InnovationinseamlesstuberollingtechnologyCross-rollpiercingCross-rollpiercersinnewplantsandformodernisationmeasuresMillsizesCrossrollingmillsarebuiltbySMSMeerforpiercingbilletsofdiameterapproximately100mmupto450mm.Thecorrespondingrangeofrolldiametersis720mmupto1,450mm.Thelargestcone-typepiercertodatewasbuiltwithDiescherdiscsforanMPMline.Theconsequentautomationoftheplantshowsthatevensmallbatcheswithfrequentsizechangescanbemanufacturedcost-effectivelyandwithahighproductquality.ProfitablemodernisationmeasuresSignificantbenefitsinqualityandcostsareachievedwhenoutdatedtechniquesarereplacedbythemoderncross-rollpiercingtechnology.Justtwoexamples:ModernisationofanMPMmandrelmillplantIn1999tworollingmills,apress-piercingmillandanelongator,werereplacedbyamoderncross-rollpiercerwithDiescherdiscsinanMPMmandrelmilllineintheUSA.Asaresult,thetolerancesofthetubesproducedwereimprovedsignificantlyandthesurfaceflawstypicalofthepress-piercingprocesswereeliminated.Apartfromtheimprovementsinquality,reducedtool,energyandpersonnelcostshaveconfirmedthesuccessoftheinvestment.Upgradingofapush-benchplanttoaCPEplantIn1998,thefourthconventionalpush-benchplantwasconvertedintoamodernCPEplantbyreplac-ingthepiercingpresswithamoderncross-rollpier-cer.Theresultsare:•Increaseinthebilletweightfrom500kgto635kg•Increaseintheshelllengthfrom17mto22mwithconsequentlyincreasedlengthofthefinishedtubes•Reductioninthecropendlosses•Improvementinthewallthicknesstolerances•Eliminationofthreeformingstepsincludingtoolandmaintenancecosts•CostreductionsthroughreducedpersonnelrequirementsTheincreasesinbilletweightandshelllengthtogetherwiththereducedcropendlossesduetocrimpinghaveresultedinasignificantimprovementintheyieldoftheplant.Thankstothismodernisa-tionmeasure,themillownerhasconsiderablystrengthenedhiscompetitiveposition.Barrel-typepiercerinaCPEplantCone-typepiercer,run-outsidewith3-rollerguidesCone-typepiercerinanMPMplantNewtechnologyforseamlesstubeproductionNewplantconceptsThehigherperformanceofthecross-rollpiercerwithrespecttoelongationanddiameterexpan-sionordimensionalflexibilityachievedthroughrecenttechnologydevelopmentisusedtoreduceinvestmentandproductioncostsinthemainelongationstage.Thisisachievedbyshiftingtheformingtobeperformedintheseamlesstubeproductionlinefromthesecondstage,themainelongationstage,tothefirststage,thepiercingstage.Thepossibilitiesfornewplantconceptsrequiringlowerinvestmentcostsandsuitableforsmallerproductioncapacitieshavethusbeenopenedup.OneexampleofthisisanMPMmandrelmillinwhichthecone-typepiercer,4-standmandrelmillandstretch-reducingmillarecombined.Theplantproducestubesinthesizerangefrom33to168mmwithanannualcapacityof75,000t.QualityboostthroughprocesscontrolSourcesoffaultsThefollowingdimensionaldeviationscanoccuronthepiercedbilletproducedonthecross-rollpiercer:Deviationsinmeandiameterandmeanwallthicknessarecausedbychangesinfriction,temperature,etc.Largergeometricaldeviationscanbetracedbacktooperatorerrors,incorrecttools,etc.Causesofdeviationsinthelocalwallthicknessesinthecross-sectionofthepiercedbilletcanbe:Positiondevia-tionsoftherolls,plugorguides,toolwear,crookedplugbars,uneventemperaturedistributioninthebillet,errorsinposition,functionandtemporalcontrolofthethreerollerguidesintheoutletsection,crooked-nessofthebilletanditscutsurfaceandagreatmanymore.Thedifferentcausesgenerallyhaveachara...
