SMS Meer 穿孔机介绍.pdf

Innovation in seamless tube rolling technologyCross-roll piercingCross-roll piercers in new plants and for modernisation measuresMill sizesC ross rolling mills are built by SMS Meer for pierc i n gbillets of diameter approximately 100 mm up to450 mm.The corresponding range of roll diametersis 720 mm up to 1,450 mm.The largest cone-typepiercer to date was built with Diescher discs for anMPM line.The consequent automation of the plantshows that even small batches with frequent sizechanges can be manufactured cost-effectively andwith a high product quality.Profitable modernisation measuresSignificant benefits in quality and costs are achievedwhen outdated techniques are replaced by themodern cross-roll piercing technology.Just twoexamples:Modernisation of an MPM mandrel mill plantIn 1999 two rolling mills,a press-piercing mill andan elongator,were replaced by a modern cross-rollpiercer with Diescher discs in an MPM mandrel millline in the USA.As a result,the tolerances of thetubes produced were improved significantly and thesurface flaws typical of the press-piercing processwere eliminated.Apart from the improvements inquality,reduced tool,energy and personnel costshave confirmed the success of the investment.Upgrading of a push-bench plant to a CPE plantIn 1998,the fourth conventional push-bench plantwas converted into a modern CPE plant by replac-ing the piercing press with a modern cross-roll pier-cer.The results are:Increase in the billet weight from 500 kg to635 kg Increase in the shell length from 17 m to 22 mwith consequently increased length of the finishedtubes Reduction in the crop end losses Improvement in the wall thickness tolerances Elimination of three forming steps including tool and maintenance costs Cost reductions through reduced personnelrequirementsThe increases in billet weight and shell lengthtogether with the reduced crop end losses due tocrimping have resulted in a significant improvementin the yield of the plant.Thanks to this modernisa-tion measure,the mill owner has considerablystrengthened his competitive position.Barrel-type piercer in a CPE plantCone-type piercer,run-out side with 3-roller guidesCone-type piercer in an MPM plantNew technology for seamless tube productionNew plant conceptsThe higher performance of the cross-roll piercerwith respect to elongation and diameter expan-sion or dimensional flexibility achieved throughrecent technology development is used to reduceinvestment and production costs in the mainelongation stage.This is achieved by shifting theforming to be performed in the seamless tubeproduction line from the second stage,the mainelongation stage,to the first stage,the piercingstage.The possibilities for new plant conceptsrequiring lower investment costs and suitable forsmaller production capacities have thus beenopened up.One example of this is anMPM mandrel mill in which the cone-type piercer,4-stand mandrel mill andstretch-reducing mill are combined.The plant produces tubes in the sizerange from 33 to 168 mm with anannual capacity of 75,000 t.Quality boost through process controlSources of faultsThe following dimensional deviations can occur onthe pierced billet produced on the cross-roll piercer:Deviations in mean diameter and mean wall thicknessare caused by changes in friction,temperature,etc.Larger geometrical deviations can be traced back tooperator errors,incorrect tools,etc.Causes ofdeviations in the local wall thicknesses in the cross-section of the pierced billet can be:Position devia-tions of the rolls,plug or guides,tool wear,crookedplug bars,uneven temperature distribution in thebillet,errors in position,function and temporal contro lof the three roller guides in the outlet section,c ro o k e d-ness of the billet and its cut surface and a gre a tmany more.The diff e rent causes generally have acharacteristic effect and can thus be detected fromthe different measurement data using appropriateanalysis methods.Metrology,the basis for process controlOutside diameter and length of the pierced billet pro-duced in the cross-roll piercer are measured imme-diately behind the mill.The mean wall thickness iscalculated.Furthermore,temperature and rolling timeare measured.These values are compared with thenominal values and,if necessary,a warning is given.For a detailed examination of the product quality,measuring systems are employed at appropriatepoints in the production plant which measure the wallthickness in the cross-section of the rolling stock.A wall thickness measuring device employing the radia-tion principle cannot be positioned directly behind thecross-roll piercer due to the plug bar inside thepierced billet during the longitudinal transport.If it isemployed behind the main elongation unit,however,statements can be derived as to the product qualityor faults generated in the cross-roll piercer usingsuitable evaluation methods(e.g.Fourier analysis).With the LASUS wall thickness measuring systemavailable today which employs ultrasonic waves,thewall thickness of the pierced billet can be measuredimmediately behind the cross-roll piercer.The causesof avoidable wall thickness deviations can now bedetermined directly and eliminated.This createsimproved possibilities for a controlled rolling processwith a high standard of quality.a)b)Presentation of wall thickness measurement data(a:screw effect,b:better quality)User interface of the technology systemMean eccentricity valuesTechnology and process control systemThe technology system developed by SMS Meerprovides the tools,the computation methods andthe know-how for the work in the technology areaand on the mill necessary for optimising produc-tion.Using this system,optimised mill settings and piercer plug geometries can be calculated.At the technology terminal,rolling programme and tool data are generated and optimised usingthe feedback from the production.The stored data are available to the tool shop and the mill.The operator at the control stand of the cross-rollpiercer uses the technology system for ongoingprocess optimisation.In the event of deviations inthe nominal dimensions of the pierced billet,a new optimised setting is calculated quickly,easilyand reliably with its help.If avoidable local wallthickness deviations occur,the system provideshints as to the causes of the faults and their remedies through measurement data analysis.The benefit of the use of this system lies in the drastic reduction in the wall thickness deviations by establishing a controlled rolling process:Operator errors are prevented,problems arequickly detected and correctly interpreted,the measures necessary to solve the problems arequickly and reliably implemented.Result:higher wall thickness precisionOne of the most important quality features on thec ro s s-roll piercer is the eccentricity of the pierc e dbillet,as this type of wall thickness deviation canbe influenced to only a very limited extent in thef u rther forming steps.The figure below shows themean eccentricity values asa function of the wall thick-ness from a stable,con-t rolled production pro c e s s.These values were re c o rd e dby an automatic measuringand re c o rding systembehind the main elongationstage and plotted over thep i e rced billet thickness pro-duced in the cro s s-roll pierc e r.The values shown exhibit mean deviations in thewall thickness of around 0.22 mm with a scatterband of 0.05 mm.Without process control,de-viations of twice this size generally have to be ex-pected,corresponding to a few percentage pointsin the potential for improved yield.Furt h e rm o re,operator errors and undetected rolling faults usuallylead to losses due to excessive eccentricities ofbetween 0.5%and 1%.This is an additional po-tential for saving losses by process contro l.Pierced billet wall thickness mmsminsmaxEccentricity:e=smax-smin2Piercer types and working rangesDifferent choicesDepending on the cone angle a,a distinction ismade between cone-type and barrel-type piercers.Both types can be equipped either with guide shoesor Diescher discs for guiding the rolling stock be-tween the rolls.Guide shoes permit better guidancefor sizing while Diescher discs involve lower costsduring production and increase the mill throughput.With increasing angle a,the relative velocities betweenroll and rolling stock change so that the elongatingeffect is increased.The different forming behaviourof the two mill types is reflected in the very differentworking ranges with respect to elongation,diameterexpansion and diameter-to-wall thickness ratio of thep i e rced billet.Another piercer type is the thre e-ro l lp i e rcing mill with certain advantages in rolling criticalm a t e r i a l s.a)Conical rolls,Diescher discb)Barrel rolls,guide shoeWorking ranges of cone-type and barrel-type piercersDiameter-to-wall thickness ratioElongationBarrel-type piercerCone-type piercerThe cross-rolling processEssentials of cross-rollingDuring cross-rolling,rolls with a double conical p rofile are used which rotate in the same dire c t i o nand which are inclined relative to the mill center-line by the feed angle g and the cone angle a.The forming process encompasses diameterreduction,piercing,a wall thickness reduction anda diameter increase.The size of the feed angle isthe primary determining factor for the materialt h roughput and the number of rotations of the rolling stock.The size of the cone angle deter-mines the additional axial forces and the increasein diameter in the run-out section.Material strain,i.e.processability of even critical materials andp roduct quality,in particular the wall thicknesstolerances,can be optimised by an appro p r i a t echoice of the angles and tool sizing.The stress state created during the diameterreduction of the billet ensures a tensile stress infront of the piercer plug and a centering of thep i e rcer plug in the middle of the billet cro s s-section.This centering effect is the primary factorfor the creation of a uniform wall thickness in thepierced billet cross-section.The negative effect ofthe tensile stresses(reeling effect)is essentiallysuppressed by appropriate sizing and positioningof the piercer plug.Roll arrangementAxial stresses in the billet cross sectionCone angle aFeed anglegCompressive stressCompressive stressRollRollTensile stressSMS Meer GmbHOhlerkirchweg 66.41069 MnchengladbachP.O.Box 100645.41006 MnchengladbachGermanyPhone([phone].Fax[phone]e-mail:infosms-.http:/www.sms-