Mechanical Characterization of Welded AISI 304L Stainless Steel Using Tungsten Inert Gas (TIG) and Manual Metal Arc (MMA) Welding Processes

Abstract

AISI 304L austenitic stainless steel is considered weldable at various fusion welding process. Manual metal arc (MMA) welding of austenitic stainless steel is often associated with probems such as residual stresses, cold cracking and inclusion in the weld metal causing premature failure. These identified welding defects can be minimised by the use of tungsten inert gas (TIG) welding process. The effects of tungsten inert gas welding and manual arc welding on the mechanical properties of AISI 304L austenitic stainless steel were investigated. A 300 x 300 x10mm plate of austenitic steel was cut into 8 pieces and each plate faces were chamfered at an angle of 300 and 2.5mm root gap. TIG and MMA welding processes were used to join the plates in a single V butt joint. The strength of the weld joint was evaluated for impact, bending, hardness and tensile tests. TIG weld joint was found to exhibit higher yield and ultimate tensile strength of 416MPa and 530MPa respectively while the base metal and MMA showed the least yield and tensile strength of 354MPa and 423MPa. Impact energy of 222J was absorbed by the base metal; while TIG weld joint was 207J and MMA absorbed the least energy of 201J. Microhardness values were higher at the weld metal for both welding processes and TIG joint found to give higher bending strength. Microstructural investigation also indicated that MMA weld metal had more delta ferrite than the TIG weld.