Research on quarter-wave control in DP980 steel during cold rolling based on multi-pass simulation

Quarter-wave flatness defect often appears in the DP980 cold rolling process, seriously affecting product quality. To find the causes of this kind of flatness defect, a multi-pass finite element model (FEM) based on a 2130 UCM mill was established, and the accuracy of the model was verified by three methods. The simulation results of the S3 and S4 stands show that the deviation between the simulated and theoretical profiles can be reduced when the work roll bending (WRB) force approaches the positive limiting value; as the WRB force decreases, the reduction in the quarter position of the strip increases significantly. The S5 stand is simulated under different rolling force conditions, and when near the real rolling force, the strip plastic deformation exists only in the central area effect, which is unable to solve the abnormal thickness in quarter position. The control effect of unit forward tension, entry profile, and bending force of the S3 stand was analyzed systematically. The results show that the actual setting value will cause a quarter wave, and improving the WRB force is useful to reduce but cannot eliminate the flatness defect, which is verified by experiments. The work roll compensation curve is designed to eliminate the flatness defect, and the experiment results show that the work roll compensation curve has an obvious control effect on the quarter wave.