Effect of Ultrasonic Power on the Microstructure and Properties of 304 Stainless Steel Welded Joints Through Cold Metal Transfer Welding Assisted with Ultrasonication

With the development of welding technology, low heat input and high efficiency cold metal transfer welding have become the main methods of thin plate welding. However, low heat input easily forms columnar crystals, which will endanger the mechanical properties of joints. Therefore, ultrasonication treatment was applied to the cold metal transfer welding of 304 stainless steel to conduct cold metal transfer welding assisted with ultrasonication in this paper. The comparison between cold metal transfer welding assisted with ultrasonication and cold metal transfer showed that the weld grain diameter obtained by cold metal transfer welding assisted with ultrasonication was finer. In the welded joint, the maximum grain size diameter of the weld seam in cold metal transfer welding assisted with ultrasonication decreased to 375 μm, and the maximum tensile strength of cold metal transfer welding assisted with ultrasonication increased to 734 MPa. The texture intensity of the weld seam in cold metal transfer was significantly greater than that of the weld seam in cold metal transfer welding assisted with ultrasonication, which was ascribed to the improvement of the microstructure of the weld seam in cold metal transfer welding assisted with ultrasonication. In cold metal transfer welding assisted with ultrasonication, the flow performance of the welding pool increased, and the ultrasonic cavitation degree was intensified. This resulted in the significant refinement of the weld grain, the reduction of texture intensity, and an increase in the tensile strength. Graphic Abstract