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865:. If operated below the critical frequency, heating efficiency is reduced because eddy currents from either side of the workpiece impinge upon one another and cancel out. Increasing the frequency beyond the critical frequency creates minimal further improvement in heating efficiency, although it is used in applications that seek to heat treat only the surface of the workpiece.
503:, so it operates at low temperatures and has a long life. The frequency used ranges from 30 kHz down to 5 kHz, decreasing for thicker barrels. The reduction in the cost of inverter equipment has made induction heating increasingly popular. Induction heating can also be applied to molds, offering more even mold temperature and improved product quality.
922:(100–500) are easier to heat with induction heating. Hysteresis heating occurs below the Curie temperature, where materials retain their magnetic properties. High permeability below the Curie temperature in the workpiece is useful. Temperature difference, mass, and specific heat influence the workpiece heating.
351:
Seams of tubes can be welded this way. Currents induced in a tube run along the open seam and heat the edges resulting in a temperature high enough for welding. At this point, the seam edges are forced together and the seam is welded. The RF current can also be conveyed to the tube by brushes, but
360:
In the Rapid
Induction Printing metal additive printing process, a conductive wire feedstock and shielding gas is fed through a coiled nozzle, subjecting the feedstock to induction heating and ejection from the nozzle as a liquid, in order to refuse under shielding to form three-dimensional metal
478:
This ability can be used in hardening to produce parts with varying properties. The most common hardening process is to produce a localised surface hardening of an area that needs wear resistance while retaining the toughness of the original structure as needed elsewhere. The depth of induction
948:
The furnace consists of a circular hearth that contains the charge to be melted in the form of a ring. The metal ring is large in diameter and is magnetically interlinked with an electrical winding energized by an AC source. It is essentially a transformer where the charge to be heated forms a
309:
uses induction to heat 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
173:
An important feature of the induction heating process is that the heat is generated inside the object itself, instead of by an external heat source via heat conduction. Thus objects can be heated very rapidly. In addition, there need not be any external contact, which can be important where
474:
Induction heating can produce high-power densities which allow short interaction times to reach the required temperature. This gives tight control of the heating pattern with the pattern following the applied magnetic field quite closely and allows reduced thermal distortion and damage.
482:
Limits to the flexibility of the process arise from the need to produce dedicated inductors for many applications. This is quite expensive and requires the marshalling of high-current densities in small copper inductors, which can require specialized engineering and "copper-fitting."
429:
of containers in the food and pharmaceutical industries. A layer of aluminum foil is placed over the bottle or jar opening and heated by induction to fuse it to the container. This provides a tamper-resistant seal since altering the contents requires breaking the foil.
444:
Induction heating is often used to heat an item causing it to expand before fitting or assembly. Bearings are routinely heated in this way using utility frequency (50/60 Hz) and a laminated steel transformer-type core passing through the centre of the bearing.
410:
Induction brazing is often used in higher production runs. It produces uniform results and is very repeatable. There are many types of industrial equipment where induction brazing is used. For instance, Induction is used for brazing carbide to a shaft.
830:
is determined by the reference depth. Decreasing the reference depth requires increasing the frequency. Since the cost of induction power supplies increases with frequency, supplies are often optimized to achieve a critical frequency at which
549:
The frequency of the inductive current determines the depth that the induced eddy currents penetrate the workpiece. In the simplest case of a solid round bar, the induced current decreases exponentially from the surface. The penetration depth
387:
inside the cooktop heats the iron base of cookware by magnetic induction. Using induction cookers produces safety, efficiency (the induction cooktop is not heated itself), and speed. Non-ferrous pans such as copper-bottomed pans and
330:. Because it is a clean and non-contact process, it can be used in a vacuum or inert atmosphere. Vacuum furnaces use induction heating to produce specialty steels and other alloys that would oxidize if heated in the presence of air.
1161:. 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.
322:. Sizes range from a kilogram of capacity to a hundred tonnes. Induction furnaces often emit a high-pitched whine or hum when they are running, depending on their operating frequency. Metals melted include iron and
611:
289:). Induction heating is often used to heat graphite crucibles (containing other materials) and is used extensively in the semiconductor industry for the heating of silicon and other semiconductors.
281:
and soldering, and heating to fit. Due to their ferromagnetic nature, iron and its alloys respond best to induction heating. Eddy currents can, however, be generated in any conductor, and
348:
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.
499:
for injection and extrusion processes. Heat is directly generated in the barrel of the machine, reducing warm-up time and energy consumption. The induction coil can be placed outside
249:
of the electric current used for induction heating depends on the object size, material type, coupling (between the work coil and the object to be heated), and the penetration depth.
925:
The energy transfer of induction heating is affected by the distance between the coil and the workpiece. Energy losses occur through heat conduction from workpiece to fixture,
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can occur in any magnetic material. Induction heating has been used to heat liquid conductors (such as molten metals) and also gaseous conductors (such as a gas plasma—see
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in the pyrolysis of biomass. Heat is directly generated into shaker reactor walls, enabling the pyrolysis of the biomass with good mixing and temperature control.
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Relative depth varies with temperature because resistivities and permeability vary with temperature. For steel, the relative permeability drops to 1 above the
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Small workpieces or shallow penetration (e.g. steel at 815 °C with diameter of 5–10 mm or steel at 25 °C with a diameter around 0.1 mm).
654:
872:. Thus the reference depth can vary with temperature by a factor of 2–3 for nonmagnetic conductors and by as much as 20 for magnetic steels.
1030:
Sanchez
Careaga, FJ, Porat, A, Briens, L, Briens, C. Pyrolysis shaker reactor for the production of biochar. Can J Chem Eng. 2020; 1– 8.
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Induction heating is used by mechanics to remove rusted bolts. The heat helps remove the rust induced tension between the threads.
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Induction heating allows the targeted heating of an applicable item for applications including surface hardening, melting,
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Radio-frequency heating equipment, with particular reference to the theory and design of self-excited power oscillators
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hardened patterns can be controlled through the choice of induction frequency, power density, and interaction time.
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structures. The core benefit of the use of induction heating in this process is significantly greater energy and
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within the coil to heat up and possibly melt steel, copper, brass, graphite, gold, silver, aluminum, or carbide.
155:
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75:
728:. The equivalent resistance of the workpiece and thus the efficiency is a function of the workpiece diameter
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contamination is an issue. Induction heating is used in many industrial processes, such as heat treatment in
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material. Induction furnaces are used in most modern foundries as a cleaner method of melting metals than a
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to increase the reactive power. The alternating magnetic field induces eddy currents in the workpiece.
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Induction heating is often used in the heat treatment of metal items. The most common applications are
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as well as a higher degree of safety when compared with other additive manufacturing methods, such as
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is the process of heating electrically conductive materials, namely metals or semi-conductors, by
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single-turn short circuit secondary and is magnetically coupled to the primary by an iron core.
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is the frequency of the AC field in Hz. The AC field can be calculated using the formula
293:(50/60 Hz) induction heating is used for many lower-cost industrial applications as
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but very high current and high frequency. The workpiece to heat is placed inside an
940:. Diameter, shape, and number of turns influence the efficiency and field pattern.
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Application of high-frequency induction heating to high-quality injection molding
892:
Thick materials (e.g. steel at 815 °C with diameter 50 mm or greater).
27:
Process of heating an electrically conducting object by electromagnetic induction
17:
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the result is still the same—the current flows along the open seam, heating it.
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369:, which deliver heat to the material using a powerful laser or electron beam.
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Induction heating of 25 mm metal bar using 15 kW at 450 kHz.
802:. Since the workpiece diameter is fixed by the application, the value of
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The basic setup is an AC power supply that provides electricity with low
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Keeping silicon in crucible molten at 2,650 °F (1,450 °C) for
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Plastics
Engineering Annual Technical Conference Proceedings ANTEC 2010
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1045:"Ditch the Torch and Use Induction Heat to Break Free Rusted Bolts"
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driven by the power supply, usually in combination with a resonant
396:, the heat induced in the base is transferred to the food inside.
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1129:
Brown, George Harold, Cyril N. Hoyler, and
Rudolph A. Bierwirth,
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Magnetic materials improve the induction heat process because of
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This article is about
Induction heating. Not to be confused with
344:
A similar, smaller-scale process is used for induction welding.
238:
467:/brazing as a means of joining metal components, and induction
1133:. New York, D. Van Nostrand Company, Inc., 1947. LCCN 47003544
570:
in which 86% of power will be concentrated, can be derived as
36:
1159:
Radio-frequency induction heating of low-pressure plasmas
606:{\displaystyle \delta =503{\sqrt {\frac {\rho }{\mu f}}}}
1154:. 1st ed., Indianapolis, H. W. Sams, 1969. LCCN 76098943
936:
The induction coil is usually made of copper tubing and
209:(AC) through the electromagnet. The rapidly alternating
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that require very high temperatures. It is also used in
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1140:. London, G. Allen & Unwin, 1949. LCCN 50002705
67:. Unsourced material may be challenged and removed.
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127:Learn how and when to remove this message
1157:Sovie, Ronald J., and George R. Seikel,
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1147:. London, Pitman, 1949. LCCN 50001900
491:Induction heating is used in plastic
241:, heat also is generated by magnetic
221:. The eddy currents flow through the
147:is heated by induction during testing
7:
511:Induction heating is used to obtain
65:adding citations to reliable sources
383:In induction cooking, an induction
197:An induction heater consists of an
1032:https://doi.org/10.1002/cjce.23771
392:pans are generally unsuitable. By
213:penetrates the object, generating
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876:Applications of frequency ranges
768:, increasing rapidly up to about
1152:Abc's of radio-frequency heating
657:of the workpiece in ohm-meters,
225:of the material, and heat it by
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145:Stirling radioisotope generator
52:needs additional citations for
721:{\displaystyle {\frac {1}{T}}}
679:relative magnetic permeability
1:
1112:Elements of Induction Heating
1091:Elements of Induction Heating
1070:Elements of Induction Heating
1016:Society of Plastics Engineers
987:Handbook of Induction Heating
966:Handbook of Induction Heating
495:. Induction heating improves
425:Induction heating is used in
205:that passes a high-frequency
217:inside the conductor called
1110:S. Zinn and S. L. Semiatin
1089:S. Zinn and S. L. Semiatin
1068:S. Zinn and S. L. Semiatin
310:surrounding a container of
287:Induction plasma technology
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463:of steel parts, induction
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180:Czochralski crystal growth
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156:electromagnetic induction
1114:ASM International, 1988
1093:ASM International, 1988
1072:ASM International, 1988
633:is the depth in meters,
440:Induction shrink fitting
1138:Radio-frequency heating
626:{\displaystyle \delta }
563:{\displaystyle \delta }
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215:electric currents
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953:References
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243:hysteresis
223:resistance
176:metallurgy
158:, through
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665:μ
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590:ρ
578:δ
558:δ
507:Pyrolysis
469:annealing
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390:aluminium
295:inverters
247:frequency
1166:See also
613:, where
540:air coil
346:Plastics
164:inductor
1197:Heating
1122:page 16
1101:page 19
1080:page 15
1018:, 2010
997:page 92
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897:100–400
653:is the
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530:Details
513:biochar
415:Sealing
400:Brazing
373:Cooking
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301:Furnace
279:brazing
201:and an
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318:or a
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108:JSTOR
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991:ISBN
970:ISBN
889:5–30
385:coil
239:iron
233:and
182:and
80:news
905:480
584:503
305:An
63:by
1188::
1047:.
1014:,
933:.
194:.
178:,
1058:.
853:4
850:=
847:d
843:/
839:a
818:d
814:/
810:a
790:4
787:=
784:d
780:/
776:a
756:d
736:a
714:T
711:1
689:f
597:f
581:=
130:)
124:(
119:)
115:(
105:·
98:·
91:·
84:·
57:.
34:.
20:)
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