Cyclic Thermal Shock Resistance of Corundum Refractory via Densified Spinel‐Calcium Aluminate (C‐CMA) Aggregate

Commercial spinel‐calcium aluminate (CMA) aggregates are limited in ladle applications by their high apparent porosity (∼21.5%), which severely degrades cyclic thermal shock resistance. To address the issues, this study employs high‐temperature secondary sintering at 1600°C to fabricate densified CMA (C‐CMA) aggregates, and subsequently evaluates their thermal shock resistance under simulated ladle conditions using a supersonic frequency induction heating system. The resulting C‐CMA aggregates exhibit a significantly reduced apparent porosity of 4.65% and a distinctive core‐shell structure composed of dense CA 2 and CA 6 phases. Combined with an increased calcium aluminate (CA) phase content, this tailored microstructure markedly promotes solid–liquid phase transition during thermal cycling. Consequently, compared to refractory with conventional CMA aggregates, the enhanced heat storage capacity of refractory with C‐CMA aggregates prolongs the cooling time by 81.86 s (+6.3%) and 119.98 s (+11.1%) after 1 and 3 cycles, respectively. Furthermore, the in situ generated liquid phase not only alleviates thermal stress but also continuously infiltrates and heals microcracks through an overflow mechanism. This results in significantly improved compressive strength retention, with increases of 2.63%–5.32% under cold‐state conditions and 25.75% at high temperature. These findings demonstrated that microstructural engineering via secondary sintering can effectively transform conventional CMA into a functional and self‐healing aggregate, providing a new strategy for the design of high‐performance refractory.