Refractory Materials and Application
Various refractory bricks in different sizes and shapes are now available for diverse applications. The typical refractory materials include fireclay refractories, high alumina refractories, silica brick, Magnetite refractories, Chromite refractories, Zirconia refractories, Insulating materials and Monolithic refractory. Depending on temperatures and service conditions of the applications such as boilers, furnaces, kilns, ovens etc. different types of refractories are used.
Fireclay refractories are essentially hydrated aluminium silicates with 25% – 45% Al2O3 and 50% – 80% SiO2 and minor other minerals. As fireclay brick is relatively cheap and its raw materials are widespread, it is the most common type of refractory brick and used widely in most furnaces, kilns, stoves, regenerators, etc.
Silica brick is a refractory material containing at least 93% SiO2. The raw material is quality rocks. Silica brick has excellent mechanical strength at temperatures approaching their actual fusion point. This behaviour contrasts with that of many other refractories, for example alumina-silicate materials, which begin to fuse and creep at temperatures considerably lower than their fusion points. Various grades of silica brick have found extensive use in glass making and steel industry.
High alumina refractories
Alumina refractories containing more than 45% alumina are generally termed as high alumina materials. The alumina concentration ranges from 45 to 95%. Commonly used refractory are sillimanite (61%), mullite (70 –85%) and corundum (99%). The refractoriness of high alumina refractories increases with increase in alumina percentage. The applications of high alumina refractories includes the hearth and shaft of blast furnaces, lime and ceramic kilns, cement kilns, glass tanks and crucibles for melting a wide range of metals.