Refractories
In addition to aluminium oxide, the raw materials for refractory products are primarily oxides of the metallic elements silicon, magnesium, calcium, chromium and zirconium. These materials often also contain carbon or silicon carbide. Ceramic-based materials resistant to temperatures exceeding 1500 °C are used in foundries and the steel-, cement-, and glass-making industries for the construction of kilns, smelters, blast furnaces, converters, tundishes and crucibles. They are also used as refractory linings for flues and chimneys. Refractory materials may be resistant to high temperatures; however, due to the extreme conditions of use, they are subject to excessive wear, therefore requiring regular maintenance and frequent replacement. Refractory products are generally manufactured by pressing, stamping or casting.