Formation and prevention of turning crack of screw for electronic parking brake system

Abstract The cracking of screws made from medium-carbon cold heading steel for the electronic parking brake system was studied through the analysis of the microstructure and the systematic investigation of the whole process, and the corresponding improvement measures were proposed at last. Results showed that the cracks initiated at the root of the threads due to insufficient plasticity generated by the large pressure during thread rolling were the resource of the fracture, which was further extruded during the turning process, while the centering condition was not well. It was necessary to adjust the appropriate parameters of rolling pressure and rolling time to avoid heavy work hardening and also pay attention to the cleanness on the surface of the rolling plate or the wheel.