“Magnetic King” NdFeB-sunrise industry in rare earth permanent magnet materials
Due to its excellent magnetic properties and high cost performance, neodymium iron boron permanent magnet material has quickly become the leader in the rare earth permanent magnet market since its advent, and its output value accounts for 90% of the world’s output value of rare earth permanent magnet materials, and with the continuous improvement of preparation technology and production technology, its various properties are continuously improved and the application field is gradually expanded. Therefore, the amount of neodymium iron boron permanent magnet material application has become a symbol of the level of modernization, neodymium iron boron permanent magnet material is still a sunrise industry in the rare earth material industry.
Today, let’s meet this new material together.
Permanent magnet materials and their development
Permanent magnetic material is a kind of functional material which is magnetized to saturation under the action of external magnetic field and can still keep its magnetism after the removal of external magnetic field. It is also called permanent magnetic material or hard magnetic material, to put it bluntly, it is the “magnet” that people often say “. “Si Nan”, invented as early as the warring states period, used the function of magnet guide to identify the direction.
Figure.1 SiNan in the warring states period
Although human beings have known magnetic materials for more than 2,000 years, artificial permanent magnets began with magnetized steel needles invented by China in the 10th century. Great progress in the development and application of magnetic materials began in the end of the 19th century and the beginning of the 20th century. At the beginning of the 20th century, people mainly used tungsten steel, carbon steel, chromium steel and cobalt steel as permanent magnet materials. At the end of the 1930 s, (aluminum nickel cobalt) AlNiCo permanent magnet materials were successfully developed, and permanent magnet materials began to be applied in large scale. In the 1950 s, barium ferrite appeared, which reduced the cost of permanent magnets and broadened the application range of permanent magnet materials to the high frequency field. By 1960’s, the successful research and development of rare earth cobalt permanent magnet has entered a new era. In 1967, the SmCo5 permanent magnet successfully made by strnat and others from Dayton University in the United States marked 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 SmCo5 and the second generation precipitation hardening Sm2Co17 to the third generation Nd-Fe-B permanent magnet materials.
In addition, Cu-Ni-Fe, Fe-Co-V, Fe-Co-Mo, A1MnC, MnBi alloys have been used as permanent magnet materials in history. These alloys have been rarely used in most occasions due to their poor performance and low cost performance. The alloys such as fesenco, AlNiCo and PtCo are still used in some special occasions. Ba and Sr ferrite is still the permanent magnet material with the largest consumption at present, but it is gradually replaced by Nd-Fe-B materials in many application fields, and the current output value of rare earth permanent magnet materials has far exceeded that of Ferrite Permanent Magnet Materials, the production of 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 at present, and it is also the most magnetic permanent magnet material so far.
Fig.2 development history of permanent magnet materials (1990-2015)
The characteristics and advantages of NdFeB magnet
Neodymium iron boron is a kind of rare earth permanent magnet compound composed of rare earth metal neodymium, metallic element iron, nonmetal element boron and a small amount of adding elements such as praseostomy, dysprosium, NB, aluminum, gallium, copper, etc, simply speaking, it is a kind of magnet, also known as magnetic steel. The neodymium iron boron permanent magnet is known as the “magnetic king” for its excellent magnetic performance, light weight and low price, wide application range, and is the magnet material with the highest cost performance so far.
The neodymium iron boron permanent magnet has a large magnetic crystal anisotropy field with high magnetic polarization strength, and the theoretical magnetic energy product is 64mgoe. Its magnetic properties are more than 100 times higher than those of magnetic steel used in the 19th century, compared with ordinary ferrite, alnico is 10 times higher than that of the expensive platinum-cobalt alloy in terms of magnetic properties, and its refractory force and energy density are very high, which greatly reduces the sizes of magnetic materials and parts and pushes the instrumentation, electroacoustic motor, the miniaturization, light weight, thinness and high efficiency of the computer, mobile phone and other equipment improve the performance of the product, and promote the production of some special devices; Neodymium iron boron has good mechanical characteristics and is easy to cut and process; its preparation technology is relatively mature. The Curry temperature is about 580K and the use temperature can reach 150℃. NdFeB does not contain strategic elements Co and Ni, and the original materials are rich and its cost performance is very high, this has made its production soar to 55540 tons in since the advent of NdFeB in and to about 130,000 tons in.
Iii. Application of neodymium iron boron rare earth permanent magnet materials
The emergence of neodymium iron boron permanent magnet materials has promoted the progress of human civilization and made great contributions to social and economic development. This kind of materials can realize the mutual conversion function of mechanical energy and electromagnetic energy, and have magneto-optical effect, magnetic resonance effect, magnetic chemical effect, magnetic biological effect, various physical effects of magnetism, such as reluctance effect and Hall effect, have been manufactured as magnetic functional devices and widely used in the fields of computer, transportation, communication, aerospace, industrial automation, medical treatment and so on.
A large number of traditional asynchronous motors are used in the industry. When working, the rotor winding needs to absorb some electric energy from the power grid to excitation, and this part of the power grid energy will eventually be consumed in the rotor winding in the form of current, this part of the loss accounts for about 20% ~ 30% of the total loss of the motor, which reduces the efficiency of the motor. The permanent magnet synchronous motor embeds the permanent magnet on the rotor, and the rotor magnetic field is established by the permanent magnet. When it is working normally, the rotor and the stator magnetic field run synchronously. There is no induced current generation in the rotor, and there is no rotor resistance loss, this alone can improve the motor efficiency by 4% ~ 50%. Because there is no induction current excitation in the permanent magnet motor rotor, the stator winding can realize pure resistance load, making the motor power factor almost 1, greatly improving the quality factor of the power grid, it is no longer necessary to install compensators in the power grid. At the same time, due to the high efficiency of permanent magnet motors, electric energy is also saved.
At present, rare earth permanent magnet motor is the largest application field of neodymium iron boron magnet, accounting for about 70% of the total application amount of magnet, its variety, shape and performance are different. Voice coil motor (VCM) supporting computer hard disk accounts for 40%-50%, so the computer industry is currently the largest user of permanent magnet motor. The neodymium iron boron rare earth permanent magnet material is applied to the development of various motors. It is excited by a permanent magnet without rotor loss and friction. It can be produced with high efficiency, energy saving, light weight, small volume, large torque, low speed drive, stable and low noise motor with long service life maintenance-free can obviously reduce the quality of motor and improve the performance of motor. Combined with the new technology of power electronics, the application of rare earth permanent magnet material in motor can realize mechanical and electrical integration of products, new types of rare earth permanent magnet motors for various purposes have entered a brand-new stage of development.
Automotive industry is one of the fastest growing fields for Nd-Fe-B permanent magnet application. Generally, 40 to 100 NdFeB and SmFeN sintered magnets can be used in dozens of parts of each car, such as engine, brake, sensor, meter, sound box, etc. It is reported that a fully automatic car needs to consume rare earth permanent magnet material 0.5kg ~ 3.5kg; The amount of NdFeB Material on new energy vehicles is more, and each hybrid vehicle (HEV) it consumes about 5kg more NdFeB than traditional cars. Pure electric vehicles (EV) use rare earth permanent magnet motors instead of traditional generators, and more use 5~10kg NdFeB. With the development of automobile industry and the continuous improvement of electronic technology requirements, its demand for nd-fe-B permanent magnet materials will become more and more large.
In 2015, after the rare earth permanent magnet synchronous traction system was successfully adopted in the trial operation of china’s “permanent magnet high-speed railway”, due to the direct excitation drive of the permanent magnet motor, it has high energy conversion efficiency, stable rotating speed, low noise, small volume, the light weight, reliability and many other characteristics have reduced the equipment power of the original 8-compartment train from 6 to 4-compartment equipment power, therefore, the traction system cost of two cars is saved, and the traction efficiency of the train is improved, saving at least 10% of the power is saved, and the life cycle cost of the train is reduced.
After adopting NdFeB rare earth permanent magnet traction motor for subway, the system noise is obviously lower than asynchronous motor when running at low speed. The design structure of permanent magnet generator using brand new enclosed ventilation motor can effectively ensure that the cooling system inside the motor is clean and tidy, and it avoids the problem of screen blocking and cleaning caused by the naked coil of asynchronous traction motor in the past, which makes the use safer and more reliable, less maintenance; The use of direct-drive ND-Fe-B permanent magnet motor makes some rail transit can be expected to remove the gear box in the near future, which will bring revolutionary changes to the traction system of rail transit. Permanent magnet traction has become the mainstream research direction of rail transit trains in the next generation world.
In recent years, maglev aircraft International Co., Ltd. has promoted the U.S. maglev aircraft system in China. The magnetic suspension aircraft system adopts NdFeB permanent magnet, which is a new type of ground rail transportation system. 2 magnetic suspension aircraft trains are needed per kilometer), and each magnetic suspension aircraft train) will use about 10 tons of sintered NdFeB Material. The system realizes the unity of intelligence, large capacity and high speed by optimizing the technical characteristics of various transportation resources and collection diversity, reducing the cost and operating cost. If the maglev aircraft system is put into practical application, the short-range transportation system in the city can be integrated with the inter-city long-distance transportation system, which is helpful to realize the integration of the complicated transportation system in the city.
In addition, rare earth permanent magnet materials are also widely used in magnetic suspension devices such as perpetual magnetic suspension wind generators, permanent magnet bias suspension bearings, magnetic suspension induction motors, etc.
The suspension electromagnet of electromagnetic/permanent magnet composite EMS type structure adopts NdFeB permanent magnet, which does not need simple refrigeration system structure and low cost, and can reduce the power consumption of the whole system. Under the same conditions, its repulsive force of the same pole is 16 times of that of the ferrite, and it can increase the suspension clearance, reduce the precision requirements of the orbit, and enhance the reliability of the suspension and the stability of the train running. On october 22th, 2004, the permanent magnet compensation magnetic suspension technology verification vehicle “zhonghua 01”, which can be taken by 32 people and is independently developed by our country, was unveiled in dalian. The magnet used was rare earth permanent magnet material, which adopted the road integration design structure, the suspension energy consumption is almost zero, and the transportation force is equivalent to the current train, and the safety is greatly improved. At present, china is vigorously promoting the research on the permanent magnetic levitation train using NdFeB magnets, and is expected to build a special line for magnetic levitation trains with a speed of about 600 km/h in the next few years.
Robots, 3D printing and related intelligent manufacturing have attracted more and more attention. Intelligent robots have become a core technology for human to reform the world, and the driving motor is the core component of robots. Inside the drive system, miniature NdFeB magnetic steel is everywhere. For information, at present, the robot motor permanent magnet synchronous servo motor, that is, ND-Fe-B permanent magnet motor is the mainstream, and the servo motor, controller, sensor and reducer are the core components of the robot control system and automation products. The joint movement of the robot is realized by driving the motor, which requires a very large power mass ratio and torque inertia ratio, a high starting torque, a low inertia and a wide range of speed regulation. Especially the end actuator of the robot (hand-claw), the motor with small weight should be used as much as possible; When the rapid response is required, the driving motor must also have relatively large short-time overload capacity; high reliability and stability are the prerequisites for the application of driving motors in industrial robots. In this regard, rare earth permanent magnet motors are most suitable. Some organizations estimate that currently a 165kg welding robot needs to consume about 25kg of high-performance NdFeB. China has also listed robots in the national development strategy plan, and Chinese and foreign-funded enterprises have already deployed the robot industry in action, and have invested huge financial and material resources in the artificial intelligence and robot fields.
In medical treatment, the emergence of NdFeB magnets has promoted the development and miniaturization of magnetic resonance imaging MRI. The permanent magnetic RMI-CT magnetic resonance imaging equipment used to use ferrite permanent magnet, and the magnet weight is up to 50 tons. After using NdFeB permanent magnet material, each nuclear magnetic resonance imaging machine only needs a permanent magnet of 0.5~3 tons, however, the magnetic field intensity is doubled, which greatly improves the image definition. Moreover, the NdFeB permanent magnet equipment has the advantages of least land occupation, smallest magnetic flux leakage and lowest operation cost. As a typical representative of medical robots, rehabilitation robots can help patients carry out scientific and effective rehabilitation treatment. High performance and high integration brushless direct current motor is the key part of the motor driving joint of rehabilitation robots, high temperature resistant NdFeB permanent magnet material.
The application of rare earth permanent magnet in electron beam focusing field is mainly used in various mass spectrometers, accelerators and microwave devices. Typical applications are periodic permanent magnets (REPM), electron beams or other particle beams focusing through magnets to change the direction of forward. At present, the reason why the patriot air-defense missile equipped by the united states can accurately intercept the incoming target is due to the fact that about 4kg samlog cobalt magnet and NdFeB magnet are used in its guidance system for electron beam focusing. The navigation and positioning system of the M1A2 main battle tank uses rare earth magnets, “militia” intercontinental missiles, “trident” missiles, “harpoon” anti-ship missiles, JDAM precision-guided bombs, “hell fire” missiles, “Raptor” F-22 and so on all use rare earth magnets.
The amount of NdFeB used for magneto-electric and electromagnetic instruments accounts for about 6% of the total amount required. Application NdFeB general requirements for permanent magnet magnetic system with simple structure and can ensure high magnetic flux utilization rate and high magnetic flux density in instrument magnetic system. At the same time, the NdFeB magnetic steel body is small and light, and can be made into thin sheets, which provides the possibility of transformation for the miniature and precision of groove watches, wide-angle watches and special shape instruments.
In the air and space, from the shenzhou series spacecraft, the moon exploration project chang’e series satellites to space rockets, they are all inseparable from rare earth permanent magnet materials. Neodymium iron boron permanent magnet plays an irreplaceable role in gyro instrument and navigation system due to its outstanding stability, reliability and highest performance size ratio.
In addition, NdFeB is also widely used in oil field wax removal, electronic communication, numerical control machine tools, household appliances and other fields.
With the upgrading of domestic technological level and the R & D breakthrough 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 of the American and Japanese markets for China’s high-performance sintered NdFeB has increased dramatically. The products of many neodymium iron boron magnet materials manufacturers in China have entered Japan, european countries, the united states and other countries around the world strongly promote the development of high-end NdFeB products in china and the large-scale replacement of ferrite in the market, thus promoting the scale growth of NdFeB in the world.
Source: China Permanent Magnet Manufacturer – www.rizinia.com