A sintered rare earth permanent magnet material with high magnetic energy product and low temperature coefficient and a preparation method thereof

Abstract

The application relates to a high-magnetic-energy-product low-temperature-coefficient sintered rare earth permanent magnet material and a preparation method thereof, and belongs to the technical field of rare earth permanent magnet materials. The application discloses a high-magnetic-energy-product low-temperature-coefficient sintered rare earth permanent magnet material. The composition of the sintered rare earth permanent magnet material comprises the following components in percentage by weight: LRE: 20-32%, HRE: 1-6%, Co: 19-25%, B: 0.9-1.2%, Cu: 0-1%, Al: 0-1%, Zr: 0-1%, and the balance of Fe; LRE is one or both of light rare earth Pr and Nd; HRE is one or more of heavy rare earth Gd, Tb, Dy and Ho; the high-magnetic-energy-product low-temperature-coefficient sintered rare earth permanent magnet material comprises a main phase and a grain boundary phase; the main phase has a core-shell structure; in a region of 0-500 mu m radially inward from the surface layer of the sintered rare earth permanent magnet material, the shell thickness of the main phase with the core-shell structure decreases with the increase of the distance from the surface of the sintered rare earth permanent magnet material; the cobalt-rich, iron-rich and rare earth-rich phase in the grain boundary phase accounts for more than 70% of the total mass of the grain boundary phase.

Description

Technical Field

[0001] This invention belongs to the field of rare earth permanent magnet materials technology, and relates to a high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material and its preparation method. Background Technology

[0002] Since the advent of Nd-Fe-B magnets in 1984, the application of sintered Nd-Fe-B magnets has rapidly expanded to various fields. Neodymium iron boron rare-earth permanent magnet materials have achieved a maximum magnetic energy product exceeding 54 MGOe, making them the undisputed king of magnets. However, their Curie temperature is relatively low (generally not exceeding 360℃), and their temperature stability is relatively poor (remanence temperature coefficient between -0.09 and -0.12% / ℃), making it difficult to meet the requirements of many high-temperature applications. To better meet the requirements of core control devices in fields such as electric vehicles, wind power generation, nuclear energy applications, and aerospace for the performance stability, reliability, and high heat resistance of rare-earth permanent magnet materials, researching the main factors affecting the thermal stability of magnets and their mechanisms of action has significant academic and practical value.

[0003] Currently, a typical method to increase the operating temperature of NdFeB magnets is to add heavy rare earth elements such as dysprosium or terbium, which significantly improves the magnet's coercivity, allowing it to maintain sufficient resistance to demagnetization even at higher operating temperatures. While this method improves the temperature stability of high-coercivity magnets, the magnetic properties still decrease relatively quickly with increasing temperature because the Curie temperature is not significantly increased, resulting in poor temperature stability.

[0004] Therefore, obtaining magnets that possess both high magnetic energy product and good temperature stability to expand the application fields of neodymium iron boron is a current challenge. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems in the prior art by proposing a high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material containing a main phase and a grain boundary phase. The grain boundary phase has a large proportion of cobalt-rich, iron-rich, and rare earth-rich phases, ensuring a low remanence temperature coefficient. Furthermore, the coercivity is optimized through grain boundary diffusion.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A high-energy-product, low-temperature-coefficient sintered rare-earth permanent magnet material, wherein the composition of the sintered rare-earth permanent magnet material, by weight percentage, comprises: LRE: 20-32%, HRE: 1-6%, Co: 19-25%, B: 0.9-1.2%, Cu: 0-1%, Al: 0-1%, Zr: 0-1%, with the balance being Fe;

[0008] LRE is one or both of light rare earth elements Pr and Nd;

[0009] HRE is one or more of the heavy rare earth elements Gd, Tb, Dy, and Ho;

[0010] The high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material includes a main phase and a grain boundary phase, wherein the grain boundary phase isolates and / or coats the main phase.

[0011] The main phase has a core-shell structure, which includes a core and a shell, with the shell located outside the main phase.

[0012] In the region radiating inward from the surface of the sintered rare earth permanent magnet material within a range of 0–500 μm, the shell thickness of the main phase with a core-shell structure decreases as the distance from the surface of the sintered rare earth permanent magnet material increases.

[0013] The grain boundary phase includes a rare earth-rich phase and a very small amount of a boron-rich phase. The rare earth-rich phase includes an iron- and cobalt-poor rare earth-rich phase and a cobalt- and iron-rich rare earth-rich phase, wherein the cobalt- and iron-rich rare earth-rich phase accounts for more than 70% of the total mass of the grain boundary phase.

[0014] In the magnet of this invention, the cobalt-rich, iron-rich, and rare-earth-rich phases account for a high proportion of the grain boundary phase, and the high cobalt content in the main phase can ensure a low remanence temperature coefficient.

[0015] The main phase with a core-shell structure of this invention has a large distribution depth on the magnet surface, which is beneficial to improving the coercivity of the magnet; and as the distribution depth increases, the thickness of the shell layer decreases, which is beneficial to ensuring that the magnet has sufficient high remanence and high magnetic energy product.

[0016] The wettability of the grain boundary phase is related to its composition. Higher wettability is beneficial to grain boundary diffusion. In this invention, the addition of trace elements Cu and Al to the raw materials makes the grain boundary phase of the magnet more wettable, which is beneficial to ensuring the shell thickness during subsequent grain boundary diffusion.

[0017] Preferably, the content is 0.2% ≤ Cu + Al ≤ 0.4%; and the content is 0.3% ≤ Cu + Al + Zr < 0.6%.

[0018] Preferably, the main phase is a main phase grain with a RE:(Fe,Co):B = 2:14:1 structure, where RE includes light rare earth LRE and heavy rare earth HRE.

[0019] Preferably, the main phase accounts for 92-96% of the total mass of the sintered rare earth permanent magnet material.

[0020] Preferably, the mass of heavy rare earth elements in the shell of the main phase accounts for 0.01 to 2% of the total mass of the sintered rare earth permanent magnet material.

[0021] Preferably, the cobalt content in the cobalt-rich, iron-rich, and rare-earth-rich phase of the grain boundary phase is higher than the cobalt content in the high magnetic energy product and low temperature coefficient sintered rare-earth permanent magnet material.

[0022] The cobalt content in the iron- and cobalt-poor rare-earth-rich phase of the grain boundary phase is much lower than that in the cobalt content of sintered rare-earth permanent magnet materials with high magnetic energy product and low temperature coefficient.

[0023] The cobalt content in the core of the main phase is slightly higher than or close to the cobalt content in high magnetic energy product low temperature coefficient sintered rare earth permanent magnet materials.

[0024] The cobalt content of the shell layer of the main phase is slightly higher than or close to the cobalt content in high energy product, low temperature coefficient sintered rare earth permanent magnet materials.

[0025] Preferably, the composition of the high magnetic energy product, low temperature coefficient sintered rare earth permanent magnet material is as follows, by weight percentage: LRE a HRE b Co c M d B e Fe 1-a-b-c-d-e ;

[0026] LRE is one or both of light rare earth elements Pr and Nd;

[0027] HRE is one or more of the heavy rare earth elements Gd, Tb, Dy, and Ho;

[0028] M is one or more of Cu, Al, and Zr;

[0029] 20% ≤ a ≤ 32%, 1% ≤ b ≤ 6%, 19% ≤ c ≤ 25%, 0% ≤ d ≤ 3%, 0.9% ≤ e ≤ 1.2%.

[0030] Preferably, the shell composition of the main phase, by weight percentage, is: LRE f HRE g Co h B i Fe 1-f-g-h-i ;

[0031] LRE is one or both of light rare earth elements Pr and Nd;

[0032] HRE is one or more of the heavy rare earth elements Gd, Tb, Dy, and Ho;

[0033] 15%≤f≤22%, 6%≤g≤9%, 19%≤h≤25%, 0.9%≤i≤1.2%, 50%≤1-fghi≤55%.

[0034] Preferably, the core component of the main phase, by weight percentage, is: LRE k HRE m Co n B p Fe 1-k-m-n-p ;

[0035] LRE is one or both of light rare earth elements Pr and Nd;

[0036] HRE is one or more of the heavy rare earth elements Gd, Tb, Dy, and Ho;

[0037] 18% ≤ k ≤ 28%, 1% ≤ m ≤ 5%, 19% ≤ n ≤ 25%, 0.9% ≤ p ≤ 1.2%, 50% ≤ 1-kmnp ≤ 55%.

[0038] Preferably, the composition of the iron- and cobalt-poor rare-earth-rich phase in the grain boundary phase is as follows (by weight percentage): LRE r HRE s Co t M u O v Fe 1-r-s-t-u-v ;

[0039] LRE is one or both of light rare earth elements Pr and Nd;

[0040] HRE is one or more of the heavy rare earth elements Gd, Tb, Dy, and Ho;

[0041] M is one or more of Cu, Al, and Zr;

[0042] 60%≤r≤85%, 0%≤s≤25%, 0%≤t≤14%, 0%≤u≤3%, 0%≤v≤1.3%, 2%≤1-rstuv≤10%.

[0043] Preferably, the composition of the cobalt-rich, iron-rich, and rare-earth-rich phase in the grain boundary phase is as follows (by weight percentage): LRE w HRE x Co y M z Fe 1-w-x-y-z ;

[0044] LRE is one or both of light rare earth elements Pr and Nd;

[0045] HRE is one or more of the heavy rare earth elements Gd, Tb, Dy, and Ho;

[0046] M is one or more of Cu, Al, and Zr;

[0047] 40%≤w≤60%, 0%≤x≤8%, 22%≤y≤30%, 0%≤z≤3%, 20%≤1-wxyz≤30%.

[0048] Preferably, the rare earth content in the shell of the main phase is 1.0 to 1.5 times that in the core of the main phase.

[0049] Preferably, the HRE content of the main phase shell is 2.2 to 2.9 times that of the main phase core.

[0050] As a preferred option, the atomic ratio of (Fe,Co):RE in the cobalt-rich, iron-rich, and rare earth-rich phase is (2-3.5):1.

[0051] In one embodiment of the present invention, the shell composition of the main phase is Nd by weight percentage. 14.0 Pr 4.6 Tb 8.5 Co 20. 5Fe 51.3 B 1.1 The core component of the main phase, by weight percentage, is Nd. 17.5 Pr 5.8 Tb 3.0 Co 21.0 Fe 51.7 B 1.0 .

[0052] In one embodiment of the present invention, the iron- and cobalt-poor rare-earth-rich phase in the grain boundary phase is Nd by weight percentage. 49.9 Pr 31.5 Co 13.9 Fe 3.2 O 0.9 Cu 0.6 The composition of the cobalt-rich, iron-rich, and rare-earth-rich phases in the grain boundary phase, by weight percentage, is Nd. 32.1 Pr 13.3 Tb 5.8 Co 25.5 Fe 21.9 Zr 1.4 .

[0053] Preferably, the thickness of the sintered rare earth permanent magnet material is 1-10 mm; the average size of the main phase is 1-10 μm; and the shell thickness of the main phase is ≤6 μm.

[0054] Further preferably, the thickness of the sintered rare earth permanent magnet material is 6-9 mm; the size of the main phase is 4-8 μm, and the shell thickness of the main phase is ≤4 μm;

[0055] More preferably, the size of the main phase is 5 μm, and the shell thickness of the main phase is ≤4 μm;

[0056] The core-shell structured main phase is distributed in a region radiating inward from the surface of the sintered rare earth permanent magnet material in the range of 0–500 μm.

[0057] The thickness of the shell layer is 3-4 μm in the region radiating inward from the surface of the sintered rare earth permanent magnet material to a depth of 0-100 μm.

[0058] The thickness of the shell layer is 1-3 μm in the region radiating inward from the surface of the sintered rare earth permanent magnet material to a depth of 100-300 μm.

[0059] The thickness of the shell layer is 0.01–1 μm in the region radiating inward from the surface of the sintered rare earth permanent magnet material to a depth of 300–500 μm.

[0060] In the region where the surface of the sintered rare earth permanent magnet material radiates inward to a depth of more than 500 μm, the thickness contrast of the shell layer is not obvious.

[0061] A method for preparing a high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material, the preparation method comprising: batching, melting, coarse grinding, fine grinding, magnetic field forming, sintering, and grain boundary diffusion; after magnetic field forming, a green embryo is obtained, and after grain boundary diffusion, a high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material is obtained.

[0062] Preferably, the preparation method includes:

[0063] (1) Ingredients: The raw materials are prepared according to the weight percentage of the rare earth permanent magnet material, wherein LRE: 20-32%, HRE: 1-6%, Co: 19-25%, B: 0.9-1.2%, Cu: 0-1%, Al: 0-1%, Zr: 0-1%, and the balance is Fe; LRE is one or more of light rare earth Pr and Nd; HRE is one or more of heavy rare earth Gd, Tb, Dy, and Ho;

[0064] (2) Melting: The raw materials are placed in a vacuum melting furnace. After multiple gas washings, the melting furnace is evacuated to 100°C. -3 ~10 - 1 Pa, then protective argon gas is introduced to maintain a pressure of -0.06 to -0.04 MPa, and rapid solidification castings are obtained after vacuum melting and cooling with cooling water;

[0065] (3) Coarse grinding: The quick-solidified casting sheet is crushed into coarse powder with a particle size of 10-500μm using a hydrogen crusher.

[0066] (4) Fine grinding: Under nitrogen protection, the coarse powder is processed into fine powder by passing it through an air jet mill with a particle size of 3-5 μm;

[0067] (5) Magnetic field forming: fine powder is oriented and formed under a magnetic field of 1.5 to 2T, and isostatic pressing is performed to obtain green body;

[0068] (6) Sintering: The green body is sintered under vacuum conditions at a temperature of 1000-1100℃ for 2-5 hours to obtain a sintered magnet.

[0069] (7) Grain boundary diffusion: the sintered magnet is subjected to heavy rare earth diffusion; the diffusion temperature is 850-960℃ and the diffusion time is 6-15h, so as to obtain a sintered rare earth permanent magnet material with high magnetic energy product and low temperature coefficient.

[0070] The presence of a cobalt-rich phase in the magnet of this invention is not conducive to improving coercivity. Therefore, coercivity is optimized by grain boundary diffusion.

[0071] Preferably, the density of the embryo is 7.6–7.8 g / cm³. 3 .

[0072] Preferably, the heavy rare earth diffusion process in (7) includes coating the magnet surface with a heavy rare earth solution of 0.1 to 5% by weight.

[0073] More preferably, the coating amount of the heavy rare earth solution is 0.5% to 1%.

[0074] The shell thickness of the main phase is closely related to the high remanence and high energy product performance of the magnet. A shell with decreasing thickness is beneficial to maintaining the overall remanence of the bulk magnet. The coating amount of the heavy rare earth diffusion source will affect the shell thickness. Therefore, it is necessary to control the content of heavy rare earth elements in the heavy rare earth solution and control the coating amount of the heavy rare earth solution.

[0075] Further preferably, the heavy rare earth elements include one or more of Gd, Tb, Dy, and Ho.

[0076] Further preferably, the heavy rare earth elements in the heavy rare earth solution are the same as those in the magnet raw material.

[0077] Further preferably, the solvent in the heavy rare earth solution includes one or more of ethanol and methanol.

[0078] Preferably, the density of the high magnetic energy product, low temperature coefficient sintered rare earth permanent magnet material is 7.7–8.0 g / cm³. 3 The Curie temperature is 500–600℃.

[0079] Preferably, the remanence temperature coefficient α of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material at 20 to 150°C is -0.07 to -0.01% / °C.

[0080] Compared with the prior art, the present invention has the following beneficial effects:

[0081] 1. The high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material of the present invention includes a main phase and a grain boundary phase. The grain boundary phase isolates and / or coats the main phase. The grain boundary phase is mainly a rare earth rich phase, which includes a cobalt-poor phase and a cobalt-rich phase. The cobalt-rich phase accounts for more than 70% of the total mass of the grain boundary phase. The high cobalt content can ensure a low remanence temperature coefficient.

[0082] 2. This invention optimizes the coercivity of magnets by diffusing heavy rare earth elements at grain boundaries; and because it uses the same heavy rare earth elements as the raw materials, it is beneficial to make full use of the heavy rare earth elements remaining in the grain boundary phase.

[0083] 3. The Zr element in the raw material of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material of this invention is beneficial to refine the grains; Al and Cu elements can improve the fluidity and wettability of the grain boundary phase. Attached Figure Description

[0084] Figure 1 This is a microstructure diagram of the surface of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material in Example 1 of the present invention.

[0085] Figure 2 This is a microstructure image of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material at a distance of 280 μm from the surface in Example 1 of the present invention.

[0086] Figure 3 This is a microstructure image of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material at a distance of 400 μm from the surface in Example 1 of the present invention. Detailed Implementation

[0087] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0088] Unless otherwise specified, the materials used in this invention are commercially available products, and the methods used are conventional technical means.

[0089] Example 1

[0090] (1) Prepare the materials according to the composition of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material designed in Table 1;

[0091] (2) Melting: The raw materials are placed in a vacuum melting furnace. After multiple gas washings, the melting furnace is evacuated to 100°C. -1 Pa, then protective argon gas was introduced to maintain a pressure of -0.06 MPa, and rapid solidification castings were obtained by vacuum melting and cooling with cooling water, with an average thickness of 0.38 mm;

[0092] (3) Coarse grinding: The quick-solidifying cast sheets are crushed into coarse powder with a particle size of 300μm using a hydrogen crusher.

[0093] (4) Fine grinding: Under nitrogen protection, the coarse powder is processed into fine powder by passing it through an air jet mill with a particle size of 4.43 μm;

[0094] (5) Magnetic field forming: The fine powder is isostatically pressed at 2T for 40s at a pressure of 180MPa to obtain a green body with a density of 5.4g / cm³.3 ;

[0095] (6) Sintering: The green body is sintered under vacuum conditions at a temperature of 1060℃ for 2 hours to obtain a sintered magnet with a thickness of 7mm.

[0096] (7) Grain boundary diffusion: heavy rare earth diffusion is performed on the sintered magnet.

[0097] The heavy rare earth diffusion process includes: acid washing of the sintered magnet surface, coating the upper and lower surfaces of the magnet with a 1% (by weight) heavy rare earth Tb solution, followed by heat treatment at 950°C for 10 hours under vacuum conditions, allowing the heavy rare earth diffusion source to enter the main phase along the grain boundaries. The resulting magnet has a density of 7.712 g / cm³. 3 ;

[0098] (8) The magnet is machined into a column shape of Ф10×7mm.

[0099] Figure 1 This is a microstructure diagram of the surface layer of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material in this embodiment. Figure 2 This is a microstructure image of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material at a distance of 280 μm from the surface in this embodiment; Figure 3 This is a microstructure image of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material at a distance of 400 μm from the surface in this embodiment; the comparison shows that the thickness of the shell decreases as the depth of the main phase distribution increases.

[0100] The magnet was tested, and the composition of the high magnetic energy product, low temperature coefficient sintered rare earth permanent magnet material, by weight percentage, was Nd. 20.25 Pr 6.75 Tb 3.5 Co 20 Cu 0.2 Al 0.1 Zr 0.2 Fe 48.04 B 0.96 ;

[0101] The shell composition of the main phase, by weight percentage, is Nd. 14.0 Pr 4.6 Tb 8.5 Co 20.5 Fe 51.3 B 1.1 The core component of the main phase, by weight percentage, is Nd. 17.5 Pr 5.8 Tb 3.0 Co 21.0 Fe 51.7 B 1.0 ;

[0102] The composition of the iron- and cobalt-poor rare-earth-rich phase in the grain boundary phase, by weight percentage, is: Nd 49.9 Pr 31.5 Co 13.9 Fe 3. 2O 0.9 Cu 0.6 The composition of the cobalt-rich, iron-rich, and rare-earth-rich phases in the grain boundary phase, by weight percentage, is as follows: Nd 32.1 Pr 13.3 Tb 5.8 Co 25.5 Fe 21.9 Zr 1.4 .

[0103] The magnetic properties of the magnet in (8) were measured using a NIM-2000 hysteresis loop tester. The specific properties are shown in Table 2.

[0104] Example 2

[0105] (1) Prepare the materials according to the composition of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material designed in Table 1;

[0106] (2) Melting: The raw materials are placed in a vacuum melting furnace. After multiple gas washings, the melting furnace is evacuated to 100°C. -1 Pa, then protective argon gas was introduced to maintain a pressure of -0.06 MPa, and rapid solidification castings were obtained by vacuum melting and cooling with cooling water, with an average thickness of 0.38 mm;

[0107] (3) Coarse grinding: The quick-solidifying cast sheets are crushed into coarse powder with a particle size of 300μm using a hydrogen crusher.

[0108] (4) Fine grinding: Under nitrogen protection, the coarse powder is processed into fine powder by passing it through an air jet mill with a particle size of 4.43 μm;

[0109] (5) Magnetic field forming: The fine powder is isostatically pressed at 2T for 40s at a pressure of 180MPa to obtain a green body with a density of 5.52g / cm³. 3 ;

[0110] (6) Sintering: The green blank is sintered under vacuum conditions at a temperature of 1060℃ for 2 hours to obtain a sintered magnet.

[0111] (7) Grain boundary diffusion: The sintered magnet is subjected to heavy rare earth diffusion; the diffusion temperature is 950℃ and the diffusion time is 10h.

[0112] The heavy rare earth diffusion process includes: coating the upper and lower surfaces of the magnet with a 1% (by weight) heavy rare earth Tb solution, followed by heat treatment at 950°C for 10 hours, allowing the heavy rare earth diffusion source to enter the main phase along the grain boundaries. The resulting magnet has a density of 7.768 g / cm³. 3;

[0113] (8) The magnet is machined into a column shape of Ф10×7mm. The magnetic properties of the magnet are measured using a NIM-2000 hysteresis loop tester. The specific properties are shown in Table 2.

[0114] Example 3

[0115] (1) Prepare the materials according to the composition of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material designed in Table 1;

[0116] (2) Melting: The raw materials are placed in a vacuum melting furnace. After multiple gas washings, the melting furnace is evacuated to 100°C. -1 Pa, then protective argon gas was introduced to maintain a pressure of -0.06 MPa, and rapid solidification castings were obtained by vacuum melting and cooling with cooling water, with an average thickness of 0.38 mm;

[0117] (3) Coarse grinding: The quick-solidifying cast sheets are crushed into coarse powder with a particle size of 300μm using a hydrogen crusher.

[0118] (4) Fine grinding: Under nitrogen protection, the coarse powder is processed into fine powder by passing it through an air jet mill with a particle size of 4.43 μm;

[0119] (5) Magnetic field forming: The fine powder is isostatically pressed at 2T for 40s at a pressure of 180MPa to obtain a green body with a density of 5.60g / cm³. 3 ;

[0120] (6) Sintering: The green blank is sintered under vacuum conditions at a temperature of 1060℃ for 2 hours to obtain a sintered magnet.

[0121] (7) Grain boundary diffusion: The sintered magnet is subjected to heavy rare earth diffusion; the diffusion temperature is 950℃ and the diffusion time is 10h.

[0122] The heavy rare earth diffusion process includes: coating the upper and lower surfaces of the magnet with a 1% (by weight) heavy rare earth Tb solution, followed by heat treatment at 950°C for 10 hours, allowing the heavy rare earth diffusion source to enter the main phase along the grain boundaries. The resulting magnet has a density of 7.812 g / cm³. 3 ;

[0123] (8) The magnet is machined into a column shape of Ф10×7mm. The magnetic properties of the magnet are measured using a NIM-2000 hysteresis loop tester. The specific properties are shown in Table 2.

[0124] Comparative Example 1

[0125] The difference from Example 1 is that heavy rare earth grain boundary diffusion is not performed.

[0126] The properties of the prepared sintered rare earth permanent magnet materials are shown in Table 2.

[0127] Comparative Examples 2-5

[0128] Compared with Example 1, the difference lies in the formulation of the sintered rare earth permanent magnet material according to the composition designed in Table 1.

[0129] The properties of the prepared sintered rare earth permanent magnet materials are shown in Table 2.

[0130] Table 1. Composition (%) of high energy product and low temperature coefficient sintered rare earth permanent magnet materials

[0131] Pr Nd Tb Co Cu Al Zr B Fe Example 1 6.75 20.25 3.5 20 0.2 0.1 0.2 0.96 margin Example 2 5.6 22.4 3 22 0.15 0.1 0.15 1.0 margin Example 3 6.5 19.5 4 25 0.1 0.1 0.15 0.98 margin Comparative Example 1 6.75 20.25 3.4 20 0.2 0.1 0.2 0.96 margin Comparative Example 2 6.75 20.25 3.5 15 0.2 0.1 0.2 0.96 margin Comparative Example 3 6.75 20.25 3.5 20 0 0.1 0 0.96 margin Comparative Example 4 6.75 20.25 3.5 20 0.2 0 0 0.96 margin Comparative Example 5 6.75 20.25 3.5 20 0 0 0 0.96 margin

[0132] Table 2. Performance of High Energy Product and Low Temperature Coefficient Sintered Rare Earth Permanent Magnet Materials

[0133] Br(kGs) Hcj(kOe) (BH)max α(RT~150℃) Example 1 13.10 19.87 41.04 -0.0686 Example 2 12.47 20.09 36.77 -0.068 Example 3 12.10 18.49 34.08 -0.068 Comparative Example 1 13.11 12.80 40.96 -0.069 Comparative Example 2 13.08 16.92 39.87 -0.072 Comparative Example 3 12.98 17.12 39.72 -0.069 Comparative Example 4 12.94 17.56 39.88 -0.069 Comparative Example 5 12.96 16.52 39.82 -0.069

[0134] As can be seen from Tables 1 and 2, the sintered rare earth permanent magnet materials in Examples 1 to 3 of the present invention have both high magnetic energy product and low temperature coefficient.

[0135] In Comparative Example 1, the lack of heavy rare earth grain boundary diffusion resulted in a significant reduction in coercivity; in Comparative Example 2, the Co content was reduced to 15%, leading to an increase in the absolute value of the remanence temperature coefficient; in Comparative Example 3, the absence of Cu and Zr resulted in an increase in the average grain size of the main phase and a slight decrease in coercivity; in Comparative Example 4, the absence of Al and Zr resulted in an increase in the average grain size of the main phase and a slight decrease in coercivity; in Comparative Example 5, the absence of Cu, Al, and Zr resulted in an increase in the average grain size of the main phase and a slight decrease in coercivity.

[0136] In summary, the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material of the present invention includes a main phase and a grain boundary phase. The grain boundary phase isolates and / or coats the main phase. The grain boundary phase is mainly a rare earth-rich phase, which includes a cobalt-poor phase and a cobalt-rich phase. The cobalt-rich phase accounts for more than 70% of the total mass of the grain boundary phase. The high cobalt content can ensure a low remanence temperature coefficient.

[0137] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A high-energy-product, low-temperature-coefficient sintered rare-earth permanent magnet material, characterized in that, The composition of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material includes, by weight percentage: LRE: 20~32%, HRE: 1~6%, Co: 19~25%, B: 0.9~1.2%, Cu: 0~1%, Al: 0~1%, Zr: 0~1%, with the balance being Fe; LRE is one or both of light rare earth elements Pr and Nd; HRE is one or more of the heavy rare earth elements Gd, Tb, Dy, and Ho; The high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material includes a main phase and a grain boundary phase, wherein the grain boundary phase isolates and / or coats the main phase. The main phase has a core-shell structure, which includes a core and a shell, with the shell located outside the main phase. In the region radiating inward from the surface of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material, the shell thickness of the main phase with a core-shell structure decreases as the distance from its surface increases. The shell composition of the main phase, by weight percentage, is: LRE f HRE g Co h B i Fe 1-f-g-h-i ; LRE is one or both of light rare earth elements Pr and Nd; HRE is one or more of the heavy rare earth elements Gd, Tb, Dy, and Ho; 15%≤f≤22%, 6%≤g≤9%, 19%≤h≤25%, 0.9%≤i≤1.2%, 50%≤1-fghi≤55%; The grain boundary phase includes a rare earth-rich phase and a very small amount of a boron-rich phase. The rare earth-rich phase includes an iron- and cobalt-poor rare earth-rich phase and a cobalt- and iron-rich rare earth-rich phase. The cobalt- and iron-rich rare earth-rich phase accounts for more than 70% of the total mass of the grain boundary phase.

2. A high-energy-product, low-temperature-coefficient sintered rare-earth permanent magnet material, characterized in that, The composition of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material includes, by weight percentage: LRE: 20~32%, HRE: 1~6%, Co: 19~25%, B: 0.9~1.2%, Cu: 0~1%, Al: 0~1%, Zr: 0~1%, with the balance being Fe; LRE is one or both of light rare earth elements Pr and Nd; HRE is one or more of the heavy rare earth elements Gd, Tb, Dy, and Ho; The high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material includes a main phase and a grain boundary phase, wherein the grain boundary phase isolates and / or coats the main phase. The main phase has a core-shell structure, which includes a core and a shell, with the shell located outside the main phase. In the region radiating inward from the surface of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material, the shell thickness of the main phase with a core-shell structure decreases as the distance from its surface increases. The core components of the main phase, by weight percentage, are: LRE k HRE m Co n B p Fe 1-k-m-n-p ; LRE is one or both of light rare earth elements Pr and Nd; HRE is one or more of the heavy rare earth elements Gd, Tb, Dy, and Ho; 18%≤k≤28%, 1%≤m≤5%, 19%≤n≤25%, 0.9%≤p≤1.2%, 50%≤1-kmnp≤55%; The grain boundary phase includes a rare earth-rich phase and a very small amount of a boron-rich phase. The rare earth-rich phase includes an iron- and cobalt-poor rare earth-rich phase and a cobalt- and iron-rich rare earth-rich phase. The cobalt- and iron-rich rare earth-rich phase accounts for more than 70% of the total mass of the grain boundary phase.

3. A high-energy-product, low-temperature-coefficient sintered rare-earth permanent magnet material, characterized in that, The composition of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material includes, by weight percentage: LRE: 20~32%, HRE: 1~6%, Co: 19~25%, B: 0.9~1.2%, Cu: 0~1%, Al: 0~1%, Zr: 0~1%, with the balance being Fe; LRE is one or both of light rare earth elements Pr and Nd; HRE is one or more of the heavy rare earth elements Gd, Tb, Dy, and Ho; The high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material includes a main phase and a grain boundary phase, wherein the grain boundary phase isolates and / or coats the main phase. The main phase has a core-shell structure, which includes a core and a shell, with the shell located outside the main phase. In the region radiating inward from the surface of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material, the shell thickness of the main phase with a core-shell structure decreases as the distance from its surface increases. The grain boundary phase includes a rare earth-rich phase and a very small amount of a boron-rich phase. The rare earth-rich phase includes an iron-poor and cobalt-poor rare earth-rich phase and a cobalt-rich, iron-rich, and rare earth-rich phase. The cobalt-rich, iron-rich, and rare earth-rich phase accounts for more than 70% of the total mass of the grain boundary phase. The composition of the iron- and cobalt-poor rare-earth-rich phase in the grain boundary phase, by weight percentage, is: LRE r HRE s Co t M u O v Fe 1-r-s-t-u-v ; LRE is one or both of light rare earth elements Pr and Nd; HRE is one or more of the heavy rare earth elements Gd, Tb, Dy, and Ho; M is one or more of Cu, Al, and Zr; 60%≤r≤85%, 0%≤s≤25%, 0%≤t≤14%, 0%≤u≤3%, 0%≤v≤1.3%, 2%≤1-rstuv≤10%.

4. A high-energy-product, low-temperature-coefficient sintered rare-earth permanent magnet material, characterized in that, The composition of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material includes, by weight percentage: LRE: 20~32%, HRE: 1~6%, Co: 19~25%, B: 0.9~1.2%, Cu: 0~1%, Al: 0~1%, Zr: 0~1%, with the balance being Fe; LRE is one or both of light rare earth elements Pr and Nd; HRE is one or more of the heavy rare earth elements Gd, Tb, Dy, and Ho; The high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material includes a main phase and a grain boundary phase, wherein the grain boundary phase isolates and / or coats the main phase. The main phase has a core-shell structure, which includes a core and a shell, with the shell located outside the main phase. In the region radiating inward from the surface of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material, the shell thickness of the main phase with a core-shell structure decreases as the distance from its surface increases. The grain boundary phase includes a rare earth-rich phase and a very small amount of a boron-rich phase. The rare earth-rich phase includes an iron-poor and cobalt-poor rare earth-rich phase and a cobalt-rich, iron-rich, and rare earth-rich phase. The cobalt-rich, iron-rich, and rare earth-rich phase accounts for more than 70% of the total mass of the grain boundary phase. The composition of the cobalt-rich, iron-rich, and rare-earth-rich phases in the grain boundary phase, by weight percentage, is: LRE w HRE x Co y M z Fe 1-w-x-y-z ; LRE is one or both of light rare earth elements Pr and Nd; HRE is one or more of the heavy rare earth elements Gd, Tb, Dy, and Ho; M is one or more of Cu, Al, and Zr; 40%≤w≤60%, 0%≤x≤8%, 22%≤y≤30%, 0%≤z≤3%, 20%≤1-wxyz≤30%.

5. The high magnetic energy product, low temperature coefficient sintered rare earth permanent magnet material according to claim 1, 2, 3, or 4, characterized in that, The composition of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material is 0.2%≤Cu+Al≤0.4% and 0.3%≤Cu+Al+Zr<0.6%.

6. The high magnetic energy product, low temperature coefficient sintered rare earth permanent magnet material according to claim 1, 2, 3, or 4, characterized in that, The main phase is a main phase grain with a RE:(Fe,Co):B = 2:14:1 structure, and RE includes light rare earth LRE and heavy rare earth HRE. The main phase accounts for 92-96% of the total mass of the sintered rare earth permanent magnet material; The mass of heavy rare earth elements in the shell of the main phase accounts for 0.01 to 2% of the total mass of the sintered rare earth permanent magnet material.

7. The high magnetic energy product, low temperature coefficient sintered rare earth permanent magnet material according to claim 1, 2, 3, or 4, characterized in that, The thickness of the sintered rare earth permanent magnet material is 1~10mm; the average size of the main phase is 1~10μm, and the shell thickness of the main phase is ≤6μm.

8. A method for preparing a high magnetic energy product, low temperature coefficient sintered rare earth permanent magnet material as described in 1, 2, 3, or 4, characterized in that, The preparation method includes: batching, smelting, coarse grinding, fine grinding, magnetic field forming, sintering, and grain boundary diffusion; after magnetic field forming, a green embryo is obtained, and after grain boundary diffusion, a high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material is obtained.

9. The preparation method according to claim 8, characterized in that, The density of the embryo is 7.6~7.8 g / cm³. 3 The density of the high magnetic energy product, low temperature coefficient sintered rare earth permanent magnet material is 7.7~8.0 g / cm³. 3 The Curie temperature is 500~600℃; the remanence temperature coefficient α of the high magnetic energy product and low temperature coefficient sintered rare earth permanent magnet material at 20~150℃ is -0.07~-0.01% / ℃.

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