The work roll is subjected to quenching and rapid heat during operation, and there are temperature alternating stress and temperature gradient stress in the roll, and at the same time, it is subjected to bending deformation under rolling pressure, and tensile and compressive stress are repeatedly generated in the roll, and the internal stress acts. Under the roller, microcracks are generated in the roller. As the roller is used, the microcracks gradually expand and extend to the surface to become surface cracks. After the work roll diameter is ground, part of the crack can not be completely eliminated, and then in the next use, the surface is directly contacted with the high-temperature rolled piece, and the cooling water is rapidly cooled, causing the roll surface crack to expand and deepen, resulting in the development of cracks. When cracks or reticular cracks are intricately intersected, new rolls cannot be replaced in time. Under the action of rolling pressure and friction, the roll surface is partially subjected to high pressure and generates huge contact stress. On the one hand, the crack rapidly expands, on the other hand, the net The roll metal between the blocks is crushed, that is, the roll surface is slag. Part of the crushed roll body material remains on the surface of the rolled piece. During the next rolling process, the hard block metal material is bitten into the roll gap together with the rolled piece, so that other parts of the roll body are simultaneously indented. Roll surface pits. When the slag is large and separated from the quenched layer and the internal metal interface of the roll, it is called peeling or blasting. In the case of a deep cracked roll, since the pressure is too large when pressed, the crack develops rapidly and the roll body is broken.