A method for producing an Nd-Fe-B permanent magnetic powder

Abstract

This invention provides a method for preparing Nd-Fe-B permanent magnet powder. The method includes: mixing iron, iron-boron alloy, neodymium source (neodymium oxide and / or neodymium chloride) with rare earth hydrides (as reducing agents, preferably lanthanum hydride and / or cerium hydride), ball milling the mixture, and pressing the resulting mixture into a blank; subjecting the blank to vacuum heat treatment to obtain crude Nd-Fe-B magnetic powder material; crushing the crude Nd-Fe-B magnetic powder material, and then transferring it to a washing liquid for cleaning to remove residual non-magnetic impurities in the solid phase, thereby obtaining the Nd-Fe-B magnetic powder. Compared with conventional methods that use calcium as a reducing agent to prepare Nd-Fe-B permanent magnet powder, the preparation method provided by this invention has advantages such as lower reducing agent dosage, lower heat treatment temperature, shorter time, and effectively reduces the preparation cost of Nd-Fe-B permanent magnet powder.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet powder preparation technology, and in particular to a method for preparing Nd-Fe-B permanent magnet powder. Background Technology

[0002] Rare earth permanent magnet materials are widely used in information technology, industrial production, aerospace, and emerging fields such as new energy vehicles and robotics due to their excellent magnetic properties. With the development of precision, integration, and personalization of magnetic components, higher requirements are being placed on the magnetic properties of materials and the manufacturing cost.

[0003] In recent years, many researchers have focused on calcium thermal reduction, a method that uses rare earth oxides as raw materials and is widely used in the preparation of NdFeB powder due to its short process and low pollution. However, when using calcium as a reducing agent to prepare NdFeB powder, solid Ca must first be melted (melting point 842 °C) to form liquid Ca, and then contacted with NdFeB oxide through liquid diffusion. The required reduction temperature is usually greater than 1000 °C to overcome the solid-solid reaction barrier, resulting in high energy consumption. Furthermore, the fluidity of liquid Ca can easily lead to local over- or under-reaction. In addition, the byproduct CaO (melting point 2614 °C) generated by the reaction easily forms a dense oxide layer on the surface of the reactant particles. The encapsulation effect of CaO hinders the contact between Ca and unreacted NdFeB oxide, leading to incomplete reaction. On the other hand, in the process of using calcium as a reducing agent to prepare NdFeB powder, it has been found that in order to completely reduce the rare earth oxides and ensure thorough reduction diffusion, a calcium metal amount much larger than the stoichiometric ratio needs to be added. Since obtaining calcium metal usually requires a large amount of calcium carbonate as raw material, and the production process requires high-purity calcium oxide, the subsequent electrolysis or aluminothermic reduction method is very energy-intensive and the purification process is complicated, resulting in excessively high market prices, thus increasing the cost of calcium reduction process.

[0004] Therefore, improving the preparation method of Nd-Fe-B permanent magnet materials to effectively reduce costs and enhance the magnetic properties of the materials has become a current hot topic. Summary of the Invention

[0005] To address the problems existing in the background art, the present invention provides a method for preparing Nd-Fe-B permanent magnet powder with high efficiency and low cost, thus solving at least one of the problems mentioned in the background; the specific invention content is as follows:

[0006] This invention provides a method for preparing Nd-Fe-B permanent magnet powder, the method comprising:

[0007] Iron, iron-boron alloy, neodymium source and reducing agent rare earth hydride are mixed and ball-milled to obtain a billet.

[0008] The blank is subjected to vacuum heat treatment to obtain coarse NdFeB magnetic powder material;

[0009] After the crude NdFeB magnetic powder material is crushed, it is cleaned to remove the non-magnetic impurities remaining in the solid phase, and then dried to obtain the NdFeB magnetic powder.

[0010] The reducing agent rare earth hydride is selected from lanthanum hydride and / or cerium hydride;

[0011] The neodymium source is selected from neodymium oxide and / or neodymium chloride powder.

[0012] Optionally, the mass ratio of the reducing agent rare earth hydride to the neodymium source is (2.6~5):1;

[0013] The mass ratio of the iron, the iron-boron alloy, and the neodymium source is 13:1:(1~3).

[0014] Optionally, the ball-to-material ratio in the ball mill is (10-20):1, and the ball milling time is 1-10 h.

[0015] Optionally, the briquetting process is carried out by cold pressing, and the pressure used for the briquetting is 20-30 MPa.

[0016] Optionally, the target temperature for the vacuum heat treatment is 850-1100 ℃, the heating rate is 2-25 ℃ / min, and the holding time is 10 min-6 h.

[0017] Optionally, the cleaning process includes: sequentially using an acidic washing solution, deionized water, and an ethanol solution to perform multi-step cleaning on the crude NdFeB magnetic powder; the acidic washing solution is a hydrochloric acid solution or a glacial acetic acid solution with a concentration of 1-5%.

[0018] Optionally, the reducing agent rare earth hydride is obtained by hydrogen explosion of lanthanum or cerium metal.

[0019] The particle size of the reducing agent rare earth hydride is 50-150 μm.

[0020] Optionally, the particle size of the iron-boron alloy is 1-3 μm;

[0021] The iron has a particle size of 30 nm to 20 μm.

[0022] Optionally, before ball milling, the neodymium source is subjected to vacuum heat treatment at 200-400 °C for 3-6 h to remove residual moisture and obtain dry anhydrous neodymium oxide.

[0023] Optionally, the method further includes: adding an appropriate amount of flux to the mixture, mixing it evenly, and then pressing it into briquettes to obtain a green body;

[0024] The flux is selected from BiCl3, CaCl2, KCl and / or LaCl3.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] This invention provides a method for preparing Nd-Fe-B permanent magnet powder. The method includes: mixing iron, iron-boron alloy, neodymium source, and rare earth hydride reducing agent, followed by ball milling, and then pressing the ball-milled mixture into briquettes to obtain a blank; subjecting the blank to vacuum heat treatment to obtain coarse Nd-Fe-B magnetic powder material; crushing the coarse Nd-Fe-B magnetic powder material, and then transferring it to a washing liquid for cleaning to remove residual non-magnetic impurities in the solid phase to obtain the Nd-Fe-B magnetic powder. Compared with conventional methods using calcium as a reducing agent to prepare Nd-Fe-B permanent magnet powder, the preparation method provided by this invention has the advantages of a shorter preparation process, less reducing agent, lower heat treatment temperature and shorter time, and effectively reduced preparation cost of Nd-Fe-B permanent magnet powder. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A flowchart illustrating the preparation method of Nd-Fe-B permanent magnet powder provided in an embodiment of the present invention is shown.

[0029] Figure 2 The SEM image of the magnetic powder provided in Embodiment 1 of the present invention is shown;

[0030] Figure 3 The XRD pattern of the magnetic powder provided in Embodiment 1 of the present invention is shown;

[0031] Figure 4 The hysteresis loop diagram provided in Embodiment 1 of the present invention is shown;

[0032] Figure 5 The XRD pattern of the magnetic powder provided in Embodiment 2 of the present invention is shown;

[0033] Figure 6 The hysteresis loop diagram provided in Embodiment 2 of the present invention is shown;

[0034] Figure 7 The XRD pattern of the magnetic powder provided in Comparative Example 1 of the present invention is shown.

[0035] Figure 8 The hysteresis loop diagram provided in Comparative Example 1 of the present invention is shown;

[0036] Figure 9 The XRD pattern of the magnetic powder provided in Comparative Example 2 of the present invention is shown. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0038] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0039] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0040] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0041] This invention provides a method for preparing Nd-Fe-B permanent magnet powder. The method uses iron, iron-boron alloy, and neodymium source (neodymium oxide and / or neodymium chloride) as reactants, and lanthanum hydride or cerium hydride as a reducing agent. Under vacuum heating conditions, NdFeB magnetic powder is prepared through reduction diffusion. x In the crystal structure of La x+ With H -Bonded by ionic bonds, rare earth hydride crystals exhibit superior lattice vibration and ion migration capabilities compared to metallic calcium or metallic lanthanum / cerium under the same temperature conditions. Therefore, rare earth hydrides can induce reduction reactions of neodymium oxide and / or neodymium chloride under milder vacuum heat treatment conditions. This means that at the same reaction temperature, the reaction rate using lanthanum hydride or cerium hydride as reducing agents is faster, reducing the need for reducing agents. On the other hand, the H2 generated by the decomposition of rare earth hydrides forms microbubble flows inside the reactants. The disturbance of the airflow prevents the raw material particles from agglomerating at high temperatures, ensuring complete reaction of neodymium oxide and / or neodymium chloride.

[0042] Taking lanthanum hydride as an example, the reaction pathway between lanthanum hydride and neodymium source Nd₂O₃ is: Nd₂O₃ + 2LaH₂O x →2Nd + La₂O₃ + xH₂↑; In this process, H in lanthanum hydride - Released as hydrogen gas, the byproduct La2O3, though solid, is kept loose due to its fine particle size (50-150 μm) after ball milling and the microchannels formed during H2 desorption. It can be quickly dissolved with only 1-5% dilute hydrochloric acid / glacial acetic acid. In contrast, the traditional calcium thermal reduction method requires high-temperature melting and slag removal of the generated byproduct CaO, a complex and energy-intensive process. Alternatively, large amounts of water are used to remove CaO, releasing significant heat and requiring post-treatment with a strong alkaline solution, leading to substantial costs. Furthermore, excess calcium reacts with Fe to form CaFe2 or with B to form CaB6. Removing these impurities requires acid washing, alkali washing, and secondary ball milling, increasing the number of steps and reducing the magnetic powder yield.

[0043] Furthermore, the mining process of rare earth minerals reveals their symbiotic relationship; lanthanum and cerium are not mined independently but are byproducts of the separation process in rare earth deposits such as bastnaesite, resulting in marginal costs approaching zero. This avoids the additional capital and energy investment required for the entire limestone calcination-molten salt electrolysis process necessary for calcium extraction. Moreover, the waste heat and byproduct steam from La electrolysis in the combined plant can be reused, making the use of lanthanum hydride / cerium hydride as a reducing agent even more economically viable.

[0044] The specific embodiments of the present invention are described below:

[0045] This invention provides a method for preparing Nd-Fe-B permanent magnet powder. Figure 1 A flowchart illustrating the preparation method of Nd-Fe-B permanent magnet powder provided in an embodiment of the present invention is shown, as follows: Figure 1 As shown, the method includes:

[0046] S1. Iron, iron-boron alloy, neodymium source and reducing agent rare earth hydride are mixed and ball-milled, and the resulting mixture is pressed into briquettes to obtain a billet;

[0047] In this step, the reducing agent rare earth hydride is selected from lanthanum hydride and / or cerium hydride, and the neodymium source is selected from neodymium oxide and / or neodymium chloride powder. In this step, ball milling is used to mix the raw materials required for the preparation process while activating the reaction activity. The ball-to-material ratio used for ball milling is preferably (10-20):1, the ball milling voltage is preferably 70-110 V, and the ball milling time is preferably 1-10 h. The neodymium source in the ball milling raw material is appropriately in excess to compensate for the evaporation loss of neodymium during the thermal reduction process.

[0048] In this step, the stoichiometric ratio of rare earth hydride to neodymium source is preferably 2.6~5:1. That is, if the amount of neodymium oxide and / or neodymium chloride is 1 mol, the molar amount of lanthanum hydride and / or cerium hydride is 2.6~5 times that amount, so as to ensure that the reducing agent reduces the total amount of neodymium source to elemental neodymium. The stoichiometric ratio of iron, iron-boron alloy and neodymium source is preferably 13:1:(1~3). That is, if the amount of Fe is fixed at 13 mol, the amount of iron-boron alloy (FeB) is 1 mol, and the amount of neodymium oxide and / or neodymium chloride is adjusted between 1~3 mol.

[0049] It should be noted that the reducing agent rare earth hydride used in this invention can be commercially available or obtained by hydrogen explosion of lanthanum or cerium metal. The particle size of the obtained rare earth hydride is preferably 50-150 μm. The iron is preferably commercially available nano or micro iron with a particle size of 30 nm-20 μm. The particle size of the iron-boron alloy is preferably 1-3 μm.

[0050] It should be noted that all raw materials used must be strictly dried (moisture content less than 0.1%) before ball milling to avoid oxidation caused by moisture and resulting impurities. Specifically, the neodymium source can be vacuum heat-treated at 200-400 ℃ for 3-6 h to remove residual moisture and obtain dry anhydrous neodymium oxide for ball milling.

[0051] In some embodiments, this step employs cold pressing during briquetting, with a pressure of 20-30 MPa increasing the density of the blank and the contact area between particles by 30%-50%. - It can be directly transferred to Nd through the interparticle interface 3+ This avoids the reaction dead zone caused by the obstruction of liquid Ca permeation in traditional calcium reduction.

[0052] In some embodiments, a flux comprising 5% by mass may be added during the preparation of the ingredients. The flux can further reduce the energy consumption required for the thermal reduction reaction and improve the reaction efficiency. The flux is preferably BiCl3, CaCl2, KCl and / or LaCl3.

[0053] S2. The blank is subjected to vacuum heat treatment to obtain coarse NdFeB magnetic powder material;

[0054] This step benefits from the use of rare earth hydrides as reducing agents. Without the need for additional additives, the reduction reaction can occur at a minimum temperature of 850 °C (200-300 °C lower than calcium reduction), effectively lowering the reaction initiation threshold. Furthermore, the generated byproduct La₂O₃ has a loose structure and does not hinder the normal progress of the reduction reaction. In contrast, using the traditional calcium reduction method, the generated byproduct CaO (melting point 2614 °C) easily forms a dense oxide layer on the surface of Nd particles. The encapsulation effect of CaO hinders the contact between Ca and the unreacted Nd₂O source, requiring extended holding time (typically >8 hours) or increased temperature to break down this barrier.

[0055] In this step, the preferred target temperature for vacuum heat treatment is 850-1100 ℃, the heating rate is 2-25 ℃ / min, and the holding time is 10 min-6 h. Compared with calcium thermal reduction, these reaction conditions reduce both the reaction temperature and reaction time, thereby increasing the production capacity per unit time, reducing the preparation cost, and fundamentally solving the problem of byproduct obstacles.

[0056] S3. After crushing the crude NdFeB magnetic powder material, it is transferred to a washing liquid to clean it until the non-magnetic impurities remaining in the solid phase are removed, thereby obtaining the NdFeB magnetic powder.

[0057] In this step, the crude NdFeB magnetic powder material obtained by heat treatment contains almost no Fe / B byproducts, so no additional impurity removal process is required. The crude NdFeB magnetic powder material obtained after heat treatment only needs to be crushed (no larger than 100 mesh), placed in a washing solution, and washed to remove lanthanum / cerium oxides.

[0058] In specific implementation, the cleaning process includes: sequentially using acidic washing solution, deionized water and ethanol solution to perform multi-step cleaning on the crude NdFeB magnetic powder; wherein, the acidic washing solution can be selected from hydrochloric acid solution or glacial acetic acid solution, with a concentration of 1-5%.

[0059] To enable those skilled in the art to more clearly understand the present invention, the following embodiments will be used to describe in detail the preparation method of Nd-Fe-B permanent magnet powder according to the present invention.

[0060] Example 1

[0061] Ball milling treatment: Weigh 2.8954 g iron powder, 0.2798 g iron-boron alloy, 2.0045 g neodymium oxide, and 3.3885 g cerium hydride (the molar ratio of cerium hydride to neodymium oxide is 4, and the molar ratio of iron, iron-boron alloy, and neodymium oxide is 13:1:1.5). Add grinding balls at a ball-to-material ratio of 20:1, place the mixture in a ball mill, and mill for 3 hours at 110 V. Every 1.5 hours, the sample should be ground in a glove box to prevent cold welding from causing uneven grinding of the powder.

[0062] Pressing: Under a protective atmosphere, the grinding powder is taken out and placed in a mold to be cold-pressed into a blank. The pressing pressure is 30 MPa.

[0063] Heat treatment: The green blank is placed into a covered stainless steel crucible, the crucible is sealed with a lid and placed in a heat treatment furnace. Under argon protection, the temperature is increased to 900 ℃ at a heating rate of 10 ℃ / min and held for 3 h. Then it is air-cooled to room temperature to obtain crude NdFeB magnetic powder material.

[0064] Post-processing: The coarse NdFeB magnetic powder material is crushed, and the obtained powder is washed with glacial acetic acid solution, then washed with deionized water, and finally rinsed three times with alcohol. The washed powder is placed in a vacuum drying oven and dried to obtain high-purity NdFeB magnetic powder.

[0065] It should be noted that the entire process of weighing, sampling, pressing, and heat treatment is carried out in an argon-filled glove box. When used in industrial production, the washed solution can be purified to recover rare earth elements, further reducing production costs.

[0066] Figure 2 The SEM image of the magnetic powder provided in Embodiment 1 of the present invention is shown. Figure 3 The XRD pattern of the magnetic powder provided in Embodiment 1 of the present invention is shown. Figure 4 The hysteresis loop spectrum provided in Embodiment 1 of the present invention is shown. As can be seen from the XRD pattern combined with the hysteresis loop spectrum, Neodymium iron boron single phase can be successfully prepared in Embodiment 1 using cerium hydride as a reducing agent under the assistance of high-energy ball milling.

[0067] Example 2

[0068] Ball milling treatment: Weigh 3.4402 g iron powder, 0.3102 g iron-boron alloy, 2.3333 g neodymium oxide, and 3.9164 g lanthanum hydride (the molar ratio of lanthanum hydride to neodymium oxide is 4, and the molar ratio of iron, iron-boron alloy, and neodymium oxide is 13:1:1.5). Add grinding balls at a ball-to-material ratio of 20:1, place in a ball mill, and mill for 3 hours at 110 V. Every 1.5 hours, the sample needs to be ground in a glove box to prevent cold welding from causing uneven grinding of powder.

[0069] Pressing: Under a protective atmosphere, the grinding powder is taken out and placed in a mold to be cold-pressed into a blank. The pressing pressure is 30 MPa.

[0070] Heat treatment: The green blank is placed in a covered stainless steel crucible, the crucible is sealed with a lid and placed in a vacuum tube furnace for vacuum heat treatment. The temperature is increased to 950 ℃ at a heating rate of 10 ℃ / min and held for 1 h. Then it is air-cooled to room temperature to obtain crude NdFeB magnetic powder material.

[0071] Post-processing: The coarse NdFeB magnetic powder material was crushed, and the obtained powder was washed with glacial acetic acid solution, then washed with deionized water, and finally rinsed three times with alcohol. The washed powder was placed in a vacuum drying oven and dried to obtain high-purity NdFeB magnetic powder. The cleaning process involved alternating acid washing and water washing.

[0072] It should be noted that the entire process of weighing, sampling, pressing, and heat treatment is carried out in an argon-filled glove box. When used in industrial production, the washed solution can be purified to recover rare earth elements, further reducing production costs.

[0073] Figure 5 The XRD pattern of the magnetic powder provided in Embodiment 2 of the present invention is shown. Figure 6 The hysteresis loop spectrum provided in Example 2 of the present invention is shown. As can be seen from the XRD pattern combined with the hysteresis loop spectrum, in Example 2, lanthanum hydride as a reducing agent can be successfully prepared as a single phase of neodymium iron boron under the assistance of high-energy ball milling.

[0074] Comparative Example 1

[0075] Unlike Example 1, Comparative Example 1 weighed 2.8954 g of iron powder, 0.2798 g of iron-boron alloy, 2.0045 g of neodymium oxide, and 3.3885 g of cerium hydride, mixed evenly, and directly pressed into blocks without ball milling; the rest of the process was the same as in Example 1.

[0076] Figure 7 The XRD pattern of the magnetic powder provided in Comparative Example 1 of the present invention is shown. Figure 8 The hysteresis loop spectrum provided by Comparative Example 1 of the present invention is shown. As can be seen from the XRD pattern combined with the hysteresis loop spectrum, although lanthanum hydride was used as a reducing agent in Comparative Example 1, neodymium iron boron single phase could not be successfully prepared without the assistance of high-energy ball milling.

[0077] Comparative Example 2

[0078] Unlike Example 2, in Comparative Example 1, lanthanum metal was used as a reducing agent during ball milling and mixing.

[0079] During heat treatment, the temperature for vacuum heat treatment is 1100 ℃;

[0080] The remaining process is the same as in Example 2.

[0081] Figure 9 The XRD pattern of the magnetic powder provided in Comparative Example 2 of the present invention is shown. As can be seen from the XRD pattern, Comparative Example 2 used lanthanum as a reducing agent, but because the temperature of vacuum heat treatment did not reach the temperature required for reduction, it was impossible to successfully prepare NdFeB single phase.

[0082] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0083] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0084] The present invention provides a detailed description of a method for preparing Nd-Fe-B permanent magnet powder. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for producing an Nd-Fe-B permanent magnetic powder, characterized by, The method includes: Iron, iron-boron alloy, neodymium source and reducing agent rare earth hydride are mixed and ball-milled, and the resulting mixture is then pressed into briquettes to obtain a billet. The blank is subjected to vacuum heat treatment to obtain coarse NdFeB magnetic powder material; After the crude NdFeB magnetic powder material is crushed, it is cleaned to remove the non-magnetic impurities remaining in the solid phase, and then dried to obtain the Nd-Fe-B permanent magnet powder. The reducing agent rare earth hydride is selected from lanthanum hydride and / or cerium hydride; The neodymium source is selected from neodymium oxide and / or neodymium chloride; The molar ratio of the reducing agent rare earth hydride to the neodymium source is (2.6~5):1; The molar ratio of the iron, the iron-boron alloy, and the neodymium source is 13:1:(1~3).

2. The method of producing an Nd-Fe-B permanent magnetic powder according to claim 1, characterized by, The ball-to-material ratio for ball milling is (10-20):1, and the ball milling time is 1-10 h.

3. The method of producing an Nd-Fe-B permanent magnetic powder according to claim 1, characterized by, The briquetting process is carried out by cold pressing, and the pressure used for the briquetting is 20-30 MPa.

4. The method of producing an Nd-Fe-B permanent magnetic powder according to claim 1, characterized by, The target temperature for the vacuum heat treatment is 850-1100 ℃, the heating rate is 2-25 ℃ / min, and the holding time is 10 min-6 h.

5. The method of producing an Nd-Fe-B permanent magnetic powder according to claim 1, wherein The cleaning process includes: sequentially using an acidic detergent, deionized water, and ethanol solution to perform multi-step cleaning on the crude NdFeB magnetic powder material; the acidic detergent is a hydrochloric acid solution or a glacial acetic acid solution with a concentration of 1-5%.

6. The method for preparing Nd-Fe-B permanent magnet powder according to claim 1, characterized in that, The rare earth hydrides are obtained by hydrogen explosion of lanthanum or cerium metal. The particle size of the reducing agent rare earth hydride is 50-150 μm.

7. The method for preparing Nd-Fe-B permanent magnet powder according to claim 1, characterized in that, The iron-boron alloy has a particle size of 1-3 μm; The iron has a particle size of 30 nm to 20 μm.

8. The method for preparing Nd-Fe-B permanent magnet powder according to claim 1, characterized in that, Before ball milling, the neodymium source is subjected to vacuum heat treatment at 200-400 °C for 3-6 h to remove residual moisture and obtain dry anhydrous neodymium oxide.

9. The method for preparing Nd-Fe-B permanent magnet powder according to claim 1, characterized in that, The method further includes: adding an appropriate amount of flux to the mixture, mixing it evenly, and then pressing it into a block to obtain a green body; The flux is selected from BiCl3, CaCl2, KCl and / or LaCl3.

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