The fused magnesia is the product of magnesite and other magnesia raw materials that are sintered after high temperature treatment. Magnesia calcined with natural magnesite as raw material by one or two step calcination process with high-temperature equipment such as shaft kiln and rotary kiln is called sintered magnesia; Magnesite and other raw materials are melted in the electric arc furnace to reach the melting state and cooled, which is called fused magnesite; The magnesia extracted from seawater is called seawater magnesia. Magnesia is one of the most important raw materials for refractories, and is used for manufacturing various magnesia bricks, magnesia-alumina bricks, ramming materials, furnace repair materials, etc. It contains many impurities and is used to pave the bottom of the steelmaking furnace.