TITANIUM PROCESSING

preparation of the ore for use in various products. Titanium (Ti) is a soft, ductile, silvery gray metal with a melting point of 1,675 C (3,047 F). Owing to the formation on its surface of an oxide film that is relatively inert chemically, it has excellent corrosion resistance in most natural environments. In addition, it is light in weight, with a density (4.51 grams per cubic centimetre) midway between aluminum and iron. Its combination of low density and high strength gives it the most efficient strength-to-weight ratio of common metals for temperatures up to 600 C (1,100 F). Because its atomic diameter is similar to many common metals such as aluminum, iron, tin, and vanadium, titanium can easily be alloyed to improve its properties. Like iron, the metal can exist in two crystalline forms: hexagonal close-packed (hcp) below 883 C (1,621 F) and body-centred cubic (bcc) at higher temperatures up to its melting point. This allotropic behaviour and the capacity to alloy with many elements result in titanium alloys that have a wide range of mechanical and corrosion-resistant properties. Although titanium ores are abundant, the high reactivity of the metal with oxygen, nitrogen, and hydrogen in the air at elevated temperatures necessitates complicated and therefore costly production and fabrication processes. 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 BritannicaMatthew J. Donachie, Jr. (ed.), Titanium: A Technical Guide (1988), offers an excellent engineering review of the metallurgy and fabrication of titanium metal. A more scientific review of mechanical and physical properties is presented in E.W. Collings, The Physical Metallurgy of Titanium Alloys (1984). Most comprehensive collections of technical articles on titanium and its alloys are found in the proceedings of international conferences on the subject, such as P. Lacombe, R. Tricot, and G. Beranger (eds.), Sixth World Conference on Titanium, 4 vol. (1989). For examinations of titanium applications, see Daniel Eylon (ed.), Titanium for Energy and Industrial Applications (1981); Designing with Titanium: Proceedings of the International Conference (1986); and F.H. Froes, Daniel Eylon, and H.V. Bomberger (eds.), Titanium Technology: Present Status and Future Trends (1985). The U.S. Bureau of Mines publishes Titanium (quarterly), a survey with additional data on supply and demand of all titanium products, including ores and pigments. Stan R. Seagle