Since its inception, NdFeB permanent magnet materials have attracted much attention for their superior magnetic properties and are known as "Magnetic King". With the continuous growth of market demand, NdFeB production technology and magnet performance have also continued to develop and improve. promote. We generally use remanence, coercivity and magnetic energy product to measure the performance of magnetic materials.
Remanence Br: If a magnet is likened to a sponge, the remanence is as if the sponge is saturated with water, and the magnetic force value of the magnet displayed at this time. It refers to the magnetic induction intensity of a magnet that is magnetized by an external magnetic field in a closed-circuit environment to the technical saturation and then cancels the external magnetic field.
Coercive force Hcb and intrinsic coercive force Hcj: The water in the sponge is absorbed to a large extent, and then the water is pressed out until there is no water in the sponge. The pressure used is like the coercive force. It is the value of the reverse magnetic field strength required for the magnetic induction to drop to zero when the magnet is reversely magnetized. However, the magnetization of the magnet is not zero at this time, but the applied reverse magnetic field and the magnetization of the magnet cancel each other out. If the external magnetic field is canceled at this time, the magnet still has certain magnetic properties. Intrinsic coercivity is the reverse magnetic field strength required to reduce the magnetization of the magnet to zero.
Magnetic energy product (BH)max: The sponge is saturated with water, and the total amount of water in it can be understood as a large magnetic energy product. It represents the magnetic energy density established by the space between the two magnetic poles of the magnet, that is, the magnetostatic energy per unit volume of the air gap, which is the larger value of the product of Br and Hcj, and its size directly indicates the performance of the magnet.
Today, I will talk to you about what determines the above performance of NdFeB strong magnetism, how to improve the performance of magnetic materials through technical means, and how to avoid the loss of performance of magnetic materials in use.
The raw material composition and production process of NdFeB permanent magnet 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 so, demagnetization will occur.
1. The effect of raw material composition on the strong magnetic properties of NdFeB
As the name suggests, NdFeB strong magnetism is a magnetic material made of rare earth metal Nd, pure iron and boron by powder metallurgy process. Other elements are further added, but the effect of the addition of elements on the performance of the magnet may be bidirectional, and the added elements should be determined according to the specific requirements of the magnetic material performance in the application of NdFeB strong magnetism.
. Effect of production process on the strong magnetic properties of NdFeB
In order to obtain high-performance NdFeB permanent magnets, new technologies and processes are constantly 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 an ideal microstructure. In order to solve these problems, new methods and processes are emerging in practice, such as: Antioxidants and lubricants are added, and magnets are prepared by rapid quenching and stripping method; steel ingot homogenization treatment and sheet casting process; dual-phase preparation process; wet pressing molding process, etc.
The great advantage of adding antioxidant is that the oxygen content of the magnet is reduced, and the magnetic powder can be ground more finely, which is beneficial to improve the coercivity. Compared with the traditional process, the intrinsic coercivity of the magnet with antioxidant added can be increased by about 160kA/m.
After adding the lubricant, the friction force between the magnetic powders is reduced, the fluidity of the magnetic powders is improved, the degree of orientation is increased, and the remanence is improved.
The thickness of NdFeB strips prepared by stripping method is 0.25-0.35mm, which can eliminate the α-Fe phase. Due to the enhanced oxidation resistance of the powder prepared by the strip method, the grain size of the magnet becomes smaller, and the coercive force is greatly improved.
The above are the factors and methods that affect the performance of NdFeB permanent magnets. Do you all know? If you have magnet-related needs, please contact Cihan Electronic Technology.