Cerium-containing neodymium iron boron magnet and preparation method thereof

Abstract

The invention discloses a cerium-containing neodymium iron boron magnet and a preparation method thereof. The magnet is obtained through diffusion of the Ce-containing neodymium iron boron base material, Ce-rich phases and Nd-rich phases in the magnet are distributed in a balanced mode, and the magnetic performance is excellent.

Description

Technical Field

[0001] This invention relates to the field of neodymium iron boron permanent magnet technology, specifically to a cerium (Ce)-containing neodymium iron boron magnet and its preparation method. Background Technology

[0002] Neodymium iron boron (NdFeB) magnets have become an essential material for high-performance motors and are widely used in new energy vehicle drive motors, wind turbines, and home appliance compressors. In recent years, with the continuous development of emerging industries such as humanoid robots and drones, the demand for NdFeB permanent magnets has been increasing year by year. However, with the soaring prices of rare earth raw materials required for NdFeB, in order to reduce magnet costs and decrease Nd usage, people have begun to use elements with greater reserves and lower prices to replace Nd.

[0003] Cerium (Ce) is abundant in the Earth's crust and inexpensive, attracting extensive research. Studies have found that replacing Nd with Ce can significantly reduce the cost of permanent magnets. However, Ce₂Fe 14 B's inherent magnetic properties are lower than those of Nd2Fe. 14 B, (Ce2Fe) 14 B: Js = 1.17T, HA = 3T, Nd2Fe 14 (B: Js = 1.61 T, HA = 7.6 T), therefore a large amount of Ce replaces Nd2Fe. 14 In NdFeB magnets, the magnetic dilution effect limits coercivity, reduces magnet performance, and restricts the application of NdCeFeB sintered bodies. The substitution of large amounts of Ce readily forms a non-ferromagnetic CeFe2 phase at the grain boundaries of NdCeFeB magnets. The formation of the CeFe2 phase not only reduces the remanent magnetization of the magnet but also consumes excess rare earth elements (RE) in the alloy, reducing RE-rich grain boundary phases. The non-ferromagnetic CeFe2 phase weakens the decoupling effect between the main phase grains, reducing the magnet's coercivity. The simplest and most direct way to suppress the formation of the CeFe2 phase is to control the amount of Ce added. The higher the Ce content, the greater the driving force for CeFe2 phase formation, and the easier it is to form coarse CeFe2 phases, thus making it difficult to prepare NdCeFeB magnets with high Ce content and high coercivity.

[0004] To address the above issues, a small amount of heavy rare earth elements (Dy, Tb) is introduced through diffusion to further stabilize grain boundaries and reduce the formation of the CeFe2 phase. Simultaneously, grain boundary diffusion effectively enhances the magnet's coercivity while maintaining a slight decrease in remanence. In traditional NdCeFeB substrate magnets, the coexistence of Ce and Nd in the grain boundaries, along with the difference in their diffusion rates towards the diffusion source elements, easily leads to an uneven distribution of Ce-rich and Nd-rich phases within the grain boundary phase. This results in Ce segregation and an inability to suppress the formation of the CeFe2 phase, leading to grain boundary structural defects and worsening the magnet's coercivity (Hcj) and remanence (Br). Summary of the Invention

[0005] To address the above shortcomings, the technical solution of this invention is as follows: A method for preparing Ce-containing NdFeB magnets is provided. By optimizing the substrate formulation, diffusion source composition and process parameters, the method stabilizes grain boundaries, suppresses CeFe2 precipitation, balances Ce / Nd distribution in the grain boundary phase, reduces internal defects in the magnet, and improves overall magnetic properties.

[0006] This invention is achieved through the following technical solution: This invention provides a Ce-containing neodymium iron boron magnet, which is obtained by diffusion from a Ce-containing neodymium iron boron substrate; The Ce mass content in the grain boundary phase of the Ce-containing NdFeB magnet is Ce4, the Nd mass content in the grain boundary phase is Nd4, and 0.2≤Ce4 / Nd4≤0.7; The mass content of Ce in the grain boundary phase of the Ce-containing NdFeB substrate is Ce2, 2% ≤ Ce4 - Ce2 ≤ 13%; The mass content of Nd in the grain boundary phase of the Ce-containing NdFeB substrate is Nd2, 3%≤Nd4-Nd2≤15%; The Ce mass content in the main phase of the Ce-containing NdFeB magnet is Ce3, and Ce3 / Ce4 ≥ 0.06.

[0007] According to embodiments of the present invention, 0.25≤Ce4 / Nd4≤0.7, 0.4≤Ce4 / Nd4≤0.6, or 0.45≤Ce4 / Nd4≤0.55; for example, Ce4 / Nd4=0.33, 0.35, 0.38, 0.40, 0.428, 0.45, 0.48, 0.50, 0.53, 0.55, 0.60, 0.65, 0.70, or 0.75.

[0008] According to an embodiment of the present invention, 2%≤Ce4-Ce2≤10% or 2%≤Ce4-Ce2≤8%, for example, Ce4-Ce2=2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or 13%.

[0009] According to an embodiment of the present invention, 3%≤Nd4-Nd2≤12% or 3%≤Nd4-Nd2≤10%, for example, Nd4-Nd2=3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11% or 12%.

[0010] According to embodiments of the present invention, 0.06 ≤ Ce3 / Ce4, for example 0.08 ≤ Ce3 / Ce4, and also 0.06 ≤ Ce3 / Ce4 ≤ 0.40, 0.2 ≤ Ce3 / Ce4 ≤ 0.35, or 0.25 ≤ Ce3 / Ce4 ≤ 0.35, exemplarily Ce3 / Ce4 = 0.06, 0.1, 0.15, 0.2, 0.25, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, or 0.4.

[0011] According to an embodiment of the present invention, 4%≤Ce3≤14% or 6%≤Ce3≤10%, for example, Ce3=4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or 13%.

[0012] According to embodiments of the present invention, 17%≤Ce4≤58%, 17%≤Ce4≤40%, or 20%≤Ce4≤30%, for example, Ce4=20%, 25%, 30%, 40%, 45%, 50%, or 55%.

[0013] According to an embodiment of the present invention, 6%≤Ce2≤45% or 6%≤Ce2≤20%, for example, Ce2=8%, 10%, 12%, 15%, 20%, 25%, 30%, 35% or 40%.

[0014] According to an embodiment of the present invention, 50%≤Nd4≤85% or 60%≤Nd4≤80%, for example, Nd4=53%, 55%, 58%, 60%, 63%, 65%, 68%, 70%, 75% or 80%.

[0015] According to an embodiment of the present invention, 35%≤Nd2≤80% or 55%≤Nd2≤75%, for example 40%, 45%, 50%, 55%, 60%, 63%, 65%, 68%, 70%.

[0016] According to an embodiment of the present invention, the diffusion source used for diffusion is RLRHM. RL is selected from one or more of Pr, Nd, La and Ce, with a preferred RL content of W. RL ≥60wt%, for example, 60wt%≤W RL ≤90wt% RH is selected from one or both of Dy and Tb, with a preferred RH content of W. RH ≥0wt%, for example, 0wt%≤W RH ≤20wt% M is selected from one or more of Al, Cu and Ga, with M content preferably ≥10wt%, for example 10wt%≤M content≤25wt%.

[0017] According to some embodiments of the present invention, in the diffusion source, RL is selected from Pr, M is selected from Al and Cu, and / or RH is selected from Tb.

[0018] According to some embodiments of the present invention, the diffusion source is Pr 80 Al 10 Cu 10 or (Pr 80 Tb 20 ) 80 Al 10 Cu 10 The element subscript represents the mass content of that element.

[0019] According to an embodiment of the present invention, the average particle size of the diffusion source is 3~5μm, and / or the particle size range is 1μm~12μm, for example 1μm~10μm, 1.3μm~10.2μm.

[0020] According to an embodiment of the present invention, the diffusion includes: a Ce-containing NdFeB substrate with a diffusion source slurry coated on its surface is stacked in multiple layers in an alternating manner, and the empty box rate is ≤3%.

[0021] According to an embodiment of the present invention, the diffusion source slurry comprises the diffusion source, fatty acid esters (e.g., glycerides) and organic solvents (e.g., ethanol), for example, a mixture of diffusion source, fatty acid esters (e.g., glycerides) and organic solvents (e.g., ethanol) in a mass ratio of 80:(10~18):(2~10) (e.g., 80:(12~16):(4~8)).

[0022] According to an embodiment of the present invention, the mass content of Nd in the main phase of the Ce-containing NdFeB magnet is Nd3, 16%≤Nd3≤32%, for example Nd3=18%, 20%, 22%, 25%, 27%, 30%.

[0023] According to an embodiment of the present invention, the mass content of Ce in the main phase of the Ce-containing NdFeB substrate is Ce1, 1.5%≤Ce1≤8%, for example Ce1=2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%.

[0024] According to an embodiment of the present invention, the raw material of the Ce-containing NdFeB substrate (denoted as R-Fe-B-M1) comprises the following elements by weight percentage: The content of rare earth element R (e.g., Nd+Ce) is not less than 29wt% and not more than 32.2wt%, of which Ce ≥ 5wt%; The content of B is greater than 0.90 wt% and not greater than 1.0 wt%; M1 is selected from Ga and Cu, and optionally includes or excludes at least one of Al, Zr, Ti and Co. The content of M1 is greater than 0 and not greater than 2.5 wt%, and Ga accounts for 0 to 0.5 wt% of the total amount of M1, Cu accounts for 0 to 0.4 wt% of the total amount of M1, and the content of Ga and Cu is not 0.

[0025] According to an embodiment of the present invention, the Br (20°C) of the Ce-containing neodymium iron boron magnet is 1.345~1.37T, for example 1.35~1.36T; and / or, the Hcj (20°C) is 1400~2100kA / m, for example 1400~1800kA / m.

[0026] The present invention also provides a Ce-containing neodymium iron boron magnet, wherein, The mass content of Ce in the grain boundary phase is Ce4, and the mass content of Nd in the grain boundary phase is Nd4, with 0.2≤Ce4 / Nd4≤0.7, for example 0.25≤Ce4 / Nd4≤0.7, 0.4≤Ce4 / Nd4≤0.6, or 0.45≤Ce4 / Nd4≤0.55; exemplary Ce4 / Nd4 = 0.33, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.5, 0.53, 0.55, 0.6, 0.65, 0.7, or 0.75; The Ce content in the main phase is Ce3, and Ce3 / Ce4 ≥ 0.06, for example, Ce3 / Ce4 ≥ 0.08, or 0.06 ≤ Ce3 / Ce4 ≤ 0.40, 0.2 ≤ Ce3 / Ce4 ≤ 0.35 or 0.25 ≤ Ce3 / Ce4 ≤ 0.35, for example Ce3 / Ce4 = 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15 or 0.16; The mass content of Nd in the main phase is Nd3, 16%≤Nd3≤32%, for example Nd3=18%, 20%, 22%, 25%, 27%, 30%.

[0027] According to an embodiment of the present invention, 4%≤Ce3≤14% or 6%≤Ce3≤10%, for example, Ce3=4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or 13%.

[0028] According to embodiments of the present invention, 17%≤Ce4≤58%, 17%≤Ce4≤40%, or 20%≤Ce4≤30%, for example, Ce4=20%, 25%, 30%, 40%, 45%, 50%, or 55%.

[0029] According to an embodiment of the present invention, 50%≤Nd4≤85% or 60%≤Nd4≤80%, for example, Nd4=53%, 55%, 58%, 60%, 63%, 65%, 68%, 70%, 75% or 80%.

[0030] According to an embodiment of the present invention, the Br (20°C) of the Ce-containing neodymium iron boron magnet is 1.345~1.37T, for example 1.35~1.36T; and / or, the Hcj (20°C) is 1400~2100kA / m, for example 1400~1800kA / m.

[0031] According to an embodiment of the present invention, the Ce-containing NdFeB magnet is obtained by diffusion from a Ce NdFeB substrate; The mass content of Ce in the grain boundary phase of the Ce NdFeB substrate is Ce2, 2% ≤ Ce4 - Ce2 ≤ 13%; The mass content of Nd in the grain boundary phase of the Ce-containing NdFeB substrate is Nd2, 3%≤Nd4-Nd2≤15% or 3%≤Nd4-Nd2≤12%; The diffusion source used for diffusion is RLRHM, and the diffusion and diffusion source are defined as shown above.

[0032] According to embodiments of the present invention, 6% ≤ Ce2 ≤ 45% or 6% ≤ Ce2 ≤ 20%, for example, Ce2 = 8%, 10%, 12%, 15%, 20%, 25%, 30%, 35%, or 40%; And / or, 35%≤Nd2≤80% or 55%≤Nd2≤75%, for example 40%, 45%, 50%, 55%, 60%, 63%, 65%, 68%, 70%.

[0033] This invention also provides the application of Ce-containing NdFeB substrate in the preparation of Ce-containing NdFeB magnets; The Ce-containing NdFeB substrate and the Ce-containing NdFeB magnet have the limitations shown above.

[0034] The present invention also provides a method for preparing the above-mentioned Ce-containing NdFeB magnet, the method comprising: placing multiple layers of Ce-containing NdFeB substrate coated with diffusion source slurry in an alternating manner, with a material box void ratio ≤3%, and obtaining the Ce-containing NdFeB magnet by diffusion; The Ce-containing NdFeB substrate, diffusion source, and diffusion source slurry are all subject to the limitations described above.

[0035] According to an embodiment of the present invention, the preparation of the Ce-containing NdFeB substrate (denoted as R-Fe-B-M1) includes: (1) The following elements are used to prepare neodymium iron boron alloy quick-setting sheets by smelting and crushing. The content of rare earth element R (e.g., Nd+Ce) is not less than 29wt% and not more than 32.2wt%, of which Ce ≥ 5wt%; The content of B is greater than 0.90 wt% and not greater than 1.0 wt%; M1 is selected from Ga and Cu, and optionally includes or excludes at least one of Al, Zr, Ti and Co. The content of M1 is greater than 0 and not greater than 2.5 wt%, and Ga accounts for 0 to 0.5 wt% of the total amount of M1, Cu accounts for 0 to 0.4 wt% of the total amount of M1, and the content of Ga and Cu is not 0. (2) The obtained magnetic powder is mixed with an antioxidant and then pressed and cold isostatically pressed to obtain a green body; For example, the antioxidant is a fatty acid ester, such as a glyceride; (3) The green blank is sintered and aged to obtain the Ce-containing neodymium iron boron substrate.

[0036] According to an embodiment of the present invention, the preparation of the diffusion source slurry includes: The raw materials required for the diffusion source are proportioned according to the target element content. The diffusion source alloy sheet is prepared by rapid solidification and spinning process. After being crushed, the powder with the target particle size is obtained. Then, the powder particles are mixed with fatty acid esters (such as glycerides) and organic solvents (such as ethanol) to prepare diffusion source slurry. The target element content is: RL content ≥ 60wt%, for example, 60wt% ≤ RL content ≤ 90wt%, with examples being 70wt%, 75wt%, 80wt%, and 85wt%. RH content ≤ 0wt% ≤ 20wt%, for example 0wt%, 5wt%, 10wt%, 15wt%; M content ≥ 10wt%, for example 10wt% ≤ M content ≤ 25wt%, such as 10wt%, 12wt%, 15wt%, 18wt%, 20wt%; The target particle size is: the average particle size of the diffusion source is 3~5μm, and / or the particle size range is 1~12μm, for example 1~10μm, 1.3~10.2μm; The mass ratio of powder particles to fatty acid esters and organic solvents is 80:(10~18):(2~10), for example 80:(12~16):(4~8), and an exemplary 80:15:5.

[0037] According to an embodiment of the present invention, the method for preparing the Ce-containing NdFeB magnet includes: (S1) The Ce-containing NdFeB substrate is cut into sheets with the thickness direction being the direction in which the magnet is easily magnetized; (S2) The sheet containing Ce NdFeB substrate is placed in a degreasing agent solution for ultrasonic cleaning, and then successively subjected to acid washing, water washing and drying for later use. (S3) Coat the surface of the sheet obtained in step (S2) with the diffusion source slurry until the sheet weight increases by 0.25% to 1.0%, for example, 0.5% to 0.8%; (S4) The sheet coated in step (S3) is subjected to diffusion treatment to obtain the Ce-containing neodymium iron boron magnet; During the diffusion process, a material box matching the material is used to ensure that the empty rate of the material box is ≤3% (that is, the volume ratio of magnets in the material box is ≥97%), and the material is placed in the graphite material box in multiple layers of staggered stacking. For example, the diffusion is a two-stage heat treatment diffusion, where the temperature of the first-stage heat treatment diffusion is 800~950℃ and the time is 4~8h; and the temperature of the second-stage heat treatment diffusion is 400~550℃ and the time is 2~6h.

[0038] The beneficial effects of this invention are: This invention provides a Ce-containing neodymium iron boron magnet with an internal balanced distribution of Ce-rich and Nd-rich phases, which exhibits excellent magnetic properties.

[0039] By optimizing the grain boundary diffusion process, the uniformity of Ce-rich and Nd-rich phases inside the magnet can be improved, thereby enhancing its magnetic properties.

[0040] By controlling the change in Ce / Nd content after diffusion, a uniform distribution of Ce-rich and Nd-rich phases can be achieved, reducing grain boundary defects.

[0041] The low vacancy rate (≤3%) of diffusion and the multi-layer staggered stacking method reduce the volatilization of rare earth elements at high temperatures, reduce the uneven distribution of diffusion sources during diffusion, eliminate Ce / Nd composition fluctuations at grain boundaries, balance the distribution of Ce-rich and Nd-rich phases, reduce internal defects of the magnet, and improve the magnetic properties of the magnet.

[0042] By adding RL and RH in combination, and combining the grain boundary wetting effect of element M, the penetration efficiency of the diffusion source at the grain boundary is improved, RL is diffused to the grain boundary, and Ce / Nd segregation is suppressed.

[0043] Terminology Definitions and Explanations "Multi-layer staggered stacking" refers to stacking two or more layers of sheets, with contact between layers and sheets, and the vertical edges of adjacent layers are not aligned; see details. Figure 1 . Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the multi-layered staggered stacking arrangement in step (4) of the embodiment; Figure 2 This is a schematic diagram showing the stacking arrangement of magnets between layers in Comparative Examples 1-1 and 1-2; Figure 3 This is a schematic diagram of the irregular arrangement of magnets between layers in Comparative Examples 1-5. Detailed Implementation

[0045] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0046] Test methods Vacancy rate: Products are neatly arranged in rectangular blocks. The length, width, and height after arrangement are measured to obtain the magnet volume V1. The internal length, width, and height of the material box are measured to calculate the material box volume V2. Vacancy rate = 1 - V1 / V2 * 100%.

[0047] Performance testing: The obtained Ce-containing NdFeB matrix and sintered R-Fe-B magnet were processed into sample pieces with a thickness of 2.9 mm, a length of 7 mm, and a width of 7 mm from the center position. After being saturated with a 5T pulsed magnetic field, the demagnetization curve of the magnet at 20℃ was tested using an NIM-10000 measuring instrument.

[0048] Methods for testing the elemental composition of the main phase and grain boundary phase in substrate and magnet products: Five main phase grain regions and five grain boundary phase regions are randomly selected in the field of view image using a backscattered scanning electron microscope. Five points are randomly selected from each region for fixed-point analysis, for a total of 25 points. The average value of the 25 points represents the composition value of the main phase and grain boundary phase regions.

[0049] The R-Fe-B magnet substrates used in the following examples and comparative examples, and their preparation methods, are as follows: (1) The raw materials required for R-Fe-B alloy are melted in an argon atmosphere at 1400℃ according to the target ratio and kept for 15 minutes to ensure the homogenization of the raw materials. Then, they are poured onto the surface of a rotating quenching roller to obtain a Nd-Fe-B alloy rapid solidification sheet with a thickness of about 0.3 mm. The raw materials required for the R-Fe-B alloy are formulated according to the target ratio: rare earth element R contains 22.5wt% Nd, 9wt% Ce; 1.0wt% B, 0.20wt% Ti, 0.10wt% Al, 0.1wt% Ga, 0.2% Cu, and 1.0wt% Co; the remainder is Fe and unavoidable impurities. (2) The R-Fe-B alloy rapid solidification sheet from step (1) is coarsely crushed in a hydrogen explosion furnace and then discharged under argon protection to reduce the oxidation of the coarse powder; the coarse powder after hydrogen explosion is directly ground by an air jet mill to obtain magnetic powder with a particle size of 1~10μm and an average particle size of 3.5μm. (3) Add 0.10wt% antioxidant diglyceride to the magnetic powder obtained in step (2) and continue mechanical stirring for 4 hours until uniformly dispersed; (4) The magnetic powder from step (3) is pressed into shape under vacuum and magnetic field strength of 2T and magnetic field orientation direction, and then cold isostatic pressing at 170MPa is used to obtain a green blank. (5) The green blank from step (4) is placed in a vacuum sintering furnace and sintered at 1070°C for 3 hours, and then tempered at 900°C and 520°C for 4 hours to obtain sintered R-Fe-B substrate MO.

[0050] The magnetic properties of the test substrate are Br=1.365T and Hcj=1110KA / m.

[0051] Backscattered scanning electron microscopy analysis of sintered R-Fe-B substrate M0 showed that the main phase and grain boundary phase composition were: Ce1 (main phase) 6%, Nd1 (main phase) 24%, Ce2 (grain boundary) 12%, and Nd2 (grain boundary) 65%.

[0052] Example 1 A method for preparing Ce-containing sintered R-Fe-B magnets, comprising the following steps: (1) The sintered R-Fe-B substrate is machined into a black sheet with a thickness of 3.0 mm × length of 35 mm × width of 21 mm, wherein the thickness direction is the direction in which the magnet is easily magnetized. The substrate is ultrasonically cleaned in degreasing agent solution, and then acid-washed, water-washed and dried in sequence. (2) Preparation of diffusion source slurry: Pr in a weight ratio of 8:1:1 80 Al 10 Cu 10 The alloy powder particles, diglycerides, and alcohol are mixed in a weight ratio of 80:15:5. The raw materials required for the diffusion source are prepared according to the target ratio by mass. The diffusion source alloy sheet is prepared by rapid solidification and spinning process. After crushing, the average particle size is 3.5μm. Then, the powder particles are mixed with glycerides and organic solvents in a weight ratio to prepare the diffusion slurry.

[0053] (3) The diffusion source slurry obtained in step (2) is coated on the two large surfaces of the black sheet after cleaning in step (1) in an atmospheric environment, with a coating amount of 0.7% of the weight of the black sheet.

[0054] (4) Stack the black sheets coated with diffusion source slurry obtained in step (3) in multiple layers in an alternating manner (see Figure 1 ) placed in a graphite box, with a box empty rate of 2%, in 2×10 -3 Two-stage heat treatment diffusion was carried out in a vacuum atmosphere. The first-stage heat treatment was performed at 900℃ for 6 hours, and the second-stage heat treatment was performed at 460℃ for 4 hours, resulting in Ce-containing sintered R-Fe-B magnets.

[0055] The test results showed that the Ce-containing sintered magnet had a Br=1.35T and an Hcj=1429KA / m.

[0056] Example 2 The preparation method of Example 2 is basically the same as that of Example 1, except that the diffusion source in step (2) is different. The diffusion source is (Pr 80 Tb 20 ) 80 Al 10 Cu 10 Alloy powder particles.

[0057] The test results showed that the Ce-containing sintered magnet had a Br=1.35T and an Hcj=1765KA / m.

[0058] Comparative Example 1-1 The difference between Comparative Example 1-1 and Example 1 lies in the preparation method: the empty box rate during the diffusion process in step (4) is 5%, and the magnets are stacked between layers (see...). Figure 2 ).

[0059] The test results showed that the Ce-containing sintered magnet had a Br=1.35T and an Hcj=1399kA / m performance.

[0060] Comparative Examples 1-2 The difference between Comparative Examples 1-2 and Example 1 lies in the preparation method: in step (4), the empty box rate is 20% during the diffusion process, and the magnets are stacked between layers (see...). Figure 2 ).

[0061] The test results showed that the Ce-containing sintered magnet had a Br=1.346T and an Hcj=1394kA / m performance.

[0062] Comparative Examples 1-3 The difference between the preparation methods of Comparative Examples 1-3 and Example 1 is that the diffusion source is Pr 50 Al 25 Cu 25 The alloy powder particles undergo primary heat treatment with a diffusion temperature of 890℃.

[0063] The test results showed that the Ce-containing sintered magnet had a Br=1.338T and an Hcj=1379kA / m performance.

[0064] Comparative Examples 1-4 The difference between the preparation methods of Comparative Examples 1-4 and Example 1 is that the diffusion source is Pr 40 Al 30 Cu 30 The alloy powder particles undergo a first-stage heat treatment diffusion temperature of 875℃.

[0065] The tested properties of the Ce-containing sintered magnet were Br=1.334T and Hcj=1359kA / m.

[0066] Comparative Examples 1-5 The difference between the preparation methods of Comparative Examples 1-5 and Example 1 is that the empty box rate during the diffusion process is 5%, and the magnets are irregularly arranged between layers (see...). Figure 3 ).

[0067] The test results showed that the Ce-containing sintered magnet had a Br=1.348T and an Hcj=1374kA / m performance.

[0068] Table 1 Br@20℃ / (T) Hcj@20℃ / (KA / m) Ce3 / wt% Nd3 / wt% Ce4 / wt% Nd4 / wt% (Ce4 / Nd4) / wt% Ce3 / Ce4 (Ce4-Ce2) / wt% (Nd4-Nd2) / wt% Substrate M0 1.365 1110 6 24 12 65 0.18 0.50 0 0 Example 1 1.35 1429 7 23 22 73 0.30 0.32 10 8 Example 2 1.35 1765 7 23 22 71 0.31 0.32 10 6 Comparative Example 1-1 1.35 1399 7.8 23 15 80 0.19 0.52 3 15 Comparative Examples 1-2 1.346 1394 6 25 14 81 0.17 0.43 2 16 Comparative Examples 1-3 1.338 1379 7.5 23 12.5 84 0.15 0.60 0.5 19 Comparative Examples 1-4 1.334 1359 7.3 23 12.5 83 0.15 0.58 0.5 18 Comparative Examples 1-5 1.348 1374 6 25 14 82 0.17 0.43 2 17 Comparing Example 1 with Comparative Examples 1-1 and 1-2, it can be seen that the increased empty space ratio of the magnet box leads to a decrease in the magnetic properties of the magnet, a greater difference in Ce and Nd content in the grain boundary phase of the magnet, and a worse uniformity between the Ce-rich and Nd-rich phases. Comparing Comparative Examples 1-1 and 1-5, it can be seen that under the same empty space ratio, the regularly arranged magnet layers exhibit better magnetic properties and better uniformity of the Ce-rich and Nd-rich phases in the grain boundaries compared to irregularly closely arranged layers.

[0069] Comparing Example 1 with Comparative Examples 1-3 and 1-4, it can be seen that the RE content in the diffusion source decreases, the difference between Ce and Nd content in the grain boundary phase increases, and the magnet performance decreases.

[0070] A comparison of Example 1 and Example 2 shows that the substitution of some light rare earth elements by some heavy rare earth elements in the diffusion source does not affect the uniformity of Ce-rich and Nd-rich phases in the grain boundaries of the magnet. Simultaneously, it can improve the magnetic properties of the magnet.

[0071] The exemplary embodiments of the present invention have been described above. However, the scope of protection of this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A Ce-containing neodymium iron boron magnet, characterized in that, The Ce-containing NdFeB magnet is obtained by diffusion from a Ce-containing NdFeB substrate; The Ce mass content in the grain boundary phase of the Ce-containing NdFeB magnet is Ce4, the Nd mass content in the grain boundary phase is Nd4, and 0.2≤Ce4 / Nd4≤0.7; The mass content of Ce in the grain boundary phase of the Ce-containing NdFeB substrate is Ce2, 2%≤Ce4-Ce2≤13%; The mass content of Nd in the grain boundary phase of the Ce-containing NdFeB substrate is Nd2, 3%≤Nd4-Nd2≤15%; The Ce mass content in the main phase of the Ce-containing NdFeB magnet is Ce3, and Ce3 / Ce4 ≥ 0.

06.

2. The Ce-containing NdFeB magnet according to claim 1, characterized in that, 0.35≤Ce4 / Nd4≤0.7, 0.4≤Ce4 / Nd4≤0.6, or 0.45≤Ce4 / Nd4≤0.55; And / or, 2%≤Ce4-Ce2≤10% or 2%≤Ce4-Ce2≤8%; And / or, 3%≤Nd4-Nd2≤12% or 3%≤Nd4-Nd2≤10%; And / or, 0.06≤Ce3 / Ce4≤0.40 or 0.25≤Ce3 / Ce4≤0.35; And / or, the mass content of Nd in the main phase of the Ce-containing NdFeB magnet is Nd3, 16%≤Nd3≤32%; And / or, the mass content of Ce in the main phase of the Ce-containing NdFeB substrate is Ce1, 1.5%≤Ce1≤8%.

3. The Ce-containing NdFeB magnet according to claim 1 or 2, characterized in that, 4%≤Ce3≤14%; And / or, 17%≤Ce4≤58%; And / or, 6%≤Ce2≤45%; And / or, 50%≤Nd4≤85%; And / or, 35%≤Nd2≤80%.

4. The Ce-containing NdFeB magnet according to claim 1, characterized in that, The diffusion source used for diffusion was RLRHM. RL is selected from one or more of Pr, Nd, La and Ce, with a preferred RL content of ≥60wt%, for example, 60wt%≤RL content≤90wt%; RH is selected from one or both of Dy and Tb, with RH content preferably ≥ 0 wt%, for example, 0 wt% ≤ RH content ≤ 20 wt%; M is selected from one or more of Al, Cu and Ga, with M content preferably ≥10wt%, for example, 10wt%≤M content≤25wt%; And / or, the average particle size of the diffusion source is 3.5 μm, and the particle size range is 1 μm to 12 μm.

5. The Ce-containing NdFeB magnet according to claim 1, characterized in that, The diffusion process includes: multiple layers of Ce-containing NdFeB substrate coated with diffusion source slurry are stacked in an alternating manner, with a material box empty rate of ≤3%; Preferably, the diffusion source slurry comprises the diffusion source, a fatty acid ester (e.g., a glycerol ester), and an organic solvent (e.g., ethanol), for example, a mixture of the diffusion source, fatty acid ester (e.g., a glycerol ester), and organic solvent (e.g., ethanol) in a mass ratio of 80:(10-18):(2-10).

6. The Ce-containing NdFeB magnet according to claim 1, characterized in that, The Br (20℃) of the Ce-containing neodymium iron boron magnet is 1.345~1.37T, and / or the Hcj (20℃) is 1400~2100kA / m.

7. The use of a Ce-containing NdFeB substrate in the preparation of the Ce-containing NdFeB magnet according to any one of claims 1-6; The mass content of Ce in the grain boundary phase of the Ce-containing NdFeB substrate is Ce2, 6% ≤ Ce2 ≤ 45%; The mass content of Nd in the grain boundary phase of the Ce-containing NdFeB substrate is Nd2, 35wt%≤Nd2≤80wt%; The mass content of Ce in the main phase of the Ce-containing NdFeB substrate is Ce1, where 1.5% ≤ Ce1 ≤ 8%.

8. The application according to claim 7, characterized in that, The raw material of the Ce-containing NdFeB substrate (denoted as R-Fe-B-M1) includes the following elements: The content of rare earth element R (e.g., Nd+Ce) is not less than 29wt% and not more than 32.2wt%, of which Ce ≥ 5wt%; The content of B is greater than 0.90 wt% and not greater than 1.0 wt%; M1 is selected from Ga and Cu, and optionally includes or excludes at least one of Al, Zr, Ti and Co. The content of M1 is greater than 0 and not greater than 2.5 wt%, and Ga accounts for 0-0.5 wt% of the total amount of M1, Cu accounts for 0-0.4 wt% of the total amount of M1, and the content of Ga and Cu is not 0.

9. The method for preparing the Ce-containing NdFeB magnet according to any one of claims 1 to 6, characterized in that, The preparation method includes: a Ce-containing NdFeB substrate coated with a diffusion source slurry is stacked in multiple layers with an alternating stacking, the empty space rate of the material box is ≤3%, and the Ce-containing NdFeB magnet is obtained by diffusion.

10. The preparation method according to claim 9, characterized in that, The preparation method includes: (S1) The Ce-containing NdFeB substrate is cut into sheets with the thickness direction being the direction in which the magnet is easily magnetized; (S2) The sheet containing Ce NdFeB substrate is placed in a degreasing agent solution for ultrasonic cleaning, and then successively subjected to acid washing, water washing and drying for later use. (S3) The diffusion source slurry is applied to the surface of the sheet obtained in step (S2) until the sheet weight increases by 0.25% to 1.0%; (S4) The sheet coated in step (S3) is subjected to diffusion treatment to obtain the Ce-containing neodymium iron boron magnet; During the diffusion process, a material box matching the material is used to ensure that the empty rate of the material box is ≤3%, and the material is placed in the graphite material box in multiple layers of staggered stacking. The diffusion is a two-stage heat treatment diffusion, with the first-stage heat treatment diffusion at a temperature of 800~950℃ and a time of 4~8h; and the second-stage heat treatment diffusion at a temperature of 400~550℃ and a time of 2~6h.

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