Analysis of small spalling mechanism on hot rolling mill roll surface

In order to analyze the small spalling mechanism on the surface of the hot rolling mill high speed steel roll, an actual hot rolling mill roll was investigated, and the thermal cycle and Mode II fatigue crack growth tests, which reflect the results of the investigation, were carried out. From the investigation of the actual hot rolling mill roll, it was proven that the small spalling was generated by heat crack initiation by thermal cycling and Mode II fatigue crack growth. The crack due to the thermal cycling was initiated in the oxide area. Estimation of the small spalling hot rolling mill roll life on the roll surface became possible based on the relationship between the crack growth rate da/dN and threshold Mode II stress intensity factor range ΔKIIth, and it was clarified that the life of the Mode II fatigue crack growth was longer than that of the crack initiation life by thermal cycling.