Within recent years, the melting of steel by the electric furnaces have developed rapidly for the availability of cheap electric power. Electricity is used solely for the production of heat and does not impart any special properties to the steel. Nevertheless, The electric furnace has the following advantageous features.
1. It generates extremely high temperature, about 2000*C , in the melting chamber without introducing oxygen or nitrogen from the air or impurities from the fuel. This facilitates the removal of the harmful impurities such as oxygen, Sulphur, and Phosphorus , and also non metallic inclusions.
2. The temperature at all times may be easily controlled and regulated.
3. It permits the additions of expensive alloying elements such as chromium , nickel , tungsten , etc. without loss by oxidation.
4. A great variety of steels, differing on carbon content and with any content of alloying elements , can be manufactured.
On account of the above considerations, high grade alloy steel, stainless and heat - resisting steels are made almost exclusively by that process. But this process is more expensive in operation than any other steel making process and the output is very low. When the average open- hearth surface can produce 800 tons of steel, The Bessemer converter about 1200 tons , the average electric furnace between 30 to 80 tons, every 24 hours. In the electric furnace process also both basics and acid methods are used. As in the previous processes, in the basic method, the lining is made of basic materials such as magnesite or dolomite, and in the acid process the lining consists of silica bricks.
Two types of electric furnaces used in manufacture of steel are :
(2) High - frequency Induction Furnace.
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