稀土永磁及其应用Rare earth permanent magnet and its application
近年来稀土永磁材料在国内的应用发展很快，目前已应用于一般电机、大电机如磁力泵、磁选设备、永磁吊车和家用电器等方面。但与西方国家相比，我国生产的钕铁硼磁体，包括出口，用得最多的是音响器件（中国是全球最大的扬声器生产者，国产钕铁硼有近一半用于制造扬声器），其次是电机和油井除蜡器。而在音圈马达等国外用量最多的领域，我国的应用还很少。其原因在于这两个应用领域所用的磁体，不仅要求磁性能高，均匀性、一致性好，而且要求加工精度高，镀层质量好，国内大多数厂家的产品难于满足上述使用要求。1、 Rare earth permanent magnet material
Rare earth permanent magnet material is a kind of magnetic material made of the alloy composed of samarium and neodymium mixed rare earth metals and transition metals (such as cobalt, iron, etc.), which is pressed and sintered by powder metallurgy and magnetized by magnetic field.
Rare earth permanent magnets are divided into samarium cobalt (SmCo) permanent magnets and neodymium iron boron (NdFeB) permanent magnets. The magnetic energy product of SmCo magnets is between 15 and 30mgoe, and the magnetic energy product of NdFeB permanent magnets is between 27 and 50mgoe. It is known as the "king of permanent magnets". It is the most magnetic permanent magnet material at present. Although samarium cobalt permanent magnet has excellent magnetic properties, it contains rare earth metal samarium and rare and expensive strategic metal cobalt. Therefore, its development is greatly limited. The development of China's rare earth permanent magnet industry began in the late 1960s. At that time, the leading product was samarium cobalt permanent magnet. At present, the world sales volume of samarium cobalt permanent magnet is 630 tons and that of China is 90.5 tons (including SmCo magnetic powder), which is mainly used in military technology.
With the development of computer, communication and other industries, rare earth permanent magnet, especially NdFeB permanent magnet industry, has developed rapidly.
Rare earth permanent magnet material is a kind of permanent magnet material with the highest comprehensive performance. It has more than 100 times higher magnetic properties than the magnetic steel used in the 19th century, much better properties than ferrite and Al Ni Co, and twice higher magnetic properties than the expensive platinum cobalt alloy. The use of rare earth permanent magnet materials not only promotes the miniaturization of permanent magnet devices, improves the performance of products, but also promotes the emergence of some special devices. Therefore, the emergence of rare earth permanent magnet materials immediately attracted great attention and developed very rapidly. The properties of various rare earth permanent magnet materials developed and produced in China have approached or reached the international advanced level
Now rare earth permanent magnet materials have become important materials in electronic technology and communication. They are used in traveling wave tubes and circulators in satellite and radar, as well as micro motors, micro recorders, aviation instruments, electronic watches, seismometers and other electronic instruments. At present, the application of rare earth permanent magnet has penetrated into automobile, household appliances, electronic instruments, nuclear magnetic resonance imaging instrument, audio equipment, micro special motor, mobile phone and so on. In medical treatment, the use of rare earth permanent magnet materials for "magnetic acupoint therapy" has greatly improved the curative effect, thus promoting the rapid promotion of "magnetic acupoint therapy". Rare earth permanent magnet materials are one of the fastest developing fields in the application of rare earth. It not only brings great impetus to the development of rare earth industry, but also has a far-reaching impact on many related industries.
2、 Classification of rare earth permanent magnet materials
1. Rare earth cobalt permanent magnet materials, including rare earth cobalt (type 1-5) permanent magnet material SmCo5 and rare earth cobalt (type 2-17) permanent magnet material Sm2Co17.
2. Rare earth neodymium permanent magnet material, NdFeB permanent magnet material.
3. Rare earth iron nitrogen (re-fe-n system) or rare earth iron carbon (re-fe-c system) permanent magnet materials.
3、 Preparation process classification of rare earth permanent magnet materials
1. Sintered magnet prepared by powder metallurgy sintering process;
2. Sintered magnets prepared by reduction diffusion powder making or hydrogen crushing powder and powder metallurgy sintering process;
3. Bonding magnet prepared by rapid solidification powder making or hydrogen crushing powder making (HDDR) and powder molding bonding process;
4. Injection magnet prepared by injection process of rapid solidification powder preparation or hydrogen fragmentation (HDDR) powder;
5. Hot pressed magnet prepared by hot pressing method of rapid solidification powder preparation or hydrogen fragmentation (HDDR) powder;
6. The anisotropic hot deformation piezoelectric magnet prepared by hot deformation pressing process with hot pressing magnet;
7. The hot deformed piezoelectric magnet is ground into powder, and then the anisotropic bonded magnet is prepared by molding or injection.
4、 Main applications of rare earth permanent magnet materials
The most basic function of permanent magnet is to generate a constant magnetic field in a specific space. Maintaining this magnetic field does not need any external power supply. There are many parameters to mark the quality of permanent magnet materials. 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 generated by the material per unit volume. At present, the maximum magnetic energy product of commercial NdFeB permanent magnet materials has reached 50mgoe. Due to the excellent characteristics of rare earth permanent magnet materials such as high magnetic energy product and high coercivity, it has brought revolutionary changes to the application of permanent magnet. Rare earth permanent magnet materials are mainly used in the following aspects:
The emergence of rare earth permanent magnets means that the field of motor will cause revolutionary changes. This is because the rare earth permanent magnet has no excitation loss and no heating. The motor made of it has many advantages. Because the rare earth permanent magnet motor has no excitation coil and iron core, the magnet volume occupies less space than the original magnetic field pole, has no loss and no heating. Therefore, in order to obtain the volume of the whole machine with the same output power, the weight can be reduced by more than 30%, or the output power can be increased by more than 50% with the same volume and weight.
Permanent magnet motors, especially micro motors, produce hundreds of millions of units in the world every year, mainly used in automobiles, office automation equipment and household appliances. Most of the used are high-performance ferrite and rare earth permanent magnets.
In the future, one of the largest markets for rare earth permanent magnet motors will be the automotive industry. Nd-Fe-B permanent magnet material has excellent performance. It can be used to manufacture motor and realize "Nd-Fe-B" of automobile motor. In terms of automobile, only small motor can reduce the weight of automobile, increase comfort, improve safety, reduce exhaust emission and improve the overall performance of automobile. At present, the largest consumption is starting motor. Motor is an indispensable part of automobile, and the number of motors on automobile is increasing year by year. There are 8 ~ 18 cars in general and 40 ~ 50 high-end cars. With the development of automobile industry, the demand for automobile motors is huge. The rare earth permanent magnet with high magnetic energy product has small volume, but can produce much greater power than ferrite, so the electrical efficiency is improved. By using rare earth magnets to reduce weight and size, more fuel can be saved and design flexibility can be increased.
2. Application of rare earth permanent magnet materials in medical treatment
3. Magnetic separator
There are two types of general magnetic separators: permanent magnet type and electromagnetic type. In the past, the magnets of permanent magnet magnetic separators mostly used ferrite. After the emergence of rare earth permanent magnet, various models and types of permanent magnet Separators have been designed and manufactured, especially in medium and high magnetic field separators, rare earth permanent magnet must be used.
4. Computer and peripheral equipment
The most rare earth permanent magnet used in computers is disk drive motor (VCM), and the other is data output printer motor.
5. Various instruments
There are many kinds of instruments using permanent magnets, such as magnetoelectric instruments, counters, etc.
6. Speakers and headphones
Speakers and earphones are traditional applications of permanent magnets. There are two types of loudspeakers: external magnetic and internal magnetic. After the emergence of rare earth permanent magnet, the loudspeakers are made very small under the same output power and sound quality. At present, rare earth permanent magnet loudspeakers and headphones have been applied to advanced walkman.
7. Microwave devices
In the microwave field, microwave tubes, milliwave tube generators or Amplifiers need to stabilize the magnetic field. Rare earth permanent magnets mainly play the role of aggregation of electron motion.
5、 Present situation and future development trend of rare earth permanent magnet materials
In recent years, the application of rare earth permanent magnet materials in China has developed rapidly. At present, they have been used in general motors and large motors, such as magnetic pumps, magnetic separation equipment, permanent magnet cranes and household appliances. However, compared with western countries, the most widely used NdFeB magnets produced in China, including exports, are audio devices (China is the world's largest speaker producer, and nearly half of domestic NdFeB magnets are used to manufacture speakers), followed by motors and oil well wax removers. However, there are few applications in China in voice coil motor and other fields with the largest consumption abroad. The reason is that the magnets used in these two application fields require not only high magnetic properties, good uniformity and consistency, but also high machining precision and good coating quality. The products of most domestic manufacturers are difficult to meet the above requirements.