444 



UNITED STATES MINERAL RESOURCES 



Niobium is utilized chiefly in the form of ferro- 

 columbium as an alloying element in carbon and 

 alloy steel, stainless steel, and superalloys. Of promi- 

 nence in recent years has been the inclusion of 

 niobium in high-strength low-alloy steels that are 

 used in the construction of large buildings, pipelines, 

 and machinery and structures where savings in 

 weight and increased durability and strength are 

 important factors. Niobium is added as a grain 

 refiner and stabilizer in some stainless steels and 

 variously improves the corrosion resistance, weld- 

 ability, or formability of the material. Niobium is 

 a common alloying addition to nickel-, iron-, or 

 cobalt-based superalloys that have use in high- 

 temperature and high-strength applications such as 

 gas-turbine components and hot-gas ducting in air- 

 craft. For example, niobium-based alloys are used 

 in rocket engines and superconductors, and unalloyed 

 niobium is used in currently classified nuclear appli- 

 cations, mainly in mill-product form. 



More than half of the tantalum produced is used 

 in the electronics industry, largely in the manufac- 

 ture of capacitors and rectifiers. The remainder goes 

 into the production of superalloys in high-tempera- 

 ture corrosion-resistant applications in aerospace 

 vehicles, into tantalum carbide for high-temperature 

 cutting tools, and into tantalum metal for a variety 

 of corrosion-resistant usages such as prosthetic de- 

 vices, chemical processing equipment, and liquid- 

 metal containment apparatus. 



Because niobium is principally used as a ferroalloy 

 element in steel, its consumption is tied closely to 

 the activities of the steel industry; a cutback in 

 steel production is reflected in a low consumption of 

 niobium. The consumption of tantalum is related 

 chiefly to the level of production in the electronics 

 industry. 



In many applications vanadium can be substituted 

 for niobium although some substitutions result in 

 deficiencies in certain mechanical properties such as 

 weldability in high-strength steel. Tantalum and 

 titanium are possible substitutes for niobium in 

 superalloys. 



Aluminum and ceramic materials can be substi- 

 tuted for tantalum in capacitors, with correspond- 

 ing tradeoffs among such things as durability, cost, 

 and size of units. Molybdenum and tungsten are 

 sometimes substituted for tantalum used in chemical 

 environments, and they may be actually superior in 

 some applications where halogens and halides are 

 involved; however, unlike tantalum, both have poor 

 weldability characteristics. 



Except for material released from the govern- 

 ment stockpile, the United States has imported all 



its niobium and tantalum since 1959. Some domestic 

 deposits are known and have been variably explored, 

 developed, or exploited, but none are commercially 

 productive at the present time. These metals are 

 imported mostly in the form of mineral concentrates 

 chiefly from Brazil, Canada, and Nigeria and other 

 African countries and in processed material in the 

 form of ferrocolumbium from Brazil and of tanta- 

 lum-bearing tin smelter slags from Malaysia. 



EXPLOITATION 



Limited demand for niobium and tantalum began 

 in the first quarter of the 20th century and a low 

 consumption continued until the World War II 

 period at which time critical shortages of both 

 niobium and tantalum developed (fig. 53). Tempo- 



1937 1940 1950 1960 1970 



Figure 53. — World production and U.S. imports of niobium- 

 tantalum concentrates, 1937-71. Data from U.S. Bureau 

 Mines (1938-72). Note: Ferrocolumbium included in im- 

 port data for 1964-68. Comparable data not available for 

 1970-71. One pound ferrocolumbium arbitrarily considered 

 equivalent to 2 pounds niobium ore concentrate. 



