Tantalum and Niobium A Staff-Industry Collaborative Report
DONALD J. SOISSON, Assistant Editor in collaboration with
J. J. McLAFFERTY, Fansteel Metallurgical Corp., Muskogee, Okla., and JAMES A. PIERRET, Fansteel Metallurgical Corp., North Chicago, 111.
Moving to ensure its share of the increasing markef for these two refractory metals, Fansteel Metallurgical has developed a
liquid-liquid extraction proeess that doubles production rates over the original process, gives metals over
99.9% pure
T A N T A L U M , atomic number 73, is a member of Group V in the periodic table. I t does not occur in nature in the free state. Found in a number of minerals, it is usually associated with niobium. Niobium is also a member of Group V, has atomic number 41. I t is usually called columbium by the metallurgy industry. Both metals-with their high melting points and good corrosion resistance-are excellent refractory metals. Both metals derive their name from ancient Greek mythology. Tantalus was the son of Zeus, had a daughter named Niobe. He was sentenced to the eternal punishment of being tantalized with food and water just out of his reach. Similarly, early chemists were “tantalized” with these strange elements which they could name easily enough but could not isolate (6). The first commercial producer of tantalum in the United States was Fansteel Metallurgical Corp., North Chicago, Ill. In 1922, the late Dr. C. W. Balke, director of research at Fansteel, succeeded in making ductile tantalum bars (7). And until 1956, Fansteel had much of the tantalum field to itself. At this time, Kawecki Chemical entered the picture and is now the other principal producer of tantalum. Also making the metal now are Kennametal, National Research, Union Carbide Metals, and Wah Chang (77).
Fansteel has been producing niobium since 1929. Other producers of this metal include D u Pont, Union Carbide Metals, and Wah Chang. Wah Chang is the largest one, turns out over 75y0 of the niobium produced in the United States (77).
Ta, Nb Properties Surpass M a n y Other Refractory Metals Tantalum has a myriad of useful properties. I t melts at 2996’ C. (5425’ F.), thus ranks behind only tungsten and rhenium among the refractory metals. I t almost completely resists chemical attack, is on a par with glass in its immunity to acids. Only two acids-hydrofluoric and fuming sulfuric -or strong alkalies will attack the metal. These properties make it suitable for chemical processing equipment and for use as surgical implants. Tantalum’s thermal conductivity (0.130 at 20’ C.) is higher than that of glass, about the same as that of steel. Thus, it is ideal for heat transfer surfaces in acid or other corrosive surroundings. I n ductility, workability, and weldability, it surpasses most other refractory metals. It can be drawn, stamped, or spun like steel. Annealed tantalum won’t spring back when stamped or forged. In addition, the metal workhardens slowly, will not age-harden. Two rather unusual properties make VOL. 53, NO. 11
NOVEMBER 1961
861
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-with water. The product is dried in a stainless steel, steam-jacketed dryer (.?E)
Sintering and Reclaiming at Muskogee, Too For making ingots, the tantalum powder is first pressed into 20-pound bars, These bars are sintered in a furnace at a vacuum (7E) of less t h a n 5 microns and a little below tantalum's melting point. The vacuum furnaces were designed and built by Fansteel. The tantalum bars are held between water-cooled terminals in the furnace and are heated by passing an electric current through them. After sintering, the bars are shipped by rail or truck to Fansteel's North Chicago plant for rolling and fabrication, The Muskogee plant also carries on a tantalum reclaiming operation. Trimmings from rolling and s'ntering operations and clean customer scrap are reworked this way: The scraps are reacted with pure hydrogen gas at red heat to form the brittle metal hydride. Then the tantalum is pulverized in a Raymond hammer mill (QE) to -120 mesh. The tantalum powder is washed with hydrochloric acid to remove iron picked u p during processing. Finally, it is degassed to remove hydrogen by heating in vacuum a t 1200O to 1400' F. This product is then ready for pressing and sintering.
.Staff-Industry the press and packed in 6-inch silica crucibles. To remove the last traces of water, and convert to high purity Nbz06, the cake is calcined a t 1600' to 1800O F. Final processing of the niobium pentoxide to elemental niobium is done at the North Chicago plant. The oxide is blended with carbon, pressed into a slug, then reacted a t above 1600' C. in vacuum to produce the metal. T h e resulting spongelike metal is reacted with hydrogen to make it brittle. Next, it is pulverized in a Raymond mill, washed with hydrochloric acid, and degassed under vacuum. The finished metala fine powder-is then ready for pressing and for sintering. Sintering is conducted a t 2000' to 2150' C. under vacuum to remove interstitial oxygen, carbon, and nitrogen.
Plant Has Room for Expansion
From Fluoride Solution to Niobium The high purity niobium raffinate (99.9+% pure) is pumped from the fourth mixer-settler box to 3000-gallon, rubber-lined, steel tanks (723). Anhydrous ammonia is added to convert the niobium to hydrated niobium pentoxide (Nb2O6.xHp0)-a white, amorphous precipitate. The mother liquor is pumped off and the precipitate washed with deionized water to remove fluorides. Wash water containing fluorides is siphoned off. This slurry is dropped from the tanks to a wood plate and frame filter press (7UE). Excess water is removed by air, and the resulting cake is scraped from
Fansteel's $6,500,000 tantalum-niobium plant at Muskogee was built to augment the output of the company's North Chicago facility. Recognizing niobium's potential and the growing need for more tantalum, Fansteel initiated a $1,000,000 expansion program at its North Chicago plant in 1955. The program was under way only a few months when Fansteel, realizing that more production facilities were necessary, began to look for a new site. The company evaluated over 150 possible sites before it finally selected a 113-acre tract on the west bank of the Arkansas River, just outside Muskogee, Okla. Ground was broken in 1956, and the plant went on stream in the fall of 1957. The Muskogee plant consists of three principal buildings: chemical, sintering, and service. These structures add up to more than 95,000 square feet of floor space. The chemical building houses production facilities and laboratories for quality control and process development.
Quartograph i s used to determine purity of products
T o ensure purity of product and to guide processing, Fansteel chemists check the product in various stages of the process. I n addition to the ore itself, they analyze samples from the liquid-liquid separation and from the electrolysis steps. Finally, they analyze the finished sintered bar for other metals and for interstitials. T h e service building houses storage and maintenance facilities plus the administrative offices. In the sintering building, sintering and reclaimed tantalum operations are conducted. The liquid-liquid separation is run in a smaller building separated from the others because of the inflammable nature of the materials used. All the solvent extraction equipment is housed in this building. Facilities are also provided for bulk storage of chemicals. The chemicals are brought in by rail, stored in large tanks. T h e tanks hold up to 12,000 gallons of hydrofluoric acid and ketone, respectively, and u p to 20,000 gallons of sulfuric acid, potassium hydroxide, and hydrochloric acid, respectively.
Available in M a n y Shapes Fansteel is currently offering tantalum in a variety of forms. These include powder, ingots, briquettes, billets, plate, sheet, foil, rod, wire, ribbon, and tubing. T h e company makes such tantalum chemical processing equipment as bayonet heaters, coils, condensers, heat exchangers, and thermowells. And it also fabricates the metal to customer specifications. A number of tantalum alloys are supplied by Fansteel. Tantalloy (tantalum-tungsten) and Fansteel 82 (niobium-tantalum-zirconium) are two of the most widely used. Niobium is supplied as sheet, bar, rod, tubing, wire, foil, powder, ingot, and fabricated parts. T h e company also
Product i s checked through various stages of process
produces tungsten alloys of the metal.
and molybdenum
Bright Future United States tantalum production was 150 tons last year, u p from 122 tons in 1959 (10). Niobium production more than doubled, going from about 70 tons in 1959 to about 150 tons in 1960. T h e outlook for both metals continues to be a rosy one. Tantalum use in electronic devices is increasing. Applications in the fields of cryogenics and high temperature alloys are on the upswing. More niobium is going into steel. nonferrous alloys (including those with a niobium base), and nuclear applications. Of these, the alloys field looks the most promising. New uses that should boost demand for niobium still higher are high temperature alloys for gas turbines, jet engines, missiles. and aircraft structural uses; corrosion and heat resistant steels; and special steels for construction machinery, ship hulls, and impact resistant parts, such as aircraft landing gear (9). The future will not be without its problems, though, according to Fansteel’s president, E. T. Collinsworth, Jr. “There is a n indication that the exotic appeal of this business is enticing new producers to the extent that it will probably lead to an over capacity for an indeterminate period. This could result in profit margins much less than expected.” “As in many industries today, those companies with the most aggressive mar-
Chemicals used in process are bulk stored in these tanks
keting, backed by the best technical talent, \vi11 survive to enjoy the longterm expected increase in the market in the coming years.”
literature Cited (1) Balke, C. W., IND. ENG. CHEM.27, 1166 (1935). (2) “%cyclopedia of Chemical Technology, Vol. 13, p. 600, Interscience, New York, 1954. (3) Zbid.,p. 601. (4) Fansteel Metallurgical Corp., North
Chicago, Ill., “Fansteel Metallurgy,” 1958. ... (5) Zbid.,’“Fansteel Tantalum.” (6) Ibid., ”The Metal Tantalum.” 1953. (7) , , Placek, C., Taylor, D. F., IND.END. CHEM.48, 686-93 (1956). (8) Spedding, F. H., Daane, A. H.: Met. Reus. 5 , No. 19, 302 (1960). (9) U. S. Bureau of Mines, “Mineral Facts and Problems,’‘ Bull. 585, 1960. (IO) Zbid., Mineral Market Report, MMS No. 3228, 1961. (11) Zbid., preprint from “Minerals Yearbook,” Vol. 1, p. 2, 1959. (12) Werning, J. R.? Hibbie, K. B., others, IKD.EKG.CHEM.46, 644-54 (1954). (13) Wilhelm, H. A., Kerrigan, J. V. (to U.S.A., Atomic Energy Commission), U. S. Patent 2,767,047 (Oct. 16, 1956). .Tanuarv ...~ ~
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Processing Equipment
Hydrostatic pressing of metal powders is shown here
868
INDUSTRIAL AND ENGINEERING CHEMISTRY
(IE) American Hard Rubber Co., Div. of Arnerace Corp., 7 Ace Rd., Butler, N. J., rubber-lined steel tank. (2E) Belke Manufacturing Go., 951 N. Cicero Ave., Chicago 51, Ill., steamjacketed dryer. (3E) Big-Four Foundry Co., Inc., 621 E. Cameron, Tulsa, Okla., electrolysis pots. (4E) Denver Equipment Co., 1661 Market St., Denver 17, Colo., concentrating table. (5E) Globe Div., Casalbi Co., Wayne and Sparks, Jackson, klich., tumbling barrels. (6E) Hardinge Co., Inc., 240 Arch St., York, Pa., ball mill. (7E) Xational Research Corp., 70 Memorial Drive, Cambridge, Mass., oil diffusion vacuum pumps. (8E) Patterson Foundry 8r Machine Co., 41 Helene St., East Liverpool, Ohio, rotary dryer. (9E) Raymond Div., Combustion Engineering, Inc.: 1118 W. Blackhawk St., Chicago 22, Ill., hammer mill. (10E) Sperry, D. R., & Co.: Batavia, Ill., plate-and-frame filter press. (11E) Syntron Co., 1938 Black St., Homer City, Pa., air-driven feeder. (12E) Tolhurst Centrifugals Div., American Machine & Metals, Inc., 48 Thomas St., East Moline, Ill., centrifuge.
