Study on quarter-wave generation mechanism in DP980 steel during cold rolling

The quarter-wave defect seriously affected the quality of cold rolling products, especially in DP980 dual-phase steel production. The study is the first attempt to use a material model with transverse mechanical properties difference to explore the generation mechanism of DP980 cold rolling quarter-wave. The piecewise function was used to establish a new deformation resistance model of the strip. By this model, the mechanical property can be described in an arbitrary position. A 6-high Universal Crown Control Mill (UCM Mill) implicit FEM model, coupled with the new deformation resistance model was used to complete the research. Analysis based on the simulation results found that the thickness difference between simulation and measure data could be affected by the accuracy of the material model. Based on the multi-stand simulation results, a "local thickness drop" defect was found at 120 mm from the edge of the S3 stand. Through further research of three paths in the elastic-plastic deformation zone of stand S3, it is found that the yield strength (YS) growth rate at 120 mm away from the strip edge is much higher than other locations, which promotes the generation of high-order bending on the work roll surface and lead to the quarter-wave.