Since the advent of neodymium iron boron magnet material, it has attracted attention for its excellent magnetic properties, and is called the magnet king. With the increase in market demand, the production technology and magnetic properties of NdFeB are also developing and improving. We usually use remanence, coercivity and maximum magnetic energy product to measure the performance of magnetic materials. So, what are the specific factors that affect the performance of NdFeB permanent magnets?
Neodymium permanent magnets, as the name suggests, are magnetic materials made of rare earth metal neodymium, pure iron and boron by powder metallurgy. In order to further improve the magnetic properties of NdFeB, other elements can be added to the ternary Nd-Fe-B material. However, the effect of the addition of elements on the performance of the magnet may be two-way. The additional elements should be determined according to the specific requirements of the use of the neodymium iron boron magnet on the performance of the magnetic material.
In order to obtain high-performance neodymium iron boron permanent magnets, new technologies and new processes are constantly emerging. In the production process of sintered NdFeB, the main problem is to prevent the precipitation of the α-Fe phase and the oxidation of the alloy, and it is difficult to obtain the ideal microstructure. In order to solve these problems, new methods and processes are constantly emerging in practice. For example: adding anti-oxidants and lubricants, and adopting the spinning strip rapid quenching method to prepare magnets; steel ingot homogenization treatment and sheet casting process; two-phase preparation process; wet pressing forming process, etc.
The biggest advantage of adding antioxidants is that the oxygen content of the final magnet is reduced, and the magnetic powder can be ground finer, which is conducive to improving the coercivity. In addition, since the oxygen content is reduced, it is also beneficial to increase the coercivity. Compared with the traditional process, the intrinsic coercivity of the magnet with anti-oxidant can be increased by about 160kA/m.
After lubricant is added, the friction between the magnetic powder is reduced, the fluidity of the magnetic powder is improved, the degree of orientation is improved, and the remanence is improved.
Temperature: NdFeB magnets have strict working temperature limits. When the temperature is higher than the working temperature, the magnet may demagnetize, and when the temperature is higher than the Curie temperature, the demagnetization of the magnet will be irreversible.
Humidity: neodymium permanent magnets are magnetic materials pressed by powder metallurgy technology. The internal structure has voids and is very easy to oxidize. Therefore, neodymium iron boron permanent magnets are coated with anti-corrosion treatment. But the magnetic layer cannot fundamentally deal with the influence of environmental humidity on the magnet. The drier the environment, the longer the magnetic energy of the magnet will last.
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