In order to simulate and analyze hot strip crown and flatness accurately and efficiently, the 3-D (three-dimensional) coupled model involved in RPFEM (rigid-plastic finite element method) is improved based on the analytical model of forecasting rolling force distribution. In the analytical model, variational method is employed to solve the lateral flow of metal and influential function method is employed to calculate roll deflection, the lateral distribution of rolling force can be obtained rapidly by iterative strategy. Then the 3-D coupled model uses the result as initial distribution of rolling force to calculate roll deflection and makes the initial on-load roll gap profile close to the final value, so as to reduce iterations and increase efficiency. Compared with previous algorithms, the improved model can reduce the iterations by about 50% and shorten the computing time by about 60% on the basis of the calculation accuracy.
WANG Tao, XIAO Hong, ZHAO Tie-yong, QI Xiang-dong (College of Mechanical and Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China)
Rolling schedule not only determines the rolling process to be going smoothly, but also affects the shape accuracy and structure properties of finished strip. In order to gain good strip crown and flatness, the calculation formulas of the most suitable rolling force and bending force are deduced. By taking relatively equal load of rolling power and good shape as objective functions, the optimization mathematical models of finish rolling schedule are established. By contrast, the rolling schedules after optimization can improve the rolling mill working status and ensure the strip crown and flatness to be good. At the same time, the setting value of bending force is improved and this leaves more space for on-line shape control.
QI Xiang-dong, WANG Tao, XIAO Hong (National Engineering Research Center for Equipment and Technology of Cold Strip Rolling, Yanshan University, Qinhuangdao 066004, Hebei, China)
In order to improve rolled strip quality,precise plate shape control theory should be established.Roll flattening theory is an important part of the plate shape theory.To improve the accuracy of roll flattening calculation based on semi-infinite body model,especially near the two roll barrel edges,a new and more accurate roll flattening model is proposed.Based on boundary integral equation method,an analytical model for solving a finite length semiinfinite body is established.The lateral surface displacement field of the finite length semi-infinite body is simulated by finite element method (FEM) and lateral surface displacement decay functions are established.Based on the boundary integral equation method,the numerical solution of the finite length semi-infinite body under the distributed force is obtained and an accurate roll flattening model is established.Different from the traditional semi-infinite body model,the matrix form of the new roll flattening model is established through the mathematical derivation.The result from the new model is more consistent with that by FEM especially near the edges.
