Role of Activating Flux in Weld Bead Symmetricity during Dissimilar Metal Joining

Abstract

Ferritic/martensitic steels and austenitic stainless steels are high-strength steels, and highly recommended in high-temperature and high-pressure application. In general, multimetallics with different Inconel alloys are used for joining. This is quite a complex and time-consuming procedure. The current work demonstrates the efforts made to weld 8 mm-thick P91 steel and 316L SS plates in a single pass using activating flux tungsten inert gas (A-TIG) welding process without any interlayers. The main challenge is to get the symmetric weld bead profile. Flux coating is optimized in terms of flux composition, coating density, and coating pattern to get the full penetration with symmetric appearance. The current work discusses the possible cause and their solution of asymmetricity during dissimilar welding. Differential flux coating density is found to be very effective in controlling the arc column shape, fluid flow, and consequently the bead geometry. High coating density is used in the P91 side compared to 316L side. Symmetric weld profile with full penetration is achieved by applying multicomponent flux (33–38% TiO₂, 38–43% SiO₂, 13–17% NiO, and 8–10% CuO) during A-TIG welding.