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《模具专业英语 教学课件 作者 王浩钢 14456第14章.ppt》由会员上传分享，免费在线阅读，更多相关内容在应用文档-天天文库。
1、Lesson14ExtrusionExtrusionistheprocessinwhichmaterialisforcedbycompressiontoflowthroughasuitablyshapedapertureinadie,usuallytogiveaproductofasmallerbutuniformcross-sectionalarea①.Theprocesscanbecarriedoutwiththestartingmaterialatambienttemperature,i.e.coldextr
2、usion,orheatedtoatemperaturewhichgivesoptimumresultsfortheconditionsapplyingandtheproductrequirements,i.e.hotorwarmextrusion.Inmostcases,themetalisintheformofasolidorhollowcylinderandismovedinacontainingtoolinthedirectioninwhichtheproductemergesfromthedieapert
3、ure.However,therearesomevariationsonthissuchasbackward-extrusion,tubeextrusion,compoundextrusion,andsideways(lateral,transverse)extrusion.Mostmetalscanbeextrudedinonewayoranother,butobviouslysomemoreeasilythanothers.Thecommonmetalsthatcanbeextrudedatambienttem
4、peraturesarelead,aluminium,copper,lowcarbonsteelsandafewalloysofthesemetals.Thesoftersemi-preciousmetalscanalsobeextrudedcoldifrequired.HotextrusionTraditionally,inhotextrusionabilletofmetalisforcedthroughashapedholeatoneendofacontainerbytheactionofarampressin
5、gfromtheotherend.Thecontainerboreisofuniformcross-sectionandtheratioofitsareatothatoftheproductisknownastheextrusionratio.Inthemostcommonformoftheprocess,directextrusion,therammovesthroughtheboreofthecontainer,thediebeingclampedrigidlyagainsttheendofthecontain
6、er.Theextrudateexitsinthesamedirectionastherammoves.Inindirectextrusion,thedieisfittedontotheramwhichisforcedagainstthebilletheldinacontainerclosedatthefarend.Inthiscasetheextrudateleavesthediethroughthehollowram.Althoughthecontainerboreisnormallyrounditmayals
7、oberectangulartopermitextrusionofverywideproducts.Indirectextrusion,adummyblockisgenerallyinterposedbetweenthehotbilletandtheramendtominimizedamagetotheram—thedummyblockbeingacheap,easilyreplaceableitem.Forextrusionofhollowsectionsortubestheramcarriesamandrel,
8、whichservestoformtheinnersurfaceofahollowextrusionandwhichonsomepressesmaybedrivenindependentlyofthemainramtopermitpiercingofsolidbillets.Themaintoolingcomponentsforthehotextrusion
