It is represented by magnesium products. It contains 80% to 85% of magnesia, with periclase as the main phase. The main raw materials for the production of magnesia bricks are magnesite, seawater magnesia, which is obtained by calcining magnesium hydroxide extracted from seawater at high temperature. It has good resistance to alkaline slag and iron slag. The melting point of pure magnesium oxide is as high as 2800 ° C. Therefore, the refractoriness of magnesia bricks is higher than that of clay bricks and silica bricks. Since the mid-1950s, the production of alkaline refractories has gradually increased due to the use of oxygen-blown converter steelmaking and the use of alkaline open hearth roofs, and the production of clay bricks and silica bricks has been reduced. Alkaline refractories are mainly used in open hearth furnaces, oxygen blowing converters, electric furnaces, non-ferrous metal smelting and some high temperature thermal equipment.