What are pressed magnets ?

Pressed magnets are the result of the bonding between thermoplastic binders and permanent magnet powders, i.e. ferrite, neodymium and/or samarium cobalt, and can be divided into isotropic magnets and anisotropic full density magnets.

The manufacturing process of this type of magnet is significantly different from the traditional sintering and gluing. Hot pressed magnets have fine glass grains after a series of unique manufacturing processes.

The magnetic properties of hot pressed magnets are much higher than those present in traditionally bonded magnets, even because it makes the neodymium sintered.

This type of magnets have an excellent resistance to heat, managing to withstand up to about 180deg C during operation. Hot pressing and deformation technology requires no orientation mechanism during the molding process. The flexibility and declination of its poles depends entirely on the magnetization process.

What are the advantages of pressed magnets?

They have excellent mechanical properties that allow tight tolerances to be reached, facilitating their equilibrium and assembly. The waveforms of pressed magnets are determined by the magnetization process and their nanocrystalline structure and higher density is able to ensure that they have greater corrosion resistance.

Also, pressed magnets have certain disadvantages in relation to other types of magnets, because:

• The investment in equipment is greater than other magnets.

• The manufacturing process is more complex.

• Production efficiency remains very low.

• Freedom of form is limited.

Despite the magnetic properties of this type of magnet, which are close to the properties of sintered neodymium magnets, its value is even higher than that of this type of magnet. In fact, nowadays, the price of pressed magnets is an important element at the time of their manufacture.

What are the applications of hot pressed magnets?

Hot pressed magnets can help the smooth running engine, but they are punctually used in:

• Electric power steering (EPS) of the motor.

• AC / DC servo motor.

• Power tools.

Pressed magnets have demonstrated the heat resistance described above in the hybrid cars of a major Japanese assembler, demonstrating that high coercitivity magnetic properties have been the best option for reducing the use of heavy rare earth elements.

Prepared samples of pressed magnets, to date, exhibit intrinsic coercivities of approximately 1200 kA / m, a remanence of around 690 mT and maximum BH values of approximately 90 kJ / m 3 . Careful studies of microstructures reveal that the magnets consist of Nd 2 Fe 14 B predominantly in the range of 0.1 μm⩽ x ⩽1.0 μm with a very small number of grains in the range of 10 μm ⩽ x ⩽35 μm.

These larger grains exhibit very regular morphology and are the result of very rapid growth of some of the smaller micrometric grains. B 8 ensures that the magnets have 12% neodymium-rich intergranular material and this low melting point phase has been found to aid the densification process.

This neodymium-rich material is very unevenly distributed throughout the hot pressed magnet and little evidence of its presence can be found among the grains of Nd 2 Fe 14 B.

This material enables the creation of more complex geometries. IMA currently manufactures this product for numerous customers such as motor manufacturers, magnetic encoders for household appliances, washers and motors, automotive, among others, so if you are interested in knowing more about the power of pressed magnets, do not hesitate to contact us.