Neodymium-iron-boron magnet with high magnetic stability, method for manufacturing the same, and use thereof

Abstract

The application provides a neodymium-iron-boron magnet with high magnetic stability, a manufacturing method and application thereof. The neodymium-iron-boron magnet has a three-dimensional structure, which comprises a length direction, a pressing direction and an orientation direction; and the orientation deviation angle of the neodymium-iron-boron magnet is less than or equal to 1°. The neodymium-iron-boron magnet and the manufacturing method can effectively improve the magnetic stability of the magnet.

Description

Technical Field

[0001] This invention relates to the field of rare earth permanent magnet technology, specifically to a neodymium iron boron magnet with high magnetic stability, its manufacturing method, and its application. Background Technology

[0002] Neodymium iron boron (NdFeB) permanent magnets are widely used in various technological fields due to their excellent magnetic properties, such as wind power, home appliances, elevators, and EPS (expanded power supply). In large-scale equipment, NdFeB magnets are bulky, and the corresponding magnetic performance requirements and the consistency of the orientation angle are relatively low. However, with the continuous development and expansion of the electric vehicle industry, the use of NdFeB permanent magnets is increasing year by year. As the electric vehicle industry tends towards smaller and lighter designs, reducing the weight of electric vehicles and increasing their mobility, the size of NdFeB permanent magnets used in electric vehicles is becoming smaller, but the requirements for the stability of their magnetic properties are becoming increasingly stringent. During the magnetic orientation forming process of permanent magnets, the product orientation direction and the orientation magnetic field direction are not parallel, resulting in an orientation angle; or, during product delivery, improper alignment during clamping can cause an orientation angle between the product's geometric symmetry axis and the product's magnetic axis. In other words, the orientation angle of a permanent magnet refers to the angle between the final magnetization vector direction and the orientation direction. Due to the existence of the orientation angle, a magnetic field is generated in the non-magnetized direction of the magnet, forming a stray magnetic field.

[0003] With the increasing application of permanent magnets, orientation angle has become a crucial factor affecting the performance of precision magnetic devices. Improving the consistency of product orientation angle and enhancing product stability is therefore urgently needed. Summary of the Invention

[0004] The purpose of this invention is to provide a neodymium iron boron magnet with high magnetic stability, its manufacturing method, and its application.

[0005] The technical solution of the present invention is as follows:

[0006] A neodymium iron boron magnet, wherein the neodymium iron boron magnet has a three-dimensional structure, such as Figure 2 As shown, the three-dimensional structure includes a length direction, a pressing direction, and an orientation direction; the orientation deflection angle of the neodymium iron boron magnet is less than or equal to 1°.

[0007] It should be noted that, in this invention, the orientation deflection angle of the neodymium iron boron magnet specifically refers to the measurement of magnetic flux values ​​in three directions: product length, pressing, and orientation. The length direction, pressing direction, and orientation direction are mutually orthogonal. The vector sum of the three directions is taken to obtain the total magnetic flux value and the final magnetization vector direction of the neodymium iron boron magnet. Then, the angle between the final magnetization vector direction and the orientation direction of the neodymium iron boron magnet is measured and defined as the orientation deflection angle.

[0008] According to an embodiment of the present invention, the neodymium iron boron magnet comprises the following components:

[0009] 25-35 wt% R, where R is selected from one or more of Nd, Pr, Ce, Dy or Tb;

[0010] 0.8-1.5 wt% B;

[0011] 1-5 wt% M, selected from one or more of Ti, Ga, Cu, Al, Zr, Nb, Mn or Ni; the remainder is Fe and unavoidable impurities.

[0012] According to an embodiment of the present invention, the impurities in the neodymium iron boron magnet include at least one of the following elements:

[0013] C, the content of which is less than 700 ppm, preferably 100-650 ppm;

[0014] O, the content of which is less than 1000 ppm, preferably 100-950 ppm;

[0015] N, the content of which is less than 900 ppm, preferably 100-650 ppm.

[0016] The present invention also provides a method for manufacturing the above-mentioned neodymium iron boron magnet, the method comprising the following steps: a rapid solidification sheet process, a powder preparation process, a vertical pressing and forming process, and a sintering process, to prepare the neodymium iron boron magnet.

[0017] According to an embodiment of the present invention, the rapid solidification sheet process specifically includes: adding the required raw materials according to the stoichiometric coefficients of the NdFeB magnet components, fully melting them into an alloy steel liquid under a vacuum or inert gas atmosphere, then rapidly cooling to form an alloy sheet, and then undergoing a second cooling to obtain the rapid solidification sheet. The rapid solidification sheet can suppress the production of α-Fe, which is key to obtaining high-performance NdFeB permanent magnets.

[0018] According to an embodiment of the present invention, the rapid-setting sheet process can be carried out using methods known in the art, as long as the rapid-setting sheet can be obtained.

[0019] For example, the rapid cooling condition is a cooling rate of 15-20°C / min.

[0020] For example, the secondary cooling is performed by injecting cryogenic argon gas.

[0021] According to an embodiment of the present invention, the powder preparation process specifically includes: grinding the rapidly solidifying sheet into neodymium iron boron powder by hydrogen embrittlement and air jet milling. Through the powder preparation process of the present invention, the obtained neodymium iron boron powder has a smaller average particle size, making it easier to achieve better orientation and improving the magnetic properties of neodymium iron boron magnets.

[0022] Preferably, the average particle size (SMD) of the neodymium iron boron powder is 1-5 μm, more preferably 2-4 μm, for example 3.0 ± 0.2 μm.

[0023] According to an embodiment of the present invention, the gas used in the air jet mill is selected from an inert gas. Preferably, the inert gas is selected from nitrogen, argon, helium, etc.

[0024] Preferably, the oxygen content in the inert gas is no more than 30 ppm, which can prevent the NdFeB powder from being oxidized during the air jet milling process, thereby reducing the magnetic properties of the final product.

[0025] According to an embodiment of the present invention, the inert gas, after being ground in an air jet mill, can be recycled after filtration. Preferably, the inert gas, after being ground in an air jet mill, is filtered to obtain recovered powder.

[0026] Preferably, the recycled powder is rare earth-rich powder. More preferably, the particle size of the rare earth-rich powder is between 0.1 μm and 2 μm.

[0027] According to an embodiment of the present invention, the vertical pressing process specifically includes: under the action of a magnetic field, the neodymium iron boron powder is vertically pressed to obtain a compact.

[0028] Preferably, the magnetic field can be a magnetic field known in the art, such as a 2T magnetic field.

[0029] Preferably, the ratio of the dimension in the orientation direction to the dimension in the length direction of the pressed blank is 1-5, for example, 2-4, 2.5-3.2, or 2.5-3.0. When the dimension in the length direction of the pressed blank is too small, the mold cavity of the pressing mold needs to withstand relatively large pressure, which requires high-quality mold materials and is prone to physical damage, making it unsuitable for mass production.

[0030] The inventors discovered that when the ratio of the orientation direction dimension to the length direction dimension of the NdFeB magnet blank is 2-4, preferably 2.5-3.2, the orientation deflection angle of the NdFeB magnet can be controlled within 1°. Therefore, in this invention, by strictly controlling the dimensions of the NdFeB magnet blank, the numerical value of the orientation deflection angle of the NdFeB magnet can be controlled.

[0031] For example, the length dimension of the pressed blank is 10-20mm, preferably 10mm-15mm.

[0032] For example, the dimension of the pressing direction of the pressed blank is 45-55mm.

[0033] According to an embodiment of the present invention, the vertical pressing process further includes performing an isostatic pressing operation after pressing. The isostatic pressing operation increases the density of the NdFeB magnets, further reduces the gaps between the NdFeB powders within the compact, and reduces the differences between the powders within the NdFeB compact, thus preparing for uniform shrinkage of the NdFeB product during subsequent sintering and hardening.

[0034] Preferably, the isostatic pressure is 100 MPa to 300 MPa.

[0035] According to an embodiment of the present invention, additives need to be added to the neodymium iron boron powder before vertical pressing.

[0036] Preferably, the additive includes a lubricant and / or an antioxidant.

[0037] Preferably, the additive is stirred evenly using methods known in the art. For example, a rotary stirrer is used to thoroughly stir the NdFeB powder and the additive to ensure their uniformity. For instance, a thin film formed by the additive is uniformly coated onto the surface of the NdFeB powder. This film not only prevents oxidation of the NdFeB powder but also ensures good flowability, thereby improving the magnetization orientation of the pressed compact.

[0038] According to an embodiment of the present invention, the sintering process specifically includes: sintering the pressed blank at high temperature, tempering at low temperature, and cooling to obtain neodymium iron boron magnets.

[0039] Preferably, the conditions for high-temperature sintering include: a vacuum degree of 1.0 × 10⁻⁶. -3 Below Pa, the sintering temperature is 1000℃-1100℃, and the sintering time is 6-12h. More preferably, to ensure uniform heating of the green body, a heating process is required before high-temperature sintering. Exemplarily, the heating rate is 1-10℃ / min, preferably 1-5℃ / min.

[0040] Preferably, the temperature of the low-temperature tempering is 450℃-600℃.

[0041] Preferably, the cooling rate is 5-15°C / min, and more preferably 6-10°C / min.

[0042] According to an embodiment of the present invention, both the vertical pressing and sintering processes are performed under a low-oxygen atmosphere. Preferably, the low-oxygen atmosphere refers to an oxygen content of less than 50 ppm. By controlling the low-oxygen atmosphere in the vertical pressing and sintering processes, localized oxidation of the compact surface is prevented, thus avoiding interference with the uniformity of compact shrinkage.

[0043] Preferably, a sintering protective material is also added during the sintering process. Preferably, the sintering protective material is evenly distributed on the outer side of the billet, for example, coated on the outer surface of the billet or coated in the cavity of the sintering box.

[0044] The inventors discovered that the sintering protective material can not only reduce the influence of impurity elements (such as C, O, N, etc.) in the sintering furnace atmosphere on the magnet, but also effectively eliminate the inconsistent shrinkage of NdFeB magnets during the sintering process, so that the sintered NdFeB magnets have high shape consistency and performance consistency, thereby obtaining NdFeB products with high magnetic stability.

[0045] According to an embodiment of the present invention, the sintering protective material comprises rare earth-rich powder.

[0046] Preferably, in the rare earth-rich powder, the rare earth elements are selected from Nd, Pr, La, and Ce, and the content of the rare earth elements is greater than 80%.

[0047] Preferably, the particle size of the rare earth-rich powder is not higher than 2 μm, and more preferably 0.1-2 μm.

[0048] Exemplarily, the green body is sintered in a sintering box, and a protective film is coated on the inner wall of the sintering box, the protective film comprising the sintering protective material. Exemplarily, the protective film is prepared using methods known in the art, such as mixing the rare earth-rich powder with an organic solvent to obtain a slurry, coating the slurry onto the inner surface of the sintering box, and removing the organic solvent to obtain the protective film. Exemplarily, the organic solvent is selected from at least one of anhydrous ethanol, glycerol, and ethylene glycol. Exemplarily, in the slurry, the mass ratio of the rare earth-rich powder to the organic solvent is (27-40):(60-73).

[0049] For example, the rare earth-rich powder includes the recycled powder described in this invention.

[0050] For example, the sintering box is selected from graphite boxes. Since graphite is not easily deformed at high temperatures, it can ensure that the green body will not deform during the sintering process.

[0051] The present invention also provides neodymium iron boron magnets manufactured by the above-described manufacturing method.

[0052] The present invention also provides the application of the above-mentioned neodymium iron boron magnet in the field of electric vehicles.

[0053] The beneficial effects of this invention are:

[0054] The orientation deflection angle of the neodymium iron boron magnet provided by this invention is less than or equal to 1°. The neodymium iron boron magnet provided by this invention can effectively improve the magnetic stability of the magnet.

[0055] The method for manufacturing NdFeB magnets provided by this invention, by adding sintering protective materials during sintering, can not only reduce the influence of impurity elements (such as C, O, N, etc.) in the sintering furnace atmosphere on the magnets, but also effectively eliminate the inconsistent shrinkage of NdFeB magnets during sintering, so that the sintered NdFeB magnets have high shape and performance consistency, thereby obtaining NdFeB products with high magnetic stability.

[0056] In the manufacturing process of this invention, controlling the ratio of the orientation direction dimension to the length direction dimension of the pressed blank to be 1-5, preferably 2-4, is more suitable for mass production. Attached Figure Description

[0057] Figure 1 This is a schematic diagram showing the sampling location in the material box; A - Material box; B - Sampling compact;

[0058] Figure 2 This is a schematic diagram for measuring the orientation degree of a cube product. Detailed Implementation

[0059] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0060] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0061] The inventors discovered that, after the sintering process, the pressed blanks located at the corners of the graphite box are most prone to exhibiting excessively large orientation deviation angles. Therefore, in the following embodiments, only four pressed blanks placed at the corners of the graphite box were tested. The position of the pressed blank B used for testing in box A is as follows: Figure 1 The inventors also discovered that the magnet portion located at the corners of each pressed blank is most prone to exhibiting excessively large orientation deviation angles. Therefore, in this invention, the orientation deviation angle is obtained through the following testing method:

[0062] 1. The magnets located at the corners of the graphite box are used as the magnets to be tested. In the following embodiment, there are 5 layers in the graphite box. Four magnets are taken from the four corners of each layer, and a total of 20 magnets are used as the magnets to be tested.

[0063] 2. Processing test samples: The above-mentioned magnets to be tested are processed into 1 segment along their length, 5 segments along their pressing direction, and 10 segments along their orientation direction, for a total of 50 samples.

[0064] 3. Testing: Take a sample from the magnet to be tested, such as... Figure 2 The magnetic flux of four samples (numbered 1-4) shown in the diagram was tested. The magnetic flux of each sample was measured along its length, pressing direction, and orientation direction. The vector sum of these three directions was taken to obtain the actual magnetic flux value for each sample. The formula cosθ = magnetic flux in the orientation direction / actual magnetic flux value was used, where θ represents the orientation deflection angle between the orientation direction and the direction of the total magnetic flux vector of the magnet. After measuring the orientation deflection angles of the four samples, the maximum value was taken as the orientation deflection angle value of the magnet under test. The orientation deflection angles of a total of 20 magnets were measured, and the maximum, minimum, and average orientation deflection angles were recorded.

[0065] Example 1

[0066] (1) Rapid solidification sheet process: Prepare the raw materials for neodymium iron boron magnets according to Table 1, fully melt the raw materials into alloy steel liquid under nitrogen atmosphere, and prepare alloy sheets by strip casting process. After the alloy sheets are cooled and removed by the quenching roller, they are sprayed with low temperature argon gas for secondary cooling to fully cool the alloy sheets and obtain rapid solidification sheets.

[0067] Table 1

[0068] serial number Pr Nd Dy B Co Cu Ga Al Zr Fe and impurity elements Example 1 - 29 0.5 0.9 - 0.3 0.4 0.2 0.4 margin

[0069] (2) Powdering process: The rapid-condensing flakes obtained in step (1) are coarsely crushed using a hydrogen embrittlement process to obtain powder. 0.1 wt% zinc stearate is added to the powder as a lubricant, and the mixture is stirred for 60 minutes. After stirring, the material is finely crushed in a fluidized bed jet mill using nitrogen as the grinding gas to obtain iron-boron powder with a target particle size SMD = 2.5 μm. Before grinding in the jet mill, the oxygen content in the mill is monitored. Nitrogen gas with a purity of 99.9% is introduced and purged for 5 minutes to ensure the oxygen content in the jet mill is <30 ppm.

[0070] (3) Vertical pressing molding process: Add 0.2wt% zinc stearate as a lubricant to the neodymium iron boron powder obtained in step (2). After mixing thoroughly, the powder is vertically pressed under a magnetic field of 2T to obtain a compact.

[0071] During the vertical pressing process, the oxygen content in the pressing gas atmosphere is controlled to be below 50 ppm. The specific dimensions of the pressed preform are as follows: length, pressing direction, and orientation direction dimensions are 13 mm, 50 mm, and 50 mm, respectively; after pressing, the density of the preform is controlled to be 3.0-4.0 g / cm³. 3 The compact is then subjected to an isostatic pressing process at a pressure of 200 MPa until its density reaches 4.6 g / cm³. 3The isostatic pressing process is then completed.

[0072] (4) Sintering process: Argon gas is introduced into the sintering furnace to replace the ambient atmosphere and ensure a low-oxygen environment inside the furnace. The pressed billets are placed in a graphite sintering box, with 5 layers of pressed billets placed inside the furnace. Sintering and hardening are then performed under a vacuum atmosphere. The vacuum degree of the furnace is 1.0*10⁻⁶. -3 Below Pa, the sintering temperature is controlled at 1020℃. To ensure uniform shrinkage of the NdFeB magnet, the heating rate is controlled at 5℃ / min to prevent uneven heating in certain areas. After sintering and hardening, a low-temperature tempering treatment is performed at 450℃. After sintering, the NdFeB magnet needs to be cooled. It is removed after cooling until the temperature is below 50℃ to ensure a small temperature difference between the surface and internal parts of the NdFeB magnet.

[0073] Five layers of pressed blanks are placed in a graphite cassette. Four pressed blanks are taken from the corners of each graphite cassette layer. The position of sample pressed blank B in cassette A is shown below. Figure 1 Each pressed blank is processed into a square product according to its dimensions. The specific dimensions of the square product are 10mm*10mm*5mm. The blank is machined into 10mm sections along its 13mm length, and into 5 segments at 10mm intervals along its 50mm length. Finally, it is machined into 10 segments at 5mm intervals along its 50mm orientation (oriented arrow). The specific processing method is as follows... Figure 2 (The arrow direction represents the orientation direction of the NdFeB magnet). A total of 20 blanks were processed into square products, and 4 square products were taken from each blank, for a total of 80 square products to measure the orientation degree of the products.

[0074] The position of sampled compact B in the material box is as follows: Figure 1 As shown; the specific processing method is as follows: Figure 2 As shown, where Figure 2 The arrows in the image indicate the orientation direction of the neodymium iron boron magnet:

[0075] For each pressed blank, four square products from the top corners are taken for orientation measurement, such as... Figure 2 At positions 1-4 shown, the magnetic flux of the measuring product is measured in three directions: length, compression, and orientation. The vector sum of the three directions is taken to obtain the magnetic flux value and direction of the square product. Then, the angle between the magnetic flux value in the orientation direction and the total magnetic flux value of the square product is obtained by using the magnetic flux value in the orientation direction and the total magnetic flux value of the square product.

[0076] Twenty blanks of neodymium iron boron magnets of this specification and size were taken. Four square products were made from each blank according to the requirements, for a total of 80 pieces of data. The test results showed that the average orientation deflection angle of the neodymium iron boron magnet in Example 1 was 1.00°, the maximum value was 1.22°, the minimum value was 0.77°, and the variance was 0.111.

[0077] Example 2

[0078] The method for preparing the magnet in this embodiment is the same as that in Embodiment 1, except that the dimensions of the pressed blank in the length direction, pressing direction, and orientation direction are 13mm, 50mm, and 45mm, respectively.

[0079] The sampling and testing methods for the neodymium iron boron magnets in Example 2 are the same as those in Example 1. The tests show that the average orientation deflection angle of the neodymium iron boron magnets in Example 2 is 0.96°, the maximum value is 1.19°, the minimum value is 0.69°, and the variance is 0.109.

[0080] Example 3

[0081] The method for preparing the magnet in this embodiment is the same as that in Embodiment 1, except that the dimensions of the pressed blank in the length direction, pressing direction, and orientation direction are 13mm, 50mm, and 40mm, respectively.

[0082] The sampling and testing methods for the neodymium iron boron magnets in Example 3 are the same as those in Example 1. The test results show that the average orientation deflection angle of the neodymium iron boron magnets in Example 2 is 0.93°, the maximum value is 1.00°, the minimum value is 0.75°, and the variance is 0.055.

[0083] Example 4

[0084] The method for preparing the magnet in this embodiment is the same as that in Embodiment 1, except that the dimensions of the pressed blank in the length direction, pressing direction, and orientation direction are 13mm, 50mm, and 35mm, respectively.

[0085] The specific sampling method is the same as in Example 1.

[0086] The sampling and testing methods for the neodymium iron boron magnets in Example 4 are the same as those in Example 1. The test results show that the average orientation deflection angle of the neodymium iron boron magnets in Example 2 is 0.87°, the maximum value is 0.98°, the minimum value is 0.7°, and the variance is 0.079.

[0087] Comparing the orientation angle data of Examples 1-4 above, it can be seen that as the size of the magnet orientation direction decreases, the average value of the orientation angle decreases. Therefore, reducing the size of the magnet orientation direction can improve the magnetic properties of NdFeB magnets. During the preparation process, when the ratio of the size of the orientation direction to the length direction of the pressed blank is controlled to be 2-4, the average value of the orientation angle of the NdFeB magnets prepared in the same graphite box can be within 1°; when the ratio of the size of the orientation direction to the length direction of the pressed blank is 2.5-3.2, the maximum value of the orientation angle of the NdFeB magnets prepared in the same graphite box can be within 1°.

[0088] Example 5

[0089] The method for preparing the magnet in this embodiment is the same as that in embodiment 2. The difference is that in step (4), after coating a protective film on the inner wall of the graphite box, the pressed blank is placed into the graphite box.

[0090] The coating method for the protective film is as follows:

[0091] a. The inner wall of the graphite box is cleaned by shot blasting to remove surface impurities;

[0092] b. Preparation of slurry: The rare earth-rich powder is mixed with ethanol and glycerol in an equal volume ratio of 1:1 and then mixed with an organic solvent in a mass ratio of 30:70 to obtain the slurry;

[0093] c. Preparation of protective film: The slurry is coated on the inner wall of the graphite box with a thickness of 100 μm. After the organic solvent dries, the protective film is obtained.

[0094] The coating process in step c above is carried out in a nitrogen protective atmosphere;

[0095] Protective films for Examples 5-1 to 5-7 were prepared using the rare earth-rich powders listed in Table 2, and neodymium iron boron magnets for Examples 5-1 to 5-7 were obtained after processing. The sampling and testing methods for the neodymium iron boron magnets in Example 5 were the same as those in Example 1. The average, maximum, and minimum values ​​of the orientation deflection angles of the samples were obtained and recorded in Table 2.

[0096] The magnets from Examples 2 and 5 were tested for C, O, and N content using a high-frequency inductively coupled plasma atomic emission spectrometer. Specifically, the O content was determined using a gas analysis device based on gas dissolution-infrared absorption, the N content using a gas analysis device based on gas dissolution-thermal conduction, and the C content using a gas analysis device based on combustion-infrared absorption. The C, O, and N contents of the magnets from Examples 2 and 5 are detailed in Table 2.

[0097] Table 2

[0098]

[0099] The data in Table 2 show that by coating the inner wall of the graphite cartridge with a protective film, the orientation angle of all magnets in the graphite cartridge can be reduced while keeping the length and pressing dimensions of the NdFeB blank unchanged. When the rare earth element content in the coating slurry is >80% and the average particle size of the powder is 0.1-2μm, the maximum orientation angle of all magnets in the graphite cartridge can be kept within 1°.

[0100] In addition, the protective film can also adsorb impurity elements such as C, O, and N in the sintering furnace atmosphere, effectively reducing the risk of impurity elements entering the NdFeB magnet, thereby reducing the impurity content in the NdFeB magnet. The resulting NdFeB magnet has high consistency in shape and performance, and high magnetic stability.

[0101] While keeping the dimensions of the NdFeB magnet in the length and pressing directions unchanged, reducing the dimension in the orientation direction of the magnet will further reduce the orientation deflection angle of the NdFeB magnet. However, reducing the dimension in the orientation direction increases the processing requirements of the pressing mold, and it cannot be reduced indefinitely, otherwise it will lose its practical production value.

[0102] Meanwhile, the present invention found that the powder recovered after air jet milling is all rare earth rich powder, with a rare earth content of more than 80% and a particle size of less than 2μm, which is very suitable as a protective film for the inner wall of the graphite box.

[0103] The recycled powder generated by the air jet mill is used as rare earth-rich powder to prepare a slurry, which eliminates safety hazards and solves the problem of environmental pollution.

[0104] The exemplary embodiments of the present invention have been described above. However, the scope of protection of this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for manufacturing neodymium iron boron magnets, characterized in that, The manufacturing method includes the following steps: rapid solidification sheeting process, powder preparation process, vertical pressing molding process and sintering process, to prepare the neodymium iron boron magnet; The vertical pressing process specifically includes: under the action of a magnetic field, neodymium iron boron powder is vertically pressed to obtain a compact; the ratio of the dimension in the orientation direction to the dimension in the length direction of the compact is 2.5-3.2; In the sintering process, a sintering protective material is also added; the sintering protective material is evenly distributed on the outer side of the green body; the sintering protective material includes rare earth-rich powder; in the rare earth-rich powder, the rare earth elements are selected from Nd, Pr, La, and Ce; The neodymium iron boron magnet has a three-dimensional structure, which includes a length direction, a pressing direction, and an orientation direction; the orientation angle of the neodymium iron boron magnet is less than or equal to 1°. The impurities in the neodymium iron boron magnet include: C, its content is less than 700 ppm; O, its content is less than 1000 ppm; N, its content is less than 900 ppm.

2. The manufacturing method according to claim 1, characterized in that, The neodymium iron boron magnet comprises the following components: 25-35 wt% R, where R is selected from one or more of Nd, Pr, Ce, Dy or Tb; 0.8-1.5wt% B; 1-5 wt% M, selected from one or more of Ti, Ga, Cu, Al, Zr, Nb, Mn or Ni; the remainder is Fe and unavoidable impurities.

3. The manufacturing method according to claim 1, characterized in that, The impurities in the neodymium iron boron magnet include: The C content is 100-650 ppm; The content of O is 100-950 ppm; The nitrogen content is 100-650 ppm.

4. The manufacturing method according to claim 1, characterized in that, The rapid solidification sheet process specifically includes: adding the required raw materials according to the stoichiometric coefficients of the NdFeB magnet components, fully melting them into alloy steel liquid under vacuum or inert gas atmosphere, then rapidly cooling them to form alloy sheets, and then undergoing secondary cooling to obtain the rapid solidification sheet.

5. The manufacturing method according to claim 1, characterized in that, The powder preparation process specifically includes: grinding the rapid-condensing flakes through hydrogen embrittlement and air jet milling to obtain NdFeB powder; The average particle size of the neodymium iron boron powder is 1-5 μm; The gas used in the air jet mill is selected from inert gases; the inert gases are selected from nitrogen, argon, and helium. The oxygen content in the inert gas is no more than 30 ppm; The inert gas is filtered and recycled after being ground in an air jet mill.

6. The manufacturing method according to claim 5, characterized in that, The average particle size of the neodymium iron boron powder is 2-4 μm.

7. The manufacturing method according to claim 1, characterized in that, The ratio of the dimension in the orientation direction to the dimension in the length direction of the pressed blank is 2.5-3.

8. The manufacturing method according to claim 1, characterized in that, The vertical pressing process further includes: performing isostatic pressing after pressing is completed; The isostatic pressure is 100 MPa-300 MPa.

9. The manufacturing method according to claim 1, characterized in that, Additives are added to the neodymium iron boron powder before vertical pressing. The additives include lubricants and / or antioxidants.

10. The manufacturing method according to claim 1, characterized in that, The sintering process specifically includes: sintering the pressed blank at high temperature, tempering at low temperature, and cooling it to obtain neodymium iron boron magnets; The conditions for the high-temperature sintering include: a vacuum degree of 1.0 × 10⁻⁶. -3 For Pa below 1000℃, the sintering temperature is 1000℃-1100℃, and the sintering time is 6-12h. The temperature for the low-temperature tempering is 450℃-600℃; The cooling rate is 5-15℃ / min; Both the vertical pressing and sintering processes are carried out in a low-oxygen atmosphere; the low-oxygen atmosphere refers to an oxygen content of less than 50 ppm.

11. The manufacturing method according to claim 10, characterized in that, The cooling rate is 6-10°C / min.

12. The manufacturing method according to claim 1, characterized in that, The rare earth-rich powder contains more than 80% rare earth elements. The particle size of the rare earth-rich powder is no higher than 2 μm; The sintering protective material is coated on the outer surface of the billet or in the cavity of the sintering box.

13. The neodymium iron boron magnet obtained by the manufacturing method according to any one of claims 1-12, characterized in that, The neodymium iron boron magnet has a three-dimensional structure, which includes a length direction, a pressing direction, and an orientation direction; the orientation angle of the neodymium iron boron magnet is less than or equal to 1°. The impurities in the neodymium iron boron magnet include: C, its content is less than 700 ppm; O, its content is less than 1000 ppm; N, its content is less than 900 ppm.

14. The application of the neodymium iron boron magnet of claim 13 in the field of electric vehicles.

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