Effect of vibration on microstructure and performance of WQ960 steel welded joints

WQ960 high strength steel was welded using MAG welding process under vibration field. In order to explore the effect of vibration on the microstructure, impact ductility and tensile strength, the microstructure and mechanical properties of the welded joints were investigated under different vibration parameters. The results show that vibration can obviously improve the impact toughness of the weld zone and fusion zone up to 15%, but had little effect on the impact toughness of the heat-affected zone. Vibration can improve the tensile strength of welded joint, but the amplitude was only 2%. Owing to the vibration, the morphology of columnar grain changed and the microstructure was fine acicular ferrite which could improve the strength and toughness of welded joints. The dimples in impact fracture fiber zone were uniform and deep, and the cleavage steps in crystalline zone were apparent with a lot of uniform and refined tearing ridges.