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Induction heating is the process of heating a conductive material (i.e. metal or semiconductor) by electromagnetic induction, by transferring heat through an induction coil, within which an electromagnetic field is generated to heat and possibly melt steel, copper, brass, graphite, gold, silver, aluminum or carbide.An important feature of the induction heating process is that the heat is generated inside the object rather than from an external heat source by heat conduction.Objects can thus be heated very quickly.Also, no external contact is required, which can be important when contamination is an issue.Induction heating is used in many industrial processes such as heat treatment in metallurgy, Czochralski crystal growth and zone refining used in the semiconductor industry, and melting refractory metals requiring very high temperatures.Also for induction hobs.Induction heaters consist of an electromagnet and an electronic oscillator that passes high frequency alternating current (AC) through the electromagnet.The rapidly alternating magnetic field penetrates the object, creating currents called eddy currents inside the conductor.Eddy currents flow through the electrical resistance of the material and heat it through Joule heating.In ferromagnetic and ferrimagnetic materials such as iron, heat is also generated by hysteresis losses.Current frequency for induction heating depends on object size, material type, coupling (between working coil and object to be heated) and penetration depth.
Induction heating allows targeted heating of applicable items for applications including case hardening, melting, brazing and soldering, and heating to conform.Due to ferromagnetism, iron and its alloys respond best to induction heating.However, eddy currents can occur in any conductor, and hysteresis can occur in any magnetic material. Induction heating has been used to heat liquid conductors (such as molten metal) and gaseous conductors (such as gas plasmas Inductive Plasma Technology).Induction heating is commonly used to heat graphite crucibles (containing other materials) and is widely used in the semiconductor industry to heat silicon and other semiconductors. Mains frequency (50/60 Hz) induction heating is used in many low cost industrial applications as no inverter is required.
Induction furnaces use induction to heat metals to their melting point. After melting, a high-frequency magnetic field can also be used to stir the hot metal, which helps ensure that alloying additions are well mixed into the melt.Most induction furnaces consist of a water-cooled copper ring surrounding a refractory vessel.Most modern foundries use induction furnaces as a cleaner method of melting metal than reverberatory or cupola furnaces.Capacity varies from one kilogram to one hundred tons.Induction furnaces typically make a high-pitched whine or hum when they're running, depending on how often they're running.Molten metals include steel, copper, aluminum and precious metals.Because it is a clean and non-contact process, it can be used in vacuum or inert atmosphere.Vacuum furnaces use induction heating to produce specialty steels and other alloys that oxidize when heated in air.
A similar small-scale process is used for induction welding.Plastics can also be welded by induction if they are doped withferromagnetic ceramics (where the magnetic hysteresis of the particles provides the required heat) or metal particles.The seams of the pipes can be welded in this way.An electric current induced in the tube flows along the slit and heats the edges, resulting in a temperature high enough to weld. At this point, the seam edges are pressed together and the seam is welded.RF current can also be delivered to the tube via brushes, but the result is still the same current flows along the slit, heating it.
In the rapid induction printing metal additive printing process, the conductive wire raw material and protective gas are fed through the spiral nozzle, and the raw material is ejected from the nozzle in a liquid state after induction heating to form a three-dimensional metal structure under the shield.The core advantages of the procedural use of induction heating in this process are significantly improved energy and material efficiency and improved safety compared to other additive manufacturing methods such as selective laser sintering, which uses a powerful laser or electron beam .