Neodymium iron boron rare earth magnet and preparation method thereof

Abstract

The present invention relates to a neodymium iron boron rare earth magnet and a preparation method thereof, and relates to the technical field of rare earth magnet preparation. By designing the coordinated diffusion of a diffusion source and a magnet, diffusion and aging treatment are performed to obtain a high-performance heavy rare earth-free magnet. The diffusion source is prepared by coating a layer of heavy rare earth-free alloy film on a diffusion source sheet, and performing aging treatment to form a new type of diffusion source, wherein the diffusion source sheet is R α RH δ M β B γ Fe 100‑α‑β‑γ‑δ The heavy rare earth-free film is a film with the chemical formula R n M m , aging treatment is carried out to form a new diffusion source; the chemical formula of NdFeB magnet is R a M 1b M 2c B d Fe 100‑a‑b‑c‑d After the magnet is diffused with Dy diffusion source, the remanent magnetism decreases by less than 0.15kGs, and the Hcj increases by more than 8kOe. After the magnet is diffused with Tb diffusion source, the remanent magnetism decreases by less than 0.15kGS, and the Hcj increases by more than 11kOe.

Description

Technical Field

[0001] The invention relates to the technical field of NdFeB rare earth magnets, and in particular to a NdFeB rare earth magnet capable of improving its own coercivity and a preparation method thereof. Background Art

[0002] NdFeB sintered permanent magnets are widely used in electronic information, medical equipment, new energy vehicles, household appliances, robots and other fields. In the past few decades of development, the research on NdFeB permanent magnets has developed rapidly. In particular, diffusion technology can significantly reduce the consumption of heavy rare earths and has a great cost advantage. In the manufacturing process of NdFeB sintered permanent magnets, heavy rare earth elements Dy and Tb are often added to the parent material. This method will cause a large amount of heavy rare earth elements Dy and Tb to enter the interior of the grains, reducing the remanence and magnetic energy product of the magnet, consuming a large amount of heavy rare earth elements and increasing the cost. Another method is grain boundary diffusion, which is a technology that uses heat treatment to allow the diffusion source to enter the interior of the magnet along the grain boundary to increase the coercive force of the magnet. This technology uses less heavy rare earth and can greatly improve the coercive force of the magnet. It has received widespread attention because of its low cost. However, with the current soaring prices of heavy rare earth Dy and Tb raw materials, the cost of pure Dy and Tb diffusion is still high. The diffusion technology of heavy rare earth alloys can effectively reduce the preparation cost of magnets while improving performance. Therefore, the development of diffusion technology of heavy rare earth alloys is particularly important for the mass production of NdFeB magnets.

[0003] The patent with publication number CN101641750B discloses a method for manufacturing a NdFeB system sintered magnet, which has the following steps: after applying a powder containing Rh to the NdFeB system sintered magnet, the NdFeB system sintered magnet is heated to diffuse the Rh in the powder into the NdFeB system sintered magnet through the grain boundary, wherein Rh is Dy and / or Tb, the powder contains 0.5-50% by weight of Al in a metallic state, and the amount of oxygen contained in the NdFeB sintered magnet is less than 0.4% by weight. This patent mainly prepares a diffusion source by mixing different powders, and then diffuses it into the magnet to increase the coercive force of the magnet. The diffusion source prepared by the above method, due to the different density of the powder, will have a certain degree of aggregation during the mixing process, which will cause uneven performance of the magnet after diffusion. Although there is heavy rare earth in the diffusion, the coercive force does not increase much after diffusion, and the purpose of cost saving cannot be achieved.

[0004] Publication No. CN106298219B discloses a method for preparing RTB rare earth permanent magnets, comprising the following steps: a) preparing R L u R H v Fe 100-u-v-w-z B w Mz Rare earth alloy, the R L represents at least one element of Pr and Nd, R H represents at least one element among Dy, Tb and Ho, M represents at least one element among Co, Nb, Cu, Al, Ga, Zr and Ti, the rare earth alloy contains a main phase structure of R-Fe-B tetragonal crystal, u, v, w and z are weight percentages of the respective substances, and u, v, w and z satisfy the following relationship: 0≤u≤10, 35≤v≤70, 0.5≤w≤5, 0≤z≤5; b) crushing R L u R H v Fe 100-u-v-w-z B w M z Rare earth alloy, forming alloy powder; c) the alloy powder and RTB magnet are loaded into a rotary diffusion device for thermal diffusion, the temperature range is 750-950℃, the time range is 4-72h; d) aging treatment, the rotary diffusion device is added with a dispersion or buffering material, the material is one or more of metal iron-based materials, titanium-based materials, or one or more of non-metallic aluminum oxide and zirconium oxide, the particle size of the material is less than 10mm, and the rotary diffusion device can also be added with anti-sticking powder, the anti-sticking powder is one or more of aluminum oxide, zirconium oxide, dysprosium oxide, terbium oxide, dysprosium fluoride, terbium fluoride, the particle size of the anti-sticking powder is less than 100um. The diffusion source alloy used in this invention is the diffusion source R L u R H v Fe 100-u-v-w-z B w M z Rare earth alloys. This technology has the following problems: ① When the B content in the diffusion source used is too high, its melting point will be relatively high and it is not easy to diffuse into the magnet. Ti, Zr, and Nb in M ​​are all high-melting-point elements and are not easy to diffuse into the magnet. ② According to the diffusion source formula, the Fe content in the diffusion is ≥10%. If the iron content is too high, too many ferromagnetic phases will be formed after diffusion, and the performance of the NdFeB magnet will be reduced. Although the Hcj of the magnet has increased, the Br decreases significantly, which is not conducive to improving the overall performance. Although the diffusion source contains heavy rare earths, the coercive force does not increase much after diffusion, and the remanence decreases significantly, which does not achieve ideal performance.

[0005] The patent with the publication number CN113593800A discloses a high-performance sintered NdFeB magnet and its preparation method, wherein RHxM1Bz, RH is selected from one or two elements of Dy and Tb, M1 is selected from one, two or three elements of Ti, Zr and Al, B is boron, x, y and z represent the weight percentage of the element, and x, y and z satisfy the following relationship: 75%≤x≤90%, 0.1%≤z≤0.5%, y=1-xz. On the one hand, the method improves the Hcj of the sintered NdFeB magnet by diffusion in a detachable material reaction barrel, solves the problem of improving the efficiency of the diffusion process, the problem of appearance adhesion, and slightly improves the coercive force, but the long-term use of the diffusion source will inevitably cause a certain degree of oxidation and nitridation, which will further reduce the utilization rate of heavy rare earth and increase the cost. On the other hand, when the diffusion source contains Ti or Zr, its melting point will be relatively high, resulting in a low diffusion rate. Under the same heavy rare earth content, the remanence decreases more, and the coercivity of the magnet is not further improved. The three-stage ramping heat treatment method is a conventional production process. Finally, the remanence decreases more after diffusion, and the coercivity of the magnet diffusion is not significantly improved.

[0006] Based on the above technical analysis, the heavy rare earth alloy diffusion source encounters the following two problems: on the one hand, the melting point of the diffusion source is too high, resulting in a low diffusion rate and limited improvement in coercive force; on the other hand, the heavy rare earth content is too high or the Fe content is too high during the diffusion process, and the remanence of the magnet decreases significantly, resulting in the inability to significantly improve the magnet performance. Summary of the invention

[0007] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a neodymium iron boron rare earth magnet and a preparation method thereof.

[0008] Technical solution: To achieve the above purpose, the present invention provides a NdFeB rare earth magnet, which comprises a main phase, a heavy rare earth shell, a grain boundary phase and a rare earth-rich phase, wherein the grain boundary phase comprises a μ phase or a δ phase, and the μ phase is R 36.5 Fe 63.5-x M x , 2.5≤x≤5; δ is R 32.5 Fe 67.5-y M y , 7≤y≤25, where R refers to at least two elements among Nd, Pr, Ce, and La, and M refers to at least two elements among Al, Cu, and Ga, and the ratio is in atomic percentage.

[0009] A method for preparing the NdFeB rare earth magnet comprises the following steps:

[0010] (S1) Diffusion source preparation: Melting alloy flakes, chemical formula R α RH δ Mβ B γ Fe 100-α-β-γ-δ , wherein 15≤α≤45, 20≤δ≤70, 10≤β≤25, 0.2≤γ≤5, R is at least one of Nd and Pr, RH is at least one of Dy and Tb, M is at least one of Al, Cu and Ga, and the Fe content is less than 5%; a layer of heavy rare earth-free alloy film is plated on the surface of the above alloy sheet, the chemical formula of which is R n M m , 50≤n≤80, 20≤m≤50, R is at least one of Nd, Pr, Ce, and La, M is at least one of Al, Cu, and Ga, and aging treatment is performed to form a new diffusion source and then hydrogen absorption and dehydrogenation treatment is performed, and the ratio is mass percentage;

[0011] (S2) The mass ratio chemical formula of NdFeB magnet matrix is ​​R a M 1 b M 2 c B d Fe 100-a-b-c-d , where 27≤a≤33, 0.5≤b≤3, 0.5≤c≤2.5, 0.8≤d≤1.2, R refers to one or more of Dy, Tb, Y, Ho, Gd, Nd, Pr, Ce, La, M 1 Refers to one or more of Al, Ga, Cu, M 2 It refers to various combinations of Ti, Co, Mg, Zn, Nb, Zr, Mo, Sn, and the remaining component is Fe. The NdFeB magnet matrix is ​​made into NdFeB thin sheets, and the proportion is mass percentage;

[0012] (S3) coating a novel diffusion source film layer on the NdFeB thin sheet, performing diffusion and aging treatment, and obtaining a NdFeB magnet.

[0013] Furthermore, the method of coating a layer of heavy rare earth-free alloy film on the surface of the alloy sheet in step (S1) and step (S3) is spray coating, dip coating or screen printing coating.

[0014] Furthermore, in step (S1), the aging treatment temperature is 600-800°C; the novel diffusion source is subjected to hydrogen absorption and dehydrogenation treatment, the hydrogen absorption temperature is 50-200°C, and the dehydrogenation temperature is 450-550°C.

[0015] Furthermore, the particle size of the novel diffusion source powder in step (S1) is 3-60 μm.

[0016] Furthermore, in step (S2), the prepared NdFeB magnet matrix material is melted and rapidly solidified into thin slices to obtain NdFeB thin slices.

[0017] Furthermore, in step (S2), the NdFeB matrix sheet and lubricant are mixed and hydrogen treated, and mixed powder is prepared by jet milling, and the powder is pressed into shape and sintered to obtain the NdFeB magnet matrix.

[0018] Furthermore, the particle size of the jet-milled powder of the NdFeB magnet matrix is ​​2-5 μm.

[0019] Furthermore, the sintering temperature of the sintering process for preparing the NdFeB magnet base material is 980-1060° C., and the sintering time is 6-15 hours.

[0020] Furthermore, in step (S3), the diffusion temperature is 850-950°C, the diffusion time is 6-30h, the primary aging temperature is 700-850°C, the primary aging time is 2-10h, the secondary aging temperature is 450-600°C, and the secondary aging time is 3-10h.

[0021] The NdFeB rare earth magnet and its preparation method of the present invention have at least the following technical effects:

[0022] (1) In alloy sheet R α RH δ M β B γ Fe 100-α-β-γ-δ The low melting point design increases the proportion of light rare earth elements, reduces the proportion of Fe content, increases the proportion of M, and coats the surface with a layer of low melting point R n M m The composite diffusion source formed by the alloy can effectively solve the problem of low diffusion rate due to a small amount of B content, thereby reducing diffusion performance; this method can well transport heavy rare earth into the magnet, form more heavy rare earth shells, effectively increase the coercive force of the magnet, and can well improve the diffusion rate, especially for NdFeB magnets with a thickness greater than 6mm.

[0023] (2) Alloy sheet R α RH δ M β B γ Fe 100-α-β-γ-δ The surface is coated with a layer of low melting point R n M m The powder made of the composite diffusion source formed by the alloy contains the B element, which can effectively reduce the oxidation problem in the diffusion process, thereby effectively utilizing the diffusion source and increasing the problem of low element utilization, such as the heavy rare earth is easy to combine with oxygen during the diffusion process, making it difficult for the heavy rare earth to diffuse into the magnet.

[0024] (3) Alloy sheet R α RH δ M β Bγ Fe 100-α-β-γ-δ The surface is coated with a layer of low melting point R n M m The powder made of the composite diffusion source formed by the alloy contains B and Fe elements, which diffuse into the magnet to form a new main phase, increase the remanence of the magnet, and offset the sharp decrease in remanence during a part of the diffusion process. The remanence decrease is less than 0.15Kgs. At the same time, the Fe element can form μ phase and δ phase with the Al, Ga, and Cu elements in the special magnet, further increasing the coercive force of the magnet. The increase in comprehensive performance is much greater than that of pure Dy, that is, the decrease in remanence Br is ≤0.15Kgs, and the increase in coercive force Hcj is ≥8kOe, and the typical increase can reach 9kOe.

[0025] (4) Alloy sheet R α RH δ M β B γ Fe 100-α-β-γ-δ The surface is coated with a layer of low melting point R n M m The powder made of the composite diffusion source formed by the alloy contains B element and Fe element, and the ratio of Fe element to B element can reach 10% at most, which can greatly reduce the price of the diffusion source, thereby reducing the production cost.

[0026] (5) The diffusion source can be prepared in large quantities. After being made into powder, it can achieve a utilization efficiency of nearly 100% by coating. It can provide a large number of diffusion sources for a large number of magnets and reduce the use of heavy rare earths. At the same time, the diffusion source can effectively increase the magnetic energy product of the magnet, thereby greatly reducing the production cost and improving the core competitiveness of the NdFeB magnet product production process.

[0027] (6) The prepared NdFeB magnet matrix is ​​only sintered to form a sintered state, without primary and secondary aging. After mechanical processing, diffusion and aging are performed, which greatly reduces the production cost and obtains excellent performance of the final product. Compared with the prior art, the present invention realizes the mutual coordination of the heavy rare earth alloy diffusion source and the magnet of the corresponding composition, solves the problem of greatly increasing the coercive force of the magnet and reducing the large decrease of Br in the light rare earth diffusion process. DETAILED DESCRIPTION

[0028] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0029] A method for preparing a neodymium iron boron rare earth magnet comprises the following steps:

[0030] (S1) Diffusion source preparation: The diffusion source alloy components are prepared according to Table 1. The chemical formula of the diffusion source alloy components is Rα RH δ M β B γ Fe 100-α-β-γ-δ , put it into a vacuum melting furnace for melting, cast it to form an alloy sheet, the average thickness of the alloy sheet is within the range of 0.25mm, the content of C and O elements in the alloy sheet is ≤200ppm, and the content of N is ≤50ppm; use a spray coating method to coat the surface of the above alloy sheet with a layer of heavy rare earth-free alloy film, and after coating, put the sheet into a drying wheel furnace for drying at ≤150℃, and the weight of the coating film is less than or equal to 3%; according to the proportion of the heavy rare earth-free film layer in Table 1, the aging treatment temperature is 600-800℃, and during the aging process The degreasing operation is carried out at 250-300°C. The cooling temperature of the new diffusion source during the aging cooling process is lower than 40°C. The cooling method is rapid cooling by circulating airflow, and the cooling gas atmosphere is an inert gas such as argon or helium. After the new diffusion source is formed, hydrogen absorption and dehydrogenation treatment are carried out. The powder particle size of the new diffusion source is 3-60μm, wherein the hydrogen absorption temperature is 50-200°C, and the dehydrogenation temperature is 450-550°C. It is worth noting that the alloy sheets are placed with gaps to prevent the local temperature from being too high during the hydrogen absorption process, causing the sheets to stick and be difficult to remove.

[0031] (S2) NdFeB base alloy is prepared according to Table 2, and its mass ratio chemical formula is R a M 1 b M 2 c B d Fe 100-a-b-c-d , put it into a vacuum melting furnace for smelting, cast it to form NdFeB matrix sheet, cool it to 50℃ and discharge it. The average thickness of the sheet is 0.25mm, the content of C and O elements is ≤200ppm, and the content of N is ≤50ppm. The NdFeB matrix sheet and lubricant are mixed and hydrogen treated, and then the mixed powder is prepared by air flow mill. The grinding gas is argon and the grinding particle size is 2-5μm. The NdFeB powder is placed in an automatic press, pressed into a blank under a magnetic field, and packaged into blocks. The block blank is placed in a sintering furnace for sintering. The sintering temperature is 980-1060℃, and the sintering time is 6-15h before machining.

[0032] (S3) A new type of diffusion source film layer is coated on the NdFeB thin sheet by a spray coating method, and diffusion and aging treatment are performed to obtain a NdFeB magnet. The specific process conditions and the properties of the obtained NdFeB magnet are shown in Table 3.

[0033] In order to verify the present scheme, eighteen comparative examples were designed. The difference between the comparative examples and the embodiments is that the diffusion source alloy composition of the comparative examples does not contain B and Fe elements, and its composition, content and process conditions are shown in Table 4; it is placed in a vacuum melting furnace for melting, cast to form a thin sheet, and discharged after cooling to 50°C. The average thickness of the thin sheet is 0.25 mm, the C and O contents are ≤200 ppm, and the N content is ≤50 ppm.

[0034] Based on the above data, by diffusing the diffusion source alloy R 2α M β B γ Fe 100-α-β-γ As for the rare earth magnets, after diffusion, the coercivity of all the embodiments containing Dy diffusion △Hcj>8kOe, containing Tb diffusion △Hcj>11kOe, containing DyTb diffusion △Hcj>9kOe increased significantly, the residual magnetism drop of the embodiment was significantly lower than that of the comparison example, and the coercivity of the embodiment was higher than that of the comparison example.

[0035] Therefore, the embodiments and comparative examples are specifically analyzed as follows:

[0036] Example 1 and Comparative Example 1: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 1 has Br=13.30kGs, Hcj=26.00kOe after diffusion, containing μ phase and δ phase, and Comparative Example 1 has Br=13.15kGs, Hcj=25kOe after diffusion, containing only δ phase. The Br (remanent magnetism) and Hcj (coercive force) advantages of the example are significantly higher than those of the comparative example.

[0037] Example 2 and Comparative Example 2: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 2 has Br=12.75kGs, Hcj=23kOe after diffusion, containing μ phase and δ phase, and Comparative Example 2 has Br=12.60kGs, Hcj=22.5kOe after diffusion, containing only δ phase. The Br (remanent magnetism) and Hcj (coercive force) advantages of the example are significantly higher than those of the comparative example.

[0038] Example 3 and Comparative Example 3: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 3 has Br=14.75kGs, Hcj=24.5kOe after diffusion, containing μ phase and δ phase, and Comparative Example 3 has Br=14.60kGs, Hcj=23kOe after diffusion. The Br (remanent magnetism) and Hcj (coercive force) of the embodiment are significantly superior to those of the comparative example.

[0039] Example 4 and Comparative Example 4: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 4 has Br=14.65kGs, Hcj=23kOe after diffusion, containing μ phase and δ phase, and Comparative Example 4 has Br=14.50kGs, Hcj=22kOe after diffusion. The Br (remanent magnetism) and Hcj (coercive force) of the embodiment are significantly superior to those of the comparative example.

[0040] Example 5 and Comparative Example 5: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 5 has Br=14.5kGs, Hcj=23.5kOe after diffusion, containing μ phase and δ phase, and Comparative Example 5 has Br=14.30kGs, Hcj=22kOe after diffusion. The Br (remanent magnetism) and Hcj (coercive force) of the embodiment are significantly superior to those of the comparative example.

[0041] Example 6 and Comparative Example 6: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 6 has Br=14.35kGs, Hcj=25kOe after diffusion, containing μ phase and δ phase, and Comparative Example 6 has Br=14.2kGs, Hcj=24.5kOe after diffusion. The Br (remanent magnetism) and Hcj (coercive force) of the embodiment are significantly superior to those of the comparative example.

[0042] Example 7 and Comparative Example 7: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 7 has Br=14.15kGs, Hcj=26kOe after diffusion, and contains μ phase and δ phase, and Comparative Example 7 has Br=13.9kGs, Hcj=24.5kOe after diffusion. The Br (remanent magnetism) and Hcj (coercive force) of the embodiment are significantly superior to those of the comparative example.

[0043] Example 8 and Comparative Example 8: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 8 has Br=13.9kGs, Hcj=28kOe after diffusion, and contains μ phase and δ phase, and Comparative Example 8 has Br=13.7kGs, Hcj=26.5kOe after diffusion. The Br (remanent magnetism) and Hcj (coercive force) of the embodiment are significantly superior to those of the comparative example.

[0044] Example 9 and Comparative Example 9: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 9 has Br=14.00kGs, Hcj=26.5kOe after diffusion, containing μ phase and δ phase, and Comparative Example 9 has Br=13.80kGs, Hcj=24.8kOe after diffusion. The Br (remanent magnetism) and Hcj (coercive force) of the embodiment are significantly superior to those of the comparative example.

[0045] Example 10 and Comparative Example 10: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 10 has Br=13.45kGs, Hcj=26.5kOe after diffusion, containing μ phase and δ phase, and Comparative Example 10 has Br=13.3kGs, Hcj=24.5kOe after diffusion, containing only δ phase. The Br (remanent magnetism) and Hcj (coercive force) advantages of the example are significantly higher than those of the comparative example.

[0046] Example 11 and Comparative Example 11: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 11 has Br=13.35kGs, Hcj=27kOe after diffusion, containing μ phase and δ phase, and Comparative Example 11 has Br=13.2kGs, Hcj=25kOe after diffusion, containing only δ phase. The Br (remanent magnetism) and Hcj (coercive force) of the embodiment are significantly superior to those of the comparative example.

[0047] Example 12 and Comparative Example 12: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 12 has Br=13.85kGs, Hcj=25.5kOe after diffusion, containing μ phase and δ phase, and Comparative Example 12 has Br=13.65kGs, Hcj=23.5kOe after diffusion. The Br (remanent magnetism) and Hcj (coercive force) of the embodiment are significantly superior to those of the comparative example.

[0048] Example 13 and Comparative Example 13: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 13 has Br=13.85kGs, Hcj=31kOe after diffusion, containing μ phase and δ phase, and Comparative Example 13 has Br=13.7kGs, Hcj=28.5kOe after diffusion. The Br (remanent magnetism) and Hcj (coercive force) of the embodiment are significantly superior to those of the comparative example.

[0049] Example 14 and Comparative Example 14: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 14 has Br=13.75kGs, Hcj=28kOe after diffusion, containing μ phase and δ phase, and Comparative Example 14 has Br=13.6kGs, Hcj=26.5kOe after diffusion. The Br (remanent magnetism) and Hcj (coercive force) of the embodiment are significantly superior to those of the comparative example.

[0050] Example 15 and Comparative Example 15: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 15 has Br=13.35kGs, Hcj=27kOe after diffusion, containing μ phase and δ phase, and Comparative Example 15 has Br=13.25kGs, Hcj=25kOe after diffusion. The Br (remanent magnetism) and Hcj (coercive force) of the example are significantly superior to those of the comparative example.

[0051] Example 16 and Comparative Example 16: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 16 has Br=13.4kGs, Hcj=29kOe after diffusion, containing μ phase and δ phase, and Comparative Example 16 has Br=13.25kGs, Hcj=27kOe after diffusion, containing only δ phase. The Br (remanent magnetism) and Hcj (coercive force) advantages of the example are significantly higher than those of the comparative example.

[0052] Example 17 and Comparative Example 17: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 17 has Br=12.6kGs, Hcj=29kOe after diffusion, containing μ phase and δ phase, and Comparative Example 17 has Br=12.5kGs, Hcj=27kOe after diffusion, containing only δ phase. The Br (remanent magnetism) and Hcj (coercive force) advantages of the example are significantly higher than those of the comparative example.

[0053] Example 18 and Comparative Example 18: Under the same NdFeB magnet and size, the same diffusion temperature and aging temperature and other conditions, compared with before diffusion, Example 18 has Br=13.6kGs, Hcj=28kOe after diffusion, containing μ phase and δ phase, and Comparative Example 18 has Br=13.45kGs, Hcj=26.5kOe after diffusion. The Br (remanent magnetism) and Hcj (coercive force) of the embodiment are significantly superior to those of the comparative example.

[0054] Table 1 Diffusion source components and contents in the examples

[0055] serial number Diffusion source slice ratio Alloy film ratio Example 1 Pr: 30%, Tb: 45%, Al: 10%, B: 4%, Fe: balance Pr: 82% Ga: 18% Example 2 Pr: 30%, Tb: 45%, Al: 15%, B: 3%, Fe: balance Pr: 70% Cu: 20% Ga: 10% Example 3 Nd: 20%, Tb: 45%, Al: 12%, Cu: 13%, B: 3%, Fe: balance Pr: 50% Cu: 30% Ga: 20% Example 4 Pr: 30%, Dy: 45%, Al: 10%, Ca: 5%, B: 5%, Fe: balance Nd: 60% Cu: 40% Example 5 Pr: 30%, Dy: 45%, Ga: 10%, Cu: 5%, B: 5%, Fe: balance Nd: 70% Cu: 20% Ga: 10% Example 6 Nd: 30%, Tb: 45%, Cu: 15%, B: 2%, Fe: balance Pr: 80% Al: 20% Example 7 Pr: 30%, Dy: 50%, Ga: 10%, B: 1%, Fe: balance Nd: 70% La: 5% Cu: 25% Example 8 Pr: 20%, Tb: 50%, Ga: 10%, Cu: 10%, B: 3%, Fe: balance Pr: 50% Ce: 5% Cu: 45% Example 9 Pr: 15%, Dy: 70%, Cu: 10%, B: 2%, Fe: balance Pr: 75% La: 6% Ga: 19% Example 10 Pr: 15%, Dy: 70%, A1: 10%, B: 0.5%, Fe: balance Pr: 60% Cu: 40% Embodiment 11 Pr: 15%, Dy: 70%, Al: 5%, Cu: 5%, B: 1%, Fe: balance Pr: 65% Ce: 5% Cu: 30% Example 12 Nd: 25%, Dy: 60%, Cu: 10%, B: 0.5%, Fe: balance Pr: 75% Ga: 25% Embodiment 13 Nd: 25%, Tb: 60%, Cu: 10%, B: 2%, Fe: balance Pr: 50% La: 5% Cu: 45% Embodiment 14 Nd: 45%, Tb: 30%, Cu: 10%, Al: 10%, B: 2%, Fe: balance Pr: 75% La: 6% Ga: 19% Embodiment 15 Nd: 30%, Dy: 50%, Cu: 10%, Ga: 3%, B: 4%, Fe: balance Nd: 70% Cu: 30% Example 16 Pr: 20%, Dy: 40%, Tb: 10%, Cu: 10%, Al: 5%, B: 5%, Fe: balance Nd: 65% Ce: 5% Cu: 30% Embodiment 17 Pr: 20%, Tb: 40%, Dy: 10%, Cu: 10%, Al: 5%, B: 4%, Fe: balance Nd: 50% Ga: 10% Cu: 40% Embodiment 18 Pr: 30%, Dy: 40%, Tb: 10%, Cu: 10%, B: 2%, Fe: balance Nd: 50% Ga: 25% Cu: 25%

[0056] Table 2 NdFeB magnet matrix material composition, content and magnet properties in each embodiment

[0057]

[0058] Table 3 Process conditions and finished magnet properties of various embodiments

[0059]

[0060] Table 4 Diffusion source components, contents and process conditions in each comparative example

[0061]

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A neodymium iron boron rare earth magnet, characterized in that: The NdFeB magnet comprises a main phase, a heavy rare earth shell, a grain boundary phase and a rare earth-rich phase, wherein the grain boundary phase comprises a μ phase or a δ phase, and the μ phase is R 36.5 Fe 63.5-x M x , 2.5≤x≤5; δ is R 32.5 Fe 67.5- y M y , 7≤y≤25, wherein R refers to at least two elements of Nd, Pr, Ce, and La, M refers to at least two elements of Al, Cu, and Ga, and the ratio refers to atomic percentage; The preparation process of the NdFeB rare earth magnet comprises the following steps: (S1) Diffusion source preparation: melting alloy flakes, the chemical formula of the alloy flakes is R α RH δ M β B γ Fe 100-α-β-γ-δ , wherein 15≤α≤45, 20≤δ≤70, 10≤β≤25, 0.2≤γ≤5, R is at least one of Nd and Pr, RH is at least one of Dy and Tb, M is at least one of Al, Cu and Ga, and the Fe content is less than 5%, wherein the ratio is mass percentage; a layer of heavy rare earth-free alloy film is plated on the surface of the above alloy sheet, the chemical formula of which is R n M m , 50≤n≤80, 20≤m≤50, R is at least one of Nd, Pr, Ce, and La, and M is at least one of Al, Cu, and Ga, and an aging treatment is performed to form a new diffusion source and then hydrogen absorption and dehydrogenation treatment is performed; (S2) NdFeB sheet production: Prepare NdFeB magnet matrix material, whose mass ratio chemical formula is R a M 1 b M 2 c B d Fe 100-a-b-c-d , where 27≤a≤33, 0.5≤b≤3, 0.5≤c≤2.5, 0.8≤d≤1.2, R refers to one or more of Dy, Tb, Y, Ho, Gd, Nd, Pr, Ce, La, M 1 Refers to one or more of Al, Ga, Cu, M 2 It refers to one or more of Ti, Co, Mg, Zn, Nb, Zr, Mo, Sn, and the remaining component is Fe. The NdFeB magnet matrix is ​​made into NdFeB thin sheets, and the proportion is mass percentage; (S3) coating a novel diffusion source film layer on the NdFeB thin sheet, performing diffusion and aging treatment, and obtaining a NdFeB magnet.

2. The NdFeB rare earth magnet according to claim 1, characterized in that: The coating method in step (S1) and step (S3) is any one of spray coating, dip coating or screen printing coating.

3. The NdFeB rare earth magnet according to claim 1, characterized in that: In step (S1), the aging treatment temperature is 600-800°C; the hydrogen absorption temperature of the new diffusion source is 50-200°C, and the dehydrogenation temperature is 450-550°C.

4. The NdFeB rare earth magnet according to claim 1, characterized in that: The particle size of the novel diffusion source powder in step (S1) is 3-60 μm.

5. The NdFeB rare earth magnet according to claim 1, characterized in that: In step (S2), the prepared NdFeB magnet matrix material is melted and rapidly solidified into thin slices to obtain NdFeB thin slices.

6. The NdFeB rare earth magnet according to claim 1, characterized in that: In step (S2), the NdFeB matrix sheet and lubricant are mixed and hydrogen treated, and mixed powder is prepared by jet milling. The powder is pressed into a shape and sintered to obtain the NdFeB magnet matrix.

7. The NdFeB rare earth magnet according to claim 6, characterized in that: The particle size of the jet-milled powder of the NdFeB magnet matrix is ​​2-5 μm.

8. The NdFeB rare earth magnet according to claim 6, characterized in that: The sintering temperature of the sintering process for preparing the NdFeB magnet base material is 980-1060° C., and the sintering time is 6-15 hours.

9. The NdFeB rare earth magnet according to claim 1, characterized in that: In step (S3), the diffusion temperature is 850-950°C, the diffusion time is 6-30h, the primary aging temperature is 700-850°C, the primary aging time is 2-10h, the secondary aging temperature is 450-600°C, and the secondary aging time is 3-10h.

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