Structure-property Interaction in Flux Assisted Tungsten Inert Gas Welding of Austenitic Stainless Steel

Austenitic stainless steel SS304 grade was welded with active Tungsten Inert Gas (TIG) welding process by applying a flux paste made of SiO2 powder and acetone. SiO2 flux application improves the weld bead depth with a simultaneous reduction in weld bead width. The improvement in penetration results from arc constriction and reversal of Marangoni convection. Experimental studies revealed that the SiO2 flux assisted TIG welding can enhance the weld bead penetration by more than 100%. Full depth welds up to 6mm were obtained by applying SiO2 flux. Microstructure reveals a reduction in ferrite formation in fusion zone by applying SiO2 flux. Samples welded with flux exhibits reduction in tensile strength and improvement in impact strength. Fractography of the tensile test specimens reveals the presence of oxide inclusions in the samples welded with flux. The relation of ferrite content and mechanical properties are presented in this paper.