Performance optimization of friction stir welded flanges: insights from a hybrid Grey-Taguchi method

Flanges play a vital role in piping systems, especially in industries like oil and gas, for efficiently connecting pipes and allowing for easy maintenance and disassembly. Welding is the most common method for joining flanges, and friction stir welding (FSW) has gained prominence due to its ability to join various metals, ease of automation, and cost-effectiveness. This study focuses on optimizing the performance of FSW flange joints of Al 6063-T66 alloy using a hybrid Grey-based Taguchi method. Key FSW parameters—rotational speed, traverse speed, axial force, and tool pin profile—were optimized through an L9 Taguchi orthogonal array to enhance joint quality. The quality of the welded joints was assessed based on tensile strength, crashworthiness, and flexural properties. The optimal settings were found to be a rotational speed of 3000 rpm, a traverse speed of 10 mm/min, an axial force of 8 kN, and a conical tool shape. These conditions resulted in tensile strength, crashworthiness, and flexural strength values of 179 MPa, 70%, and 8.32 MPa, respectively. The tool pin profile contributed most significantly (46.5%) to overall weld performance, followed by rotational speed (43.79%). A confirmatory test validated the optimization, showing that the Grey-based Taguchi method effectively improves multiple performance characteristics of welded joints.