The restructuring-sintering mechanism of calcium alumino-titanate in tundish permanent lining castables

Calcium alumino-titanate (CAT) is widely used as a refractory raw material in China. It is obtained by the recycling of non-ferrous metallurgical solid waste and is often used in high-temperature oxidizing environments. The main crystal phase of CAT is the Ca(Al,Ti) 12 O 19 , which is unstable under high temperature oxidizing environments and preferentially forms a new phase system. In this study, CAT raw materials were prefired in air to facilitate the reconstructing process from Ca(Al,Ti) 12 O 19 to CaAl 12 O 19 in air. Herein, the effects of the prefiring of CAT raw materials on the mechanical properties and thermal conductivity of tundish permanent lining castables were studied and mechanism of restructuring-sintering of CAT aggregates in this process was proposed based on it. The results showed that the use of prefired CAT raw materials reduced the bulk density and mechanical strength of the castable samples after baking at 110 °C for 24 h. After firing at 1400 °C for 3 h, these samples showed greater volume shrinkage and higher mechanical strength than those prepared using CAT raw materials. The use of prefired CAT raw materials reduced the formation of anorthite in the castable matrix, thereby reducing the pores formed by liquid–phase transfer in the matrix; however, it resulted in castables with higher thermal conductivity than those prepared using unfired CAT raw materials.