Neodymium-iron-boron magnet for super-high-speed motor and preparation method and application thereof

Abstract

The present application relates to a kind of neodymium-iron-boron magnets for ultra-high-speed motor, comprising: 30.0wt. %-35.0wt. % of R;0.9wt. %‑1.2wt. % of B;0.1wt. %‑0.5wt. % of Mf;And the balance of T and inevitable impurity elements;And satisfy wherein, the neodymium-iron-boron magnet for ultra-high-speed motor has main phase R2T14B, grain boundary rich R phase and the Mf precipitated phase of point distribution, and the quantity percentage content of the Mf precipitated phase distributed in the grain boundary rich R phase is not less than 99%. The neodymium-iron-boron magnet for ultra-high-speed motor of the present application keeps the magnetic property Br not less than 13.2kGs, Hcj between 15kOe-23kOe, bending strength is increased to about 580MPa, meet the high reliability demand of ultra-high-speed motor.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet technology, and in particular to a neodymium iron boron magnet for ultra-high speed motors, its preparation method, and its application. Background Technology

[0002] In recent years, high-end equipment such as new energy vehicles, flywheel energy storage, and aero engines have been developing towards high power density and ultra-high speed. Ultra-high speed motors (speed not less than 30,000 r / min) have placed stringent requirements on rotor magnets to simultaneously achieve high magnetic properties (high maximum energy product, high intrinsic coercivity) and excellent mechanical properties (high bending strength, high fracture toughness). Sintered NdFeB permanent magnets are considered the first choice due to their highest room temperature energy product, but their inherent brittleness and strong tendency to crack along grain boundaries make them prone to breakage and failure under high-speed centrifugal force and alternating hot and cold loads, becoming a bottleneck restricting the reliability and lifespan of ultra-high speed motors.

[0003] To improve the mechanical properties of NdFeB magnets, existing technologies mainly employ alloying strengthening, grain refinement, and surface coating or metal cladding. For alloying, elements such as Al, Cu, Ga, Ti, Nb, and Zr are often added to the alloy, relying on the formation of non-magnetic borides or enrichment in the grain boundary phase to improve grain boundary bonding strength. However, these high-melting-point elements often form large (micrometer-scale) rod-shaped or fibrous borides, such as (Ti,Nb)B2 and ZrB2, mainly distributed at the triangular grain boundaries where three grains meet. Their effect on strengthening the thin grain boundaries between the two main phases that determine fracture behavior is minimal, resulting in limited overall strengthening efficiency. Grain refinement is achieved by lowering the sintering temperature or adding inhibitors such as Nb and Zr, which can improve strength to some extent. However, excessive cooling sacrifices sintering density and magnetic properties, and uneven distribution of inhibitors can easily induce localized coarse grains. While surface coating or metal cladding can suppress surface crack initiation, it cannot change the intergranular brittle fracture mechanism inside the magnet.

[0004] Recent studies have found that the strengthening effect of the second phase depends not only on its content but also on the morphology, size, and distribution of the precipitated phase. Point-like nanoprecipitates, compared to traditional rod-like phases, have advantages such as small size, high curvature, and uniform dispersion in thin grain boundary phases. They can effectively pin grain boundaries and hinder crack propagation, while exhibiting weak pinning effect on magnetic domain walls and minimal deterioration of magnetic properties. However, existing processes struggle to stably obtain high-melting-point element precipitates that are "point-like, nanoscale, and highly distributed in a thin grain boundary between the two main phases" in industrial production. The reasons include: firstly, a narrow compositional window requires precise control of the contents of multiple components such as Ti, Nb, and Zr, matching them with the total rare earth element content; otherwise, coarse rod-like phases may form or the liquid phase content may be reduced, leading to incomplete sintering. Secondly, a strict process window exists, and the diffusion and segregation behavior of high-melting-point elements throughout the melting, powdering, and sintering processes is complex, making it difficult to achieve controllable distribution of the precipitated phase using traditional single-stage sintering.

[0005] Therefore, how to specifically strengthen the thin grain boundary phase between the two main phase grains while ensuring high magnetic performance has become the key to improving the reliability of NdFeB magnets under ultra-high speed conditions, and this is also the problem that this invention focuses on solving. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a neodymium iron boron magnet for ultra-high-speed motors, its preparation method, and its application.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention is to provide a neodymium iron boron magnet for ultra-high-speed motors, comprising, by weight percentage:

[0009] 30.0 wt.% to 35.0 wt.% of R, wherein R represents at least one of Y, La, Ce, Pr, Nd, Gd, Tb, Dy, or Ho, and wherein R includes at least the Nd element;

[0010] 0.9 wt.% - 1.2 wt.% of B, where B represents element B;

[0011] 0.1 wt.% to 0.5 wt.% of Mf, wherein Mf represents at least two of Ti, Zr, or Nb, and wherein Mf includes at least 0.05 wt.% to 0.2 wt.% of the Ti element.

[0012]

[0013] Where, k∈[9,50]; [Zr] represents the mass percentage content of the Zr element; [Nb] represents the mass percentage content of the Nb element; [R] represents the mass percentage content of the R (rare earth element);

[0014] Furthermore, This indicates the ratio of Zr atoms in the R-rich phase at the grain boundaries of neodymium iron boron magnets used in ultra-high-speed motors. This represents the atomic ratio of Nb in the R-rich phase at the grain boundaries of NdFeB magnets used in ultra-high-speed motors; 27% represents the R2T phase that forms the main phase in NdFeB magnets used in ultra-high-speed motors. 14 The mass percentage of rare earth elements in B, therefore This indicates the atomic ratio of rare earth elements in the R-rich phase at the grain boundaries of NdFeB magnets for ultra-high-speed motors; therefore, Equation I indicates that the atomic ratio of rare earth elements in the R-rich phase at the grain boundaries of NdFeB magnets for ultra-high-speed motors is 9-50 times the sum of the atomic ratios of Zr and Nb.

[0015] The remaining amount of T and unavoidable impurity elements, wherein T represents at least one of Fe or Co, and T includes at least Fe, wherein the mass percentage of Fe in T is not less than 80.0 wt.%;

[0016] The neodymium iron boron magnet for the ultra-high speed motor has a main phase R2T. 14 B. Grain boundary R-rich phase and Mf precipitates distributed in a dotted pattern, wherein the percentage of the Mf precipitates distributed in the grain boundary R-rich phase is not less than 99%.

[0017] In this invention, a trace amount (0.05 wt.% - 0.2 wt.%) of Ti element is used as a grain boundary site occupant in NdFeB magnets for ultra-high-speed motors, taking advantage of its smaller atomic radius to preferentially enter thin-layer grain boundaries; and based on the mass percentage [R] of rare earth elements in NdFeB magnets for ultra-high-speed motors, the content of Zr element and / or Nb element is precisely matched according to Formula I to form a high-melting-point Mf precipitate phase and control its growth driving force.

[0018] Preferably, the product further comprises, by mass percentage, 0.01 wt.% to 3.5 wt.% of M, wherein M represents at least one of Al, Mn, Ni, Cu, Zn, Ga, or Sn elements.

[0019] Preferably, the grain boundary R-rich phase includes: located at the three main phases R2T 14 The triangular grain boundary phase FR1 at the B grain boundary and the R2T phase located between the two main phases 14 The thin grain boundary phase FR2 between B grains; wherein...

[0020] The percentage of the Mf precipitates distributed in the thin grain boundary phase FR2 is not less than 30%.

[0021] Preferably, the mass percentage of Mf in the Mf precipitated phase is not less than 8.0 wt.%.

[0022] A second aspect of the present invention is to provide a method for preparing a neodymium iron boron magnet for an ultra-high-speed motor as described above, comprising the steps of:

[0023] S1. Melt the raw materials according to the element mass percentage of the neodymium iron boron magnet for the ultra-high speed motor to obtain the casting sheet;

[0024] S2. The casting sheet is subjected to heat treatment, hydrogen crushing treatment, and air jet milling treatment in sequence to obtain fine powder;

[0025] S3. The fine powder is subjected to orientation forming, sintering and aging treatment in sequence to obtain the neodymium iron boron magnet for ultra-high speed motor.

[0026] Preferably, the heat treatment temperature is 800℃-1000℃, and the heat treatment duration is 1h-2h.

[0027] This invention achieves the pre-precipitation of Mf nanocrystals in a cast wafer through heat treatment, and then uniformly embeds them into the R-rich phase at the grain boundaries through hydrogen crushing and air jet milling.

[0028] Preferably, the sintering process includes:

[0029] P1. Heat to 400℃-500℃ at a heating rate of 8℃ / min-10℃ / min and hold for 1h-4h.

[0030] P2. Heat to 700℃-800℃ at a heating rate of 8℃ / min-10℃ / min and hold for 1h-3h.

[0031] P3. Heat to 950℃-1000℃ at a heating rate of 5℃ / min-8℃ / min and hold for 0.5h-1h, then cool down to 780℃-800℃ and hold for 0.5h-1h.

[0032] P4. After repeating step P3 several times, heat to the sintering temperature Tf at a heating rate of 5℃ / min-8℃ / min and hold for 3h-8h, then perform cooling treatment; among which,

[0033] When [R] / wt.% ∈ [30, 32], the sintering temperature Tf / ℃ ∈ [1060, 1090];

[0034] When [R] / wt.% ∈ [32,33], the sintering temperature Tf / ℃ ∈ [1040,1080];

[0035] When [R] / wt.%∈[33,35], the sintering temperature Tf / ℃∈[1030,1070].

[0036] Preferably, step P3 is repeated 3-10 times.

[0037] Furthermore, step P3 is repeated 5-8 times.

[0038] This invention utilizes the reciprocating migration and capillary force of the grain boundary phase during repeated step P3 to transport and pin Mf nanocrystals to the thin grain boundary phase FR2; through step P4, the Mf nanocrystals grow into a precipitate phase with a dotted distribution of 600nm-800nm, while simultaneously inhibiting the growth of the main phase grains.

[0039] Preferably, the time-sensing process includes:

[0040] M1, first-level high-temperature aging treatment, followed by cooling treatment;

[0041] The temperature of the first-stage high-temperature aging treatment is 800℃-900℃, and the duration of the first-stage high-temperature aging treatment is 3h-6h.

[0042] M2, secondary low-temperature aging treatment, followed by cooling treatment;

[0043] The temperature of the secondary low-temperature aging treatment is 440℃-540℃, and the duration of the secondary low-temperature aging treatment is 3h-6h.

[0044] A third aspect of the present invention is to provide an application of neodymium iron boron magnets for ultra-high-speed motors as described above in ultra-high-speed motors.

[0045] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0046] The neodymium iron boron magnet for ultra-high-speed motors of the present invention, through Formula I and sintering treatment, etc., causes Mf precipitates with a dotted distribution of 600nm-800nm ​​to be distributed in the thin grain boundary phase FR2. The magnetic properties are maintained at Br not less than 13.2kGs and Hcj between 15kOe-23kOe, and the bending strength is improved to about 580MPa, which meets the high reliability requirements of ultra-high-speed motors. Attached Figure Description

[0047] Figure 1 The microstructure of the neodymium iron boron magnet for ultra-high speed motor in Example 4 is shown.

[0048] Figure 2 The microstructure of the neodymium iron boron magnet for the ultra-high-speed motor in Comparative Example 1 is shown.

[0049] Figure 3 The microstructure of the neodymium iron boron magnet for the ultra-high speed motor in Comparative Example 2 is shown.

[0050] Figure 4 The microstructure morphology of the casting in Example 6 is shown. Detailed Implementation

[0051] The specific embodiments of the present invention will be described in detail below.

[0052] Unless otherwise defined, the technical or scientific terms used in the claims and description shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0053] The word "comprising" or similar terms used in the specification and claims of this patent application mean that the objects preceding "comprising" include the objects listed after "comprising" or their equivalents, and do not exclude other objects.

[0054] The numerical values ​​mentioned in this invention include all values ​​increasing one unit at a time from low to high, assuming that there is at least a two-unit interval between any lower and higher value. For example, if it is said that a component quantity or a physical quantity is better from 1 to 100, 10 to 90, and 20 to 80, it means that values ​​such as 5 to 95, 14 to 76, 23 to 67, 32 to 58, and 41 to 49 are clearly listed in this specification; for values ​​less than 1, 0.0001, 0.001, 0.01, or 0.1 are considered to be a suitable unit. The foregoing examples are for illustrative purposes only; in practice, all combinations of values ​​between the lowest and highest listed values ​​are considered to be clearly listed in this specification in a similar manner.

[0055] In embodiments of the present invention, the preparation steps of the neodymium iron boron magnet for ultra-high-speed motors include:

[0056] S1. Place the raw materials, each with a purity of not less than 99.9%, into the crucible of the vacuum induction furnace in descending order of melting point; after sealing the furnace, evacuate to 10°C. -3 Pa-10 -4 Pa, while ensuring the dew point is below -50℃; then argon gas is introduced to 30kPa-50kPa, and smelting is carried out at 1460℃-1530℃. After the material is completely melted, it is held at the temperature for 3min-5min; the temperature of the alloy liquid is reduced to 1420℃-1460℃ and held at the temperature, and then it is continuously poured through the tundish onto the surface of a water-cooled copper roller with a rotation speed of 30r / min-75r / min for rapid solidification. The resulting castings then fall into the water-cooling pan for further cooling.

[0057] S2. Place the obtained casting in a molybdenum boat or graphite box and transfer it into a heating furnace; evacuate to 10°C. -3 Pa-10 -4 After Pa, the temperature is raised to 800℃-1000℃, and after reaching the temperature, argon gas at 30kPa-50kPa is introduced and held for 1-2 hours. After the holding period, the furnace body can be cooled with the furnace or cooled to room temperature by argon air, and the cooling rate is unlimited.

[0058] The casting is placed in a reactor, and after evacuation, hydrogen gas is introduced to a positive pressure (positive pressure is the difference between absolute pressure and atmospheric pressure) of 0.1 MPa. When the casting absorbs hydrogen and the positive pressure in the reactor drops to 0.05 MPa-0.06 MPa, hydrogen is introduced again to 0.1 MPa. This process is repeated until the pressure change does not exceed 0.5% within 10 minutes, at which point hydrogen absorption saturation is determined. Then, while evacuating, the temperature is raised to 400℃-600℃ and held for 2-6 hours to completely remove hydrogen. Finally, the mixture is cooled to obtain hydrogen-crushed coarse powder.

[0059] The coarse powder from hydrogen crushing is placed in an air jet mill and placed in an inert atmosphere such as helium or nitrogen. The nozzle pressure is adjusted to 0.6MPa-0.8MPa, and the high-speed airflow drives the particles to collide with each other to produce fine powder.

[0060] The resulting fine powder can also be mixed with commercially available magnetic powder protective lubricant and / or antioxidant as needed. The amount of magnetic powder protective lubricant is 0.01%-0.1% of the mass of the fine powder, and the amount of antioxidant is 0.01%-0.14% of the mass of the fine powder.

[0061] S3. Orientation molding was completed under an orientation magnetic field of 1.8T-2.5T and a molding pressure of 30MPa-45MPa, resulting in a compact with a density of 3.6g / cm³. -3 -4.0g cm -3 ;

[0062] Optionally, the compact is subjected to cold isostatic pressing at 150MPa-180MPa to increase its density to 4.5g / cm³. -3 –4.6gcm -3 To eliminate internal cracks;

[0063] The pressed blank is placed in a vacuum sintering furnace, and the following steps are performed sequentially:

[0064] P1, at 8℃·min -1 -10℃·min -1 The temperature is increased to 400℃-500℃ at a heating rate and held for 1-4 hours.

[0065] P2, at 8℃·min -1 -10℃·min -1 The temperature is increased to 700℃-800℃ at a rising rate and held at that temperature for 1-3 hours.

[0066] P3, at 5℃·min -1 -8℃·min -1 The temperature is raised to 950℃-1000℃ at a heating rate and held for 0.5h-1h, and then cooled down to 780℃-800℃ with the furnace and held for 0.5h-1h.

[0067] P4. Repeat step P3 3-10 times, then at 5℃·min -1 -8℃·min -1 The temperature is increased to the sintering temperature Tf at a certain heating rate and held for 3-8 hours, and then cooled to obtain a dense magnet.

[0068] M1. The obtained dense magnet is first subjected to a first-level high-temperature aging treatment at 800℃-900℃ for 3h-6h, and then furnace-cooled or air-cooled to below 100℃ after the heat treatment is completed.

[0069] M2, then heat to 440℃-540℃ and hold for 3-6 hours for secondary low-temperature aging treatment. After the holding period, maintain a temperature of not less than 30℃·min. -1 The neodymium iron boron magnet for the ultra-high speed motor is obtained by cooling it to below 80°C using an air cooling rate.

[0070] After the magnet broke, samples were taken from the central area, and the composition was determined by inductively coupled plasma atomic emission spectrometry (ICP). The microstructure was observed using scanning electron microscopy (SEM), and the micro-area composition was confirmed by electron probe microanalysis (EPMA). Three-point bending specimens were prepared using a diamond internal circular slicer and a double-sided grinder, with dimensions of 25 mm (length) × 6 mm (width) × 5 mm (height) and a tolerance of ±0.01 mm. The height direction was parallel to the orientation axis. Three-point bending tests were performed according to GB / T 31967.2-2015: 10 specimens were taken per group, with a 5 mm diameter indenter and support column, a span of 14.5 mm, and a loading rate of 0.1 mm / min. The average value was taken as the bending strength. The specimens were also processed by wire cutting, double-sided grinding, and end face grinding. The magnetic properties of the cylindrical samples were measured using the NIM standard magnetic measurement system.

[0071] Examples 1-4 and Comparative Examples 1-4

[0072] The NdFeB magnets for ultra-high-speed motors in Examples 1-4 and Comparative Examples 1-4, along with their elemental mass percentages and sintering temperatures, are shown in the table below:

[0073]

[0074] In this context, serial numbers 1-4 represent Examples 1-4, serial numbers D1-D4 represent Comparative Examples 1-4, TRE represents unavoidable impurity elements, Bal represents the balance, and √ and × represent satisfaction and non-satisfaction, respectively.

[0075] The performance test results of the neodymium iron boron magnets for ultra-high-speed motors in Examples 1-4 and Comparative Examples 1-4 are shown in the table below:

[0076]

[0077]

[0078] As can be seen from the table above, except for Comparative Example 2, which had a decrease in density and a significant reduction in remanence due to the mass percentage of Mf exceeding the limits of this invention, the magnetic properties of the other groups were basically the same; however, the bending strengths differed significantly.

[0079] Specifically, the elemental mass percentage content of Examples 1-4 meets the requirements, and the Mf precipitate phase exhibits a dotted distribution of 600nm-800nm. Figure 1Example 4), uniformly dispersed in the R-rich phase at the grain boundaries, can effectively deflect crack paths and significantly improve bending strength; Comparative Example 1 contains only 0.15 wt.% Ti, without the introduction of Zr and / or Nb elements, and its Mf precipitates are distributed in a point-like pattern of ~200 nm. Figure 2 While it can improve strength, its size is too small, limiting its crack-resistant effect; Comparative Examples 2 and 3 contain Mf2, but do not satisfy Equation I. The Mf precipitate in Comparative Example 2 is coarse and rod-shaped. Figure 3 The Mf2 content is mainly distributed in the triangular grain boundary phase FR1, which limits the strengthening effect. The Mf2 content in Comparative Example 3 is insufficient, and the strength is comparable to that of Comparative Example 1. Comparative Example 4 lacks Ti element. Although the Mf2 content meets the requirements, it is difficult to form fine precipitates, and the strength is low. The EPMA results show that the Mf mass percentage content in the Mf precipitates of Examples 1-4 is not less than 8.0 wt.%.

[0080] In summary, the synergistic effect of appropriate amounts of Ti and Mf2 in a suitable ratio can form finely distributed high-melting-point Mf precipitates at grain boundaries, which both strengthens the grain boundaries and refines the main R2T phase. 14 B-grains significantly improve the bending strength of the magnet.

[0081] Example 5 and Comparative Example 5

[0082] The elemental mass percentages and sintering temperatures of the neodymium iron boron magnets for ultra-high-speed motors in Example 5 and Comparative Example 5 are shown in the table below:

[0083] 5 / D5 22.3 7.0 2.0 1.0 0.95 0.3 0.25 0.15 0.18 0.2 Bal 31.3 √ 1080

[0084] Wherein, serial number 5 represents Example 5, serial number D5 represents Comparative Example 5, TRE represents unavoidable impurity elements, Bal represents the balance, and √ represents satisfaction.

[0085] The difference between Example 5 and Comparative Example 5 is that step P3 in Comparative Example 5 is not repeated, that is, step P3 in Comparative Example 5 is only performed once.

[0086] The performance test results of the neodymium iron boron magnets for ultra-high-speed motors in Example 5 and Comparative Example 5 are shown in the table below:

[0087] 5 13.25 22.6 0.983 589 D5 13.26 21.3 0.979 521

[0088] SEM analysis showed that at 1 mm 2 Within the field of view, the distribution density of Mf precipitates in the NdFeB magnets for ultra-high-speed motors of Example 5 and Comparative Example 5 is 4.5 precipitates / 100 μm. 2In Example 5, 99.8% of the Mf precipitates were located in the R-rich phase at grain boundaries, while in Comparative Example 5, the percentage of Mf precipitates located in the R-rich phase at grain boundaries was 99.2%. Both showed a grain boundary-dominated distribution. Further analysis of the distribution of Mf precipitates in the R-rich phase at grain boundaries revealed that in Example 5, more than 33% of the Mf precipitates were located in the two main phases R2T. 14 The thin grain boundary phase FR2 between B grains is present, while in Comparative Example 5, only 12% of the Mf precipitates are located in this region. Since the grain boundary strength of the thin grain boundary phase FR2 is relatively low, it is a weak link in the mechanical properties of the magnet. In Comparative Example 5, the Mf precipitates are mainly retained in the triangular grain boundary phase FR1 under the existing sintering steps, resulting in limited strengthening effect. The cyclic sintering step in Example 5 causes the high melting point Mf nanocrystals to migrate with the grain boundary and be located in the thin grain boundary phase FR2 by capillary force. Subsequent high-temperature sintering causes them to grow into precipitates with a dotted distribution, which significantly strengthens the thin grain boundary and inhibits grain growth. Therefore, the bending strength and coercivity of Example 5 are higher than those of Comparative Example 5.

[0089] Example 6 and Comparative Example 6

[0090] The elemental mass percentages and sintering temperatures of the neodymium iron boron magnets for ultra-high-speed motors in Example 6 and Comparative Example 6 are shown in the table below:

[0091] 6 / D6 24.6 7.4 0.5 1.2 0.93 0.1 0.15 0.15 0.12 0.2 Bal 32.5 √ 1070

[0092] Wherein, serial number 6 represents Example 6, serial number D6 represents Comparative Example 6, TRE represents unavoidable impurity elements, Bal represents the balance, and √ represents satisfaction.

[0093] The difference between Example 6 and Comparative Example 6 is that the heat treatment in step S2 is not performed in Comparative Example 6, that is, the casting obtained in step S1 is directly subjected to hydrogen crushing treatment in Comparative Example 6.

[0094] The performance test results of the neodymium iron boron magnets for ultra-high-speed motors in Example 6 and Comparative Example 6 are shown in the table below:

[0095] 6 13.65 17.6 0.998 583 D6 13.65 17.2 0.975 552

[0096] The data in the table above show that the coercivity of the NdFeB magnet for the ultra-high-speed motor in Example 6, which underwent heat treatment, is slightly higher than that in the untreated Comparative Example 6, and its bending strength is significantly better than the latter; SEM statistical results show that at 1 mm... 2 Within the field of view, the percentage of Mf precipitates in the grain boundary-rich R phase in Example 6 (99.6%) was significantly higher than that in Comparative Example 6 (68.5%). This is because, after heat treatment at 800℃-1000℃, high-melting-point elements preferentially precipitate in nanocrystalline form. Figure 4Subsequently, during the cyclic sintering stage, these nanocrystals migrate to the intergranular space of the main phase along with grain boundary movement, and further grow into dispersed point-like precipitates during the high-temperature sintering stage; conversely, without heat treatment, Mf and the main phase R2T 14 B grains grow synchronously, the grain refinement effect is weakened, and the precipitated phases are unevenly distributed and easily enter the grains, resulting in a decrease in mechanical properties.

[0097] Example 7 and Comparative Example 7

[0098] The elemental mass percentages and sintering temperatures of the neodymium iron boron magnets for ultra-high-speed motors in Example 7 and Comparative Example 7 are shown in the table below:

[0099] 7 26.5 6 0.5 1.0 0.95 0.3 0.2 0.1 0.18 0.2 Bal 33 √ 1070 D7 26.5 6 0.5 1.0 0.95 0.3 0.2 0.1 0.18 0.2 Bal 33 √ 1080

[0100] Wherein, serial number 7 represents Example 7, serial number D7 represents Comparative Example 7, TRE represents unavoidable impurity elements, Bal represents the balance, and √ represents satisfaction.

[0101] The performance test results of the neodymium iron boron magnets for ultra-high-speed motors in Example 7 and Comparative Example 7 are shown in the table below:

[0102] 7 13.26 20.1 0.986 579 D7 13.20 18.6 0.921 498

[0103] The sintering temperature Tf of Comparative Example 7 exceeds the range defined in this invention; the data in the table above show that Example 7 is superior to Comparative Example 7 in both magnetic and mechanical properties. This is because, with the increase of the total rare earth content, the main phase R2T... 14 B grains grow more readily, and excessively high sintering temperatures weaken the grain-refining effect of high-melting-point elements. SEM statistical results show that the average main phase R2T in Comparative Example 7... 14 B grain size (6.0 μm) and the largest principal phase R2T 14 The B grain size (20.5 μm) was significantly larger than that of Example 7 (average main phase R2T). 14 The B grain size is 4.5 μm, and the largest main phase is R2T. 14 The B grain size is 11.3 μm, and there are abnormally large grains, which causes a significant decrease in its coercivity and bending strength.

[0104] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A neodymium iron boron magnet for an ultra-high-speed motor, characterized in that, By mass percentage, it includes: R, wherein R represents at least one of the elements Y, La, Ce, Pr, Nd, Gd, Tb, Dy, or Ho, and R includes at least the Nd element; The B in B represents element B; The Mf element represents at least two of the elements Ti, Zr, or Nb, and the Mf element comprises at least 0.05 wt.% to 0.2 wt.% of the Ti element. ； in, ; This indicates the mass percentage content of the Zr element; This indicates the ratio of Zr atoms in the R-rich phase at the grain boundaries of neodymium iron boron magnets used in ultra-high-speed motors. This indicates the mass percentage content of the Nb element; This indicates the ratio of Nb atoms in the R-rich phase at the grain boundaries of neodymium iron boron magnets used in ultra-high-speed motors. This indicates the mass percentage content of R. To form the main phase R2T in neodymium iron boron magnets for ultra-high speed motors 14 The mass percentage of rare earth elements in B, therefore This indicates the ratio of rare earth element atoms in the R-rich phase at the grain boundaries of neodymium iron boron magnets used in ultra-high-speed motors. In the R-rich phase at the grain boundaries of neodymium iron boron magnets for ultra-high-speed motors, the atomic ratio of rare earth elements is 9-50 times the sum of the atomic ratios of Zr and Nb. The remaining amount of T and unavoidable impurity elements, wherein T represents at least one of Fe or Co, and T includes at least Fe, wherein the mass percentage of Fe in T is not less than 80.0 wt.%; The neodymium iron boron magnet for the ultra-high speed motor has a main phase R2T. 14 B. Grain boundary R-rich phase and Mf precipitates distributed in a dotted pattern, wherein the percentage of the Mf precipitates distributed in the grain boundary R-rich phase is not less than 99%.

2. The neodymium iron boron magnet for ultra-high-speed motors according to claim 1, characterized in that, Based on mass percentage, it also includes 0.01 wt.% to 3.5 wt.% of M, where M represents at least one of Al, Mn, Ni, Cu, Zn, Ga, or Sn elements.

3. The neodymium iron boron magnet for ultra-high-speed motors according to claim 1, characterized in that, The grain boundary R-rich phase includes: located at the three main phases R2T 14 The triangular grain boundary phase FR1 at the B grain boundary and the R2T phase located between the two main phases 14 The thin grain boundary phase FR2 between B grains; wherein... The percentage of the Mf precipitates distributed in the thin grain boundary phase FR2 is not less than 30%.

4. The neodymium iron boron magnet for ultra-high-speed motors according to claim 1 or 3, characterized in that, The mass percentage of Mf in the Mf precipitate phase is not less than 8.0 wt.%.

5. A method for preparing a neodymium iron boron magnet for an ultra-high-speed motor as described in any one of claims 1-4, characterized in that the step... include: S1. Melt the raw materials according to the element mass percentage of the neodymium iron boron magnet for the ultra-high speed motor to obtain the casting sheet; S2. The casting sheet is subjected to heat treatment, hydrogen crushing treatment, and air jet milling treatment in sequence to obtain fine powder; S3. The fine powder is subjected to orientation forming, sintering and aging treatment in sequence to obtain the neodymium iron boron magnet for ultra-high speed motor.

6. The preparation method according to claim 5, characterized in that, The heat treatment temperature is 800℃-1000℃, and the heat treatment duration is 1h-2h.

7. The preparation method according to claim 5, characterized in that, The sintering process includes: P1. Heat to 400℃-500℃ at a heating rate of 8℃ / min-10℃ / min and hold for 1h-4h. P2. Heat to 700℃-800℃ at a heating rate of 8℃ / min-10℃ / min and hold for 1h-3h. P3. Heat to 950℃-1000℃ at a heating rate of 5℃ / min-8℃ / min and hold for 0.5h-1h, then cool down to 780℃-800℃ and hold for 0.5h-1h. P4. After repeating step P3 several times, heat to the sintering temperature Tf at a heating rate of 5℃ / min-8℃ / min and hold for 3h-8h, then perform cooling treatment; among which, when At that time, sintering temperature ; when At that time, sintering temperature ; when At that time, sintering temperature .

8. The preparation method according to claim 7, characterized in that, Step P3 is repeated 3-10 times.

9. The preparation method according to claim 5, characterized in that, The timeliness processing includes: M1, first-level high-temperature aging treatment, followed by cooling treatment; The temperature of the first-stage high-temperature aging treatment is 800℃-900℃, and the duration of the first-stage high-temperature aging treatment is 3h-6h. M2, secondary low-temperature aging treatment, followed by cooling treatment; The temperature of the secondary low-temperature aging treatment is 440℃-540℃, and the duration of the secondary low-temperature aging treatment is 3h-6h.

10. The application of a neodymium iron boron magnet for an ultra-high speed motor as described in any one of claims 1-4 in an ultra-high speed motor.

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