Magnetics Business & Technology - May/June 2022 - 27

TECH TIPS
with a homogeneous structure is ultimately created by means of
sintering and a special heat treatment.
According to Velzeboer, the application of the HREE's Dy and
Tb is particularly inefficient: 'These rare and therefore precious
metals are present throughout the entire magnet, while they are
actually only needed on the outside of the magnet to protect the
magnet against heat and counter-field. In addition, the inactive
particles Dy and Tb in the center of the magnet take the place of
neodymium particles that can give the magnet more magnetic
force. "
Grain Boundary Diffusion
This problem has been solved by the new GBD technique. The
HREE's Dy and Tb are no longer in the basic raw material mix,
but are impregnated into the outer layer of the pressed and
sintered permanent magnet using a spray method. Due to a special
heat treatment, the HREEs penetrate even further into the
magnet, spread and form a protective layer around the NdFeB
particles, up to a depth of about 5 mm. Because the vast majority
of HREE particles are in the outer shell of the magnet, much
less heavy rare earth metals are needed than with the traditional
method. Velzeboer: " GBD provides a significant reduction in
the use of Dysprosium and Terbium in permanent neodymium
magnets, often more than 70%. This solution is more sustainable
and cheaper. Because we can process more neodymium in a
magnet, we make the magnet even more powerful, while retaining
resistance. The result of this is that smaller and lighter motors
can be built with the same output. With GBD we can create new
magnet degrees that we would not have dared to dream before.
Grain Refining Technology
The second new technique is Grain Refining Technology (GRT).
This method makes it possible to produce H (max. 120°C) and
SH (max. 150°C) magnet grades in series, completely without
the use of HREE's. " The technology is not as new as GBD, but it
has also resulted in a significant improvement in magnet technology, "
says Velzeboer.
ticles that can all face in the same direction as a line of soldiers.
With the old technique we were on a particle size of an average
of 5.24 μm. With GRT we arrive at 4.34 μm. This is a significant
reduction. This makes the magnet stronger and gives it a higher
resistance to degaussing, compensating for the lack of HREE's.
And if this is also combined with GBD, even new levels are
reached. "
The smaller the particle size, the higher resistance against demagnetization
Better
performances
According to Velzeboer, car manufacturers and suppliers can
push their boundaries considerably with the new magnet technology:
" The new grades significantly improve the performance of
the electric drive and enable a more compact, lightweight construction.
But this is not all. The design of the magnetic rotor and
the precise mounting of the magnets can also optimize the drive,
delivering more power. And this is very important. For example,
a very high angular accuracy of 0.05 ° in the assembly or very
small tolerances of +/- 0.03 mm in the production of the magnets.
Car manufacturers can simply expect this high quality from their
magnetic partner, and we can therefore also meet this. E-mobility
is a fantastic growth market, in which we help more and more
customers from magnet production to prototyping and the eventual
series production and just-in-time delivery of the assembly.
True co-creation, which has become even more exciting than it
already was due to the new magnetic technologies. "
For more info and to access the white paper, see www.bakkermagnetics.com.
FIND
OUT WHY THE WORLD'S LEADING COMPANIES
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Jet Milling process
" You can also achieve a higher magnetic grade by mixing the
metals better. And this can be done by making the particles even
smaller by means of jet milling. The flakes that arise from the
production process are " broken " with the help of hydrogen and
then " shot " into even finer particles with jet-milling. This creates
a very fine homogeneous powder with even more magnetic parwww.MagneticsMag.com
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May/June 2022 * Magnetics Business & Technology 27
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Magnetics Business & Technology - May/June 2022

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