This neodymium magnet is audited by the project of compiling and applying the scientific encyclopedia entries

This neodymium magnet is audited by the project of compiling and applying the scientific encyclopedia entries of "Popular Science China"

Brief introduction：Neodymium magnet, also known as neodymium magnet, is a tetragonal crystal composed of neodymium, iron and boron (Nd2Fe14B). In 1982, Sumitomo Sagawa, a special metal, discovered the neodymium magnet. The magnetic energy product (BHmax) of this kind of magnet is larger than that of Sm-Co magnet, which is the largest substance in the world at that time. Later, Sumitomo Special Metals successfully developed the powder metallurgy process, and General Motors successfully developed the melt-spinning process to prepare neodymium magnet. This kind of magnet is a permanent magnet whose magnetism is second only to the absolute zero holmium magnet, and it is also the most commonly used rare earth magnet. Neodymium magnet is widely used in electronic products, such as hard disks, mobile phones, headphones and battery-powered tools. In order to avoid corrosion damage, it is necessary to protect the surface of permanent magnet materials, such as electroplating with gold, nickel, zinc and tin, and spraying epoxy resin on the surface.

Classify: NdFeB can be divided into sintered NdFeB and bonded NdFeB. Bonded NdFeB is magnetic and corrosion resistant in all directions. However, sintered NdFeB is easy to corrode and needs to be coated on its surface. Generally, there are zinc plating, nickel plating, environmental protection zinc plating, environmental protection nickel plating, nickel copper nickel plating and environmental protection nickel copper nickel plating. Sintered NdFeB is generally magnetized in axial direction and radial direction, depending on the required working face.

NdFeB surface treatment: With the unfreezing of patented technology of sintered NdFeB in Japan, Germany and the European Union, and the concerted efforts of major sintering manufacturers in China, the grade of sintered NdFeB products has been greatly improved. As a high-tech application field, its comprehensive performance has been continuously improved, and the requirements for surface treatment of sintered NdFeB have also been greatly improved. The traditional treatment methods can no longer meet the requirements of industrial chain progress. Scientific research institutions such as Electronic Science and Technology University, Sichuan University, Jiaotong University, and Ruishileisi have started with the micro-molecular structure. In essence, the principle of surface treatment and the development of industrial application technology have been improved. After four years' efforts, breakthroughs have been made in key technologies. The nano (3010) chelating film is uncoated, which is an original technology. The active groups contained in the nano-film layer have strong resistance to moisture, oxygen, chloride ion (Cl), carbon dioxide (co2), etc. The corrosion resistance and the adhesive ability of organic resin have been greatly improved. Its excellent surface physical and chemical properties are very good for. In December 2013, the treatment process was systematically tested by Sichuan University and Chinese Academy of Sciences. Its corrosion resistance can meet the requirements of 20-30 years in marine climate conditions, and it can be widely used in sea-based wind power generation. The surface adhesion is more than 20Mpa, and it can be widely used in permanent magnet high-speed motors, special motors, electric vehicle motors, UHV, high-voltage DC power supply systems, fast charging systems, aerospace military industries and other fields. Common surface treatment methods: 1. Nanometer (Royce3010) chelating film is treated without plating; (3010 means that the film contains more than three active chelating groups, and the film thickness is 10 nm); 2, phosphating; 3, electroplating; 4, electrophoresis; 5, vacuum vapor deposition; 6. Electroless plating; 7, organic plastic spraying;

Application: Sintered NdFeB permanent magnet(HTMAGNETS) materials have excellent magnetic properties, which are widely used in electronics, electric machinery, medical instruments, toys, packaging, hardware machinery, aerospace and other fields, such as permanent magnet motors, speakers, magnetic separators, computer disk drives, magnetic resonance imaging equipment and meters. The coating-free treatment of nano (Royce3010) chelating film can be used in marine climate for 20-30 years, and can be widely used in sea-based wind power generation. The surface adhesion is above 20Mpa, and it can be widely used in permanent magnet high-speed motors, special motors, electric vehicle motors, UHV, high-voltage DC power supply systems, fast charging systems, aerospace military industries and other fields.

Chemical composition: NdFeB permanent magnetic material is a permanent magnetic material based on intermetallic compound Nd2Fe14B. The main components are rare earth elements neodymium (iron (Fe), boron (B). Among them, the rare earth element is mainly neodymium (Nd), which can be partially replaced by other rare earth metals such as dysprosium (Dy) and praseodymium (Pr) in order to obtain different properties, and iron can also be partially replaced by other metals such as cobalt (Co) and aluminum (Al). The content of boron is small, but it plays an important role in forming intermetallic compounds with tetragonal crystal structure, which makes the compounds have high saturation magnetization and high monomer content. The third generation of rare earth permanent magnet NdFeB is the most powerful permanent magnet among contemporary magnets. Its main raw materials are rare earth neodymium 29%-32.5%, metallic element iron 63.95-68.65%, nonmetallic element boron 1.1-1.2%, dysprosium 0.6-8%, niobium 0.3-0.5%, aluminum 0.3-0.5% and copper 0.05-. distinguish 1. Usually, it is placed on an adsorbable plane with a magnet of the same specification, such as a patch, a blade, an iron gate, etc., and the magnitude of the magnetic force is distinguished by the feel. 2. Use an electronic scale: a magnet with weak magnetic force is generally related to its density. If the density is small, the magnetic force is relatively small. If it is heavy, the magnetic force is relatively large. On the contrary, if it is light, the magnetic force is small.

Product introduction: Each type of product is divided into several brands according to the maximum magnetic energy product. The brands of NdFeB magnetic materials are: N35-N52, 35M-50M, 30H-48H, 30SH-45SH, 28UH-35UH, 28EH-35EH. Example of brand number: 048021 stands for sintered NdFeB permanent magnet material with (BH)max of 366~398kj/m3 and Hcj of 800kA/m. The brand of sintered NDFEB permanent magnet material consists of three parts: principal name and two magnetic characteristics. The first part is principal name, which consists of chemical symbol Nd of neodymium, chemical symbol Fe of iron and chemical symbol B of boron. The second part is the number before the line, which is the nominal value of the maximum magnetic energy product (BH)max of the material (in kj/m3), and the third part is the number after diagonal lines, and the value of magnetic polarization strength coercivity (in Ka/m3). Example of brand number: NdFeb380/800 represents sintered NdFeB permanent magnet material with (BH)max of 366 ~ 398 kJ/m3 and HCJ of 800 Ka/mr.