Ferroalloy

The metal looks like iron it exists in four allotropic modifications, stable over various temperature ranges. Although not easily attacked by air. it is slowly attacked by water and dissolves readily in dilute acids to give manganese(II) salts. The stable form of the metal at ordinary temperatures is hard and brittle—hence man ganese is only of value in alloys, for example in steels (ferroalloys) and with aluminium, copper and nickel. 

Submerged-Arc Furnace. Furnaces used for smelting and for certain electrochemical operations are similar in general design to the open-arc furnace in that they are usually three-phase, have three vertical electrode columns and a shell to contain the charge, but dkect current may also be utilised They are used in the production of phosphoms, calcium carbide, ferroalloys, siUcon, other metals and compounds (17), and numerous types of high temperature refractories. 

A typical large three-phase ferroalloy furnace using prebaked carbon electrodes is shown in Eigure 4. The hearth and lower walls where molten materials come in contact with refractories are usually composed of carbon blocks backed by safety courses of brick. In the upper section, where the refractories are not exposed to the higher temperatures, superduty or regular firebrick may be used. The walls of the shell also may be water-cooled for extended life. Usually, the furnace shell is elevated and supported on beams or on concrete piers to allow ventilation of the bottom. When normal ventilation is insufficient, blowers are added to remove the heat more rapidly. The shell also may rest on a turntable so that it can be oscillated slightly more than 120° at a speed equivalent to 0.25—1 revolution per day in order to equalize refractory erosion or bottom buildup. 

This product is mainly used within the ferroalloy plant as the reducing agent in a silicothermic process to produce the low carbon grade of refined ferromanganese. 

During the years 1981 to 1986, the average consumption of manganese units (as ferroalloys) for the EEC, the United States, and Japan combined, decreased from 6.5 to 5.5 kg/t of steel. Eor the same period in the United States, the consumption of manganese decreased from 6.2 to 4.7 kg/t of steel (33), and apparendy decreased further in the years of 1990, 1991, and 1992 to 4.15, 4.11, 3.85 kg/t of steef respectively (9). In contrast, in 1984, the steel industry of the former USSR, where 50% of steel production was stiU made in open-hearth furnaces, had an average consumption of manganese units of 13 kg/t steel (35). 

Plant Safety. Of the many ferroalloy products produced in electric furnaces, ferromanganese has the greatest potential for furnace emptions or the more serious furnace explosions. The severity of the explosions increases with the size of the furnace. Such incidents are infrequent, but can occur, and when they do are often disastrous. Explosions usually result in extensive damage to the furnace and surrounding area, and often severe injuries or death to personnel in the immediate area. An emption is the sudden ejection of soHds, Hquids, or gases from the furnace interior. A more violent and instantaneous ejection of material, accompanied by rapid expansion of burning gas, is considered an explosion (38). 

W. Gericke, "The Establishment of a 500,000 tpa Sinter Plant at Samancor s Mamatwan Manganese Ore Mine," Proceedings of the 5th International Ferroalloys Congress (fnfacon). New Orleans, La., Apr. 1989. 

P. L. Dancoisne, "Past and Present Evolution of the Manganese Demand," presented at 4th lEMFMMBM Ferroalloy Congress, Salvador de Bahia,... 

Ferroalloys Association 1612 K Street, NW Washington, D.C. 20006 Metal Powder Industries Federation P.O. Box 2054 Princeton, NJ 08540 Gold Institute 1001 Connecticut Avenue, NW Washington, D.C. 20036 Silver Institute 1001 Connecticut Avenue, NW Washington, D.C. 20036... 

Primary consumers for ferrous scrap are the iron and steel mills and foundries. Minor consumers iaclude ferroalloy producers, copper producers for use ia copper precipitation (see Recycling, nonferrous metals), and the chemical iadustry. The steel iadustry consumes about three-fourths of the total. Scrap consumption for ferroalloy production, copper precipitation, and the chemical iadustry total less than one million t. The United States is the leading exporter of ferrous scrap, exporting almost nine million t ia 1994, valued at about 1.3 biUioa. Total value of domestic scrap purchases and exports ia 1994 was 8 biUioa (2). 

The only new sihcon capacity since the early 1990s is by the Gulf Ferroalloys Company in Saudi Arabia. This plant is expected to have four furnaces and produce silicon metal, ferrosihcon, sihcomanganese, and manganese alloys by late 1996. 

Table 3. Ferroalloy Density and Thermal Effects on Steel Baths...

Rare-Earth Silicides. Rare-earth sihcides, in the form of a ferroalloy that contain up to 33% rare earths, are used increasingly by the iron and steel industries. Whereas the term sihcides is no longer used for alloys of this type, it is stih in common usage for these materials. Eor nodular iron, addition... 

P. deLinde, "EerrosiHcon Euture Production Trends," 10th International Ferroalloys Conference, Barcelona, Spain, Nov. 1994. 

The reaction temperature of 500—600°C is much lower than that required for the reductive chlorination. The volatile chlorides evolve from the molten salt bath. The boiling points of NbCl, TaCl, and WOCl He between 228 and 248°C. These compounds must therefore be separated by means of a distillation column. The chlorination of ferroalloys produces very pure tantalum pentachloride in toimage quantities. The TaCl contains less than 5 )J.g Nb/g Ta, and other metallic impurities are only amount to 1—2 lg/g Ta. 

Carburization by Menstruum Process. The P. M. McKenna method of caihuiization (1) involves the use of mineial concentrates such as wolframite [1332-08-7] Fe(Mn)WO, and microhte [12173-96-5] ferroalloys such as iron tungstide, FeW, or high purity scrap metals in a high... 

Menstruum Carburization. Mineral concentrates, ferroalloys, primary metals, or high, purity scrap may also be carburized (14). 

With the exception of carbon use in the manufacture of aluminum, the largest use of carbon and graphite is as electrodes in electric-arc furnaces. In general, the use of graphite electrodes is restricted to open-arc furnaces of the type used in steel production whereas, carbon electrodes are employed in submerged-arc furnaces used in phosphoms, ferroalloy, and calcium carbide. 

Various forms of carbon, semigraphite, and graphite materials have found wide apphcation ia the metals iadustry, particularly ia connection with the productioa of iroa, alumiaum, and ferroalloys. Carbon has been used as a refractory material siace 1850, though full commercial acceptance and subsequent rapid iacrease ia use has occurred only siace 1945. 

Table 4. Composition of Chromium Ferroalloys and Chromium Metal, wt...

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