Study on High-Cycle Shear Fatigue Behavior of Two Kinds of Spot-Welded 980 Mpa Ultra-High-Strength Steels

DP980 and QP980 steels are chosen to evaluate their properties of welded spot under high-cycle shear fatigue test. Samples are analyzed by OM and SEM after fatigue test. It was observed that QP980 steel has a better performance of anti-high-cycle fatigue fracture at the same welding parameters. Both fatigue cracks of two kinds of welded spot initiate from the end of pre-cracks between two base materials, and better anti-high-cycle fatigue performance of spot-welded QP980 are found due to higher initiation difficulty of fatigue cracks which has some connections with higher hardness of martensite in this area.