A high temperature resistant neodymium iron boron magnet and its preparation process

Abstract

The invention discloses a high-temperature resistant NdFeB magnet and a preparation process thereof, and relates to the technical field of NdFeB magnets. The preparation method comprises the following steps: S1: preparing NdFeB powder; S2: preparing a ternary auxiliary alloy, uniformly mixing the ternary auxiliary alloy powder and NdFeB powder, performing thin strip casting, hydrogen explosion and air flow milling processes, adding tri-n-butyl borate, and uniformly mixing to prepare doped NdFeB powder; S3: preparing a NdFeB magnet blank using the doped NdFeB powder as a raw material; S4: preparing diffusion source alloy powder by adopting arc melting, melt spinning and ball milling processes, coating the diffusion source alloy powder on the upper and lower surfaces of the NdFeB magnet blank perpendicular to the magnetic field direction, performing heat treatment and vacuum annealing processes, spraying a high-temperature resistant varnish on the magnet surface, and vacuum drying to obtain the high-temperature resistant NdFeB magnet.

Description

Technical Field

[0001] The present invention relates to the technical field of NdFeB magnets, in particular to a high-temperature resistant NdFeB magnet and a preparation process thereof. Background Art

[0002] In today's rapidly developing modern industry and electronics, rare earth permanent magnets, with their unique properties, play a key role. Among them, neodymium iron boron, a highly representative rare earth permanent magnet, exhibits exceptional properties. Its exceptionally high magnetic energy product and coercivity, along with its significant energy density, have revolutionized numerous fields. In the instrumentation field, it facilitates the miniaturization of equipment, improving measurement accuracy and convenience. In electroacoustic motors, it drives product lightweighting, reducing energy consumption while improving efficiency. NdFeB also enables thinner magnetic separation and magnetization equipment, optimizing performance.

[0003] However, NdFeB magnets face some challenges in practical applications. Due to their inherent characteristics, magnetic properties tend to degrade easily in high-temperature environments, and their corrosion resistance is poor. To address these problems, protective treatments are usually performed on the surface of NdFeB magnets, such as electroplating, chemical plating, physical vapor deposition, or composite coatings. However, these traditional treatment methods have many drawbacks, complex process operations, and extremely high requirements for technology and equipment, which increase production costs and difficulty. More importantly, even after treatment, the magnet's ability to withstand high temperatures still cannot reach the ideal state. Under high-temperature conditions, the deterioration of the magnet's performance has severely limited its further application in aerospace, new energy vehicles, high-temperature industrial equipment, and other fields that have stringent requirements for the material's high-temperature resistance.

[0004] Therefore, it is urgent to develop a NdFeB magnet with good high-temperature resistance and its preparation process, which is of great significance for expanding the application scope of NdFeB magnets and promoting the development of related industries. Summary of the Invention

[0005] The object of the present invention is to provide a high temperature resistant NdFeB magnet and a preparation process thereof, so as to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A preparation process for a high-temperature resistant NdFeB magnet comprises the following steps:

[0008] S1: NdFeB powder was prepared by strip casting, hydrogen detonation and jet milling.

[0009] S2: A ternary auxiliary alloy is prepared by arc melting, and the ternary auxiliary alloy powder is coarsely crushed in an argon atmosphere. The coarsely crushed ternary auxiliary alloy powder is evenly mixed with NdFeB powder, and thin strip casting, hydrogen detonation and jet milling are performed. Tri-n-butyl borate is added and mixed evenly to obtain doped NdFeB powder;

[0010] S3: placing the doped NdFeB powder in a magnetic field environment, performing pressing, cold isostatic pressing, vacuum sintering, and annealing processes perpendicular to the magnetic field to obtain a NdFeB magnet blank;

[0011] S4: Diffusion source alloy powder is prepared by arc melting, melt spinning and ball milling, and the diffusion source alloy powder is coated on the upper and lower surfaces of the NdFeB magnet blank perpendicular to the magnetic field direction, and heat treatment and vacuum annealing are performed. High-temperature resistant varnish is sprayed on the magnet surface, and vacuum drying is performed to obtain a high-temperature resistant NdFeB magnet.

[0012] Furthermore, during the preparation of the doped NdFeB powder, the mass ratio of NdFeB powder to ternary auxiliary alloy powder is (95-97): (3-5); the amount of tri-n-butyl borate added is 0.1-0.3wt% of the total mass of the NdFeB powder and the ternary auxiliary alloy powder; and the components of the ternary auxiliary alloy include: 90.5wt% neodymium, 7.4wt% cobalt, and 2.1wt% gallium.

[0013] Furthermore, during the preparation of the NdFeB magnet blank, the vertical magnetic field strength is 1.8-2T, the pressing pressure is 20-21MPa, and the cold isostatic pressing pressure is 14000-15000kgf / cm 2 The vacuum sintering temperature is 1070-1090℃, the vacuum sintering time is 5-6h, the annealing temperature is 450-470℃, and the annealing time is 4-5h.

[0014] Furthermore, the components of the diffusion source alloy powder include: 75-y-zwt% terbium, ywt% aluminum, zwt% cerium, 20wt% copper, and 5wt% zinc, wherein y=0-30; z=0-15.

[0015] Furthermore, the total coating amount of the diffusion source alloy powder is 2-3wt% of the mass of the NdFeB magnet blank, and the coating amount on the upper and lower surfaces of the NdFeB magnet blank is the same.

[0016] Furthermore, during the preparation of the high-temperature resistant NdFeB magnet, the heat treatment temperature is 900-905° C., the heat treatment time is 6-6.5 h, the vacuum annealing temperature is 500-505° C., and the vacuum annealing time is 3-3.5 h.

[0017] Furthermore, the preparation method of the high temperature resistant varnish comprises the following steps:

[0018] Prepare ethanol and water solution in a volume ratio of 15:1, add acetic acid to adjust the pH to 1.9-2.1, add KH-570, stir evenly, add hollow glass microspheres, heat to 70-75°C and stir for 3-4 hours, cool to room temperature, filter, and vacuum dry to obtain modified hollow glass microspheres;

[0019] Add polyether nitrile ketone resin to N-methyl pyrrolidone, stir evenly, add KH-560, stir evenly, add dispersants BYK310 and BYK354, stir evenly, add modified hollow glass microspheres, stir evenly to obtain a high temperature resistant varnish.

[0020] Furthermore, during the preparation of the modified hollow glass microspheres, the amount of KH-570 added is 10-12wt% of the mass of the hollow glass microspheres; during the preparation of the high-temperature resistant varnish, the concentration of the polyether nitrile ketone resin solution is 18-22wt%, the amount of KH-560 added is 0.5-1wt% of the mass of the polyether nitrile ketone resin, the amount of dispersant BYK310 added is 0.08-0.09wt% of the total mass of the high-temperature resistant varnish, the amount of dispersant BYK354 added is 0.5-0.6wt% of the total mass of the high-temperature resistant varnish, and the amount of modified hollow glass microspheres added is 51.6-61.5vol% of the total volume of the high-temperature resistant varnish.

[0021] Furthermore, the spraying thickness of the high temperature resistant varnish is 0.2-0.8 mm.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention adds a ternary auxiliary alloy to the NdFeB magnet. The Co element can replace the Fe in the grain boundary phase. The formed NdCo alloy has a low melting point under a specific composition, is suitable for liquid phase sintering, and can improve the corrosion resistance of the magnet; the Ga element inhibits the formation of the soft ferromagnetic phase and increases the intrinsic coercive force of the magnet. The synergistic effect of the two improves the high-temperature stability of the magnet.

[0024] 2. In the process of mixing NdFeB powder and ternary auxiliary alloy powder, the present invention additionally adds tri-n-butyl borate as a lubricant, with the aim of improving the orientation of the magnetic powder in the magnetic field forming stage so that it fully covers the surface of the magnetic powder, thereby improving the arrangement of the magnetic powder in the magnetic field, and ultimately achieving the effect of increasing the intrinsic coercive force and maximum magnetic energy product of the magnet. By increasing the intrinsic coercive force, the thermal stability of the magnet is improved, and the high temperature resistance of the magnet is further enhanced.

[0025] 3. The present invention further coats alloy powder on the upper and lower surfaces of the sintered magnet blank. On the one hand, after treatment, the coated alloy powder will form a shell around the magnet grains, further inhibiting the nucleation of the reverse magnetization domain, thereby improving the coercive force. On the other hand, elements such as Cu and Zn tend to be distributed at grain boundaries and triple grain boundaries. Zn can reduce the magnetization intensity of the grain boundary phase and enhance the decoupling effect between adjacent grains, which helps to improve the coercive force and further improve the performance and high temperature resistance of the magnet.

[0026] 4. In addition to improving the high-temperature resistance of the magnet itself, this invention also achieves thermal insulation from the external environment by spraying a high-temperature resistant coating on the magnet surface, further increasing the magnet's maximum operating temperature without affecting its own magnetic properties. By using hollow glass microspheres as insulating filler and combining them with a high-performance polyether nitrile ketone resin, the high-temperature resistant coating achieves both low thermal conductivity and high thermal stability. DETAILED DESCRIPTION

[0027] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0028] In the following examples, the hollow glass microspheres have a particle size of: 50 th %: 30, thermal conductivity: 0.078W·m -1 ·K -1 Specifications of polyether nitrile ketone resin: viscosity 0.46 dL / g; other raw materials are commercially available.

[0029] The preparation method of the high temperature resistant varnish comprises the following steps:

[0030] Prepare ethanol-water solution in a volume ratio of 15:1, add acetic acid to adjust the pH to 2, add 10 wt% KH-570, stir evenly, add hollow glass microspheres, heat to 70°C and stir for 3 hours, cool to room temperature, filter, and vacuum dry to obtain modified hollow glass microspheres;

[0031] 18 wt% of polyether nitrile ketone resin was added to N-methyl pyrrolidone and stirred evenly. 0.5 wt% of KH-560 was added and stirred evenly. 0.08 wt% of dispersant BYK310 and 0.5 wt% of dispersant BYK354 were added and stirred evenly. 51.6 vol% of modified hollow glass microspheres were added and stirred evenly to obtain a high-temperature resistant varnish.

[0032] Example 1: A process for preparing a high-temperature resistant NdFeB magnet, comprising the following steps:

[0033] S1: NdFeB powder was prepared by strip casting, hydrogen detonation and jet milling.

[0034] S2: A ternary auxiliary alloy is prepared by arc melting, and the ternary auxiliary alloy powder is coarsely crushed in an argon atmosphere. 3 wt% of the coarsely crushed ternary auxiliary alloy powder is uniformly mixed with 97 wt% of NdFeB powder, and thin strip casting, hydrogen detonation, and jet milling are performed. 0.1 wt% of tri-n-butyl borate is added and the mixture is uniformly mixed to obtain doped NdFeB powder;

[0035] S3: Place the doped NdFeB powder in a magnetic field environment, press it with a 1.8T vertical magnetic field at 20MPa and 14000kgf / cm 2 The NdFeB magnet blank was obtained by cold isostatic pressing, vacuum sintering at 1090℃ for 5h, and annealing at 470℃ for 4h.

[0036] S4: Diffusion source alloy powder is prepared by arc melting, melt spinning and ball milling. 2 wt% of the diffusion source alloy powder is coated on the upper and lower surfaces of the NdFeB magnet blank perpendicular to the magnetic field direction. The powder is heat treated at 900°C for 6 hours and vacuum annealed at 500°C for 3 hours. High-temperature resistant varnish is sprayed on the surface of the magnet and vacuum dried to obtain a high-temperature resistant NdFeB magnet.

[0037] The components of the diffusion source alloy powder include: 45wt% terbium, 15wt% aluminum, 15wt% cerium, 20wt% copper, and 5wt% zinc; the thickness of the high-temperature resistant varnish spraying is 0.8mm.

[0038] Example 2: A process for preparing a high-temperature resistant NdFeB magnet, comprising the following steps:

[0039] S1: NdFeB powder was prepared by strip casting, hydrogen detonation and jet milling.

[0040] S2: A ternary auxiliary alloy is prepared by arc melting, and the ternary auxiliary alloy powder is coarsely crushed in an argon atmosphere. 3 wt% of the coarsely crushed ternary auxiliary alloy powder is uniformly mixed with 97 wt% of NdFeB powder, and thin strip casting, hydrogen detonation, and jet milling are performed. 0.3 wt% of tri-n-butyl borate is added and the mixture is uniformly mixed to obtain doped NdFeB powder;

[0041] S3: Place the doped NdFeB powder in a magnetic field environment, press it with a 1.8T vertical magnetic field at 20MPa and 14000kgf / cm 2 The NdFeB magnet blank was obtained by cold isostatic pressing, vacuum sintering at 1090℃ for 5h, and annealing at 470℃ for 4h.

[0042] S4: Diffusion source alloy powder is prepared by arc melting, melt spinning and ball milling. 2 wt% of the diffusion source alloy powder is coated on the upper and lower surfaces of the NdFeB magnet blank perpendicular to the magnetic field direction. The powder is heat treated at 900°C for 6 hours and vacuum annealed at 500°C for 3 hours. High-temperature resistant varnish is sprayed on the surface of the magnet and vacuum dried to obtain a high-temperature resistant NdFeB magnet.

[0043] The components of the diffusion source alloy powder include: 45wt% terbium, 15wt% aluminum, 15wt% cerium, 20wt% copper, and 5wt% zinc; the thickness of the high-temperature resistant varnish spraying is 0.8mm.

[0044] Example 3: A process for preparing a high-temperature resistant NdFeB magnet, comprising the following steps:

[0045] S1: NdFeB powder was prepared by strip casting, hydrogen detonation and jet milling.

[0046] S2: A ternary auxiliary alloy is prepared by arc melting, and the ternary auxiliary alloy powder is coarsely crushed in an argon atmosphere. 3 wt% of the coarsely crushed ternary auxiliary alloy powder is uniformly mixed with 97 wt% of NdFeB powder, and thin strip casting, hydrogen detonation, and jet milling are performed. 0.3 wt% of tri-n-butyl borate is added and the mixture is uniformly mixed to obtain doped NdFeB powder;

[0047] S3: Place the doped NdFeB powder in a magnetic field environment, press it with a 1.8T vertical magnetic field at 20MPa and 14000kgf / cm 2 The NdFeB magnet blank was obtained by cold isostatic pressing, vacuum sintering at 1090℃ for 5h, and annealing at 470℃ for 4h.

[0048] S4: Diffusion source alloy powder is prepared by arc melting, melt spinning and ball milling. 3 wt% of the diffusion source alloy powder is coated on the upper and lower surfaces of the NdFeB magnet blank perpendicular to the magnetic field direction. The powder is heat treated at 900°C for 6 hours and vacuum annealed at 500°C for 3 hours. High-temperature resistant varnish is sprayed on the surface of the magnet and vacuum dried to obtain a high-temperature resistant NdFeB magnet.

[0049] The components of the diffusion source alloy powder include: 45wt% terbium, 15wt% aluminum, 15wt% cerium, 20wt% copper, and 5wt% zinc; the thickness of the high-temperature resistant varnish spraying is 0.8mm.

[0050] The preparation method of the high temperature resistant varnish in Example 4 comprises the following steps:

[0051] Prepare ethanol-water solution in a volume ratio of 15:1, add acetic acid to adjust the pH to 2, add 10 wt% KH-570, stir evenly, add hollow glass microspheres, heat to 70°C and stir for 3 hours, cool to room temperature, filter, and vacuum dry to obtain modified hollow glass microspheres;

[0052] 18 wt% of polyether nitrile ketone resin was added to N-methyl pyrrolidone and stirred evenly. 0.5 wt% of KH-560 was added and stirred evenly. 0.08 wt% of dispersant BYK310 and 0.5 wt% of dispersant BYK354 were added and stirred evenly. 61.5 vol% of modified hollow glass microspheres were added and stirred evenly to obtain a high temperature resistant varnish.

[0053] Example 4: A process for preparing a high-temperature resistant NdFeB magnet, comprising the following steps:

[0054] S1: NdFeB powder was prepared by strip casting, hydrogen detonation and jet milling.

[0055] S2: A ternary auxiliary alloy is prepared by arc melting, and the ternary auxiliary alloy powder is coarsely crushed in an argon atmosphere. 3 wt% of the coarsely crushed ternary auxiliary alloy powder is uniformly mixed with 97 wt% of NdFeB powder, and thin strip casting, hydrogen detonation, and jet milling are performed. 0.3 wt% of tri-n-butyl borate is added and the mixture is uniformly mixed to obtain doped NdFeB powder;

[0056] S3: Place the doped NdFeB powder in a magnetic field environment, press it with a 1.8T vertical magnetic field at 20MPa and 14000kgf / cm 2 The NdFeB magnet blank was obtained by cold isostatic pressing, vacuum sintering at 1090℃ for 5h, and annealing at 470℃ for 4h.

[0057] S4: Diffusion source alloy powder is prepared by arc melting, melt spinning and ball milling. 3 wt% of the diffusion source alloy powder is coated on the upper and lower surfaces of the NdFeB magnet blank perpendicular to the magnetic field direction. The powder is heat treated at 900°C for 6 hours and vacuum annealed at 500°C for 3 hours. High-temperature resistant varnish is sprayed on the surface of the magnet and vacuum dried to obtain a high-temperature resistant NdFeB magnet.

[0058] The components of the diffusion source alloy powder include: 45wt% terbium, 15wt% aluminum, 15wt% cerium, 20wt% copper, and 5wt% zinc; the thickness of the high-temperature resistant varnish spraying is 0.8mm.

[0059] Comparative Example 1: A process for preparing a high-temperature resistant NdFeB magnet, comprising the following steps:

[0060] S1: preparing NdFeB powder by strip casting, hydrogen detonation and jet milling; adding 0.1 wt% tri-n-butyl borate and mixing uniformly to obtain doped NdFeB powder;

[0061] S2: Place the doped NdFeB powder in a magnetic field environment, press it with a 1.8T vertical magnetic field at 20MPa and 14000kgf / cm 2The NdFeB magnet blank was obtained by cold isostatic pressing, vacuum sintering at 1090℃ for 5h, and annealing at 470℃ for 4h.

[0062] S3: Diffusion source alloy powder is prepared by arc melting, melt spinning and ball milling. 2 wt% of the diffusion source alloy powder is coated on the upper and lower surfaces of the NdFeB magnet blank perpendicular to the magnetic field direction. The powder is heat treated at 900°C for 6 hours and vacuum annealed at 500°C for 3 hours. High-temperature resistant varnish is sprayed on the surface of the magnet and vacuum dried to obtain a high-temperature resistant NdFeB magnet.

[0063] The components of the diffusion source alloy powder include: 45wt% terbium, 15wt% aluminum, 15wt% cerium, 20wt% copper, and 5wt% zinc; the thickness of the high-temperature resistant varnish spraying is 0.8mm.

[0064] Comparative Example 2: A process for preparing a high-temperature resistant NdFeB magnet, comprising the following steps:

[0065] S1: NdFeB powder was prepared by strip casting, hydrogen detonation and jet milling.

[0066] S2: A ternary auxiliary alloy is prepared by arc melting, and coarsely crushed in an argon atmosphere. 3 wt% of the coarsely crushed ternary auxiliary alloy powder is evenly mixed with 97 wt% of NdFeB powder, and thin strip casting, hydrogen detonation, and air flow milling are performed to obtain doped NdFeB powder;

[0067] S3: Place the doped NdFeB powder in a magnetic field environment, press it with a 1.8T vertical magnetic field at 20MPa and 14000kgf / cm 2 The NdFeB magnet blank was obtained by cold isostatic pressing, vacuum sintering at 1090℃ for 5h, and annealing at 470℃ for 4h.

[0068] S4: Diffusion source alloy powder is prepared by arc melting, melt spinning and ball milling. 2 wt% of the diffusion source alloy powder is coated on the upper and lower surfaces of the NdFeB magnet blank perpendicular to the magnetic field direction. The powder is heat treated at 900°C for 6 hours and vacuum annealed at 500°C for 3 hours. High-temperature resistant varnish is sprayed on the surface of the magnet and vacuum dried to obtain a high-temperature resistant NdFeB magnet.

[0069] The components of the diffusion source alloy powder include: 45wt% terbium, 15wt% aluminum, 15wt% cerium, 20wt% copper, and 5wt% zinc; the thickness of the high-temperature resistant varnish spraying is 0.8mm.

[0070] Comparative Example 3: A process for preparing a high-temperature resistant NdFeB magnet, comprising the following steps:

[0071] S1: NdFeB powder was prepared by strip casting, hydrogen detonation and jet milling.

[0072] S2: A ternary auxiliary alloy is prepared by arc melting, and the ternary auxiliary alloy powder is coarsely crushed in an argon atmosphere. 3 wt% of the coarsely crushed ternary auxiliary alloy powder is uniformly mixed with 97 wt% of NdFeB powder, and thin strip casting, hydrogen detonation, and jet milling are performed. 0.1 wt% of tri-n-butyl borate is added and the mixture is uniformly mixed to obtain doped NdFeB powder;

[0073] S3: Place the doped NdFeB powder in a magnetic field environment, press it with a 1.8T vertical magnetic field at 20MPa and 14000kgf / cm 2 The NdFeB magnet blank was obtained by cold isostatic pressing, vacuum sintering at 1090℃ for 5h, and annealing at 470℃ for 4h.

[0074] S4: spraying high temperature resistant varnish on the surface of the NdFeB magnet blank, and vacuum drying to obtain a high temperature resistant NdFeB magnet.

[0075] Comparative Example 4: A process for preparing a high-temperature resistant NdFeB magnet, comprising the following steps:

[0076] S1: NdFeB powder was prepared by strip casting, hydrogen detonation and jet milling.

[0077] S2: A ternary auxiliary alloy is prepared by arc melting, and the ternary auxiliary alloy powder is coarsely crushed in an argon atmosphere. 3 wt% of the coarsely crushed ternary auxiliary alloy powder is uniformly mixed with 97 wt% of NdFeB powder, and thin strip casting, hydrogen detonation, and jet milling are performed. 0.1 wt% of tri-n-butyl borate is added and the mixture is uniformly mixed to obtain doped NdFeB powder;

[0078] S3: Place the doped NdFeB powder in a magnetic field environment, press it with a 1.8T vertical magnetic field at 20MPa and 14000kgf / cm 2 The NdFeB magnet blank was obtained by cold isostatic pressing, vacuum sintering at 1090℃ for 5h, and annealing at 470℃ for 4h.

[0079] S4: Diffusion source alloy powder is prepared by arc melting, melt spinning and ball milling. 2 wt% of the diffusion source alloy powder is coated on the upper and lower surfaces of the NdFeB magnet blank perpendicular to the magnetic field direction, and then heat treated at 900 ° C for 6 hours and vacuum annealed at 500 ° C for 3 hours to obtain a high-temperature resistant NdFeB magnet.

[0080] The components of the diffusion source alloy powder include: 45 wt% terbium, 15 wt% aluminum, 15 wt% cerium, 20 wt% copper and 5 wt% zinc.

[0081] Experiment: Maximum operating temperature test: The above samples were tested in accordance with GB / T 13560-2017 "Sintered NdFeB Permanent Magnet Materials".

[0082] Magnetic property test: The above samples were tested according to GB / T 3217.

[0083] The experimental results are shown in Table 1 below.

[0084] Table 1 NdFeB magnet performance test data

[0085]

[0086] Conclusion: The NdFeB magnets prepared by the present invention have excellent magnetic properties and high temperature resistance.

[0087] In Comparative Example 1, no ternary auxiliary alloy powder was added, resulting in a decrease in sintering density and overall magnetic properties.

[0088] In Comparative Example 2, the lubricant tri-n-butyl borate was not added, which resulted in difficulty in orienting the magnetic powder during the magnetic field forming stage, and reduced magnetic properties and maximum operating temperature of the magnet.

[0089] In Comparative Example 3, the diffusion source alloy powder was not coated, resulting in a decrease in the coercive force of the magnet and a decrease in the thermal stability.

[0090] In Comparative Example 4, high-temperature resistant varnish was not sprayed, which resulted in an increase in the thermal conductivity between the magnet and the external ambient temperature, and a decrease in the maximum operating temperature.

[0091] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A preparation process for high temperature resistant NdFeB magnets, characterized by: The following steps are involved: S1: NdFeB powder was prepared by strip casting, hydrogen detonation and jet milling. S2: A ternary auxiliary alloy is prepared by arc melting, and the ternary auxiliary alloy powder is coarsely crushed in an argon atmosphere. The coarsely crushed ternary auxiliary alloy powder is evenly mixed with NdFeB powder, and thin strip casting, hydrogen detonation and jet milling are performed. Tri-n-butyl borate is added and mixed evenly to obtain doped NdFeB powder; S3: placing the doped NdFeB powder in a magnetic field environment, performing pressing, cold isostatic pressing, vacuum sintering, and annealing processes perpendicular to the magnetic field to obtain a NdFeB magnet blank; S4: arc melting, melt spinning and ball milling are used to prepare diffusion source alloy powder, the diffusion source alloy powder is coated on the upper and lower surfaces of the NdFeB magnet blank perpendicular to the magnetic field direction, heat treatment and vacuum annealing are performed, high temperature resistant varnish is sprayed on the magnet surface, and vacuum drying is performed to obtain a high temperature resistant NdFeB magnet; The preparation method of the high temperature resistant varnish, The method comprises the following steps: preparing an ethanol-water solution in a volume ratio of 15:1, adding acetic acid to adjust the pH to 1.9-2.1, adding KH-570, stirring evenly, adding hollow glass microspheres, heating to 70-75° C. and stirring for 3-4 hours, cooling to room temperature, filtering, and vacuum drying to obtain modified hollow glass microspheres; adding polyether nitrile ketone resin to N-methyl pyrrolidone, stirring evenly, adding KH-560, stirring evenly, adding dispersants BYK310 and BYK354, stirring evenly, adding modified hollow glass microspheres, stirring evenly, and obtaining a high-temperature resistant varnish; During the preparation of the modified hollow glass microspheres, the amount of KH-570 added was 10-12 wt% of the mass of the hollow glass microspheres; During the preparation of the high-temperature resistant varnish, the concentration of the polyether nitrile ketone resin solution is 18-22wt%, the amount of KH-560 added is 0.5-1wt% of the mass of the polyether nitrile ketone resin, the amount of dispersant BYK310 added is 0.08-0.09wt% of the total mass of the high-temperature resistant varnish, the amount of dispersant BYK354 added is 0.5-0.6wt% of the total mass of the high-temperature resistant varnish, and the amount of modified hollow glass microspheres added is 51.6-61.5vol% of the total volume of the high-temperature resistant varnish.

2. The process for preparing a high temperature resistant NdFeB magnet according to claim 1, wherein: During the preparation of doped NdFeB powder, the mass ratio of NdFeB powder to ternary auxiliary alloy powder is (95-97):(3-5); the amount of tri-n-butyl borate added is 0.1-0.3wt% of the total mass of the NdFeB powder and the ternary auxiliary alloy powder; and the components of the ternary auxiliary alloy include: 90.5wt% neodymium, 7.4wt% cobalt, and 2.1wt% gallium.

3. The process for preparing a high temperature resistant NdFeB magnet according to claim 1, wherein: During the preparation process of NdFeB magnet blanks, the vertical magnetic field strength is 1.8-2T, the pressing pressure is 20-21MPa, the cold isostatic pressing pressure is 14000-15000kgf / cm2, the vacuum sintering temperature is 1070-1090℃, the vacuum sintering time is 5-6h, the annealing temperature is 450-470℃, and the annealing time is 4-5h.

4. The process for preparing a high temperature resistant NdFeB magnet according to claim 1, wherein: The components of the diffusion source alloy powder include: 75-y-zwt% terbium, ywt% aluminum, zwt% cerium, 20wt% copper, and 5wt% zinc, wherein y=0-30; z=0-15.

5. The process for preparing a high temperature resistant NdFeB magnet according to claim 1, wherein: The total amount of the diffusion source alloy powder coated is 2-3wt% of the mass of the NdFeB magnet blank, and the coating amount on the upper and lower surfaces of the NdFeB magnet blank is the same.

6. The process for preparing a high temperature resistant NdFeB magnet according to claim 1, wherein: During the preparation of the high-temperature resistant NdFeB magnet, the heat treatment temperature is 900-905°C, the heat treatment time is 6-6.5 hours, the vacuum annealing temperature is 500-505°C, and the vacuum annealing time is 3-3.5 hours.

7. The process for preparing a high temperature resistant NdFeB magnet according to claim 1, wherein: The thickness of high temperature resistant varnish spraying is 0.2-0.8mm.

8. A high temperature resistant NdFeB magnet prepared according to the process for preparing a high temperature resistant NdFeB magnet according to any one of claims 1 to 7.

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