An Experimental Investigation of Optimum Process Parameters for Friction Stir Welding of Copper Plate

In this study, the friction stir welding technique was utilized to create qualified weld joints from a 5mm thick copper plate on a vertical milling machine. The experiments involved a steel backing plate and tool profiles with different pin shapes, including flat cylindrical, cylindrical threaded pin, and square pins, each with 3 shoulder pin ratios. Process parameters were determined using Taguchi’s L9 orthogonal array. The experiments considered tool geometry or pin profile, tool rotational speed (9100 RPM, 1280 RPM, 1700 RPM), and weld speed (16 mm/min, 29 mm/min, 44 mm/min). Tensile strength analysis indicated that welding speed had the most significant impact, contributing 76.90%. Hardness analysis showed that the tool profile had the highest influence, contributing 84.67%. The highest tensile strength achieved was 345.03 MPa with a cylindrical threaded tool profile, 1700 RPM tool rotation, and 16 mm/min weld speed. The maximum hardness obtained was 94 RHE with a square tool profile, 910 RPM tool rotation, and 44 mm/min weld speed. The study revealed that welding speed significantly affected the ultimate tensile strength of FSW joints in the copper plate, while the tool profile was crucial in achieving optimal hardness in the Heat Affected Zone (HAZ), Thermo-Mechanically Affected Zone (TMAZ), and Stir Zone (SZ).