An arc furnace is a general term for electric melting furnaces that generate heat by means of an electric arc. Depending on how the arc transfers its heat to the charge, arc furnaces are divided into two design families: furnaces with indirect arc heating and furnaces with direct arc heating.
In furnaces with indirect arc heating, such as the graphite rod furnace, the arc burns between electrodes positioned above the charge and heats the material indirectly, mainly through radiation. In furnaces with direct arc heating, such as the three-phase AC arc furnace and the DC arc furnace, the arc burns directly between the electrode or electrodes and the metal charge, transferring heat straight into the material.
Use of arc furnaces in foundries and steelworks
Arc furnaces with direct arc heating are widely used in foundries and steelworks for melting steel scrap and producing steel alloys. Three-phase AC arc furnaces and DC arc furnaces are the standard furnace types for electric steelmaking, where they melt scrap into liquid steel that is subsequently refined and cast. The choice between the AC and DC design depends on factors such as electrode consumption, arc stability, and the specific production process at hand.
Both AC and DC arc furnaces are supplied with power through dedicated furnace transformers, which adapt the electrical grid voltage to the requirements of the arc process. The furnace lining protects the vessel from the high thermal and mechanical loads created by the arc and the molten metal. For a comparison with other melting technologies, see our articles on induction melting and on melting time.
Comparison of arc furnace types
| Furnace type | Heating principle | Electrode arrangement | Typical application |
|---|---|---|---|
| Graphite rod furnace | Indirect arc heating | Arc burns between electrodes positioned above the charge | Melting applications where indirect, radiant heating is required |
| Three-phase AC arc furnace | Direct arc heating | Three electrodes connected to a three-phase AC supply | Melting of steel scrap in steelworks and foundries |
| DC arc furnace | Direct arc heating | Single electrode with a bottom (hearth) anode | Melting of steel scrap in steelworks and foundries |
Frequently asked questions
What is the difference between direct and indirect arc heating?
In direct arc heating, the electric arc burns directly between the electrode and the metal charge, transferring heat straight into the material, as in three-phase AC and DC arc furnaces. In indirect arc heating, such as in the graphite rod furnace, the arc burns between electrodes above the charge, and heat reaches the material mainly through radiation.
What is an arc furnace used for?
Arc furnaces are mainly used in foundries and steelworks to melt steel scrap and to produce steel alloys. Three-phase AC and DC arc furnaces are the standard furnace types for electric steelmaking.
What is a graphite rod furnace?
A graphite rod furnace is an arc furnace with indirect arc heating. The arc burns between graphite electrodes positioned above the charge, and the heat generated is transferred to the material mainly by radiation rather than by direct contact with the arc.