Neodymium-iron-boron sintered magnet and preparation method and application thereof

Abstract

The invention provides a neodymium iron boron sintered magnet and a preparation method and application thereof. The neodymium iron boron sintered magnet comprises the following components: R, wherein the mass content of R is 28-33wt%; r comprises Nd and Ce, and optionally comprises or does not comprise at least one of Pr, Dy, Tb, Ho and Gd; m, wherein the mass content of the M is 1.5-2.5 wt%; b, the mass content of the B is 0.95 to 1.05 wt%; the mass content of the Ti ranges from 0.1 wt% to 0.25 wt%; fe is the balance; in the neodymium iron boron sintered magnet, the mass content of Ce is 0.3-5 wt%. By accurately controlling the main alloy element components, the generation of a soft magnetic phase in main phase grains is avoided; and meanwhile, the element components of the auxiliary alloy are optimized, and the dosage ratio of the main alloy to the auxiliary alloy is adjusted, so that main phase grains are refined, a fine titanium-rich phase which is dispersed and distributed is formed in a grain boundary phase, and the magnetic performance of the product is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth sintered magnet preparation, and in particular relates to a neodymium iron boron sintered magnet and a preparation method and application thereof. Background Art

[0002] In modern industry and technology, high-performance permanent magnet materials play an indispensable role. Neodymium iron boron (Nd-Fe-B) sintered magnets are one of the most widely used rare earth permanent magnet materials due to their high magnetic energy product and high coercivity. They are widely used in many fields such as electronic equipment, motors, generators, etc., and are crucial to improving the efficiency and performance of these devices.

[0003] However, there are some problems in the preparation process of traditional NdFeB sintered magnets, such as insufficient control of grain boundary phase and unstable magnetic properties, which limit their potential in high-performance applications. To solve these problems, researchers have been exploring new preparation methods and material components to improve the magnetic properties and reliability of magnets. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a new type of NdFeB sintered magnet and its preparation method and application, aiming to achieve fine control of the microstructure of the magnet by precisely controlling the mass content of rare earth elements (R), boron (B), titanium (Ti) and other alloy elements (M), and optimizing the ratio of main alloy powder and auxiliary alloy powder, thereby significantly improving the magnetic properties of the magnet.

[0005] The technical solution provided by the present invention is as follows: A neodymium iron boron sintered magnet comprising the following components: R, the mass content of R is 28-33wt%; R includes Nd and Ce, and optionally includes or excludes at least one of Pr, Dy, Tb, Ho, and Gd; The mass content of M, M is 1.5-2.5wt%; M is selected from at least one of Co, Cu, Ga, Al, Mn, Nb, W, Hf, and Cr; B, the mass content of B is 0.95-1.05wt%; Ti, the mass content of Ti is 0.1-0.25wt%; Fe is the balance; In the NdFeB sintered magnet, the mass content of Ce is 0.3-5wt%.

[0006] According to an embodiment of the present invention, in the NdFeB sintered magnet, the mass content of R is preferably 29-32wt%, for example 30wt%.

[0007] According to an embodiment of the present invention, in the NdFeB sintered magnet, the mass content of M is, for example, 2 wt %.

[0008] According to an embodiment of the present invention, in the NdFeB sintered magnet, the mass content of B is preferably 0.98-1.01 wt%, for example, 1 wt%.

[0009] According to an embodiment of the present invention, in the NdFeB sintered magnet, the mass content of Ti is preferably 0.15-0.2wt%, for example 0.18wt%.

[0010] According to an embodiment of the present invention, in the NdFeB sintered magnet, the mass content of Ce is preferably 1.5-2.5wt%, for example, 2wt%.

[0011] According to an embodiment of the present invention, in the NdFeB sintered magnet, the mass ratio of Ti to Ce is 0.15-0.2:1.5-2.5, for example, 0.18:2.

[0012] According to an embodiment of the present invention, the NdFeB sintered magnet is prepared by mixing a main alloy powder and an auxiliary alloy powder, pressing and molding, sintering the mixture, and then subjecting the mixture to composite diffusion.

[0013] According to an embodiment of the present invention, the main alloy powder includes at least Ti and optionally Ce, wherein the mass content c' of Ti is 0.1-0.2%, for example 0.15wt%; the mass content a' of Ce is not more than 4wt%, preferably 0-2.5wt%, for example 1.55wt%.

[0014] According to an embodiment of the present invention, the auxiliary alloy powder includes at least Ti and Ce, wherein the mass content c" of Ti is 0.2-0.4%, for example, 0.25wt%, 0.3wt%, 0.35wt%; the mass content a" of Ce is 5-15wt%, preferably 7-10wt%, for example, 9.3wt%.

[0015] According to an embodiment of the present invention, the ratio of the mass content a' of Ce in the main alloy powder to the mass content a' of Ce in the auxiliary alloy powder is a' / a'' (0-3.2):(6-13.6), preferably a' / a'' is 1:(5-7), exemplified by 1.55:7.75, 1.55:9.3, 1.55:9.6, 1.5:7.75, 1.5:9.3, 1.5:9.6; 0:9.3.

[0016] According to an embodiment of the present invention, the ratio c' / c'' of the mass content c' of Ti in the main alloy powder and the mass content c'' of Ti in the auxiliary alloy powder is (0.1-0.2):(0.2-0.4), for example, 0.17:0.25, 0.17:0.3, 0.17:0.35, 0.15:0.25, 0.15:0.3, 0.15:0.35.

[0017] According to an embodiment of the present invention, the remanence Br of the NdFeB sintered magnet is not less than 13 kGs, for example, 13.2 kGs, 13.4 kGs, 13.6 kGs, 13.8 kGs, or 14 kGs.

[0018] According to an embodiment of the present invention, the Hcj of the NdFeB sintered magnet is not less than 15.8 kOe, for example, 16 kOe, 16.2 kOe, 16.4 kOe, 16.6 kOe, 16.8 kOe, or 17 kOe.

[0019] The present invention also provides a method for preparing the above-mentioned NdFeB sintered magnet, which comprises: mixing main alloy powder and auxiliary alloy powder, and then subjecting the mixture to molding and sintering to obtain the NdFeB sintered magnet.

[0020] According to an embodiment of the present invention, the main alloy powder includes the following components: R, the mass content of R is 28-32wt%; R includes Ra and / or Ce; Ra is selected from Nd and / or Pr, and optionally includes at least one of Dy, Tb, Ho, and Gd; Wherein, the mass percentage x of Ce in the total mass of R in the main alloy powder is 0-10wt%, and x is, for example, 0wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%; B, the mass content of B is 0.95-1.05wt%, preferably 0.98-1.01wt%, for example 1wt%; Ti, the mass content of Ti is 0.1-0.2wt%, for example, 0.15wt%; The mass content of M, M is 1.5-2.5wt%; M is selected from at least one of Co, Cu, Ga, Al, Mn, Nb, W, Hf, and Cr; The balance is Fe.

[0021] According to an embodiment of the present invention, the auxiliary alloy powder includes the following components: R, the mass content of R is 30-34wt%; R includes Rb and Ce; Rb is selected from Nd and / or Pr, and optionally includes at least one of Dy, Tb, Ho, and Gd; Wherein, the mass percentage y of Ce in the total mass of R in the auxiliary alloy powder is 20-40wt%; B, the mass content of B is 0.95-1.05wt%, preferably 0.98-1.01wt%, for example 1wt%; Ti, the mass content of Ti is 0.2-0.4wt%, for example, 0.25wt%, 0.3wt%, 0.35wt%; The mass content of M, M is 1.5-2.5wt%; M is selected from at least one of Co, Cu, Ga, Al, Mn, Nb, W, Hf, and Cr; The balance is Fe.

[0022] According to an embodiment of the present invention, the ratio c' / c'' of the mass content c' of Ti in the main alloy powder and the mass content c'' of Ti in the auxiliary alloy powder is (0.1-0.2):(0.2-0.4), for example, 0.17:0.25, 0.17:0.3, 0.17:0.35, 0.15:0.25, 0.15:0.3, 0.15:0.35.

[0023] According to an embodiment of the present invention, the ratio of the mass content a' of Ce in the main alloy powder to the mass content a' of Ce in the auxiliary alloy powder is a' / a'' (0-3.2):(6-13.6), preferably a' / a'' is 1:(5-7), exemplified by 1.55:7.75, 1.55:9.3, 1.55:9.6, 1.5:7.75, 1.5:9.3, 1.5:9.6; 0:9.3.

[0024] According to an embodiment of the present invention, when mixed, the mass ratio of the main alloy powder to the auxiliary alloy powder is 5-15:1, for example, 8:1, 10:1, 12:1.

[0025] According to an embodiment of the present invention, the preparation method specifically comprises: Step 1: Mixing: mixing the main alloy powder and the auxiliary alloy powder to obtain a mixed powder; Step 2: Molding and sintering: the mixed powder is pressed and molded under magnetic field conditions to obtain a compact; the compact is sintered to obtain the NdFeB sintered magnet.

[0026] According to an embodiment of the present invention, the particle sizes of the main alloy powder and the auxiliary alloy powder are the same or different, and are independently selected from 1-5 μm, such as 2 μm, 3 μm, and 4 μm.

[0027] According to an embodiment of the present invention, the mass ratio of the main alloy powder to the auxiliary alloy powder has the meaning as described above, and is preferably 5-15:1.

[0028] According to the embodiment of the present invention, in step 1, the main alloy powder and the auxiliary alloy powder can be prepared by methods known in the art, as long as the components containing the corresponding mass content can be obtained. For example, the corresponding raw materials are prepared according to the components and mass contents of the main alloy powder and the auxiliary alloy powder, respectively melted to obtain the corresponding alloy flakes, and then respectively pulverized to obtain the main alloy powder and the auxiliary alloy powder.

[0029] Exemplarily, the corresponding alloy flakes are obtained by melting as follows: the raw materials of the main alloy powder and the auxiliary alloy powder are respectively melted by high-frequency induction heating to 1300-1600°C, poured onto a rapid cooling roller, and then dropped into a water-cooled barrel for further cooling to obtain the main alloy flakes and the auxiliary alloy flakes, respectively.

[0030] Exemplarily, the powder making is specifically as follows: respectively take the main alloy flakes and the auxiliary alloy flakes, firstly perform coarse crushing (such as hydrogen explosion), and then perform secondary grinding and pulverization (such as air flow milling) to obtain the main alloy powder and auxiliary alloy powder of the target particle size respectively.

[0031] According to an embodiment of the present invention, in step 1, a lubricant is optionally added during mixing. Preferably, the lubricant can be a lubricant known in the art, and the amount used in the art can be selected. Exemplarily, the lubricant is selected from volatile organic solvents such as lipids or alcohols, such as zinc stearate; Exemplarily, the amount of the lubricant is 0.01-2wt% of the total mass of the mixed powder, such as 0.02wt%.

[0032] According to an embodiment of the present invention, in step 1, mixing can be performed in a device known in the art using a method known in the art, as long as a uniformly mixed mixed powder can be obtained; for example, mixing in a V-type mixer for 6 hours.

[0033] According to an embodiment of the present invention, in step 2, the pressing and molding specifically comprises: pressing and molding the mixed powder in a magnetic field with an intensity ≥ 2T, and optionally further densifying it by cold isostatic pressing to form a compact.

[0034] According to an embodiment of the present invention, in step 2, the sintering treatment specifically includes: primary sintering, secondary sintering and aging sintering. Preferably, the primary sintering is specifically: heating the compact to 1000-1100°C under vacuum and heat preservation for 2-8 hours, and cooling to room temperature. Preferably, the secondary sintering is specifically: heating to 850-950°C and heat preservation for 2-6 hours, and cooling to room temperature. Preferably, the aging sintering is specifically: heating to 450-550°C and heat preservation for 2-6 hours.

[0035] The present invention also provides the application of the NdFeB magnet in the fields of electronic equipment, motors, generators, etc.

[0036] Compared with the prior art, the present invention has the following beneficial effects: The present invention can be widely used in the application fields of preparation of rare earth sintered magnets, powder metallurgy technology, materials science and engineering, etc. Studies have found that the addition of Ce element alone will easily form CeFe2 phase in the form of single grains due to the mixed valence characteristics of Ce, and Ce with a smaller ion radius will make it easy to form CeFe2 phase in the form of single grains, resulting in a lack of RE-rich phase distributed along the grain boundary between the main phase grains, which significantly reduces the coercive force of the magnet. This technical solution can effectively refine the grains and optimize the grain boundary structure by simultaneously adding a certain amount of alloying elements Ce and Ti to the rare earth permanent magnet powder material, forming a fine and dispersed titanium-rich phase, ingoting the domain wall, and improving the coercive force of the magnet, which is of great significance for improving the performance of rare earth magnets.

[0037] In addition, as PrNd resources are consumed in large quantities, the price of PrNd is gradually increasing. Using Ce to replace Pr and Nd in sintered NdFeB can not only reduce costs, but also help achieve balanced utilization of rare earth resources. DETAILED DESCRIPTION

[0038] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations 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 included in the scope that the present invention is intended to protect.

[0039] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0040] Examples 1-9 The preparation method of the NdFeB magnet comprises the following steps, wherein the element composition in the raw materials of the main alloy and the auxiliary alloy in each embodiment, and the mass ratio of the main alloy and the auxiliary alloy are all as shown in Table 1: 1. According to Table 1, the elemental metals used in each embodiment are weighed, and raw materials of the main alloy and the auxiliary alloy with corresponding elemental composition are prepared, wherein M in the main alloy and the auxiliary alloy is the same, and the mass content of M is 2wt% (M includes: Co, Al, Ga and Cu, and the mass ratio of Co:Al:Ga:Cu is 1:0.5:0.3:0.2). The weighed raw materials of the main alloy and the auxiliary alloy are respectively processed as follows to obtain the main alloy flakes and the auxiliary alloy flakes: under the protection of an argon atmosphere of about 0.03Mpa, the raw materials are heated to 1450℃-1550℃ by a high-frequency induction furnace for melting, and after melting, the raw materials are kept at 1450℃-1500℃ for homogenization for 20 minutes, and then the alloy melt is sprayed through the crucible mouth under the action of gravity onto the surface of the high-speed rotating water-cooled copper roller to achieve instant solidification and throw out, and then fall into a water-cooled barrel for further cooling to form alloy flakes, wherein the surface linear speed of the water-cooled copper roller is controlled to be 1.5m / s.

[0041] 2. The main alloy flakes and auxiliary alloy flakes obtained are respectively treated as follows to obtain main alloy powder and auxiliary alloy powder: coarsely crushed by hydrogen explosion treatment, and then the coarsely crushed powder is placed in a nitrogen atmosphere with an oxygen content of less than 10ppm and subjected to air flow milling at a grinding pressure of 0.6Mpa to obtain alloy powder with an average particle size of 3±0.5μm.

[0042] 3. Under nitrogen protection, the main alloy powder and the auxiliary alloy powder after jet milling in step 2 are mixed according to the corresponding weight percentages in Table 1, and 0.2wt% of zinc stearate lubricant is added, and the mixture is mixed by a V-type mixer for 6 hours to be uniformly mixed. The present invention has no particular limitation on the lubricant.

[0043] 4. The mixed alloy powder is pressed once in a nitrogen atmosphere with an oxygen content of less than 50ppm. During the pressing process, a 2T magnetic field is applied simultaneously to keep the magnetization direction of the powder consistent, and after the magnet shape is fixed, an appropriate reverse magnetic field is applied for demagnetization. The magnet after the first pressing is sealed, and then an isostatic pressing machine is used to perform a secondary forming at a pressure of 180MPa to further densify the magnet and form a compact.

[0044] 5. Heat the compact to 1080℃ in a vacuum sintering furnace and keep the vacuum degree less than 10 -3 The heat treatment was carried out under the condition of Pa for 6 hours, and then cooled to room temperature. The temperature was then raised to 900°C and kept for 6 hours for primary aging treatment, and then cooled to room temperature. The temperature was then raised to 500°C and kept for aging treatment for 6 hours, and finally cooled to obtain the NdFeB magnet.

[0045] Comparative Examples 1-6 The preparation method of Comparative Examples 1-6 refers to the preparation method of Examples 1-9, with the only difference being that the content of each element in the raw materials of the main alloy and the auxiliary alloy in each comparative example, and the mass ratio of the main alloy and the auxiliary alloy are shown in Table 2; other process conditions are the same as Examples 1-9.

[0046] Table 1 NdFeB magnet performance test results of the embodiment

[0047] Table 2 Performance test results of NdFeB magnets of comparative example

[0048] Note: In the main alloys and auxiliary alloys in Tables 1 and 2, the content of each element is in mass percentage, in units of wt%. For example, the main alloy (Nd 0.95 Ce 0.05 ) 31 Fe 65.84 Ti 0.17 M2B 0.99 It means that Nd and Ce account for 31wt% of the total mass of the main alloy (the mass ratio of Nd and Ce is 0.95:0.05), Fe accounts for 65.84wt% of the total mass of the main alloy, Ti accounts for 0.17wt% of the total mass of the main alloy, M accounts for 2wt% of the total mass of the main alloy, and B accounts for 0.99wt% of the total mass of the main alloy.

[0049] It can be seen from Table 1 that compared with Example 5: In Comparative Example 1, the content of auxiliary alloy Ce is too high (i.e., y is greater than 0.4wt%), and the introduction of too much Ce element at the grain boundary leads to an imbalance in the ratio of Ti element at the grain boundary, weakening the synergistic effect of the two, thereby inhibiting the generation of dispersed titanium-rich phase and significantly reducing the coercive force performance of the magnet.

[0050] In Comparative Example 2, the content of auxiliary alloy Ti is too low (less than 0.2wt%), and a fine dispersed titanium-rich phase cannot be formed in the grain boundary phase, resulting in reduced magnet performance; and the inventors found that when the content of auxiliary alloy Ti is too high, excess Ti will be enriched at the grain boundary to form a non-dispersed continuous titanium-rich phase, destroying the microstructure at the grain boundary and seriously affecting the magnetic properties. Moreover, a large amount of Ti enters the main phase of the auxiliary alloy, causing the main phase lattice distortion, which will also have a certain impact on the magnetic properties. In Comparative Example 3, the Ce content of the main alloy is too high (x is greater than 0.1wt%), and a large amount of CeFeB main phase is formed in the main phase grains. The CeFeB main phase grains in the magnet obtained after mixing the main alloy and the auxiliary alloy are significantly increased, thereby affecting the overall magnetic properties of the final magnet.

[0051] Comparative Example 4: The Ti content of the main alloy is too high (greater than 0.2wt%), and a large amount of Ti enters the main phase, causing the main phase lattice distortion, seriously affecting the magnetic properties. In addition, too much Ti is enriched at the grain boundary, forming a continuous titanium-rich phase with non-dispersed distribution, destroying the microstructure at the grain boundary and affecting the magnetic properties. The principle is basically the same as that of Comparative Example 2.

[0052] Comparative Examples 5-6: When the mass ratio of the main alloy to the auxiliary alloy is too small, the ratio of Ce to Ti in the grain boundary is unbalanced, the synergistic effect of the two is weakened, and the generation of a dispersed titanium-rich phase is inhibited; moreover, when the mass ratio of the main alloy to the auxiliary alloy is too small, that is, the content of the auxiliary alloy is too high, the CeFeB main phase grains are significantly increased and the coercive force is reduced. The inventors also found that when the mass ratio of the main alloy to the auxiliary alloy is too large, there is not enough Ti to form a fine dispersed titanium-rich phase at the grain boundary, and the magnetic properties of the magnet will also be reduced.

[0053] It can be seen from the above embodiments and comparative examples that when the Ce and Ti contents in the main alloy and the auxiliary alloy and the mass ratio of the main alloy and the auxiliary alloy exceed the scope of the present invention, the Ce and Ti content ratio in the product is unbalanced, and the effect of grain refinement cannot be achieved, and the tiny dispersed titanium-rich phase cannot be formed at the grain boundary, resulting in a significant deterioration of the magnetic properties of the sintered magnet, and the magnetic properties can be reduced by more than 10%. However, the present invention avoids the generation of soft magnetic phases in the main phase grains by precisely controlling the main alloy element composition; at the same time, the auxiliary alloy element composition is optimized, and the dosage ratio of the main alloy and the auxiliary alloy is adjusted, which not only achieves the refinement of the main phase grains, but also forms a tiny dispersed titanium-rich phase in the grain boundary phase, thereby improving the magnetic properties of the product.

[0054] The above is a description of the exemplary embodiments of the present invention. However, the protection scope of the present application is not limited to the above embodiments. Any modification, equivalent substitution, improvement, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A neodymium iron boron sintered magnet, characterized in that: It includes the following components: R, the mass content of R is 28-33wt%; R includes Nd and Ce, and optionally includes or excludes at least one of Pr, Dy, Tb, Ho, and Gd; The mass content of M, M is 1.5-2.5wt%; M is selected from at least one of Co, Cu, Ga, Al, Mn, Nb, W, Hf, and Cr; B, the mass content of B is 0.95-1.05wt%; Ti, the mass content of Ti is 0.1-0.25wt%; Fe is the balance; In the NdFeB sintered magnet, the mass content of Ce is 0.3-5wt%.

2. The NdFeB sintered magnet according to claim 1, characterized in that: In NdFeB sintered magnets, the mass content of R is 29-32wt%; In NdFeB sintered magnets, the mass content of B is 0.98-1.01wt%; In NdFeB sintered magnets, the mass content of Ti is 0.15-0.2wt%; In NdFeB sintered magnets, the mass content of Ce is 1.5-2.5wt%; In NdFeB sintered magnets, the mass ratio of Ti to Ce is 0.15-0.2:1.5-2.

5.

3. The NdFeB sintered magnet according to claim 1, characterized in that: The NdFeB sintered magnet is prepared by mixing a main alloy powder and an auxiliary alloy powder, pressing and molding, sintering, and then performing composite diffusion. The main alloy powder comprises at least Ti and optionally Ce, wherein the mass content c' of Ti is 0.1-0.2%; the mass content a' of Ce is not more than 4wt%; The auxiliary alloy powder includes at least Ti and Ce, wherein the mass content c" of Ti is 0.2-0.4%; the mass content a" of Ce is not more than 5-15wt%; The ratio a' / a'' of the mass content a' of Ce in the main alloy powder to the mass content a'' of Ce in the auxiliary alloy powder is (0-3.2):(6-13.6); The ratio c' / c'' of the mass content c' of Ti in the main alloy powder to the mass content c'' of Ti in the auxiliary alloy powder is (0.1-0.2):(0.2-0.4).

4. The NdFeB sintered magnet according to claim 1, characterized in that: The remanence Br of the NdFeB sintered magnet is not less than 13 kGs; The Hcj of the NdFeB sintered magnet is not less than 15.8 kOe.

5. The method for preparing a sintered NdFeB magnet according to any one of claims 1 to 4, characterized in that: The preparation method comprises: mixing main alloy powder and auxiliary alloy powder, and then performing molding and sintering treatment to obtain the NdFeB sintered magnet.

6. The preparation method according to claim 5, characterized in that: The main alloy powder comprises the following components: R, the mass content of R is 28-32wt%; R includes Ra and / or Ce; Ra is selected from Nd and / or Pr, and optionally includes at least one of Dy, Tb, Ho, and Gd; Wherein, the mass percentage x of Ce in the total mass of R in the main alloy powder is 0-10wt%; B, the mass content of B is 0.95-1.05wt%; Ti, the mass content of Ti is 0.1-0.2wt%; The mass content of M, M is 1.5-2.5wt%; M is selected from at least one of Co, Cu, Ga, Al, Mn, Nb, W, Hf, and Cr; The balance is Fe; And / or, the auxiliary alloy powder includes the following components: R, the mass content of R is 30-34wt%; R includes Rb and Ce; Rb is selected from Nd and / or Pr, and optionally includes at least one of Dy, Tb, Ho, and Gd; Wherein, the mass percentage y of Ce in the total mass of R in the auxiliary alloy powder is 20-40wt%; B, the mass content of B is 0.95-1.05wt%; Ti, the mass content of Ti is 0.2-0.4wt%; The mass content of M, M is 1.5-2.5wt%; M is selected from at least one of Co, Cu, Ga, Al, Mn, Nb, W, Hf, and Cr; The balance is Fe.

7. The preparation method according to claim 5, characterized in that: The ratio c' / c'' of the mass content c' of Ti in the main alloy powder to the mass content c'' of Ti in the auxiliary alloy powder is (0.1-0.2):(0.2-0.4); And / or, the ratio a' / a'' of the mass content a' of Ce in the main alloy powder to the mass content a'' of Ce in the auxiliary alloy powder is (0-3.2):(6-13.6); And / or, when mixed, the mass ratio of the main alloy powder to the auxiliary alloy powder is 5-15:

1.

8. The preparation method according to claim 5, characterized in that: The preparation method specifically comprises: Step 1: Mixing: mixing the main alloy powder and the auxiliary alloy powder to obtain a mixed powder; Step 2: Molding and sintering: the mixed powder is pressed and molded under magnetic field conditions to obtain a compact; the compact is sintered to obtain the NdFeB sintered magnet.

9. The preparation method according to claim 8, characterized in that: In step 2, the pressing and molding specifically comprises: pressing and molding the mixed powder in a magnetic field with an intensity of ≥ 2T, and optionally further densifying by cold isostatic pressing to form a compact; In step 2, the sintering treatment specifically includes: primary sintering, secondary sintering and aging sintering; the primary sintering specifically includes: heating the pressed green sheet to 1000-1100°C under vacuum and keeping the temperature for 2-8 hours, and cooling to room temperature; the secondary sintering specifically includes: heating the green sheet to 850-950°C and keeping the temperature for 2-6 hours, and cooling to room temperature; the aging sintering specifically includes: heating the green sheet to 450-550°C and keeping the temperature for 2-6 hours.

10. Application of the NdFeB magnet according to any one of claims 1 to 4 in the fields of electronic equipment, motors and generators.

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