PartIII-chapter-13

PARTIIIFormingandShapingProcessesandEquipment第二篇：压力成型工艺与设备,张新房,Takeforgranted:想当然comeacross:不期而遇、stapler:订书机pipewrench:管钳子lightfixture:电灯器具aluminumfoil:铝箔plasticfilm:塑料薄膜,electrical-resistancewirefortoaster:电阻丝的烤面包机,hull:外壳boilerplate:锅炉钢板smoothcurvature:平滑的曲率bicyclehandle:自行车把手ballbearing:球轴承cookingpot:烹饪器具configuration:构造detailedsurfacefuture:精细的表面特征coin:硬币silverware:银器engineblock:发动机组，气缸体,connectingrod:连杆elevatorcable：升降机控制锁paperclip:纸夹slab:板坯convert:归结wrough:锻造的pellet:球flake:片clay:粘土Body:坯体,workpiece:工件stock：坯料blank:板坯sheet:薄板bar:棒材rod:长杆tubing:管材coathanger:金属衣架translucent:半透明的Formingprocess:锻压工艺,FigIII.1Formedandshapedpartsinatypicalautomobile,Ceranicsparkplug:陶瓷火花塞powder-metalfilter:粉末金属过滤器forgedvalve:锻造阀门windshield:挡风玻璃dashboard:仪表盘drawntubeforantenna:制定管天线cold-rolledsheetmetalorreinforcedplasticforbody:车体冷轧薄板或强化塑料stampedlicenseplate:车牌安装处injection-moldedtaillighttense:注塑尾灯紧固件,fueltank:油箱compression-moldedtire:压缩成型轮胎spring:弹簧blow-moldedwindshield:吹塑挡风玻璃washerfluidtank:清洗液箱stampedoilpan:冲压油盘stampedwheelcover:冲压车轮盖.,Shapingprocessesusuallyinvolvemolding(造型)andcasting.Theresultingproductsisusuallyatornearthefinaldesiredshapeandmayrequirelittleornofurtherfinishing.Discrete:不连续的Machinery:机械,Animportantconsiderationistheworkabilityandformabilityofmaterials,meaningthemaximumamountofdeformationamaterialcanwithstandinaparticularformingandshapingprocesswithoutfailure.材料的可加工性和可成型性是该过程中一个重要的考虑因素，意为这在一个特定的压力成型工艺中可以承受，而不失效的材料最大变形量。Workabilitycorrespondstocompressiveforce,whileformabilitycorrespondstotensileforceappliedontherawmaterials.Stamping:模印stretchforming:拉伸成型,Chapter13RollingofMetals第十三章金属轧制,13.1Introduction简介13.2flatRolling平板轧制13.3RollingMills轧机13.4FlatRollingPractice平板轧制的应用13.5Shape-RollingOperations成形轧制工艺13.6ProductionofSeamlessPipeandTubing无缝管和管件的生产13.7ContinuousCastingandRolling连续铸造与轧制,13.1Introduction,Rollingistheprocessofreducingthethickness(orchangingthecross-section)ofaworkpiecebycompressiveforcesappliedthroughasetofrolls(Fig.13.1);theprocessissimilartotherollingofdoughwitharollingpintoreduceitsthickness.Rolling,whichaccountsorabout90%ofallmetalsproducedbymetalworkingprocesses,wasfirstdevelopedinthelate1500s.thebasicoperationisflatrolling,orsimplyrolling,wheretherolledproductsareflatplaneandsheet.轧制是一种通过一组轧辊对长的工件施加压力，从而减小其厚度（或改变其横截面积）的工艺；这一工艺类似于用擀面杖滚压生面团以减小面团的厚度。轧制工艺最早在16世纪后期发展起来，现在的金属加工工艺制作的所有材料中，约有90%要用到轧制。轧制的基本操作室平板轧制，即简单轧制，产品是平板和薄片。,skelp:制管板材hotrolledbar:热轧棒材colddrawn:冷拉rod:圆棒tuberound:圆管坯seamlesspipe:无缝管材,Slab:平板坯billet:钢条，方钢坯bloom:大方坯hotstrip:热轧钢带,pickling:酸洗oiling:油洗coldstrip:冷轧,Plates,whicharegenerallyregardedashavingathicknessgreaterthan6mm,areusedforstructuralapplications,suchasmachinestructures,shiphulls,boilers,bridgesandnuclearvessels.Platescanbeasmuchas0.3m(12in.)thickforthesupportsforlargeboilers,150mm(6in.)forareactorvessels,and100-125mmthickforbattleshshipsandtanks.平板通常是指厚度大于6mm的板材，用于一些结构上，如机器结构件、船体、锅炉、桥梁和核反应容器等。厚度达0.3m的板材（12in.）用来做大锅炉的支撑；而150mm（6in.）厚的板可用来做反应器容器；100-125mm厚的板可用在战舰和坦克上。,Sheetsaregenerallylessthan6mmthick;theyareprovidedtomanufacturingfacilitiesasflatpiecesorasstripincoilsforfurtherprocessingintovariousproducts.Theyareusedforautomobileandaircraftbodies,appliances,foodandbeveragescontainers,andkitchenandofficeequipment.薄板厚度通常小于6mm；它们以平板或卷料的形式提供给制造者，以进一步加工成各种产品。薄板可用在汽车和飞行器的壳体、家用器具、食品和饮料的容器，以及厨房和办公设备。,Commercialaircraftfuselagesareusuallymadeofaminimumof1mm(0.040in.)thickaluminumalloysheet.Forexample,theskinthicknessofaBoeing747is1.8mm;thatofaLockheedL1011is1.9mm.Aluminumbeveragecansarenowmadefromsheets0.28mmthick,whicharereducedtoafinalcanwallthicknessof0.1mm.Aluminumfoil,typicallyusedtowrapcandyandcigarettes,hasathicknessof0.008mm.商用飞行器机身一般用不小于1mm（0.04in.）厚的铝合金薄板制成。例如，波音747的蒙皮厚1.8mm；洛克希德L1011的蒙皮厚1.9mm。铝饮料罐目前用0.28mm厚的薄板制作，其最后成形的罐壁厚度减小到0.1mm。铝箔一般用于包装糖果和香烟，其厚度为0.008mm。,Thischapterdescribesthebasicprocessofflatrollingandshaperollingoperations,theproductionofseamlesstubingandpipe,andtheimportantfactorsinvolvedinrollingpractices.Traditionally,theinitialmaterialsformforfillingisaningot.AsstatedinSection5.4,however,thispracticeisnowbeingrapidlyreplacedbythatofcontinuouscastingandrolling,atmuchhigherefficiencyandalowercost.本章介绍平板轧制和成形轧制的基本工艺、无缝钢管和管件的生产，以及影响轧制的重要参数。传统上，轧制的原始坯料是钢锭。但是，如5.4节中所述，目前这一工艺正在迅速地被连铸连轧所取代，后者具有更高的效率，而且成本更低。,Rollingisfirstcarriedoutatelevatedtemperature(hotrolling);duringthisphase,thecoarse-grained,brittle,andporousstructureofingotorthecontinuouslycastmetalisbrokendownintoawroughtstructurehavingfinergrainsizeandenhancedproperties.轧制先在高温下进行(热轧)；在此阶段，钢锭或连续铸造金属的粗大晶粒、脆性和多空结构被打碎称为具有更小的晶粒尺寸和更好性能的锻造组织。,13.2FlatRolling平板轧制,AschematicillustrationoftheflatrollingprocessisshowninFig.13.2a.Astripofthicknessh0enterstherollgapandisreducedtothicknesshfbyapairofrotationrolls,eachrollbeingpoweredthroughitsshaftbyelectricmotors.ThesurfacespeedoftherollsisVr.Thevelocityofthestripincreasesfromitsentryvalue,Vo,asitmovesthroughtherollgap,inthesamewayfluidmustflowfasterasitmovesthroughaconvergingchannel.平板轧制工艺如图13.2a所示。厚度为h0的条料进入轧辊间隙并被一对旋转轧辊减厚到hf，轧辊有电动机通过周驱动。轧辊表面线速度是Vr。当条料通过轧辊间隙时，其进入时的初速度是V0，然后开始增加，这与当流体流经收敛的渠道时流速加快是同样的道理。,Fig.13.2(a)Schematicillustrationoftheflat-rollingprocess.(b)Frictionforcesactingonstripsurfaces.(c)Therollforce,F,andthetorqueactionontherolls.Thewidthwofthestripusuallyincreasesduringrolling,asshowninFig.13.5,Thevelocityofthestripishighestattheexitformtherollgap;wedenoteitasVfthere.Becausethesurfacespeedoftherollisconstant,thereisrelativeslidingbetweentherollandthestripalongthearcofthecontactintherollgap,L.条料在离开轧辊间隙时的速度最大，用Vf来表示。因为轧辊的表面速度恒定，所以在轧辊间隙处，轧辊和条料之间沿接触弧上有相对滑动。Neutral:中性的,no-slip:无滑动,13.2.1FrictionalForces摩擦力,Therollspullthematerialintotherollgapthroughanetfrictionalforceonthematerial.ItcanbeseenthatthisnetfrictionalforcemustbetotherightinFig.13.2b;consequently,thefrictionalforcetotheleftoftheneutralpointmustbehigherthanthefrictionforcetotheright.轧辊通过与材料表面的净摩擦力把材料拉入轧辊间隙。从图13.2b可见它必在右侧；因此中性点左侧的摩擦力要大于右侧的摩擦力。Netfrictionalforce:净摩擦力dissipate:散失compromise:折中、妥协,(13.1)Thus,thehigherthefrictionandthelargertherollradius,thegreaterthemaximumpossibledraft(andreductioninthickness)becomes.因此，摩擦力和轧辊半径越大，最大减面率（减厚）也就越大。Tread:胎纹,tractor:拖拉机,off-road:越野,terrain:地带,skid:打滑,Themaximumpossibledraft:减面率，压下量,definedasthedifferencebetweentheinitialandfinalthickness,(ho-hf),isafunctionofthecoefficientoffriction,andtherollradius,R.最大可能的减面率，被定义为轧制前后厚度差(ho-hf)，它是摩擦系数u和轧辊半径R的函数：,13.2.3RollForceandPowerRequirement轧制力和动力要求,Perpendicular:垂直于,alignment:近似、校准Therollforceinflatrollingcanbeestimatedfromtheformula:,(13.2)WhereListheroll-stripcontactlength,wisthewidthofthestrip,Yavgistheaveragetruestressofthestripintherollgap.Forfrictionlesssituation,sothehigherthecoefficientoffrictionbetweentherollsandthestrip,thegreaterbecomesthedivergence(偏离),andtheformulapredictsalowerrollforcethantheactualforce.,ThepowerrequiredperrollcanbeestimatedbyassumingthattheforceFactsinthemiddleofthearcofcontact:InFig.13.2c,a=L/2.Torque(扭矩)perrollistheproductofFanda.Therefore,thepowerperrollinS.I.unitsis:,(13.3),ReducingRollForce:Rollforcecancausedeflection(挠曲，变位)andflattening(压扁)oftherolls;suchchangeswill,inturn,adverselyaffecttherollingoperation.Also,therollstand(轧钢机架),includingthehousing(箱),chocks(轮挡、楔子),andbearings(轴承),maystretch(拉伸)undertherollforcestosuchanextentthattherollgapcanopenupsignificantly.Consequently,therollshavetobesetcloserThantwascalculated,tocompensateforthisdeflectionandtoobtainthedesiredfinalthickness.,Fig.13.3Schematicillustrationofafour-highrolling-millstand,showingitsvariousfeatures.Thestiffnessesofthehousing,therolls,andtherollbearingsareallimportantincontrollingandmaintainingthethicknessoftherolledstrip.,制动器,Rollforcescanbereducedbyanyofthefollowingmeans:a.reducingfrictionb.usingsmall-diameterrolls,toreducethecontactarea;c.takingsmallerreductionsperpass,toreducethecontactarea;andd.rollingatelevatedtemperatures,tolowerthestrengthofthematerial.Andtoapplylongitudinaltensionstothestripduringrolling.Tensionscanbeappliedtothestripeitherattheentryzone(backtension)orattheexitzone(fronttension)orboth.Back-uproll:支撑轧辊,screw:螺钉,hydraulic:水压的Steckelrolling:斯特克尔轧制法，炉卷轧机，如图一所示。,13.2.3GeometricConsiderations几何考虑,Transverse:横向的Thehighertheelasticmodulusoftherollmaterials,thesmallertherolldeflection.Asaresultofrollbending,therolledstriptendstobethicker(haveacrown:隆起)atiscenterthanatitsedge.Theusualmethodofavoidingthisproblemistogrindtherollssothattheirdiameteratthecenterisslightlylargerthanattheiredges(camber:凸度).,Theradiusofthemaximumcamberpointisgenerally0.25mmgreaterthanthatattheedges.Plasticdeformationinducesheatleadingslightlybarrel-shaped:桶形(thermalcamber),sothetotal(orfinal)cambercanbecontrolledbyvaryingthelocationofthecoolantontherollsduringhotrolling.Flatteningtherollbyrollingforceproducesalargerrollradiusandhence,alargercontactareaforthesamedraft.Therollforce,inturn,increaseswithincreasedflattening(扁度）.,Fig.13.4(a)Bendingofstraightcylindricalrolls.Causedbytherollforce.(b)Bendingofrollsgroundwithcamber,producingastripwithuniformthickness.,Spreading:Theincreaseinwidthduringrollingiscalledspreading(延展).Itincreaseswithadecreaseinthewidth-to-thicknessratiooftheenteringmaterials(becauseofreductioninthewidthconstraint:约束),withanincreaseinthefriction,andwithadecreaseintherationoftherollsradiustothestripsthickness(thelattertwobeingduetoincreasedlongitudinalconstraintofthematerialflowintherollgap).Spreadingcanbepreventedbytheuseofverticalrollsincontactwiththeedgesoftherolledproduct(asedgermills:立辊轧机).随着进料的宽度-厚度比的减小（由于宽度上约束的减小）、摩擦力的增加，以及轧辊半径与条料厚度比的减小（后二者是由于材料在这个间隙中纵向流动约束的增加），材料的展宽就增加。利用与轧件边缘接触的垂直轧辊（如立辊轧机）可以防止展宽。,Fig.13.5Increaseinthewidth(spreading)ofastripinflatrolling(seealsoFig.13.2a).Similarly,spreadingcanbeobservedwhendoughisrolledwitharollingpin.,13.3FLAT-ROLLINGPRACTICE平板轧制的应用,Hotrolling:Hotrolling(abovetherecrystallizationtemperatureofthemetal)canenhancethemechanicalpropertiesbyrefininggrains,breakingupofbrittlegrainboundariesandtheclosingupofinternaldefectsofthecastslab(板坯).Temperaturerangesforhotrollingaretypicallyabout450oCforaluminumalloys,upto1250oCforalloysteels,andupto1650oCforrefractoryalloys.,Fig.13.6Changesinthegrainstructureofcastorlflarge-grainwroughtmetalduringhotrolling.Hotrollingisaneffectivewaytoreducegrainsizeinmetals,forimprovedstrengthandductility.Caststructuresofingotsorcontinuouscastingsareconvertedtoawroughtstructurebyhotrolling.,平整轧制,Fig.13.7Amethodofrollerlevelingtoflattenrolledsheets.,Bloom(初轧方坯)orslab(初轧板坯),firsthot-rollingoperation.Bloomwithsquare(正方形)cross-section,atleast150mmontheside,whichcanbeprocessedfurther,byshaperolling,intostructuralshapes,suchasI-beamsandrailroadrails;aslabisusuallyrectangular(矩形)incross-section,furtherrolledintoplaneandsheet.Billets(方钢坯)areusuallysquare,withacross-sectionalsmallerthanblooms;theyarelaterrolledintovariousshapes,suchasroundrodsandbars,bytheuseofshapedrolls.Wiredrawing:拉丝,wirerods:线材.,Conditioning(预处理）isdonebyvariousmeans,suchastheuseofatorch:吹焰器(scarfing：火焰表面清理)toremoveheavyscale（氧化皮）orofroughgrindingtosmoothensurface.Acidetching:酸洗Coldrolling(冷轧)iscarriedoutatroomtemperatureand,comparedtohotrolling,producessheetandstripwithmuchbettersurfacefinish,dimensionaltolerances,andmechanicalproperties.,Packrolling(叠板轧制)isaflat-rollingoperationinwhichtowofmorelayerofmetalarerolledtogether;thisprocessimprovesproductivity.Matte:无光泽的，shiny:有光泽的。,13.3.1DefectsinRolledPlatesandSheets轧制板材和薄板中的缺陷,Defectsmaybepresentonthesurfaceorinternalstructuraldefects,leadingtothedecreasedsurfaceandmechanicalpropertiesandothercharacteristics.,Surfacedefects,scale(氧化皮，鳞皮),rust(锈),scratches(划痕),gouges(圆凿、半圆凿、弧口凿),pits(凹坑),cracks,etc.on,maybecausedbyinclusions(夹杂物)animpuritiesintheoriginalcastmaterialorbyvariousotherconditionsrelatedtomaterialpreparationandtotherollingoperation.,Wavyedges(波状边)onsheetsaretheresultofrollbending(轧辊挠度).Thestripinthinneralongitsedgethanatitscenter;becausetheedgeselongatemorethanthecenter,theybuckle(翘曲),becausetheyarerestrainedfromexpandingfreelyinthelongitudinal(rolling)direction.ThecracksshowninFigs.13.8bandcareusuallytheresultofpoormaterialductilityattherollingtemperature.,Alligatoring(皱裂)isacomplexphenomenonandmaybecausedbynonuniformdeformationduringrollingorbythepresenceofdefectsintheoriginalcastbillet(钢坯).Theedgedefectsinrolledsheetsareoftenremovedbyshearing(剪切)andslitting(纵剪)operations.,Fig.13.8Schematicillustrationoftypicaldefectsinflatrolling:(a)wavyedges;(b)zippercracksinthecenterofthestrip;(c)edgecracks;and(d)alligatoring.,13.3.2OtherCharacteristics其它特点,Residualstress(残余应力)resultsfromnonuniformdeformationforrolledplateandsheet.Forsmall-diameterrollsorsmallreductionperpass,compressiveresidualstressonthesurfaceandtensilestressinthemiddle.Large-diameterrollsandhighreductionstendtodeformthebulkmorethanthesurface,producingtensileresidualstressonthesurfaceandcompressivestressinthemiddle.,Fig.13.9(a)Residualstressesdevelopedinrollingwithsmallrollsoratsmallreductionsinthicknessperpass.(b)Residualstressesdevelopedinrollingwithlargerollsorathighreductionsperpass.Notethereversaloftheresidualstresspatterns.,Dimensionaltolerance(尺寸公差).0.1mmto0.35mmforthicknesstoleranceundercold-rolledsheet.Flatnesstolerances(平面度公差)areusuallywithin15mm/mforcoldrollingand55mm/mforhotrolling.SurfaceRoughness(表面粗糙度),seenintheFig.11.12forhotandcoldrolling.,Gagenumbers(规数).Thethicknessofasheetisusuallyidentifiedbyagagenumber.Thesmallerthenumber,thethickerthesheet.Rolledsheetsofcopperandbrassarealsoidentifiedbythicknesschangesduringrolling,suchas1/4hard,1/2hard,andsoon.,13.4ROLLINGMILLS轧机,Thedesign,construction,anoperationofrollingmillsrequiremajorinvestments.Highlyautomatedmillsproduceclose-tolerance,high-qualityplatesandsheetathighproductionratesandlowcostperunitweight,particularlywhenintegratedwithcontinuouscasting.Thewidthofrolledproductsmayrangeupto5mandbeasthinas0.0025mm.rollingspeedsmayrangeupto25m/sforcoldrolling,orevenhigherinhighlyautomatedandcomputer-controlledfacilities.,Two-high（二次）orthree-high（三次）rollingmillsareusedforhotrollingforinitialbreakdown(初次开坯)passes(轧道道次)(primaryroughing:粗轧orcoggingmills:初轧机)oncastingotsorincontinuouscasting,withrolldiametersrangingfrom0.6mto1.4m.Inthethree-highorreversingmill(可逆式轧机),thedirectionofmaterialmovementisreversedaftereachpass.,Fig.13.10Ageneralviewofarollingmill.,Four-highmillsandclustermills(多辊式轧机)(SendzimirofZmill)arebasedontheprinciplethatsmall-diameterrollslowerrollforcesandpowerrequirementsandreducingspreading.AlthoughthecostofSendzimirmillfacilitycanbemillionsofdollars,itisparticularlysuitableforcoldrollingthinsheetofhighstrengthmetals.Commonrolledwidthsare0.66m,withamaximumof1.5m.,Fig.13.11Schematicillustrationofvariousrollarrangements:(a)two-high;(b)threehigh;(c)four-high;(d)cluster(Sendzimir)mill.,backingbearing:支撑轴承,bearingshaft:轴承轴,intermediateroll:中间辊,Intandemrolling(交叉轧制，连轧),thestripisrolledcontinuously,throughanumberstands,tosmallergageswitheachpass.Electronicandcomputercontrols,alongwithextensivehydraulic(液压)controlsareusedintandemrollingoperations.Rolls.Strengthandresistancetowear,commonmaterialsforrollarecastiron,caststeel,andforgedsteel(锻钢).,Tungstencarbides(碳化钨)arealsousedforsmall-diameterrolls.Forgedsteelrolls,althoughmorecostly,havegreaterstrength,stiffness(刚度)thancastironrolls.Rollsforcoldrollingaregroundtoafinefinish;forspecialapplications,theyarepolished.Replica:复制品，仿制品Rollsmadeforcoldrollingshouldnotbeusedforhotrolling,becausetheymaycrackforthermalcyclingandspalling(自发破裂，剥落,flaking).,Lubricants.Hotrollingofferrousalloysisusuallycarriedoutwithlubricants,althoughgraphitemaybeused.Water-basedsolutionsareusedtocooltherollsandtobreakupthescaleontherolledmaterial.Nonferrousalloysarehotrolledwithaverityofcompoundedoils(复合油),emulsions(乳化液),andfattyacids(脂肪酸).Coldrolling,water-solubleoilorlow-viscositylubricants,suchasmineraloils,emulsions,paraffin(石蜡),andfattyoils.,Arandemhot-rollingmill,Fig.13.12Atandemrollingoperation,13.5SHAPE-ROLLINGOPERATIONS成形轧制工艺,Becausethematerialscross-sectionistobereducednon-uniformly,thedesignofaseriesofrolls(roll-passdesign:轧辊型缝设计)requiresconsiderableexperienceinordertoavoidexternalandinternaldefects,toholddimensionaltolerances,andtoreducerollwear.由于材料横截面的缩减是不均匀的，因此，为了避免内部和外部缺陷，控制公差和减小轧辊的磨损，在设计这一系列轧辊（轧辊型缝的设计）时，需要相当多的经验。,13.5.1RingRolling环轧制,Inthering-rollingprocess,athickringisexpandedintoalargediameterringwithreducedcross-section.Thering-shapedblank(坯件)maybeproducedbysuchmeansasbycuttingfromaplate,bypiercing(冲孔),orbycuttingathick-walledpipes.,Fig.13.13StagesintheshaperollingoranH-sectionpart.Variousotherstructuralsections,suchaschannelsandI-beams,arealsorolledbythiskindofprocess.,Roundingroll:倒圆辊edlerroll:导辊edgingroll:边辊,Typicalapplication:largeringsforrocketsandturbines,gearwheelrims(齿轮环),ball-bearing(球轴承)androller-bearing(滚针轴承)races(轴承环),flanges(凸圆盘，法兰),andreinforingringsforpipes.Processingconditions:roomorevaluatedtemperature,dependingonthesize,strength,andductilityoftheworkpiecematerial.Advantages:shortproductiontimes,materialssavings,closedimensionaltolerances,andfavorablegrianflowintheproduct.,Apictureshowingtheringrollingprocess,Fig.13.14(a)Schematicillustrationofaring-rollingoperation.Thicknessreductionresultsinanincreaseinthepartdiameter.(b)Examplesofcross-sectionsthatcanbeformedbyring-rolling,13.5.2ThreadRolling滚丝,Thethread-rollingprocessisacold-formingprocessbywhichstraightortapered(锥形的)threads(螺纹)areformedonroundrods,bypassingthembetweendies.ThreadRollingprocessisusedformakingexternalthreads.Adie,whichisahardenedtoolwiththethreadprofile,ispressedontoarotatingworkpiece.Astheforceisgraduallyincreased,thethreadprofileistransferredtotheworkpiece.Thisprocessproducesscrewswithgreaterstrengththanmachinedthreadsduetothecoldworking,aswellasbettermaterialyield.Advantages:nowasteofmaterial,goodstrength,goodsurfacefinish,improvedfatiguelige.Spur(正齿轮)andhelicalgears(螺旋齿轮)canbeproducedbycold-rollingprocessessimilartothreadrolling.Theprocessmaybecarriedoutonsolidcylindricalblanksoronprecautgears.Coldrollingofgearshasextensiveapplicationsinautomatictransissionsandinpowertools.Internalthreadrollingusedwithaflutelessfomingtap(无槽成形丝锥),goodstrength.,Fig.13.15Thread-rollingprocesses:(a)andreciprocati