Fracture Reason Analysis of a QU80 Crane Rail

A U71Mn QU80 crane rail fractured which serviced only for 1 month after exothermic welding. Means such as chemical compositions analysis, mechanical properties test, macrostructure and microstructure examination were used to analyze fracture reason of the crane rail. The results show that while the rail was welded, liquid steel generated by welding flux of exothermic welding spilled. Drops of the flux gathered at bottom of the crane raile and produced a arc-shaped notch with size of 4 mm. The notch became stress concentration point during the service process and resulted in fracture of the crane rail under the cycle of external force.