Engineering Perfection in GTAW Welding: Taguchi-Optimized Root Height Reduction for SS316L Pipe Joints

This study presents a systematic optimization of GTAW welding parameters to achieve a pipe-to-pipe butt weld with a root height consistently below 2 mm when joining stainless-steel 316L material, employing the Taguchi design of experiments. To the authors’ knowledge, no similar studies have been conducted to explore the optimization of welding parameters specifically aimed at minimizing weld root height under 2 mm in stainless-steel EO pipeline welding applications. This gap in the existing literature highlights the innovative aspect of the current study, which seeks to address these challenges and improve welding precision and joint reliability. Root height, also referred to as weld root reinforcement, is defined as the excess weld metal protruding beyond the inner surface root side of a butt-welded joint. The input parameters considered are the welding current, voltage, speed, and root gap configurations of 1, 1.5, and 2 mm. Welding was performed according to the Taguchi L-09 experimental design. Nine weld samples were evaluated using liquid penetrant testing to detect surface-breaking defects, such as porosity, laps, and cracks; X-ray radiography to identify internal defects; and profile radiography to assess erosion, corrosion, and root height. Among the nine welded plate samples, the optimal root height (less than 2 mm) was selected and further validated through the welding of a one-pipe sample. An additional macro examination was conducted to confirm the root height and assess the overall root weld integrity and quality.