Magnesite Refractories

(or periclase refractories), materials consisting of magnesium oxide (periclase), with 1-10 percent additives. Magnesite powder is produced by roasting magnesite or other magnesium compounds (mainly hydrated compounds) in a rotary or shaft furnace at 1700°-2000°C. The compounds may be natural (brucite) or chemically extracted from the salt in seawater or, less frequently, from magnesium-bearing minerals such as dolomite or bischofite. The magnesite powder is composed of grains 5-15 mm in size, with 5-20 percent porosity, and refractoriness up to 2300°-2800°C (depending on purity). This powder is used for the bottoms of steel-melting open-hearth and electric-arc furnaces, as well as in the manufacture of magnesia refractory products. The latter group includes magnesite (periclase) products, containing more than 90 percent MgO, and magnesite products with various binders, containing more than 80 percent MgO. The smelting of magnesite powder in arc furnaces yields fused periclase, which is pulverized and used in the manufacture of refractory products, as well as in filling crucibles for induction melting furnaces. Highly pure periclase is used in electrical engineering. One-piece useful refractory products with near-zero porosity are also cut from fused blocks of periclase.