Reasons Analysis on Fracture of a Spring of the Railway Axle Box

A spring of the railway axle box fractured during service. The fracture reasons of the spring were analyzed by methods of chemical composition analysis, non-metallic inclusion examination, hardness testing, microstructure and surface decarburization layer examination, and fracture analysis. The results show that:during the service, the discontinuous dents on the spring surface generated stress concentration and became the crack source, and the fatigue cracks expanded constantly, which led to the fatigue fracture of the spring.