Preparation method of high-performance rare-earth-free neodymium-iron-boron magnet
By coating the surface of NdFeB coarse powder with lanthanum and cerium and adding Ga, Cu and Al, the grain boundary structure was optimized, the problem of uneven distribution of heavy rare earth elements was solved, and the preparation of heavy rare earth-free NdFeB magnets with high coercivity and high remanence was realized, thus improving the magnet performance and consistency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG ZHONGKE MAGNETIC IND
- Filing Date
- 2026-03-10
- Publication Date
- 2026-06-05
AI Technical Summary
Existing high-grade sintered NdFeB magnets rely on heavy rare earth elements Dy and Tb, resulting in uneven distribution, high price, and poor performance consistency, making it difficult to achieve high coercivity and high remanence without relying on heavy rare earth elements.
By uniformly coating the surface of NdFeB coarse powder with lanthanum and cerium, nano-scale rare earth oxides are formed. Combined with the addition of trace elements Ga, Cu and Al, the grain boundary structure is optimized, and a continuous grain boundary layer is formed during sintering, thereby improving the coercivity and thermal stability of the magnet.
Without relying on heavy rare earth elements, the coercivity and remanence of NdFeB magnets have been significantly improved, ensuring high performance and consistency of the magnets and reducing production costs.
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the field of magnetic materials technology, specifically to a method for preparing a high-performance heavy rare-earth neodymium iron boron magnet. Background Technology
[0002] Neodymium iron boron (NdFeB) magnets are the second strongest permanent magnets after holmium magnets at absolute zero, and are also the most commonly used rare-earth magnets. Due to their excellent properties of high remanence, high coercivity, and high energy product, they are widely used in permanent magnetic field devices and equipment such as electroacoustics, telecommunications, motors, instruments, nuclear magnetic resonance, magnetic levitation, and magnetic sealing. They are particularly suitable for manufacturing various high-performance products, such as VCM wafers for optical drive motors, heterogeneous magnets in the acoustic field, helical magnets in oil exploration drilling rigs, and various sizes and shapes of products in permanent magnet motors.
[0003] Currently, traditional high-grade sintered NdFeB magnets rely on the addition of heavy rare earth elements Dy and Tb to achieve high coercivity and high remanence. However, heavy rare earth elements Dy and Tb are scarce and expensive. When Dy and Tb are doped in trace amounts, the distribution of Dy and Tb is inconsistent, resulting in poor grain boundary continuity after high-temperature sintering and low product performance consistency.
[0004] Therefore, the present invention provides a method for preparing high-performance heavy rare earth-free NdFeB magnets to solve the above-mentioned technical problems. Summary of the Invention
[0005] The purpose of this invention is to provide a method for preparing high-performance heavy rare earth neodymium iron boron magnets. The prepared neodymium iron boron magnets have both high coercivity and high remanence, effectively ensuring their performance and quality.
[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a high-performance heavy rare-earth neodymium iron boron magnet includes the following steps: Step 1, Rapid solidification: The main phase alloy is batched according to the design ratio and added to a vacuum rapid solidification sintering furnace. It is preheated and refined at a temperature of 1400-1500℃, and then cast and cooled by copper rollers to obtain rapid solidification sheets. Step 2, Powder Mixing: The quick-setting flakes are put into the hydrogen crushing furnace for hydrogen crushing. After the hydrogen crushing is completed, the resulting coarse powder is pretreated. Then, antioxidants and lubricants are added to the pretreated coarse powder, and the mixture is stirred evenly. The resulting mixed powder is then stored for later use. Step 3, Powdering: The mixed powder obtained in Step 2 is prepared into fine powder with an average particle size of 2-3.5 μm by air jet milling; Step 4: Magnetic Field Forming and Isostatic Pressing: The obtained fine powder is placed in a sealed magnetic field press mold under nitrogen protection for magnetic orientation pressing to form a green body, which is then vacuum-sealed. Isostatic pressing is then applied and maintained to achieve a density of 4.2 ± 0.3 g / cm³. 3 raw blanks; Step 5, Sintering: The green blank obtained in Step 4 is placed in a vacuum sintering furnace, and after sintering and tempering, a high-performance heavy rare earth-free NdFeB magnet is obtained.
[0007] Furthermore, the main phase alloy is composed of the following components by mass percentage: 28-31 wt.% Pr25Nd75, 0.88-1.2 wt.% B, 0-0.1 wt.% Al, 0.05-0.3 wt.% Ti, 0.05-0.4 wt.% Cu, 0.5-1.4 wt.% Co, 0.1-0.4 wt.% Ga, with the balance being Fe.
[0008] Furthermore, the thickness of the rapidly solidified flakes is 0.15-0.5 mm, the proportion of columnar crystals is greater than 70%, and the rare earth-rich phase is uniformly distributed around the main phase grains without obvious agglomeration.
[0009] Furthermore, the method for preparing the pretreated coarse powder is as follows: Lanthanum nitrate and cerium nitrate are added to ethanol and fully dissolved to prepare a mixed solution with a lanthanum nitrate concentration of 0.1-0.2 mol / L and a cerium nitrate concentration of 0.1-0.15 mol / L. Under nitrogen protection, the coarse powder is immersed in the mixed solution with a mass of 3-5 times its weight, and ultrasonically vibrated at a frequency of 35-40 kHz while magnetically stirred at a rate of 120-180 r / min for 30-50 min. Then, the obtained mixed components are filtered, and the resulting solid filter material is placed in a vacuum drying oven and vacuum dried at 70-90℃ for 1-2 h to obtain the pretreated coarse powder.
[0010] Furthermore, the amount of antioxidant used is 0.05-0.1 wt.% of the pretreated coarse powder, and the antioxidant is any one of 2,6-di-tert-butyl-p-cresol, tert-butylhydroquinone, and butylated hydroxyanisole.
[0011] Furthermore, the amount of the lubricant used is 0.05-0.08 wt.% of the pretreated coarse powder, and the lubricant is any one of zinc stearate, aluminum stearate, and magnesium stearate.
[0012] Furthermore, the specific procedures for sintering and tempering are as follows: first, sinter at 1050-1100℃ for 4-5 hours, then cool to below 100℃; then perform a first-stage tempering at 880-920℃ for 2-3 hours, cool to below 80℃, then raise the temperature to 460-560℃, perform a second-stage tempering at this temperature for 4-6 hours, and then cool to room temperature.
[0013] Furthermore, during the hydrogen destruction process, hydrogen is absorbed at a temperature of 180-220℃ and a pressure of 0.1-0.3MPa for 2-3 hours, and then heated to 400-600℃ for dehydrogenation treatment at this temperature for 6-10 hours.
[0014] Furthermore, the conditions for magnetic field orientation pressing in step four are as follows: orientation molding is performed under nitrogen protection with a magnetic field strength of 1.5-2.5T and a pressure of 50-100MPa; then, cold isostatic pressing is performed at a pressure of 230-300MPa for 3-6 minutes.
[0015] Furthermore, the grinding pressure of the air jet mill during powder production is set to 5.8-6.2 MPa, and the powder output speed is set to 120-150 kg / h.
[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention involves impregnating hydrogen-degraded NdFeB coarse powder in a mixed solution containing lanthanum nitrate and cerium nitrate, followed by ultrasonic-magnetic stirring. This process uniformly coats the particle surface with lanthanum and cerium in the form of nitrates, which are then converted into nanoscale rare earth oxides during subsequent sintering. These highly active oxides, distributed at grain boundaries, effectively purify the grain boundary phase, inhibit abnormal growth of the main phase grains, and optimize the wettability of the rare earth-rich phase, promoting the formation of a continuous and thin grain boundary structure. This significantly improves the coercivity and thermal stability of the magnet without relying on heavy rare earth elements. Furthermore, the cavitation effect generated by ultrasonic vibration deeply cleans the particle surface and breaks up soft agglomerates. Combined with magnetic stirring, this ensures uniform coating, greatly improving the powder's dispersibility and surface condition. This benefits the subsequent air jet milling process to obtain fine powder with a concentrated particle size distribution and regular shape, and also enhances the powder's flowability and magnetic field orientation during the forming process, laying the foundation for achieving high remanence. In addition, the lanthanum-cerium precursor layer formed on the surface can also protect against oxygen during processing, reduce powder oxidation, and ensure the stability of magnetic properties.
[0017] 2. This invention achieves excellent magnetic properties even without heavy rare earth elements. The improved coercivity is also attributed to the addition of trace elements Ga, Cu, and Al, and the reduction of B content. During magnet sintering, the reduction of B content and the addition of Al significantly enhance the coercivity of the magnet, and the Nd6Fe exhibits strong wettability during sintering. 13 Ga phase along Nd2Fe 14 The B-phase grains are uniformly distributed, forming a continuous and thin grain boundary layer, which greatly enhances the coercivity of the magnet without significantly reducing the remanence. Detailed Implementation
[0018] 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.
[0019] Example 1 A method for preparing a high-performance heavy rare-earth neodymium iron boron magnet includes the following steps: Step 1, Rapid solidification: The main phase alloy is batched according to the design ratio and added to a vacuum rapid solidification spinning furnace. It is preheated and refined at a temperature of 1400℃, and then cast and cooled by copper rollers to obtain rapid solidification sheets. The main phase alloy is composed of the following components by mass percentage: 28wt.%Pr25Nd75, 0.88wt.%B, 0.05wt.%Ti, 0.05wt.%Cu, 0.5wt.%Co, 0.1wt.%Ga, with the balance being Fe; The thickness of the rapidly solidified flakes is 0.15 mm, the proportion of columnar crystals is greater than 70%, and the rare earth-rich phase is uniformly distributed around the main phase grains without obvious agglomeration. Step 2, Powder Mixing: The quick-setting flakes are put into the hydrogen crushing furnace for hydrogen crushing. After the hydrogen crushing is completed, the resulting coarse powder is pretreated. Then, antioxidants and lubricants are added to the pretreated coarse powder, and the mixture is stirred evenly. The resulting mixed powder is then stored for later use. In the hydrogen destruction process, hydrogen is absorbed at a temperature of 180℃ and a pressure of 0.1MPa for 2 hours, and then heated to 400℃ and dehydrogenated at this temperature for 10 hours. The amount of antioxidant used is 0.05 wt.% of the pretreated coarse powder, and the antioxidant is 2,6-di-tert-butyl-p-cresol; The amount of lubricant used is 0.05 wt.% of the pretreated coarse powder, and the lubricant is zinc stearate; Step 3, Powdering: The mixed powder obtained in Step 2 is prepared into fine powder with an average particle size of 2μm by air jet milling; wherein, the grinding pressure of air jet mill is set to 5.8MPa and the powder output speed is set to 120kg / h. Step 4: Magnetic Field Forming and Isostatic Pressing: The obtained fine powder is placed in a sealed magnetic field press mold under nitrogen protection for magnetic orientation pressing to form a green body, which is then vacuum-sealed. Isostatic pressing is then applied and maintained to achieve a density of 4.2 ± 0.3 g / cm³. 3 raw blanks; The conditions for magnetic field orientation pressing are as follows: orientation is performed under nitrogen protection with a magnetic field strength of 1.5T and a pressure of 50MPa; then, cold isostatic pressing is performed at a pressure of 230MPa for 6 minutes. Step 5, Sintering: The green blank obtained in Step 4 is placed in a vacuum sintering furnace, and after sintering and tempering, a high-performance heavy rare earth-free NdFeB magnet is obtained. The specific procedures for sintering and tempering are as follows: first, sinter at 1050℃ for 5 hours, then cool to below 100℃; then perform a first-stage tempering at 880℃ for 3 hours, cool to below 80℃, then raise the temperature to 460℃, perform a second-stage tempering at this temperature for 6 hours, and then cool to room temperature.
[0020] The pretreated coarse powder was prepared as follows: Lanthanum nitrate and cerium nitrate were added to ethanol and fully dissolved to prepare a mixed solution with a concentration of 0.1 mol / L for lanthanum nitrate and 0.1 mol / L for cerium nitrate. Under nitrogen protection, the coarse powder was immersed in a mixed solution with a mass of 3 times that of the lanthanum nitrate and treated with ultrasonic vibration at a frequency of 35 kHz and magnetic stirring at a rate of 120 r / min for 50 min. The resulting mixed component was then filtered, and the resulting solid filter material was placed in a vacuum drying oven and vacuum dried at 70℃ for 2 h to obtain the pretreated coarse powder.
[0021] Example 2 A method for preparing a high-performance heavy rare-earth neodymium iron boron magnet includes the following steps: Step 1, Rapid solidification: The main phase alloy is batched according to the design ratio and added to a vacuum rapid solidification spinning furnace. It is preheated and refined at a temperature of 1400℃, and then cast and cooled by copper rollers to obtain rapid solidification sheets. The main phase alloy is composed of the following components by mass percentage: 30wt.%Pr25Nd75, 1.0wt.%B, 0.05wt.%Al, 0.1wt.%Ti, 0.2wt.%Cu, 1.0wt.%Co, 0.3wt.%Ga, with the balance being Fe; The thickness of the rapidly solidified flakes is 0.3 mm, the proportion of columnar crystals is greater than 70%, and the rare earth-rich phase is uniformly distributed around the main phase grains without obvious agglomeration. Step 2, Powder Mixing: The quick-setting flakes are put into the hydrogen crushing furnace for hydrogen crushing. After the hydrogen crushing is completed, the resulting coarse powder is pretreated. Then, antioxidants and lubricants are added to the pretreated coarse powder, and the mixture is stirred evenly. The resulting mixed powder is then stored for later use. In the hydrogen destruction process, hydrogen is absorbed at a temperature of 200℃ and a pressure of 0.2MPa for 2 hours, and then heated to 500℃ and dehydrogenated at this temperature for 8 hours. The amount of antioxidant used was 0.08 wt.% of the pretreated coarse powder, and the antioxidant was tert-butylhydroquinone; The amount of lubricant used is 0.06 wt.% of the pretreated coarse powder, and the lubricant is aluminum stearate; Step 3, Powdering: The mixed powder obtained in Step 2 is prepared into fine powder with an average particle size of 3μm by air jet milling; wherein, the grinding pressure of air jet mill is set to 6.0MPa and the powder output speed is set to 130kg / h. Step 4: Magnetic Field Forming and Isostatic Pressing: The obtained fine powder is placed in a sealed magnetic field press mold under nitrogen protection for magnetic orientation pressing to form a green body, which is then vacuum-sealed. Isostatic pressing is then applied and maintained to achieve a density of 4.2 ± 0.3 g / cm³. 3 raw blanks; The conditions for magnetic field orientation pressing are as follows: orientation is performed under nitrogen protection with a magnetic field strength of 2.0T and a pressure of 80MPa; then, cold isostatic pressing is performed at a pressure of 250MPa for 5 minutes. Step 5, Sintering: The green blank obtained in Step 4 is placed in a vacuum sintering furnace, and after sintering and tempering, a high-performance heavy rare earth-free NdFeB magnet is obtained. The specific procedures for sintering and tempering are as follows: first, sinter at 1080℃ for 5 hours, then cool to below 100℃; then perform a first-stage tempering at 900℃ for 2 hours, cool to below 80℃, then raise the temperature to 500℃, perform a second-stage tempering at this temperature for 5 hours, and then cool to room temperature.
[0022] The pretreated coarse powder was prepared as follows: Lanthanum nitrate and cerium nitrate were added to ethanol and dissolved completely to prepare a mixed solution with a concentration of 0.15 mol / L for lanthanum nitrate and 0.15 mol / L for cerium nitrate. Under nitrogen protection, the coarse powder was immersed in a mixed solution with a mass of 4 times that of the lanthanum nitrate and subjected to ultrasonic vibration at a frequency of 35 kHz and magnetic stirring at a rate of 150 r / min for 40 min. The resulting mixed component was then filtered, and the resulting solid filter material was placed in a vacuum drying oven and vacuum dried at 80 °C for 2 h to obtain the pretreated coarse powder.
[0023] Example 3 A method for preparing a high-performance heavy rare-earth neodymium iron boron magnet includes the following steps: Step 1, Rapid solidification: The main phase alloy is batched according to the design ratio and added to a vacuum rapid solidification spinning furnace. It is preheated and refined at a temperature of 1500℃, and then cast and cooled by copper rollers to obtain rapid solidification sheets. The main phase alloy is composed of the following components by mass percentage: 31wt.%Pr25Nd75, 1.2wt.%B, 0.1wt.%Al, 0.3wt.%Ti, 0.4wt.%Cu, 1.4wt.%Co, 0.4wt.%Ga, with the balance being Fe; The thickness of the rapidly solidified flakes is 0.5 mm, the proportion of columnar crystals is greater than 70%, and the rare earth-rich phase is uniformly distributed around the main phase grains without obvious agglomeration. Step 2, Powder Mixing: The quick-setting flakes are put into the hydrogen crushing furnace for hydrogen crushing. After the hydrogen crushing is completed, the resulting coarse powder is pretreated. Then, antioxidants and lubricants are added to the pretreated coarse powder, and the mixture is stirred evenly. The resulting mixed powder is then stored for later use. In the hydrogen destruction process, hydrogen is absorbed at a temperature of 220℃ and a pressure of 0.3MPa for 2 hours, and then heated to 600℃ and dehydrogenated at this temperature for 6 hours. The amount of antioxidant used is 0.1 wt.% of the pretreated coarse powder, and the antioxidant is butylated hydroxyanisole; The amount of lubricant used is 0.08 wt.% of the pretreated coarse powder, and the lubricant is magnesium stearate; Step 3, Powdering: The mixed powder obtained in Step 2 is prepared into fine powder with an average particle size of 3.5 μm by air jet milling; wherein, the grinding pressure of air jet mill is set to 6.2 MPa and the powder output speed is set to 150 kg / h. Step 4: Magnetic Field Forming and Isostatic Pressing: The obtained fine powder is placed in a sealed magnetic field press mold under nitrogen protection for magnetic orientation pressing to form a green body, which is then vacuum-sealed. Isostatic pressing is then applied and maintained to achieve a density of 4.2 ± 0.3 g / cm³. 3 raw blanks; In step four, the conditions for magnetic field orientation pressing are as follows: orientation is performed under nitrogen protection with a magnetic field strength of 2.5T and a pressure of 100MPa; then, cold isostatic pressing is performed at a pressure of 300MPa for 3 minutes. Step 5, Sintering: The green blank obtained in Step 4 is placed in a vacuum sintering furnace, and after sintering and tempering, a high-performance heavy rare earth-free NdFeB magnet is obtained. The specific procedures for sintering and tempering are as follows: first, sinter at 1100℃ for 5 hours, then cool to below 100℃; then perform a first-stage tempering at 920℃ for 2 hours, cool to below 80℃, then raise the temperature to 560℃, perform a second-stage tempering at this temperature for 4 hours, and then cool to room temperature.
[0024] The pretreated coarse powder was prepared as follows: Lanthanum nitrate and cerium nitrate were added to ethanol and dissolved completely to prepare a mixed solution with a lanthanum nitrate concentration of 0.2 mol / L and a cerium nitrate concentration of 0.15 mol / L. Under nitrogen protection, the coarse powder was immersed in the mixed solution with a mass of 5 times that of the lanthanum nitrate and treated with ultrasonic vibration at a frequency of 40 kHz and magnetic stirring at a rate of 180 r / min for 30 min. The resulting mixed component was then filtered, and the resulting solid filter material was placed in a vacuum drying oven and vacuum dried at 90 ℃ for 1 h to obtain the pretreated coarse powder.
[0025] Comparative Example 1: The difference from Example 1 is that the coarse powder in the neodymium iron boron magnet prepared in this comparative example was not pretreated.
[0026] Comparative Example 2: The difference from Example 1 is that the neodymium iron boron magnet prepared in Example 5 of the invention patent with application number "CN202411572827.X" and title "A method for preparing a high coercivity and high thickness neodymium iron boron magnet".
[0027] Performance Testing: The NdFeB magnet samples prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to relevant performance tests according to GB / T 3217-2013 "Magnetic Test Methods for Permanent Magnet (Hard Magnet) Materials", and the test data are recorded in the table below: By comparing and analyzing the relevant data in the table, it can be seen that the NdFeB magnet prepared by this invention possesses both high coercivity and high remanence, effectively ensuring its performance and quality. This indicates that the preparation method of the high-performance heavy rare-earth-free NdFeB magnet provided by this invention has a broader market prospect and is more suitable for widespread application.
[0028] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0029] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims
1. A method for preparing a high-performance heavy rare-earth neodymium iron boron magnet, characterized in that, Includes the following steps: Step 1, Rapid solidification: The main phase alloy is batched according to the design ratio and added to a vacuum rapid solidification sintering furnace. It is preheated and refined at a temperature of 1400-1500℃, and then cast and cooled by copper rollers to obtain rapid solidification sheets. Step 2, Powder Mixing: The quick-setting flakes are put into the hydrogen crushing furnace for hydrogen crushing. After the hydrogen crushing is completed, the resulting coarse powder is pretreated. Then, antioxidants and lubricants are added to the pretreated coarse powder, and the mixture is stirred evenly. The resulting mixed powder is then stored for later use. Step 3, Powdering: The mixed powder obtained in Step 2 is prepared into fine powder with an average particle size of 2-3.5 μm by air jet milling; Step 4: Magnetic Field Forming and Isostatic Pressing: The obtained fine powder is placed in a sealed magnetic field press mold under nitrogen protection for magnetic orientation pressing to form a green body, which is then vacuum-sealed. Isostatic pressing is then applied and maintained to achieve a density of 4.2 ± 0.3 g / cm³. 3 raw blanks; Step 5, Sintering: The green blank obtained in Step 4 is placed in a vacuum sintering furnace, and after sintering and tempering, a high-performance heavy rare earth-free NdFeB magnet is obtained.
2. The method for preparing a high-performance heavy-earth-free neodymium iron boron magnet according to claim 1, characterized in that: The main phase alloy is composed of the following components by mass percentage: 28-31 wt.% Pr25Nd75, 0.88-1.2 wt.% B, 0-0.1 wt.% Al, 0.05-0.3 wt.% Ti, 0.05-0.4 wt.% Cu, 0.5-1.4 wt.% Co, 0.1-0.4 wt.% Ga, with the balance being Fe.
3. The method for preparing a high-performance heavy-earth-free neodymium iron boron magnet according to claim 1, characterized in that: The thickness of the rapidly solidifying flakes is 0.15-0.5 mm, and the proportion of columnar crystals is greater than 70%.
4. The method for preparing a high-performance heavy-earth-free neodymium iron boron magnet according to claim 1, characterized in that, The method for preparing the pretreated coarse powder is as follows: Lanthanum nitrate and cerium nitrate are added to ethanol and fully dissolved to prepare a mixed solution with a lanthanum nitrate concentration of 0.1-0.2 mol / L and a cerium nitrate concentration of 0.1-0.15 mol / L. Under nitrogen protection, the coarse powder is immersed in the mixed solution with a mass of 3-5 times its weight. The mixture is ultrasonically vibrated at a frequency of 35-40 kHz while being magnetically stirred at a rate of 120-180 r / min for 30-50 min. The resulting mixed component is then filtered, and the resulting solid filter material is placed in a vacuum drying oven and vacuum dried at 70-90℃ for 1-2 h to obtain the pretreated coarse powder.
5. The method for preparing a high-performance heavy-earth-free neodymium iron boron magnet according to claim 1, characterized in that: The amount of antioxidant used is 0.05-0.1 wt.% of the pretreated coarse powder, and the antioxidant is any one of 2,6-di-tert-butyl-p-cresol, tert-butylhydroquinone, and butylated hydroxyanisole.
6. The method for preparing a high-performance heavy-earth-free neodymium iron boron magnet according to claim 1, characterized in that: The amount of the lubricant used is 0.05-0.08 wt.% of the pretreated coarse powder, and the lubricant is any one of zinc stearate, aluminum stearate, and magnesium stearate.
7. The method for preparing a high-performance heavy-earth-free NdFeB magnet according to claim 1, characterized in that, The specific procedure for sintering and tempering is as follows: first, sinter at 1050-1100℃ for 4-5 hours, then cool to below 100℃; then perform a first-stage tempering at 880-920℃ for 2-3 hours, cool to below 80℃, then raise the temperature to 460-560℃, perform a second-stage tempering at this temperature for 4-6 hours, and then cool to room temperature.
8. The method for preparing a high-performance heavy-earth-free neodymium iron boron magnet according to claim 1, characterized in that: During the hydrogen destruction process, hydrogen is absorbed at a temperature of 180-220℃ and a pressure of 0.1-0.3MPa for 2-3 hours, and then heated to 400-600℃ and dehydrogenated at this temperature for 6-10 hours.
9. The method for preparing a high-performance heavy-earth-free neodymium iron boron magnet according to claim 1, characterized in that: The conditions for magnetic field orientation pressing in step four are as follows: orientation molding is performed under nitrogen protection with a magnetic field strength of 1.5-2.5T and a pressure of 50-100MPa; then, cold isostatic pressing is performed at a pressure of 230-300MPa for 3-6 minutes.
10. The method for preparing a high-performance heavy-earth-free neodymium iron boron magnet according to claim 1, characterized in that: The grinding pressure of the air jet mill during powder production is set to 5.8-6.2 MPa, and the powder output speed is set to 120-150 kg / h.