As a part of natural aluminum-silicon raw materials, andalusite’s special properties can make up for the lack of properties of other raw materials, thereby enriching and improving the properties of high-alumina refractory materials.
For all refractory materials, excellent (high temperature) mechanical strength and high softening temperature under high load are the first performance indicators that must be met. High creep resistance and good thermal shock stability are also very necessary, especially for kilns at high temperature and subjected to high mechanical stress. Erosion is defined as a chemical reaction between refractory materials and processed materials such as slag, metallic liquids, dust and gases. Especially in the iron industry we can find all different kinds of erosion. Refractory materials have low reversible thermal expansion and generally good thermal shock resistance, which is also the requirement for kiln lining materials in the harsh thermal process of modern industrial kilns.
Among aluminum-silicon-based materials, it significantly improves the above-mentioned properties. In actual use, its application in products is generally considered from the following aspects.
Used as “active” mullite: Compared with synthetic mullite, andalusite has high temperature reactivity, and the generated primary and secondary mullite has higher load softening temperature, higher mechanical strength and creep resistance performance. Typical applications include low-creep high-alumina bricks for ironmaking hot blast stoves, coke oven mullite-SiC bricks, cement kiln mullite-SiC bricks, direct reduced iron furnace lining bricks and castables, Al2O3-SiC-C bricks for torpedo tank cars , Heating furnace bricks/castables, industrial furnace roof bricks, hanging bricks, etc.
Used as a thermal stress inhibitor: the structural change and high silica glass phase produced by the andalusite-mullite process can greatly improve the thermal shock stability of the product. The fields of application include ladle and tundish castables, aluminum smelting anode roasting furnaces, lime kilns, cement kiln coal injection pipes and kiln mouth bricks/castables, foundry intermediate frequency furnaces/induction furnaces, molten iron three-removal treatment spray guns, high-temperature kiln furniture, Honeycomb ceramics, etc.
Used as an expansion agent: the appropriate amount of residual expansion (+0.3% to +1.5%) of andalusite products at high temperatures and the secondary mullite process can ensure volume stability. This is especially important for structural lining materials such as blast furnaces, ceramic kiln linings and kiln cars. It is also important for unshaped refractory materials such as fire clay, gun clay and iron trench castables.
Used as a high-temperature binding phase: andalusite phase transformation will form a mullite matrix. This matrix will strengthen the combination of granules and granules, granules and fine powders. The improvement of bonding strength, especially the medium temperature strength, can improve the service life of materials, especially amorphous materials, especially light bricks and light castables.