Effect of MgO/Al2O3 and CaO/SiO2 on the Metallurgical Properties of CaO–SiO2–Al2O3–MgO–TiO2 Slag

•The melting performance, phase composition, viscosity and the activation energy for viscous flow (Eη) of CaO-SiO2-Al2O3-MgO-TiO2 slag were studied.•The increase of MgO/Al2O3 from 0.21 to 0.54, liquidus temperature and breakpoint temperature increase, while the viscosity and Eη decrease.•The basic phase in the slags is melilite, CaO/SiO2 has a great influence on the precipitation temperature of melilite.•Compared with MgO/Al2O3, CaO/SiO2 has less effect on the thermal stability of the slags.