Impact of reverse Marangoni convection and arc constriction on flux-based TIG welding processes of AISI 304L stainless steel

This study aimed to enhance the depth of penetration (DoP) of AISI 304L weldments through the application of oxide fluxes. Various flux application methods, such as flux-bound TIG (FB-TIG) and flux-zoned TIG (FZ-TIG), were compared to A-TIG and conventional TIG (C-TIG). Reverse Marangoni convection and arc constriction effects were found to be the primary factors contributing to higher DoP and minimal bead width (BW) in all flux-assisted welds. FZ-TIG (centre: TiO₂; side: SiO₂) and FB-TIG (TiO₂—1 mm gap) demonstrated 131.26% and 127.48% increases in DoP, respectively, compared to the C-TIG welded sample. Among the fluxes, SiO₂ exhibited greater arc constriction due to its higher ionization potential and electronegativity in the arc periphery region. The δ-ferrite morphology in FB-TIG and FZ-TIG weldments showed a continuous network, whereas a scattered network was observed in the C-TIG weld zone. Tensile test indicated satisfactory mechanical properties with failures occurring within the weldment.