Grain boundary diffusion source without heavy rare earth and method for preparing high-coercivity magnet by grain boundary diffusion source

Abstract

The invention relates to the technical field of rare earth permanent magnet materials, in particular to a grain boundary diffusion source without heavy rare earth and a method for preparing a high-coercivity magnet by the grain boundary diffusion source, the grain boundary diffusion source is SmCo magnetic powder, and the grain size of the grain boundary diffusion source is 1-5 microns. The alloy further comprises a mixed alloy of Al powder and Cu powder. The method for preparing the high-coercivity magnet comprises the following steps: (1) processing a neodymium-iron-boron magnet to be diffused into a magnet of which one surface is less than 5mm in thickness; 2) carrying out surface oil removal, acid pickling and surface activation on the processed magnet sheet, drying in a drying oven, and drying for later use to obtain a pretreated magnetic sheet for later use; (3) mixing and stirring a grain boundary diffusion source and a diffusant to form turbid liquid; 4) uniformly coating the turbid liquid on the surface of a magnet to be diffused through a spraying, brushing or screen printing process, and curing the alloy powder of a diffusion source on the surface of the magnet through baking of a baking oven or a baking tunnel; and (5) the magnet with the solidified diffusion source alloy powder is placed in a vacuum sintering furnace to be subjected to diffusion treatment.

Description

Technical Field

[0001] This invention relates to the field of rare earth permanent magnet materials technology, specifically to a grain boundary diffusion source without heavy rare earth and a method for preparing a high coercivity magnet. Background Technology

[0002] Since its discovery by American and Japanese scientists in the 1980s, neodymium iron boron rare earth permanent magnets have been widely used in various fields such as motors, electronic devices, aerospace, medical equipment, microwave communication technology, controllers, instruments, new energy, and humanoid robots due to their advantages such as high magnetic energy product and high remanence.

[0003] In recent years, the new energy vehicle industry has developed rapidly. New energy electric vehicles are typically driven by electricity and generally use permanent magnet motors. From the perspective of magnetic materials, in order to further improve energy efficiency, the demand for rare-earth permanent magnets with superior magnetic properties is constantly increasing. Furthermore, smartphone technology is also constantly evolving; lighter and thinner designs have become the trend in mobile phone development. The electronic components used are becoming smaller and smaller, and the requirements for the performance of magnets in these electronic components are becoming increasingly stringent.

[0004] To manufacture rare-earth permanent magnets with high coercivity, the traditional method is to replace light rare-earth elements such as praseodymium (Pr) or neodymium (Nd) in the magnet alloy with heavy rare-earth elements such as dysprosium (Dy) or terbium (Tb). However, these heavy rare-earth elements are 4 to 10 times more expensive than light rare-earth elements, and their global reserves are also limited, resulting in resource constraints. Therefore, to expand the application areas of rare-earth magnets and solve the supply problem, it is necessary to invent a manufacturing technology for rare-earth permanent magnets that can minimize the content of heavy rare-earth elements and improve coercivity.

[0005] Based on this, research institutions and rare earth magnet manufacturers worldwide have been striving since 2000 to reduce the use of heavy rare earth elements and improve magnetic retention. To date, representative methods developed include grain refinement techniques for rare earth sintered magnets, developed by companies such as Hitachi Metals in Japan. This technology uses high-speed pulverizing equipment to create fine powders during the manufacture of magnet alloys and powders. The grain size of the final sintered body can be controlled to 1-2 μm compared to traditional methods. However, its drawbacks include the high sensitivity of the fine powders to oxygen, making oxidation difficult and challenging to control in an oxygen-free atmosphere during production. Furthermore, the sintering behavior of the fine powders is uneven, with some forming coarse grains, leading to various intractable problems. Many domestic companies are also researching grain refinement technology, but due to the high equipment requirements and difficulty in controlling the production process, it has not yet been applied to large-scale production.

[0006] With the increasing demand for high-performance NdFeB magnets, grain boundary diffusion treatment technology has gained significant attention and interest from researchers. This technology involves attaching heavy rare earth elements (dysprosium, terbium, or alloys containing dysprosium and terbium) to the surface of an NdFeB magnet and then diffusing them into the magnet's interior through a high-temperature treatment process. Compared to traditional techniques, this method can significantly increase the magnet's coercivity with a smaller amount of heavy rare earth elements while maintaining almost no change in remanence.

[0007] Another technique is the heavy rare earth grain boundary diffusion technology. Traditional sintered NdFeB magnets with low or no heavy rare earth elements are cut into sheets less than 8 mm thick. Compounds containing heavy rare earth elements (dysprosium, terbium) are then applied to the surface of these sheets via spraying, brushing, magnetron sputtering, screen printing, or electroplating. The sheets are then heat-treated at temperatures above 800°C in argon or a vacuum, allowing the heavy rare earth element (dysprosium, terbium) compounds attached to the sheet surface to gradually diffuse along the grain boundaries and penetrate into the magnet's interior. Once the heavy rare earth elements have diffused along the grain boundaries and completely penetrated the magnet, they become concentrated around the grain boundaries. Due to the inherent characteristics of sintered NdFeB magnets, almost all magnetic defects causing a decrease in magnetostrictive remanent magnetization are located at the grain boundaries. Therefore, by removing these magnetic defects when heavy rare earth elements are concentrated at the grain boundaries, coercivity can be improved. Therefore, the grain boundary diffusion technology of heavy rare earth elements, by selectively distributing heavy rare earth elements at the grain interface, can minimize the reduction in magnetic properties and maximize the increase in coercivity, and is considered the most reasonable way to reduce the amount of heavy rare earth elements used.

[0008] Diffusion technology using heavy rare earth elements (including dysprosium and terbium) has been widely applied in recent years; however, the high price of heavy rare earth elements results in a still high cost. For example, US11527356B2 uses application materials containing one or more heavy rare earth hydrides (Dy-H and Tb-H compounds) to uniformly diffuse the heavy rare earth elements into the magnet. JP2019220689A mainly uses heavy rare earth hydrides as diffusion materials to produce uniform and stable high-quality magnets, while minimizing the use of heavy rare earth elements and improving magnetic retention. CN108140482A uses HRE compound powder containing Gd, Tb, Dy, and Ho heavy rare earth elements through a specific process to achieve grain boundary diffusion, thereby improving coercivity. Summary of the Invention

[0009] The purpose of this invention is to provide a grain boundary diffusion source without heavy rare earth elements and a method for preparing a high coercivity magnet.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A grain boundary diffusion source without heavy rare earth elements is SmCo magnetic powder with a particle size of 1-5 μm.

[0012] Furthermore, it also includes mixed alloys of Al powder and Cu powder.

[0013] A diffusion solution prepared from a grain boundary diffusion source free of heavy rare earth elements comprises the aforementioned grain boundary diffusion source free of heavy rare earth elements and a diluent, wherein the diluent includes a diluent and a curing agent. During preparation, the slurry after mixing the two is placed in an ultrasonic cleaner and kept for at least 10 minutes to ensure uniform stirring.

[0014] Furthermore, the diluent is one or more of isopropanol, anhydrous alcohol, liquid paraffin, petroleum ether, and butanol.

[0015] Furthermore, the curing agent includes epoxy resin and / or polypropylene resin.

[0016] Furthermore, the volume percentage of the diluent and the curing agent is 9:1.

[0017] The present invention also provides a method for preparing a high coercivity magnet, comprising the following steps:

[0018] (1) The neodymium iron boron magnet to be diffused is processed into a magnet with a thickness of <5mm on one side, and its shape is arbitrary;

[0019] (2) Remove oil and pickle the surface of the processed magnet sheet, activate the surface, place it in an oven to dry, and then dry it for later use to obtain a pre-treated magnet sheet for later use.

[0020] (3) Mix the grain boundary diffusion source without heavy rare earth with the diffusion agent and then disperse and stir it with ultrasound to form a suspension;

[0021] (4) The uniformly mixed suspension is uniformly coated onto the surface of the magnet to be diffused by spraying, brushing or screen printing diffusion process, and then baked in an oven or drying tunnel at a temperature of 100-150℃, so that the alloy powder of the diffusion source is solidified on the surface of the magnet.

[0022] (5) Place the magnet with the solidified diffusion source alloy powder in a graphite box or a metal molybdenum box and place it in a vacuum sintering furnace for diffusion treatment.

[0023] In step (3), the mass percentage of SmCo magnetic powder in the suspension is ≥90%.

[0024] In step (4), the magnet coated with diffusion source alloy powder is placed in a heating furnace and gradually heated to a temperature range of 300℃ to 450℃. It is then kept at this temperature for 1.5 to 4 hours for preheating treatment, and then heated to 800-1000℃ to allow the alloy powder to diffuse into the interior of the magnetic sheet.

[0025] Furthermore, step (4) includes:

[0026] First-stage heat treatment: Vacuum is applied, and the temperature is raised to 300-450℃ for preheating for 1.5-3 hours. Then, the temperature is raised to 850-950℃ and held for 5-20 hours for homogenization. The vacuum level during the heating process is below 10. -3 Pa, after the heat preservation is completed, argon gas is used for cooling;

[0027] Secondary heat treatment: The magnetic sheet after primary heat treatment is subjected to secondary heat treatment at a temperature of 500-650℃ for 2.5-5 hours. After the heat treatment is completed, argon gas is used for cooling, and the refrigeration system is turned on for rapid cooling to obtain a high-performance magnet with high coercivity.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] This invention provides a grain boundary diffusion source free of heavy rare earth elements. Using this source to diffuse neodymium iron boron magnets yields high-performance, high-coercivity magnets. Compared to existing diffusion sources containing heavy rare earth elements, this invention significantly reduces product costs while maintaining essentially the same performance, demonstrating promising prospects for industrialization. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] (1) According to the proportion of the raw materials (mass percentage) PrNd(29.8)Fe68.63B0.92Cu0.15Al0.1Ti0.2Ga0.2, the proportioned raw materials were passed through a continuous vacuum melting furnace using a rapid solidification process to obtain a strip with an average thickness of 0.25mm. The melting temperature was 1450℃ and the refining time was 6min. The obtained strip was sorted by a thickness sorter to remove qualified strips, and then loaded into a hydrogen crushing furnace for hydrogen crushing. It was then kept at 550℃ for 6.5h for dehydrogenation treatment to obtain coarse crushed powder. The coarse crushed powder was then ground in a gas flow mill under nitrogen atmosphere protection to obtain fine powder with an average particle size of 3.0μm.

[0033] (2) Add lubricant (0.03% isopropanol) to the air jet mill magnetic powder and stir. Then, it is oriented and formed under nitrogen atmosphere protection with an orientation magnetic field >1.7T. Then, it isostatically pressed and the vacuum film is removed in the oil stripping box under nitrogen protection. During the operation, ensure that the oxygen content is less than 100ppm. Place the pressed magnetic block into a graphite box and wait for sintering.

[0034] (3) The blanks placed in the graphite box are put into a vacuum sintering furnace for sintering. The blanks are sintered at 1060℃ for 6 hours, cooled to less than 50℃ by argon gas, and then heated to 900℃ for first-stage tempering for 2.5 hours. The blanks are cooled to less than 50℃ by argon gas, and then heated to 490℃ for second-stage tempering for 5 hours to prepare sintered NdFeB magnets.

[0035] (4) The prepared sintered NdFeB magnets were processed into magnetic sheets with dimensions of 20mm×20mm×2mm and marked as T. The surface of the sheets was degreased and activated, and then each sheet was weighed at 10Kg and used as a diffusion substrate for diffusion.

[0036] (5) Preparation of diffusion source solvent: Weigh 90g of crushed SmCo powder, weigh 135g of alcohol and 7g of epoxy resin, wherein the epoxy resin is 5.2% of the weight of alcohol and the weight ratio of alcohol to alloy powder is 1.5:1. First, add epoxy resin to alcohol and stir evenly with ultrasonic waves. Then add the weighed alloy powder to the evenly mixed solution and continue to disperse it evenly into a uniform diffusion source with ultrasonic waves.

[0037] (6) Place the diffusion substrate and cover the substrate surface by screen printing. Weigh the magnetic sheet after coating to ensure that the weight of the coating layer is 1% of the total weight of the magnetic sheet after coating.

[0038] (7) Place the coated magnetic sheet into a molybdenum box, and then place it in a sintering furnace for diffusion treatment. Preheat the furnace to 300℃-450℃ for 2 hours. Then, raise the temperature to 850℃-950℃ and hold for 20 hours for homogenization heat treatment. The vacuum degree during the heating process should be below 10. -3 Pa. After the heat treatment is completed, argon gas is purged for cooling. Then, a secondary heat treatment is performed, with the temperature set at 500-650℃ and the heat treatment time at 5 hours. After the heat treatment is completed, argon gas is purged for cooling, and the refrigeration system is turned on for rapid cooling, resulting in a high-performance, high-coercivity magnet.

[0039] The magnetic sheet is removed and labeled T1. The properties of the well-impregnated material T1 and the substrate T0 are measured using a magnetic performance measuring instrument.

[0040] The performance comparison between T0 and T1 is shown in the table below.

[0041] magnetic sheet Br(KGS) Hcj(KOe) (BH)max(MGOe) HK / Hcj T0 14.35 17.3 50.34 95.6 T1 14.21 20.15 50.22 95.2

[0042] Example 2

[0043] (1) According to the proportion of the components (mass percentage) PrNd(31.8)Fe65.98B0.92Cu0.4Al0.3Ti0.2Ga0.4, the proportioned raw materials were passed through a continuous vacuum melting furnace using a rapid solidification process to obtain a strip with an average thickness of 0.25mm. The melting temperature was 1450℃ and the refining time was 6min. The obtained strip was sorted by a thickness sorter to remove qualified strips, and then loaded into a hydrogen crushing furnace for hydrogen crushing. It was then kept at 550℃ for 6.5h for dehydrogenation treatment to obtain coarse crushed powder. The coarse crushed powder was then ground in an air jet mill under nitrogen atmosphere protection to obtain fine powder with an average particle size of 3.0μm.

[0044] (3) Add lubricant (0.03% isopropanol) to the air jet mill magnetic powder and stir. Then, it is oriented and formed under nitrogen atmosphere protection. The orientation magnetic field is >1.7T. Then, it isostatically pressed and the vacuum film is removed in the oil stripping box under nitrogen protection. During the operation, ensure that the oxygen content is less than 100ppm. Place the pressed magnetic block into the graphite box and wait for sintering.

[0045] (3) The blanks placed in the graphite box are put into a vacuum sintering furnace for sintering. The blanks are sintered at 1060℃ for 6 hours, cooled to less than 50℃ by argon gas, and then heated to 900℃ for first-stage tempering for 2.5 hours. The blanks are cooled to less than 50℃ by argon gas, and then heated to 490℃ for second-stage tempering for 5 hours to prepare sintered NdFeB magnets.

[0046] (4) The prepared sintered NdFeB magnets were processed into magnetic sheets with dimensions of 20mm×20mm×2mm and marked as A. The surface of the sheets was degreased and activated, and then weighed separately. These sheets were used as diffusion substrates for diffusion.

[0047] (5) Preparation of diffusion source solvent: Weigh 90g of crushed SmCo powder, weigh 135g of alcohol, and weigh 7g of epoxy resin, wherein the epoxy resin is 5.2% of the weight of alcohol and the weight ratio of alcohol to alloy powder is 1.5:1. First, add epoxy resin to alcohol and stir evenly with ultrasonic waves. Then, add the weighed alloy powder to the evenly mixed solution and continue to disperse it evenly into a uniform diffusion source with ultrasonic waves.

[0048] 6) Place the diffusion substrate in place and cover the substrate surface with screen printing spraying. Weigh the coated magnetic sheet to ensure that the weight of the coating layer is 1% of the total weight of the coated magnetic sheet.

[0049] 7) Place the coated magnetic sheet into a molybdenum box, then place it in a sintering furnace for diffusion treatment. Preheat the furnace to 300℃-450℃ for 2 hours. Then, raise the temperature to 850℃-950℃ and hold for 20 hours for homogenization heat treatment. The vacuum level during the heating process should be below 10°C. -3 Pa. Then, a secondary heat treatment is performed, with the temperature set at 500-650℃ and the holding time at 5 hours. After the holding time is completed, argon gas is purged for cooling, and the refrigeration system is turned on for rapid cooling to obtain a high-performance, high-coercivity magnet.

[0050] After the heat preservation is completed, argon gas is used for cooling. The magnetic sheet is removed and labeled A1. The properties of the well-impregnated material A1 and the substrate A0 are measured using a magnetic property measuring instrument.

[0051] The performance comparison between A0 and A1 is shown in the table below.

[0052] magnetic sheet Br(KGS) Hcj(KOe) (BH)max(MGOe) HK / Hcj A0 13.12 22.1 42.15 95.6 A1 12.96 25.32 41.53 95.1

[0053] Example 3

[0054] (1) According to the proportion of PrNd(29.3)Fe69.23B0.92Cu0.2Ti0.15Ga0.2, the proportioned raw materials were processed by a rapid solidification process through a continuous vacuum melting furnace to obtain a strip with an average thickness of 0.25mm. The melting temperature was 1450℃ and the refining time was 6min. The obtained strip was sorted by a thickness sorter to remove qualified strips, and then loaded into a hydrogen crushing furnace for hydrogen crushing. It was then kept at 550℃ for 6.5h for dehydrogenation treatment to obtain coarse crushed powder. The coarse crushed powder was then ground in a gas flow mill under nitrogen atmosphere protection to obtain fine powder with an average particle size of 3.0μm.

[0055] (2) Add lubricant (0.03% isopropanol) to the air jet mill magnetic powder and stir. Then, it is oriented and formed under nitrogen atmosphere protection with an orientation magnetic field >1.7T. Then, it isostatically pressed and the vacuum film is removed in the oil stripping box under nitrogen protection. During the operation, ensure that the oxygen content is less than 100ppm. Place the pressed magnetic block into a graphite box and wait for sintering.

[0056] (3) The blanks placed in the graphite box are put into a vacuum sintering furnace for sintering. The blanks are sintered at 1060℃ for 6 hours, cooled to less than 50℃ by argon gas, and then heated to 900℃ for first-stage tempering for 2.5 hours. The blanks are cooled to less than 50℃ by argon gas, and then heated to 490℃ for second-stage tempering for 5 hours to prepare sintered NdFeB magnets.

[0057] (4) The prepared sintered NdFeB magnets were processed into magnetic sheets with dimensions of 20mm×20mm×2mm and marked as B. The surface of the sheets was degreased and activated, and then weighed separately. These sheets were then used as diffusion substrates for diffusion.

[0058] (5) Preparation of diffusion source solvent: Weigh 90g of crushed SmCo powder, weigh 135g of alcohol, and weigh 7g of epoxy resin, wherein the epoxy resin is 5.2% of the weight of alcohol and the weight ratio of alcohol to alloy powder is 1.5:1. First, add epoxy resin to alcohol and stir evenly with ultrasonic waves. Then, add the weighed alloy powder to the evenly mixed solution and continue to disperse it evenly into a uniform diffusion source with ultrasonic waves.

[0059] (6) Place the diffusion substrate and cover the substrate surface with screen printing. Weigh the coated magnetic sheet to ensure that the weight of the coating layer is 1% of the total weight of the coated magnetic sheet.

[0060] (7) Place the coated magnetic sheet into a molybdenum box, and then place it in a sintering furnace for diffusion treatment. Preheat the furnace to 300℃-450℃ for 2 hours. Then, raise the temperature to 850℃-950℃ and hold for 20 hours for homogenization heat treatment. The vacuum degree during the heating process should be below 10. -3 Pa. Then, a secondary heat treatment is performed, with the temperature set at 500-650℃ and the holding time at 5 hours. After the holding time is completed, argon gas is purged for cooling, and the refrigeration system is turned on for rapid cooling to obtain a high-performance, high-coercivity magnet.

[0061] After the heat preservation is completed, argon gas is used for cooling. The magnetic sheet is removed and labeled B1. The properties of the well-impregnated material B1 and the substrate B0 are measured using a magnetic property measuring instrument.

[0062] The performance comparison between B0 and B1 is shown in the table below.

[0063] magnetic sheet Br(KGS) Hcj(KOe) (BH)max(MGOe) HK / Hcj B0 14.62 14.12 53.65 96.8 B1 14.45 17.35 52.33 95.3

[0064] Example 4

[0065] (1) According to the proportion of PrNd(29.3)Fe69.23B0.92Cu0.2Ti0.15Ga0.2, the proportioned raw materials were processed by a rapid solidification process through a continuous vacuum melting furnace to obtain a strip with an average thickness of 0.25mm. The melting temperature was 1450℃ and the refining time was 6min. The obtained strip was sorted by a thickness sorter to remove qualified strips, and then loaded into a hydrogen crushing furnace for hydrogen crushing. It was then kept at 550℃ for 6.5h for dehydrogenation treatment to obtain coarse crushed powder. The coarse crushed powder was then ground in a gas flow mill under nitrogen atmosphere protection to obtain fine powder with an average particle size of 3.0μm.

[0066] (2) Add lubricant (0.03% isopropanol) to the air jet mill magnetic powder and stir. Then, it is oriented and formed under nitrogen atmosphere protection with an orientation magnetic field >1.7T. Then, it isostatically pressed and the vacuum film is removed in the oil stripping box under nitrogen protection. During the operation, ensure that the oxygen content is less than 100ppm. Place the pressed magnetic block into a graphite box and wait for sintering.

[0067] (3) The blanks placed in the graphite box are put into a vacuum sintering furnace for sintering. The blanks are sintered at 1060℃ for 6 hours, cooled to less than 50℃ by argon gas, and then heated to 900℃ for first-stage tempering for 2.5 hours. The blanks are cooled to less than 50℃ by argon gas, and then heated to 490℃ for second-stage tempering for 5 hours to prepare sintered NdFeB magnets.

[0068] (4) The prepared sintered NdFeB magnets were processed into magnetic sheets with dimensions of 20mm×20mm×2mm and marked as C. The surface of the sheets was degreased and activated, and then weighed separately. These sheets were used as diffusion substrates for diffusion.

[0069] (5) Preparation of diffusion source solvent: Weigh 85g of crushed SmCo powder, 3.5g of aluminum powder, 1.5g of copper powder, 135g of alcohol, and 7g of epoxy resin, wherein the epoxy resin is 5.2% of the weight of alcohol and the weight ratio of alcohol to alloy powder is 1.5:1. First, add epoxy resin to alcohol and stir evenly with ultrasonic waves. Then, add the weighed alloy powder to the evenly mixed solution and continue to disperse it evenly with ultrasonic waves to form a uniform diffusion source.

[0070] (6) Place the diffusion substrate and cover the substrate surface with screen printing. Weigh the coated magnetic sheet to ensure that the weight of the coating layer is 1% of the total weight of the coated magnetic sheet.

[0071] (7) Place the coated magnetic sheet into a molybdenum box, and then place it in a sintering furnace for diffusion treatment. Preheat the furnace to 300℃-450℃ for 2 hours. Then, raise the temperature to 850-950℃ and hold for 20 hours for homogenization heat treatment. The vacuum degree during the heating process should be below 10. -3 Pa. Then, a secondary heat treatment is performed, with the temperature set at 500-650℃ and the holding time at 5 hours. After the holding time is completed, argon gas is purged for cooling, and the refrigeration system is turned on for rapid cooling to obtain a high-performance, high-coercivity magnet.

[0072] After the heat preservation is completed, argon gas is used for cooling. The magnetic sheet is removed and labeled C1. The properties of the well-impregnated material C1 and the substrate C0 are measured using a magnetic property measuring instrument.

[0073] The performance comparison between C0 and C1 is shown in the table below.

[0074] magnetic sheet Br(KGS) Hcj(KOe) (BH)max(MGOe) HK / Hcj C0 14.62 14.12 53.65 96.8 C1 14.42 17.54 52.13 95.4

[0075] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A grain boundary diffusion source free of heavy rare earth elements, characterized in that: It is SmCo magnetic powder with a particle size of 1-5 μm.

2. The grain boundary diffusion source without heavy rare earth elements according to claim 1, characterized in that: It also includes mixed alloys of Al powder and Cu powder.

3. A diffusion solution prepared using the grain boundary diffusion source without heavy rare earth elements as described in claim 1 or 2, characterized in that: It includes the grain boundary diffusion source and diffusing agent without heavy rare earth as described in claim 1 or 2, wherein the diffusing agent includes a diluent and a curing agent.

4. The diffusion solution according to claim 3, characterized in that: The diluent is one or more of isopropanol, anhydrous alcohol, liquid paraffin, petroleum ether, and butanol.

5. The grain boundary diffusion source without heavy rare earth elements according to claim 4, characterized in that: The curing agent includes epoxy resin and / or polypropylene resin.

6. The grain boundary diffusion source without heavy rare earth elements according to claim 5, characterized in that: The volume percentage of the diluent and the curing agent is 9:

1.

7. A method for preparing a high coercivity magnet, characterized in that, Includes the following steps: (1) The neodymium iron boron magnet to be diffused is processed into a magnet with a thickness of <5mm on one side, and its shape is arbitrary; (2) Remove oil and pickle the surface of the processed magnet sheet, activate the surface, place it in an oven to dry, and then dry it for later use to obtain a pre-treated magnet sheet for later use. (3) The grain boundary diffusion source without heavy rare earth as described in claim 1 or 2 is mixed with a diffusion agent and then ultrasonically dispersed and stirred to form a suspension; (4) The uniformly mixed suspension is uniformly coated onto the surface of the magnet to be diffused by spraying, brushing or screen printing diffusion process, and then baked in an oven or drying tunnel at a temperature of 100-150℃, so that the alloy powder of the diffusion source is solidified on the surface of the magnet. (5) Place the magnet with the solidified diffusion source alloy powder in a graphite box or a metal molybdenum box and place it in a vacuum sintering furnace for diffusion treatment.

8. The method for preparing a high coercivity magnet according to claim 7, characterized in that: In step (3), the mass percentage of SmCo magnetic powder in the suspension is ≥90%.

9. The method for preparing a high coercivity magnet according to claim 8, characterized in that: In step (4), the magnet coated with diffusion source alloy powder is placed in a heating furnace and gradually heated to a temperature range of 300℃ to 450℃. It is then kept at this temperature for 1.5 to 4 hours for preheating treatment, and then heated to 800-1000℃ to allow the alloy powder to diffuse into the interior of the magnetic sheet.

10. The method for preparing a high coercivity magnet according to claim 9, characterized in that: Step (4) includes: First-stage heat treatment: Vacuum is applied, and the temperature is raised to 300-450℃ for preheating for 1.5-3 hours. Then, the temperature is raised to 850-950℃ and held for 5-20 hours for homogenization. The vacuum level during the heating process is below 10. -3 Pa, after the heat preservation is completed, argon gas is used for cooling; Secondary heat treatment: The magnetic sheet after primary heat treatment is subjected to secondary heat treatment at a temperature of 500-650℃ for 2.5-5 hours. After the heat treatment is completed, argon gas is used for cooling, and the refrigeration system is turned on for rapid cooling to obtain a high-performance magnet with high coercivity.