Effects of YSZ and CA6 additives on densification and thermal shock resistance of Al2O3-MgO-CaO-Y2O3 refractories

To achieve high-quality and stable production of modern clean steel, novel Al2O3-MgO-CaO-Y2O3 refractories with enhanced sintering properties and thermo-mechanical properties were synthesized by introducing YSZ and CA6 as the reinforcers. A sintering reaction mechanism involving the Al2O3-MgO-CaO-Y2O3 quaternary system is proposed. The results show that the sintering process in the Al2O3-MgO-CaO-Y2O3 quaternary system was characterized by the sequential formation of Al5Y3O12→YAlO3→Y4Al2O9→Y2O3 in three distinct stages, resulting in the predominant phases of Al5Y3O12 and MgAl2O4. The YSZ addition on Al2O3-MgO-CaO-Y2O3 refractories promotes the complete reaction between Y2O3 and CaAl4O7, fostering the formation of additional Al5Y3O12, which significantly enhances the densification, leading to improvements in both compressive strength and thermal shock resistance. The addition of CA6 promotes the generation of more Al5Y3O12, which forms numerous pores during the three stages of the sintering process, and the distribution of these pores is uncontrollable. Therefore, based on the sintering reaction mechanism of the Al2O3-MgO-CaO-Y2O3 quaternary system, a low-cost and enforceable reinforcement strategy for Al2O3-MgO-CaO-Y2O3 refractories is proposed, which is expected to focus on the application of YSZ in Al2O3-MgO-CaO-Y2O3 refractories for clean steel smelting.