An electric furnace is an enclosed structure that uses electricity as a
heat source to produce high temperatures for industrial purposes. In
these furnaces, electricity is used to generate the heat and then push
the air out through the central system. These furnaces can be made with
several kinds of heat resistant (refractory) elements in order to
withstand long term use. The enclosed space holds the materials, gas or
air being heated until the desired temperature is reached, as measured by an external sensor.
Electric furnaces can come with numerous temperature control options or be set for a single temperature, depending on the process for which the furnace will be used. To increase heat, pulverized coal and oxygen are often added to the electric heat. Electric furnaces commonly have one of the following atmospheres: air or oxidizing, inert, reducing, salt bath or vacuum. They also come in three-zone or multi-zone varieties. Over-temperature protection, service or entry holes, view ports, computer interface and application software are other optional features available for electric furnaces. A common electric furnace is the electric arc furnace which is typically used for making steel from scrap material. Scrap metal is placed in the electric arc furnace in varying layers (of light-gauge steel and large heavy steel); as the arcs heat up they heat through the layers of the metal, lengthening the arcs and increasing the melting process. Further acceleration can occur when oxygen is added to the process.
Advantages to electric furnaces are that they provide precision control when it comes to the temperature and internal atmosphere of the furnace. They are also considered more economical because they can re-use scrap metal. Important factors to consider when selecting an electric furnace are pressure range, process temperature, chamber length, and the height, width, or tube outer diameter of the furnace. Pressure range is the range of pressure the furnace can run on, while the process temperature represents the range of temperatures that the furnace can handle. The length of the chamber is the length of the furnace itself. Height and width refer to internal measurements of the furnace. Tube outer diameter is another measurement that affects the performance of tube furnaces, a particular variety of electric furnaces.