The aim of present study is to investigate the physicochemical and thermophysical behaviour of submerged arc welding slags designed by CaO-SiO2-CaF2 and CaO-SiO2-Al2O3 system. Slag was produced during submerged arc welding using laboratory prepared agglomerated fluxes. By using mixture design and extreme vertices approach twenty one submerged arc welding slags were formulated. X-ray fluorescence technique was used to find the elemental weight percentage of each flux ingredient. The thermophysical behavior such as specific heat, thermal conductivity and thermal diffusivity of each slag was evaluated by hot disc technique. Density of submerged arc welding slags was evaluated at room temperature. FTIR technique was used to study the structural behaviour of submerged arc welding slags. Multi objective optimization technique was performed to derive the optimized slag formulations. Individual, binary and ternary slag constituents have been developed using various regression models for thermophysical and physicochemical properties. Significance level (upto 95%) has been checked for regression models by using F-test. © 2019, Springer Nature B.V.