Physicochemical and thermo-physical behaviour were studied for the agglomerated submerged arc fluxes for CaO–SiO2–CaF2 and CaO–SiO2–Al2O3 flux system. Mixture design approach was used to develop twenty-one fluxes. Thermogravimetric (TGA), differential-scanning calorimetric (DSC), hot-disk technique and XRD techniques were utilized to analyse the fluxes. Structural behaviour of fluxes was analyzed using Fourier transform infrared spectrometer. Thermal behaviour of fluxes was observed in the temperature range of 25 °C to 900 °C. Thermo-physical behaviour such as specific heat, thermal diffusivity and thermal conductivity of each flux were evaluated by hot disc technique. Multi objective optimization was performed to derive the optimized flux formulations. This type of flux formulation helps us to evaluate the physical-chemical and thermo-physical behaviour of different mineral constituents used during submerged arc welding process. © 2019 Elsevier Ltd and Techna Group S.r.l.