1、稀土永磁体的应用简况（Application of rare earth permanent magnet）Application of rare earth permanent magnetRen Lie Zhu JinghanWith a long history appear permanent magnetic materials and applications. During the Warring States period (from 475 BC to 221 BC), people used natural magnetite in ores to polish the s
2、hapes needed to guide them. In the past 100 years, with the rapid development of science and technology, permanent magnet materials are constantly improving. The emergence of new permanent magnetic materials has promoted the improvement and development of permanent magnet devices. The demand of high
3、 and new technology has promoted the emergence of new permanent magnetic materials“. Therefore, the development and application of new permanent magnetic materials are very important in the high-tech industry. Rare earth permanent magnets, especially NdFeB, have a great influence on the development
4、of modern high and new technology industry.The influence of 1. permanent magnet material on permanent magnet devicePermanent magnetic material (body) is in a specified space can produce constant magnetic materials. Permanent magnets can be used either alone or in combination with other ferromagnetic
5、 or non ferromagnetic materials to form magnetic circuits, and then become magnetic devices. The performance of permanent magnet materials can be reduced, which makes it possible for various permanent magnetic devices in modern industry to be small, micro and lightweight. The maximum magnetic energy
6、 product (BH) max of one of the important properties of permanent magnetic materials describes the progress of permanent magnetic materials and their influence on magnetic devices.There new materials always have new properties, such as rare earth permanent magnet materials with high coercive force o
7、ther than the permanent magnet material, this feature to develop a new class of applications and devices.Classification of applications of 2. permanent magnetic materialsThere are many classification methods application of permanent magnetic materials, the most basic is classified from physical prin
8、ciple, there are several:2.1 electrical mechanical conversion(1) motor: DC motor, stepper motor, hysteresis motor, linear motor, servo motor and so on;(2) generator(3) transmission device: magneto optical recording, laser focusing, printing head, VCM in computer disk drive, etc(4) measuring instrume
9、nts(5) current control: reed switch, eddy current motor, over speed switch, etc2.2 electric sound conversion(1) sound producing device: loudspeaker, earphone, telephone, etc(2) receiving sound device: receiver, ultrasonic broadcaster, etc(3) other audio converters.2.3 a magnetic force or torque(1) f
10、ixed or lifting device: all kinds of magnetic chuck (magnetic suspension), door suction block, refrigerator seal strip, etc(2) processing device: magnetic separation, copier magnetic roller, etc(3) magnetic coupling and braking device, etc(4) magnetic bearings, magnetic levitation trains and so on.(
11、5) electronic scale2.4 microwave devices, electron beams and ion beam focusing(1) power tube: magnetron, periodic permanent magnet (PPM).(2) waveguide devices(3) particle accelerators: synchrotron radiation sources, free electron lasers, etc(4) mass spectrometer: deflection magnet, alpha mass spectr
12、ometer and so on.(5) cathode ray tube: ion trap, focusing, etc2.5 sensor, electrical signal transmission, change(1) the use of magnetism: Hall effect, magnetoresistance, temperature sensitive components, etc(2) volume effect: position, velocity, acceleration, liquid flow, pressure, vibration, etc(3)
13、 area effect: computer read write head.2.6 medical and biological(1) medical equipment: magnetic resonance imaging (MRI).(2) dental appliances: tooth fixation, orthopedic and so on.(3) surgical instruments.(4) magnetic therapy and magnetic jewelry2.7 other applications(1) magnetic pin(2) vacuum tech
14、nology(3) magnetic bit storage bias field, etcRare earth permanent magnet for permanent magnetic materials in the latest and highest magnetic materials, the principle can be applied to all of the above areas. The largest use of NdFeB in the western world is the voice coil motor (VCM) in the computer
15、 disk drive, accounting for 57% of the total. The biggest use of China is audio (27%) and motor (25%), the western world of these two items accounted for 5% and 17% respectively. The VCM magnets in China account for only 1%.This is because most of the NdFeB magnet production in China is low performa
16、nce products, suitable for audio and motor applications, the so-called horn piece of magnetic steel common market is the application. The magnetic steel used by VCM requires high performance: (BH) max 318.4kJ / m3 (40MG0e), high machining accuracy, good product consistency and fast update. This prod
17、uct is also one of the positions held by the rare earth permanent magnet manufacturers in the United States and japan. Magnetic resonance imaging (MRI) is another big field of NdFeB application. China has just started, and the western world is 11%. Only the units such as Shenzhen and Zhangjiagang ha
18、ve researched and manufactured in our country, but they havent formed industry yet. Oil field paraffin removal device in China accounted for 22%, is the third major application areas, the west is zero. This is related to the special oil composition of Chinas oil fields, including high wax content. I
19、n short, in the application of rare earth permanent magnet, especially NdFeB permanent magnet, our country has its own characteristics.Typical examples of 3. rare earth permanent magnet applications3.1 audio devicesOther applications include speakers, headset stereo.The magnetic circuit structure in
20、ner magnet speaker (with Alnico magnet) and the outer magnetic type (using ferrite magnets do) two. When using rare earth permanent magnet, it can be applied to two kinds of structures: internal magnetic type and external magnetic type, and the size and weight are greatly reduced. At present, some d
21、omestic and foreign manufacturers of advanced audio equipment have been introduced NdFeB speakers, electroacoustic performance has been greatly improved. Chinas large export of horn magnet steel is mainly used in high performance stereo headphones.Paraffin remover in 3.2 OilfieldContains more China
22、petroleum wax, pull out the oil from the formation process, due to the oil pressure, temperature and other environmental changes, the crude oil containing wax precipitation in the well wall and the pipeline, so each year due to wax production and caused huge economic losses. A magnetic circuit is fo
23、rmed in the tube with rare earth permanent magnet. The crude oil passes through the magnetic field and prevents wax precipitation effectively. This greatly reduces the number of oil well cleaning and shutdown, and improves the output. At present, this is one of the most important rare earth applicat
24、ions. In addition to paraffin, there are also rare permanent magnets made of oil well, such as salvage device.3.3 motorBoth at home and abroad, rare earth motor has become one of the largest field of rare earth permanent magnet application. It has a wide range of shapes and properties. China has a h
25、igh level of development and development of rare earth motor. Individual varieties of motor, such as light motorcycle rare earth starting motor has reached the scale of production. Due to the appearance of rare earth permanent magnet, the size of permanent magnet motor is greatly reduced. Automotive
26、 industry is the biggest potential application field of rare earth permanent magnet motor.3.4 computer VCM magnetMobile computer hard disk and floppy disk drive read head is composed of VCM voice coil motor driven. With the continuous progress of computer technology and hardware, the shape and perfo
27、rmance requirements of VCM magnet are changing frequently. The market requires VCM magnets (BH) m 318.4kJ / m3 (40MGOe) levels.3.5 magnetic resonance imaging system (MRI)Magnetic resonance imaging is the use of the body within the nuclei of hydrogen atoms in magnetic measurement on the parameters of
28、 magnetic resonance signals of permanent magnetic field and scanning field, the tissue and body symptoms caused by the change, as image shading and display, in order to achieve the purpose of diagnosis. The magnetic field sources include (a) superconducting electromagnets, (b) general electromagnets
29、, (c) permanent magnets, and (three). Permanent magnet type equipment has the advantages of minimum leakage flux, minimum occupied area and lowest operation cost, while the imaging quality is better than the superconducting one, which is better than the electromagnetic one. Especially, the emergence
30、 of NdFeB magnets has promoted the development of MRI and made it possible to make the permanent magnet MRI more compact. When using ferrite, the device weighs 100 tons, only 10 tons when using NdFeB. At present, the world has installed NdFeB MRI has reached 1000 or so.China has started the research
31、 work of rare earth permanent magnet type MRI and great progress.3.6 electron beam focusing and microwave devicesElectron beam focusing in the field of application of rare earth permanent magnet is mainly in a variety of accelerator,Mass spectrometer and microwave device. Because of the high ambient
32、 temperature, the Sm Co rare earth permanent magnet is usually used. Typical applications are periodic permanent magnets (REPM), electron beams or other particle beams focused by magnets, changing the direction of forward motion, etc3.7 magnetic chuck and magnetic suspensionDomestic about this work
33、at the international advanced level, the independent development of the room temperature and high temperature permanent magnet lifting head (permanent magnetic crane), especially high temperature in Jilin province Tonghua Steel Corp hanging casting plant, lifting hot billet has been working for seve
34、ral years, reflecting the good. And there are 10 national patents. The existing problem is how to extend the new product to practical application.3.8 magnetic separationMagnetic separation mainly refers to form a magnetic circuit using rare earth permanent magnet, metal or non-metallic minerals and
35、various raw materials for separation. The appearance of rare earth permanent magnet makes the separation ability and efficiency of magnetic separation equipment increase, and the volume decreases. A lot of work has been carried out in our country and the products have been sold. It has been successf
36、ully used in the separation of iron ore, mica, quartz and other minerals, and the effect is very good.3.9 meterInstrument is a wide application field of permanent magnet, including various magnetic, electromagnetic instrument. Such as ammeter, voltmeter, watt hour meter, speed and acceleration meter
37、 and other conventional measuring instruments. Because of the appearance of rare earth permanent magnets, especially the NdFeB magnets, the instrument has achieved high precision and miniaturization.3.10 other applicationsChina rare earth permanent magnet application research and promotion of the ea
38、rlier work and made great achievements, but also has Chinese characteristics in some aspects, such as the use of magnetic pump, solves the problem of leaking oil industry. The development and application of magnetic medical treatment of various diseases and magnetic jewelry, also belongs to the rare
39、 earth permanent magnet which has a wide range of influence.Application of another rare earth permanent magnet maglev system is important. The magnetic suspension bearing has been successfully applied to the ultra high speed rotating device and the kilowatt hour meter bearing. In addition, it should
40、 be pointed out that there is a huge potential application area, namely, maglev transportation system. Its research began in 70s, not in the early 80s. The experimental line of Maglev transit system using rare earth permanent magnet has been run in Berlin, Germany and Las Vegas in the United states.
41、 Recently, according to the science and technology daily, Germany has started an investment project involving 18 billion Mark and established a maglev high-speed train, which has been put into practice. If maglev train is put into commercial operation, it will greatly promote the development of rare
42、 earth permanent magnet industry. This project is only carried out in several developed countries with strong economic strength and high technical level.Appears rare earth permanent magnet is a tremendous progress in the field of permanent magnet materials, especially the high performance NdFeB rare
43、 earth permanent magnet materials made of high-tech industrial magnetic device high efficiency, miniaturization, light become possible. The magnetic devices were used in many fields that could not be used in the past. Therefore, some new applications of permanent magnetic field were opened up. The r
44、esearch of new rare earth permanent magnet materials is more and more deep and extensive, and new materials will be developed continuously in the near future. It is believed that with the application of rare earth permanent magnet, the application of rare earth permanent magnet will usher in a new era of high and new technology.References (abbreviated)
