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Induction heating

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Image:Plustherm induction heater.jpg

Induction heating is the process of heating a metal object by electromagnetic induction, where eddy currents are generated within the metal and resistance leads to Joule heating of the metal. An induction heater (for any process) consists of an electromagnet, through which a high-frequency AC is passed. Heat may also be generated by magnetic hysteresis losses.

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[edit] Applications of induction heating

Induction heating allows the precision heating of an applicable item, for applications from surface hardening to melting. Often, iron and its alloys respond best to induction heating, due to their ferromagnetic nature. Eddy currents can, however, be generated in any metallic conductor, and magnetic hysteresis can occur in any magnetic material.

[edit] Induction furnace

An induction furnace uses induction to heat a metal to its melting point. Once molten, the high-frequency magnetic field can also be used to stir the hot metal, which is useful in ensuring that alloying additions are fully mixed into the melt. Most induction furnaces consist of a tube of water-cooled copper rings, surrounding a container of refractory material. Induction furnaces are used in most modern foundries, as a cleaner method of melting metals than a reverberatory furnace or a cupola. Sizes range from a kilogram of capacity, to a hundred tonnes capacity. Induction furnaces often emit a high-pitched whine or hum when they are running, depending on their operating frequency. Metals melted include iron and steel, copper, aluminium, and precious metals.

[edit] Induction welding

A similar, smaller-scale process is used for induction welding. Plastics may also be welded by induction, if they are either doped with ferromagnetic ceramics (where magnetic hysteresis of the particles provides the heat required) or by metallic particles.

[edit] Induction cooking

In induction cooking, an induction coil in the cook-top heats the iron base of cookware. Copper bottomed pans, aluminium pans and most stainless steel pans are not suitable.

The heat induced in the base is transferred to the food via conduction. Benefits of induction cookers include efficiency, safety (the induction cook-top is not heated itself) and speed. Drawbacks include the fact that non-ferrous cookware such as copper, aluminium and glass cannot be used on an induction cook-top. Both installed and portable induction cookers are available.

[edit] Induction sealing

Induction heating is often used in Induction sealing or "cap sealing".

[edit] Heat treatment

Induction heating is often used in the heat treatment of metal items.

[edit] Further reading

  • Shields, John Potter, Abc's of radio-frequency heating. 1st ed., Indianapolis, H. W. Sams, 1969. LCCN 76098943
  • Hartshorn, Leslie, Radio-frequency heating. London, G. Allen & Unwin, 1949. LCCN 50002705
  • Langton, L. L., Radio-frequency heating equipment, with particular reference to the theory and design of self-excited power oscillators. London, Pitman, 1949. LCCN 50001900
  • Sovie, Ronald J., and George R. Seikel, Radio-frequency induction heating of low-pressure plasmas. Washington, D.C. : National Aeronautics and Space Administration ; Springfield, Va. : Clearinghouse for Federal Scientific and Technical Information, October 1967. NASA technical note. D-4206; Prepared at Lewis Research Center.
  • Brown, George Harold, Cyril N. Hoyler, and Rudolph A. Bierwirth, Theory and application of radio-frequency heating. New York, D. Van Nostrand Company, Inc., 1947. LCCN 47003544

[edit] External links

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