Failure Analysis on Straightening Fracture of Bainite Steel Rails

Means such as macro and micro fracture analysis, chemical compositions analysis, hardness test and metallographic examination were used to analyze the fracture reasons of bainite steel rails which fractured when straightening. The results show that the main reason for the fracture was attributed to intercrystalline brittleness of a great deal of acicular martensite in the microstructure of the bainite steel rails. When the rail received straightening stress, cracks initiated from inclusions at the intercrystalline brittleness phase stress concentration positions, and the cracks expanded rapidly along the brittle grain boundaries and led to fracture eventually.