Rare-earth permanent magnet and its application

First, Rare-earth permanent magnet material 

Rare-earth permanent magnetic material is a kind of magnetic material, which is made of SM, nd mixed rare earth metal and transition metal (such as cobalt, iron, etc.). It is made by powder metallurgy and magnetized by magnetic field. 

The permanent magnets of samarium cobalt (SmCo) permanent magnets and NdFeB (NdFeB) are permanent magnets, in which the magnetic energy of the SmCo magnets is between 15 and 30MGOe, and the magnetic energy of the NdFeB system permanent magnets is between 27 and 50MGOe. It is called the "king of permanent magnets" and is the most magnetic permanent magnet at present. Samarium cobalt permanent magnets, despite their excellent magnetic properties, contain rare rare earth metal samarium and rare and expensive strategic metal cobalt. Therefore, its development has been greatly restricted. The development of China‘s rare earth permanent magnet industry began at the end of 60s. The dominant product was samarium cobalt permanent magnet at that time. At present, the world sales volume of SM co permanent magnet was 630 tons, and our country was 90.5 tons (including SmCo magnetic powder), mainly used in military technology. 

With the development of computer and communication industry, rare earth permanent magnet, especially the NdFeB permanent magnet industry, has been developing rapidly. 

The rare-earth permanent magnet is one of the most comprehensive permanent magnetic materials known now. It is more than 100 times higher than the magnetic properties of the magnetic steel used in nineteenth Century, and is much better than the ferrite, aluminum and nickel and cobalt, and is twice as high as the magnetic energy of the expensive platinum cobalt alloy. The use of rare earth permanent magnets not only promotes the miniaturization of permanent magnet devices, improves the performance of the products, but also promotes the production of some special devices. So the rare earth permanent magnetic materials appear, which immediately causes great attention and rapid development in various countries. The performance of various rare earth permanent magnet materials developed in China has reached or reached the international advanced level. 

Now rare earth permanent magnetic material has become an important material in electronic technology communication. It is used in the traveling wave tube, circulator, micro motor, micro recording machine, aeronautical instrument, electronic watch, seismometer and some other electronic instruments. At present, the application of rare earth permanent magnet has penetrated into automobile, household electric appliance, electronic instrument, magnetic resonance imaging instrument, sound equipment, micro electric motor, mobile phone and so on. In terms of medical treatment, the use of rare earth permanent magnetic materials for "magnetic hole therapy" has greatly improved the curative effect and promoted the rapid popularization of "magnetic hole therapy". Rare-earth permanent magnet materials are among the fastest growing areas in the field of rare earth applications. It not only brings great impetus to the development of rare earth industry, but also has a far-reaching impact on many related industries. 

The Second. Classification of rare earth permanent magnet materials 

1. rare earth cobalt permanent magnet materials, including rare earth cobalt (1-5) permanent magnet material SmCo5 and rare earth cobalt (2-17 type) permanent magnet material Sm2Co17 two category. 

2. rare earth neodymium permanent magnet material, NdFeB permanent magnet material. 

3. rare earth iron nitrogen (RE-Fe-N) or rare earth iron carbon (RE-Fe-C) permanent magnet materials. 

Three, classification of preparation technology of rare earth permanent magnet materials 

1. Sintered magnets prepared by powder metallurgy sintering process; 

2. sintered magnet prepared by reduction diffusion powder or hydrogen crushing powder and powder metallurgy sintering process. 

3. bonded magnets made by rapid solidification or pulverization (HDDR) and powder molding. 

4. injecting magnet prepared by injection process of rapidly solidified powder or HDDR powder; 

5. hot pressing magnet prepared by hot pressing of rapidly solidified powder or HDDR powder. 

6. anisotropic hot deformation magnets made by hot pressing magnet and hot deformation process. 

7. the hot deformation magnets were ground into powder and then the anisotropic bonded magnets were prepared by means of molding or injection. 

Four, the main application of rare earth permanent magnet materials 

The most basic function of permanent magnet is to produce a constant magnetic field in a specific space, and no external power is needed to maintain the magnetic field. There are many parameters to mark permanent magnetic materials, and the most important is the maximum magnetic energy product (BH) max. The larger the magnetic energy product, the greater the energy of the external magnetic field per unit volume of the material. At present, the maximum magnetic energy product of NdFeB permanent magnet material has reached 50MGOe. Because of the excellent properties of high magnetic energy product and high coercivity, the rare earth permanent magnetic materials have brought revolutionary changes to the permanent magnet applications, and the rare earth permanent magnet materials are mainly used in the following aspects: 

1. mechanical and electrical classes 

The appearance of rare earth permanent magnets means that the motor field will cause revolutionary changes. This is because the rare earth permanent magnet has no excitation loss and no heat, and the motor made of it has many advantages. Because the rare-earth permanent magnet motor has no magnetizing coil and core, the volume of the magnet is smaller than the original magnetic field, without loss and heat, so the weight of the same output power can be reduced by more than 30%, or the same volume, weight, and the output power of 50%. 

The permanent magnet motor, especially the micro motor, produces around 100 million units a year. It is mainly used in automobiles, office automation equipment and household appliances. High performance ferrite and rare earth permanent magnets are used. 

One of the biggest markets for rare earth permanent magnet motors will be the automotive industry in the future. Nd-Fe-B permanent magnet materials are excellent in performance, and can be used to manufacture motors. In automobile, only small motor can reduce the weight of the car, increase the sense of comfort, improve the safety, reduce the exhaust emission and improve the overall performance of the car. At present, the biggest use of the motor is the starting motor. The motor is an indispensable part of the automobile, and the number of motors on the motor is increasing year by year. There are 8~18 cars on average and up to 40~50 cars. With the development of the automobile industry, the demand for automotive motors is huge.