Fracture Reason Analysis of the Roller

A roller which hadn’t reached its normal lifetime fractured when its diameter reduced from 780 mm to 780 mm. Means such as chemical compositions analysis,fracture analysis,microstructure examination and the hardness test were used to analyze the fracture reason of the roller. The results show that there were micro cracks at the junction surface of roller body and roller neck,which was the main reason for the fracture. Thin and brittle quenching microstructure formed at this position because of the improper handling during seal ring covering process. Additionally,this position was just right the stress concentration zone,so micro cracks produced. Under the common action of the pressure and torsion stress,the formed micro cracks propagated to the center of the roller due to the stress concentration. As the crack depth increased to a certain value,fracture of the roller happened.