Method for remarkably improving coercive force of cerium-rich neodymium-iron-boron magnet

Abstract

The invention provides a method for remarkably improving the coercive force of a cerium-rich neodymium-iron-boron magnet. The method comprises the following steps: (1) preparing cerium-rich magnetic powder I of which the cerium content accounts for not less than 24% of the total content of rare earth; (2) preparing cerium-poor rare earth-rich magnetic powder II in which the cerium content is not more than 24% of the total content of rare earth and the total content of the rare earth is more than 30%; (3) preparing low-melting-point nano metal powder III by taking at least one of Ga, Al, Zn and Sn as a raw material; (4) magnetic powder I, magnetic powder II and metal powder III with the mass being m1, m2 and m3 are taken and mixed uniformly according to the ratio that (m2 + m3): m1 is larger than or equal to 1 and larger than 0, and after uniform mixing, orientation forming, sintering and cutting machining are conducted to prepare a base material; and (5) the surface of the base material is coated with the diffusion source, the weight of the base material is increased by md, 0.05 > = md: (m1 + m2 + m3) > 0, then heat treatment is conducted, and the cerium-rich neodymium-iron-boron magnet is obtained. The prepared cerium-rich neodymium-iron-boron magnet has the advantages of being excellent in performance, low in cost, high in cost performance and the like, and especially compared with a conventional cerium-rich neodymium-iron-boron magnet, the coercive force of the cerium-rich neodymium-iron-boron magnet is greatly improved.

Description

Technical Field

[0001] The invention discloses a method for significantly improving the coercive force of a cerium-rich NdFeB magnet, belonging to the technical field of NdFeB magnetic material preparation. Background Art

[0002] NdFeB has excellent magnetic properties and is widely used in electronics, power machinery, medical equipment, hardware machinery, computers, new energy, aerospace and other fields. It is an indispensable basic functional material. The production of NdFeB requires a large amount of expensive praseodymium and neodymium metals, which makes the preparation cost high. In addition, the proportion of praseodymium and neodymium in rare earth ores is relatively low. While the NdFeB industry is developing rapidly, the contradiction between supply and demand of rare earth resources such as praseodymium and neodymium is becoming increasingly prominent. These reasons have greatly restricted the use of NdFeB and the rapid development of the industry.

[0003] Cerium-rich NdFeB uses high-abundance, low-price cerium to replace high-priced rare earths such as praseodymium and neodymium in NdFeB, and ensures that the magnetic properties such as remanence and maximum magnetic energy product are equivalent to those of NdFeB, which can greatly reduce production costs. Because cerium in the original ore is a high-abundance element, the current application range of cerium is relatively narrow, resulting in a large amount of cerium hoarding. Broadening the application of cerium is conducive to the balanced utilization of rare earth resources and effectively alleviates the contradiction between supply and demand of rare earth resources such as praseodymium and neodymium. However, the heat resistance of cerium-rich NdFeB is poor. The use of "grain boundary diffusion" can improve the coercivity of the material and achieve the purpose of improving heat resistance. "Grain boundary diffusion" uses compounds and alloys containing dysprosium and terbium as diffusion sources, which are coated on the surface of the substrate, and then diffused into the substrate through heat treatment. It can greatly improve the coercivity and heat resistance of the material while minimizing the amount of dysprosium and terbium. At present, this technology is widely used in the preparation process of NdFeB. However, compared with conventional NdFeB, when the ratio of cerium substitution to the total rare earth content of Cerium-rich NdFeB magnets reaches and exceeds 24%, the substrate will generate CeFe2 phase during the sintering process, blocking the channel of the grain boundary diffusion process. At the same time, CeFe2 will react with Dy and Tb to generate (Dy, Ce)Fe2 phase or (Tb, Ce)Fe2 phase, affecting the effective diffusion of dysprosium and terbium elements, making it difficult to increase the weight of the substrate, and ultimately affecting the improvement of the coercive force of the Cerium-rich NdFeB magnet after diffusion. There is still a lot of work to be done to improve its heat resistance. In view of these reasons, the current Cerium-rich NdFeB is mostly used in fields with low requirements for heat resistance, which is not conducive to the development of Cerium-rich NdFeB.

[0004] The present invention is proposed in view of the difficult problems existing in the prior art. Summary of the invention

[0005] The purpose of the present invention is to solve the above-mentioned problems existing in the prior art and provide a method for significantly improving the coercive force of cerium-rich NdFeB magnets.

[0006] The present invention discloses a method for significantly improving the coercive force of a cerium-rich neodymium iron boron magnet, comprising the following steps:

[0007] 1. A method for significantly improving the coercivity of a cerium-rich NdFeB magnet, comprising the following steps:

[0008] Step 1: By ingredient (LRE 100-a Ce a ) b Fe e B c M d Prepare cerium-rich magnetic powder I, wherein LRE is at least one of Pr and Nd; M is at least one of Co, Ti and Zr, a is the percentage of cerium content in the total rare earth content in the magnetic powder I, 100≥a>24, b, c, d and e are the contents of the components in the magnetic powder I, 30>b>20, 1.1>c>0.8, 3>d>1, and e=100-bcd;

[0009] Step 2: By ingredient (LRE 100-u Ce u ) x Fe w B y M z Preparation of cerium-poor rare earth-rich magnetic powder II, wherein LRE is at least one of Pr and Nd; M is at least one of Al, Ga, Cu and Sn; u is the percentage of cerium content in the total rare earth content in magnetic powder II, 24≥u>0, x, y, z and w are the contents of the components in magnetic powder II, 95>x>30, 1.1>y>0, 3>z>1, and w=100-xyz;

[0010] Step 3: using at least one of Ga, Al, Zn and Sn as a raw material to prepare low melting point nano metal powder III;

[0011] Step 4: Take m1 of cerium-rich magnetic powder I, m2 of cerium-poor rare earth-rich magnetic powder II and m3 of low melting point nano metal powder III, mix them according to 1≥(m2+m3):m1>0, and after they are uniformly mixed, form them by orientation, sinter and cut them into cerium-rich NdFeB substrate;

[0012] Step 5: Apply the diffusion source to the surface of the substrate to increase the weight of the substrate m d , where 0.05 ≥ m d: (m1+m2+m3)>0, the diffusion sources include at least one of hydride, fluoride, Dy-Me (Me is at least one of La, Ce, Pr, Nd, Ho, Y, Al, Ga, Cu, Sn, Zn, and Co) alloy of dysprosium, and hydride, fluoride, Tb-Me (Me is at least one of La, Ce, Pr, Nd, Ho, Y, Al, Ga, Cu, Sn, Zn, and Co) alloy of terbium, and then heat treatment is performed to obtain the cerium-rich NdFeB magnet of the present invention.

[0013] The advantages and beneficial effects of the present invention compared with the prior art are as follows:

[0014] 1. Using low-cost cerium to replace the expensive praseodymium and neodymium in NdFeB, and making the percentage of cerium in the total rare earth content not less than 24% to obtain cerium-rich NdFeB magnets can greatly reduce the preparation cost while ensuring the same magnetic properties. It has an excellent cost-effectiveness, greatly improves the competitiveness of (cerium-rich) NdFeB magnets, and is conducive to promoting the development of the industry.

[0015] 2. The cerium-rich NdFeB substrate is prepared by the grain boundary control technology with a reasonable combination of three powders. Due to the presence of the cerium-poor rare earth-rich magnetic powder II, Nd and Pr will inhibit the reaction of Dy or Tb with the CeFe2 phase during sintering. In addition, the added low-melting point metal nanopowder III reduces the melting point of the magnet grain boundary phase, which can increase the diffusion depth of Dy and or Tb in the diffusion source into the interior of the magnet during grain boundary diffusion, and the weight gain is obvious, thereby significantly improving the coercive force of the magnet after diffusion. DETAILED DESCRIPTION

[0016] The present invention is further illustrated with reference to the embodiments, but is not limited thereto.

[0017] Example 1

[0018] A method for significantly improving the coercivity of a cerium-rich NdFeB magnet comprises the following steps:

[0019] 1. By composition (Nd 74.90 Ce 25.10 ) 29.20 Fe 68.28 B 1.02 Co 0.80 Ti 0.50 Zr 0.20 preparing cerium-rich magnetic powder I with an average particle size of 3 to 4 μm;

[0020] 2. By composition (Pr 38.00 Nd 59.90 Ce 2.10 ) 60.00 Fe 36.88 B 1.02 Al 0.50 Cu0.80 Ga 0.30 Sn 0.50 Preparation of 3-4 μm cerium-poor rare earth-rich magnetic powder II;

[0021] 3.According to the composition of Ga 2.00 Al 84.30 Zn 10.70 Sn 3.00 Preparation of low melting point nano metal powder III with a particle size not exceeding 100 nm;

[0022] 4. The three powders are mixed, wherein the mass of the cerium-rich magnetic powder I is 9.5 kg, the mass of the cerium-poor rare earth-rich magnetic powder II is 0.4 kg, and the mass of the low melting point nano metal powder III is 0.1 kg. After being mixed evenly, the mixture is oriented, sintered, and cut to form a cerium-rich NdFeB substrate;

[0023] 5. Take the cerium-rich NdFeB magnetic sheet with a mass of 55.10 g and a size (L×B×H) of 45.00 mm×30.00 mm×5.00 mm as the substrate, and 67.00 Zn 33.00 After the alloy diffusion source was coated on the surface of the substrate, the weight gain of the substrate was 0.58 g, and then heat treatment was performed to obtain the high cerium NdFeB magnet of the present invention. The magnetic properties of the magnet after diffusion were measured, and the results are shown in Table 1 below:

[0024] Table 1. Test results of main magnetic properties of the diffused magnet at 20°C in Example 1

[0025]

[0026] Example 2

[0027] A method for significantly improving the coercivity of a cerium-rich NdFeB magnet comprises the following steps:

[0028] 1. By composition (Nd 50.90 Ce 49.10 ) 29.25 Fe 68.23 B 1.02 Co 0.80 Ti 0.50 Zr 0.20 Step I of preparing cerium-rich magnetic powder with a particle size of 3 to 4 μm;

[0029] 2. By composition (Pr 28.60 Nd 69.90 Ce 1.5 ) 60.50 Fe 35.18 B 1.02 Al 1.50 Cu 1.00 Ga 0.30 Sn0.50 Preparation of cerium-poor rare earth-rich magnetic powder II with a particle size of 3 to 4 μm;

[0030] 3.According to the composition of Al 79.83 Zn 10.17 Sn 10.00 Preparation of low melting point nano metal powder III with a particle size not exceeding 100 nm;

[0031] 4. The three powders are mixed, wherein the mass of the cerium-rich magnetic powder I is 9.4 kg, the mass of the cerium-poor rare earth-rich magnetic powder II is 0.4 kg, and the mass of the low melting point nano metal powder III is 0.2 kg. After being mixed evenly, the mixture is oriented, sintered, and cut to form a cerium-rich NdFeB substrate;

[0032] 5. Take the cerium-rich NdFeB magnetic sheet with a mass of 55.12 g and a size (L×B×H) of 45.01 mm×30.00 mm×5.00 mm as the substrate, and 67 Zn 33 After the alloy diffusion source was coated on the surface of the substrate, the weight gain of the substrate was 0.56 g, and then heat treatment was performed to obtain the high cerium NdFeB magnet of the present invention. The magnetic properties of the magnet after diffusion were measured, and the results are shown in Table 2 below:

[0033] Table 2. Test results of main magnetic properties of the diffused magnet at 20°C in Example 2

[0034]

[0035] Comparative Example 3

[0036] A method for significantly improving the coercivity of a cerium-rich NdFeB magnet comprises the following steps:

[0037] 1. By composition (Nd 74.90 Ce 25.10 ) 29.20 Fe 68.28 B 1.02 Co 0.80 Ti 0.50 Zr 0.20 Step I of preparing cerium-rich magnetic powder with a particle size of 3 to 4 μm;

[0038] 2. By composition (Pr 38.00 Nd 59.90 Ce 2.10 ) 60.00 Fe 36.88 B 1.02 Al 0.50 Cu 0.80 Ga 0.30 Sn 0.50 Preparation of cerium-poor rare earth-rich magnetic powder II with a particle size of 3 to 4 μm;

[0039] 3.According to the ingredients Ga 2.00 Al 84.30 Zn 10.70 Sn 3.00 Preparation of low melting point nano metal powder III with a particle size not exceeding 100 nm;

[0040] 4. Take 10 kg of the cerium-rich magnetic powder I in step 1, and prepare a cerium-rich NdFeB substrate 1 by orientation molding, sintering and cutting;

[0041] 5. Take the cerium-rich NdFeB magnetic sheet substrate 1 with a mass of 55.15 g and a size (L×B×H) of 45.02 mm×30.00 mm×5.00 mm in step 4, and 67.00 Zn 33.00 After the alloy diffusion source was coated on the surface of the substrate, the weight gain of the substrate was 0.57 g, and then heat treatment was performed to obtain a comparative cerium-rich NdFeB magnet, and the magnetic properties of the magnet after diffusion were measured, and the results are shown in Table 3;

[0042] 6. The three powders of steps 1, 2 and 3 are mixed, wherein the mass of the cerium-rich magnetic powder I is 9.5 kg, the mass of the cerium-poor rare earth-rich magnetic powder II is 0.4 kg, and the mass of the low melting point nano metal powder III is 0.1 kg. After mixing evenly, the mixture is oriented, sintered and cut to form a high cerium NdFeB substrate 2;

[0043] 7. Take the cerium-rich NdFeB magnetic sheet with a mass of 55.10 g and a size (L×B×H) of 45.00 mm×30.00 mm×5.00 mm as the substrate, and 67.00 Zn 33.00 After the alloy diffusion source was coated on the surface of the substrate, the weight gain of the substrate was 0.58 g, and then heat treatment was performed to obtain the cerium-rich NdFeB magnet of the present invention. The magnetic properties of the magnet after diffusion were measured, and the results are shown in Table 3 below:

[0044] Table 3. Test results of main magnetic properties of diffused magnet at 20°C in Comparative Example 3

[0045]

Claims

1. A method for significantly improving the coercivity of cerium-rich NdFeB magnets. Its characteristics include the following steps: Step 1: Prepare cerium-rich magnetic powder I according to the composition (LRE100-aCea)bFeeBcMd, wherein LRE is at least one of Pr and Nd; M is at least one of Co, Ti and Zr, a is the percentage of cerium content in the total rare earth content in the magnetic powder I, 100≥a>24, b, c, d and e are the contents of the components in the magnetic powder I, 30>b>20, 1.1>c>0.8, 3>d>1, and e=100-bcd; Step 2: Prepare cerium-poor rare earth-rich magnetic powder II according to the composition (LRE100-uCeu)xFewByMz, wherein LRE is at least one of Pr and Nd; M is at least one of Al, Ga, Cu, and Sn, u is the percentage of cerium content in the total rare earth content in magnetic powder II, 24≥u>0, x, y, z, w are the contents of each component in magnetic powder II, 95>x>30, 1.1>y>0, 3>z>1, w=100-xyz; Step 3: using at least one of Ga, Al, Zn and Sn as a raw material to prepare low melting point nano metal powder III; Step 4: Take m1 of cerium-rich magnetic powder I, m2 of cerium-poor rare earth-rich magnetic powder II and m3 of low melting point nano metal powder III, mix them according to 1≥(m2+m3):m1>0, and after they are uniformly mixed, form them by orientation, sinter and cut them into cerium-rich NdFeB substrate; Step 5: Coat the diffusion source on the surface of the substrate to increase the weight of the substrate by md, wherein 0.05≥md: (m1+m2+m3)>0, and the diffusion source includes at least one of hydride, fluoride, Dy-Me (Me is at least one of La, Ce, Pr, Nd, Ho, Y, Al, Ga, Cu, Sn, Zn, and Co) alloy of dysprosium, and hydride, fluoride, and Tb-Me (Me is at least one of La, Ce, Pr, Nd, Ho, Y, Al, Ga, Cu, Sn, Zn, and Co) alloy of terbium, and then perform heat treatment to obtain the cerium-rich NdFeB magnet of the present invention.

Images