NTN develops high performance magnetic core for induction hardening equipment

August 26, 2014

NTN Corporation, headquartered in Osaka, Japan, has announced the development of a high performance magnetic core with what it claims is the industry’s highest level of magnetic properties and strength. The process involves coating the surface of iron powder with thermosetting resin and applying compression moulding.


The high performance magnetic core is capable of

processing numerous shapes

Machine parts such as bearings and gears are heat treated to increase strength and to improve reliability. In particular, parts related to drive equipment commonly found in automobiles which have a complex shape require strength in certain areas, calling for heat treatment or high-frequency induction heating (induction hardening) to harden the required areas. The heating coil section of induction hardening equipment features magnetic material attached called a “core” that contributes to reducing heat treatment time and improving hardening precision. Until now this has, however, suffered from issues related to low material strength, excessive processing man-hours and material loss.

The newly developed high performance magnetic core from NTN uses iron powder as the magnetic powder, with a proprietary mix of thermosetting resin added for granulation processing to apply an insulating coating over the surface of the iron. A special type of compression moulding and thermal hardening help to limit damage to the coating.

These features reduce contact between powders, and the saturated magnetic flux density, the market index for magnetic properties, is improved by 10%. The relative permeability is increased by 30%, and the iron loss is reduced by 15% to achieve what NTN claim are the industry’s highest level of magnetic properties. The radial crushing strength is also five times that of commercially available products, which drastically improves core cutting work and handling. Utilisation of the developed product brings improvements to induction hardening efficiency for more accurate hardening, which helps to reduce the time required for heat treatment, and increase both strength and hardness of machined parts.

Induction heat treatment is gaining attention as a form of heat treatment that does not require fossil fuels or detergents. The new magnetic core is already in use with equipment at NTN, however the product is now being marketed to new manufacturers of induction hardening equipment and high-frequency heat treatment machining companies.


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