Reason for Fracture of Brake Lever Bolts

The fracture reason for locomotive brake lever bolts were analyzed by optical microscope, scanning electron microscope, and energy spectrum analyzer. The results show that the fracture mode of bolts was intergranular brittle fracture caused by stress corrosion. The external reasons for the fracture of bolts included the large bending stress on the fracture during service and severe service conditions of bolts; the internal reasons for the fracture included the banded ferrite distributed along the rolling direction and large inclusions in the microstructure of bolts. After strengthening the quality control of raw material of bolts and optimizing the heat treatment process of bolts, no fracture occurred.