Research On Deformation Behavior And Control Tactics Of Strip Ridge-Buckle

With the continuous development of manufacturing technique, steel production equipment and flatness control technology, the quality of strip shape has been able to achieve a relatively high level. However, the problems of ridge-buckle occurred in the production process constrain the further improvement of quality. Due to many influence factors that lead to the reinforcement of strip steel, therefore, it is difficult to make quantitative research theoretically. At the present, the investigations available at home and abroad mainly focus on the measurement and prediction of the amount of reinforcement, there are few researches on the mechanism and control method of reinforcement, and no reasonable explanation can be given for the local waves on the steel strip with reinforcement after uncoiling. As a result, the research on the mechanism and control method of reinforcement has great significance for both academic studies and practical production. For this reason, this paper makes study of the mechanism and the control strategy of ridge-buckler in strip and coiling process in depth, basing on the numerical method and analytical method, and achieves the following innovative results:(1) To analyze the radical reasons of reinforcement on strip steel, establish the calculation model of coil elastic-plastic stress field and ridge-buckler height basing on the theory of three-dimensional elastic-plastic deformation. For the different features of local heights and waves, analyze the reasons of ridge-buckle defects result from both features from the aspect of stress, and investigate the impacts all the factors have on reinforcement, get the major conclusion that the ridge-buckle defects caused by local height occur firstly on the outermost layer, and appear on the innermost layer when they are caused by local waves.(2) To analyze the critical stress of strip steel reinforcement and the relation between the factors, according to the characteristics of local height and waves of ridge-buckle defects, basing on the hypothesis of stress function and S.Timoshenko minimum work principle, get the distribution of stress field of steel coils with ridge-buckle defects on both outer and inner side, and set up the calculation model of critical coiling tension basing on the principle of galerkin virtual displacement, analyze the relation between critical tension and its other factors, providing theoretical basis for the control method. This paper has also established the judging method of elastic limit of ridge-buckle height basing on the bi-directional stress yield criterion, and by inducing the idea of secondary perturbation into the analysis of post-buckling deformation, get the relation between the tension of post-buckling deformation and deflection, finally perfect the theory of buckling deformation of strip steel.(3) Analyze the effect all the factors have on the local deformation of strip steel in the cold rolling process, set up the unstable-buckling calculation model, providing theoretical basis for minimizing the deficiencies so that to eliminate the waves. Combining the models such as buckling height, buckling critical stress, rollers-piece quick coupler and unstable buckling, achieve the assessment strategy of limit values of local deficiencies and control method of strip steel in cold rolling process basing on the PSODE algorithm, and form the synthetic optimizing control system of buckling on the raw materials from hot rolling and cold rolling process, provide data support for solving the problem of buckling, the rate of sending back caused by buckling in the process of colorful material decrease from 15.8% to 0.18%, which have significant application value for improving the shape quality of strip steel and industrial production.