorroughturningtools.Roughturningtoolshavesmallnoseradiiandareemployedwhendeepcutsaremade.车削刀具：车削刀具可以是精车刀具或粗车刀具。粗车刀具刀尖半径较小，用于深切削。Ontheotherhand,finishingtoolshavelargernoseradiiandareusedforobtainingthefinalrequireddimensionswithgoodsurfacefinishbymakingslightdepthsofcut.Roughturningtoolscanberight-handorleft-handtypes,dependinguponthedirectionoffeed.Theycanhavestraight,bent,oroffsetshanks.而精车刀具刀尖半径较大，用于通过微量进刀深度来获得具有较好表面光洁度的最终所需尺寸。粗车刀具按其进给方向可以是右手型的或是左手型的。它们可以有直的、弯的或偏置的刀杆。FacingFaciFacingFacingtools.ngtooltools.s.Facingtoolsareemployedinfacingoperationsformachiningplanesideorendsurfaces.Therearetoolsformachiningleft-hand-sidesurfacesandtoolsforright-hand-sidesurfaces.Thosesidesurfacesaregeneratedthroughtheuseofthecrossfeed,contrarytoturningoperations,wheretheusuallongitudinalfeedisused.端面刀具：端面刀具用在端面作业中加工平板侧面或端部表面，也有加工左右侧表面之分。与一般采用纵向进给的车削作业相反，那些侧表面通过采用横向进给产生。khdaw.comCutoffCutoCutofffftools.tooltools.s.Cutofftools,whicharesometimescalledpartingtools,servetoseparatetheworkpieceintopartsand/ormachineexternalannulargrooves.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 切断刀具：切断刀具，有时也称为分割刀具，用于将工件分割成若干部分和/或加工外部环形槽。Thread-cuttingThreThread-cuttingThread-cuttingtools.ad-cuttingtooltools.s.Thread-cuttingtoolshaveeithertriangular,square,ortrapezoidalcuttingedges,dependinguponthecrosssectionofthedesiredthread.Also,theplaneanglesofthesetoolsmustalwaysbeidenticaltothoseofthethreadforms.螺纹切削刀具：螺纹切削刀具根据所需螺纹的横截面，有三角形的、矩形的或梯形的切削刃。同时，这些刀具的平面角必须始终与螺纹形状的平面角保持一致。Thread-cuttingtoolshavestraightshanksforexternalthreadcuttingandareofthebent-shanktypewhencuttinginternalthreads.车外螺纹的螺纹切削刀具为直刀杆，而车内螺纹的螺纹切削刀具则是弯刀杆。FormFFormtools.ormtooltools.s.Formtoolshaveedgesespeciallymanufacturedtotakeacertainform,whichisoppositetothedesiredshapeofthemachinedworkpiece.成形刀具：成形刀具有专门制成特定形状的刀刃，这种刀刃形状与被加工工件所需外形正好相反。AnHSStoolisusuallymadeintheformofasinglepiece,contrarytocementedcarbidesorceramic,whicharemadeintheformoftips.Thelatterarebrazedormechanicallyfastenedtosteelshanks．高速钢刀具通常以单件形式制造，而硬质合金或陶瓷刀具则以刀尖形式制造。后者用铜焊或机械方法固定于钢质刀杆上。Fig.11.2indicatesanarrangementofthislattertype,whichincludesthecarbidetip,thechipbreaker,thepad,theclampingscrew(withawasherandanut),andtheshank.khdaw.com图11.2所示为机械式固定布置方式，它包括了硬质合金刀尖、断屑槽、衬垫、卡装螺杆(带有垫圈和螺母)及刀杆。Asthenamesuggests,thefunctionofthechipbreakeristobreaklongchipseverynowandthen,thuspreventingtheformationofverylongtwistedribbonsthatmaycauseproblemsduringthemachiningoperation.顾名思义，断屑槽的功能就是不时地折断长切屑，以防形成很长的可能会在机加工操作中引起问题的缠绕切屑条。Thecarbidetips(orceramictips)canhavedifferentshapes,dependinguponthemachiningoperationsforwhichtheyaretobeemployed.Thetipscaneitherbesolidorwithacentralthroughhole,dependingonwhetherbrazingormechanicalclampingisemployedformountingthetipontheshank.课后答案网硬质合金刀尖(或陶瓷刀尖)根据采用它们的机加工操作，可以有不同的形状。根据将刀尖装配在刀杆上是通过用铜焊还是机械卡装，刀尖可以是实心的或是带有中心通孔的。•LatheOperationswww.hackshp.cn车床操作Inthefollowingsection,wediscussthevariousmachiningoperationsthatcanbeperformedonaconventionalenginelathe.在下面这节中，要讨论的是能在传统普通车床上进行的各种机加工作业。Itmustbeborneinmind,however,thatmoderncomputerizednumericallycontrolledlatheshavemorecapabilitiesandcandootheroperations,suchascontouring,forexample.Followingareconventionallatheoperations.然而，必须记住现代计算机数控车床具有更多的功能并且可以进行其它操作，例如仿型。下面是传统车床的操作。CylindricalCyliCylindricalCylindricalturning.ndricalturnturning.ing.Cylindricalturningisthesimplestandthemostcommonofalllatheoperations.Asinglefullturnoftheworkpiecegeneratesacirclewhosecenterfallsonthelatheaxis;thismotionisthenreproducednumeroustimesasaresultoftheaxialfeedmotionofthetool.圆柱面车削：圆柱面车削是所有车床操作中最简单也是最普通的。工件旋转一整圈产生一个圆心落在车床主轴上的圆；由于刀具的轴向进给运动这种动作重复许多次。Theresultingmachiningmarksare,therefore,ahelixhavingaverysmallpitch,whichisequaltothefeed.Consequently,themachinedsurfaceisalwayscylindrical.所以，由此产生的机加工痕迹是一条具有很小节距的螺旋线，该节距等于进给。因此机加工表面始终是圆柱形的。Theaxialfeedisprovidedbythecarriageorthecompoundrest,eithermanuallyorautomatically,whereasthedepthofcutiscontrolledbythecrossslide.轴向进给通过大拖板或复式刀架手动或自动提供，然而切削深度则由横向滑板控制。Inroughingcuts,itisrecommendedthatlargedepthsofcuts(upto0.25in.or6mm,dependingupontheworkpiecematerial)andsmallerfeedswouldbeused.Ontheotherhand,veryfinefeeds,smallerdepthsofcut(lessthan0.05in,or0.4mm),andhighcuttingspeedsarepreferredforfinishingcuts.粗车中，推荐使用较大切削深度(根据工件材料可达0.25英寸或6毫米)和较小进给。另一方面，精车则最好采用很小的进给、较小的切削深度(小于0.05英寸或0.4毫米)和较高的切削速度。Facing.FaciFacing.ng.Theresultofafacingoperationisaflatsurfacethatiseitherthewholeendsurfaceoftheworkpieceorkhdaw.comanannularintermediatesurfacelikeashoulder.Duringafacingoperation,feedisprovidedbythecrossslide,whereasthedepthofcutiscontrolledbythecarriageorcompoundrest.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 端面车削：端面车削操作的结果是将工件整个端部表面或者像轴肩之类的中间环形表面加工平整。在端面车削操作中，进给由横向滑板提供，而切削深度则通过大拖板或复式刀架控制。Facingcanbecarriedouteitherfromtheperipheryinwardorfromthecenteroftheworkpieceoutward.Itisobviousthatthemachiningmarksinbothcasestaketheformofaspiral.端面车削既可以从外表面向内切削也可以从工件中心往外切削。很明显在这两种情况下机加工痕迹都是螺线形式。Usually,itispreferredtoclampthecarriageduringafacingoperation,sincethecuttingforcetendstopushthetool(and,ofcourse,thewholecarriage)awayfromtheworkpiece.Inmostfacingoperations,theworkpieceisheldinachuckoronafaceplate.通常在端面车削作业时习惯于采用夹住大拖板，这是因为切削力倾向于将刀具(当然包括整个大拖板)推离工件。在大多数端面车削作业中，工件被支撑在卡盘或花盘上。GrooveGrooGrooveGroovecutting.vecuttcutting.ing.Incut-offandgroove-cuttingoperations,onlycrossfeedofthetoolisemployed.Thecut-offandgroovingtools,whichwerepreviouslydiscussed,areemployed.开槽：在切断和开槽操作中，刀具只有横向进给。要采用前面已经讨论过的切断和开槽刀具。BoringBoriBoringBoringandngandanandinternaldinteinternalinternalturning.rnalturnturning.ing.Boringandinternalturningareperformedontheinternalsurfacesbyaboringbarorsuitableinternalcuttingtools.Iftheinitialworkpieceissolid,adrillingoperationmustbeperformedfirst.Thedrillingtoolisheldinthetailstock,andthelatteristhenfedagainsttheworkpiece.镗孔和内部车削：镗孔和内部车削通过镗杆或合适的内部切削刀具在内表面进行。如果初始工件是实心的，则必须首先进行钻孔作业。钻孔刀具安装在尾架上，然后对着工件进给。khdaw.comTaperTapeTaperTaperturning.rturnturning.ing.Taperturningisachievedbydrivingthetoolinadirectionthatisnotparalleltothelatheaxisbutinclinedtoitwithananglethatisequaltothedesiredangleofthetaper.Followingarethedifferentmethodsusedintaper-turningpractice:锥面车削：锥面车削通过沿着与车床主轴不平行而倾斜成一个等于锥面所需角度的方向进刀来实现。下面是在实际锥面车削中采用的不同方法：(1)Rotatingthediscofthecompoundrestwithanangleequaltohalftheapexangleofthecone.Feedismanuallyprovidedbycrankingthehandleofthecompoundrest.Thismethodisrecommendedfortaperturningofexternaland课后答案网internalsurfaceswhenthetaperangleisrelativelylarge.(1)将复式刀架盘旋转一个等于圆锥体顶角一半的角度。通过摇动复式刀架操纵柄手动提供进给。当锥角相对较大时切削外锥面和内锥面推荐使用这种方法。www.hackshp.cn(2)Employingspecialformtoolsforexternal,veryshort,conicalsurfaces.Thewidthoftheworkpiecemustbeslightlysmallerthanthatofthetool,andtheworkpieceisusuallyheldinachuckorclampedonafaceplate.Inthiscase,onlythecrossfeedisusedduringthemachiningprocessandthecarriageisclampedtothemachinebed.(2)对很短的外锥面采用特殊的成型刀具。工件的宽度必须略小于刀具的宽度，并且工件通常由卡盘支撑或夹紧在花盘上。在这种情况下，机加工作业时只有横向进给而大拖板则夹紧在床身上。(3)Offsettingthetailstockcenter.Thismethodisemployedforexternaltaperturningoflongworkpiecesthatarerequiredtohavesmalltaperangles(lessthan8°).Theworkpieceismountedbetweenthetwocenters;thenthetailstockcenterisshiftedadistanceSinthedirectionnormaltothelatheaxis.(3)偏移尾架顶尖。对需要较小锥角(小于8°)的较长工件外锥面车削采用这种方法。工件安装于两顶尖之间；然后将尾架顶尖朝垂直于车床主轴方向移动一距离S。(4)Usingthetaper-turningattachment.Thismethodisusedforturningverylongworkpieces,whenthelengthislargerthanthewholestrokeofthecompoundrest.Theprocedurefollowedinsuchcasesinvolvescompletedisengagementofthecrossslidefromthecarriage,whichisthenguidedbythetaper-turningattachment.(4)采用锥面车削附加装置。这种方法用于车削很长的工件，其长度大于复式刀架的整个行程。在这种场合下要遵循的步骤是将横向滑板完全脱离大拖板，然后通过锥面车削附加装置进行引导。Duringthisprocess,theautomaticaxialfeedcanbeusedasusual.Thismethodisrecommendedforverylongworkpieceswithasmallconeangle,i.e.,8°through10°.在此作业中，能照常使用自动轴向进给。对具有较小锥角(即8°到10°)的很长工件推荐采用这种方法。ThreadThreThreadThreadcutting.adcuttcutting.ing.Whenperformingthreadcutting,theaxialfeedmustbekeptataconstantrate,whichisdependentupontherotationalspeed(rpm)oftheworkpiece.Therelationshipbetweenbothisdeterminedprimarilybythedesiredpitchofthethreadtobecut.螺纹切削：在螺纹切削作业时，轴向进给必须保持恒定速率，这取决于工件的转速(rpm)。两者之间的关系基本上由被切削螺纹所需的节距决定。Aspreviouslymentioned,theaxialfeedisautomaticallygeneratedwhencuttingathreadbymeansoftheleadkhdaw.comscrew,whichdrivesthecarriage.Whentheleadscrewrotatesasinglerevolution,thecarriagetravelsadistanceequaltothepitchoftheleadscrew.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 如前所述，当依靠驱动大拖板的丝杆切削螺纹时轴向进给是自动产生的。丝杆旋转一圈，大拖板就行进等于丝杆节距的一段距离。Consequently,iftherotationalspeedoftheleadscrewisequaltothatofthespindle(i.e.,thatoftheworkpiece),thepitchoftheresultingcutthreadisexactlyequaltothatoftheleadscrew.因此如果丝杆的旋转速度等于心轴的转速(即工件的转速)，生成切削螺纹的节距就正好等于丝杆的节距。Thepitchoftheresultingthreadbeingcutthereforealwaysdependsupontheratiooftherotationalspeedsoftheleadscrewandthespindle:Pitchoftheleadscrew/Desiredpitchofworkpiece=rpmoftheworkpiece/rpmofleadscrew=spindle-to-carriagegearingratio.所以被切削生成螺纹的节距总是取决于丝杆和心轴的转速比：丝杆的节距/工件所需节距=工件转速/丝杆转速=心轴到大拖板的传动比。Thisequationisusefulindeterminingthekinematiclinkagebetweenthelathespindleandtheleadscrewandenablesproperselectionofthegeartrainbetweenthem.这公式在决定车床心轴和丝杆之间的运动学关系时很有用，并且提供了正确挑选它们之间轮系的方法。Inthreadcuttingoperations,theworkpiececaneitherbeheldinthechuckormountedbetweenthetwolathecentersforrelativelylongworkpieces.Theformofthetoolusedmustexactlycoincidewiththeprofileofthethreadtobecut,i.e.,triangulartoolsmustbeusedfortriangularthreads,andsoon.在螺纹切削作业中，工件既能支撑于卡盘中，对相对较长的工件也能安装在两个车床顶尖之间。使用的刀具外形必须正好与要切削螺纹的轮廓一致，即三角形刀具必须用于三角形螺纹等等。khdaw.comKnurling.KnurKnurling.ling.Knurlingismainlyaformingoperationinwhichnochipsareproduced.Itinvolvespressingtwohardenedrollswithroughfilelikesurfacesagainsttherotatingworkpiecetocauseplasticdeformationoftheworkpiecemetal.滚花：滚花主要是一种不产生切屑的成型操作。它使用两个带有粗锉式表面的淬火滚轮压在旋转的工件上使工件金属产生塑性变形。Knurlingiscarriedouttoproducerough,cylindrical(orconical)surfaces,whichareusuallyusedashandles.Sometimes,surfacesareknurledjustforthesakeofdecoration;therearedifferenttypesofpatternsofknurlsfromwhich课后答案网tochoose.滚花用于生成粗糙的圆柱(或圆锥)面，通常用来作手柄。有时表面滚花只为装饰之故；有不同的滚花图案类型可供选择。www.hackshp.cn•CuttingSpeedsandFeed切削速度和进给Thecuttingspeed,whichisusuallygiveninsurfacefeetperminute(SFM),isthenumberoffeettraveledinthecircumferentialdirectionbyagivenpointonthesurface(beingcut)oftheworkpiecein1minute.切削速度，通常用每分钟表面英尺给出，就是一分钟内工件(被切削)表面给定点在圆周方向上行进的英尺数。Therelationshipbetweenthesurfacespeedandrpmcanbegivenbythefollowingequation:SFM=πDNWhereD=thediameteroftheworkpieceinfeetN=therpm表面速度与转速之间的关系可以用下式给出：SFM=πDN式中D=用英尺表示的工件直径N=转速Thesurfacecuttingspeedisdependantprimarilyuponthematerialbeingmachinedaswellasthematerialofthecuttingtoolandcanbeobtainedfromhandbooks,informationprovidedbycuttingtoolmanufacturers,andthelike.表面切削速度主要由被切削材料和切削刀具材料决定，可以从手册、切削刀具生产商提供的资料及类似的东西上查取。Generally,theSFMistakenas100whenmachiningcold-rolledormildsteel,as50whenmachiningtoughermetals,andas200whenmachiningsoftermaterials.Foraluminum,theSFMisusuallytakenas400orabove.Therearealsoothervariablesthataffecttheoptimalvalueofthesurfacecuttingspeed.一般而言，SFM当机加工冷轧或低碳钢时取100，机加工较坚韧的金属时取50，而机加工较软材料时取200。对铝而言，SFM通常可取400以上。也还存在其它一些变量影响表面切削速度的最佳值。Theseincludethetoolgeometry,thetypeoflubricantorcoolant,thefeed,andthedepthofcut.Assoonasthecuttingkhdaw.comspeedisdecidedupon,therotationalspeed(rpm)ofthespindlecanbeobtainedasfollows:N=SFM/(πD)若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 其中包括刀具形状、润滑剂或冷却液的类型、进给和切削深度。切削速度一旦确定，心轴转速(rpm)就能按下式得到：N=SFM/(πD)Theselectionofasuitablefeeddependsuponmanyfactors,suchastherequiredsurfacefinish,thedepthofcut,andthegeometryofthetoolused.Finerfeedsproducebettersurfacefinish,whereashigherfeedsreducethemachiningtimeduringwhichthetoolisindirectcontactwiththeworkpiece.合适进给的选择取决于许多因素，例如所需表面光洁度、切削深度和所用刀具的几何形状。进给越小生成的光洁度越好，而在刀具与工件直接接触时进给越大则可以减少机加工时间。Therefore,itisgenerallyrecommendedtousehighfeedsforroughingoperationsandfinerfeedsforfinishingoperations.Again,recommendedvaluesforfeeds,whichcanbetakenasguidelines,arefoundinhandbooksandininformationbookletsprovidedbycuttingtoolmanufacturers.所以对粗车一般推荐使用较大进给，而精车则用较小进给。再者，作为指导方针的进给推荐值可以从手册和切削刀具生产商提供的资料小册子上找到。第十二单元•DrillingandDrills钻削和钻头Drillinginvolvesproducingthroughorblindholesinaworkpiecebyforcingatool,whichrotatesarounditsaxis,khdaw.comagainsttheworkpiece.钻削就是通过迫使绕自身轴线旋转的切削刀具进入工件而在其上生成通孔或盲孔。Consequently,therangeofcuttingfromthataxisofrotationisequaltotheradiusoftherequiredhole.Inpractice,twosymmetricalcuttingedgesthatrotateaboutthesameaxisareemployed.因此，从旋转轴线开始的切削范围等于所需孔的半径。实际上，使用的是两条围绕相同轴线旋转的对称切削刃。Drillingoperationscanbecarriedoutbyusingeitherhanddrillsordrillingmachines.Thelatterdifferinsizeandconstruction.Nevertheless,thetoolalwaysrotatesarounditsaxiswhiletheworkpieceiskeptfirmlyfixed.Thisiscontrary课后答案网todrillingonalathe.钻削作业既能采用手钻也能采用钻床来实现。钻床在尺寸和结构上虽有差别，然而始终都是切削刀具围绕自身轴线旋转、工件稳固定位的形式。这正好与在车床上钻孔相反。www.hackshp.cnCuttingToolforDrillingOperationIndrillingoperations,acylindricalrotary-endcuttingtool,calledadrill,isemployed.Thedrillcanhaveeitheroneormorecuttingedgesandcorrespondingflutes,whichcanbestraightorhelical.用于钻削作业的切削刀具在钻削作业中，要用到被称为钻头的圆柱形回转端切削刀具。钻头可以有一条或多条直的或是螺旋状的切削刃以及相应的出屑槽。Thefunctionoftheflutesistoprovideoutletpassagesforthechipsgeneratedduringthedrillingoperationandalsotoallowlubricantsandcoolantstoreachthecuttingedgesandthesurfacebeingmachined.Followingisasurveyofthecommonlyuseddrills.出屑槽的功能是给钻削作业中产生的切屑提供排出通道，并允许润滑剂和冷却液到达切削刃和正在被加工的表面。下面是常用钻头的概述。TwistTwisTwistTwistdrill.tdrildrill.l.Thetwistdrillisthemostcommontypeofdrill.Ithastwocuttingedgesandtwohelicalflutesthatcontinueoverthelengthofthedrillbody,asshowninFig.12.1.Thedrillalsoconsistsofaneckandashankthatcanbeeitherstraightortapered.麻花钻：麻花钻是最常用的钻头类型。它有两条切削刃和两条沿钻头体全长连续的螺旋状出屑槽，如图12.1所示。麻花钻还包括钻颈和钻柄，钻柄可以是直的也可以是锥形的。Inthelattercase,theshankisfittedbythewedgeactionintothetaperedsocketofthespindleandhasatang,whichgoesintoaslotinthespindlesocket,thusactingasasolidmeansfortransmittingrotation.锥形钻柄通过楔入动作安装在主轴的锥形轴孔中，钻柄上还有柄舌插入主轴轴孔中的插槽，从而作为传递转动的可靠方法。Ontheotherhand,straight-shankdrillsareheldinadrillchuckthatis,inturn,fittedintothespindlesocketinthesamewayastaperedshankdrills.另一方面，直柄钻头用钻头卡盘夹住，接下来钻头卡盘则象锥形钻柄钻头一样安装在主轴轴孔内。AscanbeseeninFig.12.1,thetwocuttingedgesarereferredtoasthelips,andareconnectedtogetherbyakhdaw.comwedge,whichisachisel-likeedge.Thetwistdrillalsohastwomargins,whichenableproperguidanceandlocatingofthedrillwhileitisinoperation.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 如图12.1所示，两条切削刃就是钻唇，通过凿子状边缘的楔形体连在一起。麻花钻还有两条导向边，用于作业中钻头的正确导向和定位。Thetoolpointangle(TPA)isformedbythetwolipsandischosenbasedonthepropertiesofthematerialtobecut.TheusualTPAforcommercialdrillsis118°,whichisappropriatefordrillinglow-carbonsteelsandcastirons.两条钻唇形成钻顶角，并根据被钻削材料的性能来选取其大小。商品化钻头的钻顶角一般为118°，这适用于钻削低碳钢和铸铁。Forharderandtoughermetals,suchashardenedsteel,brassandbronze,largerTPAs(130°or140°)givebetterperformance.Thehelixangleoftheflutesofthecommonlyusedtwistdrillsrangesbetween24°and30°.Whendrillingcopperorsoftplastics,highervaluesforthehelixanglearerecommended(between35°and45°).对于更硬更韧的金属，诸如淬火钢、黄铜和青铜，更大的钻顶角(130°或140°)才能有更好的效果。麻花钻常用的出屑槽螺旋角范围为24°到30°。钻削紫铜或软塑料时，推荐采用更大的螺旋角(35°到45°)。Twistdrillsareusuallymadeofhigh-speedsteel,althoughcarbide-tippeddrillsarealsoavailable.Thesizesoftwistdrillsusedinindustrialpracticerangefrom0.01upto3.25in.(i.e.,0.25upto80mm).虽然也有硬质合金刀尖的钻头，麻花钻一般用高速钢制成。工业实际中使用的麻花钻尺寸范围为0.01到3.25英寸(即0.25到80毫米)。CoreCCoredrills.oredrildrills.ls.Acoredrillconsistsofthechamfer,body,neck,andshank,asshowninFig.12.2.Thistypeofdrillmayhaveeitherthreeorfourflutesandequalnumberofmargins,whichensuresuperiorguidance,thusresultinginhighmachiningaccuracy.khdaw.com空心钻：空心钻包括斜面、钻头体、钻颈和钻柄，如图12.2所示。这类钻头可以有三条或四条出屑槽及相同数量的保证良好导向的导向边，这样使得加工有高精度。ItcanalsobeseeninFig.12.2thatacoredrillhasflatend.Thechamfercanhavethreeorfourcuttingedgesorlips,andthelipanglemayvarybetween90°and120°.在图12.2中同样能看到，空心钻具有平坦的端部。斜面可以有三或四条切削刃或钻唇，并且钻唇角可以在90°到120°之间变化。Coredrillsareemployedforenlargingpreviouslymadeholesandnotfororiginatingholes.Thistypeofdrillischaracterized课后答案网bygreaterproductivity,highmachiningaccuracy,andsuperiorqualityofthedrilledsurfaces.空心钻用于扩大已有的孔而不是打孔。这类钻头具有较大生产率、高加工精度和优良钻削表面质量的特性。GunGuGundrills.ndrildrills.ls.Gundrillsareusedfordrillingdeepholes.Allgundrillsarestraight-fluted,andeachhasasinglecuttingwww.hackshp.cnedge.Aholeinthebodyactsasaconduittotransmitcoolantunderconsiderablepressuretothetipofthedrill.深孔钻：深孔钻用于钻深孔。所有深孔钻都是直出屑槽的，并且均为单切削刃。钻头体中有个孔作为导管在相当大的压力下将冷却液传送到钻头顶端。Therearetwokindsofgundrills,namely,thecenter-cutgundrillusedfordrillingblindholesandthetrepanningdrill.Thelatterhasacylindricalgrooveatitscenter,thusgeneratingasolidcore,whichguidesthetoolasitproceedsduringthedrillingoperation.深孔钻有两种类型，即用于钻盲孔的中心切削深孔钻和套孔钻。后者在其中心有一圆柱形沟槽，这样能生成整体芯在钻孔作业过程中引导钻头。SpadeSpadSpadeSpadedrills.edrildrills.ls.Spadedrillsareusedfordrillinglargeholesof3.5in.(90mm)ormore.Theirdesignresultsinamarkedsavingincostofthetoolaswellasatangiblereductioninitsweight,whichfacilitatesitshandling.Moreover,thistypeofdrilliseasytogrind.扁平钻：扁平钻用于钻削3.5英寸(90毫米)或更大的大孔。其设计使得钻头成本明显节省、重量切实减轻，重量轻又使操作更方便。此外这种钻头容易磨利。•MillingandMillingCutter铣削和铣刀Millingisamachiningprocessthatiscarriedoutbymeansofamultiedgerotatingtoolknownasamillingcutter.铣削是采用被称为铣刀的多刃旋转刀具完成的机加工作业。Inthisprocess,metalremovalisachievedthroughcombiningtherotarymotionofthemillingcutterandlinearmotionsoftheworkpiecesimultaneously.Millingoperationsareemployedinproducingflat,contouredandhelicalsurfacesaswellasforthread-andgear-cuttingoperation.在此工艺中，金属去除是通过铣刀的旋转运动和工件的直线运动的组合实现的。铣削作业既可用于生成平面、轮廓面和螺旋面，也可用于切削螺纹和齿轮。Eachofthecuttingedgesofamillingcutteractsasanindividualsingle-pointcutterwhenitengageswiththeworkpiecemetal.Therefore,eachofthosecuttingedgeshasappropriaterakeandreliefangles.khdaw.com在铣刀切削工件金属时，铣刀的每条切削刃都象一单独的单刃刀具一样作用。所以每条切削刃都适当的前后角。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com Sinceonlyafewofthecuttingedgesareengagedwiththeworkpieceatatime,heavycutscanbetakenwithoutadverselyaffectingthetoollife.Infact,thepermissiblecuttingspeedsandfeedsformillingarethreetofourtimeshigherthanthoseforturningordrilling.由于同一时间只有部分切削刃切削工件，因此可以在对刀具寿命没有不利影响的情况下承担重型切削。事实上，铣削允许的切削速度和进给比车削或钻削高三到四倍。Moreover,thequalityofthesurfacesmachinedbymillingisgenerallysuperiortothequalityofsurfacesmachinedbyturning,shaping,ordrilling.此外，由铣削加工的表面质量通常优于车削、刨削或钻削加工的表面质量。Awidevarietyofmillingcuttersisavailableinindustry.This,togetherwiththefactthatamillingmachineisaveryversatilemachinetool,makesthemillingmachinethebackboneofamachiningworkshop.工业上可采用的铣刀类型众多。连同铣床是极通用机床的事实，使得铣床成为机加工车间的支柱。Asfarasthedirectionofcutterrotationandworkpiecefeedareconcerned,millingisperformedbyeitherofthefollowingtwomethods.至于涉及到铣刀转动的方向和工件的进给，铣削可以通过下列两种方法之一进行。UpUpmillingmmillingilling(conventionalmilling).Inupmillingtheworkpieceisfedagainstthedirectionofcutterrotation,asshowninFig.12.3a.Aswecanseeinthatfigure,thedepthofcut(andconsequentlytheload)graduallyincreasesonthesuccessivelyengagedcuttingedges.逆铣(khdaw.com传统铣削)：在逆铣中，工件逆着铣刀转动的方向进给，如图12.3a所示。就像在此图中能看到的那样，切削深度(及作为结果的载荷)随着切削刃持续进入切削而逐渐增加。Therefore,themachiningprocessinvolvesnoimpactloading,thusensuringsmootheroperationofthemachinetoolandlongertoollife.Thequalityofthemachinedsurfaceobtainedbyupmillingisnotveryhigh.Nevertheless,upmillingiscommonlyusedinindustry,especiallyforroughcuts.所以，这种工艺没有冲击载荷，从而保证了机床的较平稳运行和较长寿命。通过逆铣所得机加工表面质量不是很高。然而逆铣仍经常被用在工业上，尤其是粗切削时。DownDDownmillingownmillmillinging(climbmilling).AscanbeseeninFig.12.3b,indownmillingthecutterrotationcoincideswiththe课后答案网directionoffeedatthecontactpointbetweenthetoolandtheworkpiece.Itcanalsobeseenthatthemaximumdepthofcutisachieveddirectlyasthecutterengageswiththeworkpiece.顺铣(同向铣削)：如同在图www.hackshp.cn12.3b中看到的那样，在顺铣时刀具与工件之间接触点上铣刀旋转与进给方向一致。还可以看到当刀具进入工件切削时直接达到最大切削深度。Thisresultsinakindofimpact,orsuddenloading.Therefore,thismethodcannotbeusedunlessthemillingmachineisequippedwithabacklasheliminatoronthefeedscrew.Theadvantagesofthismethodincludehigherqualityofthemachinedsurfaceandeasierclampingofworkpieces,sincethecuttingforcesactdownward.这会导致一种冲击，或突然加载。因此，这种方法只有当铣床在进给螺栓上配备间隙消除器时才采用。这种方法的优点包括机加工表面质量较高和工件由于切削力向下作用而较容易夹紧。TypesofMillingCuttersThereisawidevarietyofmillingcuttershapes.Eachofthemisdesignedtoperformeffectivelyaspecificmillingoperation.铣刀的类型铣刀的形状类型很多。其中每种都是为有效进行特定的铣削作业而设计的。Generally,amillingcuttercanbedescribedasamultiedgecuttingtoolhavingtheshapeofasolidofrevolution,withthecuttingteetharrangedeitherontheperipheryoronanendfaceoronboth.Followingisaquicksurveyofthecommonlyusedtypesofmillingcutters.通常，铣刀可以被描述为具有旋转实体形状并将切削齿安装在周边或一到两个端面上的多刃切削刀具。下面是常用铣刀类型的快速综览。PlainPlaiPlainPlainmillingnmillmillingmillingcutter.ingcuttcutter.er.Aplainmillingcutterisadisk-shapedcuttingtoolthatmayhaveeitherstraightorhelicalteeth,asshowninFig.12.4a.Thistypeisalwaysmountedonhorizontalmillingmachinesandisusedformachiningflatsurfaces.平面铣刀：平面铣刀是一种盘状切削刀具，它可以具有直齿或螺旋齿，如图12.4a所示。这类铣刀总是安装在卧式铣床上，用于机加工平面。FaceFFacemillingacemillmillingmillingcutter.ingcuttcutter.er.Afacemillingcutterisalsousedformachiningflatsurfaces.Itisboltedattheendofashortarbor,whichisinturnmountedonaverticalmillingmachine.Fig.12.4bindicatesamillingcutterofthistype.端面铣刀：端面铣刀也可用于机加工平面。它用螺栓固定在短刀杆的端部，而短刀杆则依次安装于立式铣khdaw.com床上。图12.4b显示了这类铣刀。PlainPlaiPlainPlainmetalnmetametalmetalslittinglslitslittingslittingsawtingsawsasawcutter.wcuttcutter.er.Fig.12.4cindicatesaplainmetalslittingsawcutter.wecanseethatitactually若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com involvesaverythinplainmillingcutter.平面金属开槽锯刃铣刀：图12.4c显示了一种平面金属开槽锯刃铣刀。可以看到它其实是一种很薄的平面铣刀。SideSSidemillingidemillmillingmillingcutter.ingcuttcutter.er.Asidemillingcutterisusedforcuttingslots,grooves,andsplines.AsshowninFig.12.4d,itisquitesimilartotheplainmillingcutter,thedifferencebeingthatthistypehasteethonthesides.Asisthecasewiththeplaincutter,thecuttingteethcanbestraightorhelical.侧铣刀：侧铣刀用于切削狭槽、凹槽和花键槽。正如图12.4d所示，它与平面铣刀十分相似，差别在于此类铣刀齿在侧面。象平面铣刀的情况一样，切削齿既可以是直的也可以是螺旋的。AngleAnglAngleAnglemillingemillmillingmillingcutter.ingcuttcutter.er.Ananglemillingcutterisemployedincuttingdovetailgrooves,ratchetwheels,andthelike.Fig.12.4eindicatesamillingcutterofthistype.倾斜铣刀：倾斜铣刀用于切削燕尾槽、棘轮之类的。图12.4e显示了这类铣刀。T-slotT-slT-slotT-slotcutter.otcuttcutter.er.AsshowninFig.12.4f,aT-slotcutterinvolvesaplainmillingcutterwithanintegralshaftnormaltoit.Asthenamesuggests,thistypeisusedformillingT-slots.T型槽铣刀：如图12.4f所示，T型槽铣刀包括了一个平面铣刀和一根垂直于它的整体轴。正像其名字所表明的，这类铣刀用于铣削T型槽。EndEnEndmilldmillmmillcutter.illcuttcutter.er.Endmillcuttersfindcommonapplicationsincuttingslots,grooves,flutes,splines,pocketingwork,andthelike.Fig.12.4gindicatesanendmillcutter.Thelatterisalwaysmountedonaverticalmillingmachineandcanhavetwoorfourflutes,whichmaybeeitherstraightorhelical.khdaw.com端面铣刀：端面铣刀在切削狭槽、凹槽、长凹槽、花键槽、凹状工件之类时均能发现其普遍应用。图12.4g为端面铣刀。它总是安装在立式铣床上，并具有两到四条既可是直的也可是螺旋的长凹槽。FormFFormmillingormmillmillingmillingcutter.ingcuttcutter.er.Theteethofaformmillingcutterhaveacertainshape,whichisidenticaltothesectionofthemetaltoberemovedduringthemillingoperation.Examplesofthistypeincludegearcutters,gearhobs,convexandconcavecutters,andthelike.Frommillingcuttersaremountedonhorizontalmillingmachines.成形铣刀：成形铣刀的齿具有特定的形状，这个形状与铣削时要切削的那部分金属的形状一致。这类铣刀的例子包括齿轮铣刀、齿轮滚刀、凸形和凹形铣刀等等。成形铣刀安装在卧式铣床上。课后答案网MaterialsofMillingCuttersThecommonlyusedmillingcuttersaremadeofhigh-speedsteel,whichisgenerallyadequateformostjobs.铣刀的材料www.hackshp.cn普通使用的铣刀用高速钢制造，这对一般大多数工作已足够。Millingcutterstippedwithsinteredcarbidesorcastnonferrousalloysascuttingteethareusuallyemployedformassproduction,whereheaviercutsand/orhighcuttingspeedsarerequired.对大规模生产而言，因为其需要重型切削和/或高切削速度，铣刀顶端常装有烧结碳化物或有色金属碳合金作为切削齿。第十三单元•Introduction导言Ithasalreadybeenstatedthattheworkpiecemustbelocatedrelativetothecuttingtool,andbesecuredinthatposition.Aftertheworkpiecehasbeenmarkedout,itisstillnecessarytopositionitwithrespecttothemachinemovements,andtoclampitinthatpositionbeforemachiningisstarted.已经说明了工件必须相对于切削刀具定位并确保到位。工件划线后，仍有必要将其相对于切削运动定位，并在机加工开始前把它装夹到位。Whenseveralidenticalworkpiecesaretobeproducedtheneedtomarkouteachpartiseliminatedbytheuseofjigsandfixtures,butifacastingorforgingisinvolved,atrialworkpieceismarkedout,toensurethattheworkpiececanbeproducedfromit,andtoensurethatribs,cores,etc.havenotbecomemisplaced.当要加工若干同样的工件时，使用钻模和夹具可以不必在每个工件上划线；但对铸件或锻件而言，还需取一试验工件划线以保证照此加工不会将加强肋、型芯等放错位置。Jigsandfixturesarealikeinthattheybothincorporatedevicestoensurethattheworkpieceiscorrectlylocatedandclamped,buttheydifferinthatjigsincorporatemeansoftoolguidingduringtheactualcuttingoperation,andfixturesdonot.钻模和夹具的相似点是它们都把保证工件正确定位和夹紧的装置相结合，它们的不同在于钻模在实际切削作业中还能与刀具导向方法相结合，而夹具则不能。khdaw.comInpractice,theonlycuttingtoolsthatcanbeguidedwhileactuallycuttingaredrills,reamers,andsimilarcutters;andsojigsareassociatedwithdrillingoperations,andfixtureswithallotheroperations.Fixturesmayincorporatemeansof若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com settingthecuttingtoolsrelativetothelocationsystem.实际上，在真实切削中能被导向的切削刀具只有钻头、铰刀和类似的刀具；因此钻模用于钻削作业，而夹具用于其余作业。夹具可以与切削刀具相对定位系统装夹的方法结合在一起。Theadvantagesofjigsandfixturescanbesummarisedasfollows:1)Markingoutandothermeasuringandsettingoutmethodsareeliminated;2)Unskilledworkersmayproceedconfidentlyandquicklyinknowledgethattheworkpiececanbepositionedcorrectly,andthetoolsguidedorset;钻模和夹具的优点可归纳如下：1)可以省去划线和其它测量及放样程序；2)在知道工件能正确定位、刀具能恰当导向或装夹的情况下，不熟练的工人也能自信而快速地操作；3)theassemblyofpartsisfacilitated,sinceallcomponentswillbeidenticalwithinsmalllimits,and“trying”andfilingofworkiseliminated;4)Thepartswillbeinterchangeable,andiftheproductsoldoverawidearea,theproblemofsparepartswillbesimplified.3)由于所有零件在较小极限范围内是相同的，可以省掉工件的‘试装’和锉削，所以零件装配很方便；4)零件具有互换性，这样如果产品在较大范围内销售的话，备件问题将简单化。Boltholesoftenhave1.5mmoreven3.0mmclearanceforthebolt,andthereadermaydoubtthenecessityofmakingprecisionjigsforsuchwork.Itmustberememberedthatthejigs,oncemade,willbeusedonmanycomponents,khdaw.comandtheextracostofanaccuratelymadejigisspreadoveralargeoutput.螺栓孔常给螺栓留出1.5毫米或甚至3.0毫米的间隙，读者可能会怀疑为这样的工作制造精密钻模的必要性。但要记住，这种钻模一旦造好，可用于许多零部件，精确制造钻模的额外成本可分摊在大量产品上。Furthermore,itissurprisinghowsmallerrorsaccumulateinamechanismduringitsassembly.Whenaclearanceisspecified,itisbettertoensureitsobservance,ratherthantoallowcarelessmarkingoutandmachiningtoencroachuponit．此外，这样做在装配机械装置时其累积误差之小也是令人惊讶的。在确定一个间隙时，最好能保证它的习惯要求，课后答案网而不是随便划线和机加工使其超出正常的界限。1)TheThThelocationelocalocationlocationoftionofofworkpiece.wworkpiece.orkpiece.Fig.13.1representsabodythatiscompletelyfreeinspace.Inthisconditionithassixdegreesoffreedom.ConsiderthesefreedomswithrespecttothethreemutuallyperpendicularaxesXX,www.hackshp.cnYY,andZZ.1)工件的定位：图13.1表示一个在空间完全自由的物体，在这种情况下它具有六个自由度。相对于三根互相垂直的坐标轴XX、YY和ZZ来考虑这些自由度。Thebodycanmovealonganyoftheseaxes;itthereforehasthreefreedomsoftranslation.Itcanalsorotateaboutanyofthethreeaxes;itthereforehasthreefreedomsofrotation.Thetotalnumberoffreedomsissix.Whenworkislocated,asmanyofthesefreedomsaspossiblemustbeeliminated,toensurethattheoperationisperformedwiththerequiredaccuracy.此物体能沿三根坐标轴的任意一根移动；这样就具有三个平移自由度。它也能围绕三根坐标轴的任意一根回转；这样它又具有三个旋转自由度。总的自由度数目是六个。当工件被定位时，必须尽可能多地消除这些自由度，以保证作业按要求精度进行。Accuracyisensuredbymachiningsuitablelocationfeaturesasearlyaspossible,andusingthemforalllocation,unlessotherconsiderationsmeanthatotherlocationfeaturesmustbeused.Ifitisnecessary,thenewlocationfeaturesmustbemachinedasaresultoflocationfromtheformerlocationfeatures.除非有必要采用另外定位要素的其它考虑，精度可通过尽可能早地加工合适的定位要素并采用它们进行所有定位来保证。如果必要的话，新的定位要素必须作为先前的定位要素的定位结果来加工。2)TheThTheclampingeclamclampingclampingofpingofofthetheththeworkpiece.eworkworkpiece.piece.Theclampingsystemmustbesuchthattheworkpieceisheldagainstthecuttingforces,andtheclampingforcesmustnotbesogreatastocausetheworkpiecetobecomedistortedordamaged.2)工件的装夹：装夹系统必须使工件对着切削力夹持，而且装夹力又不能大得引起工件变形或损坏。Theworkpiecemustbesupportedbeneaththepointofclamping,toensurethattheforcesaretakenbythemainframeofthejigorfixture,andontothemachinetableandbed.Whenjigsandfixturesaredesigned,theclampingsystemisdesignedtoensurethatthecorrectclampingforceisapplied,andthattheclampscanbeoperatedquicklybutwithsafety.工件必须在装夹点下被支撑，以保证这些力由钻模或夹具的主框架来承受并传递给机器台和床身。在设计钻模和夹具时，要同时设计装夹系统来保证提供恰当的装夹力，并使装夹操作快速而安全。•DefinitionofaDrillJig钻模的定义khdaw.comAdrilljigisadeviceforensuringthataholetobedrilled,tapped,orreamedinaworkpiecewillbemachinedintheproperplace.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 钻模是一种确保在工件正确位置进行钻孔、攻丝或铰孔加工的装置。Basicallyitconsistsofaclampingdevicetoholdthepartinpositionunderhardened-steelbushingsthroughwhichthedrillpassesduringthedrillingoperation.Thedrillisguidedbythebushings.它基本上由在淬硬钢衬套下将零件夹持到位的夹持装置组成，钻孔作业中钻头穿过这些衬套，通过它们来导向。Iftheworkpieceisofsimpleconstruction,thejigmaybeclampedontheworkpiece.Inmostcases,however,theworkpieceisheldbythejig,andthejigisarrangedsothattheworkpiececanbequicklyinsertedandasquicklyremovedafterthemachiningoperationisperformed.如果工件结构比较简单，钻模可夹持在工件上。然而大多数情况下，工件由钻模来夹持，并且把钻模设计成能将工件迅速装入而在加工后同样能很快取出。Jigsmakeitpossibletodrill,ream,andtapholesatmuchgreaterspeedsandwithgreateraccuracythanwhentheholesareproducedbyconventionalhandmethods.Anotheradvantageisthatskilledworkersarenotrequiredwhenjigsareused.Responsibilityfortheaccuracyofholelocationistakenfromtheoperatorandgiventothejig.相对于用常规的手工方法加工孔，钻模使得钻孔、铰孔和攻丝速度快很多而且精度更高成为可能。另一个优点是采用钻模时不需要熟练工人。保证孔定位精度的责任从操作者身上转移到了钻模上。Thetermjigshouldbeusedonlyfordevicesemployedwhiledrilling,reaming,ortappingholes.Itisnotfastenedtothemachineonwhichitisusedandmaybemovedaroundonthetableofthedrillingmachinetobringeachbushingdirectlyunderthedrill.Jigsphysicallylimitandcontrolthepathofthecuttingtool.钻模这个术语只用在服务于钻孔、铰孔或攻丝的装置上。它不固定在使用它的钻床上，它能在钻床工作台khdaw.com上到处移动以使每个衬套都直接位于钻头下。钻模有形地限制和控制钻削刀具的路径。Iftheoperationincludesmachiningoperationslikemilling,planing,shaping,turning,etc.,thetermfixtureshouldbeused.Afixtureholdstheworkduringmachiningoperationsbutdoesnotcontainspecialarrangementsforguidingthecuttingtool,asdrilljigsdo.如果作业还包括其它象铣削、刨削、成型、车削等机加工，则应采用夹具这一术语。夹具在机加工作业时夹持工件，但它不象钻模那样包含引导切削刀具的特殊布置。•TypicalJigsandFixtures课后答案网典型的钻模和夹具TypicalTypiTypicalTypicaldrillcaldrildrilldrilljig.ljig.jjig.ig.Figure13.2illustratesadrillingjigfordrillingfourholesintheflangeofaworkpiecethathasbeencompletedexceptforthefourholes.www.hackshp.cn典型的钻模：图13.2所示为一个能在某工件的法兰上钻四个孔的钻模，该工件除了这四个孔外已全部完成。Theworkpiecehasanaccuratelymachinedbore,andislocatedfromtheboreandtheendface,fromacylindricalpost.Thereisnoneedtocontroltherotationalpositionabouttheaxisofthebore,becauseuptothetimewhentheholesaredrilled,itissymmetricalaboutthataxis.此工件有一精确机加工的大孔，因此通过一圆柱体采用该孔和工件端面定位。由于直至钻这些小孔时，工件都对称于大孔轴线，所以没必要控制围绕大孔轴线回转的位置。Thefourbushesusedtocontrolthedrillareheldinthedrillplate,which,withthehandnut,isusedtoclamptheworkpieceagainstthebaseofthefixture.四个控制钻头的衬套装在钻板里，连同手拧螺母一起用于靠着夹具基座夹持工件。TypicalTypiTypicalTypicalmillingcalmillmillingmillingfixture.ingfixtfixture.ure.Figure13.3illustratesasimplemillingfixtureformillingtheslotintheotherwisecompletedworkpieceshown.Theworkpieceislocatedfromtwoofthefourholesinitsbase,andfromtheundersideofthebase.典型的铣削夹具：图13.3所示为一用于在图示其它工序都完成的工件上铣槽的简单铣削夹具。此工件采用其基座上四孔中的两孔和基座的底面定位。Theworkpieceisclampedinposition,andcutterislocatedagainstthesettingblock,whichprovidessettingorcutterpositionanddepthofcut.工件被夹持到位，铣刀靠着提供安装或铣刀位置及切削深度的安装台定位。Thefixturemustbepositionedrelativetothemachinetable,thisisdonebyengagingthetwotenonsatthebottomofthefixtureintheslotinthemachinetable.ThefixtureissecuredtothemachinetablewithT-bolts,alsoengagingintheslotsinthetable(Fig.13.3).夹具必须相对于铣床工作台定位，这可通过把夹具底部的两个凸榫插入工作台上的槽中来实现。夹具用T型螺栓固定于铣床工作台，同时与工作台上的槽接合(图13.3)。khdaw.com若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 第十四单元•Dimensioning标注尺寸Thedesignofamachineincludesmanyfactorsotherthanthoseofdeterminingtheloadsandstressesandselectingthepropermaterials.机械设计除了计算载荷和应力、选择合适的材料外，还包括许多其它因素。Beforeconstructionormanufacturecanbegin,itisnecessarytohavecompleteassemblyanddetaildrawingstoconveyallnecessaryinformationtotheshopmen.Thedesignerfrequentlyiscalledupontocheckthedrawingsbeforetheyaresenttotheshop.Muchexperienceandfamiliaritywithmanufacturingprocessesareneededbeforeonecanbecomeconversantwithallphasesofproductiondrawings.在建造或制造开始前，完成装配图和零件图以把必要信息传达给车间工人是必须的。在送往车间前设计者常常被召集来检查图纸。而在精通生产图纸的所有情况之前，需要有许多经验并熟悉制造工艺。Drawingsshouldbecarefullycheckedtoseethatthedimensioningisdoneinamannerthatwillbemostconvenientandunderstandabletotheproductiondepartments.Itisobviousthatadrawingshouldbemadeinsuchawaythatithasoneandonlyoneinterpretation.图纸必须仔细检查其尺寸是否按生产部门最方便易懂的方式标注。很明显图纸应该只有唯一的解释。Inparticular,shoppersonnelshouldnotberequiredtomaketrigonometricorotherinvolvedcalculationsbeforethekhdaw.comproductionmachinescanbesetup.Dimensioningisaninvolvedsubjectandlongexperienceisrequiredforitsmastery.尤其是不能要求车间工人在生产机械安排前进行三角或其它复杂的计算。尺寸标注是一项复杂的工作，要掌握它需要有丰富的经验。Tolerancesmustbeplacedonthedimensionsofadrawingtolimitthepermissiblevariationsinsizebecauseitisimpossibletomanufactureapartexactlytoagivendimension.由于要把零件加工到正好为给定尺寸是不可能的，因此图纸的尺寸必须加上公差以限制其可允许的变化。课后答案网Althoughsmalltolerancesgivehigherqualityworkandabetteroperatingmechanism,thecostofmanufactureincreasesrapidlyasthetolerancesarereduced,asindicatedbythetypicalcurveofFig14.1.Itisthereforeimportantthatthetolerancesbespecifiedatthelargestvaluesthattheoperatingorfunctionalconsiderationspermit.www.hackshp.cn虽然较小公差能得到较高加工质量和较好操作机构，但随着公差的减小制造成本会迅速增加，如图14.1的典型曲线所示。因此公差被定为从操作或功能考虑允许的最大值是重要的。Tolerancesmaybeeitherunilateralorbilateral.Inunilateraldimensioning,onetoleranceiszero,andallthevariationsaregivenbytheothertolerance.Inbilateraldimensioning,ameandimensionisusedwhichextendstothemidpointofthetolerancezonewithequalplusandminusvariationsextendingeachwayfromthisdimension.公差既可以是单向的也可以是双向的。单向标注有一公差为零，所有变化都由另一公差给定。而双向标注则采用一平均尺寸，它将公差带中点从该尺寸双向扩展为相等的正负变化范围。Thedevelopmentofproductionprocessesforlarge-volumemanufactureatlowcosthasbeenlargelydependentuponinterchangeabilityofcomponentparts.Thusthedesignermustdetermineboththepropertolerancesfortheindividualparts,andthecorrectamountofclearanceorinterferencetopermitassemblywiththematingparts.大规模低成本制造生产工艺的发展很大程度取决于组成零件的互换性。因此设计者必须确定单个零件的合适公差以及配合零件装配允许的正确间隙或过盈量。Themannerofplacingtolerancesondrawingsdependssomewhatonthekindofproductortypeofmanufacturingprocess.Ifthetoleranceonadimensionisnotspecificallystated,thedrawingshouldcontainablanketnotewhichgivesthevalueofthetoleranceforsuchdimensions.在图纸上标注公差的方法相当程度上依赖于产品的性质或制造工艺的类型。如果尺寸公差没有特别注明，图纸应该包含一个给出这些尺寸公差值的普遍适用注释。However,somecompaniesdonotuseblanketnotesonthesuppositionthatifeachdimensionisconsideredindividually,widertolerancesthanthosecalledforinthenotecouldprobablybespecified.Inanyeventitisveryimportantthatadrawingbefreefromambiguitiesandbesubjectonlytoasingleinterpretation.然而有些公司不采用普遍适用注释，假定每个尺寸是单独被考虑的，可能会规定出比注释中要求的更宽的公差。在任何情况下图纸不模棱两可并只服从于单一的解释是十分重要的。•DimensionandTolerance尺寸和公差khdaw.comIndimensioningadrawing,thenumbersplacedinthedimensionlinesrepresentdimensionthatareonlyapproximateanddonotrepresentanydegreeofaccuracyunlesssostatedbythedesigner.若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 在图纸标注尺寸时，除非设计者有意标明，注在尺寸线上的数字代表的尺寸仅仅是近似的，并不代表任何精度等级。Tospecifyadegreeofaccuracy,itisnecessarytoaddtolerancefigurestothedimension.Toleranceistheamountofvariationpermittedinthepartorthetotalvariationallowedinagivendimension.为了详细标明精度等级，有必要在尺寸上增加公差数字。公差是零件允许的变动量或给定尺寸允许的总变动。Ashaftmighthaveanominalsizeof2.5in.(63.5mm),butforpracticalreasonsthisfigurecouldnotbemaintainedinmanufacturingwithoutgreatcost.Hence,acertaintolerancewouldbeaddedand,ifavariationof±0.003in.(±0.08mm)couldbepermitted,thedimensionwouldbestated2.500±0.003(63.5±0.08mm).一根轴可能的名义尺寸为2.5in.(63.5mm)，但由于实际原因不用大成本是不能在制造中保持这个数字的，因此要增加确定的公差。如果允许有±0.003in.(±0.08mm)的变化，则此尺寸可表达为2.500±0.003(63.5±0.08mm)。Dimensionsgivenclosetolerancesmeanthatthepartmustfitproperlywithsomeotherpart.Bothmustbegiventolerancesinkeepingwiththeallowancedesired,themanufacturingprocessesavailable,andtheminimumcostofproductionandassemblythatwillmaximizeprofit.具有紧密公差的尺寸表示该零件必须恰当地与某些其它零件配合。所采用的制造工艺和使利润最大化的最小生产及装配成本都要求给定公差以保持所需允差。Generallyspeaking,thecostofapartgoesupasthetoleranceisdecreased.Ifaparthasseveralormoresurfacestobemachined,thecostcanbeexcessivewhenlittledeviationisallowedfromthenominalsize.khdaw.com一般而言，零件的成本随着公差的减小而上升。如果一个零件有若干或较多表面要机加工，且几乎不允许偏离名义尺寸，则成本会超过正常合理的界限。Allowance,whichissometimesconfusedwithtolerance,hasanaltogetherdifferentmeaning.Itistheminimumclearancespaceintendedbetweenmatingpartsandrepresentstheconditionoftightestpermissiblefit.允差，有时会跟公差混淆，但其具有完全不同的含义。它是配合零件之间最小的预期间隙空间，代表着允许的最紧配合条件。Ifashaft,size1.498+0.003-0.003,istofitaholeofsize1.500课后答案网,theminimumsizeholeis1.500andthemaximumsizeshaftis1.498.Thustheallowanceis0.002andthemaximumclearanceis0.008asbasedontheminimumshaftsizeandmaximumholedimension.如果一根尺寸为1.498+0.003-0.003www.hackshp.cn的轴与尺寸为1.500的孔配合，孔的最小尺寸为1.500而轴的最大尺寸为1.498。这样允差就是0.002，而由最小轴尺寸和最大孔尺寸形成的最大间隙为0.008。Tolerancesmaybeeitherunilateralorbilateral.Unilateraltolerancemeansthatanyvariationismadeinonlyonedirectionfromthenominalorbasicdimension.Referringtothepreviousexample,theholeisdimensioned1.500+0.003,whichrepresentsaunilateraltolerance.公差可以是单向的也可以是双向的。单向公差意味着任何变动都是只从名义或基本尺寸出发向一个方向变动的。引用前例，孔的尺寸标注为1.500+0.003，它表示了一个单向公差。Ifthedimensionsweregivenas1.500±0.003,thetolerancewouldbebilateral;thatis,itwouldvarybothoverandunderthenominaldimension.Theunilateralsystempermitschangingthetolerancewhilestillretainingthesameallowanceortypeoffit.如果尺寸标为1.500±0.003，就是双向公差；即它可以在名义尺寸之上或之下变化。单向体系允许在依然保留相同允差或配合类型的情况下改变公差。Withthebilateralsystem,thisisnotpossiblewithoutalsochangingthenominalsizedimensionofoneorbothofthetwomatingparts.Inmassproduction,wherematingpartsmustbeinterchangeable,unilateraltolerancesarecustomary.Tohaveaninterferenceorforcefitbetweenmatingparts,thetolerancesmustbesuchastocreateazeroornegativeallowance.而双向体系在不同时改变一个或两个配合零件名义尺寸的情况下，这是不可能做到的。大规模生产中配合零件必须能互换，单向公差是经常遇到的。为了使配合零件之间具有过盈或强制配合，公差必须产生零或负允差。•Tolerances,LimitsandFits公差、极限和配合Thedrawingmustbeatrueandcompletestatementofthedesigner’srequirementsexpressedinsuchawaythatthepartisconvenienttomanufacture.图纸必须按方便制造零件的方式将设计者的要求真实和完整地表达出来。Everydimensionnecessarytodefinetheproductmustbestatedonceonlyandnotrepeatedindifferentviews.Dimensionsrelatingtooneparticularfeature,suchasthepositionandsizeofahole,should,wherepossible,appearonkhdaw.comthesameview.对每一描述产品所需的尺寸都只须标注一次而不必在不同的视图中重复。有关同一特性的尺寸，诸如孔的位置和大若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com 小，如果可能应出现在同一视图上Thereshouldbenomoredimensionsthanareabsolutelynecessary,andnofeatureshouldbelocatedbymorethanonedimensioninanydirection.除绝对需要的尺寸外，不应该有更多的尺寸；而在任意方向上，只能在一个尺寸上标注特性要求。Itmaybenecessaryoccasionallytogiveanauxiliarydimensionforreference,possiblyforinspection.Whenthisisso,thedimensionshouldbeenclosedinabracketandmarkedforreference.Suchdimensionsarenotgovernedbygeneraltolerances.偶尔也可能为了检查而必须给出供参考的辅助尺寸。在这种情况下，尺寸应该用括号括起来，以便参考。这样的尺寸不受通用公差控制。Dimensionsthataffectthefunctionofthepartshouldalwaysbespecifiedandnotleftasthesumordifferenceofotherdimensions.影响零件功能的尺寸总是应该标注的而不要留作其它尺寸的和或差。Ifthisisnotdone,thetotalpermissiblevariationonthatdimensionwillformthesumordifferenceoftheotherdimensionsandtheirtolerances,andthiswillresultinthesetoleranceshavingtobemadeunnecessarilytight.Theoveralldimensionshouldalwaysappear.如果不是这样，那尺寸允许的总的变化将形成其它尺寸及它们的公差的和或差，这会导致这些公差不得不定得过紧。总尺寸一般应该标注。Alldimensionsmustbegovernedbythegeneraltoleranceonthedrawingunlessotherwisestated.Usually,suchakhdaw.comtolerancewillbegovernedbythemagnitudeofthedimension.Specifictolerancesmustalwaysbestatedondimensionsaffectingfunctionorinterchangeability.除非另行说明，所有尺寸都必须受图上的通用公差控制。一般这样的公差受到尺寸量值的控制。在影响功能或互换性的尺寸上必须标注专门的公差。Asystemoftolerancesisnecessarytoallowforthevariationsinaccuracythatareboundtooccurduringmanufacture,andstillprovideforinterchangeabilityandcorrectfunctionofthepart.为了允许在制造过程中必然会发生的精度变化，并提供零件的互换性和正确功能，一个公差系统是必需的课后答案网。Atoleranceisthedifferenceinadimensioninordertoallowforunavoidableimperfectionsinworkmanship.Thetolerancerangewilldependontheaccuracyofthemanufacturingorganisation,themachiningprocessandthemagnitudeofthedimension.www.hackshp.cn公差是为了允许工艺上不可避免缺陷而存在的尺寸上的不同。公差范围取决于制造机构的精度、机加工过程和尺寸的量值。Thegreaterthetolerancerange,thecheaperthemanufacturingprocess.Abilateraltoleranceisonewherethetolerancerangeisdisposedonbothsidesofthenominaldimension.Aunilateraltoleranceisonewherethetolerancezoneisononesideonlyofthenominaldimension,inwhichcasethenominaldimensionmayformoneofthelimits.公差范围越大，则制造过程的成本就越低。双向公差是在公称尺寸两侧都有公差带的公差。单向公差是仅在公称尺寸一侧有公差带的公差，在这种情况下公称尺寸成了两个极限中的一个。Limitsaretheextremedimensionsofthetolerancezone.Forexample,nominaldimension30mmtolerancelimits极限是公差带的极限尺寸。例如公称尺寸30毫米公差极限Fitsdependontherelationshipbetweenthetolerancezonesoftwomatingparts,andmaybebroadlyclassifiedintoaclearancefitwithpositiveallowance,atransitionfitwheretheallowancemaybeeitherpositiveornegative(clearanceorinterference),aninterferencefitwheretheallowanceisalwaysnegative.配合取决于两配合零件公差带之间的关系，并且可以概括地分为具有正允差的间隙配合，允差可以是正或负的过渡配合和总是负允差的过盈配合。•TypeofLimitsandFits极限和配合的类型TheISOSystemofLimitsandFits,widelyusedinanumberofleadingmetriccountries,isconsiderablymorecomplexthantheANSIsystem.在一些最主要采用公制的国家中广泛使用的ISO的极限和配合系统，比ANSI的极限和配合系统要复杂得多。Inthissystem,eachparthasabasicsize.Eachlimitofsizeofapart,highandlow,isdefinedbyitsdeviationfromthebasicsize,themagnitudeandsignbeingobtainedbysubtractingthebasicsizefromthelimitinquestion.Thedifferencebetweenthetwolimitsofsizeofapartiscalledthetolerance,anabsoluteamountwithoutsign.在这个系统中，每个零件都有基本尺寸。零件尺寸的每一极限，不管大小，都通过对基本尺寸的偏差来定khdaw.com义；其量值和符号由正被讨论的极限减去基本尺寸得到。零件尺寸的两个极限之差称为公差，这是一个没有符号的绝对量值。若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com Therearethreeclassesoffits:1)clearancefits,2)transitionfits(theassemblymayhaveeitherclearanceorinterference),and3)interferencefits.存在三种配合：1)间隙配合，2)过渡配合(装配后可以有间隙或过盈)，和3)过盈配合。Eitherashaft-basissystemorahole-basissystemmaybeused.Foranygivenbasicsize,arangeoftolerancesanddeviationsmaybespecifiedwithrespecttothelineofzerodeviation,calledthezeroline.基轴制或基孔制均可采用。对任何给定的基本尺寸，公差范围和偏差可以相对于被称为零线的零偏差线来确定。Thetoleranceisafunctionofthebasicsizeandisdesignatedbyanumbersymbol,calledthegrade—thusthetolerancegrade.公差是基本尺寸的函数并通过一个被称为等级的数字符号标明—即公差等级。Thepositionofthetolerancewithrespecttothezerolinealsoafunctionofthebasicsize—isindicatedbyalettersymbol(ortwoletters),acapitalletterforholesandalowercaseletterforshafts.Thusthespecificationforaholeandshafthavingabasicsizeof45mmmightbe45H8/g7.公差相对于零线的位置同样为基本尺寸的函数通过一个或两个字母符号表达，大写字母表示孔而小写字母表示轴。这样基本尺寸为45毫米的一个孔和轴配合规格可能是45H8/g7。Twentystandardgradesoftolerancesareprovided,calledIT01,IT0,IT1~18,providingnumericalvaluesforeachnominaldiameter,inarbitrarystepsupto500mm(forexample0~3,3~6,6~10,......,400~500mm).ISO规定了二十种标准的公差等级，称之为IT01，IT0，IT1~18，给在直至500毫米强行分段(例如0~3，3~6，6~10,......,400~500khdaw.com毫米)中的公称直径提供具体数值。Thevalueofthetoleranceunit,i,forgrades5~16isWhereiisinmicronsandDinmillimeters.对5～16级而言，公差单位i的值可用下式计算这里i的单位是微米，而D的单位是毫米。Standardshaftandholedeviationssimilarlyareprovidedbysetsofformulas,however,forpracticalapplication,bothtolerancesanddeviationsareprovidedinthreesetsofrathercomplextables.标准的轴和孔偏差同样都由若干公式提供；然而对实际应用，公差和偏差都在三张相当复杂的表格中规定了。Additionaltablesgivethevaluesforbasicsizesabove500mmandfor“CommonlyUsedShaftsandHoles”intwocategories—“GeneralPurpose”and“FineMechanismsandHorology课后答案网”.对基本尺寸大于500毫米和在“一般用途”和“精密机械和钟表”两个类别中的“常用的轴和孔”而言，由附加的表格给出数值。www.hackshp.cnkhdaw.com若侵犯了您的版权利益，敬请来信通知我们！℡www.khdaw.com'