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전호로(electric arc furnace)
An electric arc furnace (EAF) is a furnace that heats charged material by means of an electric arc.
Arc furnaces range in size from small units of approximately one ton capacity (used in foundries for producing cast iron products) up to about 400 ton units used for secondary steelmaking. Arc furnaces used in research laboratories and by dentists may have a capacity of only a few dozen grams. Temperatures inside an electric arc furnace can rise to 1,800 degrees Celsius.
The first electric arc furnaces were developed by Paul Heroult, of France, with a commercial plant established in the United States in 1907. Initially "electric steel" was a specialty product for such uses as machine tools and spring steel. Arc furnaces were also used to prepare calcium carbide for use in carbide lamps.
Steelmaking furnace where scrap is generally 100% of the charge. Heat is supplied from electricity that arcs from the graphite electrodes to the metal bath. Furnaces may be either an alternating current (AC) or direct current (DC). DC units consume less energy and fewer electrodes, but they are more expensive.
The electric arc furnace offers an alternative method of bulk steel making. Unlike the basic oxygen route, the electric arc furnace does not use hot metal. It is charged with "cold" material which is normally steel scrap - which would otherwise be unsightly and environmentally damaging. Other forms of raw material are also available.
Steel scrap is first tipped into the electric arc furnace from an overhead crane. A lid is then swung into position over the electric arc furnace. This lid contains three graphite electrodes which are lowered into the electric arc furnace. An electric current is passed through the electrodes to form an arc. The heat generated by this arc melts the scrap.
During the melting process, other metals (ferro-alloys) are added to the steel to give it the required chemical composition. Also oxygen is blown in to the electric arc furnace to purify the steel
The modern electric arc furnace typically makes upto 150 tonnes in each melt, which takes around 90 minutes. Steel making with electric arc furnace is also economical. Every tonne of electric arc furnace steel uses about 7.4 GJ of energy compared with about 16.2 GJ for every tonne of BOS steel (7.4 GJ is still equal to the power consumption of a town of 100,000 population).