CD Laboratory for powder metallurgical soft magnets

This CD Laboratory is researching ways to produce magnets for high-frequency applications, which are needed in electromobility, among other things. New types of metal alloys are being developed for this purpose and their properties researched.

Powder metallurgy is a method in which metal powders are pressed into shape under high pressure and these so-called "green compacts" are then compacted into the finished moulded part by sintering or mechanical processing, e.g. by rolling. With this process, metals can also be moulded below their often very high melting point. The workpieces are characterised by very high dimensional accuracy and surface quality. Although many metals and alloys can be used, the largest product group in terms of quantity is based on iron and steel.

The most important area of application is the automotive industry. However, powder metallurgy is undergoing major changes due to developments such as the shift away from combustion engines towards electric motors and the move towards additive manufacturing (also known as 3D printing). However, material development is not yet sufficiently mature for many of these new products.

The CD Laboratory for Powder Metallurgical Soft Magnets is dedicated to special soft magnetic iron-based materials. These so-called SMCs (soft magnetic compounds) are characterised by the fact that they extend the concept of laminated steel sheets to the third dimension by substituting the laminated sheets with insulated iron powder particles.

In electrical engineering and electronics, the term "laminated sheets" refers to the arrangement of thin soft iron sheets that are used to produce the magnetic circuit of a series of coils in transformers. Laminating with electrically insulating paint reduces eddy current losses and prevents the magnet from heating up. All metallic soft magnets currently still have too high eddy current losses at high frequencies. Therefore, new material concepts must be developed to massively reduce these losses in order to replace the ferrites currently used, as these have a low saturation due to their low magnetic flux density and are therefore limited in their applications.

The improvement in magnetic efficiency is to be achieved through special manufacturing concepts, thus extending the application range of SMCs to significantly higher frequencies than the approx. 1000 Hertz currently achievable. This requires special alloy concepts and the achievement of an insulating coating at powder particle level that remains stable even with moderate temperature treatment. As these alloys are not available on the market in powder form, they are to be produced on a laboratory scale by ultrasonic atomisation of a melt produced by melting a rod of the corresponding composition. If these materials themselves are not available as rod or wire, a production route must be developed for these primary materials. This is also possible through powder metallurgical production. Ideally, new alloys will therefore be available for the production of powder metallurgical magnets.