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Induction Heating Frequently Asked Questions
These FAQs cover some basics of Induction Heating and are intended for educational purposes. Our field is changing constantly, and some of this information may be out of date. If you have any questions or would like to propose any corrections to this material, please contact us at fluxtrol@fluxtrol.com.
By concentrating magnetic flux, we can increase heating in areas where heat is required and reduce undesirable heating of other areas.
There is no real difference. Concentrators are a type of magnetic flux controller. Controllers can also be shields, shunts or diverters.
Magnetic controllers provide a much easier way for magnetic flux to flow than in air, plastic or other non-magnetic materials. As a result, the magnetic flux may be redistributed or diverted in desired ways, forming areas with much stronger field (effect of concentration) or weaker field (effect of shielding).
Three major types of materials may be used for magnetic flux concentration or control:
- Sheets of special electrical steel (laminations).
- Soft magnetic composites (SMC) with Fluxtrol
- Soft ferrites
When magnetic materials are referred to as “soft”, this refers to the fact that they are soft in the magnetic sense versus the mechanical. Soft magnetic materials retain magnetic field (magnetization) only when they are placed in an external magnetic field. Permanent magnets always keep magnetization and are referred to as “hard”, even if they are mechanically soft, e.g., plastic stickers on refrigerators.
Some users still call Fluxtrol materials “ferrites” or even “magnetic stones” because they look similar to ferrite pieces and perform the same way in a magnetic circuit. However, Fluxtrol materials are SMC’s that have much more favorable properties than ferrites for induction heating applications.
If you place a C-shaped piece of Fluxtrol material on your coil, it will increase the magnetic field intensity (and therefore the heating power) on the part surface under the concentrator opening. If you place a thin plate of Fluxtrol in the gap between the coil and part, it will block heating of the part. In this case we refer to the magnetic piece as a shield, not concentrator.
Fluxtrol increases the level of magnetic flux density under the heat face of the coil, resulting in better coil performance.
Any coil can be a candidate for application of Fluxtrol controllers. However, its effectiveness depends on coil style and sizing, process type and part specifications. Controllers show the strongest effect when applied to ID coils, hairpin, split-n-return coils and relatively short OD coils.
It strongly depends on the coil style and process type (local or complete part heating, scanning or static, etc.). There are multiple cases where parts heat two or even more times faster at the same power settings when and/or where the concentrator is applied. See our videos for illustration.
The minimum thickness depends on the application. Typical thickness of the concentrator pole on the surface hardening coils is 0.125-0.5″ (3-13mm). In some cases, concentrator thickness as small as 0.020″ (0.5mm) have been used in low power, high frequency applications.
The most reliable way is to use computer simulation. It can predict not only improvement in the part heating and the whole system performance, but also expected temperature of the coil, giving you valuable information about the potential coil life time. Contact Fluxtrol’s engineering team for more information.
The strength of Fluxtrol, Inc. is not only in unique materials. We provide strong technical support for existing and potential customers. See CIT’s page on our website for complete information about our technical services.
Yes, Fluxtrol has an experienced technical / sales team that can evaluate the benefits of Fluxtrol in your application. Computer simulation may be proposed for a more accurate analysis of complicated cases.
Yes, we can test your existing coil in our lab and propose modifications if required. For large induction heating coils that require special equipment and high power, we can arrange tests at one of the major OEM facilities in our area.
Unfortunately, no. Pressing chips will not give you any valuable material that could be used for magnetic flux concentrators.
Yes, many companies use laminations and Fluxtrol material on the same coil. Fluxtrol is typically used in the areas of complex geometry, and in zones with 3D magnetic field, such as the end zones of tube seam annealers.
Absolutely. All Fluxtrol materials work well when exposed to hot water, polymer solutions or quenching oil. A unique feature of Fluxtrol compared to other concentrator materials is that it can be used for delivery of quenchants by making channels inside the concentrators.
We use well-established and safe components for manufacturing our magnetic materials. Fluxtrol materials are safe in machining, installation on the coils and in service. MSDS may be sent you upon request.
Poor cooling is the most common cause. Other potential causes are: improper material selection, unfavorable coil design, improper coil assembly, etc. See recommendations for concentrator selection and installation on our website, or contact a Fluxtrol representative for personal support (+1 248 393 2000).
Our materials are definitely non-conductors. Are they electrical insulators? It depends on the material type. All Alphaform and Ferrotron materials are rather good insulators and may be directly applied to uninsulated multi-turn coils in most cases.
Yes. All the Fluxtrol materials may be used outside of the recommended frequency range. If the material is used at too high frequency, we can expect higher magnetic losses than the recommended products. Materials may be used at lower frequencies than recommended, but they often won’t work well due to lower thermal conductivity and magnetic permeability.
Fluxtrol and Ferrotron materials have mechanical properties very favorable for their use as magnetic controllers. They may be easily machined into intricate geometries. Mechanical properties may be provided upon request.
Anisotropic properties are direction dependent properties. All of Fluxtrol’s machinable materials are anisotropic, but some are more anisotropic than others.
Yes, in some critical cases, because the materials are anisotropic, however, usually it’s not a concern. Performance of the concentrators depends mainly upon their magnetic permeability, which influences the concentration effect, and on thermal conductivity, which determines the rate of heat removal from the concentrator to cooling channel in the coil. See our recommendations about optimal use of materials.
The first step is to check the original coil drawings, or to contact your Induction heating coil manufacturer if drawings are not available. Alternatively, please contact a Fluxtrol representative. We will be happy to assist you in determining what material type you have using visual or simple instrumental inspection.
Yes, it works in multiple vacuum applications. There is some outgassing at the beginning of the vacuum setting because of the air flow from the pores. Pores are of the open type and air flows out relatively easily.
There are two sources of heat generation in the concentrator: magnetic losses and heat transfer from the part. This heat will not affect the concentrator performance provided the materials are operating below their rated service temperature. See for more information about thermal management on our website.
Magnetic losses are generated in a magnetic material due to a combination of hysteresis and eddy currents. In the proper frequency range, magnetic losses are approximately proportional to frequency and the square of magnetic flux density.
To model the influence of the concentrator on the part heating, it is enough to know the B-H curve (magnetization curve). If you also want to simulate also the temperature distribution in the coil components (copper tubing, concentrator), you additionally need to know magnetic losses in the Fluxtrol material, its specific heat capacity and thermal conductivity. You can find these data on our website or ask our experts for more information.
All materials produced by Fluxtrol are very machinable. They may be turned, ground, milled, saw-cut and drilled. See more information about machining on our website or contact our experts for advice.
Yes, water jet cutting is an effective method of making 2D parts from Fluxtrol plates. Optimal parameters of cutting can easily be found experimentally.
Carbide tools work best, but high speed steel also work well.
A thin layer of epoxy glue is recommended for most applications. Additional mechanical methods are recommended for higher power applications.
For heavy loaded coils (high power and duty cycle), it is essential to use the correct glue. Thin layer of thermally conductive epoxy is best for heat transfer. Find more tips about glue selection and application on our website.
We don’t recommend reusing concentrators applied to hardening coils with epoxy glue. Heating of the coil in a furnace or by flame torch (which is needed to break down the glue) can damage the concentrators. For quench in place or less demanding applications, you can use only mechanical attachment, or silicone rubber glue. In this case, it is possible to remove and reuse concentrators provided that they do not show signs of overheating.
Brass and non-magnetic stainless steel (e.g. 304) may be used for high strength and temperature application. Non-metallic fasteners such as plastic and fiberglass reinforced polymers (e.g. G10/G11) screws may be used when you want to avoid electrical contact of the concentrator and coil turns.
For long life, the concentrator must be protected from the following factors: mechanical impacts, electrical break and overheating. Please see guidelines for proper installation and protection of Fluxtrol controllers.