Effect of periodic ultrasonic vibration on forming and properties of 316L stainless steel’s TIG weld

To deal with large heat input and improve the structure and performance of traditional TIG welding, ultrasonic vibration was adopted and directly acted on the base material to introduce periodic ultrasonic vibration into the molten pool, and the influence of ultrasonic input distance, ultrasonic application time, and ultrasonic vibration amplitude on the forming, structure, mechanical properties, and corrosion resistance of 316L stainless steel’s TIG weld was investigated; the contribution of periodic ultrasonic vibration to the improvement of welding efficiency was explored. The results show that the ultrasonic input distance has a greater impact on weld forming. When the ultrasonic input distance is fixed, the ultrasonic energy is too large, and there is a weld penetration phenomenon. When the ultrasonic input distance is gradually increased, the melt width of the weld decreases, and the effect of structure refinement is weakened. The depth-to-width ratio of the weld increases with the increase in the ultrasonic application time, and the ratio is maximized when the ultrasonic application time is 0.5 s, which is 68.73% higher than that of the original weld. The appropriate ultrasonic vibration amplitude can simultaneously improve the strength and plasticity of the welded joint. When the ultrasonic vibration amplitude is 20.5 μm, the grain refinement effect is obvious. Compared with no ultrasonic vibration, the tensile strength is increased by 9.65%; the elongation after fracture and sectional shrinkage are increased by 35.38% and 11.22%, respectively, and the hardness and corrosion resistance are significantly improved. After applying periodic ultrasonic vibration and increasing the welding speed by 60 mm/min, the mechanical properties of the welded joints are still improved, indicating that the application of periodic ultrasonic vibration is beneficial to the improvement of welding efficiency.