Method for improving performance of neodymium-iron-boron magnet, and high-coercivity neodymium-iron-boron magnet

Abstract

The present application discloses a method for improving performance of a neodymium-iron-boron magnet, and a high-coercivity neodymium-iron-boron magnet. The method for improving the performance of the neodymium-iron-boron magnet comprises: under the action of magnetic attachment, depositing ferromagnetic alloy diffusion source powder onto the surface of a neodymium-iron-boron magnet subjected to magnetism enhancement or magnetization, so as to obtain a magnet to be diffused; and carrying out diffusion heat treatment on the magnet to be diffused. The present application substantially avoids the adverse effect of impurities, which are introduced by conventional powder coating, deposition and diffusion modes, on the performance of the magnet, greatly improves the service stability of the magnet on the basis of high-quality utilization of rare earths, has a simple overall technological process, a stable diffusion effect and a wide application range, and is suitable for batch production of a high-performance magnet.

Description

A method for improving the performance of NdFeB magnets and high coercive force NdFeB magnets

[0001] This application claims priority to Chinese invention patent application number CN 202310729285.1, filed June 19, 2023, entitled “A method for improving the performance of NdFeB magnets and high coercive force NdFeB magnets”, which is incorporated herein by reference in its entirety. Technical Field

[0002] The present application belongs to the technical field of rare earth permanent magnet materials, and specifically relates to a method for improving the performance of NdFeB magnets and a high coercive force NdFeB magnet. Background Art

[0003] Grain boundary diffusion technology, an effective means of enhancing the coercivity of NdFeB magnets, has seen rapid development in recent years. Its principle involves depositing a modified diffusion source onto the magnet surface. Through a specific heat treatment process, the modified elements in the diffusion source diffuse along the grain boundaries and into the magnet interior. This effectively reduces surface defects or optimizes the magnet's microstructure, achieving magnetic hardening (enhancing the anisotropic field on the surface of the main phase grains) or optimizing the demagnetizing exchange coupling of the continuous grain boundary phase. Ultimately, the coercivity of the magnet is significantly improved without excessively damaging the magnet's remanent magnetization. Over the years, diffusion source materials have evolved from rare earth elements, oxides, or fluorides to today's low-melting-point rare earth alloys. Diffusion source deposition methods have also gradually diversified, including evaporation, magnetron sputtering, electrophoretic deposition, spraying, and screen printing. To accommodate the industrial application of low-melting-point rare earth alloy diffusion sources with excellent diffusion properties, powder preparation of the alloy diffusion source is now the mainstream method, followed by spraying or screen printing. The aforementioned powder coating deposition method typically requires mixing rare earth alloy powder with a solvent or colloid to form a powder slurry. This ensures sufficient bonding contact or strength between the diffusion source and the magnet substrate prior to the diffusion heat treatment, preventing the diffusion source from falling off during movement of the magnet after coating, which could severely damage the diffusion effect. However, the rare earth alloy powder can easily oxidize during mixing with the solvent, solvent volatilization, or degumming, preventing the diffusion source (modifying element) from achieving the desired diffusion effect. Furthermore, residual solvent or colloid (carbon and oxygen residues) can adversely affect the performance of the resulting diffusion magnet.

[0004] In view of this, a diffusion source attachment deposition method is designed to avoid the introduction of solvents or colloids while ensuring sufficient bonding strength between the diffusion source and the magnet substrate. This will be beneficial to improving the effect of grain boundary diffusion technology on enhancing the coercive force of magnets and effectively promote the application and development of rare earth low-melting-point alloy diffusion sources.

[0005] After searching, patent CN115846645A discloses a magnetic diffusion alloy powder for use in diffused NdFeB magnets and its application. This patented technical solution can avoid the impact of carbon residue on diffused magnets caused by conventional diffusion source slurry coating. However, this technical solution has poor diffusion effect on thicker magnets (low rare earth content, and small performance increase for magnets above 5mm), and the remanence of the magnets decreases significantly after diffusion (the decrease exceeds 1.0kGs), which far exceeds the remanence damage caused by carbon residue. In actual application, magnetic powder easily agglomerates on the magnet surface (powder clumps around the magnet), and the magnet performance fluctuates greatly, making it difficult to achieve efficient batch preparation of diffused magnets and industrial application difficulties. Therefore, a method of utilizing magnetic adsorption, deposition and diffusion is invented to optimize the composition of the diffusion source magnetic powder and the magnetization method of the magnet to avoid significant damage to the remanence of the magnet. At the same time, the diffusion source composition is matched with the surface magnetic distribution of the magnet, so that the magnetic diffusion source powder can easily and evenly adhere to the magnet surface and is suitable for batch production. This is of great significance to the development of current magnet grain boundary diffusion technology.

[0006] Summary of the Invention

[0007] The main purpose of this application is to provide a method for improving the performance of NdFeB magnets and a high coercive force NdFeB magnet to overcome the deficiencies in the prior art.

[0008] To achieve the aforementioned invention objectives, the technical solutions adopted in the embodiments of the present application include:

[0009] The present application provides a method for improving the performance of NdFeB magnets, comprising:

[0010] The ferromagnetic alloy diffusion source powder is deposited on the surface of the magnetized or magnetized NdFeB magnet under the action of magnetic attraction to obtain the magnet to be diffused;

[0011] performing a diffusion heat treatment on the magnet to be diffused;

[0012] The chemical formula of the ferromagnetic alloy diffusion source powder is R a M1 b M2 (100-a-b) , R includes one or more of Dy, Tb, Pr, Nd, Ho, La, Ce, Y, and Gd, M1 is a ferromagnetic metal element, and M2 includes one or more of Al, Cu, Ga, Zr, Ti, Nb, Zn, Mg, and Mn, wherein a and b are the atomic percentages of the diffusion source powder, 75≤a≤95, 5≤b≤25, and a+b≤100.

[0013] Furthermore, the surface magnetism of the NdFeB magnet that has been magnetized or magnetized is 5 to 500 Gs.

[0014] Furthermore, the method for improving the performance of NdFeB magnets specifically includes: when the NdFeB magnet is magnetized, the magnetic deflection angle between the normal line of the magnetization coil and the C-axis of the magnet is less than 5 degrees.

[0015] Furthermore, the method for improving the performance of NdFeB magnets specifically includes: burying the magnetized or magnetized NdFeB magnet in the ferromagnetic alloy diffusion source powder, and then taking it out to obtain the magnet to be diffused.

[0016] Furthermore, the particle size of the ferromagnetic alloy diffusion source powder is 1 to 100 μm.

[0017] Furthermore, the ferromagnetic metal elements include one or more of Fe, Co, and Ni.

[0018] Furthermore, the diffusion heat treatment specifically includes:

[0019] First, the magnet to be diffused is diffused under vacuum conditions at a temperature of 850-950° C. for 4-20 hours, and then rapidly cooled to room temperature;

[0020] Then, the magnet that has undergone the diffusion treatment is tempered under vacuum conditions at a tempering temperature of 450 to 650° C. for a tempering time of 1.5 to 6 hours, and then rapidly cooled to room temperature.

[0021] Furthermore, the method for improving the performance of NdFeB magnets specifically includes: placing the magnet to be diffused into a vacuum heat treatment furnace, and setting the vacuum degree in the vacuum heat treatment furnace to be better than 10 -3 Pa, then the magnet to be diffused is heated to the diffusion temperature and kept warm, then quickly cooled to room temperature, and then the magnet that has undergone the diffusion treatment is heated to the tempering temperature again in the furnace and kept warm, then quickly cooled to room temperature.

[0022] The present application also provides a high-coercivity NdFeB magnet, which is manufactured by the above method.

[0023] Compared with the prior art, this application has the following beneficial effects:

[0024] (1) The method of improving the performance of NdFeB magnets in this application fundamentally avoids the adverse effects of impurities introduced by conventional powder coating, deposition and diffusion on the performance of magnets. On the basis of achieving high-quality utilization of rare earths, the service stability of the magnets is greatly improved. The overall process flow is simple, the diffusion effect is stable, the applicability is wide, and the prepared products have good consistency and repeatability. It is suitable for mass production of high-performance magnets, especially for enterprise automated production.

[0025] (2) The ferromagnetic alloy diffusion source powder used in the method for improving the performance of NdFeB magnets in the present application controls the content of ferromagnetic metal elements between 5wt% and 25wt%. If the content of ferromagnetic metal elements is too high (the content is greater than 25wt%), the magnetism of the powder will be stronger, and it will be difficult to control the amount of ferromagnetic alloy diffusion source powder during the magnetic adsorption process. A large amount of powder will agglomerate and accumulate on the surface of the magnet, which will not only affect the subsequent diffusion process, but also directly affect the magnetic properties of the prepared magnet. At the same time, it has more rare earth elements and fewer ferromagnetic metal elements. Such a combination can not only better play its essential diffusion role, but also ensure the appropriate binding force between the matrix and the diffusion source during the magnetic adsorption process. More rare earth elements such as Dy, Tb, Pr, Nd, Ho, La, Ce, Y, Gd, and less Fe, Co , Ni element is the basis for preparing high-performance magnets; in addition, the ferromagnetic alloy diffusion source powder, whose particle size is between 1 and 100 μm, is more conducive to magnetic adsorption and deposition, and is convenient for subsequent diffusion treatment process; if the particle size is too large, the distance between the diffusion source powders will be larger after adsorption, and it is easy to agglomerate on the surface of the magnet, resulting in extremely uneven distribution, which is not conducive to subsequent diffusion; if the particle size is too small, the diffusion source powder has a larger specific surface area and surface energy, and is more easily oxidized, and the production, storage, adsorption and diffusion treatment processes will also increase the difficulty; in addition, only diffusion source powders of this composition and particle size, which have magnets with suitable surface magnetism after magnetization, can be subjected to the burying treatment of this application. Only in this way will the surface of the magnet have an appropriate amount of powder, which is not only convenient for cleaning and recycling of magnetic powder and saving the amount of magnetic powder, but also in line with the intensive utilization of rare earth elements.

[0026] (3) In the process of preparing high-performance NdFeB magnets with high coercivity, the ferromagnetic alloy diffusion source powder of the present application is directly adsorbed on both ends of the magnet by magnetic adsorption deposition diffusion, without the need to mix the diffusion source powder with a solvent or colloid, thereby simplifying the diffusion source attachment process and fundamentally avoiding the disadvantage of easy oxidation of rare earth elements during the mixing process of alloy powder and solvent, and also avoiding the adverse effects of carbon and oxygen residues on the final magnet performance.

[0027] (4) The magnetization or magnetization treatment of the present application can be carried out on a magnetizer. The larger the magnetization current, the higher the surface magnetism of the magnet, and the smaller the magnetization current, the lower the surface magnetism of the magnet. By precisely controlling the current of the magnetization coil, the surface magnetism of the upper and lower surfaces of the magnet is distributed between 5 and 500 Gs. The appropriate size of the surface magnetism is used in conjunction with diffusion source powders of different particle sizes and different compositions. For alloy powders of the same composition, the higher the surface magnetism, the more diffusion source powders adsorbed on the magnet surface, and agglomeration will occur accordingly. If the surface magnetism is too small, the magnetism of the magnet surface is too small, and the diffusion source powder cannot be adsorbed or is rarely adsorbed, which is insufficient to achieve the purpose of adsorption. Similarly, for diffusion source powders containing more ferromagnetic metal elements such as Fe, Co, and Ni, at appropriate particle sizes, the diffusion source powders adsorbed on the magnet surface will be adsorbed less. Under the condition of diameter, a smaller surface magnetism can be used, so that the amount of diffusion source powder adsorbed on the magnet surface will be more appropriate; for diffusion source powders containing less ferromagnetic metal elements such as Fe, Co, and Ni, the surface magnetism of the magnet can be increased accordingly, and an appropriate amount of diffusion source powder can also be adsorbed; therefore, the surface magnetism of the upper and lower surfaces of the magnet is distributed between 5 and 500Gs, which can relatively accurately control the amount of magnetic adsorption deposition of the diffusion source, avoid the waste of the diffusion source, and make the process easy to control; in addition, it is necessary to ensure that the magnetic deflection angle between the normal line of the magnetization coil and the C-axis of the magnet is less than 5 degrees during magnetization. If the magnetic deflection angle is too large, it will lead to uneven distribution of the surface magnetism of the magnet, further resulting in poor adsorption effect of the magnetic adsorption process, and ultimately causing large fluctuations in the performance of the magnet after diffusion.

[0028] (5) The shape of the NdFeB magnets used in this application is not limited to square, cylindrical and other magnets. After magnetization or magnetization, due to the corner effect of the magnetic flux lines, the surface magnetism at the corners of the magnet is higher, which will absorb relatively more diffusion source powder, which is beneficial to further enhance the anti-demagnetization ability of the corners of the magnet; and during the service process of the magnet, especially in the drive motor, due to the effects of eddy current, copper loss, etc., the corners of the magnet are more susceptible to demagnetization. The magnetic adsorption deposition diffusion method proposed in this application fully matches the principle of "focusing on strengthening" the weak areas of the corners of the magnet, can greatly improve the service stability of the magnet, accurately and efficiently utilize the diffusion source, and achieve the purpose of high-quality utilization of rare earths; and the surface magnetic strength of the magnet after magnetization can be accurately controlled by the current of the magnetization coil, so that the amount of magnetic adsorption deposition of the diffusion source can be relatively accurately controlled, avoiding the waste of the diffusion source, and the process is easy to control. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] FIG1 is a schematic diagram of a process for preparing a high-performance NdFeB magnet with high coercivity in one embodiment of the present application. DETAILED DESCRIPTION

[0031] To overcome the shortcomings of the existing technology, the inventors of this case, after extensive research and extensive practice, have proposed the technical solution of this application. This application primarily provides a method for improving the performance of NdFeB magnets and a high-coercivity NdFeB magnet. This method fundamentally avoids the adverse effects of impurities introduced by conventional powder coating, deposition, and diffusion methods on magnet performance. While achieving high-quality utilization of rare earth elements, it significantly improves the service stability of the magnet. The overall process is simple, the diffusion effect is stable, and the application scope is broad, making it suitable for mass production of high-performance magnets. The following further explains this technical solution, its implementation process, and its principles.

[0032] One aspect of an embodiment of the present application provides a method for improving the performance of a neodymium iron boron magnet, comprising:

[0033] The ferromagnetic alloy diffusion source powder is deposited on the surface of the magnetized or magnetized NdFeB magnet under the action of magnetic attraction to obtain the magnet to be diffused;

[0034] performing a diffusion heat treatment on the magnet to be diffused;

[0035] The chemical formula of the ferromagnetic alloy diffusion source powder is R a M1 b M2 (100-a-b) , R includes one or more of Dy, Tb, Pr, Nd, Ho, La, Ce, Y, and Gd, M1 is a ferromagnetic metal element, and M2 includes one or more of Al, Cu, Ga, Zr, Ti, Nb, Zn, Mg, and Mn, wherein a and b are the atomic percentages of the diffusion source powder, 75≤a≤95, 5≤b≤25, and a+b≤100.

[0036] The ferromagnetic alloy diffusion source powder in the embodiment of the present application controls the content of ferromagnetic metal elements between 5wt% and 25wt%. If the content of ferromagnetic metal elements is too high, the magnetism of the powder will be stronger, and it will be difficult to control the amount of ferromagnetic alloy diffusion source powder during the magnetic adsorption process. A large amount of powder will agglomerate and accumulate on the surface of the magnet, which not only affects the subsequent diffusion process, but also directly affects the magnetic properties of the prepared magnet. At the same time, it has more rare earth elements and fewer ferromagnetic metal elements. Such a combination can not only better exert its essential diffusion effect, but also ensure the appropriate binding force between the matrix and the diffusion source during the magnetic adsorption process. More rare earth elements such as Dy, Tb, Pr, Nd, Ho, La, Ce, Y, Gd, and less Fe, Co, and Ni elements are the basis for preparing high-performance magnets.

[0037] In some preferred embodiments, the surface magnetism of the magnetized or magnetized NdFeB magnet is 5 to 500 Gs.

[0038] In some preferred embodiments, the method for improving the performance of NdFeB magnets specifically includes: when the NdFeB magnet is magnetized, the magnetic deflection angle between the normal line of the magnetization coil and the C-axis of the magnet is less than 5 degrees.

[0039] In some preferred embodiments, the thickness of the NdFeB magnet is 2 to 10 mm.

[0040] In some preferred embodiments, the NdFeB magnet is square or cylindrical in shape.

[0041] In some preferred embodiments, the method for improving the performance of NdFeB magnets specifically includes: burying the magnetized or magnetized NdFeB magnet in the ferromagnetic alloy diffusion source powder, and then taking it out to obtain the magnet to be diffused.

[0042] In some preferred embodiments, the particle size of the ferromagnetic alloy diffusion source powder is 1 to 100 μm.

[0043] In some preferred embodiments, a more specific implementation method is that the ferromagnetic alloy diffusion source powder is ground into raw materials, weighed and proportioned according to the components, and then sequentially undergoes the steps of smelting, casting, hydrogen cracking, air flow milling, etc., and the final ferromagnetic alloy diffusion source powder has a particle size between 1 and 100 μm, which is more conducive to magnetic adsorption and deposition, and is convenient for subsequent diffusion treatment process; if the particle size is too large, the distance between the diffusion source powders will be larger after adsorption, and it is easy to agglomerate on the surface of the magnet, resulting in extremely uneven distribution, which is not conducive to subsequent diffusion; if the particle size is too small, the diffusion source powder has a larger specific surface area and surface energy, is more easily oxidized, and the production, storage, adsorption and diffusion treatment processes will also increase the difficulty.

[0044] In some preferred embodiments, the ferromagnetic metal elements may include one or more of Fe, Co, Ni, etc., but are not limited thereto.

[0045] Specifically, the magnetization or magnetization treatment of the embodiment of the present application can be carried out on a magnetizer. The greater the magnetization current, the higher the surface magnetism of the magnet, and the smaller the magnetization current, the lower the surface magnetism of the magnet. By precisely controlling the current of the magnetization coil, the surface magnetism of the upper and lower surfaces of the magnet is distributed between 5 and 500Gs. The appropriate size of the surface magnetism is used in conjunction with diffusion source powders of different particle sizes and different compositions. For alloy powders of the same composition, the higher the surface magnetism, the more diffusion source powders adsorbed on the magnet surface, and agglomeration will occur accordingly. If the surface magnetism is too small, the magnetism of the magnet surface is too small, and the diffusion source powder cannot be adsorbed or is rarely adsorbed, which is insufficient to achieve the purpose of adsorption. Similarly, for diffusion source powders containing more ferromagnetic metal elements such as Fe, Co, and Ni, in the alloy Under the condition of appropriate particle size, smaller surface magnetism can be used, so that the amount of diffusion source powder adsorbed on the magnet surface will be more appropriate; for diffusion source powder containing less ferromagnetic metal elements such as Fe, Co, and Ni, the surface magnetism of the magnet can be increased accordingly, and an appropriate amount of diffusion source powder will be adsorbed; therefore, by distributing the surface magnetism of the upper and lower surfaces of the magnet between 5 and 500 Gs, the amount of magnetic adsorption deposition of the diffusion source can be relatively accurately controlled, avoiding waste of the diffusion source and making the process easier to control; in addition, it is necessary to ensure that the magnetic deflection angle between the normal line of the magnetization coil and the C-axis of the magnet is less than 5 degrees during magnetization. If the magnetic deflection angle is too large, the surface magnetism of the magnet will be unevenly distributed, further resulting in poor adsorption effect during the magnetic adsorption process, and ultimately causing large fluctuations in the performance of the magnet after diffusion. In some cases, it is also possible to obtain a certain degree of surface magnetism by bringing the NdFeB magnet into contact with a strong magnet so that it has a certain degree of magnetism.

[0046] In some preferred embodiments, the diffusion heat treatment specifically includes:

[0047] First, the magnet to be diffused is diffused under vacuum conditions at a temperature of 850-950° C. for 4-20 hours, and then rapidly cooled to room temperature;

[0048] Then, the magnet that has undergone the diffusion treatment is tempered under vacuum conditions at a tempering temperature of 450 to 650° C. for a tempering time of 1.5 to 6 hours, and then rapidly cooled to room temperature.

[0049] It is particularly noted that rapid cooling to room temperature is adopted in the diffusion treatment and tempering treatment. The microstructure will undergo metallurgical evolution during the temperature drop process, and the high-temperature microstructure of around 900°C is conducive to high performance. In order to retain the high-temperature microstructure, a rapid cooling method is adopted, which is also a common method in this field and has no special requirements (defining the cooling rate range is not very meaningful, because the temperature difference between the sample and room temperature at different temperature stages determines the cooling rate). The faster the cooling rate, the better, but based on the heat conduction effect, air cooling is conventionally (customarily) used.

[0050] In some preferred embodiments, the method for improving the performance of NdFeB magnets specifically comprises: placing the magnet to be diffused into a vacuum heat treatment furnace, and setting the vacuum degree in the vacuum heat treatment furnace to be better than 10 -3 Pa, then the magnet to be diffused is heated to the diffusion temperature and kept warm, then quickly cooled to room temperature, and then the magnet that has undergone the diffusion treatment is heated to the tempering temperature again in the furnace and kept warm, then quickly cooled to room temperature.

[0051] Another aspect of the embodiments of the present application further provides a high-coercivity NdFeB magnet, which is produced by the aforementioned method. The coercivity of the high-coercivity NdFeB magnet increases by more than 5 kOe compared with the coercivity of the original NdFeB magnet.

[0052] The technical solution created by the present application is further explained and illustrated below in conjunction with specific embodiments and illustrative drawings, so that those skilled in the art can fully understand the invention of the present application. However, this explanation and illustration does not further limit the technical solution created by the present application. The improved technical solution of simple numerical replacement and conventional adjustment made on the basis of the invention falls within the scope of protection of the invention of the present application.

[0053] Example 1

[0054] The chemical formula is Pr 75 Fe5Al9Ga 11 The alloy with an atomic ratio of 1.57477 g / cm was ground into raw materials, weighed and proportioned, and then smelted, cast, hydrogen-decomposed, and jet-milled to obtain a ferromagnetic alloy diffusion source powder with an average powder particle size of 3.1 gm.

[0055] A 2mm thick N55 brand cylindrical magnet sample was selected and placed in a magnetizer. The magnetic deflection angle between the normal line of the magnetizing coil and the C axis of the magnet was controlled to be less than 2°, and a magnet sample with a surface magnetic distribution between 420 and 500 Gs on the upper and lower surfaces was obtained.

[0056] The magnetized magnet is buried in ferromagnetic alloy diffusion source powder under a protective atmosphere and then taken out to obtain a magnet to be diffused with the diffusion source powder deposited thereon by magnetic attraction.

[0057] The magnet to be diffused is placed in a vacuum heat treatment furnace and heated to a vacuum degree of 8×10 -4Under Pa conditions, the magnet is heated to 900°C in a furnace at a heating rate of 10°C / min and kept at this temperature for 10 hours, then quickly cooled to room temperature by air cooling to complete the diffusion treatment. Thereafter, the magnet is heated to 500°C in a furnace at a heating rate of 10°C / min and kept at this temperature for 2 hours, then air cooled to room temperature to complete the tempering treatment, and finally a high-performance magnet with high coercivity is obtained. The schematic diagram of the treatment process is shown in Figure 1. In order to verify the advantages of this application, the remanence (Br), coercivity (Hcj), and squareness (Hk / Hcj) performance tests of the magnets before and after diffusion are performed, and the results are shown in Table 1 below.

[0058] Table 1 Magnetic properties of N55 magnet before and after magnetic adsorption deposition and diffusion

[0059] From the above data, it can be seen that the magnetic adsorption deposition diffusion proposed in this application can greatly improve the coercive force of the magnet sample while meeting the consistency of the performance of batch-produced magnets (Note: 1-1 to 1-6 are multiple batches of products obtained using the same method in Example 1).

[0060] Example 2

[0061] The chemical formula is Pr 65 Tb 10 Fe 15 Co 10 The alloy with (atomic ratio) is ground into raw materials, weighed and proportioned, and then goes through the steps of melting, casting, hydrogen cracking, air flow milling, etc. to obtain ferromagnetic alloy diffusion source powder with an average powder particle size of 2.6μm.

[0062] A 52M brand cylindrical magnet sample with a thickness of 5.2 mm was selected and placed in a magnetizer. The magnetic deflection angle between the normal line of the magnetizing coil and the C axis of the magnet was controlled to be less than 3°, and a magnet sample with upper and lower surface magnetic fields between 5 and 85 Gs was obtained.

[0063] The magnetized or magnetized magnet is buried in the ferromagnetic alloy diffusion source powder under a protective atmosphere, and then taken out to obtain a magnet to be diffused with the diffusion source powder deposited thereon by magnetic attraction;

[0064] The magnet to be diffused is placed in a vacuum heat treatment furnace and heated to a vacuum degree of 9×10 -4 Under Pa conditions, the magnet is heated to 890°C in a furnace at a heating rate of 10°C / min and kept warm for 10 hours, then quickly cooled to room temperature by air cooling to complete the diffusion treatment. Thereafter, the magnet is heated to 500°C in a furnace at a heating rate of 8°C / min and kept warm for 2 hours, then air cooled to room temperature to complete the tempering treatment, thus obtaining a high-performance magnet with high coercivity.

[0065] In order to compare the effect of conventional powder coating deposition diffusion and the magnetic adsorption deposition diffusion proposed in this application, the same composition of Pr 65 Tb 10 Fe 15 Co 10 (Atomic ratio) diffusion source alloy powder was prepared into a slurry according to a conventional diffusion slurry preparation process (alloy powder was mixed with alcohol, colloidal solvent, etc., and the mixing ratio of powder to solvent was 1:1). It was sprayed on the surface of four 52M brand cylindrical magnet samples with a thickness of 5.2 mm. After the same diffusion heat treatment process as in Example 2, comparative magnets were obtained, which were recorded as C1-C4. In order to verify the advantages of the present application, the magnetic properties of the magnets before and after diffusion were tested, as shown in Table 2 below.

[0066] Table 2 Magnetic properties of 52M magnet before and after magnetic adsorption deposition and diffusion

[0067] From the above data, it can be seen that the magnetic adsorption deposition diffusion proposed in this application has a better diffusion effect than the conventional slurry coating diffusion, and while greatly improving the coercive force of the magnet sample, it meets the consistency of the performance of batch-produced magnets (Note: 2-1 to 2-6 are multiple batches of products obtained by the same method in Example 2).

[0068] Example 3

[0069] The chemical formula is Tb 55 Dy 30 Fe 10 Co 2.5 Cu 2.5 The alloy with (atomic ratio) is ground into raw materials, weighed and proportioned, and then goes through the steps of melting, casting, hydrogen cracking, air flow milling, etc. to obtain ferromagnetic alloy diffusion source powder with an average powder particle size of 10.5μm.

[0070] A 10mm thick N45 brand cylindrical magnet sample was selected and placed in a magnetizer. The magnetic deflection angle between the normal line of the magnetizing coil and the C axis of the magnet was controlled to be less than 4°, and a magnet sample with upper and lower surface magnetic fields between 250 and 330Gs was obtained.

[0071] The magnetized or magnetized magnet is buried in the ferromagnetic alloy diffusion source powder under a protective atmosphere and then taken out to obtain the magnet to be diffused with the diffusion source powder deposited thereon by magnetic attraction.

[0072] The magnet to be diffused is placed in a vacuum heat treatment furnace and heated to a vacuum degree of 9×10 -4Under Pa conditions, the magnet was heated to 900°C in a furnace at a heating rate of 10°C / min, held at that temperature for 10 hours, and then rapidly cooled to room temperature by air cooling to complete the diffusion treatment. The magnet was then heated to 500°C in a furnace at a heating rate of 10°C / min, held at that temperature for 2 hours, and then air-cooled to room temperature to complete the tempering treatment, thereby obtaining a high-performance magnet with high coercivity. To verify the advantages of this application, the magnetic properties of the magnets before and after diffusion were tested, as shown in Table 3 below.

[0073] Table 3 Magnetic properties of N45 magnet before and after magnetic adsorption, deposition and diffusion

[0074] From the above data, it can be seen that the magnetic adsorption deposition diffusion proposed in this application can greatly improve the coercive force of the magnet sample while meeting the consistency of the performance of batch-produced magnets (Note: 3-1 to 3-6 are multiple batches of products obtained using the same method in Example 3).

[0075] Comparative Example 1

[0076] The chemical formula is Pr 45 Fe 35 Al9Ga 11 The alloy with (atomic ratio) is ground into raw materials, weighed and proportioned, and then goes through the steps of melting, casting, hydrogen cracking, air flow milling, etc. to obtain ferromagnetic alloy diffusion source powder with an average powder particle size of 3.1μm.

[0077] A 2mm thick N55 brand cylindrical magnet sample was selected and placed in a magnetizer. The magnetic deflection angle between the normal line of the magnetizing coil and the C axis of the magnet was controlled to be less than 2°, and a magnet sample with a surface magnetic distribution between 420 and 500 Gs on the upper and lower surfaces was obtained.

[0078] The magnetized magnet is buried in ferromagnetic alloy diffusion source powder under a protective atmosphere and then taken out to obtain a magnet to be diffused with the diffusion source powder deposited thereon by magnetic attraction.

[0079] The magnet to be diffused is placed in a vacuum heat treatment furnace and heated to a vacuum degree of 8×10 -4 Under Pa conditions, the magnets were heated in a furnace at a rate of 10°C / min to 900°C, held at that temperature for 10 hours, and then rapidly cooled to room temperature using air cooling to complete the diffusion treatment. The magnets were then heated in a furnace at a rate of 10°C / min to 500°C, held at that temperature for 2 hours, and then air cooled to room temperature to complete the tempering treatment. The remanence (Br), coercivity (Hcj), and squareness (Hk / Hcj) performance tests of the magnets before and after diffusion were performed. The results are shown in Table 4 below.

[0080] Table 4 Magnetic properties of N55 magnet before and after magnetic adsorption, deposition and diffusion

[0081] From the above data, it can be seen that after the diffusion source powder in Example 1 is replaced with a diffusion source powder with a high Fe content, the performance of the diffusion magnet is far inferior to the diffusion magnet prepared with the diffusion source powder composition used in Example 1 (Note: 4-1 to 4-6 are multiple batches of products obtained using the same method in Control Example 1).

[0082] Comparative Example 2

[0083] The chemical formula is Pr 75 Fe5Al9Ga 11 The alloy with (atomic ratio) is ground into raw materials, weighed and proportioned, and then goes through the steps of melting, casting, hydrogen cracking, air flow milling, etc. to obtain ferromagnetic alloy diffusion source powder with an average powder particle size of 3.1μm.

[0084] A 2mm thick N55 brand cylindrical magnet sample was selected and placed in a magnetizer. The magnetic deflection angle between the normal line of the magnetizing coil and the C axis of the magnet was controlled to be 6°, and a magnet sample with a surface magnetic distribution between 420 and 500 Gs on the upper and lower surfaces was obtained.

[0085] The magnetized magnet is buried in ferromagnetic alloy diffusion source powder under a protective atmosphere and then taken out to obtain a magnet to be diffused with the diffusion source powder deposited thereon by magnetic attraction.

[0086] The magnet to be diffused is placed in a vacuum heat treatment furnace and heated to a vacuum degree of 8×10 -4 Under Pa conditions, the magnets were heated in a furnace at a rate of 10°C / min to 900°C, held at that temperature for 10 hours, and then rapidly cooled to room temperature using air cooling to complete the diffusion treatment. The magnets were then heated in a furnace at a rate of 10°C / min to 500°C, held at that temperature for 2 hours, and then air cooled to room temperature to complete the tempering treatment. The remanence (Br), coercivity (Hcj), and squareness (Hk / Hcj) performance tests of the magnets before and after diffusion were performed. The results are shown in Table 5 below.

[0087] Table 5 Magnetic properties of N55 magnet before and after magnetic adsorption deposition and diffusion

[0088] From the above data, it can be seen that after the magnetic deflection angle between the normal line of the magnetizing coil and the C-axis of the magnet in Example 1 is controlled to be greater than 5°, the performance of the diffusion magnet fluctuates greatly, and the performance consistency is far inferior to the diffusion magnet prepared with the diffusion source powder component used in Example 1 (Note: 5-1 to 5-6 are multiple batches of products obtained using the same method in Control Example 2).

[0089] Comparative Example 3

[0090] The chemical formula is Pr 75 Fe5Al9Ga 11The alloy with (atomic ratio) is ground into raw materials, weighed and proportioned, and then goes through the steps of melting, casting, hydrogen cracking, air flow milling, etc. to obtain ferromagnetic alloy diffusion source powder with an average powder particle size of 3.1μm.

[0091] A 2mm thick N55 brand cylindrical magnet sample was selected and placed in a magnetizer. The magnetic deflection angle between the normal line of the magnetizing coil and the C axis of the magnet was controlled to be less than 2°, and a magnet sample with a surface magnetic distribution between 500 and 580Gs on the upper and lower surfaces was obtained.

[0092] The magnetized magnet is buried in ferromagnetic alloy diffusion source powder under a protective atmosphere and then taken out to obtain a magnet to be diffused with the diffusion source powder deposited thereon by magnetic attraction.

[0093] The magnet to be diffused is placed in a vacuum heat treatment furnace and heated to a vacuum degree of 8×10 -4 Under Pa conditions, the magnet was heated to 900°C in a furnace at a heating rate of 10°C / min and kept warm for 10 hours, then quickly cooled to room temperature by air cooling to complete the diffusion treatment. Thereafter, the magnet was heated to 500°C in a furnace at a heating rate of 10°C / min and kept warm for 2 hours, then air cooled to room temperature to complete the tempering treatment. The remanence (Br), coercive force (Hcj), and squareness (Hk / Hcj) performance tests of the magnet before and after diffusion were performed. The results are shown in Table 6 below.

[0094] Table 6 Magnetic properties of N55 magnet before and after magnetic adsorption deposition and diffusion

[0095] From the above data, it can be seen that after the surface magnetic distribution of the magnet after magnetization in Example 1 is controlled to be greater than 500Gs, the remanence of the diffusion magnet decreases significantly and the coercive force fluctuation increases significantly. The main reason is that the alloy powder magnetically adsorbed on the surface of the magnet begins to agglomerate, and the adsorption amount becomes difficult to control, which is not as good as the diffusion magnet prepared with the diffusion source powder component in Example 1 (Note: 6-1 to 6-6 are multiple batches of products obtained by the same method in Control Example 3).

[0096] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0097] Although the present application has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions, and / or additions may be made without departing from the spirit and scope of the present application, and that substantial equivalents may be substituted for the elements of the described embodiments. In addition, many modifications may be made to adapt specific circumstances or materials to the teachings of the present application without departing from the scope of the present application. Therefore, it is not intended herein to limit the present application to the disclosed specific embodiments for carrying out the present application, but rather it is intended that the present application will include all embodiments within the scope of the appended claims. Furthermore, unless specifically stated, any use of the terms first, second, etc. does not indicate any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.

Claims

1. A method for improving the performance of NdFeB magnets, characterized in that: include: The ferromagnetic alloy diffusion source powder is deposited on the surface of the magnetized or magnetized NdFeB magnet under the action of magnetic adsorption to obtain the magnet to be diffused; Performing a diffusion heat treatment on the magnet to be diffused; The chemical formula of the ferromagnetic alloy diffusion source powder is R a M1 b M2 (100-a-b) , R includes one or more of Dy, Tb, Pr, Nd, Ho, La, Ce, Y, and Gd, M1 is a ferromagnetic metal element, and M2 includes one or more of Al, Cu, Ga, Zr, Ti, Nb, Zn, Mg, and Mn, wherein a and b are the atomic percentages of the diffusion source powder, 75≤a≤95, 5≤b≤25, and a+b≤100.

2. The method for improving the performance of NdFeB magnets according to claim 1, characterized in that: The surface magnetism of the NdFeB magnet after magnetization or magnetization treatment is 5 to 500 Gs.

3. The method for improving the performance of NdFeB magnets according to claim 2, characterized in that: Specifically include: When the NdFeB magnet is magnetized, the magnetic deflection angle between the normal line of the magnetization coil and the C axis of the magnet is less than 5 degrees.

4. The method for improving the performance of NdFeB magnets according to claim 1, characterized in that: The thickness of the NdFeB magnet is 2-10 mm; and / or the shape of the NdFeB magnet is square or cylindrical.

5. The method for improving the performance of NdFeB magnets according to claim 1, characterized in that: Specifically include: The magnetized or magnetized NdFeB magnet is buried in the ferromagnetic alloy diffusion source powder and then taken out to obtain the magnet to be diffused.

6. The method for improving the performance of NdFeB magnets according to claim 1 or 5, characterized in that: The particle size of the ferromagnetic alloy diffusion source powder is 1 to 100 μm.

7. The method for improving the performance of NdFeB magnets according to claim 1, characterized in that: The ferromagnetic metal elements include one or more of Fe, Co and Ni.

8. The method for improving the performance of NdFeB magnets according to claim 1, characterized in that: The diffusion heat treatment specifically includes: First, the magnet to be diffused is diffused under vacuum conditions at a diffusion temperature of 850 to 950° C. for a diffusion time of 4 to 20 hours, and then rapidly cooled to room temperature; Then, the magnet that has undergone the diffusion treatment is tempered under vacuum conditions, the tempering temperature is 450-650° C., the tempering time is 1.5-6 hours, and then it is quickly cooled to room temperature.

9. The method for improving the performance of NdFeB magnets according to claim 8, characterized in that: Specifically include: The magnet to be diffused is placed in a vacuum heat treatment furnace, and the vacuum degree in the vacuum heat treatment furnace is set to be better than 10 -3 Pa, then the magnet to be diffused is heated to the diffusion temperature and kept warm, and then quickly cooled to room temperature, and then the magnet that has undergone the diffusion treatment is heated to the tempering temperature again in the furnace and kept warm, and then quickly cooled to room temperature.

10. A high coercive force neodymium iron boron magnet, characterized in that: The high coercive force NdFeB magnet is obtained by the method described in any one of claims 1-9.

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