Induction Furnace

(also induction melting furnace), an electrothermal device for melting materials by induction heating. Crucible and channel induction furnaces are most commonly used in industry.

A crucible induction furnace consists of an induction heater in the form of a solenoid made from water-cooled copper tubing and a crucible, which, depending on the properties of the melt, may be made of ceramic materials or in special cases may be graphite or steel. Crucible furnaces are used in melting steel, cast iron, precious metals, copper, aluminum, and magnesium. They are manufactured with crucible capacities ranging from a few kilograms to dozens of tons. They may be constructed as open, vacuum, gas-filled, or compressed-gas furnaces. The current supplied to the furnace can be low-, medium-, or high-frequency.

The main components of a channel furnace are a melting bath and a so-called induction unit, which consists of a hearthstone, a magnetic core, and an inductor. Channel furnaces differ from crucible furnaces in that the conversion of electromagnetic energy to thermal energy occurs in a heat evolution channel, which must be continuously filled with an electrically conductive body. For the first start-up of a channel furnace, molten metal is poured into the channel, or a pattern made of the material to be melted is placed in the channel. After melting is completed, the furnace is emptied incompletely, leaving a “swamp” to ensure that the heat evolution channel is filled for the next start-up. In modern furnaces the induction unit is removable to facilitate replacement of the hearthstone.

Channel furnaces are used for melting nonferrous metals and their alloys, as well as cast iron. The capacity of the melting bath of a furnace ranges from a few hundred kilograms to several hundred tons; the current is supplied at industrial frequency. Melting in induction furnaces is characterized by relatively cold slag, since heat is released in the melted metal; by high output of the process; and by intensive mixing and high quality of remelted metal. Induction furnaces are used for remelting and refining metals, and also as mixers (forehearths) for storage and reheating of lquid metal before casting.