Preparation method of high-performance rare earth permanent magnet material

Abstract

The application relates to a preparation method of high-performance rare earth permanent magnet materials and belongs to the technical field of magnetic materials. The application discloses a preparation method of high-performance rare earth permanent magnet materials, which comprises the following steps: S1, placing neodymium iron boron flake materials on a sample table of a conveying belt, and when the flake materials are conveyed to a laser polishing table by the conveying belt, irradiating the surface of the flake materials by using a laser light source with an energy density of 0.5-3.5 J / cm 2 2, and performing laser polishing; the translation speed of the conveying belt during irradiation of the laser light source is 0.7-1.5 cm / s; S2, conveying the flake materials after laser polishing to a diffusion workbench, coating diffusion source solutions obtained by mixing alloy powders and organic solvents on the double surfaces of the treated flake materials, and sequentially performing hot air drying; S3, transferring the flake materials to a diffusion furnace; S4, performing aging heat treatment on the flake materials; after aging is completed, immediately filling nitrogen or other inert gases into the furnace, and air cooling to 60-80 DEG C, so that the flake materials can be taken out of the furnace.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnetic materials, and relates to a preparation method of high-performance rare earth permanent magnet materials. BACKGROUND

[0002] Nd-Fe-B magnets are indispensable components in traditional industries such as air conditioner compressors, permanent magnet traction machines, magnetic suction discs, etc. due to their excellent comprehensive magnetic properties, and are also widely used in emerging industries such as new energy driven motors and wind power generation which are inseparable from carbon neutralization and carbon emission reduction. However, with the changes of market supply and demand and international situation, the price of rare earth raw materials is rising, and the cost of magnets becomes more sensitive to downstream customers. Therefore, how to realize efficient use of heavy rare earth is particularly important. As a method that can greatly reduce the dosage of heavy rare earth and production cost, the traditional grain boundary diffusion method has been widely used in mass production. As mentioned in the article "Magnetic properties and mechanical properties of high-Ce sintered Nd-Fe-B magnets treated by Dy diffusion" (Magnetic Materials and Devices, Vol. 52, No. 5, 2021), the process will inevitably produce waste liquid and cause environmental pollution, and a certain proportion of damage will occur during the transfer process, so a method that replaces the conventional pickling step to achieve the purpose of oil removal, rust removal and cleaning is needed. Chinese patent application file (publication number: CN108866547A) discloses a surface electric spark strengthening treatment method for Nd-Fe-B magnets based on laser cleaning, which uses laser cleaning process to treat the surface of sintered Nd-Fe-B magnets to remove oil stains and oxidation scale on the surface of the magnets; but the purpose of laser in this patent is single and has no relevance to the subsequent electric spark strengthening treatment. Chinese patent application file (publication number: CN103646776A) discloses a mechanical surface modification method for sintered Nd-Fe-B magnets based on plastic constraint, which uses a composite treatment method combining plastic constraint, low-energy laser impact treatment and laser surface heat treatment to treat the surface of sintered Nd-Fe-B magnets, which significantly improves the corrosion resistance of the magnets; but this method needs to set up an absorption layer and a constraint layer in advance, and it is time-consuming and energy-consuming. SUMMARY

[0003] The purpose of the present application is to solve the above-mentioned problems existing in the prior art, and a preparation method of high-performance rare earth permanent magnet materials is proposed, which pre-treats the magnets by an environmentally friendly laser polishing method.

[0004] The purpose of the present application can be achieved by the following technical solutions:

[0005] A preparation method of high-performance rare earth permanent magnet materials, the preparation method comprising the following steps:

[0006] S1, the neodymium iron boron sheet material is placed on the sample table of the conveying belt, when the sheet material is conveyed to the laser polishing table by the conveying belt, laser light source with energy density of 0.5-3.5 J / cm 2 is irradiated to the surface of the sheet material for laser polishing, and the translation speed of the conveying belt during laser light source irradiation is 0.7-1.5 cm / s;

[0007] S2, the sheet material after laser polishing is conveyed to the diffusion workbench, and the diffusion source solution mixed by alloy powder and organic solvent is coated on the double-sided surface of the treated sheet material, and then hot air drying is performed;

[0008] S3, the sheet material is transferred to the diffusion furnace, the diffusion temperature is 850-950 DEG C, and the diffusion time is 10-20 h;

[0009] S4, the sheet material is subjected to aging heat treatment, the heat treatment temperature is 400-600 DEG C, the aging time is 2-4 h; nitrogen or other inert gas is filled into the furnace immediately after aging, and air cooling is performed to 60-80 DEG C, and then the furnace is discharged.

[0010] The laser polishing is used instead of traditional pickling, which reduces the pollution to the environment and reduces the loss during product transportation; and the magnet after laser polishing has better comprehensive magnetic performance and deeper diffusion depth than the magnet treated by pickling through subsequent grain boundary diffusion process.

[0011] The laser polishing can remove the oxide layer on the surface of the magnet sheet and refine the grain on the surface of the magnet, widen the grain boundary as a diffusion channel, and finally improve the performance of the magnet after diffusion in combination with the subsequent diffusion process.

[0012] As preferred, the translation speed of the conveying belt during laser light source irradiation is 0.9-1.2 cm / s.

[0013] As preferred, the translation speed of the conveying belt during the process from the sample table to the laser polishing table and from the laser polishing table to the diffusion workbench is 0.7-1.5 cm / s.

[0014] The conveying belt always runs at a uniform speed, which can enable the laser to complete the polishing work and also be sufficient to complete the spraying of the diffusion source solution on the double-sided surface of the sheet material.

[0015] As preferred, the number of laser polishing is 1.

[0016] As preferred, the laser energy irradiation power is 300-500 W, the wavelength is 200-500 nm, the pulse width is 3-8 ns, and the spot diameter is 3-8 mm.

[0017] Currently, laser processing often requires high power or multiple impacts, while this invention can effectively clean the magnet surface with only one impact at lower power and improve the magnetic properties of the processed magnet.

[0018] Preferably, the neodymium iron boron sheet material on the sample stage in step S1 is N sheets with a thickness of 3-12 mm and a distance of 0-0.1 mm, wherein N≥2.

[0019] In this invention, multiple NdFeB thin film materials are arranged sequentially on a sample stage, transferred to a laser polishing stage by a conveyor belt, and then pass through a laser at a uniform speed to receive laser light source irradiation, saving energy and minimizing batch-to-batch variation; the small spacing between the thin films allows for continuous spraying in subsequent processes, reducing waste of diffusion source solution.

[0020] Preferably, the grade of the neodymium iron boron sheet material includes one or more of N52, N50, 52M, 50M, 52H, and 50H.

[0021] Preferably, the mass ratio of alloy powder to organic solvent in the diffusion source solution in step S2 is (2.8-3.2):1.

[0022] Preferably, the alloy powder is a rare earth hydride, a rare earth fluoride, or a RE. a TM 1-a One or more of them.

[0023] Further preferably, the rare earth hydride is one or more of dysprosium hydride, terbium hydride, holmium hydride, praseodymium-neodymium hydride, and gadolinium hydride, and the rare earth fluoride is one or more of TbF3 and DyF3.

[0024] Further preferably, the RE is one or more of Pr, Nd, Dy, Tb, Ho, and Gd, and the Tm is one or more of Al, Cu, Ga, Mn, and Co, wherein 35≤a≤70.

[0025] Furthermore, the RE a TM 1-a For Tb 35 Cu 52 Al 13 、Tb 65 Cu 20 Al 15 、Tb 50 Pr 15 Al 10 Ga 25 Dy 45 Pr 15 Al 15 Co 25 One or more of them.

[0026] Preferably, the organic solvent is one or more of aliphatic hydrocarbons, alicyclic hydrocarbons, alcohols, and ketones.

[0027] Preferably, the diffusion source solution is dysprosium hydride, terbium hydride, and ethanol in a mass ratio of (1.2-1.7):(1.2-1.7):1.

[0028] Further preferably, the mass ratio of dysprosium hydride to terbium hydride is 1:1.

[0029] Preferably, the coating includes one or more of the following: vacuum evaporation, spraying, magnetron sputtering, and electrophoresis.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. This invention uses laser polishing to remove the oxide layer on the surface of the neodymium iron boron sheet material, while refining the grains of the surface layer of the magnet and widening the grain boundaries that serve as diffusion channels.

[0032] 2. This invention replaces traditional acid washing with laser polishing, which reduces environmental pollution and product damage during transportation.

[0033] 3. This invention uses a conveyor belt to allow NdFeB sheet materials to pass through a laser light source at a uniform speed in sequence, resulting in uniform surface treatment of each NdFeB sheet and saving laser energy.

[0034] 4. In this invention, a diffusion source solution is sprayed onto both sides of the NdFeB thin film material, and the diffusion source is made to penetrate deeply into the NdFeB thin film material through aging treatment and heat treatment.

[0035] 5. This invention improves the overall magnetic properties of the magnet through laser polishing, surface coating with a diffusion source, diffusion heat treatment, and aging heat treatment, and also enhances the magnet's corrosion resistance. Detailed Implementation

[0036] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0037] The NdFeB sheet material before diffusion and the NdFeB finished product after diffusion were tested for performance, and the average performance test results are shown in Table 1.

[0038] Example 1

[0039] The N52 neodymium iron boron sheet material with product specifications of 14*14*5mm is prepared into 52H grade neodymium iron boron material through the following steps:

[0040] Ten NdFeB thin films with a spacing of 0.1 mm were placed on the sample stage of a conveyor belt. After the films were conveyed to the laser polishing stage at a speed of 1 cm / s, an energy density of 1.2 J / cm² was used. 2 The surface of the thin sheet material is irradiated with a laser source for laser polishing once, and the conveyor belt moves at a speed of 1 cm / s during laser irradiation. Then, the laser-polished thin sheet material is conveyed to a diffusion stage at a speed of 1 cm / s. A diffusion source solution of dysprosium hydride and ethanol mixed at a mass ratio of 3:1 is sprayed onto both sides of the treated thin sheet material, and then dried with hot air. The thin sheet material is then transferred to a diffusion furnace, where the diffusion temperature is 950℃ and the diffusion time is 20 hours. The thin sheet material is then subjected to aging heat treatment at a temperature of 500℃ for 4 hours. After aging, nitrogen is immediately introduced into the furnace, and the material is air-cooled to 70℃ before being removed from the furnace.

[0041] Example 2

[0042] The 50M NdFeB sheet material with product specifications of 32*15*3mm is prepared into 50UH grade NdFeB material through the following steps:

[0043] Ten NdFeB thin films with a spacing of 0.1 mm were placed on the sample stage of a conveyor belt. After the films were conveyed to the laser polishing stage at a speed of 1 cm / s, an energy density of 1.2 J / cm² was used. 2 The surface of the thin sheet material is irradiated with a laser source for laser polishing once, and the conveyor belt moves at a speed of 1 cm / s during laser irradiation. Then, the laser-polished thin sheet material is conveyed to the diffusion stage at a speed of 1 cm / s. A diffusion source solution of TbF3 and ethanol mixed at a mass ratio of 3:1 is sprayed onto both sides of the treated thin sheet material and dried with hot air in sequence. The thin sheet material is then transferred to a diffusion furnace, where the diffusion temperature is 950℃ and the diffusion time is 10 hours. The thin sheet material is then subjected to aging heat treatment at a temperature of 500℃ for 4 hours. After aging, nitrogen is immediately introduced into the furnace, and the material is air-cooled to 70℃ before being removed from the furnace.

[0044] Example 3

[0045] The 38H neodymium iron boron sheet material with product specifications of 32*15*3mm is prepared into 38UH grade neodymium iron boron material through the following steps:

[0046] Ten NdFeB thin films with a spacing of 0.1 mm were placed on the sample stage of a conveyor belt. After the films were conveyed to the laser polishing stage at a speed of 1.2 cm / s, an energy density of 1.2 J / cm² was used. 2A laser source irradiates the surface of a thin sheet material for laser polishing once, with the conveyor belt moving at a speed of 1.1 cm / s during irradiation. The laser-polished sheet material is then conveyed to a diffusion stage at a speed of 1 cm / s, using Tb at a mass ratio of 3:1. 65 Cu 20 Al 15 The diffusion source solution, after being mixed with ethanol, was sprayed onto both sides of the treated sheet material and dried with hot air. The sheet material was then transferred to a diffusion furnace at a diffusion temperature of 950℃ for 10 hours. The sheet material was then subjected to aging heat treatment at a temperature of 500℃ for 4 hours. After aging, nitrogen was immediately introduced into the furnace, and the material was cooled to 70℃ before being removed from the furnace.

[0047] Example 4

[0048] Compared with Example 1, the difference is that the diffusion source solution includes dysprosium hydride, terbium hydride and ethanol in a mass ratio of 1.5:1.5:1.

[0049] Example 5

[0050] Compared to Example 3, the difference lies in that the diffusion source solution includes Tb in a mass ratio of 3:1. 50 Pr 15 Al 10 Ga 25 Ethanol.

[0051] Example 6

[0052] Compared to Example 1, the difference lies in the energy density of the laser source, which is 3.7 J / cm². 2 .

[0053] Example 7

[0054] Compared to Example 1, the difference lies in the energy density of the laser source, which is 0.1 J / cm². 2 .

[0055] Example 8

[0056] Compared with Example 1, the difference is that the translational speed of the conveyor belt during laser irradiation is 1.3 cm / s.

[0057] Example 9

[0058] Compared with Example 1, the difference is that the translational speed of the conveyor belt during laser irradiation is 0.8 cm / s.

[0059] Example 10

[0060] Compared with Example 1, the difference is that the translational speed of the conveyor belt during laser irradiation is 1.6 cm / s.

[0061] Example 11

[0062] Compared with Example 1, the difference is that the translational speed of the conveyor belt during laser irradiation is 0.6 cm / s.

[0063] Comparative Example 1

[0064] Compared with Example 1, the difference is that the surface of the sheet material is treated with conventional pickling instead of a conveyor belt.

[0065] Comparative Example 2

[0066] Compared with Example 1, the difference is that the surface of the sheet material is sanded with sandpaper.

[0067] Table 1. Performance Test Table of Neodymium Iron Boron Materials

[0068]

[0069] According to the data in the table above, the NdFeB materials obtained in Examples 1-5 all exhibit good overall magnetic properties. In Example 6, the energy density of the laser source was too high, leading to a surge in surface defects and stress concentration in the magnet, affecting the subsequent diffusion effect. In Example 7, the energy density was too low, resulting in poor removal of the oxide layer on the magnet surface, which also affected the subsequent diffusion effect. In Example 8, the translation speed of the laser source was slightly too fast, and in Example 9, the translation speed was slightly too slow, both resulting in poor laser irradiation and thus minimal improvement in the material's magnetic properties. In Example 10, the translation speed of the laser source was too fast, and in Example 11, the translation speed was too slow, both resulting in poor laser irradiation and thus a decrease in the degree of improvement in the material's magnetic properties. In Comparative Example 1, conventional acid washing was used, generating waste liquid, polluting the environment, and having low processing efficiency, resulting in poor performance improvement of the obtained NdFeB materials. In Comparative Example 2, sandpaper polishing was time-consuming and laborious, and the magnetic properties were lower than those of the laser-polished product in this invention.

[0070] In summary, the present invention processes magnets in batches using lasers, which not only eliminates the need for acid washing but also increases the magnetic properties of the magnets covered by the diffusion source.

[0071] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for preparing a high-performance rare-earth permanent magnet material, characterized in that, The preparation method includes the following steps: S1. Place NdFeB sheet material on the sample stage of the conveyor belt. The NdFeB sheet material on the sample stage consists of N sheets with a thickness of 3-12 mm and a distance of 0-0.1 mm, where N ≥ 2. After the thin sheet material is conveyed to the laser polishing table by the conveyor belt, an energy density of 0.5-3.5 J / cm² is used. 2 Laser polishing is performed by irradiating the surface of a thin sheet material with a laser source. The translational speed of the conveyor belt during laser irradiation is 0.7-1.5 cm / s. The translational speed of the conveyor belt during the process from the sample stage to the laser polishing stage and from the laser polishing stage to the diffusion stage is 0.7-1.5 cm / s; S2. The laser-polished sheet material is transferred to the diffusion stage. A diffusion source solution, consisting of an alloy powder and an organic solvent at a mass ratio of (2.8-3.2):1, is applied to both sides of the treated sheet material and then dried with hot air. S3. Transfer the sheet material into a diffusion furnace at a diffusion temperature of 850-950℃ for 10-20 hours. S4. Perform aging heat treatment on the thin sheet material at a temperature of 400-600℃ for 2-4 hours. After aging, immediately fill the furnace with nitrogen or other inert gas and air cool it to 60-80℃ before removing it from the furnace.

2. The preparation method according to claim 1, characterized in that, The translational speed of the conveyor belt during laser irradiation is 0.9-1.2 cm / s.

3. The preparation method according to claim 1, characterized in that, In step S1, the laser energy irradiation power is 300-500W, the wavelength is 200-500nm, the pulse width is 3-8ns, and the spot diameter is 3-8mm.

4. The preparation method according to claim 1, characterized in that, In step S2, the organic solvent is one or more of aliphatic hydrocarbons, alicyclic hydrocarbons, alcohols, and ketones.

5. The preparation method according to claim 1, characterized in that, In step S2, the alloy powder is a rare earth hydride, a rare earth fluoride, or a RE. a TM 1-a One or more of them.

6. The preparation method according to claim 5, characterized in that, The rare earth hydride is one or more of dysprosium hydride, terbium hydride, holmium hydride, praseodymium-neodymium hydride, and gadolinium hydride, and the rare earth fluoride is one or more of TbF3 and DyF3.

7. The preparation method according to claim 5, characterized in that, The RE a TM 1-a RE is one or more of Pr, Nd, Dy, Tb, and Ho, and Tm is one or more of Al, Cu, Ga, Mn, and Co, where 35 ≤ a ≤ 70.

8. The preparation method according to claim 5, characterized in that, The RE a TM 1-a For Tb 35 Cu 52 Al 13 、Tb 65 Cu 20 Al 15 、Tb 50 Pr 15 Al 10 Ga 25 Dy 45 Pr 15 Al 15 Co 25 One or more of them.

9. The preparation method according to claim 1, characterized in that, In step S2, the diffusion source solution is dysprosium hydride, terbium hydride, and ethanol in a mass ratio of (1.2-1.7):(1.2-1.7):

1.

10. The preparation method according to claim 1, characterized in that, The coating includes one or more of the following: vacuum evaporation, spraying, magnetron sputtering, electrophoresis, and laser coating.

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