Neodymium permanent magnetic material

Neodymium permanent magnetic material
NdFeB permanent magnetic material is called "Magnet King". It was discovered in 1983. In 1985, it was industrialized in Japan, China, Europe and the United States at the same time. It has been 35 years. In the past 35 years, the global NdFeB permanent magnetic material industry has developed vigorously. Its magnetic properties have continuously set new records, the variety and grade of materials have continuously improved, the industrial technology innovation has changed with each passing day, and the material output has increased rapidly.
NdFeB permanent magnet is a tetragonal crystal formed by neodymium, iron and boron. According to the different production processes, it can be divided into sintered NdFeB, bonded NdFeB and hot-pressed NdFeB. Due to different production processes, they have great differences in product magnetism, post-treatment and application.
Sintered neodymium magnet
Sintered NdFeB is the largest and most widely used product in the NdFeB family. It is produced by powder metallurgy and is divided into N, M, H, SH, UH, EH and TH according to the different coercivity of products. Series. Commercially produced sintered NdFeB has a remanence of up to 1.45T and an intrinsic coercivity of up to 2786kA/m. The operating temperature is between 80 ° and 200 °, depending on the coercivity. Sintered NdFeB is easy to be oxidized and corroded, so surface treatment is required. According to the different requirements of the use environment, surface treatment methods such as phosphating, electroplating, electroless plating, electrophoresis and vapor deposition can be used. Common coatings such as zinc, nickel, nickel, copper nickel, epoxy resin, etc.
Bonded neodymium magnet
Sintered NdFeB is difficult to be accurately processed into special shapes, and it is easy to crack, fracture and difficult to assemble in the process. In order to solve these problems, people try to crush permanent magnets, mix them with adhesives, and then press them in the magnetic field., Bonded neodymium, iron and boron have just come out. With the advantages of low cost, high dimensional accuracy, large degree of freedom of shape, good mechanical strength and light weight, it has been widely used in the market.
At present, there are four processes to combine NdFeB: calendering, injection molding, extrusion and compression molding, of which calendering and injection are the mainstream. Bonded Nd-Fe-B magnets are generally only 80% of the theoretical density due to the addition of a large number of adhesives, so their magnetic properties are weaker than sintered Nd-Fe-B magnets. Bonded NdFeB is an isotropic magnet with the same magnetism in all directions, so it is very convenient to make multipolar or even countless monolithic magnets. (Bonded NdFeB can also be made into anisotropic magnets)
Hot-pressed neodymium magnet
Hot-pressed NdFeB can achieve magnetism similar to sintered NdFeB without adding heavy rare earth elements. It has the advantages of high density, high orientation, good corrosion resistance and high coercivity, but its mechanical properties are poor., In addition, due to patent monopoly and high processing costs, only a few companies in the market have achieved batch production of hot-pressed NdFeB products.
Due to the limitations of molding technology, the current hot-pressed NdFeB can only be made into rings, and the application range is limited. At present, it is mainly used in the field of automobile EPS motor. The hot-pressed NdFeB magnet has high magnetic properties, and the maximum radial energy product of the magnetic ring can reach 240~360kJ/m3. The magnetic ring is radial and the radial magnetic performance is uniform, which can make the motor run quietly and the torque output stable. At the same time, it has high heat resistance, and the service temperature can reach 180 ° C-200 ° C.