Effects of Keyhole Tungsten Inert Gas Welding Parameters on 2205 Duplex Stainless Steel Welded Joints

The novel keyhole gas tungsten arc (K-TIG) welding technique was applied to weld 2205 duplex stainless steel (DSS) with a thickness of 8 mm. The effects of welding parameters on both stability time of keyhole and profile of fusion zone were discussed. And the influence of heat input on microstructure and mechanical properties of welded joints was investigated. The results showed that both quasi-steady keyhole and single-pass full-penetration welding joint were obtained by optimizing welding parameters. The welding current is a crucial factor for the formation of a quasi-steady keyhole. Furthermore, the weld metal (WM) with a heat input of 1.57 kJ/mm has more content of intragranular austenite (IGA) as well as low content of hard Cr₂N and exhibits an excellent mechanical property. Refined IGA grains, including large amounts of recrystallized grains (RGs) and high angle grain boundaries (HAGBs), could improve the strength of the welded joint and hinder the propagation of microcracks. Besides, the rod-like precipitate Cr₂N plays a pernicious role in impact toughness because it could be the microcracks origins. With an increase in heat input, the hardness of WM increases, which is owing to the growing content of both hard Cr₂N and the semi-shear Widmanstätten austenite (WA).