Fracture reason of 60Si2CrA type Ⅱ spring bar

The type II spring bar of 60Si2CrA hot rolled spring round steel in a certain line fractured after more than 6 years of service. The fracture reasons were analyzed by macroscopic observation, chemical composition analysis, hardness test, metallographic examination and fracture analysis. The results show that the anti-corrosion coating on the surface of the bullet strip was peeled off, which made it exposed to the corrosive medium for a long time and forms corrosion pits. The corrosion pits reduced the fatigue strength of the bullet strip and caused stress concentration. The cracks initiated and propagating here, and finally the corrosion fatigue fracture occurring.