Induction furnace
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An induction furnace (IF) is an electrical furnace in which the heat is applied by induction heating of the metal charge.[1][2][3] Since no arc is required like and electric arc furnace or combustion is used like in a basic oxygen furnace, the temperature of the material is no higher than required to melt it, preventing loss of valuable alloying elements.[4][5] The induction furnace is a relatively clean, energy-efficient and well-controlled method of melting, which is used for steel, copper, zinc, and aluminum.[6][5]
The Process
Induction furnaces work based on two principles: Electromagnetic induction and Joule effect.[7][8] Faraday's law of Electromagnetic Induction predicts how a magnetic field interacts with an electric circuit to produce electromotive force. Accordingly, any electrically conductive material placed in a variable magnetic field becomes the site of induced electric currents. Joule heating, also known as Ohmic heating or resistive heating, is the process by which an electric current passing through a conductor generates heat due to the resistance offered by the material.[7][9]
Induction Furnaces are electrically powered furnaces that use the principle of electromagnetic induction to heat and melt metal. An alternating current is passed through a coil of copper tubing that generates a magnetic field. When metal is placed inside the coil, the magnetic field induces electric currents called eddy currents within the placed metal. The induced eddy current heats the metal which eventually results in the melting of the metal.[10]
Types
Induction Furnaces are classified broadly into two types: Core- or Channel-type and Coreless-type.[5][6] In a core- or channel-type IF, an alternating current flows through a primary coil which surrounds an iron core. A loop of molten metal forms a single-turn secondary coil that surrounds the iron core and primary coil. Current passing through the primary coil induces a large current in the secondary coil, generating heat via Joule Effect. In this method, the metal loop needs to be maintained continuously and is rarely permitted to cool. The channel-type furnace allows high throughput, high production operations requiring few alloy changes, and continuous casting schedules.[5]
In a coreless IF, the metal charge is placed in a crucible surrounded by a water-cooled alternating current solenoid coil, which constitute the primary coil.[6] The primary coil induces a current directly in the metal charge. The secondary coil is dispensed with in a coreless IF. This type of IF can be shut down and started cold. It is highly flexible to be operated across a range of frequencies, from 50 Hz to 10 kHz. However, the power efficiency is reduced when compared to a channel furnace (a 75% power efficiency approximately) because of the absence of a flux-concentrating core. Smaller coreless furnaces operate at higher frequencies, maintaining their efficiency and promoting a vigorous stirring action. Frequent alloy changes and recurring cooling and heating also tend to reduce the operating life of the refractory lining.[5]
Limitations
The one major drawback of induction furnace is its lack of refining capacity. The charge materials used in an induction furnace must be free of oxides and be of a known composition, and some alloying elements may be lost due to oxidation, so they must be re-added to the melt.[6]
References
- ↑ Laughton, M. A.; Warne, D.F. (2002). Electrical Engineer's Reference Book, 16th Ed. Newnes. pp. 17–19. ISBN 0080523544.
- ↑ Campbell, Flake C. (2013). Metals Fabrication: Understanding the Basics. ASM International. pp. 63–65. ISBN 978-1627080187.
- ↑ Bauccio, Michael (1993). ASM Metals Reference Book, 3rd Ed. American Society for Metals. p. 50. ISBN 0871704781.
- ↑ Phillip F. Ostwald, Jairo Muñoz, Manufacturing Processes and Systems (9th Edition), John Wiley & Sons, 1997 ISBN 978-0-471-04741-4 page 48
- ↑ 5.0 5.1 5.2 5.3 5.4 "How Does and Induction Furnace Work?". www.ceramicsrefractories.saint-gobain.com. 2023-07-19. Retrieved 2024-03-27.
- ↑ 6.0 6.1 6.2 6.3 "Induction furnace". Wikipedia. Retrieved 27 March 2024.
{{cite web}}: CS1 maint: url-status (link) - ↑ 7.0 7.1 "ELECTRIC INDUCTION FURNACE". Retrieved 2024-03-27.
- ↑ "Operating Practices for Induction Furnace". www.jsautocast.com. Retrieved 2024-03-27.
- ↑ "What is Induction?". Inductotherm Corp. Retrieved 2024-03-27.
- ↑ Induction, Electroheat (2013-11-28). "Channel Induction Furnace vs. Coreless Induction Furnace: What's the Difference?". Electroheat Induction. Retrieved 2024-03-27.
External links
- Induction furnace - Britannica
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