Ch. 3— Minerals Supply, Demand, and Future Trends • 91 



ing, catalysts, and refractories. In 1986, 88 percent 

 of the chromite (common ore form of chromium) 

 consumed in the United States was used by the 

 metallurgical and chemical industry, and 12 per- 

 cent by the refractory industry. 



Metallurgical Uses. — Chromium is used in a 

 variety of alloy steels, cast irons, and nonferrous 

 alloys. Chromium is used in these applications to 

 improve hardness, reduce creep, enhance impact 

 strength, resist corrosion, reduce high-temperature 

 oxidation, improve wear, or reduce galling. 



High-carbon ferrochromium contains between 

 52 and 72 percent chromium and between 6 and 

 9.5 percent carbon. Low-carbon ferrochromium 

 contains between 60 and 75 percent chromium and 

 between 0.01 and 0.75 percent carbon. Ferrochro- 

 mium-silicon contains between 38 and 45 percent 

 silicon and between 34 and 42 percent chromium. 



The largest amount of ferrochromium (76 per- 

 cent in 1986) is used for stainless steels. Chromium 

 is also used in nonferrous alloys and is essential in 

 the so-called "superalloys" used in jet engines and 

 industrial gas turbines. In 1984, about 3 percent 

 of the ferrochromium and pure chromium metal 

 used for metallurgy was for superalloys; less than 

 1 percent was used for other nonferrous alloys. 

 Chromium, along with cobalt, nickel, aluminum, 

 titanium, and minor alloying metals, enables super- 

 alloys to withstand high mechanical and thermal 

 stress and to resist oxidation and hot corrosion at 

 high operating temperatures. 



Chemical Uses. — Chromium-containing chem- 

 icals include color pigments, corrosion inhibitors, 

 drilling mud additives, catalysts, etchers, and tan- 

 ning compounds. Sodium dichromate is the pri- 

 mary intermediate product from which other 

 chromium-containing compounds are produced. 



Refractory Uses. — Chromite is used to produce 

 refractory brick and mortar. The major use for 

 refractory brick is for metallurgical furnaces, glass- 

 making, and cement processing. Use of chromite 

 in refractories improves structural strength and 

 dimensional stability at high temperatures. 



National Importance 



Chromium is considered to be a strategic mate- 

 rial that is critical to national security and poten- 



Table 3-3.— 1986 National Defense Chromium 

 Stockpile Goals and Inventories (as of Sept. 30, 1986) 



Inventory as 

 Material Goal Inventory percent of goal 



(thousand tons) 



Chromite: 



Metallurgical 3,200 1,874 59 



Chemical 675 242 36 



Refractory 850 391 46 



Ferrochromium: 



High-carbon 185 502 271 



Low-carbon 75 300 400 



Silicon 90 57 63 



Chromium metal . . 20 4 20 



SOURCE: J. Papp, "Chromium," Mineral Commodity Summaries— 1987 {Wast)- 

 ington, DC: U.S. Bureau of Mines, 1987), p. 35. 



tially very vulnerable to supply interruptions^* (ta- 

 ble 3-1 and 3-3). It is critical because of limitations 

 on substitutes for chromium in the vacuum-melted 

 superalloys needed for hot corrosion and oxidation 

 resistance in high-temperature applications and in 

 its extensive use in stainless steels. 



The Republic of South Africa accounted for 59 

 percent of total chromium imports (chromite ore, 

 concentrates, and ferroalloys) between 1982 and 

 1985. Other suppliers included Zimbabwe, which 

 provided 11 percent, Turkey 7 percent, and Yugo- 

 slavia 5 percent.^' The Republic of South Africa 

 and the U.S.S.R jointly led in world production 

 of chromite in 1986, producing about 3.7 and 3.3 

 million tons respectively, far ahead of the next 

 largest producer, Albania, with about 1 million 

 tons.^^ Some foreign producing countries, such as 

 Brazil, are producing and exporting ferrochromium 

 from chromite deposits which would not be com- 

 petitive in the world market if shipped as ore or 

 concentrate. However, by adding the value of con- 

 version to ferroalloy, both the Brazilian and the 

 Zimbabwe deposits remain competitive. 



Domestic Resources and Reserves 



The United States currently has no chromite re- 

 serves or reserve base. Domestic resources have 

 been mined sporadically when prices are high, or 



^'Office of Technology Assessment, Strategic Materials: Technol- 

 ogies to Reduce U.S. Import Vulnerability, p. 52. 



'^J. Papp, "Chrommm," Mineral Facts and Problems — 1985 Edi- 

 tion, Bulletin 675 (Washington, DC: U.S. Bureau of Mines, 1986), 

 p. 141. 



''J. Papp, "Chromium," Minerals Yearbook (Washington DC: 

 U.S. Bureau of Mines, 1985), p. 229. 



