Effect of weld groove volume on the mechanical and metallurgical performance of GTA welded martensitic stainless steel (AISI 410 SS) joints

Abstract

Effect of three groove volumes on mechanical and metallurgical performance of 6 mm thick butt welded martensitic stainless steel (AISI 410 SS) joints was studied. Three weld groove geometries (using a single-V design) that resulted in the ratio of theoretical volumes (prior to welding) as 1:1.2:1.3 were made in 6 mm thick cold rolled AISI 410SS base plates. Metallurgically compatible filler was used to weld these plates using a suitable combination of gas tungsten arc welding parameters such that sound quality in these joints was achieved. The findings indicate that variation in the weld groove volume exerts a significant influence on the tensile and impact energy absorption behaviour of these joints, besides resulting into significant microstructural changes across different zones of the weldments. Amongst all welds, the smallest groove volume of 7358.7 mm3 possessed the maximum ultimate tensile strength of 758.34 MPa. Post weld heat treatment of 750˚C/70 min. followed by slow/furnace cooling enhanced the tensile strength of these joints but the ductility reduced to a marginal extent. Microhardness values decreased due to post weld heat treatment as microstructural grain coarsening occurred in these welds. Thermocouple measurements made across different welds indicate that small groove volume resulted into higher cooling rates. Maximum impact toughness of 110.6 J and 123.8 J was possessed by the joints made using the smallest groove volume in the as welded as well as the post weld heat treated condition respectively. This study establishes that smaller weld groove volume should be preferred for improved metallurgical as well as impact toughness performance of these welds.