Research On Rolling Process Control System And Models For Hot Strip Finishing Mills

The present paper was based on the reconstruction project of hydraulic AGC system for Tianjin RockCheck 750mm medium-width hot strip rolling production line and development project of profile and flatness control system for Tangshan GangLu 1250mm hot strip rolling production line. The framework and function of process control system, the temperature prediction, the thickness control of strip head-end, the model of strip flatness and crown, flatness and profile control stategy and load distribution algorithm for finishing mills were investigated. The softwares for finishing process control and profile and flatness control are developed and applied on line, which have exhibited good performance. The chief original work and results of this paper are as follows.(1)According to the production conditions, the framework of finishing process control system for Tianjin RockCheck 750mm medium-width hot strip rolling production line and the framework of profile and flatness control system for Tangshan GangLu 1250mm hot rolling production line respectively were developed.(2)The temperature models for finishing mills were developed and the temperature prediction method finishing mills was proposed. A new temperature adaptation strategy was put forward, which could assign the finishing mills delivery temperature error to each cooling zone according to a group of temperature distribution coefficients. The temperature distribution coefficients could be adjusted according to the rolling force of each stand. The new temperature adaptation strategy could improve the prediction precision of finishing mills delivery temperature, meanwhile, the prediction precision of rolling force could be improved.(3)The thickness control precision of strip head-end was improved from the aspects of rolling force model, roll gap position model and thread adaptation model for finishing mills. The high precision rolling force model was developed in consideration of the effect of residual strain and inter-stand tension stress. The strip width influence on mill stretch was analyzed with influence function method, and then a strip width compensation regression model for mill stretch was contructed. The application of influence function method has provided a new way to analyize the effect of workpiece width on the mill stretch. In view of the deficiency of the present used finishing thread adaptation method that only the thickness deviation of the upstream stands can be eliminated and the condition was not considered, that the thickness deviation resulted from deformation resistance error would occurred repeatedly in each downstream stands. A new thread adaptation method was proposed to solve the problem above mentioned.(4)The profile and flatness control model was developed. The concept of uniform load roll gap crown was proposed. The uniform load roll gap crown under different condition was calculated with the influence function method, and then on the base of calculatin results the regression model of uniform load roll gap crown was constructed. The concept of unload roll gap crown was proposed which has reduced the factors influencing the unload roll gap profile into two and has eventually simplified the regression model of uniform load roll gap crown.(5)Based on the profile and flatness control model, a new profile and flatness control strategy was proposed. CoMPared with that of present used, the quality of target strip crown could be improved without deteriorating strip flatness quality according to the use of the new control strategy.(6)The load distribution algorithm for finishing mills provided by Mitsubshi Electric Corporation was systematically analyzed. Under rolling force or power load distribution mode, an improved algorithm, which was aimed at solving the problem emerged when using the traditional Newton-Raphson method, was proposed to realize the rolling force and power distribution mode online application. The optimization method of load distribution coefficient was conducted with the combination of GA and BFGS algorithm, which provided theoretical basis for the determination of load distribution coefficient.The present paper was focused on the hot strip finishing mills online process control. The finishing mills process control system for Tianjin RockCheck 750mm medium-width hot strip rolling production line and profile and flatness process control system for Tangshan GangLu 1250mm hot strip rolling production line have been applied in practice successfully.