Abstract:The surface of SMA490BW weathering steel was subjected to ultrasonic impact treatment by USP-300 ultrasonic surface processing device. The microstructure, microhardness and residual stress of the specimens before and after ultrasonic impact were studied, and the corrosion rate and corrosion fatigue life of the welded joints of SMA490BW weathering steel before and after ultrasonic impact were compared. The microstructure of SMA490BW weathering steel after ultrasonic impact was observed by optical microscope, and the surface hardness and residual stress of welded joint were measured by testing instrument. The mechanism of improving corrosion resistance and fatigue life of SMA490BW weathering steel by ultrasonic impact was analyzed. The test results show that ultrasonic impact treatment can refine the surface grain to form a dense plastic deformation layer, improve the microhardness, introduce effective residual compressive stress on the surface of the material, reduce the corrosion rate and reduce the weight loss. At the same time, after ultrasonic impact treatment, the crack propagation path becomes more complicated, the crack propagation rate decreases, and the corrosion fatigue life of welded joints increases.