Comparative study on conventional and underwater friction stir welding of copper plates

Friction stir welding (FSW) is a solid state welding in which the material is joined without melting but plasticized and stirred by the rotating tool. Underwater friction stir welding (UWFSW) is performed under the water against the conventional FSW where the process is carried out in air at room temperature. This paper deals with the investigation on the joints made by conventional and underwater FSW of copper sheet of thickness 2.0 mm. The experiments were carried out in computer numerically controlled vertical milling machine using the high speed steel tool with a rotational speed of 600,800,1000,1200 and 1300 rpm keeping the tool traversing speed of 50 mm/min and tool tilting angle of 0o as constant parameters. The investigation on the mechanical and microstructural properties of the joints made in both conditions are carried out and compared. The joint made at tool rotational speed 1200rpm has shown the maximum tensile strength of 91.5% & 66.6% to that of the base material in both conventional and underwater FSW respectively. Also, the maximum tensile strength achieved in underwater FSW at 1200rpm is approximately 27% less than the conventional FSW within the experimented parameters. Due to the presence of water, the heat generated by the rotating tool is not sufficient enough to plasticize the material compared to conventional process, the tensile strength of the welded joint is lower than the conventional FSW. Study of microscopic images reveals that the grains are so finer in underwater condition when compared with the conventional FSW.Friction stir welding (FSW) is a solid state welding in which the material is joined without melting but plasticized and stirred by the rotating tool. Underwater friction stir welding (UWFSW) is performed under the water against the conventional FSW where the process is carried out in air at room temperature. This paper deals with the investigation on the joints made by conventional and underwater FSW of copper sheet of thickness 2.0 mm. The experiments were carried out in computer numerically controlled vertical milling machine using the high speed steel tool with a rotational speed of 600,800,1000,1200 and 1300 rpm keeping the tool traversing speed of 50 mm/min and tool tilting angle of 0o as constant parameters. The investigation on the mechanical and microstructural properties of the joints made in both conditions are carried out and compared. The joint made at tool rotational speed 1200rpm has shown the maximum tensile strength of 91.5% & 66.6% to that of the base material in both conventional and un...