Research On Shape Control Characteristics Of Four - High Rolling Mill Based On Roller System Integral Deformation Model

Plate and strip is the main product in the iron and steel industry, of which the main quality indexes include organization property, dimension accuracy and surface quality. The dimension accuracy mainly includes thickness and shape accuracy. The plate-thickness control accuracy has achieved satisfactory results, but the plate-shape control is still not completely satisfied. The factors affecting plate shape are very complex. Under the action of various complex factors, rolled peice shows complicated plate-shape problem, which has serious impact on subsequent work and the service life of the plate. In the rolling process, rollers directly contact with the metal, which is the main cause to make the metal produce plastic deformation; bearing is used to support rollers and the forces of the bearing are related to the rolling process and product quality. Thereforce, based on the roller system and the load applied on the bearing, the analysis of the plate-shape control has practical application value for improving the product quality.On the basis of the elastic deformation of roller system of four-roller plate-and-strip mill and the forces of mill bearing, the overall deformation model of the supporting-roller bearings, bearing box, roller system and rolled pieces is established. Through the established model, the load distribution of the four-roller plate-and-strip mill bearing and the factors influencing the plate crown are analyzed.In this paper, the main research contents and results are as follows:(1) Based on the exsitent four-roller cold-rolling mill, the method testing radial force, axial force and the bearing-column temperature of supporting-roller four row cylindrical bearings have been provided. Meanwhile, the axial sensors, radial sensors and the temperature sensors have been designed and checked.(2) The finite element model of overall deformation of support-roller radial load testing device, supporting rollers, bearings, bearing boxes, work rollers and rolled piece has been established. Comparing the finite element model and early-completed bearing coupling model in the transverse thickness, the work roller deflection, the supporting-roller deflection and flatten process of rollers, the finite element model of overall deformation has been proved to reflect the actual rolling conditions more accurately than the bearing coupling model.(3) Based on the established finite element model of the overall deformation, the influence of the work roll diameter, support roll diameter, friction coefficient, deformation resistance and forward-and-backward tension on the load distribution of the supporting-roller bearing columns and on the plate crown of rolled piece after rolling has been analyzed. The results show that the work roller diameter has a larger influence on bearing load distribution of bearing columns and plate crown of rolled piece. And the supporting roller diameter and the rolled piece deformation resistance have a smaller influence. The friction coefficient and the forward tension also have a smaller influence.(4) Based on the transverse stiffness theory of mill, the concept of the roll gap transverse stiffness has been put forward. Meanwhile, the change rule of the roller-gap transverse stiffness with different width of rolled piece, reduction rate, deformation resistance, tension, work roller diameter and supporting roller diameter has been obtained, which has provided theoretical basis for further analysis and control of plate shape.