Reason for Edge Cracking of Cold-Rolled 55Mn Strip Steel and the Cold-rolling Control Measures

The cause of the edge cracking of cold-rolled 55Mn strip steel was analyzed by means of the optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and so on, and the optimal control measures of cold-rolling were proposed and confirmed. The results show that the local decarburization produced in the hot-rolling process, due to the microcracks in the slab, was the direct cause of the edge cracking of cold-rolled strip steel. This edge cracking can be controlled effectively by the measures of setting the elongation of straightening to 50% of the normal elongation, increasing the mass concentration of pickling solution by 5%-10% of the normal concentration, slowing down the pickling speed to 70% of the normal speed, setting the load distribution of the first two racks to 70% of the total reduction and controlling the micro tensile stress between racks less than 70% of the normal one.