Neodymium-iron-boron magnet and preparation method thereof

Abstract

The invention relates to the field of neodymium-iron-boron magnet preparation, in particular to a neodymium-iron-boron magnet and a preparation method thereof. The neodymium-iron-boron magnet is prepared from the following components in parts by weight: 15.9 parts of praseodymium neodymium, 15.5 to 17 parts of cerium, 0.9 to 1 part of boron, 0.2 to 0.4 part of cobalt, 0.2 to 0.4 part of aluminum, 0.2 to 0.3 part of copper, 0.1 to 0.2 part of titanium, 0.2 to 0.4 part of niobium, 0.1 to 0.2 part of zirconium and 60 to 67 parts of iron. A cobalt-rich grain boundary phase is formed through cobalt to inhibit disordered diffusion and disappearance of magnetic domains, magnetic domain arrangement is optimized, aluminum inhibits growth of crystal grains to refine the crystal grains, and the residual magnetism and the intrinsic coercive force of the neodymium-iron-boron magnet are improved through the synergistic effect of the two elements.

Description

Technical Field

[0001] The present application relates to the field of NdFeB magnet preparation, and in particular to a NdFeB magnet and a preparation method thereof. Background Art

[0002] As an important member of the current magnetic material field, NdFeB magnets have been widely used in various fields such as motors, speakers, sensors, medical devices, and wind power generation due to their excellent properties such as high remanence, high magnetic energy product, and relatively high Curie temperature. However, with the advancement of science and technology and the development of industry, the performance requirements for NdFeB magnets are also increasing.

[0003] Traditionally, efforts to enhance the magnetic properties of NdFeB magnets have focused on adjusting rare earth elements. For example, the introduction of heavy rare earth elements such as terbium and dysprosium acts as a catalyst for magnetic properties, significantly enhancing the overall performance of the magnet. In recent years, researchers have begun exploring ways to optimize the microstructure of NdFeB magnets by adding specific elements, thereby improving their magnetic properties. However, determining the optimal selection and addition of these elements, as well as the synergistic mechanisms between them to meet the growing demands of industrial applications, remains a challenging and hot topic in current research. Summary of the Invention

[0004] In order to improve the magnetic properties of NdFeB magnets, the present application uses cobalt and aluminum in combination to change the lattice structure of NdFeB magnets, optimize the magnetic domain arrangement, and thus improve the remanence and intrinsic coercivity of NdFeB magnets.

[0005] In a first aspect, the present application provides a neodymium iron boron magnet, which adopts the following technical solution: A neodymium iron boron magnet comprises the following components in parts by weight: 15.9 parts of praseodymium and neodymium, 15.5-17 parts of cerium, 0.9-1 part of boron, 0.2-0.4 part of cobalt, 0.2-0.4 part of aluminum, 0.2-0.3 part of copper, 0.1-0.2 part of titanium, 0.2-0.4 part of niobium, and 60-67 parts of iron.

[0006] By adopting the above technical solution, adding cobalt to the NdFeB magnet can form a cobalt-rich grain boundary phase, inhibiting the disordered diffusion and disappearance of magnetic domains. This inhibitory effect helps to maintain the stability and order of the magnetic domains, optimizes the arrangement of the magnetic domains, and makes it more difficult for the magnet to lose its magnetism in a reverse magnetic field, thereby improving the remanence and intrinsic coercive force of the NdFeB magnet; and adding aluminum to the NdFeB magnet can form a NdFeB interphase composite on the grain interface, which helps to form a stable grain boundary phase, inhibits the growth of grains, thereby obtaining fine grains, and further improving the remanence and intrinsic coercive force of the NdFeB magnet; by appropriately adjusting the content of cobalt and aluminum, further optimization of the remanence and intrinsic coercive force can be achieved to a certain extent.

[0007] Preferably, the mass ratio of cobalt to aluminum is 1:0.8-1.2.

[0008] By adopting the above technical solution, when the aluminum content is too low, the aluminum element is insufficient to form sufficient NdFeB interphase composites on the grain interface to stabilize the grain boundary phase, and the effect of inhibiting abnormal grain growth is not obvious; when the aluminum content is too high, too many NdFeB interphase composites will be formed on the grain interface, causing the grain boundary phase to become too "hard", thereby limiting the movement and rearrangement of magnetic domains between grains. The reduced flexibility of the magnetic domains may affect a substantial decrease in the remanence of the magnet; for this reason, the applicant finally determined after a lot of research and experimental verification that the mass ratio of cobalt to aluminum in this application is appropriate to be the above.

[0009] Preferably, the NdFeB magnet further comprises sulfide, and the weight portion of the sulfide is 0.2-0.7 parts.

[0010] By adopting the above technical solution and adding sulfide to the NdFeB alloy powder, the sulfur element will react with the rare earth element during the sintering process to form neodymium sulfide and neodymium oxysulfide in the Nd-rich grain boundary phase, thereby enhancing the magnetic isolation effect of the grain boundary and significantly improving the intrinsic coercive force; at the same time, the behavior of sulfur element segregation in the Nd-rich grain boundary phase can lower the melting point of the Nd-rich phase and increase the fluidity of the Nd-rich phase during the sintering process, thereby improving the wettability between the main phase particles and the Nd-rich phase particles. This improvement helps to optimize the boundary structure, making the grain boundary distribution tighter and more uniform, thereby further improving the intrinsic coercive force of the NdFeB magnet.

[0011] Although sulfide can improve the intrinsic coercive force of NdFeB magnets, when the amount of sulfide added is too high, it may cause sulfur to replace some oxygen atoms and enter the crystal lattice of the magnet, resulting in lattice distortion. This distortion will change the orientation and size of the magnetic moment, further affecting the magnetic properties of the magnet; and when the amount of sulfide added is too low, too little sulfur is introduced, and the effect of improving the magnetic properties of the NdFeB magnet is not obvious. For this reason, after extensive research and experimental verification, the applicant finally determined that the weight of the sulfide in this application is preferably the above.

[0012] Preferably, the sulfide is at least one of tungsten sulfide, molybdenum disulfide and zinc sulfide.

[0013] By adopting the above technical solution, molybdenum disulfide is well-known for its excellent lubrication properties. It helps to reduce the friction between NdFeB alloy particles during the sintering process, promote better bonding between particles, increase the density of the magnet, and thus increase the remanence of the magnet; zinc sulfide has good chemical stability. The addition of zinc forms a binary or ternary phase with neodymium and iron, which helps to form a stable grain boundary phase, stabilize the magnetic domain, and increase the intrinsic coercive force of the magnet.

[0014] Tungsten sulfide is known for its high hardness and excellent thermal stability, effectively enhancing the wear and heat resistance of magnets. Furthermore, tungsten sulfide is also used as a solid lubricant under high temperature, high pressure, high load, and high vacuum conditions. It helps reduce friction between NdFeB alloy particles during sintering, promotes better bonding between particles, and increases the density of the magnet, thereby improving the remanence of the magnet. The introduction of tungsten can also form borides within or at the boundaries of the main phase grains, replacing the original boron-rich phase, thereby preventing the growth of the main phase grains and improving the intrinsic coercivity of the magnet. Therefore, after comparison, tungsten sulfide was found to be the preferred choice among the three.

[0015] Preferably, the sulfide is tungsten sulfide, and the weight portion of the tungsten sulfide is 0.35-0.6 parts.

[0016] By adopting the above technical solution, when the addition amount of tungsten sulfide is too low, the content of introduced sulfur and tungsten elements is small, and the effects of sulfur and tungsten in inhibiting abnormal grain growth are not obvious; when the addition amount of tungsten sulfide is too high, excessive introduction will cause component segregation of tungsten in the NdFeB magnet, and the irregular aggregation of tungsten in the grain boundary phase will lead to abnormal grain growth, thereby reducing the performance of the NdFeB magnet; for this reason, the applicant finally determined after a lot of research and experimental verification that the weight of tungsten sulfide in this application is preferably the above.

[0017] Preferably, the sulfide is a mixture of tungsten sulfide and zinc sulfide.

[0018] By adopting the above technical solution, the high hardness and thermal stability of tungsten sulfide help to enhance the wear resistance and heat resistance of the magnet. At the same time, tungsten sulfide can form borides inside or at the boundaries of the main phase grains, replacing the original boron-rich phase, thereby effectively preventing the growth of the main phase grains and achieving grain refinement; and the zinc in zinc sulfide can form binary or ternary phases with neodymium and iron, which helps to form a stable grain boundary phase. The stable magnetic domain further inhibits the growth of grains, thereby maintaining the stability of the magnet performance and further improving the intrinsic coercive force of the magnet.

[0019] By properly adjusting the content of tungsten sulfide and zinc sulfide, the problems of component segregation and irregular aggregation can be avoided, thereby ensuring the uniform distribution of tungsten sulfide and zinc sulfide inside the magnet; this uniform distribution helps to maintain the stability of the magnet's performance, enabling it to maintain excellent magnetic properties under most environments.

[0020] Preferably, the mass ratio of tungsten sulfide to zinc sulfide is 2:1-2.

[0021] By adopting the above technical solution, when the zinc sulfide content is too low, although tungsten sulfide can significantly enhance the wear resistance and heat resistance of the magnet and effectively prevent the growth of the main phase grains, the role of zinc sulfide in stabilizing the grain boundary phase and stabilizing the magnetic domain will become less obvious. Too low a zinc sulfide content may result in an unclear stabilizing effect on the grain boundary phase of the magnet.

[0022] When the zinc sulfide content is too high, although zinc can form a stable binary or ternary phase with neodymium and iron, which helps to form a stable grain boundary phase and stable magnetic domains, too much zinc may increase the inhomogeneity of the internal composition of the magnet, affect the arrangement of magnetic domains and the orientation of magnetic moments, thereby reducing the overall magnetic properties of the magnet. In particular, too much zinc sulfide may cause part of the zinc to replace part of the iron element and enter the main phase, thereby reducing the remanence of the magnet.

[0023] Therefore, after extensive research and experimental verification, the applicant finally determined that the mass ratio of tungsten sulfide to zinc sulfide in the present application is preferably as described above.

[0024] In a second aspect, the present application provides a method for preparing a neodymium iron boron magnet, using the following technical solution: A method for preparing a neodymium iron boron magnet, for preparing the above-mentioned neodymium iron boron magnet, comprises the following steps: 1) Melting and stripping: weighing praseodymium, neodymium, cerium, boron, copper, titanium, aluminum, niobium, zirconium, cobalt and iron according to the formula amount for smelting, and spinning the obtained molten liquid to obtain strip-spinning sheets; 2) Hydrogen crushing and grinding: the stripping sheet is subjected to hydrogen crushing and then subjected to jet mill grinding to obtain magnetic powder; 3) Mixing and pressing: placing the magnetic powder under nitrogen protection and performing compression molding to obtain a pressed embryo; 4) Sintering and tempering: the pressed green body is sintered and then subjected to a secondary tempering heat treatment to obtain a NdFeB magnet.

[0025] By adopting the above technical solution, through steps such as melt spinning, hydrogen crushing and grinding, mixed pressing and sintering and tempering, efficient utilization of raw materials and uniform distribution of components are achieved, which promotes the formation of fine grains and the construction of ordered magnetic domain structure, thereby significantly optimizing the magnetic properties of the magnet, including improving key indicators such as intrinsic coercive force and magnetic energy product, while improving production efficiency and quality stability, and reducing production costs, providing an efficient and reliable way to prepare high-performance, high-quality NdFeB magnets.

[0026] Preferably, the sulfide is added during the jet milling treatment in step 2).

[0027] By adopting the above technical solution, sulfides may undergo complex chemical reactions with other metal elements in a high-temperature molten state, resulting in uneven distribution of components or the production of undesirable phase structures. However, adding sulfides during the airflow milling process can avoid such chemical reactions at high temperatures. At the same time, the high-speed airflow is used to evenly disperse the sulfide particles in the magnetic powder, which helps to avoid local aggregation and composition segregation of the sulfides, providing favorable conditions for subsequent compression molding.

[0028] Preferably, the sintering temperature is 1000-1300°C.

[0029] By adopting the above technical solution, if the sintering temperature is too high, it will affect the thermal stability of the NdFeB magnet, thereby reducing the magnetic properties of the magnet; if the sintering temperature is too low, the uniformity and density of the internal structure of the NdFeB magnet are poor, and the magnetic properties of the obtained NdFeB magnet are low; for this reason, the applicant finally determined after a lot of research and experimental verification that the sintering temperature of this application is appropriate to be the above.

[0030] In summary, this application has the following beneficial effects: 1. This application uses cobalt to form a cobalt-rich grain boundary phase to suppress the disordered diffusion and disappearance of magnetic domains, optimize the magnetic domain arrangement, and uses aluminum to suppress grain growth to refine the grains. The two elements cooperate with each other to improve the remanence and intrinsic coercivity of the NdFeB magnet; 2. This application enhances the magnetic isolation effect of grain boundaries by adding sulfides. At the same time, the behavior of sulfur elements segregating at the neodymium-rich grain boundaries helps to optimize the boundary structure, making the grain boundary distribution more compact and uniform, thereby further improving the intrinsic coercive force of the neodymium iron boron magnet. DETAILED DESCRIPTION

[0031] The raw materials in this application include the following parts: Praseodymium-neodymium: commercially available products using praseodymium-neodymium alloys; Cerium: a commercially available product with CAS number 7440-45-1 was used; Boron: a commercial product with CAS number 7440-42-8 was used; Cobalt: a commercial product with CAS number 7440-48-4 was used; Aluminum: commercially available product with CAS number 7429-90-5 was used; Niobium: commercially available product with CAS number 7440-03-1 was used; Copper: a commercially available product with CAS number 7440-05-8 was used; Titanium: a commercially available product with CAS number 7440-32-6 was used; Zirconium: a commercially available product with CAS number 7440-67-7 was used; Iron: a commercially available product with CAS number 7439-89-6 was used; Tungsten sulfide: a commercial product with CAS number 12138-09-9 is used; Molybdenum disulfide: a commercial product with CAS number 1317-33-5 was used; Zinc sulfide: a commercially available product with CAS number 1314-98-3 is used; The present application is further described in detail below with reference to the following examples and comparative examples.

[0032] Example 1 A method for preparing a neodymium iron boron magnet comprises the following steps: 1) Melting and stripping: According to the formula, 1590g of praseodymium and neodymium, 1610g of cerium, 92g of boron, 30g of cobalt, 30g of aluminum, 22g of copper, 30g of niobium, 15g of titanium, 10g of zirconium, and 6570g of iron were weighed and smelted, and the obtained molten liquid was stripped to obtain a stripping sheet; 2) Hydrogen crushing and grinding: The strip is subjected to hydrogen crushing and then jet milling to obtain magnetic powder with an average particle size of 3.5 μm (the average particle size can be between 3-4 μm); 3) Mixed pressing: The magnetic powder is placed under nitrogen protection and molded to obtain a pressed embryo; 4) Sintering and tempering: The pressed blank is sintered at a sintering temperature of 1200°C for 5.5 hours, and then subjected to a secondary tempering heat treatment, with the first tempering temperature at 800°C and the tempering time being 3 hours. After the end, the product is cooled to room temperature using argon gas, and then the second tempering heat treatment is started, with the second tempering temperature at 500°C and the tempering time being 4 hours. After the end, the product is cooled to room temperature using argon gas to obtain a NdFeB magnet.

[0033] Example 2-3 In Example 2-3, based on the preparation method of Example 1, the content of each component in the formula was adjusted. The specific adjustments are shown in Table 1.

[0034] Comparative Examples 1-3 Comparative Examples 1-3 are based on the preparation method of Example 1, and the content of each component in the formula is adjusted. The specific adjustments are shown in Table 1.

[0035] Table 1 Raw materials and performance test table of NdFeB magnets of Examples 1-3 and Comparative Examples 1-3 Performance Test The NdFeB magnets of Examples 1-3 and Comparative Examples 1-3 were subjected to the following performance tests. The test results are shown in Table 1: Remanence and intrinsic coercivity According to GB / T 3217-2013 “Magnetic test methods for permanent magnetic (hard magnetic) materials”, the remanence (Br) and intrinsic coercivity (Hcj) of NdFeB magnets are tested.

[0036] Referring to Table 1, by comparing Examples 1-3 and Comparative Examples 1-3, it can be seen that compared with Comparative Example 3, the remanence and intrinsic coercive force of Examples 1-3 are much higher than those of Comparative Example 3, indicating that the addition of cobalt and aluminum to NdFeB magnets can effectively improve the magnetic properties of NdFeB magnets.

[0037] Similarly, the remanence and intrinsic coercive force of Examples 1-3 are higher than those of Comparative Examples 1-2; for Comparative Example 1, no cobalt is added to the NdFeB magnet, and only aluminum is used to suppress grain growth, thereby improving the intrinsic coercive force of the magnet to a limited extent; for Comparative Example 2, no aluminum is added to the NdFeB magnet, and only cobalt is used to form a cobalt-rich grain boundary phase and optimize the magnetic domain arrangement, and the improvement in the magnetic properties of the magnet is not as obvious as adding cobalt and aluminum at the same time.

[0038] Therefore, adding cobalt and aluminum to the NdFeB magnet simultaneously can more effectively improve the magnetic properties of the NdFeB magnet. In comparison, the magnetic properties of the NdFeB magnet of Example 1 are preferred among Examples 1-3.

[0039] Examples 4-7 In Examples 4-7, based on the preparation method of Example 1, the amount of aluminum added was adjusted. The specific adjustments are shown in Table 2.

[0040] The NdFeB magnets of Examples 4-7 were subjected to the above performance tests, and the test results are shown in Table 2.

[0041] Table 2 Aluminum addition amount and performance test table of Example 1, Examples 4-7 Referring to Table 2, by comparing Example 1 and Examples 4-7, it can be seen that as the amount of aluminum added continues to increase, the remanence and intrinsic coercive force of the NdFeB magnet both show a trend of first increasing and then decreasing. This may be because as the amount of aluminum added continues to increase, aluminum continues to refine the grains in the NdFeB magnet, thereby increasing the magnetic properties of the NdFeB magnet; when the amount of aluminum added exceeds a certain range, part of the aluminum may replace iron and enter the main phase, affecting the main phase structure, and reducing the magnetic properties of the NdFeB magnet.

[0042] Examples 8-11 Example 8 Based on the preparation method of Example 1, in step 2), 50g of tungsten sulfide and the belt-spinning pieces after hydrogen destruction are jet-milled together to obtain magnetic powder, and the other conditions remain unchanged.

[0043] In Examples 9-10, based on the preparation method of Example 8, the type of sulfide was adjusted. The specific adjustments are shown in Table 3.

[0044] Example 11 Based on the preparation method of Example 8, tungsten sulfide is replaced by a mixture of tungsten sulfide and zinc sulfide, the mass ratio of zinc sulfide to tungsten sulfide in the mixture is 2:1.5, and the other conditions remain unchanged.

[0045] The NdFeB magnets of Examples 8-11 were subjected to the above performance tests, and the test results are shown in Table 3.

[0046] Table 3 Sulfide types and performance test table of Example 1 and Examples 8-11 Referring to Table 3, by comparing Example 1 with Examples 8-11, it can be seen that the addition of sulfide to the NdFeB magnet can effectively improve the intrinsic coercive force of the magnet. This may be because the sulfur element reacts with the rare earth element during the sintering process, is enriched in the Nd-rich phase and forms new compounds. The sulfur element plays two roles in stabilizing the grain boundary phase and optimizing the boundary structure, thereby effectively improving the intrinsic coercive force of the NdFeB magnet.

[0047] In addition, adding tungsten sulfide to NdFeB magnets can also effectively improve the remanence of the magnet. This may be because tungsten sulfide, as a solid lubricant, helps to reduce friction during the sintering process, increase the density of the magnet, and thus increase the remanence of the magnet; at the same time, tungsten forms borides inside or at the boundaries of the main phase grains, preventing the growth of the main phase grains, thereby further improving the intrinsic coercive force of the magnet.

[0048] Adding molybdenum disulfide to NdFeB magnets can also effectively improve the remanence of the magnets. This may be because both molybdenum disulfide and tungsten sulfide are solid lubricants, which also play a role in improving the density of the magnets.

[0049] Adding zinc sulfide to NdFeB magnets can further increase the intrinsic coercive force of the magnet. This may be because zinc forms a binary or ternary phase with neodymium and iron, which helps to form a stable grain boundary phase, further inhibiting the growth of grains, thereby increasing the intrinsic coercive force of the magnet.

[0050] Comparing Examples 8-10, it is found that Example 8 has the best performance and is preferred.

[0051] Comparing Example 8 and Example 11, it is found that Example 11 has better performance, which shows that the mixed addition of tungsten sulfide and zinc sulfide enables the two to cooperate with each other to jointly improve the remanence and intrinsic coercive force of the NdFeB magnet, and is therefore preferred.

[0052] Examples 12-17 In Examples 12-17, based on the preparation method of Example 8, the amount of tungsten sulfide added was adjusted. The specific adjustments are shown in Table 4.

[0053] The NdFeB magnets of Examples 12-17 were subjected to the above performance tests, and the test results are shown in Table 4.

[0054] Table 4: Addition amount and performance test table of tungsten sulfide in Example 8 and Examples 12-17 Referring to Table 4, by comparing Example 8 and Examples 12-17, it can be seen that as the amount of tungsten sulfide added continues to increase, the remanence and intrinsic coercive force of the NdFeB magnet both show a trend of increasing and then decreasing. This may be because as the amount of tungsten sulfide added continues to increase, sulfur and tungsten continuously stabilize the grain boundary phase in the NdFeB magnet, optimize the boundary structure, and thus continuously improve the magnetic properties of the NdFeB magnet; when the amount of tungsten sulfide added exceeds a certain range, it may cause tungsten component segregation in the NdFeB magnet, resulting in abnormal grain growth. At the same time, sulfur replaces part of the oxygen atoms into the crystal lattice of the magnet, resulting in lattice distortion, which in turn reduces the magnetic properties of the NdFeB magnet.

[0055] Examples 18-21 In Examples 18-21, based on the preparation method of Example 11, the mass ratio of tungsten sulfide to zinc sulfide in the mixture was adjusted. The specific adjustments are shown in Table 5.

[0056] The NdFeB magnets of Examples 18-21 were subjected to the above performance tests, and the test results are shown in Table 5.

[0057] Table 5 Mass ratio of tungsten sulfide and zinc sulfide in the mixture of Example 11 and Examples 18-21 and performance test table Referring to Table 5, it can be seen from Example 11 and Examples 18-21 that as the mass ratio of tungsten sulfide and zinc sulfide continues to decrease, the magnetic properties of the NdFeB magnet show a trend of first increasing and then decreasing. This may be because as the mass ratio of tungsten sulfide and zinc sulfide continues to decrease, zinc continues to form a binary or ternary phase with neodymium and iron in the NdFeB magnet, forming a stable grain boundary phase, stabilizing the magnetic domain, and inhibiting the growth of grains, thereby improving the overall magnetic properties of the magnet; when the mass ratio of tungsten sulfide and zinc sulfide is reduced to a certain range, the inhomogeneity of the internal composition of the magnet increases, affecting the arrangement of the magnetic domain and the orientation of the magnetic moment, and the role of tungsten sulfide in improving the density of the magnet during the sintering process of the NdFeB magnet continues to weaken. At the same time, zinc replaces part of the iron into the main phase, affecting the main phase structure, and reducing the overall magnetic properties of the magnet.

[0058] Examples 22-25 In Examples 22-25, based on the preparation method of Example 1, the sintering temperature was adjusted. The specific adjustments are shown in Table 6.

[0059] The NdFeB magnets of Examples 22-25 were subjected to the above performance tests, and the test results are shown in Table 6.

[0060] Table 6 Sintering temperature and performance test data of Example 1 and Examples 22-25 Referring to Table 6, by comparing Example 1 and Examples 22-25, it can be seen that as the sintering temperature continues to increase, the remanence and intrinsic coercive force of the NdFeB magnet show a trend of first increasing and then decreasing. This may be because as the sintering temperature continues to increase, the uniformity and density of the internal structure of the NdFeB magnet continue to improve, thereby making the magnetic properties of the NdFeB magnet continue to improve; when it exceeds a certain range, it will affect the thermal stability of the NdFeB magnet, thereby reducing the magnetic properties of the NdFeB magnet.

[0061] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A neodymium iron boron magnet, characterized in that: The invention comprises the following components in parts by weight: 15.9 parts of praseodymium and neodymium, 15.5-17 parts of cerium, 0.9-1 part of boron, 0.2-0.4 part of cobalt, 0.2-0.4 part of aluminum, 0.2-0.3 part of copper, 0.1-0.2 part of titanium, 0.2-0.4 part of niobium, 0.1-0.2 part of zirconium and 60-67 parts of iron.

2. The NdFeB magnet according to claim 1, wherein: The mass ratio of cobalt to aluminum is 1:0.8-1.

2.

3. The NdFeB magnet according to claim 1, wherein: The invention also comprises sulfide, wherein the weight portion of the sulfide is 0.2-0.7 parts.

4. The NdFeB magnet according to claim 3, wherein: The sulfide is at least one of tungsten sulfide, molybdenum disulfide and zinc sulfide.

5. The NdFeB magnet according to claim 4, wherein: The sulfide is tungsten sulfide, and the weight portion of the tungsten sulfide is 0.35-0.6 parts.

6. The NdFeB magnet according to claim 4, wherein: The sulfide is a mixture of tungsten sulfide and zinc sulfide.

7. The NdFeB magnet according to claim 6, wherein: The mass ratio of the tungsten sulfide to the zinc sulfide is 2:1-2.

8. The method for preparing the NdFeB magnet according to any one of claims 1 to 2, characterized in that: The following steps are involved: 1) Melting and spinning: Pr, Nd, Cer, B, Co, Aluminum, Co, Titanium, Niobium, Zr and Iron are weighed according to the formula and smelted. The obtained molten liquid is spun to obtain spinning sheets; 2) Hydrogen crushing and grinding: the stripping sheet is subjected to hydrogen crushing and then subjected to air flow grinding to obtain magnetic powder; 3) Mixing and pressing: the magnetic powder is placed under nitrogen protection and molded to obtain a pressed embryo; 4) Sintering and tempering: The pressed green body is sintered and then subjected to a secondary tempering heat treatment to obtain a NdFeB magnet.

9. The method for preparing a NdFeB magnet according to claim 8, wherein: In step 2), the sulfide and the hydrogen-broken stripped pieces are ground together by jet milling to obtain magnetic powder.

10. The method for preparing a NdFeB magnet according to claim 8, wherein: In step 4), the sintering temperature is 1000-1300°C.

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