Research And Application Of Plate Camber Model And Control Strategy

Under the industrial project of plate flatness, gauge and production technology optimization in a domestic4300mm plate production line, the plate camber problem during rolling process was investigated based on the experience in development and debug of the automatic control system in more than10plate production lines. In this work, the motion equation for plate camber at the entry and delivery sides was established. The elastic model for the roller system under the asymmetric rolling condition was consummated. Various factors affecting the plate camber were studied by using the influence function method. Special attention was paid to the coupling relationship between the plate camber at entry and delivery sides. Finally, a comprehensive feedback control model for plate camber was established and a systematical diagnostic strategy for plate camber was put forward. The main achievements of this paper are as follows.(1) Establishment of the motion equation for the plate camber at the entry and delivery sides. An in-depth analysis was conducted for the mechanism of plate camber during the rolling process. Using the basic theory of plane motion of rigid body, the motion equations for plate camber at the entry and delivery sides were established. According to the volume flow incremental equation, the relation of the camber curvature to the wedge rate difference between the entry and delivery side during asymmetric rolling process was acquired. The problem existed in the Nakajima’s model has been found out by rigorous theoretical derivation.(2) Investigation on the elastic model for roller system of four-high mill under transverse asymmetric rolling. The stress state and deformation of the mill under asymmetric rolling condition were investigated by using the influence function method. The rigidity inclination model for the backup roll and working roll was established. The deformation compatibility equation for the plate and roller system was improved. By adjusting the rigidity inclination coefficient of the working roll, the torque balance problem of the working roll was solved. Furthermore, a sound elastic deformation model for the roller system under asymmetric rolling condition was also established, which laid a solid foundation for the future study of the influencing factors on the plate camber.(3) Investigation on the coupling relationship between the plate camber at entry and delivery sides. Based on the motion equation of the plate camber and the elastic model of the roller system under asymmetric rolling condition, the application software for the investigation and analysis of the plate camber was developed. Considering the effects of various factors such as slab wedge at the entry side, temperature asymmetry, side guide alignment, stiffness asymmetry and the inclination of the roll gap, an in-depth and systematic study was carried out on the mechanism of the plate camber at the entry and delivery sides. Especially, the effect of the torsion at the entry side on the plate camber at the delivery side was stressed.(4) Investigation on the feedback control model and control strategy for plate camber. Under the assumption of rigid roll, the feedback control model for the plate camber at the delivery side has been established based on the distribution equation of the rolling force per width, the torque equilibrium equation, the plastic deformation equation of the plate and the elastic deformation equation of the mill. In this model, the influencing factors including slab wedge at the entry side, temperature asymmetry, side guide alignment, stiffness asymmetry and the inclination of the roll gap were considered. The corresponding feedback control system has eliminated the hysteretic characteristics. The developed model can serve as the theoretical basis for the future development of feedback control system for the plate camber.(5) Investigation and application of diagnostic strategy for plate camber. A feasible diagnostic strategy for the plate camber was proposed based on the analysis of the characteristics of the camber caused by various factors. It has been applied to solve the camber problem during the production of wide-thin dimensional plate. Through the analysis and diagnosis, specific measures have been taken and finally good results have been achieved.