Ferroalloy Manufacture

Ferroalloy Manufacture 

the manufacture of ferroalloys in specialized metallurgical plants. The electrothermal (electric-furnace) method for the production of ferroalloys (electroferroalloys) is the most common. The two variations of this method, which derive from differences in the type of reducing agent, are the carbon-reduction method, which is used for the production of high-carbon ferroalloys (5–8 percent C) and all silicon alloys, and the thermal reduction method (by convention including the silicothermic method), which is used in the production of alloys with a reduced carbon content (0.01–2.5 percent C).

The carbon-reduction process is carried out mainly in ore heat-treating furnaces with a power of 16.5–72 megavolt-amperes. It is used to produce ferrosilicon, crystalline silicon, aluminum-silicon alloy, calcium-silicon, ferrosilicocalcium, silicomanganese, ferrochrome silicon, high-carbon ferromanganese and ferrochromium, ferrophosphorus, and complex silicon-base alloys, as well as low-phosphorus manganese slag. Production in blast furnaces is insignificant and is continually decreasing (low-grade ferrosilicon and ferromanganese) since the alloys contain a higher proportion of impurities and are more expensive than electroferroalloys.

Low-carbon (purified) ferroalloys are produced in arc (refining) furnaces with a power of 2.5–5.5 megavolt-amperes by thermal reduction methods. The silicothermic method is used for low-carbon and carbon-free alloys of manganese and chromium and for ferrovanadium (aluminum being added to the charge), ferrotungsten (coke breeze being added), and zirconium ferrosilicon. Metallic chromium, carbon-free ferrochromium, ferroniobium, and ferroboron are produced by the aluminothermic method, as are zirconium ferrosilicon and various hardeners with rare and rare-earth metals.

Medium-carbon ferrochromium is also obtained in converters through the use of an oxygen current; the starting material here is high-carbon ferrochromium. Resistance furnaces and induction furnaces are used to produce nitrogen-containing (nitrided) alloys of manganese, chromium, and vanadium.

Ferrotitanium and metallic chromium and vanadium are produced by nonfurnace aluminothermic reactions; ferromolybdenum is produced through a nonfurnace silicothermic reaction involving the addition of aluminum to the charge.

Approximately 97 percent of the ferroalloys produced in the USSR (exclusive of ferrophosphorus) are alloys with silicon, manganese, and chromium. The production of these alloys is expensive with regard to both materials and energy costs and is usually organized in places where ore is plentiful and electric power is inexpensive.

REFERENCES

Proizvodstvo ferrosplavov, 2nd ed. Moscow, 1957.
Ryss, M. A. Proizvodstvo ferrosplavov. Moscow, 1957.
Shchedrovitskii, Ia. S. Proizvodstvo ferrosplavov v zakrylykh pechakh. Moscow, 1975.
Durrer, R., and H. Volkert. Metallurgiia ferrosplavov, 2nd ed. Moscow. 1976. (Translated from German.)

V. A. BOGOLIUBOV