Chromium metallurgy

M. J. Udy, Chromium, Metallurgy of Chromium and ItsMlloys, Vol. 2, Reinhold Pubhshing Corp., New York, 1956. 

Consolidation and Fabrication. Chromium metal may be consoHdated by powder metallurgy techniques or by arc melting in an inert atmosphere (8,13,24,25) (see Metallurgy Metallurgy, powder). 

In a chemical vapor deposition (CVD) variant of conventional powder metallurgy processing, fine chromium powder is obtained by hydrogen reduction of Crl2 and simultaneously combined with fine thorium(IV) oxide [1314-20-17, H1O2, particles. This product is isostaticaHy hot pressed to 70 MPa (700 atm) and 1100°C for 2 h. Compacts are steel clad and hot roUed to sheets (24). 

Because alterations to equipment design can be cumbersome and expensive, a more economical approach may be to change the metallurgy of affected components. Metals used in typical cooling water environments vary in their resistance to erosion-corrosion. Listed in approximate order of increasing resistance to erosion-corrosion, these are copper, brass, aluminum brass, cupronickel, steel, low-chromium steel, stainless steel, and titanium. 

Denominator factors for nickel and chromium are given as 20 and 10 respectively in Linnert, Welding Metallurgy, Volume 2, Third Edition,... 

The basic corrosion behaviour of stainless steels is dependent upon the type and quantity of alloying. Chromium is the universally present element but nickel, molybdenum, copper, nitrogen, vanadium, tungsten, titanium and niobium are also used for a variety of reasons. However, all elements can affect metallurgy, and thus mechanical and physical properties, so sometimes desirable corrosion resisting aspects may involve acceptance of less than ideal mechanical properties and vice versa. 

The carbide precipitation that leads to sensitised grain boundary regions can be minimised by reducing the carbon to 0.03% or less but this increases the cost and reduces the strength. The alternative is to add stabilising elements such as titanium or niobium, which are stronger carbide formers than chromium. There are numerous texts that describe the metallurgy of... 

Chromium metal is important in metallurgy, because it is used to make stainless steel and for chromium plating (Section 12.13). Chromium(IV) oxide, Cr02, is a ferromagnetic material that is used for coating chrome" recording tapes. 

Metallurgy aluminothermic production of chromium metal by reaction of aluminum powder and Cr203... 

The term cermet derives from the combination of ceramic and melal. Cermets are produced by powder metallurgy techniques and represent Ihe bonding of two or more metals. They are particularly useful at high temperatures (850- I250"C). Chromium is used in several cermet combinations, including chromium-bonded aluminum oxide, metal-bonded chromium carbide, and metal-bonded chromium horide. 

An industrial method is briefly described in Ref 2, p945 Chromic oxide has been used in metallurgy, in manuf of soluble Cr salts, as a green pigment in manuf of glasses and ceramics and as a catalyst. C O -CuO catalysts are widely used, such as in manuf of methanol and in cyclizations of hydrocarbons (Refs 2 5). Its use in smoke -producing pyrotechnic compns is discussed under Chromium Compounds for Smoke Production, Chromic oxide, as well as Cr hydroxide, are parent compds of Chromites Refs l)Mellor 1 1 (1931), 176-85 2)Kirk Othmer 3 (1949), 944-5 3)Ullmann 5... 

Foa V, Riboldi L, Patroni M, et al. 1988. Effects derived from long-term low-level chromium exposure in ferro-alloy metallurgy. Study of absorption and renal function in workers. Sci Total Environ 71 389-400. 

Figure 7.45 Chromium layer (arrow) at fatigue initiation site (F). (Reproduced from COM 1999 and 2005 with permission from the Metallurgy Society of CIM)...

Fredriksson H. Heilner L., The influence of carbon on the segregation of chromium in steel. Scand. J. Metallurgy 3 974),6 -68... 

The 8-hydroxyquinoline method was applied for determination of aluminium in plant materials [15,76,77], soil extracts [76], silicate rocks and minerals [2], cast iron and steel [1,8,9,14], nickel- and copper alloys [1], chromium [78], beryllium [79], metallurgy products [80], titanium concentrates [7], and phosphates [81]. 

OTHER COMMENTS used in the manufacture of bronzes, brass, and other copper alloys useful in the manufacture of electric wiring, electrical conductors, switches, and ammunition electroplated protective coatings and undercoats for nickel, chromium, zinc, etc. used in corrosion-resistant piping has also been used in cement, food, drugs, metallurgy, nylon, paper products, pigments, and dyes use as a pollution control catalyst. 

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