Andalusite castable is a high-performance refractory castable made of natural andalusite as the main raw material. Andalusite is an aluminum silicate mineral (Al₂SiO₅) that has the property of converting into mullite and silicon dioxide at high temperatures, giving the castable excellent refractoriness and thermal stability.
Andalusite castables are characterized by good slag resistance and thermal shock resistance. Especially at high temperatures, the linear change rate is smaller. Castables with andalusite added have a more stable volume due to the characteristics of the raw materials themselves.
The combination of the particle size of andalusite aggregate in the raw material of andalusite castable can also adjust the thermal expansion rate. After heat treatment, the volume expansion is weakened and the linear change rate is reduced. The thermal shock resistance of this castable is due to the decomposition of the added andalusite at high temperature to form a structure of mullite and silicon-rich glass phase. The silicon-rich glass phase produced by andalusite can fill the pores and promote the enhancement of sintering degree. In addition, the castable with andalusite has a structure that releases thermal stress slowly during thermal shock, and the thermal shock stability will also be improved.
The oxide layer of andalusite aggregate is relatively thin, and the introduction of andalusite aggregate greatly improves the oxidation resistance of the castable. The glass phase produced after the decomposition of andalusite fills the pores and prevents oxygen from entering the castable. As the particle size of andalusite aggregate decreases and the sintering temperature increases, the amount of silicon-rich glass phase increases, the porosity decreases, and the oxidation resistance increases.
The strength of andalusite castable is due to the introduction of andalusite aggregate, which increases its strength after high temperature. Andalusite can generate secondary mullite after decomposition, which can promote the combination of andalusite aggregate and other raw materials, thus greatly improving the high temperature strength of the castable. Moreover, with the addition of andalusite aggregate, the SiO2 generated after andalusite decomposition increases, and the amount of secondary mullite generated also increases, and the mild and high temperature strength is further improved.
The performance of andalusite castable is very good in high temperature resistance and thermal shock resistance. In areas with severe high temperature erosion, andalusite castable is a good choice.