Bureau of Mines / Minerals yearbook: Metals, minerals, and fuels 1972
Year 1972, Volume 1 (1972)
Morning, John L.
Chromium, pp. 289-299 ff. PDF (1.1 MB)
298 MINERALS YEARBOOK, 1972 TECHNOLOGY Processes for the production of stainless steel continue to be developed and improved. Most of the processes utilize lower cost high-carbon ferrochromium rather than higher cost low-carbon ferrochromium. Joslyn Stainless Steel, a division of Joslyn Manufacturing and Supply Co. and a pioneer in the development of the argonoxygen decarburization (AOD) process, believes that it has perfected a process for substituting nitrogen for a significant part of the argon used in the process. Spartan Steel and Alloy Ltd. (United Kingdom) also found that nitrogen can partially replace the more expensive argon. Allegheny Ludlum, Inc., teamed up a basic oxygen furnace (BOF) with a hot blast cupola furnace at its Natrona, Pa., plant.6 Stainless steel scrap, high-carbon ferrochromium, and molybdenum oxide are cold charged to the BOF furnace to which the cupola hot metal is added. optimum charge rate has been 66.5% hot metaL Chromium recovery rates range from 88.7 to 92.5%. For the production of most nickel stainless steel grades, Allegheny utilizes a vacuuni refining process (AVR) which employs an electric furnace for melting and a vacuum refining unit. Decarburizing is achieved by injecting oxygen below the liquid metal surface while it is held at reduced pressure. Chromium yield in the AVR unit was reported at 98.1% and overall chromium recovery at 92.6%.7 Sweden's Uddeholm Steel Corp. developed a stainless steel process similar to the AOD process, but in place of argon to carry off the carbon monoxide, water vapor is injected through the furnace bottom. Reduced refractory wear is claimed; however, the process is limited to stainless grades containing less than 0.15% carbon. The firm reports a savings of $8 per ton in the manufacturing of stainless steel. Outokumpu Oy (Finland) continued to develop a process for the production of electrolytic chromium. Chromium metal containing 200 to 300 ppm oxygen, 20 to 40 ppm nitrogen, and 10 ppm sulfur was purified in bulk to less than 1 ppm oxygen, 5 ppm nitrogen, and less than 5 ppm sulfur. The material was then processed into a wrought bar by direct extrusion in an evacuated sheath.8 Small quantities of interstitial elements in chromium metal in the past has prevented processing commercial chromium metal to ductile metal. An improved electrorefining process was developed for the preparation of high-purity chromium with low-interstitial content. High-purity commercial chromium metal was electrorefined in a chromic chloride (CrCl2) electrolyte at cathode current densities of 40 to 210 amperes per square foot. Average current efficiency and chromium recovery were 96% and 99%, respectively.' Two new chromium plating processes were developed that could substantially reduce repair and salvage costs. The first was an electrolytic process that can be taken to the automobile bumper. The second was a hard chromium plating system primarily intended for use in moldmaking and tool and die operations for salvaging worn or mismatched parts. The Central Research Institute (India) reported the development of a self-regulating, high-speed chromium salt. The performance characteristics of the formulation demonstrate the following advantages over conventional plating: Higher production rate; formation of smoother, brighter, and harder deposits; less frequent need for accessories such as jigs; and elimination of control of critical constituents such as sulfate.10 Bureau of Mines researchers determined low-temperature heat capacities and hightemperature enthalpies calorimetrically for sodium chromate.l1 6 Iron Age. Chromium Recovery Improved in Stainless Refining. V. 209, No. 23, June 8, 1972, pp. 59—60. ° Work cited in footnote 6. 8 Sced. I. R. Production of High-Purity Wrought Chromium by Hydrogen Reduction and Extrusion Without Intermediate Melting. J. Less Common Metals, v. 27, No. 3, June 1972, pp. 261—267. ' Lei, K. P. V.. J. M. Hiegel, and T. A. Sulivan. Electrolytic Preparation of High-Purity Chromium. J. Less-Common Metals, v. 27, No. 3, June 1972, pp. 353—365. 10 Journal of Mines, Metals and Fuels. Formulation for High-Speed Chromium Plating. V. 20, No. 4, April 1972, p. 124. 11 Fcrrante, M. J., J. M. Stuve, and M. P. Krug. Low-Temperature Heat Capacities and High-Temperature Enthalpie, of Sodium Chromate. BuMines RI 7691, 1972, 12 pp.
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