If the Al2O3 content is higher than 90%, it is called corundum brick. Due to different resources, the standards of various countries are not completely consistent. For example, European countries stipulate that the lower limit of Al2O3 content for high-alumina refractories is 42%. In China, high alumina bricks usually refer to refractory bricks with an Al2O3 content of more than 48%. They are mainly made of natural high-grade bauxite, which contains minerals such as diaspore, bomerite, kaolinite, etc. Soft or semi-soft clay is added to the high-alumina clinker as a binder to start batching and mixing, and then it is formed, dried, and finally fired. The refractoriness of high alumina bricks is about 1770℃, and the load softening temperature is 1420℃-1550℃. Common high alumina bricks are LZ-80, LZ-75, LZ-65, LZ-55, LZ-48, etc. It is mainly used for lining blast furnace, hot blast furnace, ore-heat furnace, electric furnace roof, blast furnace, reverberatory furnace and rotary kiln. In addition, high alumina bricks are also widely used as open-hearth heat storage checker bricks, plugs for pouring systems, nozzle bricks, etc.