An apparatus, a method for preparing anisotropic neodymium-iron-boron magnetic powder, a neodymium-iron-boron magnetic powder

Abstract

The application provides a device, a method and a neodymium-iron-boron magnetic powder for preparing anisotropic neodymium-iron-boron magnetic powder, wherein the device is an HDDR diffusion treatment furnace, which comprises a powdering furnace body based on an HDDR process and a furnace body main cavity thereof, the powdering furnace body is provided with an outer cavity in close communication with the furnace body main cavity on the outer wall surface of the powdering furnace body, an opening and closing valve for storing and blocking diffusion source powder is arranged on the outer cavity adjacent to the furnace body main cavity, and a plurality of air permeable holes with a pore size smaller than the diffusion source powder are arranged on the blocking valve body of the opening and closing valve. The device, the method and the neodymium-iron-boron magnetic powder for preparing anisotropic neodymium-iron-boron magnetic powder provided by the application can significantly improve the coercive force and temperature stability of the anisotropic neodymium-iron-boron magnetic powder, thereby meeting the working temperature requirement of more than 120 DEG C in a specific field of micro special electric machines.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rare earth magnetic materials, in particular to a device and method for preparing anisotropic neodymium-iron-boron magnetic powder and the anisotropic neodymium-iron-boron magnetic powder. BACKGROUND

[0002] Neodymium-iron-boron rare earth permanent magnet materials are widely used in modern industry and high-tech fields due to their excellent magnetic properties. Neodymium-iron-boron magnets can be divided into sintered magnets and bonded magnets according to the manufacturing process. Sintered magnets can usually only be made into magnetic blocks, magnetic tiles and other product forms, and are more suitable for use in larger power motors. Bonded magnets are a mixture of magnetic powder and bonding agent, which are formed into magnets after near-net shaping. Bonded magnets have the advantages of high raw material utilization rate, good precision and complex shape, and can be made into light, small and thin magnetic ring product forms, and are particularly suitable for micro and special motors with power of a few watts to a few hundred watts, and are widely used in many fields such as automobiles, industrial automation, consumer electronics and household appliances.

[0003] There are mainly two types of bonded neodymium-iron-boron permanent magnet materials on the market. One type is isotropic bonded neodymium-iron-boron magnets, with a maximum magnetic energy product of 9-12 MGOe. The other type is anisotropic bonded neodymium-iron-boron magnets, with a maximum magnetic energy product of 17-25 MGOe. Isotropic bonded magnets randomly arrange the easy magnetization direction of the magnetic powder / magnet, and exhibit the same magnetic properties in all directions. Anisotropic bonded magnets have their easy magnetization direction pointing in the direction of use, and only in that direction do they have high magnetic properties. Therefore, the latter can provide twice the magnetic properties of the former in the direction of use.

[0004] With the development trend of miniaturization, lightweight, integration and energy saving of power electronic devices such as motors, higher requirements are placed on bonded magnets, i.e. to increase the magnetic energy product of the magnets, make the magnets smaller, thinner and lighter, and make the motors more efficient. Isotropic bonded magnets have lower performance and are difficult to meet the above development needs. Sintered magnets have high performance but need to be machined, and it is also difficult to prepare light, small and thin magnets suitable for micro and special motors. With the same volume and the same amount of rare earth, the performance of anisotropic magnets is twice that of isotropic magnets. Obviously, anisotropic magnets have obvious advantages in improving motor efficiency, reducing energy consumption, reducing weight and saving rare earth resources, and are particularly suitable for the energy saving and lightweight needs of automobiles, especially new energy vehicles. Anisotropic magnets have wide application space in the fields of automobiles, power tools, drones, robots and smart home appliances.

[0005] In the prior art, the HDDR process has become the most effective and economical method for preparing high-performance anisotropic Nd-Fe-B magnetic powder. However, the Nd-Fe-B magnetic material has the disadvantages of low Curie temperature point and poor temperature characteristics, and the new energy vehicles and other energy-saving and environment-friendly fields have higher requirements for the permanent magnet materials used, that is, not only high magnetic performance, but also high use temperature and long-term service stability. At present, the working temperature of the anisotropic Nd-Fe-B magnetic powder is not higher than 100℃, which is difficult to meet the working temperature requirement of more than 120℃ in specific fields of micro and special electric machines, and therefore it is urgent to develop anisotropic Nd-Fe-B magnetic powder with higher coercivity and temperature stability. SUMMARY

[0006] Therefore, the technical problem to be solved by the present application is to provide a device for preparing anisotropic Nd-Fe-B magnetic powder, which significantly improves the coercivity and temperature stability of the anisotropic Nd-Fe-B magnetic powder, and further meets the working temperature requirement of more than 120℃ in specific fields of micro and special electric machines.

[0007] To solve the technical problem of the first aspect, the present application provides a device for preparing anisotropic Nd-Fe-B magnetic powder, which is an HDDR diffusion treatment furnace, comprising a powder preparation furnace body based on the HDDR process and a furnace body main cavity thereof, wherein the powder preparation furnace body is provided with an outer cavity in the outer wall surface thereof, which is in close communication with the furnace body main cavity, an opening and closing valve for storing and blocking the diffusion source powder is arranged adjacent to the furnace body main cavity, and a plurality of air permeable holes with a smaller aperture than the diffusion source powder are arranged on the blocking valve body of the opening and closing valve.

[0008] Preferably, the outer cavity is provided with a movable cover at the upper end face thereof.

[0009] Preferably, a stirring plate is arranged in the furnace body main cavity, and / or the powder preparation furnace body is provided with a rotary driving device.

[0010] The technical problem to be solved by the present application is also to provide a method for preparing anisotropic Nd-Fe-B magnetic powder and / or a Nd-Fe-B magnetic powder, which significantly improves the coercivity and temperature stability of the anisotropic Nd-Fe-B magnetic powder, and further meets the working temperature requirement of more than 120℃ in specific fields of micro and special electric machines.

[0011] To solve the technical problem of the second aspect, the present application provides a method for preparing anisotropic Nd-Fe-B magnetic powder, which uses the device of any one of the embodiments of the first aspect, and comprises the following steps:

[0012] S1: preparation of diffusion source powder;

[0013] S2: separate storage of the magnetic powder material and the diffusion source powder;

[0014] S3: vacuumizing the main cavity and the outer cavity of the furnace body;

[0015] S4: starting the HDDR process to prepare powder, and the diffusion source powder is preheated in the outer cavity;

[0016] S5: as the HDDR preparation process proceeds, the barrier valve is opened, and the diffusion source powder mixes with the magnetic powder material in the high-temperature main cavity of the furnace body and undergoes grain boundary thermal diffusion;

[0017] S6: based on the grain boundary thermal diffusion treatment, anisotropic neodymium-iron-boron magnetic powder is prepared.

[0018] Preferably, the diffusion source powder is prepared from any one of rare earth elements, rare earth alloys, and rare earth hydrides.

[0019] Preferably, step S1 includes the following three preparation methods:

[0020] S11: when the diffusion source material is any one of rare earth elements, rare earth alloys, and rare earth hydrides, hydrogen treatment crushing is used to prepare granular powder with a particle size of 100-500 μm, and then crushing to 50 nm-50 μm;

[0021] S12: when the diffusion source material is any one of rare earth elements and rare earth alloys, high-temperature evaporation condensation is used to prepare powder particles with a particle size of 50 nm-50 μm;

[0022] S13: when the diffusion source material is any one of rare earth elements and rare earth alloys, atomization supercooling is used to prepare powder particles with a particle size of 50 nm-50 μm.

[0023] Preferably, in step S3, the main cavity and the outer cavity of the furnace body are both vacuumized to 10 -3 ~ 10 -2 Pa.

[0024] Preferably, step S5 includes the following specific execution steps:

[0025] S51: in the dehydrogenation stage of the HDDR preparation process, the barrier valve is opened, and the diffusion source powder enters the high-temperature main cavity of the furnace body;

[0026] S52: the stirring plate and / or the rotary drive device are started to fully mix the diffusion source powder with the magnetic powder material;

[0027] S53: the diffusion source powder undergoes grain boundary thermal diffusion on the surface of the magnetic powder material, enters the main phase along the grain boundary, widens the grain boundary of the magnetic powder, uniformly and continuously distributes the neodymium-rich phase, and improves the magnetic crystal anisotropy field around the neodymium-iron-boron main phase.

[0028] Preferably, step S6 includes the following specific execution steps:

[0029] S61: Dehydrogenation and recombination phase of the HDDR preparation process, which is carried out simultaneously with the grain boundary thermal diffusion treatment;

[0030] S62: After the furnace body is cooled, the anisotropic high-coercivity neodymium-iron-boron magnetic powder is prepared based on the grain boundary thermal diffusion treatment.

[0031] To solve the above-mentioned third technical problem, the present application provides a neodymium-iron-boron magnetic powder prepared by the method of any one of the second aspect.

[0032] Compared with the prior art, the device, method and neodymium-iron-boron magnetic powder for preparing anisotropic neodymium-iron-boron magnetic powder have the following beneficial effects:

[0033] The coercivity and temperature stability of the anisotropic neodymium-iron-boron magnetic powder are significantly improved, thereby meeting the working temperature requirement of more than 120 DEG C in a specific field of the micro special motor. BRIEF DESCRIPTION OF DRAWINGS

[0034] The accompanying drawings, which form a part of the present application, are intended to provide further understanding of the present application and are incorporated herein for explanation by way of the illustrative embodiments of the present application. The present application is not limited by the illustrative embodiments in the drawings.

[0035] Figure 1 It is a planar structure schematic diagram of the HDDR diffusion treatment furnace described in the embodiment 1 of the present application;

[0036] Figure 2 It is a three-dimensional schematic diagram of the on-off valve described in the embodiment 1 of the present application in the open and closed states of the valve body;

[0037] Figure 3 It is a process flow chart of the method for preparing anisotropic neodymium-iron-boron magnetic powder described in the embodiment 2 of the present application;

[0038] Figure 4 It is a mechanism schematic diagram of the magnetic powder material under the grain boundary thermal diffusion described in the embodiments 1-3 of the present application.

[0039] Explanation of reference signs:

[0040] 1-powder preparation furnace body, 11-furnace body main cavity, 2-outer cavity, 21-movable cover, 3-on-off valve, 31-block valve body, 311-air hole, 4-diffusion source powder, 5-magnetic powder material, 6-stirring plate. DETAILED DESCRIPTION

[0041] In order to make the above-mentioned objectives, technical solutions and advantages of the present application clearer and easier to understand, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein merely constitute part of the embodiments of the present application, and are only used to explain the present application and do not constitute a limitation on the present application. In the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0042] Embodiment 1

[0043] Referring to Figures 1-4 As shown in the drawings, the present application provides a device for preparing anisotropic neodymium-iron-boron magnetic powder, which is an HDDR diffusion treatment furnace, comprising a powdering furnace body 1 based on the HDDR process and a furnace body main cavity 11 thereof, the powdering furnace body 1 is provided with an outer cavity 2 in close communication with the furnace body main cavity 11 on the outer wall surface thereof, the outer cavity 2 is provided with a switching valve 3 for storing and blocking diffusion source powder 4 adjacent to the furnace body main cavity 11, and a plurality of air permeable holes 311 with a pore size smaller than the diffusion source powder 4 are formed in the blocking valve body 31 of the switching valve 3.

[0044] In the prior art, for the increase of coercivity and temperature stability of anisotropic neodymium-iron-boron magnetic powder, there are many ways known, including grain refinement, adding alloy elements, etc., but the most effective and most commonly used is to directly add a certain amount of heavy rare earth dysprosium or terbium in the neodymium-iron-boron alloy material. The heavy rare earth elements such as dysprosium and terbium replace Nd in the Nd2Fe 14 B grains, which will increase the magnetic crystal anisotropy field of the main phase, and greatly increase the coercivity of the magnet; however, heavy rare earth resources are scarce and expensive, and the use of traditional alloying method to increase the coercivity will greatly increase the production cost, and more seriously, due to the antiferromagnetic coupling between heavy rare earth ions and iron ions, the remanence and magnetic energy product will greatly decrease after adding heavy rare earth elements, therefore, it is necessary to develop a more economical preparation method of neodymium-iron-boron with high coercivity.

[0045] In the process of preparing the anisotropic Nd-Fe-B magnetic powder by the HDDR process, the blocking valve body 31 is initially closed. Since the pore diameter of the gas permeable hole 311 is smaller than the diffusion source powder 4, the gas permeable hole 311 only allows the gas to pass through, and the diffusion source powder 4 is stored in the outer cavity 2 and kept in a preheating state. After the blocking valve body 31 is opened, the diffusion source powder 4 subjected to the continuous preheating treatment can be directly added into the high-temperature main cavity 11 of the furnace body, so as to mix with the magnetic powder material 5 in the main cavity 11 of the furnace body and generate the grain boundary thermal diffusion. Since the melting point of the Nd-rich phase in the grain boundary of the magnetic powder is lower than that of the main phase of the Nd-Fe-B, the diffusion source powder 4 enters the internal structure of the magnetic powder material 5 through the grain boundary and then diffuses from the grain boundary to the main phase. Meanwhile, the grain boundary of the HDDR Nd-Fe-B magnetic powder is wide, and the Nd-rich phase is more uniformly and continuously distributed in the grain boundary, which meets the microstructure requirement of the HDDR anisotropic Nd-Fe-B magnetic powder with high coercivity and significantly improves the temperature stability. The diffusion source powder 4 can be a rare earth metal, alloy or compound.

[0046] Preferably, the outer cavity 2 is provided with a movable cover 21 at the upper end face thereof.

[0047] Specifically, the outer cavity 2 is in close communication with the main cavity 11 of the furnace body. The movable cover 21 is provided to facilitate the fastening and opening of the outer cavity 2, so as to facilitate the storage of the diffusion source powder 4 in the outer cavity 2 and ensure that the diffusion source powder 4 is subjected to the continuous preheating treatment in a closed state.

[0048] Preferably, the main cavity 11 of the furnace body is provided with a stirring plate 6, and / or the powder preparation furnace body 1 is provided with a rotary driving device.

[0049] Specifically, after the blocking valve body 31 is opened, the diffusion source powder 4 subjected to the continuous preheating treatment can be directly added into the high-temperature main cavity 11 of the furnace body. Under the action of the stirring plate 6 and / or the rotary driving device, the diffusion source powder 4 can be fully mixed with the magnetic powder material 5, so as to improve the grain boundary thermal diffusion effect.

[0050] Example 2

[0051] Referring to Figures 1-4 The application further provides a method for preparing an anisotropic Nd-Fe-B magnetic powder, which uses the device as described in the above embodiment 1. The method comprises the following steps:

[0052] S1: preparation of the diffusion source powder 4;

[0053] S2: storage of the magnetic powder material 5 and the diffusion source powder 4, respectively.

[0054] S3: vacuumizing the furnace main cavity 11 and the outer cavity 2;

[0055] S4: starting the HDDR process powder preparation, the diffusion source powder 4 is preheated in the outer cavity 2;

[0056] S5: as the HDDR process goes on, the barrier valve body 31 opens, the diffusion source powder 4 mixes with the magnetic powder material 5 in the high-temperature furnace main cavity 11 and the grain boundary thermal diffusion occurs;

[0057] S6: based on the grain boundary thermal diffusion treatment, the anisotropic neodymium-iron-boron magnetic powder is prepared.

[0058] Specifically, the HDDR process powder preparation mainly includes four stages of hydrogenation, disproportionation, dehydrogenation and recombination phase change. In the present application, the dehydrogenation and recombination phase change of the magnetic powder material 5 can be carried out at the same time as the grain boundary thermal diffusion treatment, so that the anisotropic neodymium-iron-boron magnetic powder prepared has the magnetic powder grain boundary widened, the neodymium-rich phase uniformly and continuously distributed, the magnetic crystal anisotropy field of the neodymium-iron-boron main phase improved, and the temperature stability significantly improved. In step S3, the movable cover 21 will be in a buckled state, the barrier valve body 31 will be in a closed state, and the furnace main cavity 11 and the outer cavity 2 will be vacuumized to 10 -3 ~ 10 -2 Pa.

[0059] As a comparative example, if the mixing and even the grain boundary thermal diffusion treatment of the diffusion source powder 4 are carried out outside the HDDR diffusion treatment furnace, the completely dehydrogenated or incompletely dehydrogenated magnetic powder material 5 needs to be taken out from the furnace main cavity 11, and the magnetic powder material 5 is easy to be in contact with air during the taking-out and mixing process, and the oxygen adsorbed on the surface of the magnetic powder material 5 is easy to be oxidized during the grain boundary thermal diffusion treatment, and the re-heating of the grain boundary thermal diffusion treatment in the furnace will also cause the grain to grow abnormally, all of which will result in the decrease of the coercivity of the magnetic powder, thus offsetting part of the effect of the grain boundary thermal diffusion treatment. In addition, the taking-out, mixing and re-heating of the magnetic powder material 5 increase the process procedures, reduce the efficiency and increase the cost. The process for preparing the anisotropic neodymium-iron-boron magnetic powder according to the present application directly mixes the magnetic powder material 5 and the diffusion source powder 4 in the HDDR process, and simultaneously carries out the grain boundary thermal diffusion treatment at high temperature, which significantly improves the coercivity and temperature stability of the magnetic powder, does not increase the process, avoids the oxidation of the magnetic powder and the abnormal growth of the grain, has high production efficiency, low cost, small equipment investment and is suitable for mass production.

[0060] Preferably, the diffusion source powder 4 is prepared from any one of rare earth elements, rare earth alloys and rare earth hydrides.

[0061] Specifically, the diffusion source material may be dysprosium, terbium, neodymium, praseodymium, etc. in rare earth single element, dysprosium-copper, dysprosium-iron, dysprosium-iron-gallium, dysprosium-iron-praseodymium, neodymium-copper-aluminum, etc. in low melting point alloy or eutectic alloy in rare earth alloy, dysprosium-hydrogen, dysprosium-iron-hydrogen, neodymium-copper-hydrogen, etc. in rare earth hydride, or dysprosium-fluorine, etc. in rare earth compound.

[0062] Preferably, the step S1 includes the following three preparation methods:

[0063] S11: When the diffusion source material is any one of rare earth single element, rare earth alloy, and rare earth hydride, hydrogen treatment is used for crushing to prepare particle powder with a particle size of 100-500 μm, and then crushing to 50 nm-50 μm;

[0064] S12: When the diffusion source material is any one of rare earth single element and rare earth alloy, high-temperature evaporation condensation is used to prepare powder particles with a particle size of 50 nm-50 μm;

[0065] S13: When the diffusion source material is any one of rare earth single element and rare earth alloy, atomization supercooling is used to prepare powder particles with a particle size of 50 nm-50 μm.

[0066] Specifically, the crushing method in the step S11 may be, for example, airflow milling or ball milling, and the atomization supercooling method in the step S13 may be, for example, ultrasonic atomization.

[0067] Preferably, the step S5 includes the following specific execution steps:

[0068] S51: In the dehydrogenation stage of the HDDR preparation process, the barrier valve body 31 is opened, and the diffusion source powder 4 enters the high-temperature furnace body main cavity 11;

[0069] S52: The stirring plate 6 and / or the rotary driving device are started to make the diffusion source powder 4 fully mixed with the magnetic powder material 5;

[0070] S53: The diffusion source powder 4 occurs grain boundary thermal diffusion on the surface of the magnetic powder material 5, enters the main phase along the grain boundary, widens the magnetic powder grain boundary, and makes the neodymium-rich phase uniformly and continuously distributed, and the magnetic crystal anisotropy field around the neodymium-iron-boron main phase is improved.

[0071] Preferably, the step S6 includes the following specific execution steps:

[0072] S61: The dehydrogenation and recombination phase change stages of the HDDR preparation process are performed simultaneously with the grain boundary thermal diffusion treatment;

[0073] S62: Based on the grain boundary thermal diffusion treatment, the anisotropy high-coercivity neodymium-iron-boron magnetic powder is prepared after the furnace body is cooled.

[0074] Table 1 - Properties of anisotropic bonded Nd-Fe-B magnets after diffusion treatment of the magnetic powder

[0075]

[0076] As a first preferred example of the present application, the diffusion source material dysprosium-iron alloy is hydrogen treated at 0.1 MPa hydrogen pressure and 700°C to break it up into powder having a particle size of about 150 μm, and then the dysprosium-iron alloy powder is ball milled in gasoline to a particle size of 500 nm to 5 μm, thereby obtaining the dysprosium-iron alloy powder in the diffusion source powder 4.

[0077] The furnace door of the powdering furnace body 1 and the movable cover 21 of the outer chamber 2 are opened, the neodymium-iron-boron material is filled into the main chamber 11 of the furnace body, and the dysprosium-iron alloy powder is stored in the outer chamber 2. Then the furnace door of the powdering furnace body 1 and the movable cover 21 of the outer chamber 2 are closed, the powdering furnace is evacuated to 10 -2 Pa, and the HDDR process is started to prepare the magnetic powder.

[0078] During the dehydrogenation stage of the HDDR process, the barrier valve body 31 is opened, and the dysprosium-iron alloy powder flows into the high-temperature main chamber 11 of the furnace body. Under the action of the stirring plate 6 and / or the rotary drive device, the neodymium-iron-boron material and the dysprosium-iron alloy powder are thoroughly mixed in the main chamber 11 of the furnace body. At this time, the temperature in the main chamber 11 of the furnace body is about 650 to 850°C, and the dehydrogenation, re-complex phase transformation and grain boundary thermal diffusion treatment of the neodymium-iron-boron material are carried out simultaneously. After 50 min, the heating is stopped, and the diffusion-treated anisotropic neodymium-iron-boron magnetic powder is obtained. The bonded magnets are prepared by orientation under a magnetic field of 2.0 T. The properties of the bonded magnets before and after diffusion are compared in Table 1.

[0079] As a second preferred example of the present application, a neodymium-copper-gallium alloy powder having a particle size of less than 10 μm is prepared by ultrasonic atomization;

[0080] The furnace door of the powdering furnace body 1 and the movable cover 21 of the outer chamber 2 are opened, the neodymium-iron-boron material is filled into the main chamber 11 of the furnace body according to a mass ratio of 97:3, and the neodymium-copper-gallium alloy powder is stored in the outer chamber 2. Then the furnace door of the powdering furnace body 1 and the movable cover 21 of the outer chamber 2 are closed, the powdering furnace is evacuated to 10 -2 Pa, and the HDDR process is started to prepare the magnetic powder.

[0081] In the dehydrogenation stage of the HDDR process, the barrier valve 31 is opened, and the neodymium copper gallium alloy powder flows into the high-temperature furnace main cavity 11. Under the action of the stirring plate 6 and / or the rotary drive device, the neodymium / praseodymium iron boron material and the neodymium copper gallium alloy powder are fully mixed in the furnace main cavity 11. At this time, the temperature in the furnace main cavity 11 is about 750-900°C, and the neodymium / praseodymium iron boron material is simultaneously subjected to dehydrogenation, re-complex phase transformation and grain boundary thermal diffusion treatment. After 45 minutes, the heating is stopped, and the diffusion-treated anisotropic neodymium / praseodymium iron boron magnetic powder is obtained after cooling. The bonded magnets prepared by orientation under a 2.0T magnetic field have the performance shown in Table 1.

[0082] Example 3

[0083] Referring to Figures 1-4 The present application also provides a neodymium iron boron magnetic powder, which is prepared by the method described in Example 2.

[0084] Specifically, those skilled in the art can understand that the neodymium iron boron magnetic powder provided in Example 3, when prepared by the method described in Example 2, solves the technical problem and achieves the technical effect, which can be seen from the description of the method for preparing anisotropic neodymium iron boron magnetic powder in Example 2, and will not be repeated here.

[0085] Although the present application is disclosed as above, the present application is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application, and therefore the protection scope of the present application should be subject to the scope defined by the claims.

Claims

1. A method for preparing anisotropic NdFeB magnetic powder, characterized in that, The method uses an apparatus for preparing anisotropic NdFeB magnetic powder, which is an HDDR diffusion treatment furnace. The HDDR diffusion treatment furnace includes a powder preparation furnace body (1) based on the HDDR process and its main cavity (11). The powder preparation furnace body (1) has an outer cavity (2) that is in closed-loop communication with the main cavity (11) on its outer wall surface. The outer cavity (2) is provided with a switch valve (3) for storing and blocking the diffusion source powder (4) near the main cavity (11). The blocking valve body (31) of the switch valve (3) has a plurality of vent holes (311) with a diameter smaller than that of the diffusion source powder (4). The outer cavity (2) is provided with a movable cover (21) at its upper end face; The diffusion source powder (4) is prepared from any one of the following diffusion source materials: rare earth elements, rare earth alloys, and rare earth hydrides. The method includes the following steps: S1: Preparation of diffusion source powder (4); S2: Separate storage of magnetic powder material (5) and diffusion source powder (4); S3: Vacuuming is performed on the main cavity (11) and outer cavity (2) of the furnace body; S4: Start HDDR process powder making, and the diffusion source powder (4) is preheated in the outer cavity (2); S5: As the HDDR preparation process proceeds, the barrier valve (31) opens, and the diffusion source powder (4) and magnetic powder material (5) mix and undergo grain boundary thermal diffusion in the high-temperature furnace main cavity (11). S6: Anisotropic NdFeB magnetic powder was prepared with the support of grain boundary thermal diffusion treatment; Step S6 includes the following specific execution steps: S61: The temperature of the main cavity (11) of the furnace body is 650~900℃. The dehydrogenation and recombination phase transformation stage of the HDDR preparation process is carried out simultaneously with the grain boundary thermal diffusion treatment. S62: Stop heating after 45 or 50 minutes. With the help of grain boundary thermal diffusion treatment, anisotropic high coercivity NdFeB magnetic powder is prepared after the furnace body cools down. In step S3, the active cover (21) will be in a locked state and the barrier valve body (31) will be in a closed state.

2. The method for preparing anisotropic NdFeB magnetic powder according to claim 1, characterized in that, The main cavity (11) of the furnace body is equipped with a stirring plate (6), and / or the furnace body (1) of the pulverizing furnace is equipped with a rotary drive device.

3. The method for preparing anisotropic NdFeB magnetic powder according to claim 1, characterized in that, Step S1 uses any one of the following three preparation methods: (1): When the diffusion source material is any one of rare earth elements, rare earth alloys, or rare earth hydrides, hydrogen treatment is used to crush it and prepare particle powder with a particle size of 100~500μm, which is then crushed to 50nm~50μm. (2): When the diffusion source material is any one of rare earth elements or rare earth alloys, powder particles with a particle size of 50nm~50μm are prepared by high-temperature evaporation and condensation. (3): When the diffusion source material is any one of rare earth elements or rare earth alloys, powder particles with a particle size of 50nm~50μm are prepared by atomization and extreme cooling.

4. The method for preparing anisotropic NdFeB magnetic powder according to claim 1, characterized in that, In step S3, both the main cavity (11) and the outer cavity (2) of the furnace body are evacuated to a high vacuum of 10. -3 ~10 -2 Pa.

5. The method for preparing anisotropic NdFeB magnetic powder according to claim 1, characterized in that, Step S5 includes the following specific execution steps: S51: During the dehydrogenation stage of the HDDR preparation process, the barrier valve (31) is opened, and the diffusion source powder (4) enters the high-temperature furnace main cavity (11); S52: The stirring plate (6) and / or the rotary drive device are activated to fully mix the diffusion source powder (4) with the magnetic powder material (5); S53: The diffusion source powder (4) undergoes grain boundary thermal diffusion on the surface of the magnetic powder material (5), enters the main phase along the grain boundary, widens the magnetic powder grain boundary, and makes the NdFeB-rich phase evenly and continuously distributed, thereby increasing the magnetic anisotropy field of the NdFeB main phase.

6. A neodymium iron boron magnetic powder, characterized in that, Prepared using the method described in any one of claims 1-5.

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