Effects of CeO2 doping on the sintering properties and molten slag corrosion resistance of MgO-MgAl2O4 refractory materials

Abstract

Alkaline slag plays a crucial role in the vacuum refining process, making it essential to study the wetting and penetration mechanisms between refractory materials and slag. This study investigates the effect of CeO₂ doping on the sintering behavior of MgO-MgAl₂O₄ refractories and their resistance to alkaline slag corrosion in a simulated vacuum induction furnace. The results show that CeO₂ doping (0–3 wt%) slightly increases the lattice parameters and interplanar spacing of MgAl₂O₄ and MgO, leading to lattice expansion, higher lattice defect concentration, and enhanced sintering. The bulk density increased from 2.85 g·cm⁻³ to 3.25 g·cm⁻³, apparent porosity decreased from 18.25 % to 15.66 %, compressive strength rose from 166.24 MPa to 184.97 MPa, and the residual strength ratio after thermal shock improved from 87.60 % to 90.48 %. Regarding the slag-refractory interface, CeO₂ doping increased the interfacial free energy between slag and refractory at the wetting temperature range of 1380–1450 °C. The spreading coefficient of molten slag gradually decreased, and the equilibrium contact angle and residual slag volume increased. At high temperatures, chemical reactions at the interface formed low-melting-point (CaO-Al₂O₃-SiO₂) liquid phases and high-melting-point phases (such as 2CaO·SiO₂ and 2MgO·SiO₂). The low-melting-point phases promoted slag penetration, while the high-melting-point phases hindered it. CeO₂ doping facilitated the formation of sintering necks between MgAl₂O₄ and MgO grains, both on the surface and inside the refractory, inhibiting further slag penetration. The corrosion depth at the interface decreased from 102.63 μm to 51.18 μm, significantly improving the alkaline slag corrosion resistance of MgO-MgAl₂O₄ refractory materials.