Magnetic field orientation and magnetization of sintered NdFeB
In the first two issues, we introduced the grades and working temperature of sintered NdFeB. After understanding these basic knowledge, let’s talk about magnetization. Where does the magnetism of sintered NdFeB magnet come from? How to magnetize it? How to choose the direction of magnetization?
The magnetism of sintered NdFeB material is mainly derived from its easily magnetized crystal structure. It can obtain extremely high magnetism under the action of a strong external magnetic field, and its magnetism will not disappear after the external magnetic field disappears, so “magnetization” It is a key step for sintering NdFeB materials to obtain magnetism. In the production and preparation process of sintered NdFeB material, magnetization is the last step before the delivery of the finished product, but the magnetic field orientation of the NdFeB blank is already determined when the magnetic powder is pressed into a blank, and the direction of the upcoming magnetization.
Magnetic field orientation of sintered NdFeB
Magnetic materials are divided into isotropic magnets and anisotropic magnets. Isotropic magnets have the same magnetic properties in any direction and can be attracted together at will; anisotropic magnets have different magnetic properties in different directions, and the direction that can obtain the best magnetic properties is called the orientation direction of the magnet. For a square sintered NdFeB magnet, only the orientation direction has the highest magnetic field strength, and the other two directions are much smaller.
If the magnetic material has an orientation process in the production process, it is an anisotropic magnet. Sintered NdFeB is generally molded and pressed by magnetic field orientation, then it is anisotropic, so the orientation direction needs to be determined before production, the upcoming magnetization direction . Powder magnetic field orientation is one of the key technologies for manufacturing high-performance NdFeB. (The bonded of NdFeB has isotropic and anisotropic)
Magnetizing direction and method of sintered NdFeB
Magnetization is the process of applying a magnetic field to the sintered neodymium iron boron permanent magnet along the orientation direction of the magnetic field, gradually increasing the strength of the magnetic field to reach the technological saturation state.
Sintered NdFeB generally has several forms such as square, cylinder, ring, tile, etc. Next, we will talk about their respective magnetizing directions.
In addition to the above-mentioned ordinary single-pole magnetization, sintered NdFeB can also be multi-pole magnetized according to actual needs, that is, multiple N and S poles can be present on a plane after magnetization. Due to the use of specially designed specifications and pole head magnetizing fixtures, additional magnetizing fixture costs will be incurred.
(Multi-stage magnetization, the picture comes from the Internet)
The magnetizer is a tool for magnetizing magnetic materials or magnetic device magnets, through which a magnetic field is applied to the neodymium iron boron products that need to be magnetized. If the magnetized magnetic field cannot reach the technical saturation magnetic field, the remanence Br and the intrinsic coercive force Hcj of the permanent magnet cannot reach the expected value.
(Magnetic machine, the picture comes from the Internet)
So how to determine the energy of the magnetizer? First, determine the size of the magnetization tooling according to the size and magnetization direction of the magnetized product, and then calculate the size of the central magnetic field of the tooling. The size of the tooling magnetic field should be 3-5 times the coercivity of the magnet, and then calculate the magnetizing current Determine the energy storage capacitor capacity of the magnetizer according to the current and the voltage of the magnetizer, and finally determine the energy of the magnetizer.
The basic principle of magnetization is to place the magnetic object to be magnetized in the magnetic field formed by the coil through which DC current passes. There are two main methods: DC magnetization and pulse magnetization. The technical details will be discussed later.
Source: China Permanent Magnet Manufacturer – www.rizinia.com