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"Magnetic King" NdFeB - the sunrise industry in rare earth permanent magnet materials
Time:01/04/2019
Due to its excellent magnetic properties and high cost performance, NdFeB permanent magnet material has rapidly become the dominant player in the rare earth permanent magnet market since its inception, and its output value accounts for 90% of the world's rare earth permanent magnet material production value, and with the preparation The continuous improvement of process and production technology, its performance continues to improve, and the application field is gradually expanding. Therefore, the application of NdFeB permanent magnet materials has become a symbol of the level of modernization. NdFeB permanent magnet materials are still the sunrise industry in the rare earth materials industry.
 
Today, I will meet this new material with Xiaobian.
 
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Permanent magnet materials and their development
 
A permanent magnet material is a functional material that is magnetized to saturation under the action of an external magnetic field and retains its magnetic properties even after the external magnetic field is removed. It is also called a permanent magnet material or a hard magnetic material. Generally speaking, it is often Said "the magnet." The "Sinan" invented in the Warring States Period used the role of the magnet guide to identify the direction.
 
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Figure 1 Sinan during the Warring States Period
 
Although humans have been aware of magnetic materials for more than two thousand years, artificial permanent magnets began with magnetized steel needles invented in China in the tenth century. The development and application of magnetic materials have made significant progress since the end of the 19th century and the beginning of the 20th century. At the beginning of the 20th century, tungsten steel, carbon steel, chrome steel and cobalt steel were mainly used as permanent magnet materials. At the end of the 1930s, AlNiCo (aluminum-nickel-cobalt) permanent magnet materials were successfully developed, and permanent magnet materials began to be applied on a large scale. In the 1950s, barium ferrite appeared, which reduced the cost of permanent magnets and widened the application of permanent magnet materials to the high frequency field. In the 1960s, rare earth cobalt permanent magnets were successfully developed, and the application of permanent magnets entered a new era. In 1967, Strnat of the University of Dayton in the United States successfully made SmCo5 permanent magnets, marking the arrival of the rare earth permanent magnet era. So far, rare earth permanent magnet materials have been developed from the first generation 1:5 type SmCo5, the second generation precipitation hardening type Sm2Co17, to the third generation Nd-Fe-B permanent magnet material.
 
In addition, historically used as permanent magnet materials are Cu-Ni-Fe, Fe-Co-V, Fe-Co-Mo, A1MnC, MnBi alloys, etc. These alloys are poor in performance and low in cost performance. It has rarely been used in most occasions. Alloys such as FeCrCo, AlNiCo, and PtCo are still used in some special applications. Ba and Sr ferrite are still the most widely used permanent magnet materials, but they are gradually being replaced by Nd-Fe-B materials in many applications. The current production value of rare earth permanent magnet materials has far exceeded that of ferrites. The production of magnetic materials and rare earth permanent magnet materials has developed into a major industry. Nd-Fe-B has become the most widely used rare earth permanent magnet material, and it is also the most magnetic permanent magnet material.
 
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Figure 2 History of development of permanent magnet materials (1990-2015)
 
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Characteristics and advantages of NdFeB
 
NdFeB is a rare earth permanent magnet compound composed of rare earth metal lanthanum, metallic elemental iron, non-metallic element boron and a small amount of added elements such as lanthanum, cerium, lanthanum, aluminum, gallium, copper, etc., simply a magnet Also known as magnetic steel. NdFeB permanent magnets have excellent magnetic properties, are light and inexpensive, and have a wide range of applications. They are known as "Magnetic King" and are the most cost-effective magnet materials to date.
 
NdFeB permanent magnets have large magnetocrystalline anisotropy fields, high magnetic polarization, and theoretical magnetic energy product of 64MGOe. Their magnetic properties are more than 100 times higher than the magnetic properties of magnetic steel used in the 19th century. The body, aluminum-nickel-cobalt is 10 times higher than the magnetic properties of the expensive platinum-cobalt alloy. Its coercive force and energy density are high, which greatly reduces the size of magnetic materials and promotes instrumentation and electro-acoustic motors. Miniaturization, light weight, thinning and high efficiency of computers, mobile phones, etc., improve the performance of products, and promote the production of certain special devices; NdFeB has good mechanical properties and is easy to be machined; The preparation technology is relatively mature, the Curie temperature is about 580K, the use temperature can reach 150°C; the NdFeB does not contain the strategic elements Co and Ni, the raw materials are abundant, and its high cost performance makes it come out from 1983. By 2006, the output soared to 55,540 tons, and by 2015, it surged to around 130,000 tons.
 
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Application of NdFeB rare earth permanent magnet material
 
The emergence of NdFeB permanent magnet materials has promoted the progress of human civilization and made tremendous contributions to social and economic development. Such materials can realize the mutual conversion function of mechanical energy and electromagnetic energy, and have various physical effects such as magneto-optical effect, magnetic resonance effect, magnetodynamic effect, magnetochemical effect, magnetic biological effect, magnetoresistance effect and Hall effect. Therefore, magnetic functional devices are widely used in the fields of computers, transportation, communications, aerospace, industrial automation, and medical.
 
A large number of traditional asynchronous motors used in the industry, in operation, the rotor windings must absorb some of the electrical energy from the power grid. This part of the grid power is finally consumed as heat in the rotor windings. This part of the loss accounts for about 20% of the total loss of the motor. 30%, reducing motor efficiency. The permanent magnet synchronous motor embeds a permanent magnet on the rotor, and the permanent magnet establishes the rotor magnetic field. During normal operation, the rotor and the stator magnetic field run synchronously, no induced current is generated in the rotor, and there is no rotor resistance loss, and only one can improve the efficiency of the motor. Increase by 4% to 50%. Since there is no induced current excitation in the rotor of the permanent magnet motor, the stator winding is likely to achieve a pure resistive load, so that the motor power factor is almost 1, which greatly improves the quality factor of the power grid, so that the compensator is no longer needed in the power grid. At the same time, due to the high efficiency of the permanent magnet motor, energy is also saved.
 
At present, rare earth permanent magnet motors are the largest application fields of neodymium iron boron magnets, accounting for about 70% of the total application of magnets. They are various in variety and shape and performance. The voice coil motor (VCM) for computer hard disk accounts for 40%-50%, so the computer industry is currently the largest user of permanent magnet motor. The NdFeB rare earth permanent magnet material is applied to the development of various motors. It is excited by permanent magnets and has no rotor loss and friction. It can be made into high efficiency, energy saving, light weight, small size, high torque, low speed drive and stable low. Noise, long life and maintenance-free motor, significantly reduce the quality of the motor, improve the performance of the motor, combined with the new power electronics technology, so that the application of rare earth permanent magnet materials in the motor can achieve mechanical and electrical integration of products, new rare earth for various purposes Magneto has entered a new stage of development.
 
The automotive industry is one of the fastest growing areas for NdFeB permanent magnet applications. In each car, there are generally dozens of parts such as engines, brakes, sensors, meters, and speakers that use 40 to 100 NdFeB and SmFeN sintered magnets. It is reported that a fully automatic premium sedan consumes about 0.5kg to 3.5kg of rare earth permanent magnet materials; the application of neodymium iron boron materials on new energy vehicles is more, and each hybrid vehicle (HEV) consumes more than conventional vehicles. 5KG NdFeB, pure electric vehicle (EV) uses rare earth permanent magnet motor to replace traditional generator, and uses 5~10KG NdFeB. With the development of the automotive industry and the increasing requirements of electronic technology, the demand for NdFeB permanent magnet materials will become larger and larger.
 
In 2015, China's "permanent magnet high-speed rail" trial operation was successful. After the rare earth permanent magnet synchronous traction system was adopted, the permanent magnet motor was directly excited and driven, which has high energy conversion efficiency, stable speed, low noise, small size, light weight and reliability. And so on, the original train of eight cars, the power of six cars is reduced to four car equipment power, thus saving the cost of the traction system of two cars, improving the traction efficiency of the train, at least 10% power saving The life cycle cost of the train is reduced.
 
After the NdFeB rare earth permanent magnet traction motor is used in the subway, the system noise is significantly lower than that of the asynchronous motor at low speed operation. The permanent magnet generator uses a new closed ventilation motor design structure, which can effectively ensure that the internal cooling system of the motor is clean and clean, eliminating the problem of filter plugging and cleaning caused by the exposed coil of the asynchronous traction motor, which is safer and more reliable, and less maintenance; The use of direct-drive NdFeB permanent magnet motors has made it possible for some rail transits to remove gearboxes in the near future, revolutionizing rail transit traction systems. Permanent magnet traction has become the mainstream research direction of the next generation of world rail transit trains.
 
In recent years, Magplane International Ltd. introduced the US magnetic levitation aircraft system in China. The magnetic levitation aircraft system uses a neodymium iron boron permanent magnet for a new suspension design and is a new type of ground rail transportation system. Two maglev aircraft (trains) are required per kilometer, and each maglev aircraft (train) will use approximately 10 tons of sintered NdFeB materials. The system realizes the unification of intelligence, large capacity and high speed by optimizing various types of traffic resources and collecting diverse technical features, reducing cost and operating costs. If the magnetic levitation aircraft system is put into practical use, the short-distance transportation system in the city and the inter-city long-distance transportation system can be integrated to help realize the integrated solution of the city's complicated transportation system.
 
In addition, rare earth permanent magnet materials are also widely used in magnetic suspension devices such as permanent magnet suspension wind turbines, permanent magnet bias suspension bearings, and magnetic suspension induction motors.
 
The electromagnetic/permanent magnet composite EMS structure of the suspension electromagnet uses NdFeB permanent magnet, does not require a refrigeration system, has a simple structure and low cost, and can reduce the power consumption of the entire system. Under the same conditions, the repulsive force of the same pole is iron. 16 times of oxygen, at the same time can increase the suspension gap, reduce the accuracy requirements of the track, the reliability of suspension and the stability of train operation. On October 22, 2004, the 32-person, China-made permanent magnet compensation magnetic suspension technology verification vehicle "Zhonghua No. 01" was unveiled in Dalian. The magnet used was rare earth permanent magnet material, and the vehicle integrated design structure was adopted. It can be almost zero, the transportation capacity is comparable to that of the current train, and the safety is greatly improved. At present, China is vigorously promoting the study of permanent magnet suspension trains using NdFeB magnets, and it is expected to build a maglev train line with a speed of about 600km/h in the next few years.
 
Robotics, 3D printing and related intelligent manufacturing are receiving more and more attention. Intelligent robots have become a core technology in the human reform world, and the drive motor is the core component of the robot. Inside the drive system, miniature NdFeB magnets are ubiquitous. There is information to check. At present, the permanent magnet synchronous servo motor for robots, that is, NdFeB permanent magnet motor is the mainstream. Servo motors, controllers, sensors and reducers are the core components of robot control systems and automation products. The joint motion of the robot is realized by the drive motor, which requires a very large power-to-mass ratio and torque inertia ratio, high starting torque, low inertia and a smooth and wide speed range. In particular, the robot end effector (hand gripper) should use a small and light motor as much as possible; when it is required to respond quickly, the drive motor must also have a large short-term overload capability; high reliability and stability are the drive. Prerequisites for the application of motors in industrial robots. In this regard, rare earth permanent magnet motors are most suitable. According to some estimates, a 165kg welding robot currently consumes about 25 kilograms of high-performance NdFeB. China has also included robots in the national development strategy plan. Chinese and foreign-funded enterprises have already deployed the robot industry in their actions, and have invested huge financial and material resources in the field of artificial intelligence and robotics.
 
In the medical field, the emergence of NdFeB magnets has promoted the development and miniaturization of magnetic resonance imaging MRI. Permanent magnet RMI-CT nuclear magnetic resonance imaging equipment used to use ferrite permanent magnets. The weight of magnets is up to 50 tons. After using NdFeB permanent magnet materials, each MRI requires only 0.5 to 3 tons of permanent magnets, but the magnetic field The strength is doubled, and the image clarity is greatly improved, and the NdFeB permanent magnet type device has the advantages of the smallest footprint, the smallest magnetic flux leakage, and the lowest operating cost. As a typical representative of medical robots, rehabilitation robots can help patients with scientific and effective rehabilitation. High-performance, high-integration brushless DC motors are key components of the motor-driven joints of rehabilitation robots. High-performance, high-temperature resistant NdFeB is required. Magnetic material.
 
The application of rare earth permanent magnets in the field of electron beam focusing is mainly in various mass spectrometers, accelerators and microwave devices. Typical applications are periodic permanent magnets (REPM), where electron beams or other particle beams are focused by magnets to change the direction of travel, and the like. At present, the United States equipped Patriot air defense missiles can accurately intercept the target, thanks to the use of about 4 kg of samarium-cobalt magnets and neodymium-iron-boron magnets in the guidance system for electron beam focusing. The navigation and positioning system of the M1A2 main battle tank uses rare earth magnets, "Military" intercontinental missiles, "Trident" missiles, "Harpoon" anti-ship missiles, JDAM precision guided bombs, "Hellfire" missiles, "Raptor" F-22, etc. Both use rare earth magnets.
 
The amount of NdFeB used in magnetoelectric and electromagnetic meters accounts for about 6% of the total application. The application of the NdFeB permanent magnet magnetic system is simple in structure and ensures the general requirements of high magnetic flux utilization and high magnetic flux density in the magnetic system of the instrument. At the same time, the NdFeB magnet body is small and light, and can be made into a thin sheet shape, which provides the possibility of modification for the miniaturization and precision of the trough type meter, the wide angle meter and the special shape meter.
 
In aerospace, from the series of Shenzhou series spacecraft, lunar exploration engineering series satellites to space rockets, rare earth permanent magnet materials are inseparable. NdFeB permanent magnets play an irreplaceable role in gyroscopes and navigation systems due to their outstanding stability, reliability and highest performance.
 
In addition, NdFeB is also widely used in oilfield wax removal, electronic communication, CNC machine tools, home appliances and other fields.
 
With the upgrading of domestic technology and the breakthrough of research and development of proprietary equipment, the performance of various rare earth permanent magnet materials developed and produced in China has approached or reached the international advanced level. With the gradual recovery of the world economy, the demand for high-performance sintered NdFeB in China in the Americas and Japan has increased dramatically. The products of many NdFeB magnet materials manufacturers in China have entered Japan, Europe and the United States, and are strongly promoted. China's research and development of high-end NdFeB products and large-scale substitution of ferrites in the market have promoted the global growth of NdFeB.