MOLYBDENUM PROCESSING

preparation of the ore for use in various products. Molybdenum (Mo) is a white, platinum-like metal with a melting point of 2,610 C (4,730 F). In its pure state, it is tough and ductile and is characterized by moderate hardness, high thermal conductivity, high resistance to corrosion, and a low expansion coefficient. When alloyed with other metals, molybdenum promotes hardenability and toughness, augments tensile strength and creep resistance, and generally promotes uniform hardness. Small quantities of molybdenum (of 1 percent or less) significantly improve the abrasion resistance, anticorrosive properties, and high-temperature strength and toughness of the matrix material. Molybdenum is therefore a vital addition agent in the manufacture of steels and highly sophisticated nonferrous superalloys. Since the molybdenum atom has the same character as that of tungsten but only about half its atomic weight and density, it advantageously replaces tungsten in alloy steels, allowing the same metallurgical effect to be achieved with half as much metal. In addition, two of its outer electron rings are incomplete; this allows it to form chemical compounds where the metal is di-, tri-, tetra-, penta-, or hexa-valent, making possible a wide variety of molybdenum chemical products. This also is the essential factor in its considerable catalytic properties. Additional reading Comprehensive and up-to-date information on many aspects of metallurgy, individual metals, and alloys can be found in convenient reference-form arrangement in the following works: Metals Handbook, 9th ed., 17 vol. (197889), a massive and detailed source prepared under the direction of the American Society for Metals, with a 10th edition that began publication in 1990; Herman F. Mark et al. (eds.), Encyclopedia of Chemical Technology, 3rd ed., 31 vol. (197884), formerly known as Kirk-Othmer Encyclopedia of Chemical Technology, with a 4th edition begun in 1991; and its European counterpart, the first English-language edition of a monumental German work, Ullmann's Encyclopedia of Industrial Chemistry, 5th, completely rev. ed., edited by Wolfgang Gerhartz et al. (1985 ). The Editors of the Encyclopdia BritannicaAlexander Sutulov (ed.), International Molybdenum Encyclopaedia, 17781978, 3 vol. (197880), presents wide-ranging reference information on all aspects, from resources through production and trade; its supplemental vol. 4 has been published as Intermet Molybdenum Yearbook (1982) and contains later information on events and developments in the industry, with statistics. A convenient single source of reference information on all the refractory metals is Clifford A. Hampel, Rare Metals Handbook, 2nd ed. (1961, reprinted 1971). Chun Tsin Wang Alexander Sutulov