Analysis of Flatness of Hot Rolled Steel Strip after Cooling

Abstract

To analyze non-flatness (edge wave) of hot rolled steel strip after cooling, a numerical method for the prediction of temperature and thermal stress has been developed by taking phase transformation into consideration. It has been confirmed that the temperature during cooling and the residual stress calculated by the present method agree well with the measured ones. Using this method, the occurrence of edge wave in a thin and wide hot strip (3.24×2 173mm) has been studied.The results obtained are as follows:(1) The edge wave occurs when compressive residual stress in the edge becomes greater than the critical buckling stress.(2) The residual stress becomes small when the transverse distributions of finishing temperature and of water-cooling rate after rolling are small. Water-cooling of the hot strip in the latter stage of the runout table and high coiling temperature are beneficial to reduce the residual stress.(3) The most effective measure of preventing the occurrence of edge wave is to cool the strip uniformly in the transverse direction by controlling the distribution of water-supply of the cooling device after rolling.