Because it's been around for so long, dozens of industrial applications have been developed. The two basic types of this technology are direct and indirect resistance heating .
Electric resistance generates heat, which melts the metal.
For direct resistance to work, the metal must conduct at least a portion of the electric current. Direct resistance heating is used for heat treating, seam welding, forging, extruding, wire making, glass heating, and other purposes. Indirect Resistance Heating With this method, the electric current transfers heat to the metal by radiation, convection, or conduction. The resistance is created in the furnace's outer wall, and the furnace lining and interior vary depending on the target material. Typical furnace linings are ceramic, brick, and fiber batting, while furnace interiors can be air, inert gas, or a vacuum.