Residual Stress and HAZ Behaviour in Thin-Walled AISI 304 Stainless Steel under Orbital TIG Welding: A Thermo-Mechanical Study Across an Eight-Level Welding Speed Range

This study focuses on the effects of the welding speed on the heat affected zone (HAZ), residual stress and microstructural characteristics of thin-walled AISI 304 stainless steel orbital TIG-welded tubes. Welding speeds between 0.5 and 2.5 mm/s have been assessed based on an integrated experimental-numerical model that uses direct metallurgical measurements coupled with finite element method (FEM) simulations. Metallographic evaluation of the HAZ widths showed average deviation of less than 5 % in comparison to the corresponding FEM estimations in most speeds. The microstructural analysis revealed a definite relationship between thermal cycles and δ-ferrite dendrite coarseness hence showing a connection between weld speed and solidification behaviour. FEM-derived residual stress patterns were found to be non-linear in terms of velocity; best mechanical and microstructural performance was found at 2.3 mm/s. The results also demonstrate the importance of fine speed resolution and confirm the use of FEM as a reliable predictive tool of thermal and mechanical effects of precision TIG welding applications.