Electric Furnace Steel Production

Electric Furnace Steel Production

 

the production of steel in electric furnaces at metallurgical and machine-building plants. Steel intended for further conversion is melted primarily in arc furnaces having a basic refractory lining. There are several techniques used for electric melting in arc furnaces: melting with complete oxidation of impurities; remelting of alloying by-products without oxidation by means of gaseous oxygen; mixing of melts; and melting to an intermediate product (the duplex process).

The melting technique with complete oxidation of impurities covers three periods: melting, oxidizing, and reducing. During the oxidizing period impurities in the steel bath (P, Si, and other substances) are oxidized by adding solid oxidizing agents (iron ores, sinter, and the like) to the melt or by a blast of gaseous oxygen. The active boiling of the metal, produced by the formation of carbon dioxide bubbles as a result of decarburization, promotes rapid heating of the bath, degassing of the steel, and the elimination of nonmetallic inclusions. During the reducing period sulfur is removed from the melt, the steel is deoxidized, and the content of alloying elements is adjusted with ferroalloys.

Remelting the alloyed by-products without oxidation makes it possible to retain valuable, easily oxidized alloying elements (Cr and others), thus substantially improving production indicators. When high-chromium by-products are remelted with gaseous oxygen, the hot blast of the process (1800°–1900°C) ensures a low carbon content in the metal, which cannot be achieved when remelting without oxidation, and there is no appreciable loss of chromium. Methods for decarburizing high-alloy steels (corrosion-resistant steels and other types) outside the furnace are now common; the metal is blasted with argon-nitrogen-steam-oxygen mixtures in special converter-type refining units, or the oxygen may be degassed in a vacuum.

Electric melting may be intensified by reducing the melting period (by increasing the unit power of transformers, using gaseous oxygen burners, and preheating the charge), by using oxygen, by blasting the molten metal with powdered slag-forming materials, by shifting to a single-slag process, and by shortening the reducing period by using refining facilities outside the furnace (vacuum processing, blasting the metal with argon, and treating the steel with synthetic slags).

Arc furnaces with an acid refractory lining are used primarily to produce steels intended for casting molds. The high resistance of oxide slags (saturated SiO2) permits rapid heating of the metal to a high temperature, which is important in the casting of thin-walled objects. A major drawback of the acid electric arc process is that phosphorus and sulfur cannot be removed from the steel.

SeeSTEEL PRODUCTION and for discussions of steel melting in induction furnaces and the methods of special-purpose electrometallurgy as well as the position and importance of electric furnace steel production with respect to other processes.

REFERENCES

See references under .

V. A. PRIGORIAN

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