Research On Comprehensive Control Technology For Cross-section Thickness Difference Of Silicon Steel Strip Rolling

Silicon steel is widely used in the manufacturing of motors and transformers.Minimizing the transverse thicknesss difference of cold rolled strips as far as possible is an important guarantee for restraining laminated clearance and ensuring uniform thickness of stamping parts.It is a requirement for developing high-grade silicon steel and improving competitiveness.Up to now,there are still some problems to be solved in the control of strip cross-section profiles.The rational allocation of both the cold and hot rolling control targets and the comprehensive technological innovation from hot rolling to cold rolling are becoming more and more difficult in practice and research,and also becoming growing points of theory and technology innovation.The prediction algorithms for the symmetrical incoming shape have already been mature.However,there are few prediction algorithms for the shape of wedge incoming.The accuracy,speed and stability of calculation can not meet the practice requirements.Therefore,on the basis of the fast prediction model for symmetric strip shape of 6-high cold rolling mill,a fast prediction model for the asymmetrical incoming shape is established.The method couples the plastic deformation model of strip and the elastic deformation model of rolls into a set of linear equations to solve unknowns,avoiding the poor stability of the mutual iteration between the calculation results of the plastic deformation model of strip and the elastic deformation model of rolls,and its calculation speed of single pass is controlled at 100 ms level.It makes possible for the simulation of large-scale coils in strip rolling.In order to dig out the control cability for hot strip profiles,the influence rules of the key parameters of hot rolled strip profiles on the transverse thickness difference of silicon steel are analyzed based on the fast prediction model for the asymmetrical incoming shape.We establish an influence model of the key parameters of hot rolled strip profiles on transverse thickness difference of cold rolled strip,and formulate the control criteria of the key parameters of hot rolled strip profiles according to the influence model and statistic analyses.In order to control the crown and edge drop of hot rolled silicon steel,a type of improved CVC work roll contour compensated by tapered roll contours is designed,which weakens the strip edge drop to a certain extent.In order to further improve the defect that the edge drop of the strips rolled by CVC rolls increases significantly with the rolling length increasing,the improved concave rolls are designed and periodically shift in large stroke.The simulations and practice show that improved concave roll with periodic roll shifting strategies can effectively improve the self-perpetuating capacity of the original grinding roll contours and the control ability of the strip crown and edge drop in the late of rolling unit.It is a high efficient control technique of the hot rolled strip profile.In order to realize fine control for the transverse thickness difference of cold rolled strip in the single stand UCM,the stability mechanism of the central profile of cold rolled strip influenced by the tension feedback mechanism is explained and the control task of edge drop in cold rolling is clarified.Finally,the fine design principles of work roll contour considering the influences of grinding process is put forward.Further improving the control ability of the single stand UCM for the edge drop of silicon steel causes serious dual symmetrical quarter buckles.In order to solve the above problem,we analyse the influences of the rolling prcess characteristics,the flatness closed loop control characteristics and the rolls structures on the dual symmetrical quarter buckles,and propose the comprehensive control strategies for silicon steel edge drop and dual symmetrical quarter buckles by matching rolls bending and optimizing work roll and backup roll contours.Finally,the application characteristics and the effects of different control technologies in cold and hot rolling on improving the transverse thickness difference of silicon steel strip are summarized.It provides a verification for the theory and technology in this paper.