制造技术(中英文课件8)...ppt

Rolling 轧制 Lesson9 Rollingisaprocesswherethemetaliscompressedbetweentworotatingrollsforreducingitscross sectionalarea 1 Whatisrolling Higherproductivity lowcost Rolling 轧制 ManyshapessuchasI T Landchannelsections 槽形 方钢 squaresteel 圆钢 roundsteel 角钢 anglesteel 扁钢 flatsteel 工字钢 joiststeel Typicalrollingshapes Rolling 轧制 2 Principleofrolling Themetalistakenintorollsbyfrictionandsubsequentlycompressedtoobtainthefinalshape Schematicoftherollingprocess Thereductionthatcouldbeachievedwithagivensetofrollsisdesignatedasthe angleofbite What sthis Rollingisnormallyahotworkingprocessunlessspecificallymentionedascoldrolling Theareaofthecrosssectiongetsdecreased themetalleavingtherollswouldbeatahighervelocitythanitentered Initiallywhenthemetalenterstherolls thesurfacespeedofrollsishigherthanthatofincomingmetal whereasthemetalvelocityattheexitishigherthanthatofthesurfacespeedoftherolls So betweentheentranceandexit thevelocityofthemetaliscontinuouslychanging whereastherollvelocityremainsconstant Somewhereinthecontactlength thevelocitiesofthemetalandrollsaresamewhichisdesignatedas neutralplane Importanceoffrictionoftherollsurface 轧辊表面摩擦力的重要性 Themetalistakenintorollsbyfriction 摩擦力 andsubsequentlycompressedtoobtainthefinalshape Thethicknessofthemetalthatcanbedrawnintorollsdependontheroughnessoftherollsurface 轧辊表面的摩擦力决定所轧金属的厚度 Rougherrollswouldbeabletoachievegreaterreduction 压缩 thansmootherrolls But therollsurfaceproduceroughsurface Asetofrollsisdesignatedastheangleofbite 咬入角 Thepressureonrolls 轧辊的压力 Thepressureonrollsgraduallybuildsupfromtheentrytotheneutralpointwhereitisthehighestandthendecreasestillitreachestheexit 轧辊压力在刚进入时形成 中性点处最大 出口处最小 Theaveragerollpressurecanbedecreasedbyreducingthemaximumpressurewhichisafunctionofthecontactlength 接触长度 Smallercontactlengthsmeanlesserfrictionforcesacting 接触长度越小 摩擦力越小 Thus Thesmallerrollsareusedforlargerreductions Thesmallerrollswouldnothaveenoughrigidity 刚度 tosupportalargerollseparatingforce Backuprolls 支撑辊 Rolling 轧制 3 Rollingstandarrangement 轧辊机架的排列 Thenamesoftherollingstand 轧钢机架 arrangementsaregenerallygivenbythenumberofrollsemployed The2 highnon reversingrollingstandarrangement 两辊不可逆式轧辊机 therollsmoveinonlyonedirectionThe2 highreversingrollingstand 两辊可逆式轧辊机 reversibledrive 可逆传动 The3 highrollingstandarrangement 三辊轧机 rollingoftwocontinuouspassesinarollingsequencewithoutreversingthedrives 在轧制过程中有两个连续的道次 不存在可逆传动 Needatable tiltingarrangement 双转台 The4 highrollingstand 四辊轧机 2 highrollingmillwithsmall sizedrolls Theothertworollsarethebackuprolls 支承辊 Aclusterarrangementofrolls 密集形排布 Rolling 轧制 Planetaryrollingmill 行星轧辊机 精轧辊 支承辊 Thefinalshaperequiredcannotheobtainedinasinglepass Anumberoffreerotatingwheelsinsteadofasinglesmallroll Theintermediateshapes Aningotwhichhasacross sectionoftheorderof600 x600mm Theseingotsarefurtherprocessedinrollingmilltoproducetheintermediateshapes Blooms 大钢坯 aregenerallysquarecrosssection 正方形截面 varyingfrom150 x150mmto400 x400mm Slabs 扁钢 arerectangularcross section 矩形截面 withwidthsvaryingfrom500to1800mmandthicknessvaryingfrom50to300mm Billets 毛坯 arerectangularcross sectionswithsizesvaryingfrom40 x40mmto150 x150mm Thebloomingandslabbingmillswhichproducebloomsandslabsfromtheingotsaregenerally thereversible2 highrollingstands Themetalisturned90degintheinitialpassestoenablethematerialtoheuniformlycompressedfromallsides sothatanyoftheinternalvoidssuchasblowholesareeliminatedandtheslaginclusionsaresegregated Thefinalrolledproducts plates 钢板 flats 带材 sheets 薄板 rounds 圆钢 andsections 型钢 areobtainedinanumberofpassesstartingfrombilletsorslabs 毛坯 Therollsmaterials Therollsaregenerallymanufacturedofchilledcastiron carbonsteelandalloysteels Thesoftrollswithhardnessrangeof150to250BHNareusedinroughing 粗加工 standsoftheheavysection 厚大断面 millsandbillet 毛坯 mills Thesemihardrollswith250to400BHNareusedinroughingstandsofrailstructure 轨道结构 mills anfinishing 精加工 standsofheavysectionmillsandbilletmills Hardrollswith400to600BHNareusedtomakefinishing 精加工 standsofsheets railwaystructuresandhackingrolls 支承辊 forsmalldiameterrolls arollsurfaceofhardalloysuchastungstencarbide 碳化钨 Theextrahardrollswith600to800BHNareusedforcoldrolling Forrollingtheflat 带材 products plaincylindricalrollsareused Forgroovedrolls 凹槽辊 groovingdoneisdecidedbythefinalsectiondesired 4 Rollingpasses 辊组合孔型 Breakdownpasses 开坯孔型 Roughingpasses 粗轧孔型 Finishingpasses 精轧孔型 Thetypeoftherollpass Rolling 轧制 Draught 压缩率 Inordertodesigntherollpassschedule thefirsttobeconsideredisthedraughtorelongationineachofthepasses Rolling 轧制 Passscheduleforblooms Rolling 轧制 5 Breakdownpasses Boxpassseries 箱形孔型 usedforinitialmediumandlargesectionsofbloomingandbilletmills effectivedescaling 除锈 uniformdraughtalongthewidthofthebar Mainproblem smallerelongationDiamond squareseries 菱方系孔型 slowcoolingoftheentirematerial accuratesquaresthatarepossibleandlargerelongationsthatcanbeachieved Disadvantages therollgetsweakenedbecauseofthedeepimpressionsmadeintotherolls Oval squareseries 椭圆 方孔形 largerelongationthatcanbeobtained 1 35tol 8 comparedtotheotherbreakdownpasses Mainproblem non uniformityofthedeformationalongthewidthoftheroll Rolling 轧制 Rollingofrounds 圆钢轧制 Fig 18 9 c specialsteelsandbetterquality themainfeatureisthatallthepassesshownarewithoutanysharpcorners Fig 18 9 a passsequenceforsmallerroundsfrom5to20mm Fig 18 9 b highersizeroundsof20to100mm Fig 18 9 d specialsteels themainfeatureishandlingofmaterialintheovalpassesisdifficult 5 Rollpasssequences 孔型系统 Rolling 轧制 Atypicalsequenceofrollpassestoobtaina12mmrodfromabillet 毛坯 of100 x100mm Mainproblem thedeformationisnotuniformandalsorollwearposesaseriousproblem Rollingofsections 型钢轧制 Therollingofstructuralsectionsismoredifficultbecauseofthepresenceofflanges 翼缘 Shapeswithflangesaregenerallyrolledinclosedpasses Aclosedpass 封闭孔型 isonewherethecompleteshapeofthepassisinoneroll a Theopenpass 开口孔型 asshownistheonewherepar