The thermal fatigue behavior and cracking characteristics of hot-rolling material

The purpose of this study is to investigate the influence of rolling speed and various constituent phases on the thermal fatigue behavior of cast iron. Alloy cast irons with different solidification microstructure were chosen to conduct the surface-rolling thermal cycling test for a simulation of hot roll in this study. The results indicated that the thermal fatigue life of cast iron was reduced with decreasing rolling-speed because of the higher inducing temperature. Based on the observations, the developing fatigue-crack mainly initiated on the surface and penetrated into the interior of material; the nucleation and propagation of fatigue cracks were preferentially directed along the clustering zone of bulk carbides and graphite nodules. The dissolution of eutectic Fe3C and extruded-deformation of graphite will cause this cast iron to occur severe fatigue crack, and thus was harmful to its thermal fatigue resistance. For this reason, the growth orientation of surface crack gradually tended to the circumferential direction when it had faster solidification structure.