Andalusite is a natural, high-quality, energy-saving, high-aluminum refractory mineral raw material, which is mainly used in the production of refractory materials for steel metallurgy. In order to use andalusite reasonably, we must first have a general understanding of the performance of andalusite when it is used. Andalusite exhibits the following characteristics during use:
1. Low energy consumption andalusite is an anhydrous silicate mineral that does not contain crystal water, so the andalusite mineral raw material does not need to be pre-calcined, and the raw material can be directly put into use in production. Compared with products such as bauxite, andalusite eliminates the pre-calcination process, so the energy consumption during production is less. In addition, refractory materials made of andalusite can also achieve the purpose of energy saving during use. High-aluminum rotating and amorphous refractory materials made of andalusite, when used in key parts such as blast furnace hot blast furnaces and soaking furnaces for steel and smelting, can extend the furnace life by more than 150 to 200 furnaces compared with other refractory materials, reduce the loss rate by 43%, save energy by about 12%, shorten the smelting time, and reduce production costs.
2. Chemical stability. Andalusite is converted into a mixture of mullite (3Al2O3·2SiO2) and free SiO2. In the Al2O3-SiO2 binary system, only mullite has stable chemical properties. Therefore, refractory products made of andalusite have stable chemical properties.
3. Volume stability. When used in a high-temperature environment, the process of andalusite converting into mullite is accompanied by a slight volume expansion (linear expansion rate of 1%~1.5%). Compared with other products, the volume change is relatively small, that is, the volume is relatively stable. This phenomenon can effectively fill the joints between bricks and cracks in castables, thereby effectively blocking the penetration of liquid slag and metal, that is, good slag resistance. This volume expansion is irreversible, so when cooling, the connection remains tight. For high-alumina refractory castables, when andalusite is added to the matrix, although the construction performance is reduced, the volume stability is greatly improved. If the plasticity of andalusite is improved, then for high-alumina castables with high volume stability requirements, andalusite will be a good choice of material. Secondly, in the application of low creep clay bricks for blast furnace hot blast furnaces, because the volume effect of andalusite during mullite is small, adding andalusite can improve the volume stability of the product.
4. Good creep resistance After andalusite is converted into mullite, it forms a network microstructure of needle-shaped mullite interwoven with each other, so it has good creep resistance and good high-temperature mechanical properties. High-quality low creep clay bricks for blast furnace hot blast furnaces developed with special grade coke stone, andalusite, and fused mullite as the main raw materials have good creep, wear resistance, and high-temperature volume stability.
5. Strong resistance to thermal shock because most of the andalusite is converted into mullite at 1500℃, with the mullite phase accounting for 80% and the glass phase accounting for 20%. The liquid glass phase can absorb thermal stress when subjected to thermal shock, avoiding the generation of cracks and reducing spalling.
