The impact of break corner on the performance of magnets
Since the second industrial
revolution and people entered the electrification era, a large number of
electrical and electronic equipment have entered our lives and changed our
lives. And most electrical equipment can't do without one material, that is
magnet. Rare earth permanent magnets are increasingly used in various fields
due to their excellent magnetic properties. Among them, NdFeB magnets are the
most in demand. The sintered NdFeB industry is the top
priority of the magnetic material industry. New application growth points are
constantly emerging, especially the development of knowledge economy
represented by the information industry, constantly bringing new uses to
functional materials such as rare earth permanent magnets.
Everyone knows that sintered
neodymium iron boron is prepared by powder metallurgy process, and then through
mechanical processing to achieve the shape and size we need, and finally
surface treatment. The process flow is long, and there are many processes that
require turnover. In addition, the powder metallurgy process material is
relatively brittle, and the magnet will inevitably produce some bumps during
the handling and turnover process, resulting in some small chips and break
corners. So will these break corners have an impact on the application, and how
great is the impact?
For magnets, magnetic properties
are the key functional properties of magnets. Break corners affect the size and
volume of the magnet, while changes in the volume of the magnet affect the
overall magnetic properties of the magnet. When the PC value is greater than
0.5 , The magnetic flux of the magnet ≈ the product of
remanence*volume. Here, an ordinary magnet is used to simulate and calculate
the influence of break corners on the magnetic performance. Take the magnet of
NdFeB N35 as an example, the size is 20*20*20 mm, and the tolerance is all
+/-0.1. We can calculate that the volume range of the upper and lower tolerance
limits is 7880.6-8120.6 mm³, and the corresponding magnetic flux range is
108.458-116.956 mWb through simulation. Assuming that there are 2 break corners
on the magnet, the size of each break corner is 2*2*1 mm, and the total break
corner is submitted as 8 mm³, which accounts for 0.1% of the total volume. The
simulation calculation results in a magnetic flux of 0.102 mWb corresponding to
a volume of 8 mm³. From these data, we can find that the magnetic flux deviation
of the tolerance range of the magnet itself is 8.498 mWb, and the magnetic
performance loss caused by break corners accounts for 1.2% of the magnetic
performance of the tolerance deviation and 0.09% of the overall magnetic
performance. Therefore, the impact of the break corners on the performance is
very weak, and the change in the magnetic performance is smaller than the
normal tolerance range.
Most of the magnets are assembled
with some metal parts, or injected into plastic parts. break corner have no
effect on the appearance of the assembled and injection molded products. Some
break corners have almost no effect on the performance of the magnet. Products
with some small break corner can be used. In addition to break corner, there
are other appearances issue, such as poor plating, cracks, pores, etc., because
these poor conditions will affect the corrosion resistance and structural
strength of the magnet, so this type of appearance will be directly judged as
unqualified products.
Of course, for some specially application
magnets, the appearance is its main function, and the appearance requirements
are particularly high. When the quantity is particularly large, we will use the
CCD full inspection method to make the selection, which can more efficiently
meet the needs of customers.
