Evolution and Control of Residual Stress of Hot-Rolled Dual-Phase Steel during Laminar Cooling on Run-out Table

The paper focuses on DP980 dual-phase steel, aiming to deeply investigate the evolution and control strategies of residual stress during the run-out table cooling process. The temperature-phase transformation coupling model was solved using the finite difference method, and the viscoelastic-plastic constitutive relationship model considering stress relaxation was solved using LU decomposition. A rapid calculation model for shape during laminar cooling of DP980 was established and validated for accuracy using industrial actual data. Based on this model, the impact of different operational conditions on the residual stress in the strip was analyzed. The results indicate that smaller initial temperature difference and initial shapes such as middle-wave or quarter-wave lead to lower edge compressive stress in the strip. In addition, the sparse cooling and off ultra-fast cooling also help to alleviate the problem of excessive compressive stress at the edge of the strip. However, implementing rear section cooling may result in uneven stress distribution in the width direction of the strip, with a greater degree of stress reduction near the edges. Based on the analysis of stress impact laws, improvements were made to the original production line processes. These improvements reduce residual stress and effectively mitigate wave-shaped defects during the laminar cooling on the run-out table.