Design of CaO–SiO₂–CaF₂ and CaO–SiO₂–Al₂O₃ Based Submerged Arc Fluxes for Series of Bead on Plate Pipeline Steel Welds—Effect on Carbon and Manganese Content, Grain Size and Microhardness

Submerged arc welding is mainly used to weld high thickness steel plates in various applications such as offshore oil drilling platforms, bridges, building construction, and pressure vessels. Suitable flux composition and welding parameters play an important role in determining the good bead quality, which further affects the mechanical properties of welded joint. Agglomerated fluxes were formulated based on CaO–SiO₂–CaF₂ and CaO–SiO₂–Al₂O₃ flux system using constrained mixture design and extreme vertices design approach. The chemical compositions of the bead on plate have been studied using formulated fluxes. Twenty one beads on plate experiments were conducted at constant current, voltage, and welding speed using submerged arc welding process. In the present study, chemical composition, grain size, and microhardness properties of series of bead on plate weld deposits (for API 5 L X70 grade pipe line) were optimized by using multiobjective optimization approach.