NdFeB and other materials


In junior high school, physics must be learned, that is, electricity generates magnetism, and magnetism generates electricity.

Electromagnetism consists in passing current through a straight metal wire, then a circular magnetic field will be generated in the space around the wire. The greater the current flowing through the wire, the stronger the magnetic field generated. The magnetic field has the shape of a circle surrounding the wire.

NdFeB and other materials

The Danish physicist Hans Oersted continued to experiment: he placed a live wire and a magnetic needle in parallel, and the magnetic needle deflected, thus discovering that "electricity" could generate "magnetism".

August 29, 1831, Faraday wound two coils around a round iron rod, one of which was connected to a power source, and a small magnetic needle was placed in parallel under the other coil. When the power is turned on, the magnetic needle wobbles slightly, when the power is turned off, the magnetic needle wobbles in the opposite direction.

This experiment shows that when the power is turned on or off, the current changes and the magnetic field also changes. From this, Faraday concluded that a changing magnetic field induces an electric current. Faraday developed experiments with different scenarios and different materials and confirmed that as long as the magnetic flux passing through a closed circuit is changing, there will be current in the closed circuit. This is the famous "law of electromagnetic induction".

Magnetic material is a very important functional material in life, which can be divided into ordinary permanent magnet material and rare earth permanent magnet material. It has a wide range of applications, whether in the fields of national defense, energy, information communications, automotive or electrical engineering.

Permanent magnetic material is also called permanent magnetic material or hard magnetic material, which means that after magnetization, the external magnetic field can be removed.

This is a functional material that retains magnetism for a long time and withstands the influence of an external magnetic field of a certain strength. Permanent magnet

Materials can perform important functions such as electrical signal conversion and electrical/mechanical energy transmission and are widely used

In the field of energy, transport, mechanical engineering, medical care, computers and household appliances.

** It should be noted that the magnetic materials used in conventional electrical appliances are soft magnetic. Soft magnets and permanent magnets differ significantly in materials, material properties and application scenarios

Rare earth materials for permanent magnets are a kind of rare earth elements RE (Sm, Nd, Pr, etc.) and a transition group

Permanent magnetic material based on intermetallic compounds formed by TM metal elements (Fe, Co, etc.),

It is commonly referred to as a rare earth intermetallic compound permanent magnet or simply a rare earth metal permanent magnet. 1960s

Since then, along with three major advances in magnetic energy, three generations of practical materials have been successfully developed

Sharp-earth permanent magnets with applied value. The first generation is represented by SmCo5 alloy, and the second generation is represented

Sm2Co17 alloy is representative, and the third generation is represented by Nd-Fe-B alloy. Among them is neodymium

Boron-ferromagnets have been introduced into the industry and have the best integrated characteristics in the current industrial production

Permanent magnetic material.

A brief history of the development of magnetic materials

1. Cobalt steel: In 1930, this was the earliest human-made magnetic material. Although its magnetism is much stronger than natural magnets, it is still a low performance material for permanent magnets.

2. Alnico Permanent Magnet Casting: Later, people used Al, Ni, Co and Fe to make stronger materials for permanent magnets, in proportion Br can reach 12000-13000 Gauss, (BH)m can reach 5-10MGOe, Hc 500-600 Oe.

3. Permanent Magnetic Ferrite: In the 1950s, iron oxide powder was used to successfully develop cermet materials for permanent magneticc. Typically, Br is 3000-4000 Gs, (BH)m is 3.0-5.0 MGOe, and Hc is 1500-3000. e. Because it is iron oxide powder, the cost is low and the price is cheap.

4. Rare earth cobalt permanent magnet (first generation): Rare earth cobalt permanent magnet was successfully developed around 1970s, Br can reach 0.9-11.0kgf, (BH)m is 18-20MGOe, Hcj can reach more than 30K . . It is a rare earth permanent magnet of the first generation. Mainly SmCo5, SmPrCo5 and other brands.

5. Rare earth cobalt permanent magnet (second generation): by the end of the 1970s, the rare earth cobalt permanent magnet type Sm2 (Co, Cu, Fe, Zr) 17 was successfully developed, and (BH)m can reach 30MGOe. It is called rare earth permanent magnet second generation.

6. NdFeB permanent magnet (third generation): By the end of the 1980s, the strongest magnet in the world has been successfully developed, NdFeB (Nd-Fe-B) permanent magnet material, Br 12000~15000Gs, (BH)m can reach 40~50MGOe, Hc12.0~30K Oe, is called third generation rare earth permanent magnet.

NdFeB is a compound of rare earth permanent magnets, composed of the rare earth metal neodymium, the metal element iron, the non-metal element boron, and a small amount of added elements such as praseodymium, dysprosium, niobium, aluminum, gallium, copper and other elements. , Magnet, also known as magnetic steel. NdFeB permanent magnets have excellent magnetic properties, low weight and low price, have a wide range of applications and are the most cost-effective magnetic materials today.

But due to its strong reactivity, its surface needs to be coated (eg zinc, nickel, electrophoresis, passivation, etc.).

Its temperature performance is poor, magnetic loss is large when used at high temperature, and the maximum operating temperature is low. Generally, it is about 80℃, and the maximum working temperature can only reach 200℃ after the special processing of the magnet.

Due to different production methods and application requirements, NdFeB permanent magnets can be divided into three categories:

(1) Bound NdFeB (Bound NdFeB): Bound NdFeB magnets are obtained by cooling microcrystalline powder, each powder contains several microcrystalline Nd-Fe-B grains, and then polymerized compound or other binders are used to mix and bind the powder. and then pressed, extruded or calendered to form a plastic permanent magnet. Therefore, a conventional NdFeB bonded magnet is a loose isotropic magnet.

The magnetic properties of ordinary NdFeB bonded magnets are much lower than those of sintered NdFeB magnets, but NdFeB bonded magnets have many irreplaceable advantages of sintered NdFeB magnets: high processing accuracy, high output, high precision and excellent magnetic properties, good corrosion resistance and good temperature stability; In addition, Nd-Fe-B magnets are also easily magnetized in any direction and can easily create multi-pole or even infinite integral magnets.

(2) Sintered NdFeB (Sintered NdFeB): Sintered NdFeB permanent magnet is produced by powder metallurgy, the main process is alloying (melting) → coarse crushing → fine crushing → grinding to 3~5.0 µm Fine powder → magnetic pressing with field orientation→vacuum sintering and quenching→inspection→processing→finished product.

Sintered NdFeB permanent magnet has high coercivity and good mechanical properties. It can be cut and processed into various shapes and drilled holes, but it is easily corroded, so various coatings must be applied to the surface. according to different requirements. And very hard and brittle, with high resistance to demagnetization, not suitable for high operating temperatures.

(3) NdFeB Injection Molding (Zhusu NdFeB): It has extremely high precision and can easily produce thin-walled rings or thin magnets with complex anisotropic shapes.

NdFeB magnets can be widely used in motors, motors, voice coil motors, magnetic resonance imaging instruments, communications equipment, instrumentation, audio equipment, etc.

At present, rare earth permanent magnet motors are the largest application area of ​​NdFeB magnets, accounting for about 70% of the total magnet applications. There are many types, with different shapes and characteristics.

Voice coil motors for computer hard drives account for 40% to 50%, which is why the computer industry is currently the largest consumer of permanent magnet motors.

The automotive industry is one of the fastest growing applications for NdFeB permanent magnets. Each car usually has dozens of parts, such as engines, brakes, sensors, instruments, speakers, etc., which use 40 to 100 sinteredNdFeB and SmFeN magnets.

A fully automatic luxury car should consume 0.5 to 3.5 kg of permanent magnet rare earth materials; more NdFeB materials are used in new energy vehicles, and each hybrid vehicle consumes about 5kg more neodymium than traditional vehicles. Iron, boron, pure Electric vehicles use rare earth permanent magnet motors instead of traditional generators, and use 5-10 kg more neodymium-iron-boron. With the development of the automotive industry and the continuous improvement of electronic technology requirements, the demand for NdFeB permanent magnet materials will increase.

Wind energy, vehicles powered by new energy sources, robotics - these three areas are very promising industries in the next 3-5-10 years.

At present, sintered NdFeB is still the rare earth permanent magnet material with the highest performance and widest application range in China. In 2019, the output of sintered NdFeB blanks in China was 170,000 tons, which is more than in the past year. 9.7%, accounting for the largest share of domestic rare earth permanent magnets. The output of materials was 94.3%, the output of bound NdFeB was 0.79 tons, an increase of 5% year on year in 2018, accounting for 4.4% .

September 24, 2021 The U.S. Department of Commerce announced on the 24th that the department has launched a "232 investigation" into whether imports of neodymium iron boron permanent magnets (neodymium iron boron permanent magnets) have harmed U.S. national security . This is the first "232 investigation" launched by the Biden administration since taking office. The US Department of Commerce said NdFeB permanent magnet materials are used in key national security systems such as fighter jets and missile guidance systems, in key infrastructure such as electric vehicles and wind turbines, as well as in computer hard drives, audio equipment and magnetic resonance. equipment.

This shows the importance of NdFeB.

The main components of NdFeB are praseodymium-neodymium (29-32.5%), iron (63.95-68.95%), boron (1.1-1.2%), etc., and the cost raw materials is about 80%. ;

Among them, rare earth elements (praseodymium, neodymium, dysprosium and terbium) account for more than 90% of the cost of raw materials, and the increase in the price of rare earth elements will have a direct impact on the cost of raw materials. NdFeB enterprises.

Overall history of NdFeB price fluctuations in history:

1) In the 2010-2011 ascending cycle, the price of rare earth elements rose about a quarter faster than the price of NdFeB, and the price of NdFeB rose from 107,500 yuan to 628,000 yuan per ton, an increase of almost 5 times. and the profit per ton of NdFeB enterprises was the highest. The point is close to 200,000 yuan/ton;

2) During the rare earth up cycle from June 2017 to September 2017, NdFeB price growth also lagged behind rare earth prices by about 3 months. by about 30% due to the short-term upward cycle of rare earth metals, the stability of the increase in prices for magnetic materials is also low;

3) Rare earth price cycle from October 2020 to present is similar to the previous cycle. The price of NdFeB increased from 113,500 yuan/t to 240,000 yuan/t, an increase of 111%. magnetic materials, NdFeB enterprises. Profit per ton also gradually increased.

According to this story, does the 110,000-240,000 swing seem to be down and up?

Looking back to 2021year, for example, the price of Baotou in July:

The average basic price of praseodymium and neodymium oxide in the first half of this month was 519,500 yuan per ton, up 9.45% from the previous month and up 73.76% year on year;</p >

The average average price of praseodymium-neodymium alloy in the first half of this month was 641,000 yuan per ton, up 8.57% from the previous month and 80.08% from the same period last year;</p >

The average basic price of neodymium oxide in the first half of this month was 507,600 yuan per ton, up 4.46% from the previous month and up 69.49% year on year;

The average basic price of neodymium metal in the first half of this month was 621,200 yuan per ton, up 3.35% from the previous month and up 61.91% year on year;

The average basic price of praseodymium oxide in the first half of this month was 536,900 yuan per ton, up 4.25% from the previous month and up 75.60% year on year;

The average basic price of sintered NdFeB in the first half of this month was 154,000 yuan per ton, unchanged from the previous month and up 20.78% year on year.

Businesses that produce neodymium-iron-boron engines and engines for new energy vehicles, the best in these two areas, can double their shares.

Many companies produce NdFeB. They are in Zhejiang and Jiangxi.

The origin of rare earth elements varies. The origin of light rare earth elements and heavy rare earth elements is different,

The distribution of rare earth elements in my country shows an obvious regional concentration. 98% of the country's rare earths are concentrated in four regions, namely Baiyun-Obo in Baotou, Inner Mongolia, Gannan in Jiangxi, North Yuebei in Guangdong, and Liangshan in Sichuan. Among them, Baiyun Obo has the largest rare earth reserves, about 35 million tons, accounting for 83% of the country's total rare earth reserves and 38% of the world's total rare earth reserves. so. The Baiyun Obo rare earth deposit is not only the largest rare earth deposit in my country, but also the largest rare earth deposit in the world

Compared to the northern region, the rare earth mines in the southern region are medium and high concentration rare earth resources, mainly distributed in Ganzhou, Jiangxi and Longyan, Fujian Province. Lanthanum, cerium, praseodymium and neodymium light rare earths account for more than 98% of medium and heavy rare earth ores, and the proportion of medium and heavy rare earths is only 1% to 2%, which is a typical bastnäsite. Among them, the content of europium and yttrium is higher than in similar foreign deposits.yakh, and single ores of rare earth minerals are easy to isolate and smelt.

In addition to the above areas, Panzhihua, Sichuan, a significant amount of light rare earth resources have also been discovered. The Panxi Rift Belt contains the world's third largest reserves of light rare earth ores.

The main mining areas for medium and heavy ion type rare earth elements in the six southern provinces are mainly distributed in 17 cities of the six southern provinces, including Hezhou City, Chongzuo City, Wuzhou City, Guigang City, and Yulin City in Guangxi Province. Zhuang Autonomous Region; Longyan City, Sanming City in Fujian Province; Ganzhou City, Jiangxi Province; Yongzhou City, Chenzhou City, Hunan Province; Heyuan City, Qingyuan City, Meizhou City, Shaoguan City, Jieyang City, Guangdong Province; Chuxiong City, Dehong Prefecture, Yunnan Province.

Theoretically, companies located close to the place of production will have a greater advantage.