Electric furnace
Electric furnace, A heated chamber that uses electricity as a heat source and is used to reach extremely high temperatures to melt and alloy metals and refractory materials. Electricity has no electrochemical effect on the metal, it simply heats it.
Modern electric furnaces
Modern electric furnaces are generally either arc furnaces or induction furnaces. A third type is the resistance furnace, still used to produce silicon carbide and electrolytic aluminum; in this type, the charge (i.e., the material to be heated) acts as the resistance element. In a resistance furnace, the current that produces the heat is introduced by electrodes buried in the metal. Heat can also be generated by resistance elements in the furnace lining.
Electric furnaces produce about two-fifths of the steel made in the United States. Specialty steel manufacturers use them to produce nearly all of the stainless steel, electrical steel, tool steel, and specialty alloys needed by the chemical, automotive, aircraft, machine tool, transportation, and food processing industries. Electric furnaces are also used exclusively by mini-mills, small plants that use scrap to produce rebar, commercial steel (such as angles and channels), and structural shapes.
The German-born British inventor Sir William Siemens first demonstrated the electric arc furnace at the Paris Exposition in 1879, using a crucible to melt iron. In this furnace, horizontally placed carbon electrodes strike an electric arc above a metal container. The first commercial electric arc furnace in the United States was installed in 1906; it had a capacity of 4 tons and was equipped with two electrodes. Modern furnaces range in heat from a few tons to 400 tons, with the arc striking directly from a vertically placed graphite electrode into a molten pool of metal. Although three-electrode, three-phase AC furnaces are commonly used, single-electrode, DC furnaces have recently been installed.
In an induction furnace, a coil carrying an alternating current is wrapped around a metal container or furnace. Eddy currents are generated in the metal (charge), and the circulation of these currents produces extremely high temperatures, causing the metal to melt and form an alloy of precise composition.