Early Fracture Causes of Valve Spring

The valve spring produced by a company fractured early after several hours of installation. The early fracture causes of the valve spring were analyzed by means of macroscopic observation, microscopic analysis, metallographic examination and hardness test. The results show that there was folding crack on the surface of the valve spring, which was produced in the rolling process of raw materials. Under the action of alternating load, the extension part of the folding crack tip became the source of fatigue crack and expanded continuously, resulted in the early fracture failure of the valve spring.