Andalusite is heated to 1300 ℃ and becomes mullite. It is a high-grade refractory, which is the same as kyanite.
In the process of heating andalusite into mullite, a good mullite network can be formed, and the volume expansion is about 4%. This is an irreversible crystal transformation. Once transformed, it has higher fire resistance. The fire resistance can reach above 1800 ℃, and it has high resistance to sudden cooling and heat, high mechanical strength, strong thermal shock resistance, strong slag resistance, high load conversion point, high chemical stability (even insoluble in hydrofluoric acid) and strong chemical corrosion resistance.
