Research And Application On The Mathematical Modelling Of Edge Drop During Non-oriented Silicon Steel Rolling By Six-high Cold Strip Mills

Non-grain-oriented(NGO)silicon steel strip is an important soft magnetic material.In order to reduce eddy current loss,it is necessary to use cold rolled laminates that are below 0.5 mm in thickness.In order to improve the lamination coefficient,the strip's edge drop should be controlled within 5 micron-meters,which is strict requirement on the control of edge drop in cold rolling process.Because of the low accuracy of on-line model,Finite Element Method is the usually adopted research method for edge drop control,however,due to the large width/thickness ratio,large number of edge drop control actuators,and the need of calculating the post cold rolling product profile,the calculation time of FEM is too long.In view of the above problems,this paper proposes a new model for the calculation of NGO strip's edge drop during six high cold rolling,and the following aspects were conducted:(1)Based on analysis of previous roll stack's elastic deformation theories,the influence function method based on the partitioned matrix iteration scheme is proposed:Influence Function matrix solution for the six-high roll stack is founded,and by partitioning the matrix solution,the coefficient matrix with the smallest condition number is proposed as the outermost iteration.The results of ABAQUS finite element software show that the accuracy is less than 5%and the speed is f-aster.By the roll deformation model,the edge drop control effectiveness of six-high rolling mill control actuators is analyzed and compared.(2)By studying existing models for strip deformation,considering strip's elastic-visco-plasticity and three-dimensional deformation near the edge,the capabilities of Karman equation are enriched to 3-dimension.It is coupled with influence function model and post deformation model to establish a roll stack-strip-post deformation coupling model.The comparison results of the coupling model and experiment show that the mode can serve as a mathematical tool to study edge drop formation.transfer and its control.Based on the model,it is concluded that the lateral flow of metal is the reason of edge drop formation but also it provides the possibility of edge drop control.(3)Based on the developed coupling model,the laws of edge drop effectiveness coefficients are obtained,and three edge drop control methods are studied including work roll contour,edge drop automatical control and small work roll diameter rolling mill:firstly an optimal design is performed to find an optimal MEVC work roll contour which posseses best edge drop control ability and least edge tension,secondly consecutive calculations of multi-stands are conducted,the effectiveness and transfer coefficients of whole cold rolling process are obtained,and a multi-point edge drop automatic control strategy is proposed,finally the effect of small work roll radius on edge drop control is studied.(4)Based on the research of work roll contour optimal design,automatic control strategy of edge drop and application of new rolling mill,these three aspects,a positive impact has been made on the industrial applications of a cold tandem rolling line and a reversal rolling line:the optimized work roll contour strengthened the six-high mill's edge drop control ability,the designed on-line control model has been successfully applied into the first domestically designed control system of 5-stand cold tandem rolling line,the system remains stable after long term operation,as for the newly operated six high mill with small work roll diameter,a crossing process control of edge drop between hot and cold rolling is adopted,results shows an increase of edge drop target hit rate.