Steel factory with two arc furnaces
An arc furnace, also called an electric arc furnace or arc furnace, is an oven in which the material is heated by an arc between the electrodes and the material. The capacity of these ovens varies from a few grams on a laboratory scale to 400 tonnes for steel production.
The main application is in the steel industry, where usage has grown sharply due to the low investment costs and the flexible application for producing different high-grade steels. The oven can also work with 100% scrap as iron source. The oven is not a substitute for the blast furnace, since a blast furnace is used to make iron ore iron only. This iron, or otherwise reduced iron, can also be further processed into steel in the arc furnace. Disadvantages of the arc furnace are the high level of noise, dust production and energy consumption. An oven with a capacity of 35 tons (discharge charge) and a power supply of 50 MW has an average power of +/- 25,000 kW. Modern installations have a sound-proof casing and dust extraction to reduce the disadvantages.
The principle of the arc can be compared with the resistance welding of, for example, steel. A voltage source, DC or 3-phase AC voltage is used. In the case of direct voltage, the electrode is connected to one pole of the voltage source and the bottom of the furnace with the other pole. In case of alternating voltage, the three electrodes are connected to the three phases. By bringing the electrode (s) into contact with the material, a short-circuit current of several thousand amps occurs. As soon as the electrode (s) of the material is retracted, or the material melts, the arc arises. By keeping the distance between the electrode (s) and the material constant, the arc can be maintained. In the arc can the temperature rise to 7000 K (6726.85 ° C). The temperature control depends on the voltage applied, the current and the distance between the material and the electrode (s). Due to the very high temperature and its good control capability, many types of metal can be incorporated into this furnace. For the production of high-grade steels, substances such as tungsten, molybdenum or vanadium are added to the iron. In order to melt these substances in pure form and to bring them in a good connection with the iron, a very high temperature is required. This is possible on a laboratory scale in an arc furnace. On production scale, ferro alloys, iron alloys with the desired metal, are used, which melt at lower temperatures.
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