manganese processing, preparation of the ore for use in various products.

Manganese (Mn) is a hard, silvery white metal with a melting point of 1,244° C (2,271° F). Ordinarily too brittle to be of structural value itself, it is an essential agent in steelmaking, in which it removes impurities such as sulfur and oxygen and adds important physical properties to the metal. For these purposes it is most often employed as a ferromanganese or silicomanganese alloy; as a pure metal it is added to certain nonferrous alloys.

Manganese is an allotropic metal—that is, its crystal structure changes with temperature. While cooling from the molten state down to 1,138° C (2,080° F), it solidifies into a body-centred cubic structure called the delta (δ) phase; from that point down to 1,100° C (2,000° F) it is in the face-centred cubic gamma (γ) phase, and from this point down to room temperature it goes through the beta (β) and alpha (α) phases. These last two phases, characterized by complex cubic structures, are extremely hard and brittle, while the simpler gamma phase is more ductile.

Manganese metal oxidizes superficially in air, rusts in moist air, and burns in air or oxygen at elevated temperatures. It decomposes water slowly when cool and rapidly when heated, forming hydrogen gas and manganous hydroxide, and it dissolves readily in dilute mineral acids, generating hydrogen and various manganous salts. The chemical reactivity of the metal accounts for its utility in metallurgy and in various chemical compounds.

History

Metallic manganese was first isolated in 1774 by Johan Gottlieb Gahn, a Swedish mineralogist who reduced pyrolusite, a manganese dioxide ore, with carbon. In 1856 Robert Forester Mushet, a British steelmaker, used manganese to improve the ability of steel produced by the Bessemer process to withstand rolling and forging at elevated temperatures. A tough, wear-resistant steel containing approximately 12 percent manganese was developed in Sheffield, Eng., by Robert Abbott Hadfield in 1882. Ferromanganese was first smelted commercially in a blast furnace in 1875; electric-furnace production began in 1890. Pure manganese was not available commercially until 1941, following work on electrolysis conducted in the 1930s under S.M. Shelton at the U.S. Bureau of Mines.