Fracture reason of 55SiCrA steel spring

The causes of fatigue fracture of 55SiCrA steel spring were analyzed by means of macroscopic observation, chemical composition analysis, microhardness test, metallographic examination and scanning electron microscope analysis. The results show that the inner and outer surface defects of the spring were potential crack sources, which were easy to form stress concentration and produce cracks, and the cracks continued to expand, eventually led to spring fracture.