制造技术(中英文课件8)...ppt

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1、Rolling(轧制）Lesson9Rollingisaprocesswherethemetaliscompressedbetweentworotatingrollsforreducingitscross-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)Typicalrollin

2、gshapesRolling(轧制）2.PrincipleofrollingThemetalistakenintorollsbyfrictionandsubsequentlycompressedtoobtainthefinalshape.轧辊中性面咬入角SchematicoftherollingprocessThereductionthatcouldbeachievedwithagivensetofrollsisdesignatedasthe“angleofbite”What’sthis?Rollingisnormallyahotworkingprocessunlessspecificall

3、ymentionedascoldrolling.Theareaofthecrosssectiongetsdecreased,themetalleavingtherollswouldbeatahighervelocitythanitentered.Initiallywhenthemetalenterstherolls,thesurfacespeedofrollsishigherthanthatofincomingmetal,whereasthemetalvelocityattheexitishigherthanthatofthesurfacespeedoftherolls.So,between

4、theentranceandexit,thevelocityofthemetaliscontinuouslychanging,whereastherollvelocityremainsconstant.Somewhereinthecontactlength,thevelocitiesofthemetalandrollsaresamewhichisdesignatedas“neutralplane”Importanceoffrictionoftherollsurface(轧辊表面摩擦力的重要性）Themetalistakenintorollsbyfriction(摩擦力）andsubseque

5、ntlycompressedtoobtainthefinalshape.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）Thepressur

6、eonrolls（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）.Smallercontactlengthsmeanlesserfr

7、ictionforcesacting（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.Rollingstandarran