材控专业英语4.Plastic-forming process and dies

Chapter4PlasticFormingProcessandDiesChapter4PlasticFormingProcessandDies4.1ForgingWordsandterms:Die模具，凹模Seasoned适用的Unparalleled空前的，无比的Conveyance运输工具GrossNationalProduct国民生产总值Difficult-to-machinealloy难切削合金Forging锻造，锻件

forgeman

锻工Augment增长，发展

cryogenic低温的Nationaldefence

国防4.1ForgingThissectionisabriefintroductiontotheforgingindustryanditsproductsintermsoftheirimportantroleinourwayoflife,

highlightingtheirtechnologicalandeconomicsignificance.由于锻造工业及锻件在人们生活方式中起着很重要的作用，本节简单介绍锻造工业及锻件，并突出其技术（意义）和经

济意义。Thissectionisabriefintroduction，主句

4.1ForgingInearlierdaysforgingwastheprocessofshapingmetalbyheatingandhammering.过去，锻造是一种利用加热和锤击使金属成形的工艺。Today,metalisnotalwaysheatedforforgingandtheworkmaybeperformedbyseveraltypesofheavymachineswhichapplyimpactorsqueezepressurewithswiftprecision.现在，金属不必通过加热来锻造，可以采用不同类型的重型机械来完成，这些机械具有冲击力和挤压力以及高精准度。4.1ForgingIntoday’sforgingindustrytheskillandseasonedjudgmentoftheforgemanisenhancedbythemachinesofmoderntechnologytoproducemetalpartsofunparalleledstrengthandutility.在如今的锻造工业中，现代机械技术提高了锻工的技术以及丰富的经验，使其能够制造高强度和广泛应用的金属工件。Theartofforgingisbeingaugmentbythescienceofforgingatanincreasinglyrapidrate.Thus,asservicerequirementsformechanicalpartshavebecomemoresevere,forginghasbecomemorethanthemereshapingofmetal.锻造工艺随着锻造学科的发展，取得了长足的进步。这样，随着对机械零件应用的需要日益增加，锻造不仅仅用来使金属成形。4.1ForgingForgingpermitsthestructureofmetalstoberefinedandcontrolledtoprovideimprovedmechanicalproperties.锻造能细化并控制金属组织，从而提高力学性能。Also,forgingproducesacontinuous“grainflow”inthemetalwhichcanbeorientedtofollowtheshapeofthepartandresultinmaximumstrengthefficiencyofthematerial.而且，锻造在金属中产生了连续的“晶粒流动”，使晶粒能够沿着零件形状取向，从而使材料达到最大的强度效能。4.1ForgingSincevirtuallyallmetalscanbeforged--fromalumimumtozirconium—extensivecombinationsofmechanicalandphysicalpropertiesareavailabletomeetdemandingspaceageapplication.事实上，几乎所有金属都可以被锻造--从铝到锆，可以通过机械性能和物理性能的良好结合，来满足太空时代的应用需求。4.1Forging4.1ForgingTechnically,forgingmaybedefinedastheprocessofgivingmetalincreasedutilitybyshapingit,refiningit,andimprovingitsmechanicalpropertiesthroughcontrolledplasticdeformationunderimpactorpressure.从技术上说，锻造可定义为在冲击力或者压力作用下通过控制塑性变形使金属成形、细化及改善金属机械性能来扩大应用范围的工艺。4.1ForgingButthetruemeaningofforgingcanbemoreclearlyrecognizedbyconsideringthevarietyofwaysitservesmankindandtheimportantcharacteristicsforgedpartsofferthosewhodesign,purchaseandusethem.但是，锻造的真正意义被意识到是通过它服务于人类的多样化以及设计、购买和应用他们的客户赋予锻件的重要特性。4.1ForgingForgingarecommonlyfoundinmachinesandconveyancesatcriticalpointsofshockorstress-particularlywherereliabilityandhumansafetyareaffected,andyetthegreatvarietyofshapes,sizesandpropertiesavailableinforgingshasextendedthelistofcurrentapplicationsandpotentialfutureusesfarbeyondthispoint.通常，锻件用于机械或交通运输工具的承受振动或应力的关键部位，特别是关系到可靠性和人身安全，并且，形状、尺寸和性能的变化大大扩大了锻件的应用范围，其未来应用远不止于此。4.1ForgingFromthestandpointofsize,forexample,forgingsmayrangefromtinycashregisterpartsweightingfractionsofanouncetomassivestructuralcomponentsweightingseveraltons.以尺寸为例，锻件的尺寸范围从重量不到一盎司的微型收银机零件到数吨的大型结构件。Likewise,forgingsareavailableinshapescoveringvirtuallyeverybasicconfigurationusefultoman.同样，锻件可以得到各种形状，涵盖了对人类有用的所有基本外形。Fromthestandpointof，从…角度来看

4.1ForgingTheyserveinoperatingtemperaturerangingfromcryogeniclevelstoover3000°Fandinenvironmentascorrosiveasnaturecandevise.锻件的服役温度从低温到高达3000华氏度，可在类似自然界腐蚀环境中使用。Forgingareeconomicallycompetitivewithothertypesofpartsproducedincorrespondingmaterials.与同种材料的其他成形方法相比，锻件在经济上具有竞争力。4.1ForgingWhilethecommercialforgingindustryisnothugeinrelationtotheGrossNationalProduce,itisagiantinitscontributiontoourstandardoflivingandournationaldefence.锻造工业在国民生产总值中所占比例并不大，但它在日常生活和国防中的作用巨大。Theoperatingcapabilitiesofmosttoday´smachinesandconveyanceslargelydependonthepropertiesachievableinforgedcomponents.当大多数机械和交通运输工具的操作性能主要依靠锻件的性能。4.1ForgingWithoutforgingandtheperformancecharacteristicstheyprovide,autos,airplanes,trucks,farmimplements,earthmovingmachines,missiles,industrialenginesandmachines,andtheimplementsofnationaldefense,asweknowthem,wouldnotbefeasible.没有锻件及其良好的性能，汽车，飞机，卡车，农具，土方机械，导弹，工业引擎和发动机，国防装备都不可行。4.1ForgingModernmanufacturersarelookingahead-anticipatingthefutureneedsofindustryanddevelopingproductsandservicestomeetthem.现代制造商展望未来-预测工业的需求，并开发产品和服务以满足需求。Newmarketsarebeingidentified;newtechnologiesexplored;newmethodandprocessesrefined.新市场正在确立，新技术正在开发，新方法和新工艺正在改进。4.1ForgingAsefficientuseofmaterialbecomesmorenecessary,theabilityofforgingtoprovidestrengthwithminimumweightbecomesmoreattractive.材料的有效利用越来越重要，锻造能够以最低的重量达到所需的强度，因而更具吸引力。。Asmoreuseismadeofcostly,difficult-to-machinealloys,therelativeprecisionanddimensionaluniformityofforgedpartsbecomemoredesirable.Theproductsoftheforgingprocess-asoldasantiquity-arenewastomorrow.由于更多地使用了昂贵的难切削合金，锻件的精密度和尺寸均匀性更加满足需要。古老的锻造工艺正日新月异。4.1.1Closed-DieForgingWordsandterms:Close-dieforging模锻；opendieforging自由锻；

dropstamping锤上模锻；bottomdie下模；tup锤头as-forged锻造的；near-solvus接近固相线；residualstrain残留应变；insulation绝缘，隔热；kineticenergyinput动能输入；discriminating有区别的；glasscoating玻璃敷层，vaporcushioning蒸汽垫4.1.1Closed-DieForgingTheproductionofclosed-dieforginginthetitaniumandnickel-basesuperalloys,whicharespecifiedforthemostexactingaerospaceapplications,isacomplexsequenceofprocesses.钛合金和镍基被指定为最准确的太空应用件，它们的模锻是一系列复杂的工艺过程。Anessentialrequirementiscloseco-operationbetweenthemanufacturerofthebilletmaterialsandthedieforgerresponsibleforshapingthematerialtothegeometry,quality,andengineeringpropertyrequirementsoftheultimatecustomer.模锻的基本要求是将坯料制造和模具成形紧密配合，使材料达到最终客户要求的几何形状、质量和工程性能。4.1.1Closed-DieForgingInforgingbothsuperalloysandtitaniumalloys,strictdisciplinesmustbefollowedtoobtainthedegreeoftemperaturecontrolandthedeformationrateneededtoproduceapredictableas-forgedstructureofthetypewhichwillsatisfactorilyrespondtothenear-solvustemperatureemployedforthefinebalancingofpropertiescalledforbycurrentspecifications.在锻造超合金和钛合金时，需要遵循严格的规范，进行温度和成形速率控制，以获得可预测的锻后结构，这种结构更好地对应固相线温度，可用于很好地复合现行技术规格的性能。4.1.1Closed-DieForgingThemainfactorsneedingcarefulcontrolinachievinganas-forgedstructurewhichisbothpredictableandreproducibleintermsofresidualstrain/grainstructuresare:dieperformgeometry;diepreheatingtemperature;lubrication/insulation;kineticenergyinput;continualmonitoringofworkpiecesurfacetemperature.依据残余应变/晶粒结构可以预测和再生锻后结构，其中需要关注和控制的主要因素是：模具的几何形状、模具的预热温度、润滑/隔热、动能输入以及工件表面温度的持续监控。Thediesarepreheatedtothelimitimposedbythestrengthofdiematerial.模具预热的极限受模具材料的强度影响。Lubrication/insulationneedsdiscriminationuseiftheworkpieceistobesuitablydeformedandapplicationvariesfrom100%coverage,throughpartialcoverage,tonolubrication.Severalglassesofdifferentmeltingpointsandviscositieshavebeeninvestigatedandareusedforbothsuperalloyandtitaniumforgings.

为了工件适用于成形，润滑/隔热需要区别使用，可以全部润滑，部分润滑或者不润滑。几种不同熔点和黏度的玻璃被用于超合金和钛合金锻件4.1.1Closed-DieForging4.1.1Closed-DieForgingIndropstamping,controlofthekineticenergyinputisachievedbytheheighttowhichthetupisraised,thusquiteaccuratelydeterminingtheenergyofeachblow.在锤上模锻中，通过锤子升高的高度控制动能输入，这样可以准确控制每一锤的能量。Thefrequencyoftheblowsneedscarefulcontroltoachieveabalancewhichwillholdthetemperatureoftheforgingwithinanarrowband.锤击的频率需要仔细控制，从而达到平衡，控制锻造温度在一个窄的区间。Todothisinarepeatablemannerinvolvescloseco-operationbetweenthehammeroperativesandthetechnicalstaffwhosupervisetheoperationandconstantlymonitorthesurfacetemperatureoftheworkpiecetoeffectthebalancebetweenkineticheating,naturalcooling,anddiechilling.以重复的方式进行，需要锤子操作者和技工的紧密配合，技工的监控操作，并继续检测工件的表面温度，来影响动态加热、空冷和模具急冷之间的平衡。4.1.1Closed-DieForging4.1.1Closed-DieForgingThelatterisminimizedbyglasscoatingandbyvaporcushioninginthebottomdieinwhichtheforgingsometimeslevitatesandrotates.后者（模具冷却）可用玻璃涂层和下模的蒸汽垫来最小化，在下模中锻件有时会浮起或者旋转。Theadvantanges

intermsofeaseandspeedofhandlingoftheforginginafixedbottomdieareevident,sincedelaysofmorethanafewsecondsduetorelocatingforgingswhichhavejumpedoutofregisterwiththediescanmarkedlyaffecttheendresultsbecauseoftheheatlostduringthedelay锻造在固定下模中处理的方便和速度，其优点很明显。由于再定位锻件退后数秒，锻件会随着模具跳动离开原位置。时间推迟而产生热量损失而显著影响成形效果。4.1.1Closed-DieForgingByusingthetechniques

described

thedegreeofthesurfacechillingoftheforgings

duetodiecontact,withitsconsequenteffectonsurfacecrackingpotentialandlimitationofmetalflowneardiecontactsurfaces,canbeminimized,thusenablinginmanycasesamoreeconomicuseofmaterialthanispossiblewithforgingprocessesinwhichtheforginganddieareincontinuouscontact.采用上述技术，锻件表面与模具接触而冷却的程度可以最小化。这种冷却程度随后影响表面潜在开裂和限制接触模具的区域

金属的流动。许多情况下，在锻造工艺条件下，使锻件和模

具持续接触使用材料更加经济。4.1.2PressForging-压锻Wordsandterms:Press压力机，压力；closedimpressiondie闭式压锻模；Draft阻力，牵引力；dropforging落锤锻；sizingoperation精锻工艺；hydraulicpress液压机；finalforging终锻；pyrometer高温计4.1.2PressForgingPressforgingemploysaslowsqueezingactionindeformingtheplasticmetal,ascontrastedwiththerapid-impactblowsofahammer.Thesqueezingactioniscarriedcompletelytothecenterofthepartbeingpressed,thoroughlyworkingtheentiresection.与采用锤击的快速击打相反，压力锻造采用缓慢的挤压作用使金属变形。挤压作用完全施加在工件中心，彻底使之变形。Thesepressesaretheverticaltypeandmaybeeithermechanicallyorhydraulicallyoperated.Themechanicalpresses,whicharefasteroperatingandmostcommonlyused,rangeincapacityfrom500to10000tons.这种压力由机械或液压垂直施加，机械压力被广泛应用，它可以快速施压，其施压范围为50-10000吨。4.1.2PressForgingForsmallpressforgings,closedimpressiondiesareused,andonlyonestrokeoftheramisnormallyrequiredtoperformtheforgingoperation.小型压锻件可采用闭式压锻模，一次挤压操作就可以完成锻造过程。Themaximumpressureisbuildupattheendofthestrokewhichforcesthemetalintoshape.Diesmaybemountedasseparateunits,orallthecavitiesmaybeputintoasingleblock.压力在挤压动作结束时候达到最大，以使材料成形。模具可以分为多个单元进行固定，所有的凹模也可采用一个模块。Forsmallforgingsindividualdieunitsaremoreconvenient.

Thereissomedifferenceinthedesignofdiesfordifferentmetals,copper-alloyforgingscanbemadewithlessdraftthansteel,consequently,morecomplicatedshapescanbeproduced.Thesealloysflowwellinthedieandarereadilyextruded.对于小型锻件成形更方便。不同金属模具设计不同，铜合金

比钢的锻压阻力小，因此，可以锻造成复杂的形状。这些合

金在模具中流动性好，可以顺利挤出。4.1.2PressForging4.1.2PressForgingIntheforgingpressagreaterproportionofthetotalworkputintothemachineistransmittedtothemetalthaninadrophammerpress.Muchoftheimpactofthedrophammerisabsorbedbythemachineandfoundation.Pressreductionofthemetalisfaster,andthecostofoperationisconsequentlylower.在压力锻造中，传递到金属上的压力比落锤锻的压力要大得多。锻锤的冲击力大部分被机械和底座吸收。金属的压力减少越快，操作成本也相应越低。Mostpressforgingsaresymmetricalinshape,havingsurfaceswhicharequitesmooth,andprovideaclosertolerancethanisobtainedbyadrophammer.大部分压锻件形状比较匀称，表面光滑，比锤锻件有更好的公差等级。However,manypartsofirregularandcomplicatedshapescanbeforgedmoreeconomicallybydropforging.Forgingpressesareoftenusedforsizingoperationsonpartsmadebyotherforgingprocesses.但是，对于形状不规则和复杂的工件来说，采用锤锻比较经济。压锻常用于其他锻压后的精锻工艺4.1.2PressForging4.1.2PressForgingIndropforging,apieceofmetal,roughlyorapproximatelyofthedesiredshape,isplacedbetweendiefaceshavingtheexactformofthefinishedpiece,andforcedtotakethisformbydrawingthediestogether.落锤锻过程中，接近期望形状的片状金属被置于模面之间，最终成形为尺寸精确的工件。Thismethodiswidelyusedforthemanufactureofpartsbothofsteelandbrass.Largeingotsarenowalmostalwaysforgedwithhydraulicpressesinsteadofwithsteamhammers,sincetheworkdonebyapressgoesdeeper.这种成形方法广泛应用于钢和黄铜件的制造。大铸锭目前几乎全部采用液压机取代汽锤进行锻造，这样压力更大。4.1.2PressForgingFurther,thepresscantakeacooleringotandcanworktocloserdimensions.Theforgingshouldbedoneataboutthesametemperatureasrolling;theprocessimprovesthephysicalpropertiesofthesteeljustasrollingdoes.以后，可以进行冷铸锭的成形并接近最终尺寸。锻造应在与轧制相同的温度下进行，与轧制一样可以改善钢的物理性能。Inthefinalforgingitisimportantnottohavethesteeltoohot,foranoverheatedsteelwillhavepoormechanicalpropertieswhencooled.终锻阶段，要注意钢不能太热，因为过热钢冷却后力学性能变差。Inheatingforforgingthetemperatureisusuallyjudgedbytheeye,butwherelargenumbersofthesamepatternaremade,thepiecetobeforgedareheatedinfurnacesinwhichthetemperatureisindicatedbypyrometers,andoftenisautomaticallycontrolled.锻件的加热温度通常用肉眼判断，但制造大量相同方式的

锻件时，通过炉子加热，炉内的温度通过高温温度计测量，

并能实现自动控制。4.1.2PressForgingWordsandterms:Rotarybending旋转模弯曲；veebendingV型槽模弯曲；wipebending折弯弯曲；tonnage吨位；built-incam内置凸轮；consistency一致性4.2RotaryBending

Pressworkingoperationshaveincreaseddramaticallyoverthelastfewyears,butlikemanyothermanufacturingoperations,theexistingtechnologyhassometimesfailedtokeeppacewiththechangingapplications.Oneareawherethisisespeciallytrueisdiebending.压力加工在过去数年中显著增长，但是和许多其他制造方法一样，现有的技术难以与变化的应用保持同步。典型的例子就是弯曲模。4.2RotaryBendingSo,althoughthereisasubstantialincreaseintheapplicationsforbending,thetwomostcommonformsofbendingmethod—veebendingandwipebending—representtechnologiesthataresometimesquiteoutdatedfortoday”shighvolumeproductionrunsandprecisionrequirements.所以，尽管弯曲件的应用大幅增加，两种通用的主要弯曲方式—V型槽模弯曲和折弯弯曲有时明显落后于现代大体积产品的大量生产和精密的要求。4.2RotaryBendingDiebendingoperationsoftenpresentthetooldesignerwithavarietyofproblemareas,especiallywhenhighvolumeproductionisafactor.模具弯曲通常出现一系列问题，特别是大体积产品。4.2RotaryBendingFromproducingproperbendanglesandminimizingpartdistortiontoreducingtherequiredtonnageandkeepingthematerialinplaceduringthebend,theolderveebendingandwipebendingmethodscaneasilycreatemanyproblemsastheysolve.在弯曲过程中，从产生合适的弯曲角度和最小扭曲到减少需求的吨位和固定材料，旧的V型槽模弯曲和折弯弯曲很容易产生许多问题。Butaneweralternative,rotarybending,mayjustbethesolutiontotheproblemscausedbytheotherbendingmethods.但一个新的替代，旋转模弯曲可以解决其他弯曲方法产生的问题。4.2RotaryBendingTherotarybendingprocess,developedandpatentedbyReadyTool,Inc.,Dayton,OH,isahighlyefficientmethodofproducingawiderangeofdifferentbends.旋转模弯曲由ReadyTool公司发明并申请专利，它是一种可生产大范围弯曲件的高效方法。Thisformofbendingdiecanmakepreciseandaccuratebendsinmaterialsrangingfrom0.008in.to0.500in.atbendingtonnagethatare50to80percentlessthanthoserequiredfortheotherbendingmethods.这种弯曲模可以制造高精度的弯曲件，在弯曲吨位下，弯曲精度为0.008-0.500英尺，比其他弯曲方法需要的吨位少50-80%。4.2RotaryBendingAsshowninFig4.1,transferringtheverticalmotionofthepressintoarotarymotionofthebender,permitsahighlyefficientandeffectivemethodofbendingmetal.Usingthisformofbuilt-incamactionalsoprovidesanuncommondegreeofbendingaccuracyandconsistency.如图4.1所示，将压力的垂直运动转换为旋转运动，是高效和具有影响的金属弯曲方法。采用内置凸轮也能提供不寻常的弯曲精度和一致性。4.2RotaryBending4.2RotaryBending图4-1旋转模弯曲过程不需再压模Wheremanybendingoperationswerepreviouslyperformedinaseriesofstepstomaintaintherequiredaccuracy,rotarybendinggenerallypermitstheoperationstobeperformedinpressstroke.之前的弯曲工艺需要一系列工序保证精度，而旋转弯曲通常一次施压就能完成。4.2RotaryBendingRotarybendingwillnotcompletelyreplacetheneedforeitherveebendingorwipebendingforallapplications.Butinthosesituationswhererotarybendingisappropriate,thecostsavingsandoverallefficiencyofvirtuallyanybendingoperationcanbemarkedlyincreased.旋转模弯曲也不能完全替代V型槽模弯曲或者折弯弯曲。但是那些旋转模弯曲适合的情况下，在经济效益和实际效率比其他弯曲方法显著提高。4.2RotaryBendingWordsandterms:Fineblanking精密冲裁；cutedge剪切刃shaving刨削；clearance间隙，公差中的公隙；blank落料件；producinghole冲孔；cuttingpunch冲裁凸模；burr毛刺；bolster垫板；ejector卸料器；orthodox传统的；shearingzone剪切区4.3FineBlankingFineblankingisatechniqueusedforproductionofblanksperfectlyflatandwithacutedgewhichiscomparabletoamachinedfinish.Thisquickandeasyprocessisworthyofseriousthoughtwhenthenumberofpartsjustifiesthecostofablankingtoolespeciallywhenconsiderationisgiventothefactthatoperationssuchasshavingareeliminated.精密冲裁是一种采用剪切刃精确冲裁板料产品的技术，它的剪切刃可与机械精加工相媲美。这种既快捷又方便的加工方法值得认真考虑，特别是考虑到可省掉像刨削这样的操作，零件的数目也证实了冲裁工具的成本下降了。4.3FineBlankingTwomethodsoffineblankingarepracticedaccordingtothetypeofworkundertakenasfollows:(1)Thepunchhasaroundedgeandasmallclearanceandthisisbestusedforblanks,butappearstogivelesssatisfactoryresultswhenusedforproducingholes.(2)ThismethodusesacuttingpunchwhichissurroundedbyaV-shapedgripperwhichmakesaV-grooveroundtheprofileandthusclampstheblanksecurelybeforeanonroundpunchcontactsthesurface.根据加工工件的类型可分为以下两种精密冲裁方法：(1)凸模有圆角边和小的间隙，这最适合于落料件，但是对于冲孔似乎没有较满意的结果(2)该方法使用一个外廓四周形成V槽的V型夹板包围的的冲裁凸模，在一个非圆形的凸模接触表面之前，夹具紧紧夹住落料件。4.3FineBlankingInmethod1theradiusontheedgeofadieisselectedaccordingtothetypehardnessandthicknessofaparticularmaterialcoupledalsototheshapeofaprofileonthecomponent.在方法1中，冲模的圆角半径由特定材料的硬度和厚度以及轮廓外形决定。Howeversomeimportanceisattachedtothisradius,otherwisealargeincreasecancausedistortionandcreateaburrontheundersideoftheblank.Thustheminimumradiusthatwillimpartagoodresultonacomponentisanessentialfeatureandthisradiuscanvaryfrom0.3to2mmaccordingtoconditions.半径很重要，半径过大会导致变形和在落料件的下侧出现毛刺。因此，最小半径是一个重要特性，有利于零件。根据不同条件，半径可在0.3-2之间变化。4.3FineBlankingGenerallytheloadrequiredforfineblankingisnomorethan10%greaterthantheloadneededforconventionalblanking.通常精密冲裁所需的加载只比传统冲裁大10%。Greaterradiusandthusburstingpressuresareexperiencedwiththisoperation,soattentiontobethedesignofthetoolisnecessaryandthisusuallymeanssinkingthediecompletelyintoabolsterofadequateproportions.精密冲裁可以加工大半径和得到大的爆裂压力，因此必须注意工具设计，这意味着让冲模完全沉入的垫板必须有足够的面积。4.3FineBlankingWell-supportedpunchesareessentialtoensurethatthedeflectioniseliminatedandthereisnoneedtostresstheconsequencesofafailuretogiveattentiontothispointinadesign.为了确保消除凸模偏转，牢固凸模很重要，没必要强调后续失误而注意该点的设计。Sharpcuttingedgesareyetanotheritemthatmustreceivecontinuedthoughtandthereisapparentlyacasehereforpunchesmadefromhigh-carbonhighchromiumsteel.锋利的剪切刃也值得注意，一个明显的例子是由高铬钢制成的凸模。4.3FineBlankingThequestionofpunchanddieclearancesisavitalpointwiththisdesignoftoolandtheyarealwaysmuchcloserthanthoseusedforconventionalblankingtools.工具设计中一个至关重要的问题（要点）是凸模和凹模间的间隙，它们比传统冲裁工具中的间隙都要小些。Asageneralguideatotalclearanceof0.01to0.03mmwillgivegoodresultsandemphasisismadeofthepointthatthesearetotalclearancesandnoteachsideofaholeorblank.通常规定，总间隙在0.01-0.03mm之间为好，需要强调的是，这里说的是总间隙而不是每一个孔或落料件的间隙。4.3FineBlankingStrippingforcestoremovetheblankfromthepuncharehigher,duetothesmallclearancesandtheloadneededtostripthematerialsestimatedasbeing10%higherthanfornormalblankingtools.由于间隙小，将落料件从凸模中脱离的脱模力较高，脱出材料所需的加载比普通冲裁工具的高出10%左右。4.3FineBlankingMethod2employstheV-shapedsurroundtoholdtheblankduringtheoperationandthisprojectionisforcedintothematerial.Fig4.2showsbrieflywhathappensasthepressdescends;theillustrationsindicatehowthepressureplateclampsthestrip,howblankingiscarriedoutandthefinalejectionofapartbythelowerejector.第二种方法采用V型凸边围绕落料件并夹紧，这样凸边压进材料中。如图4.2所示，为压力冲下时的情形，图中显示了压力板如何夹紧带钢、如何实现冲裁以及最终零件如何由下级卸料器排出。4.3FineBlanking图4-2带V形夹板的精密冲裁过程

精密冲裁中，剪切时破坏应力仅发生在凸凹刃口处，在剪切区材料只产生了变形。Anappreciationofthedifferencebetweenordinaryblankingandfineblankingisofinterest.Forexamplewhentheshearingprocesstakesplaceonanorthodoxblankingtool,thedeformationofamaterialoccursintheshearingzoneandthebreakingstressisattainedbeforethepunchhascompletelypenetratedthematerial.有必要认识普通冲裁和精密冲裁的不同。例如，用传统的冲裁工具剪切加工时，材料的变形发生在剪切区，破坏应力发生在凸模完全穿透材料之前4.3FineBlankingWordsandterms:Convergingdie收口模；wiredrawing拔丝；opendieextrusion开式模挤压；hydrostaticextrusion静液挤压；confinedchamber闭式模腔；billet坯料；isotropic各向同性；logarithmicstrain对数应变；workpiece工件；inertiaforce惯性力；adiabatic绝热的4.4FlowThroughConicalConvergingDiesThestudyofmetalflowthroughconicalconvergingdiescoverssuchprocessesaswiredrawing,open-dieextrusion,hydrostaticextrusion,andextrusionthroughaconfinedchamber.通过圆锥收口模的金属流动研究包括诸如拉丝、开式挤压、静液挤压和通过闭式模腔的挤压等工艺。4.4FlowThroughConicalConvergingDiesFig4.3representsabilletanddie.Thebilletismadeofahomogeneousisotropicmaterialofconstantstrength;considerationwillbegivenlatertovariablematerialproperties.图4.3所示为一个钢坯及模具。钢坯由等强度的各向同性材料制成，不同的材料特性将在后面分析。Inform,thebilletisacylindricalrodofradiusR0;therodisreducedtoradiusRf

byforcingittopassthroughtheconicalconvergingdie.Thereductionismeasuredfromthecross-sectionalareaofthebilletattheentrancetothedie(A0)tothatattheexit(Af).形式上，钢坯为半径R0的圆柱形棒料，将该棒料压入圆锥收口模具中，其半径变为Rf

。半径的缩小通过模具入口处(A0)到出口处(Af)的横截面积测量。4.4FlowThroughConicalConvergingDies4.4FlowThroughConicalConvergingDiesThreevariablesinvolvedinthereductionprocessarenotedatonce:(1)Reduction,whichcanbemeasuredbytheradiusratior(%)=R0/Rforarelatedexpression,namely,thearearatio(R0/Rf)2,theareareductionratio(A0-Af)/A0=1-Af/A0=1-(R0/Rf)2,thepercentagereductioninarea,ortheeffectiveorlogarithmicstrain[Φeff=2ln(R0/Rf)].在缩径过程中涉及的三个变量如下：（1）收缩量，可以用半径比R0/Rf；或者相关的表达方式面积比(R0/Rf)2；面积的缩小：(A0-Af)/A0=1-Af/A0=1-(R0/Rf)2；面积百分比的缩小或者对数应变[Φeff=2ln(R0/Rf)]来衡量。4.4FlowThroughConicalConvergingDies(2)Thesemiconeangleofthedie,α,i.e.,halfthedieangle.Inwiredrawingαisrelativelysmall,possibly6°to12°,open-dieextrusionmayemployα=60°;forextrusionthroughaclosedchamberthediemaybe“square”,withα=90°.（2）模具半锥角，是模口角的一半。在拉丝中的半锥角α相对较小，可能在6-12°；开式挤压可能采用α=60°；对于通过闭合模腔的挤压来说，模具可能是方形的，即α=90°4.4FlowThroughConicalConvergingDies(3)Frictionbetweenthedieandtherod.Wheneverthereisrelativemotionbetweentwosurfaces,thereisresistancetothismotion,andthisresistanceiscalledfriction.Themechanicsoffrictionarecomplex.（3）第三个变量为模具和坯料棒之间的摩擦。不论何时，这两个表面都存在相对运动，这种阻力成称为摩擦。摩擦机理很复杂。Althoughthefundamentalsofthephenomenonhavebeengivenmuchstudy,verylittlethatisknownwouldfacilitateformulationoftheexactfunctionalrelationshipbetweenfrictionandtheotherprocessvariables.尽管对于摩擦现象的基本原理已经进行了很多研究，但几乎没有摩擦和工艺变化量化的的精确关系。4.4FlowThroughConicalConvergingDiesThemostcommonsimplifyingassumptionsmadewithregardtothefrictionstressbetweentheworkpieceandthetoolarethefollowing:通常对于工件和工具之间的摩擦应力关系采用如下简化假定：1)Coulombfriction.Itisassumedthattheshearstressτ

isproportionaltothepressurepbetweentheworkpieceandthedie.Thenτ

=μp，wheretheproportionalityfactorμiscalledtheCoulombcoefficientoffriction,assumedconstantforagivendie,workpiece,andlubricant.（1）库伦摩擦。假定工件和模具间的剪切应力和压力成比正比。τ=μp，比例系数μ称之为库伦摩擦系数，对于给定的模具、工件和润滑剂假定为常数。4.4FlowThroughConicalConvergingDies2)Constantfriction.Itisassumedthattheshearstressisproportionaltothestrengthoftheworkpiecematerial.Then

τ

=mσ0/31/2,wheretheproportionalityfactormiscalledtheshearfactor,with0≤m≤1assumedconstantforagivendie,workpiece,andlubricant.（2）恒定摩擦。假定剪切应力与工件材料强度成正比。此时，τ=mσ0/31/2，比例系数m为剪切因子，对于给定的模具、工件和润滑剂假定0≤m≤1。4.4FlowThroughConicalConvergingDies3)hydrodynamic-hydrostatic-,andthickfilmlubrication.Whenalubricantfilmseparatestheworkpiecefromcontactwiththedie,thenhydrodynamic-orhydrostatic-filmlubricantprevails,withitsspeciallawsofshearwithinthelubricantmedium.Sometimeshighviscositylubricantsadheretotheworkpiecetoperformthickfilmseparationoftheworkpiece

fromthetool.（3）流体动力-流体静力的及厚润滑膜层。当润滑膜使工件和模具接触分离，在润滑剂介质的作用下存在专门的剪切定律，此时流体动力的或流体静力的润滑膜占据优势。有时，高粘度润滑剂黏结工件，形成厚膜将工件和工具分开。4.4FlowThroughConicalConvergingDiesThesethreeprocessvariable—reduction,coneangle,andfriction-areindependentinthattheprocessplannermaychoosetheirvaluesseparatelywithinlimits.(theseverityoffriction,forinstance,iscontrolledbychoicesoflubricant,diematerialandfinish,speed,etc.)收缩量、锥角和摩擦这三个变量相互独立，因为工艺设计者在限定范围内可能分别选择其数值，（例如，摩擦的严重程度由润滑剂的选择、模具材料和表面处理、速度等控制）。4.4FlowThroughConicalConvergingDiesTheyaretheprimaryfactorsaffectingtheprocess,andtheireffectsonthefirstdependentparameter,thedrawingorextrusionforce,willbeanalysedfirst.这些变量是影响工艺的主要因素，它们影响首要依赖的参数、拉拔或者挤压力，首先分析。Otherindependentparametersplayaroleduringprocessing.Forexample,wewillfindthatthedrawingorextrusionforceislinearlyproportionaltotheflowstrengthofthematerial,butwheninertiaforcesareneglecteditisindependentofthespeed.其他独立参数也发挥作用。例如，拉拔或挤压力与材料强度呈线性比例关系，但当忽略惯性力时，其与速度无关。4.4FlowThroughConicalConvergingDiesThepowerintheotherhandislinearlyproportionaltothespeed.Furthermore,wewillfirstconsiderisothermalprocessing,wheretemper