High-coercivity low-temperature-coefficient neodymium-iron-boron magnet, preparation method and application thereof

Abstract

The application discloses a high-coercivity low-temperature-coefficient neodymium-iron-boron magnet and a preparation method and application thereof. The preparation method comprises the following steps: mixing a first alloy, a second alloy, a third alloy and a fourth alloy, and performing orientation compression, sintering and tempering heat treatment to obtain the high-coercivity low-temperature-coefficient neodymium-iron-boron magnet; wherein the first alloy is a Co-containing rare earth alloy. The preparation method can utilize the temperature compensation effect of heavy rare earth to improve the magnet saturation magnetization intensity within a certain temperature range, and the synergistic effect of Co elements is combined to obtain the high-coercivity low-temperature-coefficient neodymium-iron-boron magnet, which can meet the strict requirements of high-precision instrument and equipment field on the service stability of the neodymium-iron-boron material.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic materials, and in particular relates to a high-coercivity, low-temperature-coefficient neodymium iron boron magnet, and a preparation method and application thereof. Background Art

[0002] Neodymium iron boron (Nd-Fe-B) rare earth permanent magnets, as key functional materials, can provide a strong, sustained magnetic field for target devices. However, their Curie temperature is relatively low (Tc is between 320-380°C) and their temperature coefficient is relatively high (a(Br)≈-0.1% / °C, β(Hcj)≈-0.7% / °C in the range of 20-100°C). As service life increases and due to temperature rise and aging, the magnetic field strength provided by the magnet will fluctuate. This poor temperature stability significantly limits its expanded application in high-tech fields requiring precise control, such as precision servo motors, high-precision instrumentation, and sensors. Therefore, improving the temperature stability of NdFeB magnets has become a focus of industry attention.

[0003] The conventional method to improve the temperature stability of NdFeB magnets is to add a large amount of cobalt (Co) during the process of magnet preparation and melting. The technical principle is that Co can partially replace Fe in the NdFeB lattice and preferentially occupy the 8j2 and 16k2 crystal positions in the 2:14:1 phase. The 8j2 position has the most Fe atoms adjacent to it, and the exchange interaction between Co-Co and Co-Fe atomic pairs is stronger than that between Fe-Fe atomic pairs. Theoretical calculations show that Nd2Co 14 The 3d-3d electron exchange interaction of phase B is about Nd2Fe 14 The strong interatomic exchange interaction is beneficial to the temperature stability of the material. However, it has been found that with the replacement of Fe by Co, although the Curie temperature and remanence temperature coefficient of the magnet are improved, a large amount of Co-rich impurities precipitate at the grain boundaries, such as 1:2 type, 1:3 type, 1:4:1 type and many other soft magnetic phases, reducing the proportion of the main phase and deteriorating the microstructure of the magnet. At the same time, the soft magnetic impurities dilute the non-magnetic phase at the grain boundaries, resulting in a weakened magnetic isolation between grains, ultimately causing serious damage to key magnetic performance parameters such as the coercive force and magnetic energy product of the magnet. Therefore, providing a high coercive force and low temperature coefficient NdFeB magnet that suppresses the formation of Co-type impurities is an urgent problem to be solved. Summary of the Invention

[0004] The main purpose of the present invention is to provide a high coercive force and low temperature coefficient NdFeB magnet and its preparation method and application, which can promote the full utilization of rare earth resources and enable the prepared NdFeB to meet the stringent requirements of the field of high-precision instruments and equipment for the service stability of magnetic functional devices.

[0005] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0006] An embodiment of the present invention provides a method for preparing a high coercive force and low temperature coefficient neodymium iron boron magnet, which comprises:

[0007] The first alloy, the second alloy, the third alloy and the fourth alloy are mixed and subjected to orientation pressing, sintering and tempering heat treatment to obtain a high coercive force and low temperature coefficient NdFeB magnet; wherein the first alloy is a Co-containing rare earth alloy.

[0008] The embodiment of the present invention also provides a high coercive force and low temperature coefficient neodymium iron boron magnet prepared by the above preparation method.

[0009] The embodiment of the present invention further provides the application of the aforementioned high coercive force and low temperature coefficient NdFeB magnet in the fields of precision servo motors, high-precision instruments and meters, or high-precision sensors.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] (1) The present invention utilizes the synergistic effect of multiple elements to avoid the formation of Co-rich intergranular phase caused by excessive Co element, while making full use of heavy rare earth elements to avoid the decrease of remanence and the increase of cost;

[0012] (2) The four main phases provided by the present invention can be used to prepare magnets with high remanence, high coercivity, low remanence and coercivity temperature coefficient, which can meet the stringent requirements of high-precision instrumentation for the service stability of magnetic functional devices;

[0013] (3) The present invention facilitates the interdiffusion behavior between different elements of multiple components during the sintering process by designing different particle size ratios of multiple components and combining them with long-term low-temperature sintering, and can produce high-stability and high-performance magnets with uniform composition;

[0014] (4) The present invention achieves outstanding and stable crystal diffusion effects by designing a magnet with multiple main phases and uniform structure and composition, which can meet the requirements of grain boundary diffusion for large-sized magnets;

[0015] (5) The method provided by the present invention is simple and easy to implement, can be prepared in large quantities, and is suitable for industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1It is a schematic diagram of the microstructure of a high coercive force and low temperature coefficient NdFeB magnet in a typical embodiment of the present invention. DETAILED DESCRIPTION

[0018] In view of the defects of the prior art, the inventors of this case have proposed the technical solution of the present invention after long-term research and extensive practice. The present invention mixes a variety of NdFeB main phase powders, accurately designs the proportions of different main phases and powder particle sizes, promotes the mutual diffusion of different elements through long-term low-temperature sintering, utilizes the synergistic effect between different elements, and regulates the microstructure of the magnet. It can effectively inhibit the formation of high-Co magnet impurity phases, reduce the use of heavy rare earths, improve the utilization rate of heavy rare earths, and obtain low-cost, high-performance and high-stability NdFeB magnets. It can also be applied to grain boundary diffusion of large-size magnets, is simple and easy to operate, and is convenient for industrial production.

[0019] The technical solution of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] Specifically, as one aspect of the technical solution of the present invention, a method for preparing a high coercive force and low temperature coefficient neodymium iron boron magnet includes:

[0021] The first alloy, the second alloy, the third alloy and the fourth alloy are mixed and subjected to orientation pressing, sintering and tempering heat treatment to obtain a high coercive force and low temperature coefficient NdFeB magnet; wherein the first alloy is a Co-containing rare earth alloy.

[0022] In some preferred embodiments, the chemical formula of the first alloy is as shown in Formula (I):

[0023] RE1 a Co b M c Fe 100-a-b-c-d B d Formula (I)

[0024] Among them, RE1 is selected from Pr and / or Nd; M is selected from any one or more combinations of Cu, Al, Ga, Zr, Ti, and Nb; a, b, c, and d are the mass percentages of the corresponding elements, and satisfy 29≤a≤31.5, 30≤b≤70, 0≤c≤2, and 0.80≤d≤1.1.

[0025] Specifically, the first alloy of the present invention provides the magnet with a high Co component to reduce the remanence temperature coefficient α of the magnet.

[0026] In some preferred embodiments, the chemical formula of the second alloy is as shown in Formula (II):

[0027] RE2 e N f Fe 100-e-f-g B g Formula (II)

[0028] Wherein, RE2 is selected from Pr and / or Nd, N is selected from any one or more combinations of Cu, Al, Ga, Zr, Ti, and Nb; e, f, and g are the mass percentages of the corresponding elements, and satisfy 28≤e≤30, 0≤f≤2, and 0.80≤g≤1.1.

[0029] Specifically, the second alloy in the present invention provides the magnet with a high Ms to ensure that the magnet has high remanence and magnetic energy product.

[0030] In some preferred embodiments, the general chemical formula of the third alloy is as shown in formula (III):

[0031] RE3 h P i Fe 100-h-i-j B j Formula (III)

[0032] Among them, RE3 is selected from any one or more combinations of Dy, Tb, Ho, Gd, Pr, and Nd; P is selected from any one or more combinations of Cu, Al, Ga, Zr, Ti, and Nb; h, i, and j are the mass percentages of the corresponding elements, and satisfy 29.5≤h≤32, 0≤i≤2, and 0.80≤j≤1.1.

[0033] Specifically, the third alloy of the present invention provides high H A To ensure that the magnet has high coercivity.

[0034] In some preferred embodiments, the general chemical formula of the fourth alloy is as shown in Formula (IV):

[0035] RE4 x Q y Fe 100-x-y-z B z Formula (IV)

[0036] Among them, RE4 is a combination of any one or more of Y, Pr, and Nd; Q is selected from a combination of any one or more of Cu, Al, Ga, Zr, Ti, and Nb; x, y, and z are the mass percentages of the corresponding elements, and satisfy 28≤x≤29, 0≤y≤2, and 0.88≤z≤1.1.

[0037] Specifically, the fourth alloy of the present invention ensures that the magnet has a low coercive force temperature coefficient β.

[0038] In some preferred embodiments, the average particle size of the first alloy is 1.8 to 3.5 mm.

[0039] Furthermore, the average particle size of the first alloy is 2.8 to 3.5 μm.

[0040] In some preferred embodiments, the average particle size of the second alloy is 1.8 to 3.5 mm.

[0041] In some preferred embodiments, the average particle size of the third alloy is 1.8 to 3.5 mm.

[0042] Furthermore, the average particle size of the third alloy is 2.2-2.8 μm.

[0043] In some preferred embodiments, the average particle size of the fourth alloy is 1.8 to 3.5 mm.

[0044] Furthermore, the average particle size of the fourth alloy is 1.8 to 2.2 μm.

[0045] In some preferred embodiments, the orientation magnetic field used in the orientation pressing process is above 2T.

[0046] In some preferred embodiments, the temperature used in the sintering process is 950-1050°C, the time is 3-12 hours, and the vacuum degree is not less than 5×10 -3 pa.

[0047] In some preferred embodiments, the tempering heat treatment includes a primary tempering treatment and a secondary tempering treatment.

[0048] Furthermore, the temperature of the first-stage tempering treatment is 820-950°C, the time is 1-5 hours, and the vacuum degree is not less than 5×10 -3 Pa.

[0049] Furthermore, the temperature of the secondary tempering treatment is 450-600°C, the time is 1-5 hours, and the vacuum degree is not less than 5×10 -3 pa.

[0050] In some preferred embodiments, the mass ratio of the first alloy, the second alloy, the third alloy and the fourth alloy is 20-60:10-40:10-40:10-40.

[0051] In some preferred embodiments, the preparation method specifically comprises:

[0052] Smelting the first alloy, the second alloy, the third alloy, and the fourth alloy according to the ratio of each element respectively to obtain a first rapid-setting alloy sheet, a second rapid-setting alloy sheet, a third rapid-setting alloy sheet, and a fourth rapid-setting alloy sheet;

[0053] The first, second, third and fourth quick-setting alloy sheets are subjected to air flow milling and crushing treatment respectively to obtain first, second, third and fourth alloy powders.

[0054] In some more specific embodiments, the method for preparing the high coercivity and low temperature coefficient NdFeB magnet comprises:

[0055] First configure the weight ratio to RE1 a Co b M c Fe 100-a-b-c-d B d 、RE2 e N f Fe 100-e-f-g B g 、RE3 h P i Fe 100-h-i-j B j 、RE4 x Q y Fe 100-x-y-z B z The raw materials are melted into quick-setting alloy flakes, and then the four quick-setting alloy flakes are crushed into air flow milled powders; the four alloy powders are evenly mixed and then prepared into magnet blanks through a powder molding step for vacuum sintering and tempering heat treatment; finally, the tempered magnets are subjected to grain boundary diffusion treatment and tempering treatment.

[0056] Furthermore, the composition of the quick-setting alloy sheet is as follows:

[0057] RE1 a Co b M c Fe 100-a-b-c-d B d : Wherein, a, b, c, d are the values ​​of the weight ratio of each element multiplied by 100, 29≤a≤31.5, 30≤b≤70, 0≤c≤2, 0.80≤d≤1.1; RE1 is one or two of Pr and Nd; M is one or more of Cu, Al, Ga, Zr, Ti, Nb; this component provides the magnet with a high Co component to reduce the remanence temperature coefficient α of the magnet.

[0058] RE2 e N f Fe 100-e-f-g B g: Wherein, e, f, and g are the values ​​of the weight ratio of their respective elements multiplied by 100, 28≤e≤30, 0≤f≤2, 0.80≤g≤1.1; RE2 is one or more of Pr and Nd, and N is one or more of Cu, Al, Ga, Zr, Ti, and Nb. This component provides high Ms for the magnet to ensure that the magnet has high remanence and magnetic energy product.

[0059] RE3 h P i Fe 100-h-i-j B j :wherein, h, i, j are the values ​​of the mass ratio of each element multiplied by 100, 29.5≤h≤32, 0≤i≤2, 0.80≤j≤1.1; RE3 is one or more of Dy, Tb, Ho, Gd, Pr, Nd, and P is one or more of Cu, Al, Ga, Zr, Ti, Nb. This component provides high H for the magnet. A To ensure that the magnet has high coercivity.

[0060] RE4 x Q y Fe 100-x-y-z B z : Wherein, x, y, and z are the values ​​of the weight ratio of their respective elements multiplied by 100, 28≤x≤29, 0≤y≤2, 0.88≤z≤1.1; RE4 is one or more of Y, Pr, and Nd, and Q is one or more of Cu, Al, Ga, Zr, Ti, and Nb. This component ensures that the magnet has a low coercive force temperature coefficient β.

[0061] Furthermore, the average particle size of the jet mill powder is between 1.5 and 3.5 mm.

[0062] Furthermore, the RE1 a Co b M c Fe 100-a-b-c-d B d The average particle size of the jet mill powder is between 2.8 and 3.5 μm; RE3 h P i Fe 100-h-i-j B j The average particle size of the jet mill powder is between 2.2 and 2.8 μm; RE4 x Q y Fe 100-x-y-z B z The average particle size of the jet milled powder is between 1.8 and 2.2 μm. The different particle sizes of powders with different components are beneficial to the mutual diffusion of different elements and the homogenization of the composition during the sintering process.

[0063] Furthermore, the weight ratios of the four powders are as follows: 20-60: 10-40: 10-40: 10-40.

[0064] The preparation method provided by the present invention can utilize the temperature compensation effect of heavy rare earth to improve the saturation magnetization intensity of the magnet within a certain temperature range. Combined with the synergistic effect of the Co element, a NdFeB magnet with high coercivity and low temperature coefficient is obtained, which can meet the stringent requirements of the high-precision instrument and equipment field on the service stability of NdFeB materials.

[0065] Another aspect of the embodiments of the present invention further provides a high coercive force and low temperature coefficient NdFeB magnet prepared by the aforementioned preparation method.

[0066] In some preferred embodiments, the microstructure diagram of the high coercive force and low temperature coefficient NdFeB magnet of the present invention is as follows: Figure 1 shown.

[0067] Another aspect of the embodiments of the present invention further provides applications of the aforementioned high coercive force and low temperature coefficient NdFeB magnet in the fields of precision servo motors, high-precision instruments and meters, or high-precision sensors.

[0068] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0069] Unless otherwise specified, the experimental materials used in the following examples can be purchased from conventional biochemical reagent companies.

[0070] Example 1

[0071] The composition is (Pr 20 Nd 80 ) 30 Co 50 Cu 0.2 Al 0.3 Ga 0.3 Fe 18.28 B 0.92 、(Pr 20 Nd 80 ) 29.8 Cu 0.2 Al 0.1 Ga 0.1 Zr 0.1 Fe 68.77 B 0.95 、Nd 26 DYNAMIC 0.2 Al 0.3 Ga 0.2 Ti0.3 Fe 68.1 B 0.9 and (Pr 20 Nd 80 ) 23 Y6C 0.2 Al 0.2 Ga 0.2 Zr 0.2 Fe 69.22 B 0.98 The four raw materials are melted into quick-setting alloy flakes, which are then crushed by hydrogen and jet milled to produce jet mill powder with an average particle size of 1.8-3.5 μm (where (Pr 20 Nd 80 ) 30 Co 50 Cu 0.2 A 0.3 Ga 0.3 Fe 18.28 B 0.92 The average particle size is 2.9 μm, (Pr 20 Nd 80 ) 29.8 Cu 0.2 Al 0.1 Ga 0.1 Zr 0.1 Fe 68.77 B 0.95 The average particle size is 2.5 μm, Nd 26 DYNAMIC 0.2 Al 0.3 Ga 0.2 Ti 0.3 Fe 68.1 B 0.9 The average particle size is 2.3 μm, (Pr 20 Nd 80 ) 23 Y6C 0.2 Al 0.2 Ga 0.2 Zr 0.2 Fe 69.22 B 0.98 The average particle size is 1.9 μm); the four powders are then uniformly mixed in a mass ratio of 30:30:20:20, and the mixed powder is then oriented pressed and isostatically pressed under a 2 T magnetic field to prepare a magnet blank; the blank is placed in a vacuum heat treatment furnace and sintered at 1010°C for 5 hours, and then tempered at 900°C and 500°C for 2 hours respectively.

[0072] Comparative Example 1

[0073] In order to compare the advantages of the present invention, the same components as those in the embodiment are mixed in proportion (Pr 20 Nd80 ) 27.7 4Co 15 Dy 0.8 Y 0.12 Cu 0.2 Al 0.22 Ga 0.2 Zr 0.07 Ti 0.06 Fe 53.567 B 0.937 The raw materials were prepared into magnets according to the same steps (melting, powder making, molding, sintering, tempering). The magnetic properties and magnetothermal stability of the two magnets were tested. The relevant test results are as follows:

[0074]

[0075] Example 2:

[0076] The composition is (Pr 20 Nd 80 ) 29.5 Co 60 Cu 0.4 Al 0.3 Ga 0.3 Fe 8.56 B 0.94 、(Pr 20 Nd 80 ) 30 Cu 0.2 Al 0.2 Ga 0.1 Zr 0.1 Fe 68.45 B 0.95 、Nd 26 6CU 0.25 Al 0.25 Ga 0.25 Ti 0.25 Fe 66.1 B 0.9 and (Pr 20 Nd 80 ) 20 Y8 0.25 Al 0.25 Ga 0.25 Zr 0.25 Fe 70.07 B 0.93 The four raw materials are melted into quick-setting alloy flakes, which are then crushed by hydrogen and jet milled to produce jet mill powder with an average particle size of 1.8-3.5 μm (where (Pr 20 Nd 80 ) 29.5 Co 60 Cu 0.4 Al 0.3 Ga0.3 Fe 8.56 B 0.94 The average particle size is 3.2 μm, (Pr 20 Nd 80 ) 30 Cu 0.2 Al 0.2 Ga 0.1 Zr 0.1 Fe 68.45 B 0.95 The average particle size is 2.6 μm, Nd 26 6CU 0.25 Al 0.25 Ga 0.2 5Ti 0.25 Fe 66.1 B 0.9 The average particle size is 2.4 μm, (Pr 20 Nd 80 ) 20 Y8 0.25 Al 0.25 Ga 0.25 Zr 0.25 Fe 70.07 B 0.93 The average particle size is 2.0 μm); the four powders are then uniformly mixed in a mass ratio of 10:40:20:30, and the mixed powder is then subjected to orientation pressing and isostatic pressing in a 2 T magnetic field to prepare a magnet blank; the blank is placed in a vacuum heat treatment furnace and sintered at 980°C for 8 hours, and then continues to be tempered at 900°C and 500°C for 2 hours respectively.

[0077] Comparative Example 2

[0078] In order to compare the advantages of the present invention, use (Pr 20 Nd 80 ) 30 Cu 0.2 Al 0.2 Ga 0.1 Zr 0.1 Fe 68.45 B 0.95 、Nd 26 6CU 0.25 Al 0.25 Ga 0.25 Ti 0.25 Fe 66.1 B 0.9 and (Pr 20 Nd 80 ) 20 Y8 0.25 Al 0.25 Ga 0.25 Zr 0.25 Fe70.07 B 0.93 The raw materials were prepared into magnets according to the same steps (melting, powdering, molding, sintering, and tempering). The three powders were mixed in a mass ratio of 40:30:30. The magnetic properties and magnetothermal stability of the two magnets were tested. The relevant test results are as follows:

[0079]

[0080] Example 3:

[0081] The component is Pr 29.5 Co 40 Cu 0.3 Al 0.4 Ga 0.3 Fe 28.56 B 0.94 、(Pr 20 Nd 80 ) 30 Cu 0.2 Al 0.2 Ga 0.1 Zr 0.1 Fe 68.4 5B 0.95 、Pr 27 DYNAMIC 0.25 Al 0.25 Ga 0.25 Ti 0.25 Fe 67.08 B 0.92 and Pr 22 Y7U 0.25 Al 0.25 Ga 0.25 Zr 0.25 Fe 69.06 B 0.94 The four raw materials are melted into quick-setting alloy flakes, which are then crushed by hydrogen and jet milled to produce jet mill powder with an average particle size of 1.8-3.5 μm (Pr 29.5 Co 40 Cu 0.3 Al 0.4 Ga 0.3 Fe 28.56 B 0.94 The average particle size is 3.3 μm, (Pr 20 Nd 80 ) 30 Cu 0.2 Al 0.2 Ga 0.1 Zr 0.1 Fe 68.45 B 0.95 The average particle size is 2.6 μm, Pr 27 DYNAMIC 0.25Al 0.25 Ga 0.25 Ti 0.25 Fe 67.08 B 0.92 The average particle size is 2.1 μm, Pr 22 Y7U 0.25 Al 0.25 Ga 0.25 Zr 0.25 Fe 69.06 B 0.94 The average particle size is 1.8μm); the four powders are then uniformly mixed in a mass ratio of 20:30:35:25, and the mixed powder is then subjected to orientation pressing and isostatic pressing in a 2T magnetic field to prepare a magnet blank; the blank is placed in a vacuum heat treatment furnace and sintered at 1000℃ for 7h, and then tempered at 900℃ and 500℃ for 2h respectively, and then processed into a cylindrical magnet with a diameter of 7mm and a height of 8mm; a diffusion source with the composition of TbHx is then used to perform grain boundary diffusion on the processed magnet at a diffusion temperature of 900℃ for 10h; after the diffusion is completed, the magnet is tempered at 500℃ for 2h and then cooled to room temperature. After the tempering is completed, the magnetic properties of the magnet are tested.

[0082] Comparative Example 3

[0083] In order to compare the advantages of the present invention, the Pr 29.5 Co 40 Cu 0.3 Al 0.4 Ga 0.3 Fe 28.56 B 0.94 、Pr 27 DYNAMIC 0.25 Al 0.25 Ga 0.25 Ti 0.25 Fe 67.08 B 0.92 and Pr 22 Y7U 0.25 Al 0.25 Ga 0.25 Zr 0.25 Fe 69.06 B 0.94 The three raw materials were prepared into magnets using the same steps (melting, powdering, molding, sintering, tempering, grain boundary diffusion, and tempering). The three powders were mixed in a mass ratio of 30:40:30. The magnetic properties and magnetothermal stability of the two magnets were tested. The relevant test results are as follows:

[0084]

[0085] Example 4:

[0086] The composition is (Pr20 Nd 80 ) 29.5 Co 50 Cu 0.2 Al 0.2 Ga 0.2 Fe 18.96 B 0.94 、(Pr 20 Nd 80 ) 30 Cu 0.2 Al 0.2 Ga 0.1 Zr 0.1 Fe 68.45 B 0.95 、Pr 27 Tb5Cu 0.2 Al 0.2 Ga 0.2 Nb 0.2 Ti 0.2 Fe 66.08 B 0.92 and Pr 19 Y9C 0.25 Al 0.25 Ga 0.25 Zr 0.25 Fe 70.06 B 0.94 The four raw materials are melted into quick-setting alloy flakes, which are then crushed by hydrogen and jet milled to produce jet mill powder with an average particle size of 1.8-3.5 μm (where (Pr 20 Nd 80 ) 29.5 Co 50 Cu 0.2 Al 0.2 Ga 0.2 Fe 18.96 B 0.94 The average particle size is 3.0 μm, (Pr 20 Nd 80 ) 30 Cu 0.2 Al 0.2 Ga 0.1 Zr 0.1 Fe 68.45 B 0.95 The average particle size is 2.7 μm, Pr 27 Tb5Cu 0.2 Al 0.2 Ga 0.2 Nb 0.2 Ti 0.2 Fe 66.08 B 0.92 The average particle size is 2.4 μm, Pr 19 Y9C 0.25Al 0.25 Ga 0.25 Zr 0.25 Fe 70.06 B 0.94 The average particle size is 2.0 μm); the four powders are then uniformly mixed in a mass ratio of 25:25:20:30, and the mixed powder is then oriented pressed and isostatically pressed under a 2 T magnetic field to prepare a magnet blank; the blank is placed in a vacuum heat treatment furnace and sintered at 990°C for 8 hours, and then tempered at 900°C and 500°C for 2 hours respectively.

[0087] Comparative Example 4

[0088] In order to compare the advantages of the present invention, use (Pr 20 Nd 80 ) 29.5 Co 50 Cu 0.2 Al 0.2 Ga 0.2 Fe 18.96 B 0.94 、(Pr 20 Nd 80 ) 30 Cu 0.2 Al 0.2 Ga 0.1 Zr 0.1 Fe 68.45 B 0.95 The two raw materials were prepared into magnets using the same steps (melting, powdering, molding, sintering, tempering, grain boundary diffusion, and tempering). The two powders were mixed in a 50:50 mass ratio. The magnetic properties and magnetothermal stability of the two magnets were tested. The relevant test results are as follows:

[0089]

[0090] Comparative Example 5:

[0091] This embodiment is the same as embodiment 1. In order to compare the advantages of the present invention, four raw materials with the same composition are used and the same steps (melting, powdering (where (Pr 20 Nc 80 ) 30 Co 50 Cu 0.2 Al 0.3 Ga 0.3 Fe 18.28 B 0.92 The average particle size is 1.9 μm, (Pr 20 Nd 80 ) 29.8 Cu 0.2 Al 0.1 Ga 0.1 Zr0.1 Fe 68.77 B 0.95 The average particle size is 2.5 μm, Nd 26 DYNAMIC 0.2 Al 0.3 Ga 0.2 Ti 0.3 Fe 68.1 B 0.9 The average particle size is 3.4 μm, (Pr 20 Nd 80 ) 23 Y6C 0.2 Al 0.2 Ga 0.2 Zr 0.2 Fe 69.22 B 0.98 The average particle size is 2.8μm), powder mixing, molding, sintering, and tempering are used to prepare magnets. The magnetic properties and magnetic thermal stability of the two magnets were tested, and the relevant test results are as follows:

[0092]

[0093] Comparative Example 6:

[0094] This embodiment is the same as embodiment 2. In order to compare the advantages of the present invention, four raw materials with the same composition are used and the same steps (melting, powdering (where (Pr 20 Nd 80 ) 29.5 Co 60 Cu 0.4 Al 0.3 Ga 0.3 Fe 8.56 B 0.94 、(Pr 20 Nd 80 ) 30 Cu 0.2 Al 0.2 Ga 0.1 Zr 0.1 Fe 68.45 B 0.95 、Nd 26 6CU 0.25 Al 0.25 Ga 0.25 Ti 0.25 Fe 66.1 B 0.9 and (Pr 20 Nd 80 ) 20 Y8 0.25 Al 0.25 Ga 0.25 Zr 0.25 Fe70.07 B 0.93 The average particle size of both materials is 3.0 μm), powder mixing, molding, sintering, and tempering are performed to prepare magnets. The magnetic properties and magnetothermal stability of the two magnets were tested, and the relevant test results are as follows:

[0095]

[0096] Comparative Example 7:

[0097] This example is similar to Example 3. To compare the advantages of the present invention, magnets were prepared using four raw materials with the same composition and following the same steps (melting, powder preparation, powder mixing, molding, sintering (sintering at 1070°C for 4 hours), and tempering). The magnetic properties and magnetothermal stability of the two magnets were tested. The relevant test results are as follows:

[0098]

[0099] Example 5:

[0100] The components and steps for preparing the magnets of this embodiment and the comparative example are the same as those of embodiment 4. In order to compare the advantages of the present invention in being applicable to grain boundary diffusion of large-sized magnets, the magnet obtained in embodiment 4 is used as the original substrate 1 and processed into a cylindrical magnet with a diameter of 8 mm and a height of 13 mm, which is magnet 1. The magnet obtained in embodiment 4 is processed into a cylindrical magnet with a diameter of 8 mm and a height of 5 mm, which is magnet 2. DyHx powder is coated on the two magnets for grain boundary diffusion. A commercial magnet with similar performance to the original substrate 1 is used as the original substrate 2 and processed into a cylindrical magnet with a diameter of 8 mm and a height of 13 mm, which is magnet 3, and a cylindrical magnet with a diameter of 8 mm and a height of 5 mm, which is magnet 4. The diffusion temperature is 900°C, the time is 10 h, and the vacuum degree is less than 1×10 -3 After diffusion, the magnets were tempered at 500°C for 2 hours. The magnetic properties and magnetothermal stability of the two magnets were tested. The relevant test results are as follows:

[0101]

[0102]

[0103] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0104] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical variations made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a high coercive force and low temperature coefficient neodymium iron boron magnet, characterized in that: include: The first alloy, the second alloy, the third alloy and the fourth alloy are mixed and subjected to orientation pressing, sintering and tempering heat treatment to produce a high coercive force and low temperature coefficient NdFeB magnet; wherein the first alloy is a rare earth alloy containing Co; and the mass ratio of the first alloy, the second alloy, the third alloy and the fourth alloy is 20-60:10-40:10-40:10-40; The general chemical formula of the first alloy is shown in formula (I): RE1 a Co b M c Fe 100-a-b-c-d B d Formula (I) Wherein, RE1 is selected from Pr and / or Nd; M is selected from any one or more combinations of Cu, Al, Ga, Zr, Ti, and Nb; a, b, c, and d are the mass percentages of the corresponding elements, and satisfy 29≤a≤31.5, 30≤b≤70, 0≤c≤2, and 0.80≤d≤1.1; The general chemical formula of the second alloy is shown in formula (II): RE2 e N f Fe 100-e-f-g B g Formula (II) wherein RE2 is selected from Pr and / or Nd, and N is selected from any one or more combinations of Cu, Al, Ga, Zr, Ti, and Nb; e, f, and g are the mass percentages of the corresponding elements, and satisfy 28≤e≤30, 0≤f≤2, and 0.80≤g≤1.1; The general chemical formula of the third alloy is shown in formula (III): RE3 h P i Fe 100-h-i-j B j Formula (III) Wherein, RE3 is selected from any one or more combinations of Dy, Tb, Ho, Gd, Pr, and Nd, and RE3 contains at least any one or more combinations of Dy, Tb, Ho, and Gd; P is selected from any one or more combinations of Cu, Al, Ga, Zr, Ti, and Nb; h, i, and j are the mass percentages of the corresponding elements, and satisfy 29.5≤h≤32, 0≤i≤2, and 0.80≤j≤1.1; The general chemical formula of the fourth alloy is shown in formula (IV): RE4 x Q y Fe 100-x-y-z B z Formula (IV) RE4 is any one or more combinations of Y, Pr, and Nd, and RE4 contains at least Y; Q is any one or more combinations of Cu, Al, Ga, Zr, Ti, and Nb; x, y, and z are the mass percentages of the corresponding elements, and satisfy 28≤x≤29, 0≤y≤2, and 0.88≤z≤1.1; The average particle size of the first alloy is 2.8 to 3.5 μm; the average particle size of the second alloy is 1.8 to 3.5 mm; the average particle size of the third alloy is 2.2 to 2.8 μm; and the average particle size of the fourth alloy is 1.8 to 2.2 μm.

2. The preparation method according to claim 1, wherein: The orientation magnetic field used in the orientation pressing process is above 2T.

3. The preparation method according to claim 1, wherein: The temperature used in the sintering process is 950-1050°C, the time is 3-12 hours, and the vacuum degree is not less than 5×10 -3 Pa.

4. The preparation method according to claim 1, wherein: The tempering heat treatment includes a primary tempering treatment and a secondary tempering treatment.

5. The preparation method according to claim 4, characterized in that: The temperature of the first-stage tempering treatment is 820-950°C, the time is 1-5 hours, and the vacuum degree is not less than 5×10 -3 Pa.

6. The preparation method according to claim 4, characterized in that: The temperature of the secondary tempering treatment is 450-600°C, the time is 1-5 hours, and the vacuum degree is not less than 5×10 -3 Pa.

7. The preparation method according to claim 1, characterized in that Specifically include: Smelting the first alloy, the second alloy, the third alloy, and the fourth alloy according to the ratio of each element respectively to obtain a first rapid-setting alloy sheet, a second rapid-setting alloy sheet, a third rapid-setting alloy sheet, and a fourth rapid-setting alloy sheet; The first, second, third and fourth quick-setting alloy sheets are subjected to air flow milling and crushing treatment respectively to obtain first, second, third and fourth alloy powders.

8. A high coercive force and low temperature coefficient neodymium iron boron magnet prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the high coercive force and low temperature coefficient NdFeB magnet according to claim 8 in the fields of precision servo motors, high-precision instruments and meters, or high-precision sensors.

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