In our industry, many resources are available to find information on a variety of technologies. IHEA is one of those resources, and this induction article was graciously contributed by them.
Industrial processes use a wide range of heating technologies to accomplish various effects on manufactured products. IHEA has several technical divisions, and one of these focuses on induction.
Induction, as the name implies, induces a high-frequency electrical alternating current into a workpiece, causing it to heat up. The workpiece does not have to be magnetic, but it must be conductive. Induction can be used for both heating and melting.
The basic components of an induction heating system include a power supply, an induction coil, workpiece material handling and a cooling system. The basic components of an induction melting system include a power supply, a channel or coreless furnace, material-handling equipment and a cooling system.
Why Use Induction?
There are several reasons to use induction heating technology.
- Directed, precise heating: Only heats the portion of the workpiece that needs to be heated
- Fast heating: Much faster than other techniques, with pinpoint temperature control
- Energy-efficient: Instant on/instant off and precision minimize wasted energy
- Clean: The coil does not touch the workpiece, no residue
- Superior repeatability: Limited process variability, good quality
- Flexible: Good for many different shapes and sizes, numerous applications
One of the key components for induction heating is the induction coil. The induction coil is the part that directs the induced electrical current into the workpiece. The coil will be geometrically similar to the workpiece (e.g., a circular coil for heating a round shaft).
Coil design and construction is almost as much an art as a science. Through testing and iteration, coils can be created to heat almost any geometry, which contributes to the great flexibility of induction heating technology. Additionally, there are many different ways to make induction coils, including:
- Additive-manufacturing (i.e., 3D printing) techniques using electron-beam melting (EBM) or laser-beam melting (LBM)
Coils are conductors of electricity for induction heating and, as such, are typically made of copper or other highly conductive material. At the same time, carrying the electricity generates heat, so induction coils are typically hollow to allow for cooling-water flow.
Coil life is a critical component of overall induction heating part production. Depending on the parts and the coil design, part production from one coil life cycle can be in the hundreds of thousands.
Similarly, induction melting also uses induction coils. These coils are typically much larger and surround a refractory-lined vessel where the metal is melted. Higher power and longer times are required to melt metal versus just heating metal.
The two types of induction furnaces are channel and coreless. The channel induction furnace is typically used as a holding furnace and for metals that have lower melting points. The coreless furnace is best utilized for metals with higher melting points. Once materials like cast iron are melted by a coreless induction furnace, a channel induction furnace can then be used to maintain, or hold, the iron in its melted state.
Finally, all induction heating and melting systems require some type of cooling for the power supplies, coils and conductors. This is typically accomplished with process cooling water, heat exchangers, chillers and/or cooling towers. Deionized water is nonconductive and must be used when cooling electrified components such as conductors. Maintenance of cooling water and deionized water systems is critical for the proper operation of an induction heating or melting process.
As you can see, induction heating and melting provide a wide range of process heating technology for manufacturing. Induction heating and melting processes can be found in many industries across many markets. Applications are nearly unlimited because induction systems can be tailored to match power requirements, geometry, overall workpiece size and required final material characteristics.
For more information: Contact IHEA, P.O. Box 679, Independence, KY 41051; tel: 859-356-1575; web: www.ihea.org (see Contact Us). You can learn more about induction at the upcoming IHEA Process Heating Seminar this fall (see sidebar). Please plan to join us.
References available online