Profile And Flatness Control Of Electrical Steel For Schedule-free Rolling In New Generation Hot Strip Mills

Electrical steel is a kind of ferrosilicon soft magnetic alloy with high efficiency,energy saving and low carbon content,which is the key material for national defence and military project.Electrical steel can also support national electromechanical industry and energy development strategy.Schedule-free rolling process of electrical steel has a significant advantage of flexible,high efficiency and low cost.But the hot rolling process of the electrical steel production strip rolling campaigns faces two challenges.One is the wear control difficulty in the schedule-free rolling process because of the serious,uneven work roll wear and uneven deformation of strip,the other is the increasingly stringent requirement on the strip quality including profile and flatness in the electrical steel production due to the special use method of electrical steel.The flatness control is the bottleneck problem for schedule-free rolling of electrical steel strip.There are many basic research and application results on new generation high technology rolling mill,profile and flatness control methods and schedule-free rolling technology for solving the above-mentioned problem.However,there is no fundamental solution to the contradiction between the extreme manufacturing conditions and high precision flatness requirement of electrical steel.Complex control methods or devices are becoming more and more widely used.The profile and flatness control of electrical steel in hot rolling during schedule-free rolling processhave been studied by combination of actual production data,theoretical research and numerical simulation.Main work and innovative accomplishments are described as follows:(1)The flatness control characteristics of electrical steel schedule-free rolling has been analysed.The 3-D finite element simulation model for electrical steel hot rolling process is built considering constitutive model of electrical steel,work roll wear model and work roll thermal contour.Flatness control characteristics of schedule-free rolling process,work roll wear control characteristics after an entire rolling campaign and flatness control characteristics of many flatness control technologies are analyzed.(2)The porfile and flatness control of ASR(Asymmetry Self-compensating Work Rolls)technology has been analysed.The ASR work roll contour for schedule-free rolling of entire width electrical steel has been designed which has edge drop control,wear control and crown control ability based on original ASR technology.Based on finite element method,the effects of strip width,rolling force,diameter of rolls and roll shifting on flatness control characteristics of ASR work roll are studied.The ASR bending force mathematical model is established.The serious problem of work roll wear and crown control of the electrical steel schedule free rolling has been solved.(3)The porfile and flatness control of the lubrication combining with ASR technology has been analysed.A work roll wear model for electrical steel production considering lubrication during hot rolling process is built.The effect of shifting strategy on ASR work roll wear contour is analyzed using the work roll wear model.The ASR work roll contour has been designed considering lubrication.The results show that this study not only inprove the quality of electrical steel products,but also expand the extreme service conditions of hot rolled steel.(4)The integration effects on flatness control in hot rolling of electrical steel has been analysed.The evaluation index and its evaluation method for the integrated control of flatness are developed.The integrated optimization process and enhancement effects of flatness control technology such as lubrication,ASR work roll,VCR(Varing Contact Backup Roll)backup roll,work roll shifting system and work roll bending system on the coil numbers within a rolling campaign,the lateral stiffness of the roll gap,the influence coefficient of the bending force are analyzed.This study provides a theoretical and method support for the integration of various control methods and equipment of electrical steel.ASR work roll,ASR work roll hydraulic roll shifting function and shifting strategy,bending force mathematical model have been applied to industrial test and achieved a stable application with scale in the largest production line of electric steel in China.Industry application shows that the strip profile and flatness quality,serious and uneven work roll wear have been improved obviously when the rolling campaign increased.