High-temperature-resistant neodymium-iron-boron magnet and preparation process thereof

Abstract

The invention discloses a high-temperature-resistant neodymium-iron-boron magnet and a preparation process thereof, and relates to the technical field of neodymium-iron-boron magnets, and the preparation method comprises the following steps: S1, preparing neodymium-iron-boron powder; s2, ternary auxiliary alloy is prepared, ternary auxiliary alloy powder and neodymium iron boron powder are mixed to be uniform, thin strip casting, hydrogen burst and jet milling processes are carried out, tri-n-butyl borate is added, uniform mixing is carried out, and doped neodymium iron boron powder is prepared; s3, preparing a neodymium iron boron magnet green body by taking the doped neodymium iron boron powder as a raw material; and S4, diffusion source alloy powder is prepared through an electric arc melting and melt spinning technology and a ball milling technology, the upper surface and the lower surface, perpendicular to the magnetic field direction, of the neodymium-iron-boron magnet blank are coated with the diffusion source alloy powder, heat treatment and vacuum annealing technologies are carried out, high-temperature-resistant varnish is sprayed to the surface of the magnet, vacuum drying is carried out, and the high-temperature-resistant neodymium-iron-boron magnet is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of neodymium iron boron magnets, and specifically to a high-temperature resistant neodymium iron boron magnet and its preparation process. Background Art

[0002] In the current rapid development of modern industry and electronic technology, rare earth permanent magnet materials play a crucial role due to their unique properties. Among them, neodymium iron boron, as a highly representative rare earth permanent magnet material, exhibits extremely outstanding characteristics. It has a very high magnetic energy product and coercivity, and the significant advantage of high energy density has brought innovation to many fields. In the field of instruments and meters, it helps equipment to be miniaturized, improving measurement accuracy and convenience; in electroacoustic motors, it promotes products towards lightweight development, reducing energy consumption while increasing efficiency; magnetic separation and magnetization equipment has also been thinned due to neodymium iron boron, optimizing working performance.

[0003] However, neodymium iron boron magnets face some challenges in practical applications. Due to its own characteristics, in a high-temperature environment, its magnetic properties are prone to decline, and its corrosion resistance is poor. To solve these problems, currently, protective treatments are usually carried out on the surface of neodymium iron boron magnets, such as electroplating, electroless plating, physical vapor deposition, or composite coatings. However, these traditional treatment methods have many drawbacks. The process operation is complex, with extremely high requirements for technology and equipment, increasing production costs and production difficulties. More critically, even after treatment, the high-temperature resistance performance of the magnet still cannot reach an ideal state. Under high-temperature working conditions, the deterioration of the magnet performance severely restricts its further application in fields with demanding high-temperature resistance requirements for materials, such as aerospace, new energy vehicles, and high-temperature industrial equipment.

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

[0005] The purpose of the present invention is to provide a high-temperature resistant neodymium iron boron magnet and its preparation process to solve the problems raised in the prior art.

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

[0007] A preparation process of a high-temperature resistant neodymium iron boron magnet, comprising the following steps:

[0008] S1: Prepare neodymium iron boron powder by using strip casting, hydrogen decrepitation, and jet milling processes;

[0009] S2: Prepare a ternary auxiliary alloy by means of arc melting process, conduct coarse crushing treatment in an argon atmosphere, mix the coarsely crushed ternary auxiliary alloy powder and neodymium iron boron powder evenly, carry out strip casting, hydrogen decrepitation and jet milling processes, add tributyl borate, and mix evenly to obtain doped neodymium iron boron powder;

[0010] S3: Place the doped neodymium iron boron powder in a magnetic field environment, conduct pressing, cold isostatic pressing, vacuum sintering and annealing processes perpendicular to the magnetic field to obtain a neodymium iron boron magnet blank;

[0011] S4: Prepare a diffusion source alloy powder by means of arc melting, melt spinning process and ball milling process, coat the diffusion source alloy powder on the upper and lower surfaces of the neodymium iron boron magnet blank perpendicular to the magnetic field direction, conduct heat treatment and vacuum annealing processes, spray high-temperature resistant varnish on the surface of the magnet, and conduct vacuum drying to obtain a high-temperature resistant neodymium iron boron magnet.

[0012] Further, in the preparation process of the doped neodymium iron boron powder, the mass ratio of neodymium iron boron powder to ternary auxiliary alloy powder is (95 - 97):(3 - 5); the addition amount of tributyl borate is 0.1 - 0.3 wt% of the total mass of neodymium iron boron powder and ternary auxiliary alloy powder; each component in the ternary auxiliary alloy includes: 90.5 wt% neodymium, 7.4 wt% cobalt, 2.1 wt% gallium.

[0013] Further, in the preparation process of the neodymium iron boron magnet blank, the perpendicular magnetic field strength is 1.8 - 2 T, the pressing pressure is 20 - 21 MPa, the cold isostatic pressing pressure is 14000 - 15000 kgf / cm 2 , the vacuum sintering temperature is 1070 - 1090 °C, the vacuum sintering time is 5 - 6 h, the annealing temperature is 450 - 470 °C, and the annealing time is 4 - 5 h.

[0014] Further, each component in the diffusion source alloy powder includes: 75 - y - z wt% terbium, y wt% aluminum, z wt% cerium, 20 wt% copper, 5 wt% zinc, where y = 0 - 30; z = 0 - 15.

[0015] Further, the total coating amount of the diffusion source alloy powder is 2 - 3 wt% of the mass of the neodymium iron boron magnet blank, and the coating amounts on the upper and lower surfaces of the neodymium iron boron magnet blank are the same.

[0016] Further, in the preparation process of the high-temperature resistant neodymium iron boron 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] Further, the preparation method of the high-temperature resistant varnish includes the following steps:

[0018] Prepare an ethanol aqueous solution with 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 h, cool to room temperature, filter, and dry in vacuum to obtain modified hollow glass microspheres;

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

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

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

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. In the present invention, by adding a ternary auxiliary alloy to the neodymium iron boron magnet, Co element can replace Fe in the grain boundary phase. The formed NdCo alloy has a relatively low melting point under specific compositions, is suitable for liquid phase sintering, and can improve the corrosion resistance of the magnet; Ga element inhibits the formation of the soft ferromagnetic phase and improves the intrinsic coercivity of the magnet. The two act synergistically to improve the high-temperature stability of the magnet.

[0024] 2. In the present invention, during the mixing process of the neodymium iron boron powder and the ternary auxiliary alloy powder, tributyl borate is additionally added as a lubricant. The purpose is to improve the orientation degree of the magnetic powder in the magnetic field forming stage, make it fully cover the surface of the magnetic powder, and then improve the arrangement of the magnetic powder in the magnetic field. Finally, the effects of improving the intrinsic coercivity and the maximum magnetic energy product of the magnet are achieved. By improving the intrinsic coercivity, the thermal stability of the magnet is enhanced, and the high-temperature resistance performance of the magnet is further strengthened.

[0025] 3. Further, the present invention coats alloy powder on the upper and lower surfaces of the sintered magnet blank. On the one hand, after the coated alloy powder is processed, a shell layer will be formed around the magnet grains, further inhibiting the nucleation of the reverse magnetization domain, thereby improving the coercivity. On the other hand, elements such as Cu and Zn tend to be distributed at the 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 coercivity 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, the present invention also realizes the heat insulation effect of the external environment by spraying a high-temperature resistant coating on the surface of the magnet, and further improves the maximum working temperature of the magnet without affecting the magnetic properties of the magnet itself. Using hollow glass microspheres as the heat insulation filler and combining with high-performance polyether nitrile ketone resin, the technical effects of low thermal conductivity and high coating thermal stability of the high-temperature resistant coating are achieved. Detailed Embodiments

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

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

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

[0030] Prepare an ethanol aqueous solution with 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 h, cool to room temperature, filter, and vacuum dry to obtain modified hollow glass microspheres;

[0031] Add 18 wt% of polyether nitrile ketone resin to N-methylpyrrolidone, stir evenly, add 0.5 wt% of KH-560, stir evenly, add 0.08 wt% of dispersant BYK310, 0.5 wt% of dispersant BYK354, stir evenly, and add 51.6 vol% of modified hollow glass microspheres, stir evenly to obtain the high-temperature resistant varnish.

[0032] Example 1: A preparation process of a high-temperature resistant neodymium iron boron magnet includes the following steps:

[0033] S1: Prepare neodymium iron boron powder by using strip casting, hydrogen explosion and air flow milling processes;

[0034] S2: Prepare ternary auxiliary alloy by using arc melting process, carry out coarse crushing treatment in argon atmosphere, mix 3wt% of the coarsely crushed ternary auxiliary alloy powder with 97wt% of neodymium iron boron powder evenly, carry out strip casting, hydrogen explosion and air flow milling processes, add 0.1wt% of tributyl borate, mix evenly to obtain doped neodymium iron boron powder;

[0035] S3: Place the doped neodymium iron boron powder in a magnetic field environment, carry out pressing at 20MPa under a 1.8T vertical magnetic field, 2 cold isostatic pressing at 14000kgf / cm, vacuum sintering at 1090°C for 5h, annealing process at 470°C for 4h to obtain a neodymium iron boron magnet blank;

[0036] S4: Prepare diffusion source alloy powder by using arc melting, melt spinning process and ball milling process, coat 2wt% of the diffusion source alloy powder on the upper and lower surfaces of the neodymium iron boron magnet blank perpendicular to the magnetic field direction, carry out heat treatment at 900°C for 6h and vacuum annealing at 500°C for 3h, spray high-temperature resistant varnish on the surface of the magnet, and vacuum dry to obtain a high-temperature resistant neodymium iron boron magnet.

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

[0038] Example 2: A preparation process of a high-temperature resistant neodymium iron boron magnet, including the following steps:

[0039] S1: Prepare neodymium iron boron powder by using strip casting, hydrogen explosion and air flow milling processes;

[0040] S2: Prepare ternary auxiliary alloy by using arc melting process, carry out coarse crushing treatment in argon atmosphere, mix 3wt% of the coarsely crushed ternary auxiliary alloy powder with 97wt% of neodymium iron boron powder evenly, carry out strip casting, hydrogen explosion and air flow milling processes, add 0.3wt% of tributyl borate, mix evenly to obtain doped neodymium iron boron powder;

[0041] S3: Place the doped neodymium iron boron powder in a magnetic field environment, carry out pressing at 20MPa under a 1.8T vertical magnetic field, 2 cold isostatic pressing at 14000kgf / cm, vacuum sintering at 1090°C for 5h, annealing process at 470°C for 4h to obtain a neodymium iron boron magnet blank;

[0042] S4: Prepare diffusion source alloy powder by arc melting, melt spinning process and ball milling process. Coat 2 wt% of the diffusion source alloy powder on the upper and lower surfaces of the NdFeB magnet blank perpendicular to the magnetic field direction, perform heat treatment at 900 °C for 6 h and vacuum annealing at 500 °C for 3 h, spray high-temperature resistant varnish on the surface of the magnet, and dry it in vacuum to obtain a high-temperature resistant NdFeB magnet.

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

[0044] Example 3: A preparation process of a high-temperature resistant NdFeB magnet, including the following steps:

[0045] S1: Prepare NdFeB powder by strip casting, hydrogen decrepitation and jet milling process;

[0046] S2: Prepare ternary auxiliary alloy by arc melting process, perform coarse crushing treatment in an argon atmosphere, mix 3 wt% of the coarsely crushed ternary auxiliary alloy powder with 97 wt% of the NdFeB powder evenly, perform strip casting, hydrogen decrepitation and jet milling process, add 0.3 wt% of tributyl borate, and mix evenly to obtain doped NdFeB powder;

[0047] S3: Place the doped NdFeB powder in a magnetic field environment, perform pressing at 20 MPa under a 1.8 T vertical magnetic field, 14000 kgf / cm 2 cold isostatic pressing, vacuum sintering at 1090 °C for 5 h, annealing process at 470 °C for 4 h to obtain an NdFeB magnet blank;

[0048] S4: Prepare diffusion source alloy powder by arc melting, melt spinning process and ball milling process. Coat 3 wt% of the diffusion source alloy powder on the upper and lower surfaces of the NdFeB magnet blank perpendicular to the magnetic field direction, perform heat treatment at 900 °C for 6 h and vacuum annealing at 500 °C for 3 h, spray high-temperature resistant varnish on the surface of the magnet, and dry it in vacuum to obtain a high-temperature resistant NdFeB magnet.

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

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

[0051] Prepare an ethanol aqueous solution with 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 h, cool to room temperature, filter, and dry in vacuum to obtain modified hollow glass microspheres;

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

[0053] Example 4: A preparation process of a high-temperature resistant neodymium iron boron magnet, comprising the following steps:

[0054] S1: NdFeB powder was prepared by strip casting, hydrogen bursting and jet milling processes;

[0055] S2: A ternary auxiliary alloy was prepared by arc melting process, and was coarsely crushed in an argon atmosphere. 3 wt% of the coarsely crushed ternary auxiliary alloy powder was mixed evenly with 97 wt% of NdFeB powder, and strip casting, hydrogen bursting and jet milling processes were carried out. 0.3 wt% of tributyl borate was added and mixed evenly to obtain doped NdFeB powder;

[0056] S3: The doped NdFeB powder was placed in a magnetic field environment, pressed at 20 MPa under a 1.8 T vertical magnetic field, cold isostatically pressed at 14000 kgf / cm 2 sintered in vacuum at 1090 °C for 5 h, and annealed at 470 °C for 4 h to obtain a NdFeB magnet blank;

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

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

[0059] Comparative Example 1: A preparation process of a high-temperature resistant neodymium iron boron magnet, comprising the following steps:

[0060] S1: NdFeB powder was prepared by strip casting, hydrogen bursting and jet milling processes; 0.1 wt% of tributyl borate was added and mixed evenly to obtain doped NdFeB powder;

[0061] S2: The doped NdFeB powder was placed in a magnetic field environment, pressed at 20 MPa under a 1.8 T vertical magnetic field, 14000 kgf / 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, 2wt% 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, heat treated at 900°C for 6h, vacuum annealed at 500°C for 3h, high temperature resistant varnish is sprayed on the magnet surface, vacuum dried, and high temperature resistant NdFeB magnet is obtained.

[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 preparation process of a high temperature resistant NdFeB magnet, comprising the following steps:

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

[0066] S2: preparing a ternary auxiliary alloy by an arc melting process, and coarsely crushing the ternary auxiliary alloy powder in an argon atmosphere, uniformly mixing 3wt% of the coarsely crushed ternary auxiliary alloy powder with 97wt% of NdFeB powder, and performing thin strip casting, hydrogen explosion and air flow milling processes to obtain doped NdFeB powder;

[0067] S3: Place the doped NdFeB powder in a magnetic field environment, press at 20MPa in a 1.8T vertical magnetic field, 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, 2wt% 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, heat treated at 900°C for 6h, vacuum annealed at 500°C for 3h, high temperature resistant varnish is sprayed on the magnet surface, vacuum dried, and high temperature resistant NdFeB magnet is obtained.

[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 preparation process of a high temperature resistant NdFeB magnet, comprising the following steps:

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

[0072] S2: Prepare a ternary auxiliary alloy by arc melting process, perform coarse crushing treatment in an argon atmosphere, mix 3 wt% of the coarsely crushed ternary auxiliary alloy powder with 97 wt% of neodymium iron boron powder evenly, perform strip casting, hydrogen cracking and jet milling processes, add 0.1 wt% of tributyl borate, and mix evenly to obtain doped neodymium iron boron powder;

[0073] S3: Place the doped neodymium iron boron powder in a magnetic field environment, perform pressing at 20 MPa under a 1.8 T vertical magnetic field, 14000 kgf / cm 2 cold isostatic pressing, vacuum sintering at 1090 °C for 5 h, annealing process at 470 °C for 4 h to obtain a neodymium iron boron magnet blank;

[0074] S4: Spray high-temperature resistant varnish on the surface of the neodymium iron boron magnet blank and dry it in vacuum to obtain a high-temperature resistant neodymium iron boron magnet.

[0075] Comparative Example 4: A preparation process of a high-temperature resistant neodymium iron boron magnet, comprising the following steps:

[0076] S1: Prepare neodymium iron boron powder by strip casting, hydrogen cracking and jet milling processes;

[0077] S2: Prepare a ternary auxiliary alloy by arc melting process, perform coarse crushing treatment in an argon atmosphere, mix 3 wt% of the coarsely crushed ternary auxiliary alloy powder with 97 wt% of neodymium iron boron powder evenly, perform strip casting, hydrogen cracking and jet milling processes, add 0.1 wt% of tributyl borate, and mix evenly to obtain doped neodymium iron boron powder;

[0078] S3: Place the doped neodymium iron boron powder in a magnetic field environment, perform pressing at 20 MPa under a 1.8 T vertical magnetic field, 14000 kgf / cm 2 cold isostatic pressing, vacuum sintering at 1090 °C for 5 h, annealing process at 470 °C for 4 h to obtain a neodymium iron boron magnet blank;

[0079] S4: Prepare diffusion source alloy powder by arc melting, melt spinning process and ball milling process, coat 2 wt% of the diffusion source alloy powder on the upper and lower surfaces of the neodymium iron boron magnet blank perpendicular to the magnetic field direction, perform heat treatment at 900 °C for 6 h and vacuum annealing at 500 °C for 3 h to obtain a high-temperature resistant neodymium iron boron magnet.

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

[0081] Experiment: Maximum working temperature test: Detect the above samples according to GB / T 13560-2017 "Sintered Neodymium Iron Boron Permanent Magnet Materials".

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

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

[0084] Table 1 Data sheet of performance test of NdFeB magnets

[0085]

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

[0087] In Comparative Example 1, the ternary auxiliary alloy powder was not added, resulting in a decrease in sintering density and a decrease in overall magnetic properties.

[0088] In Comparative Example 2, tributyl borate, a lubricant, was not added, resulting in difficulty in orientation of magnetic powder during the magnetic field forming stage and a decrease in the magnetic properties and the 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 coercivity of the magnet and a decrease in thermal stability.

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

[0091] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention.

Claims

1. A preparation process of a high temperature resistant NdFeB magnet, characterized in that: The following steps are involved: S1: NdFeB powder was prepared by strip casting, hydrogen explosion and jet milling; S2: preparing a ternary auxiliary alloy by an arc melting process, performing a coarse crushing treatment in an argon atmosphere, mixing the coarsely crushed ternary auxiliary alloy powder and the NdFeB powder evenly, performing a thin strip casting, hydrogen explosion and air flow milling process, adding tri-n-butyl borate, mixing evenly, and obtaining a 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, vacuum drying is performed, and high temperature resistant NdFeB magnet is obtained.

2. The preparation process of a high temperature resistant NdFeB magnet according to claim 1, characterized in that: 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; the components in the ternary auxiliary alloy include: 90.5wt% neodymium, 7.4wt% cobalt, and 2.1wt% gallium.

3. The preparation process of a high temperature resistant NdFeB magnet according to claim 1, characterized in that: During the preparation of NdFeB magnet blanks, 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.

4. The preparation process of a high temperature resistant NdFeB magnet according to claim 1, characterized in that: The components in 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 preparation process of a high temperature resistant NdFeB magnet according to claim 1, characterized in that: 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.

6. The preparation process of a high temperature resistant NdFeB magnet according to claim 1, characterized in that: In the preparation process of high temperature resistant NdFeB magnets, the heat treatment temperature is 900-905°C, the heat treatment time is 6-6.5h, the vacuum annealing temperature is 500-505°C, and the vacuum annealing time is 3-3.5h.

7. The preparation process of a high temperature resistant NdFeB magnet according to claim 1, characterized in that: The preparation method of the high temperature resistant varnish comprises the following steps: Prepare ethanol-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 3-4h, cool to room temperature, filter, and vacuum dry to obtain modified hollow glass microspheres; 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 high temperature resistant varnish.

8. The process for preparing a high temperature resistant NdFeB magnet according to claim 7, characterized in that: 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.

9. The preparation process of a high temperature resistant NdFeB magnet according to claim 1, characterized in that: The thickness of high temperature resistant varnish spraying is 0.2-0.8mm.

10. A high temperature resistant NdFeB magnet prepared according to the preparation process of a high temperature resistant NdFeB magnet according to any one of claims 1 to 9.

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