Analysis and prevention of side cracking phenomenon occurring during hot rolling of thick low-carbon steel plates

In this study, a microstructural investigation was conducted on the side cracking phenomenon occurring in thick low-carbon steel plates during hot rolling. Particular emphasis was placed on the role of iron oxides and ferrite-pearlite band structure in the side cracking. Detailed microstructural analyses of the cracked region showed that the ferrite-pearlite band structure in the side region was considerably slanted to the surface, while that in the central region was parallel to the surface. Small cracks were often observed when the iron oxide layer formed by inhomogeneous oxidization along the slanted ferrite-pearlite band structure in the side region within 30 mm from the plate edge was intruded into the interior after hot rolling. In addition to these small cracks, a few large cracks were also found when some protrusions formed on the plate surface were decarburized, folded and then intruded into the interior. Based on these findings, the parallel arrangement of the ferrite-pearlite band structure in the side region by the appropriate control of the hot rolling process and the minimization of the iron oxide formation by the minimized time exposed to high temperatures were suggested in order to prevent or minimize the side cracking.