Welding Procedure and validation of combined SS304L and SS321 in autogenous TIG Welding with socket joint for both manual and orbital

This study presents a comprehensive evaluation of autogenous Tungsten Inert Gas (TIG) welding for dissimilar austenitic stainless steel socket joints between SS321 and SS304L tubes, employing both manual and orbital welding techniques. The objective is to assess weld quality, metallurgical integrity, and process feasibility for producing high-reliability dissimilar joints without filler metal, as required in aerospace, pharmaceutical, food processing, and high-purity piping applications. The dissimilar combination of titanium-stabilized SS321 and low-carbon SS304L introduces challenges such as thermal expansion mismatch, elemental diffusion, and sensitization, particularly in constrained socket geometries. Critical welding parameters, including current, pulse settings (orbital), torch angle (manual), arc length, and purge flow rate, were optimized based on tube dimensions. Both techniques achieved full-penetration welds without defects. Post-weld evaluation was conducted through visual inspection, dye penetrant testing, and metallographic analysis, while mechanical performance was assessed via hardness mapping and pressure-based leak testing. Orbital TIG welding demonstrated superior repeatability, narrower heat-affected zones, and consistent weld quality, making it suitable for automated and high-purity applications. Manual TIG welding, though operator-dependent, produced acceptable results under controlled conditions and remains advantageous for field applications. The findings confirm that autogenous TIG welding of SS321 to SS304L socket joints is feasible and capable of producing high-quality dissimilar joints when appropriate process control and joint preparation are maintained.