Neodymium-iron-boron magnet and method for producing the same

Abstract

This invention relates to a neodymium iron boron (NdFeB) magnet and its preparation method, comprising the following steps: providing NdFeB pre-formed magnetic powder; mixing the NdFeB pre-formed magnetic powder with alloy powder to obtain a mixed powder, and subjecting the mixed powder to hot pressing sintering and hot deformation treatment to obtain the NdFeB magnet. The alloy powder contains at least one of Cu or Al elements, heavy rare earth elements, light rare earth elements, and Ga elements, with the atomic percentage of heavy rare earth elements in the alloy powder being less than or equal to 45%. This preparation method can improve the utilization rate of heavy rare earth elements, thereby effectively improving the coercivity and temperature stability of the iron boron magnet with less heavy rare earth elements, thus reducing the amount of heavy rare earth elements used and lowering the raw material cost of the NdFeB magnet.

Description

Technical Field

[0001] This invention relates to the field of rare earth permanent magnet materials technology, and in particular to neodymium iron boron magnets and their preparation methods. Background Technology

[0002] Neodymium iron boron magnets have excellent magnetic properties, and are therefore widely used in aerospace, power electronics, medical devices and transportation.

[0003] Traditional NdFeB magnets have a relatively low Curie temperature of approximately 312°C. Prolonged operation at these high temperatures leads to severe thermal demagnetization. Therefore, heavy rare earth elements are typically used to replace some of the neodymium to improve coercivity and thus temperature stability. However, the utilization rate of heavy rare earth elements in the traditional NdFeB magnet manufacturing process is low, while their natural reserves are very limited and their prices are extremely high, resulting in persistently high raw material costs for traditional NdFeB magnets. Summary of the Invention

[0004] Therefore, it is necessary to provide a neodymium iron boron magnet and its preparation method to address the above problems. This preparation method can improve the utilization rate of heavy rare earth elements, thereby effectively improving the coercivity and temperature stability of iron boron magnets with less heavy rare earth elements, thus reducing the amount of heavy rare earth elements used and lowering the raw material cost of neodymium iron boron magnets.

[0005] This invention provides a method for preparing neodymium iron boron magnets, comprising the following steps:

[0006] Provide neodymium iron boron pre-fabricated magnetic powder; and

[0007] The neodymium iron boron pre-made magnetic powder is mixed with alloy powder to obtain a mixed powder, and the mixed powder is subjected to hot pressing sintering and hot deformation treatment to obtain a neodymium iron boron magnet. The alloy powder contains at least one of Cu or Al, heavy rare earth elements, light rare earth elements and Ga, and the atomic percentage of the heavy rare earth elements in the alloy powder is less than or equal to 45%.

[0008] In one embodiment, the molecular formula of the alloy powder is R. a H b T c Ga d Where R includes Nd and / or Pr, H includes Tb and / or Dy, T is Cu or Al, 30≤a≤45, 30≤b≤45, 5≤c≤20, 5≤d≤20.

[0009] In one embodiment, the alloy powder has a mass fraction of 1%-10% in the mixed powder.

[0010] In one embodiment, the particle size of the alloy powder is 30μm-200μm.

[0011] In one embodiment, the molecular formula of the neodymium iron boron pre-formed magnetic powder is L x Fe 100-x-y-z M y B z Where L is Nd or a mixture of Nd and Pr, M includes at least one of Co, Ga, Cu or Al, 12≤x≤15, 0≤y≤8, 4≤z≤8.

[0012] In one embodiment, the grain size of the neodymium iron boron pre-formed magnetic powder is 30nm-100nm.

[0013] In one embodiment, the hot pressing sintering step is performed at a temperature of 600°C-750°C for 3 min-20 min.

[0014] In one embodiment, the temperature in the heat deformation treatment step is 650℃-850℃, the deformation amount is 65%-75%, and the time is 3min-10min.

[0015] A neodymium iron boron magnet is prepared by the method described above for preparing neodymium iron boron magnets.

[0016] In one embodiment, the grain size of the neodymium iron boron magnet is 150nm-350nm.

[0017] In the method for preparing neodymium iron boron magnets provided by this invention, the alloy powder contains at least four different metallic elements. Because the irregular arrangement of these metallic atoms can weaken the metallic bonds between them, the alloy powder can be transformed into a liquid phase at a lower temperature during hot pressing sintering and hot deformation. This liquid phase has excellent fluidity and permeability. Furthermore, the addition of Ga further enhances the wettability of the liquid phase. On the one hand, this allows the heavy rare earth elements in the alloy powder to be distributed around the grains of the neodymium iron boron pre-made magnetic powder along with the flow of the liquid phase, effectively improving the utilization rate of heavy rare earth elements. On the other hand, it can shorten the time for hot pressing sintering and hot deformation, thereby making the grains of the neodymium iron boron magnet finer.

[0018] Furthermore, when the liquid phase in the alloy powder is distributed around the grains of the NdFeB pre-made magnetic powder, some heavy rare earth elements can enter the grains to enhance the magnetocrystalline anisotropy, while other heavy rare earth elements will accumulate at the grain edges to form a heavy rare earth-rich shell. In addition, the various metal elements in the alloy powder work together to enhance the coercivity of the NdFeB magnet, thereby improving the temperature stability of the NdFeB magnet.

[0019] Therefore, the method for preparing neodymium iron boron magnets provided by the present invention can effectively improve the coercivity and temperature stability of iron boron magnets with less heavy rare earth elements, thereby reducing the amount of heavy rare earth elements used and lowering the raw material cost of neodymium iron boron magnets. Attached Figure Description

[0020] Figure 1 Demagnetization curves of neodymium iron boron magnets provided in Examples 1, 2, and 1;

[0021] Figure 2 Coercivity of neodymium iron boron magnets provided in Examples 1, 2 and Comparative Example 1 at different temperatures;

[0022] Figure 3 This is a comparison of the consumption of heavy rare earth elements and the increase in coercivity in Examples 1 and 2 and related literature;

[0023] Figure 4 Backscattered electron images of the neodymium iron boron magnets provided in Examples 1, 2 and Comparative Example 1 using scanning electron microscopes. Detailed Implementation

[0024] The neodymium iron boron magnet and its preparation method provided by the present invention will be further described below.

[0025] The method for preparing neodymium iron boron magnets provided by this invention includes the following steps:

[0026] S1 provides neodymium iron boron pre-formed magnetic powder; and

[0027] S2, NdFeB pre-made magnetic powder is mixed with alloy powder to obtain mixed powder, and the mixed powder is subjected to hot pressing sintering and hot deformation treatment to obtain NdFeB magnet.

[0028] It should be noted that the basic microstructure characteristics of NdFeB magnets mainly include grain phase and NdFeB-rich phase at grain boundaries. Among them, the structure and chemical composition of the NdFeB-rich phase at grain boundaries are important microscopic factors affecting the magnetic properties of NdFeB magnets, such as coercivity and temperature stability.

[0029] In step S1, the main function of the neodymium iron boron pre-formed magnetic powder is to form the crystalline phase of the neodymium iron boron magnet. In one embodiment, the molecular formula of the neodymium iron boron pre-formed magnetic powder is L x Fe 100-x-y-z M y B z Where L is Nd or a mixture of Nd and Pr, M includes at least one of Co, Ga, Cu or Al, 12≤x≤15, 0≤y≤8, 4≤z≤8.

[0030] Understandably, in NdFeB preformed magnetic powder, L can be Nd alone or a mixture of Nd and Pr. When L is a mixture of Nd and Pr, considering that excessive Pr is not conducive to grain texture formation, the atomic percentage of Pr in the NdFeB preformed magnetic powder does not exceed 50% of (Nd+Pr). In addition, the NdFeB preformed magnetic powder may or may not include element M. Considering that element M can combine with rare earth element Nd and element Pr to form a low-melting-point Nd-rich phase at grain boundaries, it can reduce the stress of grains during deformation, making the hot deformation process easier, and reduce the magnetic coupling between grains, thus enhancing coercivity. Therefore, preferably, 0.1≤y≤8.

[0031] In one embodiment, the grain size of the neodymium iron boron pre-formed magnetic powder is 30nm-100nm, more preferably 40nm-60nm.

[0032] It should be noted that neodymium iron boron pre-formed magnetic powder can be purchased from commercial channels or prepared by oneself. In one embodiment, the preparation method of neodymium iron boron pre-formed magnetic powder includes the following steps: mixing the ingredients according to the proportion of each element in the neodymium iron boron pre-formed magnetic powder to obtain a first mixture; melting the first mixture to obtain a first master alloy; quenching the first master alloy to obtain a first thin strip; and crushing the first thin strip to obtain neodymium iron boron pre-formed magnetic powder.

[0033] The first mixture can be a mixture of alloy materials containing each element, or a mixture of metallic compounds and non-metallic compounds containing each element.

[0034] The steps of melting the first mixture and obtaining the first thin strip from the first master alloy by rapid quenching are both carried out under argon protection.

[0035] To obtain relatively superior overall magnetic properties, the particle size of neodymium iron boron pre-fabricated magnetic powder is 40μm-100μm.

[0036] In step S2, the main function of the alloy powder is to form the neodymium-rich phase at the grain boundary of the neodymium iron boron magnet. The alloy powder contains at least one of Cu or Al elements, heavy rare earth elements, light rare earth elements, and Ga elements. The atomic percentage of heavy rare earth elements in the alloy powder is less than or equal to 45%.

[0037] Understandably, in the first embodiment, the alloy powder contains Cu, heavy rare earth elements, light rare earth elements, and Ga; in the second embodiment, the alloy powder contains Al, heavy rare earth elements, light rare earth elements, and Ga; and in the third embodiment, the alloy powder contains Cu, Al, heavy rare earth elements, light rare earth elements, and Ga. Thus, the alloy powder contains at least four different metallic elements. Because the irregular arrangement of these metal atoms can weaken the metallic bonds between them, the alloy powder can transform into a liquid phase at a lower temperature during hot pressing and hot deformation processes. This liquid phase exhibits excellent fluidity and permeability. Furthermore, the addition of Ga further enhances the wettability of the liquid phase, allowing the heavy rare earth elements in the alloy powder to distribute around the NdFeB pre-formed magnetic powder grains along with the liquid phase flow, effectively improving the utilization rate of the heavy rare earth elements.

[0038] Furthermore, when the metal elements in the alloy powder are distributed around the grains of the NdFeB pre-made magnetic powder, some of the heavy rare earth elements can enter the grains to enhance the magnetocrystalline anisotropy, while other heavy rare earth elements will accumulate at the grain edges to form a heavy rare earth-rich shell, thereby enhancing the coercivity and temperature stability of the NdFeB magnet.

[0039] In one embodiment, considering the influence of heavy rare earth elements on the intrinsic magnetic properties of the grain phase, the heavy rare earth elements preferably include at least one of Tb or Dy. To balance the coercivity and remanence of the final NdFeB magnet and to reduce the amount of heavy rare earth elements used, the atomic percentage of heavy rare earth elements in the alloy powder is 35%-45%.

[0040] Light rare earth elements are mainly distributed in the neodymium-rich phase at grain boundaries, diluting the proportion of ferromagnetic elements such as Fe and Co in the neodymium-rich phase at grain boundaries, making the neodymium-rich phase at grain boundaries non-ferromagnetic, reducing the magnetic coupling between hard magnetic grain phases, and thus improving the coercivity of neodymium iron boron magnets.

[0041] In one embodiment, the light rare earth element includes at least one of La, Ce, Nd, or Pr. Considering the influence of each light rare earth element on the intrinsic magnetic properties of the main phase, the light rare earth element preferably includes at least one of Nd or Pr. To obtain a liquid phase with higher fluidity, the atomic percentage of the light rare earth element in the alloy powder is 35%-45%.

[0042] Cu and / or Al elements are mainly distributed in the Nd:1 phase at grain boundaries, combining with light rare earth elements to form a non-ferromagnetic phase. This reduces the magnetic coupling between hard magnetic grain phases, which is beneficial for improving coercivity. In order to form a low-melting-point liquid phase in the alloy powder during heating, in one embodiment, the total mass of Cu and Al elements accounts for 5%-20% of the atomic percentage of the alloy powder.

[0043] Ga is mainly distributed in the Nd+ phase at grain boundaries, combining with Nd, Pr, and Fe to form a non-ferromagnetic phase. This reduces the magnetic coupling between hard magnetic grain phases and improves the wettability of the Nd+ phase, optimizing the distribution of heavy rare earth elements and increasing their utilization rate. In one embodiment, the atomic percentage of Ga in the alloy powder is 5%-20%.

[0044] Thus, the metallic elements in the alloy powder work synergistically to enhance the coercivity of the NdFeB magnet, thereby improving its temperature stability.

[0045] In one embodiment, the molecular formula of the alloy powder is R a H b T c Ga d Where R includes Nd and / or Pr, H represents heavy rare earth elements, T is Cu or Al, 30≤a≤45, 30≤b≤45, 5≤c≤20, and 5≤d≤20.

[0046] In one embodiment, the mass fraction of alloy powder in the mixed powder is 1%-10%.

[0047] In one embodiment, the method for preparing alloy powder includes the following steps:

[0048] The alloy powder is batched according to the proportion of each element to obtain a second mixture; the second mixture is smelted to obtain a second master alloy; the second master alloy is subjected to a rapid solidification method to obtain a second rapid solidification sheet; the second rapid solidification sheet is crushed to obtain alloy powder.

[0049] The second mixture can be a mixture of alloy materials containing each element, or a mixture of metallic compounds containing each element.

[0050] The steps of melting the second mixture and obtaining the second quick-solidified sheet from the second master alloy by a quick-solidification method are both carried out under argon protection.

[0051] In order to better suppress grain growth, in one embodiment, the particle size of the alloy powder is 30μm-200μm, and more preferably 50μm-100μm.

[0052] Understandably, in the step of mixing neodymium iron boron pre-made magnetic powder with alloy powder to obtain mixed powder, the specific mixing method is not limited. In one embodiment, mixing can be carried out by equipment such as a mixer.

[0053] Understandably, hot pressing sintering serves to obtain a dense, isotropic NdFeB blank, while hot deformation serves to obtain anisotropic NdFeB magnets.

[0054] In one embodiment, the temperature in the hot pressing sintering step is 600°C-750°C, more preferably 660°C-680°C.

[0055] In one embodiment, during the heat deformation treatment step, the temperature is 650°C-850°C, more preferably 820°C-840°C, and the deformation amount is 65%-75%, more preferably 70%.

[0056] Because the alloy powder of this invention has excellent liquid phase fluidity and a relatively high process temperature is selected, the hot pressing sintering and hot deformation time can be shortened, thereby making the NdFeB magnet grains finer.

[0057] In one embodiment, the hot pressing sintering step takes 3-20 minutes, more preferably 4-6 minutes.

[0058] In one embodiment, the heat deformation treatment step takes 3-10 minutes, more preferably 4-5 minutes.

[0059] Both the hot pressing and sintering steps and the hot deformation treatment steps are carried out under vacuum conditions or a protective atmosphere.

[0060] The present invention also provides a neodymium iron boron magnet, which is prepared by the above-described method for preparing neodymium iron boron magnets.

[0061] In one embodiment, the grain size in the nanocrystalline NdFeB magnet is 150nm-350nm.

[0062] Therefore, the method for preparing neodymium iron boron magnets provided by this invention can effectively improve the magnetic properties of iron boron magnets, such as coercivity and temperature stability, with less heavy rare earth elements, thereby reducing the amount of heavy rare earth elements used and lowering the raw material cost of neodymium iron boron magnets.

[0063] The following specific examples will further illustrate the method for preparing neodymium iron boron magnets and their preparation.

[0064] Example 1

[0065] Provides molecular formula Nd 10.1 Pr 3.4 Fe76.5 Ga 0.4 Co 3.9 B 5.7 Neodymium iron boron pre-fabricated magnetic powder, with a grain size of 40nm-60nm.

[0066] Raw materials with a purity greater than 99% are processed according to Nd... 35 Dy 35 Cu 15 Ga 15 The proportions are added to the furnace, and then the alloy powder with an average particle size of 100 μm is prepared by rapid solidification and mechanical crushing. The melting point of the alloy powder is 616℃. The above-mentioned neodymium iron boron pre-made magnetic powder is mixed with the alloy powder to obtain a mixed powder. In the mixed powder, the mass fraction of neodymium iron boron pre-made magnetic powder is 95%, and the mass fraction of alloy powder is 5%.

[0067] The above-mentioned mixed powder was loaded into a mold and hot-pressed in a vacuum hot press furnace at a temperature of 670°C, a pressure of 4 MPa, and a time of 5 min to obtain a dense and isotropic NdFeB blank.

[0068] Under an argon atmosphere, the above-mentioned NdFeB blank was subjected to hot deformation treatment at a temperature of 830°C, with a deformation amount of about 70% and a time of 4 minutes, to obtain an anisotropic NdFeB magnet.

[0069] Example 2

[0070] Provides molecular formula Nd 10.1 Pr 3.4 Fe 76.5 Ga 0.4 Co 3.9 B 5.7 Neodymium iron boron pre-fabricated magnetic powder, with a grain size of 40nm-60nm.

[0071] Raw materials with a purity greater than 99% are processed according to Nd... 35 Tb 35 Cu 15 Ga 15 The proportions are added to the furnace, and then the alloy powder with an average particle size of 100 μm is prepared by rapid solidification and mechanical crushing. The melting point of the alloy powder is 605℃. The above-mentioned neodymium iron boron pre-made magnetic powder is mixed with the alloy powder to obtain a mixed powder. In the mixed powder, the mass fraction of neodymium iron boron pre-made magnetic powder is 95%, and the mass fraction of alloy powder is 5%.

[0072] The above-mentioned mixed powder was loaded into a mold and hot-pressed in a vacuum hot press furnace at a temperature of 670°C, a pressure of 4 MPa, and a time of 5 min to obtain a dense and isotropic NdFeB blank.

[0073] Under an argon atmosphere, the above-mentioned NdFeB blank was subjected to hot deformation treatment at a temperature of 830°C, with a deformation amount of about 70% and a time of 4 minutes, to obtain an anisotropic NdFeB magnet.

[0074] Comparative Example 1

[0075] Provides molecular formula Nd 10.1 Pr 3.4 Fe 76.5 Ga 0.4 C0 3.9 B 5.7 Neodymium iron boron pre-fabricated magnetic powder, with a grain size of 40nm-60nm.

[0076] The aforementioned NdFeB pre-formed magnetic powder was loaded into a mold and hot-pressed in a vacuum hot press furnace at a temperature of 670°C, a pressure of 4 MPa, and a time of 5 min to obtain a dense, isotropic NdFeB blank.

[0077] Under an argon atmosphere, the above-mentioned NdFeB blank was subjected to hot deformation treatment at a temperature of 830°C, with a deformation amount of about 70% and a time of 4 minutes, to obtain an anisotropic NdFeB magnet.

[0078] Figure 1 The demagnetization curves of the neodymium iron boron magnets provided in Examples 1, 2, and Comparative Example 1; by Figure 1 It can be seen that, compared with Comparative Example 1, the coercivity of the neodymium iron boron magnets prepared in Example 1 and Example 2 increased to 2.6T and 2.7T respectively, indicating a significant enhancement in coercivity.

[0079] Figure 2 The coercivity of the neodymium iron boron magnets provided in Examples 1, 2, and Comparative Example 1 at different temperatures; by Figure 2 It can be seen that, compared with Comparative Example 1, the coercivity temperature coefficients of the neodymium iron boron magnets prepared in Examples 1 and 2 are increased to -0.398% / ℃ and -0.387% / ℃, respectively, indicating that the temperature stability is significantly enhanced.

[0080] Figure 3 The NdFeB magnet prepared in Example 1 is compared with NdFeB magnets reported in other literature. As can be seen from the figure, Example 1 and Example 2 obtained higher coercivity when using the same mass of heavy rare earth elements.

[0081] Figure 3Among them, H.Sepehri-Amin represents Enhancement of coercivity of hot-deformed Nd-Fe-B anisotropic magnet by low-temperature grain boundary diffusion ofNd 60 Dy 20 Cu 20 Eutectic alloy reported neodymium iron boron magnets;

[0082] L.Liu represents Coercivity enhancement of hot-deformed Nd-Fe-B magnets by the eutectic grain boundary diffusion process using Nd 62 Dy 20 Al 18 Alloy reported neodymium iron boron magnets;

[0083] J.Li represents NdFeB magnets, which are characterized by their coercivity and thermal stability enhanced by the eutectic grain boundary diffusion process.

[0084] Y.Lee stands for Coercivity enhancement of hot-deformed NdFeB magnets bydoping R 80 Ga 20 (R=Pr, Dy, Tb)alloys, Comparison on the Coercivity Enhancement ofHot-Deformed Nd2Fe 14 B-Type Magnets by Doping R 70 Cu 30 And NdFeB magnets reported in the study of Coercivity enhancement in hot deformed Nd2Fe14B-type magnets by doping low-melting RCu alloys (R=Nd, Dy, Nd+Dy);

[0085] Y. Liu represents the report on the magnetic properties and microstructure evolution of in-situ Tb-Cu diffusion treated hot-deformed Nd-Fe-B magnets;

[0086] X.Tang represents neodymium iron boron magnets reported by a two-step eutectic grain boundary diffusion process, characterized by improved coercivity and squareness in bulk hot-deformed Nd-Fe-B magnets.

[0087] Q.Liu represents neodymium iron boron magnets reported on the effect of Tb-Fe diffusion on magnetic properties and thermal stability of hot-deformed magnets;

[0088] Z. Wang represents the neodymium iron boron magnet reported with a hot-deformed Nd-Fe-B magnet and a macroscopic composite structure;

[0089] S. SaWatzki represents the reported diffusion processes in hot-deformed Nd-Fe-B magnets with DyF3 additions in neodymium iron boron magnets.

[0090] Figure 4 Backscattered electron images of the neodymium iron boron magnets provided in Examples 1, 2, and Comparative Example 1, obtained by scanning electron microscopy; Figure 4 It can be seen that the neodymium-rich phase around the grain phase of the neodymium iron boron magnets prepared in Examples 1 and 2 is significantly increased, and the grains are refined.

[0091] Example 3

[0092] Provides molecular formula Nd 10.1 Pr 3.4 Fe 76.5 Ga 0.4 Co 3.9 B 5.7 Neodymium iron boron pre-fabricated magnetic powder, with a grain size of 40nm-60nm.

[0093] Raw materials with a purity greater than 99% are processed according to Nd... 35 Dy 35 Cu 15 Ga 15 The proportions are added to the furnace, and then the mixture is rapidly solidified and mechanically crushed to prepare alloy powder with an average particle size of 100 μm and a melting point of 616 °C. The above-mentioned neodymium iron boron pre-made magnetic powder is mixed with the alloy powder to obtain a mixed powder. In the mixed powder, the mass fraction of neodymium iron boron pre-made magnetic powder is 97.5% and the mass fraction of alloy powder is 2.5%.

[0094] The above-mentioned mixed powder was loaded into a mold and hot-pressed in a vacuum hot press furnace at a temperature of 670°C, a pressure of 4 MPa, and a time of 5 min to obtain a dense and isotropic NdFeB blank.

[0095] Under an argon atmosphere, the above-mentioned NdFeB blank was subjected to hot deformation treatment at a temperature of 830°C, with a deformation amount of about 70% and a time of 4 minutes, to obtain an anisotropic NdFeB magnet.

[0096] Example 4

[0097] Provides molecular formula Nd 10.1 Pr 3.4 Fe 76.5 Ga 0.4 Co 3.9 B 5.7 Neodymium iron boron pre-fabricated magnetic powder, with a grain size of 40nm-60nm.

[0098] Raw materials with a purity greater than 99% are processed according to Nd... 35 Tb 35 Cu 15 Ga 15 The proportions are added to the furnace, and then the mixture is rapidly solidified and mechanically crushed to prepare alloy powder with an average particle size of 100 μm and a melting point of 605 °C. The above-mentioned neodymium iron boron pre-made magnetic powder is mixed with the alloy powder to obtain a mixed powder. In the mixed powder, the mass fraction of neodymium iron boron pre-made magnetic powder is 97.5% and the mass fraction of alloy powder is 2.5%.

[0099] The above-mentioned mixed powder was loaded into a mold and hot-pressed in a vacuum hot press furnace at a temperature of 670°C, a pressure of 4 MPa, and a time of 5 min to obtain a dense and isotropic NdFeB blank.

[0100] Under an argon atmosphere, the above-mentioned NdFeB blank was subjected to hot deformation treatment at a temperature of 830°C, with a deformation amount of about 70% and a time of 4 minutes, to obtain an anisotropic NdFeB magnet.

[0101] Example 5

[0102] Provides molecular formula Nd 10.1 Pr 3.4 Fe 76.5 Ga 0.4 Co 3.9 B 5.7 Neodymium iron boron pre-fabricated magnetic powder, with a grain size of 40nm-60nm.

[0103] Raw materials with a purity greater than 99% are processed according to Nd... 35 Dy 35 Cu 15 Ga 15 The proportions are added to the furnace, and then the alloy powder with an average particle size of 100 μm is prepared by rapid solidification and mechanical crushing. The melting point of the alloy powder is 616℃. The above-mentioned neodymium iron boron pre-made magnetic powder is mixed with the alloy powder to obtain a mixed powder. In the mixed powder, the mass fraction of neodymium iron boron pre-made magnetic powder is 95%, and the mass fraction of alloy powder is 5%.

[0104] The above-mentioned mixed powder was loaded into a mold and hot-pressed in a vacuum hot press furnace at a temperature of 670°C, a pressure of 4 MPa, and a time of 30 min to obtain a dense and isotropic NdFeB blank.

[0105] Under an argon atmosphere, the above-mentioned NdFeB blank was subjected to hot deformation treatment at a temperature of 830°C, with a deformation amount of about 70% and a time of 4 minutes, to obtain an anisotropic NdFeB magnet.

[0106] Example 6

[0107] Provides molecular formula Nd 10.1 Pr 3.4 Fe 76.5 Ga 0.4 Co 3.9 B 5.7 Neodymium iron boron pre-fabricated magnetic powder, with a grain size of 40nm-60nm.

[0108] Raw materials with a purity greater than 99% are processed according to Nd... 35 Dy 35 Cu 15 Ga 15 The proportions are added to the furnace, and then the alloy powder with an average particle size of 100 μm is prepared by rapid solidification and mechanical crushing. The melting point of the alloy powder is 616℃. The above-mentioned neodymium iron boron pre-made magnetic powder is mixed with the alloy powder to obtain a mixed powder. In the mixed powder, the mass fraction of neodymium iron boron pre-made magnetic powder is 99%, and the mass fraction of alloy powder is 1%.

[0109] The above-mentioned mixed powder was loaded into a mold and hot-pressed in a vacuum hot press furnace at a temperature of 670°C, a pressure of 4 MPa, and a time of 5 min to obtain a dense and isotropic NdFeB blank.

[0110] Under an argon atmosphere, the above-mentioned NdFeB blank was subjected to hot deformation treatment at a temperature of 830°C, with a deformation amount of about 70% and a time of 4 minutes, to obtain an anisotropic NdFeB magnet.

[0111] Comparative Example 2

[0112] Provides molecular formula Nd 10.1 Pr 3.4 Fe 76.5 Ga 0.4 C0 3.9 B 5.7 Neodymium iron boron pre-fabricated magnetic powder, with a grain size of 40nm-60nm.

[0113] Raw materials with a purity greater than 99% are processed according to Dy 70 Cu 30 The proportions are added to the furnace, and then the alloy powder with an average particle size of 100 μm is prepared by rapid solidification and mechanical crushing. The melting point of the alloy powder is 828℃. The above-mentioned neodymium iron boron pre-made magnetic powder is mixed with the alloy powder to obtain a mixed powder. In the mixed powder, the mass fraction of neodymium iron boron pre-made magnetic powder is 95%, and the mass fraction of alloy powder is 5%.

[0114] The above-mentioned mixed powder was loaded into a mold and hot-pressed in a vacuum hot press furnace at a temperature of 670°C, a pressure of 4 MPa, and a time of 5 min to obtain a dense and isotropic NdFeB blank.

[0115] Under an argon atmosphere, the above-mentioned NdFeB blank was subjected to hot deformation treatment at a temperature of 830°C, with a deformation amount of about 70% and a time of 4 minutes, to obtain an anisotropic NdFeB magnet.

[0116] Comparative Example 3

[0117] Provides molecular formula Nd 10.1 Pr 3.4 Fe 76.5 Ga 0.4 Co 3.9 B 5.7 Neodymium iron boron pre-fabricated magnetic powder, with a grain size of 40nm-60nm.

[0118] Neodymium iron boron pre-formed magnetic powder was mixed with Dy in a 1:1:1 mass ratio 70 Cu 30 、Nd 70 Cu 30Dy 80 Ga 20 The alloy powders are mixed to obtain a mixed powder, in which the mass fraction of neodymium iron boron pre-made magnetic powder is 95%.

[0119] The above-mentioned mixed powder was loaded into a mold and hot-pressed in a vacuum hot press furnace at a temperature of 670°C, a pressure of 4 MPa, and a time of 5 min to obtain a dense and isotropic NdFeB blank.

[0120] Under an argon atmosphere, the above-mentioned NdFeB blank was subjected to hot deformation treatment at a temperature of 830°C, with a deformation amount of about 70% and a time of 4 minutes, to obtain an anisotropic NdFeB magnet.

[0121] Test case

[0122] The magnetic properties of the neodymium iron boron magnets prepared in Examples 1-6 and Comparative Examples 1-3 were tested according to the following standards, and the test results are shown in Table 1.

[0123] The grain size of the neodymium iron boron magnet was obtained statistically from the backscattered images obtained by scanning electron microscopy.

[0124] Coercivity: The magnetization curve of the neodymium iron boron magnet was measured using an ultra-high coercivity permanent magnet measuring instrument (model: PFM14.CN).

[0125] Temperature coefficient of coercivity: The coercivity was measured at 200℃ and 20℃ respectively, and the temperature coefficient of coercivity was calculated using the following formula: β=(H T2 -H T1 ) / [H T1 ×(T2-T1)]. Where β represents the temperature coefficient of coercivity, H... T2 H represents the coercivity at temperature T2. T1 This represents the coercivity at temperature T1.

[0126] Table 1

[0127]

[0128]

[0129] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0130] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method of producing a neodymium-iron-boron magnet, characterized by, The method comprises the following steps: Providing neodymium-iron-boron pre-made magnetic powder, wherein the grain size of the neodymium-iron-boron pre-made magnetic powder is 30-100 nm; and The neodymium-iron-boron prefabricated magnetic powder is mixed with alloy powder to obtain mixed powder, and the mixed powder is subjected to hot-press sintering and hot deformation treatment to obtain a neodymium-iron-boron magnet, wherein the alloy powder contains at least one of Cu element or Al element, heavy rare earth element, light rare earth element and Ga element, the atomic percentage of the heavy rare earth element in the alloy powder is less than or equal to 45%, and the molecular formula of the alloy powder is R a H b T c Ga d a H b T c Ga d wherein R includes Nd and / or Pr, H includes Tb and / or Dy, T is Cu or Al, 30≤a≤45, 30≤b≤45, 5≤c≤20, 5≤d≤20, in the step of hot-press sintering, the temperature is 600-750 DEG C, the time is 3-20 min, in the step of hot deformation treatment, the temperature is 650-850 DEG C, the deformation amount is 65-75%, and the time is 3-10 min.

2. The method of producing a neodymium-iron-boron magnet according to claim 1, characterized by, The mass fraction of the alloy powder in the mixed powder is 1-10%.

3. The method of producing a neodymium-iron-boron magnet according to claim 1, characterized by, The particle size of the alloy powder is 30-200 μm.

4. The method of producing a neodymium-iron-boron magnet according to any one of claims 1 to 3, characterized in that, The Nd-Fe-B preform magnetic powder has a molecular formula of L x Fe 100-x-y-z M y B z wherein L is Nd or a mixture of Nd and Pr, M includes at least one of Co, Ga, Cu or Al, 12≤x≤15, 0≤y≤8, and 4≤z≤8.

5. The method of producing a neodymium-iron-boron magnet according to any one of claims 1 to 3, characterized in that, The particle size of the neodymium-iron-boron pre-made magnetic powder is 40-100 μm.

6. A neodymium-iron-boron magnet, characterized by The neodymium-iron-boron magnet is prepared by the method as claimed in any one of claims 1-5.

7. The neodymium-iron-boron magnet according to claim 6, characterized in that The grain size of the neodymium-iron-boron magnet is 150-350 nm.

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