The raw material composition and production process of NdFeB magnets determine its innate magnetic properties. After becoming a strong magnetic product, its working environment (including temperature, humidity and other factors) will affect its innate magnetic properties, improper use. If there is, there will be permanent demagnetization.
1. Effect of raw material composition on the strong magnetic properties of NdFeB
NdFeB magnets, as the name suggests, are magnetic materials made from rare earth metal lanthanum, pure iron and boron by powder metallurgy. In order to further improve the magnetic properties of NdFeB, it can be based on ternary Nd-Fe-B materials. Further addition of other elements, but the effect of the addition of elements on the performance of the magnet may be two-way, the addition of elements should be determined according to the specific requirements of the magnetic properties of the use of NdFeB magnetism.
2. Influence of production process on the strong magnetic properties of NdFeB
In order to obtain high-performance NdFeB permanent magnets, new technologies and processes are emerging. In the production process of sintered NdFeB, the main problem is to prevent the precipitation of 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 emerging in practice, such as: Adding anti-oxidant and lubricant, and preparing the magnet by the quick quenching method; the ingot homogenization treatment and the sheet casting process; the two-phase preparation process; the wet compression molding process.
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 beneficial to increase the coercive force, and also contributes to the improvement of the coercive force due to the decrease of the oxygen content. Compared with the conventional process, the intrinsic coercive force of the magnet with added antioxidant can be increased by about 160 kA/m.
After the addition of the lubricant, the friction between the magnetic powders is reduced, the fluidity of the magnetic powder is improved, the degree of orientation is improved, and the remanence is improved.
The thickness of the NdFeB strip prepared by the tape method is 0.25-0.35 mm, which can completely eliminate the α-Fe phase. Since the powder obtained by the entrainment method has enhanced oxidation resistance, the grain size of the magnet becomes smaller and the coercive force is greatly improved.
3. The influence of working environment on the strong magnetic properties of NdFeB
Temperature: NdFeB magnet has a strict operating temperature limit. When the temperature is higher than the working temperature, the magnet may demagnetize. When the temperature is higher than the Curie temperature, the magnet demagnetization will be irreversible.
Humidity: Sintered NdFeB is a magnetic material that is pressed and formed by powder metallurgy. Its internal structure is void and it is very easy to oxidize. Therefore, sintered NdFeB will be treated with anti-corrosion treatment. However, the coating does not fundamentally address the effects of ambient humidity on the magnet. The drier the environment, the longer the magnetic properties of the magnet