Magnesia Refractory Products

articles whose primary component (more than 80 percent) is periclase (magnesium oxide). They are made from periclase (magnesite) powder produced by calcination (to sintering) of magnesite or magnesium oxide extracted from seawater. The powder formed from fused magesite or magnesium oxide is also used for the manufacture of critical products. Magnesia refractory products include magnesia-calcium products (prepared from roasted dolomite or from mixtures of magnesium and calcium oxides), magnesia-spinel products (from periclase and chromite or alumina), and magnesia-silicate products (made from dunite, serpentinite, or olivine, usually with the addition of magnesite powder). In most cases these products contain 35-75 percent MgO.

In the production process, the pulverized initial materials are mixed with a bonding additive and then molded on presses under a pressure of 80-150 meganewtons per sq m (MN/m²), or 800-1,500 kilograms-force per sq cm (kgf/cm2), dried, and roasted at 1600°-2000°C, depending on the type of product and the purity of the raw material. Unroasted products are also made with various binders and in steel magazines. Magnesia refractory products have high refractoriness (above 1900°C; up to 2800°C when prepared from pure periclase) and increased resistance to basic and ferrous melts. They are used in metallurgical plants (open-hearth and electric steel-melting furnaces, mixers, coppersmelting furnaces, and so on), as well as in rotary furnaces for roasting cement, magnesite, and dolomite. Magnesia-calcium (dolomite) products are used as lining in steel-melting oxygen converters, and magnesia-chromite products are used primarily for the crowns of open-hearth furnaces.