A neodymium iron boron sintered magnet, its preparation method and application

Abstract

The present invention provides a NdFeB sintered magnet, a preparation method thereof and an application. The NdFeB sintered magnet of the present invention comprises the following components: R, the mass content of R is 28-33 wt%; R comprises Nd and Ce, and optionally comprises or does not comprise at least one of Pr, Dy, Tb, Ho, Gd; M, the mass content of M is 1.5-2.5 wt%; B, the mass content of B is 0.95-1.05 wt%; Ti, the mass content of Ti is 0.1-0.25 wt%; Fe is the balance; in the NdFeB sintered magnet, the mass content of Ce is 0.3-5 wt%. By precisely controlling the components of the master alloy elements, the present invention avoids the generation of soft magnetic phases in the main phase grains; at the same time, by optimizing the components of the auxiliary alloy elements and adjusting the dosage ratio of the master alloy and the auxiliary alloy, not only the main phase grains are refined, but also fine and dispersed titanium-rich phases are formed in the grain boundary phase, thereby improving the magnetic properties of the product.

Description

Technical Field

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

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

[0003] However, there are some problems in the preparation process of traditional Nd-Fe-B sintered magnets, such as insufficient control of the 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 compositions to improve the magnetic properties and reliability of the magnets. Summary of the Invention

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

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

[0006] A neodymium iron boron sintered magnet, which comprises the following components:

[0007] R, the mass content of R is 28 - 33 wt%; R includes Nd and Ce, and optionally includes or does not include at least one of Pr, Dy, Tb, Ho, Gd;

[0008] M, the mass content of M is 1.5 - 2.5 wt%; M is selected from at least one of Co, Cu, Ga, Al, Mn, Nb, W, Hf, Cr;

[0009] B, the mass content of B is 0.95 - 1.05 wt%;

[0010] Ti, the mass content of Ti is 0.1 - 0.25 wt%;

[0011] Fe is the balance;

[0012] In the neodymium iron boron sintered magnet, the mass content of Ce is 0.3 - 5 wt%.

[0013] According to an embodiment of the present invention, in the Nd-Fe-B sintered magnet, the mass content of R is preferably 29-32 wt%, for example, 30 wt%.

[0014] According to an embodiment of the present invention, in the Nd-Fe-B sintered magnet, the mass content of M is, for example, 2 wt%.

[0015] According to an embodiment of the present invention, in the Nd-Fe-B sintered magnet, the mass content of B is preferably 0.98-1.01 wt%, for example, 1 wt%.

[0016] According to an embodiment of the present invention, in the Nd-Fe-B sintered magnet, the mass content of Ti is preferably 0.15-0.2 wt%, for example, 0.18 wt%.

[0017] According to an embodiment of the present invention, in the Nd-Fe-B sintered magnet, the mass content of Ce is preferably 1.5-2.5 wt%, for example, 2 wt%.

[0018] According to an embodiment of the present invention, in the Nd-Fe-B sintered magnet, the mass ratio of Ti to Ce is 0.15-0.2:1.5-2.5, for example, 0.18:2.

[0019] According to an embodiment of the present invention, the Nd-Fe-B sintered magnet is prepared by mixing master alloy powder and auxiliary alloy powder, pressing into a mold, sintering, and then subjecting to composite diffusion.

[0020] According to an embodiment of the present invention, the master alloy powder includes at least Ti and optionally Ce. Among them, the mass content c' of Ti is 0.1-0.2%, for example, 0.15 wt%; the mass content a' of Ce is not more than 4 wt%, preferably 0-2.5 wt%, for example, 1.55 wt%.

[0021] According to an embodiment of the present invention, the auxiliary alloy powder includes at least Ti and Ce. Among them, the mass content c'' of Ti is 0.2-0.4%, for example, 0.25 wt%, 0.3 wt%, 0.35 wt%; the mass content a'' of Ce is 5-15 wt%, preferably 7-10 wt%, for example, 9.3 wt%.

[0022] According to an embodiment of the present invention, the ratio a' / a'' of the mass content a' of Ce in the master alloy powder to the mass content a'' of Ce in the auxiliary alloy powder is (0-3.2):(6-13.6), preferably a' / a'' is 1:(5-7), exemplarily 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.

[0023] According to an embodiment of the present invention, the ratio c' / c'' of the mass content c' of Ti in the master alloy powder to 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.

[0024] According to an embodiment of the present invention, the remanence Br of the Nd-Fe-B sintered magnet is not less than 13 kGs, for example, 13.2 kGs, 13.4 kGs, 13.6 kGs, 13.8 kGs, 14 kGs.

[0025] According to an embodiment of the present invention, the Hcj of the Nd-Fe-B 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, 17 kOe.

[0026] The present invention also provides a method for preparing the above Nd-Fe-B sintered magnet, and the preparation method includes: after mixing the master alloy powder and the auxiliary alloy powder, the Nd-Fe-B sintered magnet is obtained through shaping and sintering processes.

[0027] According to an embodiment of the present invention, the master alloy powder includes the following components:

[0028] R, the mass content of R is 28 - 32 wt%; R includes Ra and / or Ce; Ra is selected from Nd and / or Pr, and optionally includes at least one of Dy, Tb, Ho, Gd;

[0029] Among them, the mass percentage x of Ce in the total mass of R in the master alloy powder is 0 - 10 wt%, and x is, for example, 0 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%;

[0030] B, the mass content of B is 0.95 - 1.05 wt%, preferably 0.98 - 1.01 wt%, for example, 1 wt%;

[0031] Ti, the mass content of Ti is 0.1 - 0.2 wt%, for example, 0.15 wt%;

[0032] M, the mass content of M is 1.5 - 2.5 wt%; M is selected from at least one of Co, Cu, Ga, Al, Mn, Nb, W, Hf, Cr;

[0033] The balance is Fe.

[0034] According to an embodiment of the present invention, the auxiliary alloy powder includes the following components:

[0035] R, the mass content of R is 30 - 34 wt%; R includes Rb and Ce; Rb is selected from Nd and / or Pr, and optionally includes at least one of Dy, Tb, Ho, Gd;

[0036] wherein, the mass percentage y of Ce in the total mass of R in the auxiliary alloy powder is 20 - 40 wt%;

[0037] B, the mass content of B is 0.95 - 1.05 wt%, preferably 0.98 - 1.01 wt%, for example 1 wt%;

[0038] Ti, the mass content of Ti is 0.2 - 0.4 wt%, for example 0.25 wt%, 0.3 wt%, 0.35 wt%;

[0039] M, the mass content of M is 1.5 - 2.5 wt%; M is selected from at least one of Co, Cu, Ga, Al, Mn, Nb, W, Hf, Cr;

[0040] The balance is Fe.

[0041] According to an embodiment of the present invention, 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), 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.

[0042] According to an embodiment of the present invention, 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), preferably a' / a'' is 1:(5 - 7), exemplarily 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.

[0043] According to an embodiment of the present invention, when mixing, 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.

[0044] According to an embodiment of the present invention, the preparation method specifically includes:

[0045] Step 1, mixing: Mix the main alloy powder and the auxiliary alloy powder to obtain a mixed powder;

[0046] Step 2, forming and sintering: Press the mixed powder under magnetic field conditions to form a green compact; After sintering the green compact, the NdFeB sintered magnet is obtained.

[0047] 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, for example, 2 μm, 3 μm, 4 μm.

[0048] According to an embodiment of the present invention, the mass ratio of the main alloy powder and the auxiliary alloy powder has the meaning as described above, and is preferably 5-15:1.

[0049] According to an embodiment of the present invention, in step one, the main alloy powder and the auxiliary alloy powder can be prepared by methods known in the art, as long as components with corresponding mass contents can be obtained. For example, according to the components and mass contents of the main alloy powder and the auxiliary alloy powder as described above, corresponding raw materials are formulated, and the corresponding alloy sheets are respectively prepared by melting, and then the main alloy powder and the auxiliary alloy powder are respectively obtained through powder making.

[0050] Exemplarily, the specific process of melting to obtain the corresponding alloy sheets is as follows: the raw materials of the main alloy powder and the raw materials of the auxiliary alloy powder are respectively melted by high-frequency induction heating to 1300-1600 °C, then poured on a chill roll, and then fall into a water-cooled barrel for further cooling to respectively obtain the main alloy sheet and the auxiliary alloy sheet.

[0051] Exemplarily, the powder making is specifically as follows: the main alloy sheet and the auxiliary alloy sheet are respectively taken, first subjected to coarse crushing (such as hydrogen explosion), and then subjected to secondary grinding and pulverization (such as jet mill) to respectively obtain the main alloy powder and the auxiliary alloy powder with the target particle size.

[0052] According to an embodiment of the present invention, in step one, a lubricant is also optionally added during mixing. Preferably, the lubricant can be selected from lubricants known in the art, and the dosage known in the art can be used. Exemplarily, the lubricant is selected from volatile organic solvents such as esters or alcohols, for example, zinc stearate; Exemplarily, the dosage of the lubricant is 0.01-2 wt% of the total mass of the mixed powder, for example, 0.02 wt%.

[0053] According to an embodiment of the present invention, in step one, the mixing can be carried out by a method known in the art in a device known in the art, as long as a uniformly mixed powder can be obtained; for example, mixing in a V-type mixer for 6 h.

[0054] According to an embodiment of the present invention, in step two, the pressing and forming specifically includes: pressing and forming the mixed powder in a magnetic field with a strength ≥2 T, and optionally further densifying by cold isostatic pressing to form a green compact.

[0055] According to an embodiment of the present invention, in step two, the sintering treatment specifically includes: primary sintering, secondary sintering, and aging sintering. Preferably, the primary sintering is specifically: heating the green compact to a high temperature of 1000 - 1100 °C under vacuum conditions and holding for 2 - 8 h, then cooling to room temperature. Preferably, the secondary sintering is specifically: heating to 850 - 950 °C and holding for 2 - 6 h, then cooling to room temperature. Preferably, the aging sintering is specifically: heating to 450 - 550 °C and performing aging treatment for 2 - 6 h.

[0056] The present invention also provides the application of the above neodymium iron boron magnet in the fields of electronic devices, electric motors, generators, etc.

[0057] Compared with the existing technology, the beneficial effects of the present invention are as follows:

[0058] The present invention can have a wide range of applications in the fields of preparation of rare earth sintered magnets, powder metallurgy technology, and materials science and engineering. It has been found through research that when adding Ce element alone, due to the mixed valence characteristics of Ce, Ce with a smaller ionic radius is prone to form CeFe2 phase existing in the form of single grains, resulting in the lack of RE-rich phase distributed along the grain boundaries between the main phase grains, significantly reducing the coercivity of the magnet. By simultaneously compounding and adding a certain amount of alloy elements Ce and Ti to the rare earth permanent magnet powder material in this technical solution, the grains can be effectively refined, and at the same time, the grain boundary structure can be optimized to form a fine and dispersed titanium-rich phase, pinning the domain walls, and improving the coercivity of the magnet, which is of great significance for improving the performance of rare earth magnets.

[0059] In addition, as PrNd resources are consumed in large quantities, the price of PrNd has gradually increased. Substituting Ce for Pr and Nd in the application of sintered neodymium iron boron can not only reduce costs, but also contribute to the balanced utilization of rare earth resources. Specific Embodiments

[0060] 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 only illustrative of and explanatory of the present invention, and should not be construed as limiting the protection scope 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.

[0061] Unless otherwise specified, the raw materials and reagents used in the following embodiments are all commercially available products, or can be prepared by known methods.

[0062] Examples 1 - 9

[0063] The preparation method of the neodymium iron boron magnet includes the following steps. Among them, for the elemental composition and mass ratio of the main alloy and auxiliary alloy in the raw materials of each example, please refer to Table 1:

[0064] 1. Weigh the elemental metals used in each example according to Table 1, and prepare the raw materials of the master alloy and the auxiliary alloy with the corresponding elemental compositions. Here, M in the master alloy and the auxiliary alloy is the same, and the mass content of M is 2 wt% (M includes Co, Al, Ga, and Cu, and the mass ratio of Co:Al:Ga:Cu is 1:0.5:0.3:0.2). Treat the weighed raw materials of the master alloy and the auxiliary alloy respectively as follows to obtain the master alloy flakes and the auxiliary alloy flakes: Under the protection of an argon atmosphere of about 0.03 Mpa, heat the raw materials to 1450 °C - 1550 °C for melting through a high-frequency induction furnace, and keep them at 1450 °C - 1500 °C for 20 minutes for heat preservation and homogenization after melting. Then, under the action of gravity, spray the alloy melt onto the surface of a high-speed rotating water-cooled copper roller through the crucible mouth to achieve instantaneous solidification and ejection, and then fall into a water-cooled barrel for further cooling to form alloy flakes, where the surface linear velocity of the water-cooled copper roller is controlled at 1.5 m / s.

[0065] 2. Treat the obtained master alloy flakes and auxiliary alloy flakes respectively as follows to obtain the master alloy powder and the auxiliary alloy powder: Coarsely crush them through hydrogen explosion treatment, and then obtain alloy powders with an average particle size of 3 ± 0.5 μm under a nitrogen atmosphere with an oxygen content < 10 ppm through a jet mill at a grinding pressure of 0.6 Mpa.

[0066] 3. Under the protection of nitrogen, mix the master alloy powder and the auxiliary alloy powder after the jet mill in step 2 according to the corresponding weight percentages in Table 1, and add 0.2 wt% of zinc stearate lubricant, and mix evenly through a V-type mixer for 6 h. The present invention does not have any special limitations on the lubricant.

[0067] 4. Press the mixed alloy powders into shape once under the protection of a nitrogen atmosphere with an oxygen content < 50 ppm. During the first pressing process, apply a magnetic field of 2 T simultaneously to keep the magnetization directions of the powders consistent, and apply an appropriate reverse magnetic field for demagnetization treatment after the shape of the magnet is fixed. Seal the magnet after the first pressing, and then use an isostatic press to perform secondary forming at a pressure of 180 Mpa to further densify the magnet and form a green compact.

[0068] 5. Heat the green compact to a high temperature of 1080 °C through a vacuum sintering furnace, keep it under a vacuum degree < 10 -3 Pa for heat preservation treatment for 6 h, and then cool it to room temperature. Then raise the temperature to 900 °C for heat preservation for 6 h for primary aging treatment, and cool it to room temperature. Then raise the temperature to 500 °C for heat preservation and aging treatment for 6 h, and finally cool to obtain the NdFeB magnet.

[0069] Comparative Examples 1 - 6

[0070] The preparation methods of Comparative Examples 1-6 refer to the preparation methods of Examples 1-9, with the difference being only that the contents of each element in the raw materials of the master alloy and the auxiliary alloy and the mass ratio of the master alloy to the auxiliary alloy in each comparative example are shown in Table 2; other process conditions are the same as those of Examples 1-9.

[0071] Table 1 Test Results of the NdFeB Magnet Performance in Examples

[0072]

[0073] Table 2 Test Results of the NdFeB Magnet Performance in Comparative Examples

[0074]

[0075] Note: In the master alloy and the auxiliary alloy of Table 1 and Table 2, the content of each element is the mass percentage content, with the unit of wt%. For example, in the master alloy of Example 1 (Nd 0.95 Ce 0.05 ), 31 Fe 65.84 Ti 0.17 M 2 B 0.99 it means that Nd and Ce account for 31 wt% of the total mass of the master alloy (the mass ratio of Nd to Ce is 0.95:0.05), Fe accounts for 65.84 wt% of the total mass of the master alloy, Ti accounts for 0.17 wt% of the total mass of the master alloy, M accounts for 2 wt% of the total mass of the master alloy, and B accounts for 0.99 wt% of the total mass of the master alloy.

[0076] It can be seen from Table 1 that compared with Example 5:

[0077] In Comparative Example 1, the content of the auxiliary alloy Ce is too high (i.e., y > 0.4 wt%), introducing too much Ce element at the grain boundary, which is disproportionate to the Ti element at the grain boundary. The synergistic effect between the two is weakened, thus inhibiting the generation of the finely dispersed titanium-rich phase, and the coercivity performance of the magnet decreases significantly.

[0078] In Comparative Example 2, the content of the auxiliary alloy Ti is too low (< 0.2 wt%), and fine and dispersed titanium-rich phases cannot be formed in the grain boundary phase, resulting in a decrease in magnet performance; moreover, the inventor found that when the content of the auxiliary alloy Ti is too high, excess Ti will accumulate at the grain boundary, forming a continuous titanium-rich phase with non-dispersed distribution, 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 lattice distortion of the main phase, which will also have a certain impact on the magnetic properties.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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 method for preparing a sintered NdFeB magnet, characterized in that: The preparation method comprises: mixing the main alloy powder and the auxiliary alloy powder, and then subjecting the mixture to molding and sintering to obtain the NdFeB sintered magnet; The sintering treatment specifically includes: primary sintering, secondary sintering and aging sintering; the primary sintering specifically includes: heating the compact 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 to 850-950°C and keeping the temperature for 2-6 hours, and cooling to room temperature; the aging sintering specifically includes: heating to 450-550°C and keeping the temperature for 2-6 hours; 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); 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); when mixed, the mass ratio of the main alloy powder to the auxiliary alloy powder is 5-15:1; The main alloy powder consists of the following components: R, the mass content of R is 28-33wt%; R is composed of Ra and / or Ce; Ra is selected from Nd, 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 0.95-1.01wt%; Ti, the mass content of Ti is 0.1-0.25wt%; 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; The auxiliary alloy powder consists of the following components: R, the mass content of R is 30-34wt%; R is composed of Rb and Ce; Rb is selected from Nd, 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.

2. The preparation method according to claim 1, 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.

3. The preparation method according to claim 2, characterized in that: In step 2, the pressing and molding specifically includes: pressing and molding the mixed powder in a magnetic field with an intensity of ≥ 2T, and optionally further densifying it by cold isostatic pressing to form a compact.

4. The preparation method according to claim 1, characterized in that: The NdFeB sintered magnet comprises 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 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 0.95-1.01wt%; 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%.

5. The preparation method according to claim 4, characterized in that: In the NdFeB sintered magnet, the mass content of R is 29-32wt%.

6. The preparation method according to claim 4, characterized in that: In the NdFeB sintered magnet, the mass content of B is 0.98-1.01wt%.

7. The preparation method according to claim 4, characterized in that: In the NdFeB sintered magnet, the mass content of Ti is 0.15-0.2wt%.

8. The preparation method according to claim 4, characterized in that: In the NdFeB sintered magnet, the mass content of Ce is 1.5-2.5wt%.

9. The preparation method according to claim 4, characterized in that: In the NdFeB sintered magnet, the mass ratio of Ti to Ce is 0.15-0.2:1.5-2.

5.

10. The preparation method 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.

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