Analysis on Early Fatigue Fracture of High-strength Spring

Imported spring steel broke during the fatigue life test. Scanning electron microscopy, optical microscope and other means were used to systematically detect the macroscopic defects, fracture morphology and metallographic structure of the fracture samples, and determine the type and cause of spring fracture. The results show that there are fatigue cracks at the fracture site, and there is copper residue at the crack. According to the analysis of the production process, due to the existence of peeling spiral pattern in the processing process of wire coil to bar, in the straightening link, the stripping bar material rotates at high speed when it enters the straightening machine, and the copper alloy of the two-roller orthodox sleeve is bonded to the surface of the silver bright rod after the straightening process, and the silver bright rod is diffusion along the grain when it is inductively heated. Considering the low melting point of copper, it is recommended that machining plants replace copper related spare materials with other materials to avoid surface quality deterioration.