Preparation method of neodymium-iron-boron magnet based on matching of powder particle size and main phase grain size

Abstract

The invention belongs to the technical field of neodymium-iron-boron magnets, and relates to a neodymium-iron-boron magnet preparation method based on matching of powder particle size and main phase grain size, which comprises the following steps: (1) preparing a neodymium-iron-boron alloy rapid hardening sheet by adopting a rapid hardening process; the main phase is a columnar crystal, and the average size of the short axis of the main phase is 2.1-3.4 microns; (2) sequentially carrying out hydrogen decrepitation and jet milling on the neodymium-iron-boron alloy rapid hardening sheet to obtain neodymium-iron-boron powder; the difference value between the D50 particle size of the neodymium iron boron powder and the average size of the short axis of the main phase is less than or equal to 1 mu m; and (3) carrying out orientation molding, compression molding, sintering treatment and tempering treatment on the neodymium-iron-boron powder to obtain the high-performance sintered neodymium-iron-boron magnet. According to the method, the average size of the main phase short axis in the rapid hardening sheet is effectively matched with the D50 particle size value of the neodymium iron boron powder by accurately controlling the rapid hardening and powder manufacturing process, it is ensured that a complete and uniform rare earth-rich phase coating layer is formed on the surface of the neodymium iron boron particle, and the microstructure is optimized from the source.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of neodymium-iron-boron magnets, and relates to a preparation method of a neodymium-iron-boron magnet based on matching of powder particle size and main phase grain size. BACKGROUND

[0002] Sintered neodymium-iron-boron permanent magnets have been widely used in new energy vehicles, wind power generation, energy-saving motors and electronic consumer goods due to their excellent magnetic properties. In order to meet the needs of high-performance application scenarios, researchers continue to explore technical paths to improve the residual magnetism (Br), coercivity (Hcj) and magnetic energy product ((BH)max) of the magnets. Currently, optimizing alloy composition, controlling sintering process and improving grain boundary phase distribution are the three core directions to improve the comprehensive performance of the magnets.

[0003] In the raw material preparation link, the rapid solidification and ribbon casting process has become the mainstream preparation method for high-quality neodymium-iron-boron magnetic powder due to its advantages of rapid solidification of alloy melt, refinement of main phase grains and improvement of organizational uniformity. Specifically, the columnar crystals and rare earth-rich phases in the rapid solidification ribbon are in an overlapping distribution: during the hydrogen breaking process, the rare earth-rich phase expands due to hydrogen absorption, causing intergranular fracture, which not only forms a rare earth-rich phase coating on the surface of coarse powder particles, but also generates independent blocky rare earth-rich phases; after entering the jet mill stage, if the main phase grains undergo transgranular fracture, the main phase fracture surface is exposed, and the rare earth-rich phase is easily stripped or dispersed, ultimately significantly reducing the amount of rare earth-rich phase coating on the surface of fine powder particles, and thus adversely affecting the residual magnetism (Br) and coercivity (Hcj) of the magnet.

[0004] However, the traditional jet milling process lacks specificity in controlling the particle size and morphology of the powder, and some powders cannot form effective grain boundary rare earth-rich phase coatings, which can weaken the magnetic isolation effect between the main phases during the sintering process, ultimately leading to a decrease in the coercivity (Hcj) of the magnet.

[0005] Chinese patent application (publication number: CN119495482A) discloses a neodymium-iron-boron rapid solidification casting ribbon, which is composed of Re2Fe 14 B main phase and intergranular Re-rich phase, and does not contain α-Fe phase; the main phase has a columnar crystal morphology, the width of the columnar crystal is 2.5-3.7 μm, the two sides of the columnar crystal are distributed with dendritic crystals, the width of the dendritic crystal is close to that of the columnar crystal, the two sides of the columnar crystal and the dendritic crystal are attached with Re-rich phases, and the Re-rich phases are uniformly distributed along the columnar crystal and the dendritic crystal. By controlling the microstructure of the neodymium-iron-boron rapid solidification casting ribbon, the yield of the neodymium-iron-boron magnetic powder is improved, and the normal distribution of the particle size of the neodymium-iron-boron magnetic powder is improved, but the main phase transgranular fracture may still occur in the subsequent powdering process, leading to exposure of the main phase fracture surface, stripping of the rare earth-rich phase, etc., which affects the magnetic properties.

[0006] The Chinese patent application (publication number: CN106165026A) discloses an R-T-B alloy powder, and the ratio of the long diameter a to the short diameter b is a / b, and the ratio of the circumference L to the equivalent circle diameter d is L / d, and the number ratio of the powder satisfying the condition of L / d≤5.39-1.07(a / b) is more than 20%, wherein the equivalent circle diameter is the diameter of a circle with the same area. The scheme focuses on the optimization of powder morphology, and the powder arc surface is realized by increasing the crushing gas pressure and prolonging the residence time, the energy consumption is increased, the production cycle is reduced, and the industrial production is not conducive.

[0007] Therefore, it is of great significance to develop a preparation method that can realize the accurate matching of powder particle size and main phase grain size, while considering the optimization of particle morphology, to promote the industrial production of high-performance sintered neodymium-iron-boron magnets. SUMMARY

[0008] The purpose of the present application is to solve the above-mentioned problems existing in the prior art, and a preparation method of a neodymium-iron-boron magnet based on the matching of powder particle size and main phase grain size is proposed. By controlling the rapid solidification process and the powder preparation process, the average size of the short axis of the main phase in the rapid solidification piece is matched with the D50 particle size of the neodymium-iron-boron powder, and the values of the two are ensured to be close, thereby improving the performance of the neodymium-iron-boron magnet.

[0009] One purpose of the present application is achieved by the following technical scheme:

[0010] A preparation method of a neodymium-iron-boron magnet based on the matching of powder particle size and main phase grain size, comprising:

[0011] (1) a neodymium-iron-boron alloy rapid solidification piece is prepared by using a rapid solidification process;

[0012] The proportion of the main phase in the neodymium-iron-boron alloy rapid solidification piece is >85%, and the main phase is a columnar crystal, and the average size of the short axis is 2.1-3.4μm;

[0013] (2) the neodymium-iron-boron alloy rapid solidification piece is sequentially subjected to hydrogen crushing and air jet milling to obtain a neodymium-iron-boron powder; the difference between the D50 particle size of the neodymium-iron-boron powder and the average size of the short axis of the main phase in step (1) is ≤1μm;

[0014] (3) the neodymium-iron-boron powder is subjected to orientation forming, compression molding, sintering treatment and tempering treatment to obtain a high-performance sintered neodymium-iron-boron magnet.

[0015] Preferably, the rapid solidification process in step (1) comprises: after the raw materials of the neodymium-iron-boron alloy are prepared according to the component design of the target sintered neodymium-iron-boron magnet, the raw materials are heated and melted to obtain an alloy liquid, the temperature of the alloy liquid is 1430-1490 ℃; the temperature of the alloy liquid is reduced to 1350-1400 ℃, and then the alloy liquid is spun on a copper roller to obtain a neodymium-iron-boron alloy rapid solidification strip.

[0016] Further preferably, the rapid solidification process in step (1) comprises: after the raw materials of the neodymium-iron-boron alloy are prepared, the raw materials are heated and melted in a vacuum environment to obtain an alloy liquid; the temperature of the alloy liquid is 1430-1490 ℃, and the temperature of the alloy liquid is reduced to 1350-1400 ℃ at a rate of 30-70 ℃ / min, and then the alloy liquid is guided to the surface of a copper roller to be spun, wherein the rotating speed of the copper roller is 10-30 r / min, and the cooling rate is 9×10 4 ~ 6×10 5 ℃ / s.

[0017] Further preferably, the chemical formula of the target sintered neodymium-iron-boron magnet, in terms of mass percentage, is RE a B b M c Fe 100-(a+b+c) , wherein RE is a rare earth element, including one or more of Pr, Nd, Dy, Tb, La, Ce, Y, Ho and Gd, M includes one or more of Cu, Al, Ga, Co, Zr and Ti, and 29≤a≤31, 0.91≤b<1.1, 0.5≤c≤4.

[0018] Preferably, the proportion of the main phase in the neodymium-iron-boron alloy rapid solidification strip in step (1) is 88-92%.

[0019] Preferably, the thickness of the neodymium-iron-boron alloy rapid solidification strip in step (1) is 0.15-0.35 mm; wherein the proportion of the neodymium-iron-boron alloy rapid solidification strip with a thickness of 0.20-0.28 mm is ≥70%.

[0020] Further preferably, in the neodymium-iron-boron alloy rapid solidification strip in step (1), the proportion of the neodymium-iron-boron alloy rapid solidification strip with a thickness of 0.20-0.28 mm is ≥90%.

[0021] Preferably, the rare earth-rich phase in the neodymium-iron-boron alloy rapid solidification strip in step (1) is uniformly distributed between the main phases.

[0022] Preferably, the short axis of the main phase in step (1) has a size of 0.8-6.3 μm, an average size of 2.1-3.4 μm, a long axis size of 30-200 μm, and an average size of 140-180 μm.

[0023] Further preferably, the ratio of the average size of the short axis of the main phase to the average size of the long axis of the main phase in step (1) is 1 : (20-100).

[0024] As a preference, the average size of the short axis of the main phase in step (1) is 2.7±0.3 μm.

[0025] Further preferably, the average size of the short axis of the main phase in step (1) is 2.7±0.05 μm.

[0026] As a preference, the hydrogen content in the hydrogen crushing in step (2) is lower than 800 ppm.

[0027] As a preference, the hydrogen crushing in step (2) obtains NdFeB coarse powder, and the D50 of the NdFeB coarse powder is 53±10 μm.

[0028] As a preference, the oxygen content in the jet mill in step (2) is lower than 40 ppm.

[0029] As a preference, the rotating speed of the classification wheel in the jet mill in step (2) is 2000-5000 rpm.

[0030] Further preferably, the rotating speed of the classification wheel in the jet mill is 2700-4000 rpm.

[0031] More preferably, the rotating speed of the classification wheel in the jet mill is 3000-3600 rpm.

[0032] Further preferably, an auxiliary agent is added to the jet mill, and the auxiliary agent comprises one or more of lubricant, antioxidant, dispersant.

[0033] As a preference, the difference between the D50 particle size of the NdFeB powder in step (2) and the average size of the short axis of the main phase in step (1) is ≤0.4 μm.

[0034] Further preferably, the difference between the D50 particle size of the NdFeB powder in step (2) and the average size of the short axis of the main phase in step (1) is <0.1 μm.

[0035] More preferably, the D50 particle size of the NdFeB powder in step (2) is the same as the average size of the short axis of the main phase in step (1).

[0036] As a preference, the ratio of the short diameter to the long diameter of the NdFeB powder in step (2) is (0.5-1) : 1.

[0037] Further preferably, the ratio of the short diameter to the long diameter of the NdFeB powder in step (2) is (0.7-1) : 1.

[0038] Preferably, the ratio of the short diameter to the long diameter of the neodymium-iron-boron powder in step (2) is (0.8-1):1.

[0039] Further preferably, the ratio of the short diameter to the long diameter of the neodymium-iron-boron powder in step (2) is (0.8-1):1.

[0040] More preferably, the ratio of the short diameter to the long diameter of the neodymium-iron-boron powder in step (2) is (0.8-1):1.

[0041] Preferably, the particle size of the neodymium-iron-boron powder in step (2) is 0.1-10 μm, the D10 of the neodymium-iron-boron powder is 0.3-2.35 μm, the D50 of the neodymium-iron-boron powder is 2.7±1 μm, and the D90 of the neodymium-iron-boron powder is 2.1-4.8 μm.

[0042] Further preferably, the D10 of the neodymium-iron-boron powder is 0.8-1.4 μm, the D50 of the neodymium-iron-boron powder is 2.7±0.3 μm, and the D90 of the neodymium-iron-boron powder is 3.1-3.9 μm.

[0043] Preferably, the orientation forming in step (3) comprises pre-press forming under the condition of a magnetic field intensity >1.5 T to obtain a pre-press blank.

[0044] Further preferably, the orientation forming in step (3) comprises pre-press forming under the condition of a magnetic field intensity of 2-3 T at 30-40 Mpa for 1-60 s to obtain a pre-press blank.

[0045] Further preferably, the density of the pre-press blank is 3.7-4.9 g / cm 3 .

[0046] Preferably, the press forming in step (3) is isostatic pressing, which comprises isostatic pressing at 200-400 Mpa for 100-600 s to obtain a press blank.

[0047] Further preferably, the density of the press blank is 4.8-5.5 g / cm 3 .

[0048] Preferably, the sintering temperature of the sintering treatment in step (3) is 980-1200 °C, and the sintering time is 1-12 h.

[0049] Further preferably, the sintering temperature of the sintering treatment in step (3) is 1010-1070 °C, and the sintering time is 3-8 h.

[0050] As a preference, the sintering treatment in step (3) comprises one or more of vacuum sintering, pressure sintering, spark plasma sintering, microwave sintering.

[0051] It is further preferred that the vacuum sintering comprises one or more of vacuum pressureless sintering, staged vacuum sintering, vacuum hot-pressing sintering.

[0052] It is further preferred that the pressure sintering comprises one or more of hot-pressing sintering, vacuum hot-pressing sintering, atmosphere pressure sintering.

[0053] It is further preferred that the sintering treatment is vacuum pressureless sintering.

[0054] As a preference, the tempering temperature in step (3) is 200-1200℃, and the tempering time is 1-48h.

[0055] It is further preferred that the tempering temperature in step (3) is lower than the sintering temperature in step (3).

[0056] As a preference, the tempering treatment in step (3) is a multi-stage tempering treatment, and the tempering temperature of each stage decreases.

[0057] It is further preferred that the difference of the tempering temperature between two adjacent stages is >200℃.

[0058] It is further preferred that the difference of the tempering temperature between two adjacent stages is 300-500℃.

[0059] As a preference, the tempering treatment in step (3) is a multi-stage tempering treatment, and the tempering time of each stage increases.

[0060] It is further preferred that the difference of the tempering time between two adjacent stages is >1h.

[0061] It is further preferred that the difference of the tempering time between two adjacent stages is 2-5h.

[0062] As a preference, the tempering treatment in step (3) comprises a first stage tempering treatment and a second stage tempering treatment, the temperature of the first stage tempering treatment is 800-970℃, and the time is 1-6h, the temperature of the second stage tempering treatment is 400-700℃, and the time is 1-12h.

[0063] It is further preferred that the tempering treatment in step (3) comprises a first stage tempering treatment and a second stage tempering treatment, the temperature of the first stage tempering treatment is 840-950℃, and the time is 1-3h, the temperature of the second stage tempering treatment is 480-670℃, and the time is 3-5h.

[0064] As preferred, the preparation method of the neodymium-iron-boron magnet based on the matching of the powder particle size and the main phase grain size comprises the following steps:

[0065] (1) according to the component design of the target sintered neodymium-iron-boron magnet, the alloy liquid is obtained by heating and melting in a vacuum environment, and the temperature of the alloy liquid is 1430-1490℃; after the temperature of the alloy liquid is reduced to 1350-1400℃, the alloy liquid is guided to the surface of the copper roller for tape casting, wherein the rotating speed of the copper roller is 10-30r / min, the cooling rate is 9×10 4 ~ 6×10 5 ℃ / s, and the neodymium-iron-boron alloy rapid solidification sheet is obtained;

[0066] The chemical formula of the neodymium-iron-boron alloy rapid solidification sheet is RE a B b M c Fe 100-(a+b+c) , wherein RE is a rare earth element, including one or more of Pr, Nd, Dy, Tb, La, Ce, Y, Ho and Gd, M includes one or more of Cu, Al, Ga, Co, Zr and Ti, and 29≤a≤31, 0.91≤b<1.1, 0.5≤c≤4;

[0067] The neodymium-iron-boron alloy rapid solidification sheet comprises a main phase and a rare earth-rich phase distributed between the main phase; wherein the proportion of the main phase is 88-92%; the main phase is columnar crystal, the short axis size is 0.8-6.3μm, the average size of the short axis is 2.1-3.4μm, and the long axis size is 30-200μm;

[0068] (2) the neodymium-iron-boron alloy rapid solidification sheet is sequentially subjected to hydrogen crushing and air jet milling to obtain a neodymium-iron-boron powder, and the difference between the D50 particle size of the neodymium-iron-boron powder and the average size of the short axis of the main phase in step (1) is ≤1μm;

[0069] The ratio of the short diameter to the long diameter of the neodymium-iron-boron powder is (0.7-1):1, wherein the proportion of the neodymium-iron-boron powder satisfying the ratio of the short diameter to the long diameter of (0.8-1):1 is >60%;

[0070] (3) the neodymium-iron-boron powder is subjected to oriented forming, press forming, sintering treatment and tempering treatment to obtain a high-performance sintered neodymium-iron-boron magnet.

[0071] Further preferably, step (3) comprises: pre-pressing the Nd-Fe-B powder into a pre-pressing blank under a magnetic field strength > 1.5T; isostatic pressing the pre-pressing blank under 200-400Mpa for 100-600s to obtain a pressing blank; sintering the pressing blank, the sintering temperature being 980-1200℃, the sintering time being 1-12h; and tempering after cooling, the first-stage tempering temperature being 800-970℃, the first-stage tempering time being 1-6h, the second-stage tempering temperature being 400-700℃, the second-stage tempering time being 1-12h, and the natural cooling temperature being room temperature, to obtain the high-performance sintered Nd-Fe-B magnet.

[0072] The second object of the present application is achieved by the following technical solution:

[0073] A high-performance sintered Nd-Fe-B magnet prepared by the above method.

[0074] Preferably, the density of the high-performance sintered Nd-Fe-B magnet is 7.3-7.6g / cm 3 .

[0075] Preferably, the remanence Br of the high-performance sintered Nd-Fe-B magnet is > 14.5kGs.

[0076] Preferably, the intrinsic coercivity Hcj of the high-performance sintered Nd-Fe-B magnet is > 11kOe. Preferably, the saturation rotation degree of the high-performance sintered Nd-Fe-B magnet is > 97.5%.

[0077] Further preferably, the saturation rotation degree of the high-performance sintered Nd-Fe-B magnet is > 98%.

[0078] More preferably, the saturation rotation degree of the high-performance sintered Nd-Fe-B magnet is > 98.5%.

[0079] The third object of the present application is achieved by the following technical solution:

[0080] Use of the high-performance sintered Nd-Fe-B magnet as described above in the field of electric machines.

[0081] Compared with the prior art, the present application has the following beneficial effects:

[0082] 1. The present application precisely controls the rapid solidification and powder preparation process, so that the average size of the short axis of the main phase in the rapid solidification piece and the D50 particle size value of the Nd-Fe-B powder are effectively matched. This matching relationship can significantly reduce the probability of transgranular fracture of the main phase grains during the powder preparation process, especially during the jet mill stage, reduce the excessive exposure of the main phase section, and at the same time inhibit the stripping or dispersion of the rare earth-rich phase, thereby ensuring the formation of a complete and uniform rare earth-rich phase coating on the surface of the main phase grains, and optimizing the microstructure from the source.

[0083] 2、The complete rare earth-rich phase coating formed based on size matching can play multiple positive roles in the sintering process: on the one hand, as a non-magnetic phase, the rare earth-rich phase can effectively isolate adjacent main phase grains, weaken the magnetic coupling between them, reduce the tendency of magnetic moment reversal, significantly improve the coercivity (Hcj) of the magnet, and enhance its demagnetization resistance in high-temperature and strong magnetic field environments; on the other hand, the complete main phase structure helps to avoid the generation of magnetic flux leakage paths, thereby ensuring that the remanence (Br) does not decrease due to structural defects. The synergistic improvement of coercivity and remanence further pushes the magnetic energy product ((BH)max) to break through the limitations of traditional processes, making the magnet fully meet the strict requirements of high-performance applications for magnetic properties, and making up for the shortcomings of traditional methods in preparing high-performance magnets.

[0084] 3、The present application innovatively establishes the correlation mechanism between the main phase size of the rapidly solidified sheet and the powder particle size, and builds a synergistic regulation system from rapid solidification to powder making: by adjusting the rapid solidification process parameters, the average size of the main phase short axis is accurately controlled; and then the powder making parameters are optimized to effectively match the powder D50 particle size with the main phase size. This regulation strategy overcomes the limitations of traditional processes that focus too much on particle size and ignore structural integrity, realizes dual precise control of powder particle size and microstructure, ensures the consistency of powder microstructure quality between batches, and solves the problem of large performance fluctuations of powder in traditional processes.

[0085] 4、The powder prepared by the present application has a complete rare earth-rich phase coating, which can avoid problems such as abnormal growth of main phase grains and uneven distribution of grain boundary phases caused by incomplete coating, thereby effectively suppressing the performance fluctuations of the magnet and improving the yield. The coating plays multiple positive roles in the sintering process: first, as a liquid phase sintering medium, the rare earth-rich phase can uniformly fill the gaps between main phase grains, inhibit the excessive growth of grains, and promote the homogenization of the sintered body structure; second, the complete coating can block the direct contact between main phase grains, reducing the loss of magnetic properties; third, the uniformly distributed grain boundary phase helps to relieve internal stress and reduce the tendency of magnet cracking and deformation.

[0086] 5、The method described in the present application shows good applicability to neodymium-iron-boron magnets with different element ratios; whether it is a high-temperature-resistant magnet with high dysprosium (Dy) and terbium (Tb) content, or a low-cost magnet with low heavy rare earth and high neodymium (Nd) iron (Fe) ratio, the present application can realize precise matching of the main phase size and the powder particle size, ensure the formation of a complete rare earth-rich phase coating, and avoid the problem of process inadaptability caused by composition differences.

[0087] 6、The process parameter regulation logic provided by the application is clear, and the operation is simple, which provides a low-cost and easy-to-implement solution for the industrial upgrading of high-performance neodymium-iron-boron magnets, and effectively promotes the transformation of the sintered neodymium-iron-boron industry to high performance and low energy consumption. BRIEF DESCRIPTION OF DRAWINGS

[0088] Figure 1 The microstructure (a) and data distribution graph of thickness (b) of the neodymium-iron-boron alloy rapid solidification sheet in the embodiment 1 of the application.

[0089] Figure 2 The microstructure (a) and data distribution graph of powder particle size (b) of the neodymium-iron-boron powder in the embodiment 1 of the application.

[0090] Figure 3 The microstructure (a) and data distribution graph of grain size (b) of the high-performance sintered neodymium-iron-boron magnet in the embodiment 1 of the application.

[0091] Figure 4 The microstructure (a) and data distribution graph of powder particle size (b) of the neodymium-iron-boron powder in the embodiment 2 of the application.

[0092] Figure 5 The microstructure (a) and data distribution graph of grain size (b) of the high-performance sintered neodymium-iron-boron magnet in the embodiment 2 of the application.

[0093] Figure 6 The magnetic performance test graph of the high-performance sintered neodymium-iron-boron magnet in the embodiment 1 of the application and the high-performance sintered neodymium-iron-boron magnet in the embodiment 2 of the application. DETAILED DESCRIPTION

[0094] The technical solutions of the application will be further described and illustrated by specific embodiments. It should be understood that the specific embodiments described herein are only used to help understand the application, and are not used to limit the application.

[0095] If not specifically stated, the raw materials used in the embodiments of the application are all commonly used raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0096] In this paper, the high-performance sintered neodymium-iron-boron magnet obtained in step (3) of the neodymium-iron-boron magnet preparation method based on matching the powder particle size and the main phase grain size can also be further improved in magnetic performance by processes such as grain boundary diffusion by coating a diffusion source.

[0097] In this paper, the neodymium-iron-boron alloy raw material is free of oxide scale.

[0098] In the present application, the neodymium-iron-boron alloy rapidly solidified flake includes a main phase and a rare earth-rich phase distributed between the main phase; the proportion of the main phase in the neodymium-iron-boron alloy rapidly solidified flake is 88-92%. If the proportion of the main phase is too high, the proportion of the corresponding rare earth-rich phase (such as Nd-rich phase) will decrease, which leads to the decrease of the rare earth-rich phase wrapping degree of the crystal grains, and is not conducive to the coercivity.

[0099] In the present application, by matching the powder particle size with the short axis size of the rapidly solidified flake, the roundness of the particles can be increased, the orientation degree is improved, the surface of the particles is kept intact and covered by the rare earth-rich phase, the rare earth-rich phase is prevented from being stripped due to crushing, direct contact between the crystal grains is effectively avoided, and the remanence and coercivity are simultaneously improved.

[0100] In the present application, the microstructure of the cross section of the rapidly solidified flake is characterized by the interlaced distribution of the columnar crystals and the rare earth-rich phase. The average size of the short axis of the columnar crystals is adjusted to 2.1-3.4 μm. If the size of the short axis is less than 2.1 μm, on the one hand, stress is easily generated between the columnar crystals and the rare earth-rich phase under temperature change or external force, which leads to microcracks or the stripping of the rare earth-rich phase, resulting in the discontinuity of the grain boundary phase. On the other hand, during subsequent sintering or long-term service, atoms are prone to diffuse along the grain boundary, leading to grain coarsening and a sharp decrease in coercivity. If the size of the short axis is greater than 3.4 μm, part of the crystal grains are in a multi-domain state, which reduces the magnetic anisotropy and leads to a decrease in coercivity.

[0101] In the present application, the hydrogen crushing time and the jet mill time are the same in each example and comparative example unless otherwise specified.

[0102] In the present application, the characterization includes testing / calculating the size of the columnar crystals and the size of the neodymium-iron-boron powder by a scanning electron microscope.

[0103] In the present application, the performance test includes:

[0104] The high-performance sintered neodymium-iron-boron magnet is processed into a standard sample column with a diameter of 10 mm and a height of 10 mm. The performance of the magnet is tested by a BH instrument, including the remanence Br, the intrinsic coercivity Hcj, the maximum magnetic energy product (BH)max, the saturation magnetization Js, and the saturation rotation degree.

[0105] The saturation rotation degree is used to represent the orientation degree of the main phase crystal grains of the magnet. The closer the value is to 1, the higher the proportion of the c-axis of the main phase crystal grains arranged along the orientation direction. In the present application, the saturation rotation degree is obtained by using the ratio of the residual magnetic polarization strength Jr to the saturation magnetization strength Js in the hysteresis loop.

[0106] Example 1

[0107] In the present application, the neodymium-iron-boron magnet preparation method based on the matching of the powder particle size and the main phase grain size includes:

[0108] (1) According to the composition design of the target sintered neodymium-iron-boron magnet, the chemical formula of Nd 30.5 B 0.93 Co 0.5 Cu 0.1 Ga 0.05 Zr 0.05 Fe 67.87 The neodymium-iron-boron alloy raw material is prepared, the neodymium-iron-boron alloy raw material is placed in a vacuum induction melting furnace under vacuum environment and heated to complete melting, obtaining an alloy liquid with a temperature of 1470℃, and after the temperature of the alloy liquid is reduced to 1380℃, the alloy liquid is guided to the surface of a copper roller for tape casting, wherein the rotation speed of the copper roller is 28r / min, the cooling rate is 3×10 5 ℃ / s, and a neodymium-iron-boron alloy rapid solidification sheet is obtained.

[0109] The microstructure of the neodymium-iron-boron alloy rapid solidification sheet and the data distribution statistics of the thickness thereof in the embodiment are shown in Figure 1 .

[0110] The average thickness of the neodymium-iron-boron alloy rapid solidification sheet is 0.24mm, and the proportion of the thickness in the range of 0.20-0.28mm is up to 90%. The proportion of the main phase of the neodymium-iron-boron alloy rapid solidification sheet is 90%, and the Nd-rich phase is distributed between the main phase grains; the main phase is columnar crystal, the average size of the short axis is 2.70μm, and the average size of the long axis is 160μm.

[0111] (2) The neodymium-iron-boron alloy rapid solidification sheet is placed in a hydrogen crusher, and the hydrogen content is controlled to be lower than 800ppm, obtaining a neodymium-iron-boron coarse powder with a D50 of 53μm; the neodymium-iron-boron coarse powder is placed in an air flow mill, the oxygen content is controlled to be lower than 40ppm, and the grading wheel rotation speed is 3200rpm, obtaining a neodymium-iron-boron powder.

[0112] The microstructure of the neodymium-iron-boron powder and the data distribution statistics of the powder particle size in the embodiment are shown in Figure 2 .

[0113] The D50 of the neodymium-iron-boron powder is 2.70μm, the D10 is 1.06μm, and the D90 is 3.53μm; the neodymium-iron-boron powder particle morphology is round, and the proportion of the ratio of the short diameter to the long diameter of the neodymium-iron-boron powder satisfying (0.8-1):1 is 73%.

[0114] (3) The neodymium-iron-boron powder is filled into an orientation forming mold cavity, and is pressed and formed under an orientation magnetic field of 2.3T, obtaining a density of 4.1g / cm 3The pre-compacted embryo is isostatically pressed at 350 MPa for 300 s to obtain a pressed embryo; the pressed embryo is placed in a vacuum sintering furnace for sintering treatment, and sintered at a sintering temperature of 1040 ℃ for 5 h; after cooling, tempering treatment is performed, the temperature is raised to a first-stage tempering treatment temperature of 900 ℃ for tempering for 2 h, and then the temperature is lowered to a second-stage tempering treatment temperature of 515 ℃ for tempering for 4.5 h, and then naturally cooled to room temperature, to obtain a high-performance sintered neodymium-iron-boron magnet.

[0115] The micro-morphology and data distribution statistics of the grain size of the high-performance sintered neodymium-iron-boron magnet in this embodiment are shown in Figure 3 It can be seen that the average size of the grains is 4.28 μm.

[0116] The magnetic properties of the high-performance sintered neodymium-iron-boron magnet in this embodiment are shown in Table 1.

[0117] Example 2

[0118] The preparation method of the neodymium-iron-boron magnet based on matching of the powder particle size and the main phase grain size in this embodiment comprises:

[0119] (1) The neodymium-iron-boron alloy rapid solidification sheet obtained in step (1) of Example 1 is used.

[0120] (2) The neodymium-iron-boron alloy rapid solidification sheet is placed in a hydrogen crushing furnace, and the hydrogen content is controlled to be less than 800 ppm, to obtain a neodymium-iron-boron coarse powder; the neodymium-iron-boron coarse powder is placed in an air flow mill, and the oxygen content is controlled to be less than 40 ppm, and the classification wheel rotation speed is 2780 rpm, to obtain a neodymium-iron-boron powder.

[0121] The micro-morphology and data distribution statistics of the powder particle size of the neodymium-iron-boron powder in this embodiment are shown in Figure 4 .

[0122] The D50 of the neodymium-iron-boron powder is 3.20 μm, the D10 is 1.75 μm, and the D90 is 4.15 μm, and the particle morphology of the neodymium-iron-boron powder is relatively sharp, and the ratio of the short diameter to the long diameter is (0.8-1):1, and the proportion of the neodymium-iron-boron powder is 53%.

[0123] (3) The same as step (3) of Example 1.

[0124] The micro-morphology and data distribution statistics of the grain size of the high-performance sintered neodymium-iron-boron magnet in this embodiment are shown in Figure 5 , and the average size of the grains is 5.63 μm.

[0125] The magnetic properties of the high-performance sintered neodymium-iron-boron magnet in this embodiment are shown in Table 1.

[0126] Example 3

[0127] The preparation method of the neodymium-iron-boron magnet based on matching of the powder particle size and the main phase grain size in this embodiment comprises:

[0128] (1) The neodymium-iron-boron alloy rapidly solidified flake obtained in step (1) of Example 1 was used.

[0129] (2) The neodymium-iron-boron alloy rapidly solidified flake was placed in a hydrogen decrepitation furnace, and the hydrogen content was controlled to be less than 800 ppm to obtain a neodymium-iron-boron coarse powder; the neodymium-iron-boron coarse powder was placed in an air flow mill, and the oxygen content was controlled to be less than 40 ppm, and the grading wheel rotation speed was 3070 rpm to obtain a neodymium-iron-boron powder; the neodymium-iron-boron powder had a D50 of 2.92 μm, a D10 of 1.43 μm, and a D90 of 3.82 μm, and the ratio of the short diameter to the long diameter was (0.8-1):1, and the proportion of the neodymium-iron-boron powder was 63%.

[0130] (3) The same as step (3) of Example 1.

[0131] The magnetic properties of the high-performance sintered neodymium-iron-boron magnet in this example are shown in Table 1.

[0132] Example 4

[0133] The neodymium-iron-boron magnet preparation method based on matching of the powder particle size and the main phase grain size in this example comprises:

[0134] (1) The neodymium-iron-boron alloy rapidly solidified flake obtained in step (1) of Example 1 was used.

[0135] (2) The neodymium-iron-boron alloy rapidly solidified flake was placed in a hydrogen decrepitation furnace, and the hydrogen content was controlled to be less than 800 ppm to obtain a neodymium-iron-boron coarse powder; the neodymium-iron-boron coarse powder was placed in an air flow mill, and the oxygen content was controlled to be less than 40 ppm, and the grading wheel rotation speed was 3560 rpm to obtain a neodymium-iron-boron powder; the neodymium-iron-boron powder had a D50 of 2.52 μm, a D10 of 0.76 μm, and a D90 of 3.23 μm, and the ratio of the short diameter to the long diameter was (0.8-1):1, and the proportion of the neodymium-iron-boron powder was 60%.

[0136] (3) The same as step (3) of Example 1.

[0137] The magnetic properties of the high-performance sintered neodymium-iron-boron magnet in this example are shown in Table 1.

[0138] Example 5

[0139] The neodymium-iron-boron magnet preparation method based on matching of the powder particle size and the main phase grain size in this example comprises:

[0140] (1) The neodymium-iron-boron alloy rapidly solidified flake obtained in step (1) of Example 1 was used.

[0141] (2) Put the neodymium iron boron alloy rapid solidification piece into a hydrogen crusher, control the hydrogen content to be lower than 800 ppm, and obtain a neodymium iron boron coarse powder; put the neodymium iron boron coarse powder into an air flow mill, control the oxygen content to be lower than 40 ppm, and obtain a neodymium iron boron powder with a classification wheel rotating speed of 3870 rpm; the neodymium iron boron powder has a D50 of 2.33 μm, a D10 of 0.53 μm, and a D90 of 2.96 μm, and the ratio of the short diameter to the long diameter of the neodymium iron boron powder is (0.8-1):1, and the proportion of the neodymium iron boron powder is 58%.

[0142] (3) The same as step (3) of Example 1.

[0143] The magnetic properties of the high-performance sintered neodymium iron boron magnet in this example are shown in Table 1.

[0144] Example 6

[0145] The neodymium iron boron magnet preparation method based on the matching of the powder particle size and the main phase grain size in this example comprises:

[0146] (1) According to the composition design of the target sintered neodymium iron boron magnet, the chemical formula Nd 30.5 B 0.93 Co 0.5 Cu 0.1 Ga 0.05 Zr 0.05 Fe 67.87 The neodymium iron boron alloy raw material is prepared, the neodymium iron boron alloy raw material is placed in a vacuum induction melting furnace under vacuum environment and heated to complete melting, and an alloy liquid with a temperature of 1470℃ is obtained. After the temperature of the alloy liquid is reduced to 1380℃, the alloy liquid is guided to the surface of a copper roller for tape casting, wherein the rotating speed of the copper roller is 32 r / min, the cooling rate is 4.5×10 5 ℃ / s, and a neodymium iron boron alloy rapid solidification piece is obtained.

[0147] The average thickness of the neodymium iron boron alloy rapid solidification piece is 0.21 mm, and the proportion of the thickness in the range of 0.20-0.28 mm is 87%. The proportion of the main phase of the neodymium iron boron alloy rapid solidification piece is 88%, and the Nd-rich phase is distributed between the main phase grains; the main phase is columnar crystal, the average size of the short axis is 2.42 μm, and the average size of the long axis is 153 μm.

[0148] (2) Put the neodymium iron boron alloy rapid solidification piece into a hydrogen crusher, control the hydrogen content to be lower than 800 ppm, and obtain a neodymium iron boron coarse powder with a D50 of 46 μm; put the neodymium iron boron coarse powder into an air flow mill, control the oxygen content to be lower than 40 ppm, and control the rotational speed of the grading wheel to be 3610 rpm, to obtain a neodymium iron boron powder; the D50 of the neodymium iron boron powder is 2.16 μm, the D10 is 1.05 μm, and the D90 is 3.16 μm, and the ratio of the short diameter to the long diameter of the neodymium iron boron powder is (0.8-1):1, and the proportion of the neodymium iron boron powder is 74%.

[0149] (3) The same as step (3) of Example 1.

[0150] The magnetic properties of the high-performance sintered neodymium iron boron magnet in this example are shown in Table 1.

[0151] Example 7

[0152] The neodymium iron boron magnet preparation method based on the matching of the powder particle size and the main phase grain size in this example comprises:

[0153] (1) According to the composition design of the target sintered neodymium iron boron magnet, the chemical formula Nd 30.5 B 0.93 Co 0.5 Cu 0.1 Ga 0.05 Zr 0.05 Fe 67.87 The neodymium iron boron alloy raw material is prepared, the neodymium iron boron alloy raw material is placed in a vacuum induction melting furnace under vacuum environment and heated to complete melting, to obtain an alloy liquid with a temperature of 1470℃, the temperature of the alloy liquid is reduced to 1380℃, and then the alloy liquid is guided to the surface of a copper roller for tape casting, wherein the rotational speed of the copper roller is 33 r / min, the cooling rate is 4.6×10 5 ℃ / min, and the neodymium iron boron alloy rapid solidification piece is obtained.

[0154] The average thickness of the neodymium iron boron alloy rapid solidification piece is 0.21 mm, and the proportion of the thickness in the range of 0.20-0.28 mm is 88%. The proportion of the main phase of the neodymium iron boron alloy rapid solidification piece is 85%, and the Nd-rich phase is distributed between the main phase grains; the main phase is columnar crystal, the average size of the short axis is 2.35 μm, and the average size of the long axis is 150 μm.

[0155] (2) Put the Nd-Fe-B alloy rapidly solidified flake into a hydrogen decrepitation furnace, control the hydrogen content to be lower than 800 ppm, to obtain Nd-Fe-B coarse powder with D50 of 46 μm; put the Nd-Fe-B coarse powder into an air jet mill, control the oxygen content to be lower than 40 ppm, and the grading wheel rotating speed to be 3590 rpm, to obtain Nd-Fe-B powder; the Nd-Fe-B powder has D50 of 2.22 μm, D10 of 0.86 μm, and D90 of 3.05 μm, and the ratio of the short diameter to the long diameter of (0.8-1):1 meets the requirements of 79%.

[0156] (3) The same as step (3) of Example 1.

[0157] The magnetic properties of the high-performance sintered Nd-Fe-B magnet in this example are shown in Table 1.

[0158] Example 8

[0159] The Nd-Fe-B magnet preparation method based on matching of the powder particle size and the main phase grain size in this example comprises:

[0160] (1) The Nd-Fe-B alloy rapidly solidified flake in step (1) of Example 6 has an average size of the short axis of 2.42 μm;

[0161] (2) Put the Nd-Fe-B alloy rapidly solidified flake into a hydrogen decrepitation furnace, control the hydrogen content to be lower than 800 ppm, to obtain Nd-Fe-B coarse powder; put the Nd-Fe-B coarse powder into an air jet mill, control the oxygen content to be lower than 40 ppm, and the grading wheel rotating speed to be 2520 rpm, to obtain Nd-Fe-B powder; the Nd-Fe-B powder has D50 of 3.34 μm, D10 of 1.91 μm, and D90 of 4.47 μm, and the ratio of the short diameter to the long diameter of (0.8-1):1 meets the requirements of 46%.

[0162] (3) The same as step (3) of Example 1.

[0163] The magnetic properties of the high-performance sintered Nd-Fe-B magnet in this example are shown in Table 1.

[0164] Example 9

[0165] The Nd-Fe-B magnet preparation method based on matching of the powder particle size and the main phase grain size in this example comprises:

[0166] (1) According to the component design of the target sintered Nd-Fe-B magnet, the chemical formula Nd 30.5 B 0.93 Co 0.5 Cu 0.1 Ga 0.05 Zr 0.05 Fe 67.87The neodymium-iron-boron alloy raw materials are prepared, the neodymium-iron-boron alloy raw materials are heated to complete melting in a vacuum induction melting furnace under a vacuum environment, an alloy liquid with a temperature of 1470℃ is obtained, the temperature of the alloy liquid is reduced to 1400℃, and then the alloy liquid is guided to the surface of a copper roller for tape casting, wherein the rotating speed of the copper roller is 30r / min, the cooling rate is 3.8×10 5 ℃ / s, and a neodymium-iron-boron alloy rapid solidification piece is obtained.

[0167] The average thickness of the neodymium-iron-boron alloy rapid solidification piece is 0.25mm, and the proportion of the thickness in the range of 0.20-0.28mm is 90%. The proportion of the main phase of the neodymium-iron-boron alloy rapid solidification piece is 85%, and the Nd-rich phase is distributed between the main phase grains; the main phase is columnar crystal, the average size of the short axis is 2.53μm, and the average size of the long axis is 142μm.

[0168] (2) The neodymium-iron-boron alloy rapid solidification piece is placed in a hydrogen decrepitation furnace, the hydrogen content is controlled to be lower than 800ppm, a neodymium-iron-boron coarse powder with a D50 of 47μm is obtained, the neodymium-iron-boron coarse powder is placed in an airflow mill, the oxygen content is controlled to be lower than 40ppm, the rotating speed of the grading wheel is 3580rpm, and a neodymium-iron-boron powder is obtained; the D50 of the neodymium-iron-boron powder is 2.53μm, the D10 is 0.83μm, and the D90 is 3.16μm, and the proportion of the neodymium-iron-boron powder satisfying the ratio of the short diameter to the long diameter of (0.8-1):1 is 70%.

[0169] (3) The same as step (3) of Example 1.

[0170] The magnetic properties of the high-performance sintered neodymium-iron-boron magnet in this example are shown in Table 1.

[0171] Example 10

[0172] The neodymium-iron-boron magnet preparation method based on the matching of the powder particle size and the main phase grain size in this example comprises:

[0173] (1) According to the composition design of the target sintered neodymium-iron-boron magnet, the chemical formula Nd 30.5 B 0.93 Co 0.5 Cu 0.1 Ga 0.05 Zr 0.05 Fe 67.87 The neodymium-iron-boron alloy raw materials are prepared, the neodymium-iron-boron alloy raw materials are heated to complete melting in a vacuum induction melting furnace under a vacuum environment, an alloy liquid with a temperature of 1470℃ is obtained, the temperature of the alloy liquid is reduced to 1400℃, and then the alloy liquid is guided to the surface of a copper roller for tape casting, wherein the rotating speed of the copper roller is 30r / min, the cooling rate is 3.8×10 5 ℃ / s, and a neodymium-iron-boron alloy rapid solidification piece is obtained.

[0174] The average thickness of the neodymium-iron-boron alloy rapid solidification sheet is 0.27 mm, and the proportion of the thickness in the range of 0.20-0.28 mm is 70%. The proportion of the main phase of the neodymium-iron-boron alloy rapid solidification sheet is 92%, and the Nd-rich phase is distributed between the main phase grains; the main phase is columnar crystal, the average size of the short axis is 2.93 μm, and the average size of the long axis is 155 μm.

[0175] (2) The neodymium-iron-boron alloy rapid solidification sheet is placed in a hydrogen decrepitation furnace, the hydrogen content is controlled to be less than 800 ppm, and a neodymium-iron-boron coarse powder with a D50 of 62 μm is obtained; the neodymium-iron-boron coarse powder is placed in an air flow mill, the oxygen content is controlled to be less than 40 ppm, and the grading wheel rotating speed is 3050 rpm, and a neodymium-iron-boron powder is obtained; the D50 of the neodymium-iron-boron powder is 2.94 μm, the D10 is 1.63 μm, and the D90 is 4.15 μm, and the proportion of the neodymium-iron-boron powder satisfying the ratio of the short diameter to the long diameter of (0.8-1):1 is 63%.

[0176] (3) The same as step (3) of Example 1.

[0177] The magnetic properties of the high-performance sintered neodymium-iron-boron magnet in this example are shown in Table 1.

[0178] Example 11

[0179] The neodymium-iron-boron magnet preparation method based on the matching of the powder particle size and the main phase grain size in this example comprises:

[0180] (1) According to the composition design of the target sintered neodymium-iron-boron magnet, the chemical formula Nd 30.5 B 0.93 Co 0.5 Cu 0.1 Ga 0.05 Zr 0.05 Fe 67.87 The neodymium-iron-boron alloy raw material is prepared, the neodymium-iron-boron alloy raw material is placed in a vacuum induction melting furnace under vacuum environment and heated to complete melting, an alloy liquid with a temperature of 1470 ℃ is obtained, the alloy liquid is directly guided to the surface of a copper roller for tape casting, the rotating speed of the copper roller is 28 r / min, the cooling rate is 3×10 5 ℃ / s, and a neodymium-iron-boron alloy rapid solidification sheet is obtained.

[0181] The average thickness of the neodymium-iron-boron alloy rapid solidification sheet is 0.29 mm, and the proportion of the thickness in the range of 0.20-0.28 mm is 45%. The proportion of the main phase of the neodymium-iron-boron alloy rapid solidification sheet is 80%, and the Nd-rich phase is distributed between the main phase grains; the main phase is columnar crystal, the average size of the short axis is 3.20 μm, and the average size of the long axis is 133 μm.

[0182] (2) Put the neodymium iron boron alloy rapid solidification piece into a hydrogen crusher, control the hydrogen content to be lower than 800 ppm, and obtain a neodymium iron boron coarse powder with a D50 of 71 μm; put the neodymium iron boron coarse powder into an air flow mill, control the oxygen content to be lower than 40 ppm, and control the rotational speed of the grading wheel to be 2930 rpm, to obtain a neodymium iron boron powder; the D50 of the neodymium iron boron powder is 3.21 μm, the D10 is 2.16 μm, and the D90 is 4.59 μm, and the ratio of the short diameter to the long diameter of the neodymium iron boron powder is (0.8-1):1, and the proportion of the neodymium iron boron powder is 65%.

[0183] (3) The same as step (3) of Example 1.

[0184] The magnetic properties of the high-performance sintered neodymium iron boron magnet in this example are shown in Table 1.

[0185] Example 12

[0186] The neodymium iron boron magnet preparation method based on the matching of the powder particle size and the main phase grain size in this example comprises:

[0187] (1) According to the composition design of the target sintered neodymium iron boron magnet, the chemical formula Nd 30.5 B 0.93 Co 0.5 Cu 0.1 Ga 0.05 Zr 0.05 Fe 67.87 The neodymium iron boron alloy raw material is prepared, the neodymium iron boron alloy raw material is placed in a vacuum induction melting furnace under vacuum environment and heated to complete melting, and an alloy liquid with a temperature of 1470℃ is obtained. After the temperature of the alloy liquid is reduced to 1300℃, the alloy liquid is guided to the surface of a copper roller for tape casting, wherein the rotational speed of the copper roller is 28 r / min, the cooling rate is 3×10 5 ℃ / s, and a neodymium iron boron alloy rapid solidification piece is obtained.

[0188] The average thickness of the neodymium iron boron alloy rapid solidification piece is 0.19 mm, and the proportion of the thickness in the range of 0.20-0.28 mm is 45%. The proportion of the main phase of the neodymium iron boron alloy rapid solidification piece is 73%, and the Nd-rich phase is distributed between the main phase grains; the main phase is columnar crystal, the average size of the short axis is 2.07 μm, and the average size of the long axis is 152 μm.

[0189] (2) Put the neodymium iron boron alloy rapid solidification piece into a hydrogen crusher, control the hydrogen content to be lower than 800 ppm, and obtain a neodymium iron boron coarse powder with a D50 of 43 μm; put the neodymium iron boron coarse powder into an air flow mill, control the oxygen content to be lower than 40 ppm, and control the rotational speed of the grading wheel to be 3762 rpm, to obtain a neodymium iron boron powder; the D50 of the neodymium iron boron powder is 2.05 μm, the D10 is 0.73 μm, and the D90 is 2.81 μm, and the ratio of the short diameter to the long diameter of the neodymium iron boron powder is (0.8-1):1, and the proportion of the neodymium iron boron powder is 63%.

[0190] (3) The same as step (3) of Example 1.

[0191] The magnetic properties of the high-performance sintered neodymium iron boron magnet in this example are shown in Table 1.

[0192] Example 13

[0193] The neodymium iron boron magnet preparation method based on the matching of the powder particle size and the main phase grain size in this example comprises:

[0194] (1) According to the composition design of the target sintered neodymium iron boron magnet, the chemical formula Nd 30.5 B 0.93 Co 0.5 Cu 0.1 Ga 0.05 Zr 0.05 Fe 67.87 The neodymium iron boron alloy raw material is prepared, the neodymium iron boron alloy raw material is placed in a vacuum induction melting furnace under vacuum environment and heated to complete melting, to obtain an alloy liquid with a temperature of 1470℃, the temperature of the alloy liquid is reduced to 1380℃, and then the alloy liquid is guided to the surface of a copper roller for tape casting, wherein the rotational speed of the copper roller is 28 r / min, the cooling rate is 3×10 5 ℃ / min, and the neodymium iron boron alloy rapid solidification piece is obtained.

[0195] The average thickness of the neodymium iron boron alloy rapid solidification piece is 0.24 mm, and the proportion of the thickness in the range of 0.20-0.28 mm is 90%. The proportion of the main phase of the neodymium iron boron alloy rapid solidification piece is 90%, and the Nd-rich phase is distributed between the main phase grains; the main phase is columnar crystal, the average size of the short axis is 2.71 μm, and the average size of the long axis is 161 μm.

[0196] (2) Put the neodymium iron boron alloy rapid solidification piece into a hydrogen crusher, control the hydrogen content to be lower than 800 ppm, and obtain a neodymium iron boron coarse powder with a D50 of 53 μm; put the neodymium iron boron coarse powder into an air flow mill, control the oxygen content to be lower than 40 ppm, and control the rotational speed of the grading wheel to be 3200 rpm, to obtain a neodymium iron boron powder; the D50 of the neodymium iron boron powder is 2.72 μm, the D10 is 1.09 μm, and the D90 is 3.56 μm, and the ratio of the short diameter to the long diameter of the neodymium iron boron powder is (0.8-1):1, and the proportion of the neodymium iron boron powder is 74%.

[0197] (3) The same as step (3) of Example 1.

[0198] The magnetic properties of the high-performance sintered neodymium iron boron magnet in this example are shown in Table 1.

[0199] Example 14

[0200] The neodymium iron boron magnet preparation method based on the matching of the powder particle size and the main phase grain size in this example comprises:

[0201] (1) According to the composition design of the target sintered neodymium iron boron magnet, the chemical formula Nd 30.5 B 0.93 Co 0.5 Cu 0.1 Ga 0.05 Zr 0.05 Fe 67.87 The neodymium iron boron alloy raw material is prepared, the neodymium iron boron alloy raw material is placed in a vacuum induction melting furnace under vacuum environment and heated to complete melting, to obtain an alloy liquid with a temperature of 1470℃, the temperature of the alloy liquid is reduced to 1380℃, and then the alloy liquid is guided to the surface of a copper roller for tape casting, wherein the rotational speed of the copper roller is 31 r / min, the cooling rate is 4×10 5 ℃ / s, and the neodymium iron boron alloy rapid solidification piece is obtained.

[0202] The average thickness of the neodymium iron boron alloy rapid solidification piece is 0.22 mm, and the proportion of the thickness in the range of 0.20-0.28 mm is 87%. The proportion of the main phase of the neodymium iron boron alloy rapid solidification piece is 88%, and the Nd-rich phase is distributed between the main phase grains; the main phase is columnar crystal, the average size of the short axis is 2.49 μm, and the average size of the long axis is 156 μm.

[0203] (2) Put the neodymium iron boron alloy rapid solidification piece into a hydrogen crusher, control the hydrogen content to be lower than 800 ppm, and obtain a neodymium iron boron coarse powder with a D50 of 49 μm; put the neodymium iron boron coarse powder into an air flow mill, control the oxygen content to be lower than 40 ppm, and control the rotational speed of the grading wheel to be 3550 rpm, to obtain a neodymium iron boron powder; the D50 of the neodymium iron boron powder is 2.48 μm, the D10 is 0.74 μm, and the D90 is 3.15 μm, and the ratio of the short diameter to the long diameter of the neodymium iron boron powder is (0.8-1):1, and the proportion of the neodymium iron boron powder is 69%.

[0204] (3) The same as step (3) of Example 1.

[0205] The magnetic properties of the high-performance sintered neodymium iron boron magnet in this example are shown in Table 1.

[0206] Example 15

[0207] The neodymium iron boron magnet preparation method based on the matching of the powder particle size and the main phase grain size in this example comprises:

[0208] (1) According to the composition design of the target sintered neodymium iron boron magnet, the chemical formula Nd 30.5 B 0.93 Co 0.5 Cu 0.1 Ga 0.05 Zr 0.05 Fe 67.87 The neodymium iron boron alloy raw material is prepared, the neodymium iron boron alloy raw material is placed in a vacuum induction melting furnace under vacuum environment and heated to complete melting, and an alloy liquid with a temperature of 1470℃ is obtained. After the temperature of the alloy liquid is reduced to 1380℃, the alloy liquid is guided to the surface of a copper roller for tape casting, wherein the rotational speed of the copper roller is 32 r / min, the cooling rate is 4.5×10 5 ℃ / s, and a neodymium iron boron alloy rapid solidification piece is obtained.

[0209] The average thickness of the neodymium iron boron alloy rapid solidification piece is 0.15 mm, and the proportion of the thickness in the range of 0.20-0.28 mm is 22%. The proportion of the main phase of the neodymium iron boron alloy rapid solidification piece is 62%, and the Nd-rich phase is distributed between the main phase grains; the main phase is columnar crystal, the average size of the short axis is 1.54 μm, and the average size of the long axis is 130 μm.

[0210] (2) The neodymium iron boron alloy rapid solidification piece is placed in a hydrogen crusher, and the hydrogen content is controlled to be less than 800 ppm, to obtain neodymium iron boron coarse powder with D50 of 40 μm; the neodymium iron boron coarse powder is placed in an air flow mill, and the oxygen content is controlled to be less than 40 ppm, and the grading wheel rotating speed is 4130 rpm, to obtain neodymium iron boron powder; the neodymium iron boron powder has D50 = 1.59 μm, D10 = 0.32 μm, and D90 = 2.11 μm, and the proportion of the neodymium iron boron powder satisfying the ratio of the short diameter to the long diameter of (0.8-1):1 is 65%.

[0211] (3) The same as step (3) of Example 1.

[0212] The magnetic properties of the high-performance sintered neodymium iron boron magnet in this example are shown in Table 1.

[0213] Comparative Example 1

[0214] The preparation method of the neodymium iron boron magnet based on matching of the powder particle size and the main phase grain size in this comparative example comprises:

[0215] (1) The neodymium iron boron alloy rapid solidification piece obtained in step (1) of Example 1 is used.

[0216] (2) The neodymium iron boron alloy rapid solidification piece is placed in a hydrogen crusher, and the hydrogen content is controlled to be less than 800 ppm, to obtain neodymium iron boron coarse powder; the neodymium iron boron coarse powder is placed in an air flow mill, and the oxygen content is controlled to be less than 40 ppm, and the grading wheel rotating speed is 2260 rpm, to obtain neodymium iron boron powder; the neodymium iron boron powder has D50 = 3.96 μm, D10 = 2.32 μm, and D90 = 4.75 μm, and the proportion of the neodymium iron boron powder satisfying the ratio of the short diameter to the long diameter of (0.8-1):1 is 43%.

[0217] (3) The same as step (3) of Example 1.

[0218] The magnetic properties of the high-performance sintered neodymium iron boron magnet in this comparative example are shown in Table 1.

[0219] Comparative Example 2

[0220] The preparation method of the neodymium iron boron magnet based on matching of the powder particle size and the main phase grain size in this comparative example comprises:

[0221] (1) According to the composition design of the target sintered neodymium iron boron magnet, the chemical formula Nd 30.5 B 0.93 Co 0.5 Cu 0.1 Ga 0.05 Zr 0.05 Fe 67.87The neodymium-iron-boron alloy raw material is prepared, the neodymium-iron-boron alloy raw material is placed in a vacuum induction melting furnace and heated to complete melting under vacuum, an alloy liquid with a temperature of 1470°C is obtained, the alloy liquid is guided to the surface of a copper roller for tape casting, the rotation speed of the copper roller is 22 r / min, the cooling rate is 1×10 5 °C / s, and a neodymium-iron-boron alloy rapid solidification sheet is obtained.

[0222] The average thickness of the neodymium-iron-boron alloy rapid solidification sheet is 0.35 mm, and the proportion of the thickness in the range of 0.20-0.28 mm is 25%. The proportion of the main phase of the neodymium-iron-boron alloy rapid solidification sheet is 83%, and the Nd-rich phase is distributed between the main phase grains; the main phase is columnar crystal, the average size of the short axis is 3.92 μm, and the average size of the long axis is 116 μm.

[0223] (2) The neodymium-iron-boron alloy rapid solidification sheet is placed in a hydrogen decrepitation furnace, the hydrogen content is controlled to be lower than 800 ppm, a neodymium-iron-boron coarse powder with a D50 of 79 μm is obtained; the neodymium-iron-boron coarse powder is placed in an air flow mill, the oxygen content is controlled to be lower than 40 ppm, the rotation speed of the classification wheel is 2140 rpm, and a neodymium-iron-boron powder is obtained; the D50 of the neodymium-iron-boron powder is 3.94 μm, the D10 is 2.26 μm, and the D90 is 4.67 μm, and the proportion of the neodymium-iron-boron powder satisfying the ratio of the short diameter to the long diameter of (0.8-1):1 is 65%.

[0224] (3) The same as step (3) of Example 1.

[0225] The magnetic properties of the high-performance sintered neodymium-iron-boron magnet in the present comparative example are shown in Table 1.

[0226] Comparative Example 3

[0227] The preparation method of the neodymium-iron-boron magnet based on the matching of the powder particle size and the main phase grain size in the present comparative example comprises:

[0228] (1) The neodymium-iron-boron alloy rapid solidification sheet of step (1) of Example 15 is used, and the average size of the short axis is 1.54 μm;

[0229] (2) The neodymium-iron-boron alloy rapid solidification sheet is placed in a hydrogen decrepitation furnace, the hydrogen content is controlled to be lower than 800 ppm, a neodymium-iron-boron coarse powder is obtained; the neodymium-iron-boron coarse powder is placed in an air flow mill, the oxygen content is controlled to be lower than 40 ppm, the rotation speed of the classification wheel is 3160 rpm, and a neodymium-iron-boron powder is obtained; the D50 of the neodymium-iron-boron powder is 2.73 μm, the D10 is 0.86 μm, and the D90 is 3.27 μm, and the proportion of the neodymium-iron-boron powder satisfying the ratio of the short diameter to the long diameter of (0.8-1):1 is 53%.

[0230] (3) The same as step (3) of Example 1.

[0231] The magnetic properties of the high-performance sintered Nd-Fe-B magnets in this comparative example are shown in Table 1.

[0232] Comparative Example 4

[0233] The preparation method of the Nd-Fe-B magnet based on matching the powder particle size and the main phase grain size in this comparative example includes:

[0234] (1) According to the composition design of the target sintered Nd-Fe-B magnet, the chemical formula Nd 30.5 B 0.93 Co 0.5 Cu 0.1 Ga 0.05 Zr 0.05 Fe 67.87 The Nd-Fe-B alloy raw material is prepared, and the Nd-Fe-B alloy raw material is placed in a vacuum induction melting furnace under vacuum environment and heated to complete melting, obtaining an alloy liquid with a temperature of 1470°C. After the alloy liquid temperature is reduced to 1400°C, the alloy liquid is guided to the surface of a copper roller for tape casting, wherein the copper roller rotates at a speed of 28 r / min, the cooling rate is 3×10 5 °C / s, and an Nd-Fe-B alloy rapid solidification sheet is obtained.

[0235] The average thickness of the Nd-Fe-B alloy rapid solidification sheet is 0.25 mm, and the proportion of the thickness in the range of 0.20-0.28 mm is 87%. The proportion of the main phase of the Nd-Fe-B alloy rapid solidification sheet is 70%, and the Nd-rich phase is distributed between the main phase grains; the main phase is columnar crystal, the average size of the short axis is 2.76 μm, and the average size of the long axis is 152 μm.

[0236] (2) The Nd-Fe-B alloy rapid solidification sheet is placed in a hydrogen crusher, and the hydrogen content is controlled to be less than 800 ppm, obtaining a Nd-Fe-B coarse powder with a D50 of 55 μm; the Nd-Fe-B coarse powder is placed in an air jet mill, and the oxygen content is controlled to be less than 40 ppm, and the grading wheel rotates at a speed of 3200 rpm, obtaining a Nd-Fe-B powder; the D50 of the Nd-Fe-B powder is 2.74 μm, the D10 is 1.35 μm, and the D90 is 3.37 μm, and the proportion of the ratio of the short diameter to the long diameter of (0.8-1):1 is 68%.

[0237] (3) The same as step (3) of Example 1.

[0238] The magnetic properties of the high-performance sintered Nd-Fe-B magnets in this comparative example are shown in Table 1.

[0239] Comparative Example 5

[0240] The preparation method of the Nd-Fe-B magnet based on matching the powder particle size and the main phase grain size in this comparative example includes:

[0241] (1) The neodymium-iron-boron alloy rapidly solidified flake with an average size of short axis of 3.92 μm was used in the step (1) of the comparative example 2;

[0242] (2) The neodymium-iron-boron alloy rapidly solidified flake was put into a hydrogen decrepitation furnace, and the hydrogen content was controlled to be less than 800 ppm to obtain a neodymium-iron-boron coarse powder; the neodymium-iron-boron coarse powder was put into an air jet mill, and the oxygen content was controlled to be less than 40 ppm, and the rotational speed of the classification wheel was 4350 rpm to obtain a neodymium-iron-boron powder; the neodymium-iron-boron powder had a D50 of 1.59 μm, a D10 of 0.72 μm, and a D90 of 2.61 μm, and the ratio of the short diameter to the long diameter was (0.8-1) : 1, and the proportion of the neodymium-iron-boron powder was 40%.

[0243] (3) The same as the step (3) of the example 1.

[0244] The magnetic properties of the high-performance sintered neodymium-iron-boron magnet in the comparative example were shown in Table 1.

[0245] Comparative example 6

[0246] The preparation method of the neodymium-iron-boron magnet based on the matching of the powder particle size and the main phase grain size in the comparative example included:

[0247] (1) The neodymium-iron-boron alloy rapidly solidified flake with an average size of short axis of 2.70 μm was used in the step (1) of the example 1;

[0248] (2) The neodymium-iron-boron alloy rapidly solidified flake was put into a hydrogen decrepitation furnace, and the hydrogen content was controlled to be less than 800 ppm to obtain a neodymium-iron-boron coarse powder; the neodymium-iron-boron coarse powder was put into an air jet mill, and the oxygen content was controlled to be less than 40 ppm, and the rotational speed of the classification wheel was 4280 rpm to obtain a neodymium-iron-boron powder; the neodymium-iron-boron powder had a D50 of 1.68 μm, a D10 of 0.74 μm, and a D90 of 2.95 μm, and the ratio of the short diameter to the long diameter was (0.8-1) : 1, and the proportion of the neodymium-iron-boron powder was 45%.

[0249] (3) The same as the step (3) of the example 1.

[0250] The magnetic properties of the high-performance sintered neodymium-iron-boron magnet in the comparative example were shown in Table 1.

[0251] Table 1, the magnetic properties table of the high-performance sintered neodymium-iron-boron magnet

[0252]

[0253]

[0254] In summary, the core advantage of the present application is to realize the accurate correspondence between the average size of the main phase short axis in the rapid solidification sheet and the D50 particle size of the Nd-Fe-B powder by establishing a synergistic regulation mechanism between the rapid solidification and the powdering process, and to fundamentally solve the performance limitations caused by size mismatch in the traditional process, and to significantly improve the powder microstructure, the comprehensive performance of the magnet and the stability of the industrial production. Figure 6 It can be seen that when the average size of the main phase short axis in the rapid solidification sheet and the D50 particle size of the Nd-Fe-B powder are completely matched and infinitely close to 2.7 microns, the magnetic performance is significantly improved.

[0255] In terms of powder microstructure, if the main phase short axis size and the powder D50 particle size are not matched, the powdering process is easy to cause transgranular fracture of the main phase, expose the main phase grain section, and the grain boundary rare earth-rich phase is easy to be mechanically stripped or dispersed, causing incomplete coating of the fine powder particle surface, thereby introducing potential defects of the magnet performance. The present application precisely controls the main phase short axis size by regulating the rapid solidification process parameters, and synergistically optimizes the powdering parameters to realize effective matching with the target D50 particle size of the powder. This strategy promotes the powder particles to be more inclined to fracture along the grain boundary, maximizes the integrity of the main phase structure, and enables the rare earth-rich phase to be uniformly and continuously coated on the powder surface, laying a foundation for forming an excellent powder microstructure.

[0256] In terms of the core performance of the magnet, size mismatch can weaken the magnetic isolation effect between the main phase grains during sintering, increase the magnetic moment reversal interference, not only cause the coercive force (Hcj) to decrease significantly, but also the main phase fracture can form a magnetic flux leakage path, making it difficult to maintain the remanence (Br), and ultimately limiting the improvement of the magnetic energy product ((BH)max). By matching the main phase and the powder particle size, the present application forms a complete and continuous rare earth-rich phase coating layer, effectively isolates adjacent main phase grains, and weakens the magnetic coupling effect, thereby significantly enhancing the demagnetization resistance of the magnet. At the same time, the complete main phase structure helps to reduce the magnetic flux loss, maintain or improve the remanence level, realize the synergistic optimization of the coercive force, the remanence and the magnetic energy product, and meet the strict requirements of high-performance applications for the performance of the magnet.

[0257] In terms of the stability of industrial production, due to the lack of systematic regulation of size matching in the traditional process, the powder microstructure fluctuates greatly, resulting in significant differences in the performance of the magnet between batches, and it is difficult to improve the product consistency and the yield. By establishing a quantifiable and repeatable process control standard for the matching relationship between the main phase grain size and the powder particle size, the present application can realize the stable preparation of high-quality powder by only slightly adjusting the existing rapid solidification furnace and air jet mill process parameters, significantly reducing the performance fluctuation risk, and improving the production stability and the product yield. This method does not require complex equipment modification, and provides a practical technical path for the large-scale and low-cost manufacturing of high-performance Nd-Fe-B magnets.

[0258] Aspects, embodiments, features of the present invention are to be considered illustrative only and not restrictive in all respects. The scope of the present invention is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art, and the embodiments are not to be considered limited to the specific embodiments set forth herein, but rather are to be given the full scope of the claims.

[0259] In the preparation method of the present invention, the order of the steps is not limited to the listed order, and for those skilled in the art, the order of the steps can be changed without creative effort, and such changes are within the protection scope of the present invention. In addition, two or more steps or actions can be performed simultaneously.

[0260] Finally, it should be noted that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the scope of the embodiments of the present invention. Those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, and it is not necessary or possible to fully describe all embodiments here. Any obvious changes or variations derived from the spirit of the present invention are still within the protection scope of the present invention, and any additional limitations are contrary to the spirit of the present invention.

Claims

1. A method for producing a neodymium-iron-boron magnet based on matching the powder particle size to the main phase grain size, characterized by, The method for preparing the neodymium-iron-boron magnet comprises: (1) using a rapid solidification process to prepare a neodymium-iron-boron alloy rapid solidification piece; The proportion of the main phase in the neodymium-iron-boron alloy rapid solidification piece is > 85%, and the main phase is columnar crystal, the average size of the short axis of which is 2.1-3.4 μm; (2) sequentially performing hydrogen crushing and air flow grinding on the neodymium-iron-boron alloy rapid solidification piece to obtain a neodymium-iron-boron powder; the difference between the D50 particle size of the neodymium-iron-boron powder and the average size of the short axis of the main phase in step (1) is ≤ 1 μm; the proportion of the neodymium-iron-boron powder satisfying the ratio of the short diameter to the long diameter of (0.8-1): 1 is > 50% in the neodymium-iron-boron powder. (3) performing oriented forming, press forming, sintering treatment and tempering treatment on the neodymium-iron-boron powder to obtain a high-performance sintered neodymium-iron-boron magnet.

2. The method of claim 1, wherein the powder particle size is matched to the main phase grain size. The rapid solidification process in step (1) comprises: after being dosed according to the component design of a target sintered neodymium-iron-boron magnet, the alloy liquid is obtained by heating and melting, and the temperature of the alloy liquid is 1430-1490 ℃; after the temperature of the alloy liquid is reduced to 1350-1400 ℃, strip casting is performed to obtain a neodymium-iron-boron alloy rapid solidification piece.

3. The method of claim 2, wherein the powder is prepared by a method comprising: The chemical formula of the target sintered neodymium-iron-boron magnet is RE a B b M c Fe 100-(a+b+c) , wherein RE is a rare earth element, including one or more of Pr, Nd, Dy, Tb, La, Ce, Y, Ho and Gd, M includes one or more of Cu, Al, Ga, Co, Zr and Ti, and 29≤a≤31, 0.91≤b<1.1, 0.5≤c≤4. ​ 4. The method of claim 1, wherein the powder particle size is matched to the main phase grain size. The proportion of the main phase in the neodymium-iron-boron alloy rapid solidification piece in step (1) is 88-92%.

5. The method of claim 1, wherein the powder-based neodymium-iron-boron magnet is prepared by matching the particle size of the powder with the grain size of the main phase. The thickness of the neodymium-iron-boron alloy rapid solidification piece in step (1) is 0.15-0.35 mm; wherein, the proportion of the neodymium-iron-boron alloy rapid solidification piece satisfying 0.20-0.28 mm is ≥ 70%.

6. The method of claim 1, wherein the powder-based neodymium-iron-boron magnet is prepared by a process comprising: The rare earth-rich phase in the neodymium-iron-boron alloy rapid solidification piece in step (1) is uniformly distributed between the main phases. ​ 7. The method of claim 1, wherein the powder-based neodymium-iron-boron magnet is prepared by a process comprising: The size of the short axis of the main phase in step (1) is 0.8-6.3 μm, the average size of the short axis is 2.1-3.4 μm, and the size of the long axis is 30-200 μm, and the average size of the long axis is 140-180 μm. ​ 8. The method of claim 1, wherein the powder-based neodymium-iron-boron magnet is prepared by a process comprising: The average size of the short axis of the main phase in step (1) is 2.7 ± 0.3 μm. ​ 9. The method of claim 1, wherein the powder-based neodymium-iron-boron magnet is prepared by a process comprising: The hydrogen content in the hydrogen crushing in step (2) is lower than 800 ppm; and the oxygen content in the air flow grinding in step (2) is lower than 40 ppm. ​ 10. The method of claim 1, wherein the powder-based neodymium-iron-boron magnet is prepared by a process comprising: The rotating speed of the classification wheel in the air flow grinding in step (2) is 2000-5000 rpm. ​ 11. The method of claim 1, wherein the powder-based neodymium-iron-boron magnet is prepared by a process comprising: In the neodymium-iron-boron powder in step (2), the proportion of the neodymium-iron-boron powder satisfying the ratio of the short diameter to the long diameter of (0.8-1): 1 is > 65%. ​ 12. The method of claim 1, wherein the powder-based neodymium-iron-boron magnet is prepared by a process comprising: The oriented forming in step (3) comprises: pre-press forming under the condition that the magnetic field intensity is > 1.5 T to obtain a pre-press blank; and the press forming in step (3) is isostatic pressing, which comprises: isostatic pressing under 200-400 Mpa for 100-600 s to obtain a press-formed blank. ​ 13. The method of claim 1, wherein the powder-based neodymium-iron-boron magnet is prepared by a process comprising: The sintering temperature of the sintering treatment in step (3) is 980-1200 ℃, and the sintering time is 1-12 h; and the tempering temperature of the tempering treatment in step (3) is 200-1200 ℃, and the time is 1-48 h. ​ 14. A high performance sintered neodymium-iron-boron magnet, characterized in that The method for preparing the neodymium-iron-boron magnet based on the matching of the powder particle size and the main phase grain size is prepared by any one of the methods for preparing the neodymium-iron-boron magnet based on the matching of the powder particle size and the main phase grain size in claims 1-13.

15. A high performance sintered NdFeB magnet prepared according to the method of any one of claims 1 to 13, or the use of a high performance sintered NdFeB magnet according to claim 14 in the field of electrical machines.

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