A high-performance rare-earth permanent magnet material with low temperature coefficient and its preparation method

Abstract

This invention belongs to the field of rare earth permanent magnet materials technology, and discloses a high-performance, low-temperature-coefficient rare earth permanent magnet material and its preparation method. The material contains chemical formulas with the following weight percentages: (Pr...) i Nd j ) a L b Co c Cu d M e B f Fe 100‑a‑b‑c‑d‑e‑f R g X h Co 100‑g‑h Neodymium iron boron substrate and rare earth cobalt alloy, wherein 25≤a≤30, 0≤b≤5, 3≤c≤8, 0.1≤d≤0.4, 0

Description

Technical Field

[0001] This invention relates to the field of rare earth permanent magnet materials technology, specifically to a high-performance, low-temperature-coefficient rare earth permanent magnet material and its preparation method, and more specifically, to a high-remanence, low-temperature-coefficient, high-temperature-stability sintered NdFeB permanent magnet and its preparation method. Background Technology

[0002] Rare-earth permanent magnet materials are among the fastest-growing functional materials in recent years, widely used in new energy vehicles, energy-saving home appliances, energy-saving elevators, and next-generation mobile communications. Since the industrialization of neodymium iron boron magnets, research has mainly focused on improving the magnetic energy product and temperature stability. Significant success has been achieved in improving the magnetic energy product. The theoretical limit of the magnetic energy product is 64 MGOe, and in 2006, laboratory samples achieved 59.6 MGOe, while industrial products exceeded 55 MGOe. In recent years, with the rapid development of new energy vehicles and rail transit, more and more power motors are adopting rare-earth permanent magnet motor designs, which not only reduce weight but also improve motor efficiency. In major high-speed rail countries such as China, Germany, Japan, and France, permanent magnet synchronous drive systems have been applied to high-speed trains and subway cars, with most prototypes completed and tested on actual routes, and small-batch applications gradually underway in some cases. However, this type of power motor places higher demands on the temperature stability of the magnets. Currently, most rail transit traction motors use samarium cobalt magnets with low temperature coefficients in their design. However, samarium cobalt magnets are complex to manufacture, costly, fragile, and have low energy product. Therefore, high-performance, low-temperature-coefficient sintered neodymium iron boron magnets are one of the important research directions at present.

[0003] To reduce the temperature coefficient of NdFeB magnets (the reduction here refers to the absolute value of the temperature coefficient, the same below) and improve temperature stability, the following measures are generally taken: 1) M. Sagawa et al. added cobalt to replace iron to increase the Curie temperature. Matsuura, Mottram et al. found that replacing 1 at.% of iron with cobalt would increase the Curie temperature of NdFeB magnets by about 10.9℃; however, adding cobalt would reduce the intrinsic coercivity of the magnet, and NdFeB magnets with low intrinsic coercivity cannot be used at high operating temperatures. 2) Adding heavy rare earth elements such as Dy and Tb to increase intrinsic coercivity, but Dy and Tb do not significantly improve the remanence temperature coefficient, meaning that the magnetic properties of permanent magnets differ greatly at room temperature and high temperature, causing the torque of permanent magnet motors to decrease at high temperatures. Therefore, extremely high intrinsic coercivity cannot meet the requirements of rail transit for the temperature stability of permanent magnets. 3) Other existing technologies, such as patent CN111640549, address the problems of low operating temperature and poor temperature stability of sintered NdFeB magnets by jointly adding heavy rare earth elements, cobalt, and trace elements to effectively control the magnetic moment and microstructure of the material. This optimizes the structure of the grain boundary phase and grain boundary of the sintered rare earth permanent magnet material, forming a cobalt-containing amorphous grain boundary phase. This results in sintered rare earth permanent magnet materials with high temperature stability. However, the amount of heavy rare earth and cobalt used is relatively high, resulting in lower magnetic properties and a remanence of approximately 11.9–12.69 kGs. Moreover, the cost is relatively high. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the above-mentioned background technology and provide a high-performance, low-temperature-coefficient rare-earth permanent magnet material and its preparation method. The rare-earth permanent magnet material is obtained from a specific composition neodymium iron boron substrate grain boundary diffused rare-earth cobalt alloy. The content of heavy rare earth and cobalt in the grain boundary phase is higher than that in the main phase, and the content of heavy rare earth and cobalt in the surface layer is higher than that in the magnet body, thus exhibiting excellent high-temperature stability.

[0005] To achieve the objectives of this invention, the high-performance, low-temperature-coefficient rare-earth permanent magnet material of this invention comprises a neodymium iron boron substrate and a rare-earth cobalt alloy, wherein the general chemical formula of the neodymium iron boron substrate is (Pr) by weight percentage. i Nd j ) a L b Co c Cu d M e B f Fe 100-a-b-c-d-e-f, where 25 ≤ a ≤ 30, 0 ≤ b ≤ 5, 3 ≤ c ≤ 8, 0.1 ≤ d ≤ 0.4, 0 < e ≤ 3, 0.9 ≤ f ≤ 1, i:j = 23 - 28:72 - 77; L is a rare earth element other than Pr and Nd; M is a combination of two or more of Al, Cr, Nb, Zr, Ga, Ti, Mn, Zn, V, and Mo; the general chemical formula of the rare earth cobalt alloy is by weight percentage R g X h Co 100-g-h , where R is one or both of Dy and Tb, 10 ≤ g ≤ 90; X is one or a combination of two or more of Cu, Al, Cr, Nb, Zr, Ga, Ti, Mn, Zn, V, Mo, and rare earth elements other than Dy and Tb, 0 < h ≤ 20.

[0006] Further, in some embodiments of the present invention, when b is 0, the rare earth cobalt alloy R g X h Co 100-g-h contains Dy.

[0007] Further, in some embodiments of the present invention, the maximum operating temperature of the high-performance low temperature coefficient rare earth permanent magnet material is greater than 200 °C.

[0008] Further, in some embodiments of the present invention, the high-performance low temperature coefficient rare earth permanent magnet material is prepared by the process steps of melting, hydrogen crushing, jet milling, magnetic field orientation forming, sintering, machining, and diffusion.

[0009] On the other hand, the present invention also provides a preparation method of the aforementioned high-performance low temperature coefficient rare earth permanent magnet material, and the method includes the following steps:

[0010] (1) Raw material preparation: The neodymium iron boron base alloy (alloy 1) is in accordance with the general chemical formula by weight percentage as (Pr i Nd j ) a L b Co c Cu d M e B f Fe 100-a-b-c-d-e-f , where 25 ≤ a ≤ 30, 0 ≤ b ≤ 5, 3 ≤ c ≤ 8, 0.1 ≤ d ≤ 0.4, 0 < e ≤ 3, 0.9 ≤ f ≤ 1, i:j = 23 - 28:72 - 77; L is a rare earth element other than Pr and Nd; M is a combination of two or more of Al, Cr, Nb, Zr, Ga, Ti, Mn, Zn, V, and Mo;

[0011] The rare earth cobalt alloy (alloy 2) is in accordance with the general chemical formula by weight percentage as R g Xh Co 100-g-h Prepare the raw materials, wherein R is one or two of Dy and Tb, 10≤g≤90; X is one or more of Cu, Al, Cr, Nb, Zr, Ga, Ti, Mn, Zn, V, Mo, and rare earth elements other than Dy and Tb, 0<h≤20.

[0012] (2) Preparation of quick-setting sheets: Neodymium iron boron base alloy and rare earth cobalt alloy are placed in the crucible of quick-setting furnace and vacuum induction melting is carried out under inert gas protection. After the raw materials are fully melted, the alloy liquid is poured onto water-cooled rotating copper roller to obtain quick-setting sheet 1 and quick-setting sheet 2.

[0013] (3) Hydrogen crushing: The quick-setting flakes 1 and 2 are crushed in a hydrogen crushing furnace to obtain millimeter-sized hydrogen crushing medium powder 1 and hydrogen crushing medium powder 2.

[0014] (4) Airflow mill: Under nitrogen protection, hydrogen-crushed medium powder 1 and hydrogen-crushed medium powder 2 are ground into fine powder 1 and fine powder 2 respectively;

[0015] (5) Pressing: Fine powder 1 is oriented and pressed into shape in a magnetic field press of 1.5T or above to obtain NdFeB blank, and then isostatic pressing is performed to obtain green blank;

[0016] (6) Sintering: Sinter the green body obtained by pressing;

[0017] (7) Machining: Machining the blank into a magnet that is close to the specifications and dimensions of the product;

[0018] (8) Diffusion: Fine powder 2 is coated on the surface of the magnet, and then placed in a vacuum furnace for diffusion treatment, followed by tempering treatment to obtain sintered NdFeB magnet.

[0019] Furthermore, in some embodiments of the present invention, when b is 0, the rare earth cobalt alloy R g X h Co 100-g-h It contains Dy.

[0020] Furthermore, in some embodiments of the present invention, in step (2), after the raw materials are fully melted, the temperature is maintained at 1350-1550°C, and then the alloy liquid is poured onto the water-cooled rotating copper roller.

[0021] Furthermore, in some embodiments of the present invention, the average thickness of the quick-setting sheet 1 and quick-setting sheet 2 in step (2) is 0.2 to 0.4 mm.

[0022] Furthermore, in some embodiments of the present invention, the average particle size of fine powder 1 and fine powder 2 in step (3) is 2 to 4 μm.

[0023] Furthermore, in some embodiments of the present invention, the density of the green body in step (5) is 3.8–5 g / cm³. 3 .

[0024] Furthermore, in some embodiments of the present invention, the sintering in step (6) is carried out under vacuum conditions, the sintering temperature is 1040-1100℃, and the sintering time is 5-10h.

[0025] Furthermore, in some embodiments of the present invention, a machining allowance of 0.05 to 0.5 mm is reserved in the orientation direction during step (7).

[0026] Furthermore, in some embodiments of the present invention, the coating weight in step (8) is 0.1% to 2% of the magnet weight.

[0027] Furthermore, in some embodiments of the present invention, in step (9), diffusion treatment is carried out in a vacuum furnace at 800-950°C for 1-48 hours.

[0028] Furthermore, in some embodiments of the present invention, in step (9), tempering is performed at 400–650°C for 2–10 hours.

[0029] Compared with the prior art, the advantages of the present invention are as follows:

[0030] (1) The high-performance, low-temperature-coefficient sintered rare-earth permanent magnet material of the present invention is a NdFeB magnet with a (DyTb)-(CoFe)-B shell structure obtained by using a NdFeB substrate with a specific composition through grain boundary diffusion of rare-earth cobalt alloy. This magnet has the characteristics of high performance and low temperature coefficient.

[0031] (2) The remanence of the high-performance low temperature coefficient sintered rare earth permanent magnet material of the present invention is Br≥13kGs, Hcj≥20kOe; the absolute value of the temperature coefficient at 20~200℃ is ≤0.1% / ℃, and the absolute value of the intrinsic coercivity temperature coefficient at 20~200℃ is ≤0.5% / ℃. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. It should be understood that the following description is merely illustrative and not intended to limit the invention.

[0033] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0034] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0035] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including the ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0036] The singular form includes the plural objects of discussion unless the context clearly indicates otherwise. "Optional" or "any one" means that the matter or event described thereafter may or may not occur, and the description includes both the possibility that the event occurs and the possibility that the event does not occur.

[0037] Approximate terms used in the specification and claims to modify quantities indicate that the invention is not limited to that specific quantity, but also includes acceptable modifications close to that quantity that do not alter the relevant essential function. Correspondingly, the use of "about," "approximately," etc., to modify a numerical value means that the invention is not limited to that precise value. In some instances, approximate terms may correspond to the precision of the instrument used to measure the value. In this application's specification and claims, scope definitions can be combined and / or interchanged, unless otherwise stated, these scopes include all subscopes contained therein.

[0038] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0039] Furthermore, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., described below refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms are not necessarily directed at the same embodiment or example. Moreover, the technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0040] Unless otherwise specified, the rapid solidification process in the embodiments and comparative examples of this invention is as follows: the alloy is placed in the crucible of the rapid solidification furnace and vacuum induction melting is carried out under argon protection. After the raw materials are fully melted, the temperature is maintained at 1350-1550°C, and the alloy liquid is poured onto a water-cooled rotating copper roller to obtain a rapid solidification sheet with an average thickness of 0.2-0.4 mm.

[0041] The hydrogen-crushing process involves crushing the quick-setting flakes in a hydrogen-crushing furnace to obtain millimeter-sized hydrogen-crushed powder.

[0042] The air jet milling process involves grinding hydrogen-fired medium powder into fine powder with an average particle size of 2–4 μm under nitrogen protection.

[0043] The molding process is as follows: fine powder is oriented and pressed into shape in a magnetic field press of 1.5T or higher to obtain NdFeB blanks, and then isostatic pressing is performed to obtain a density of 3.8-5 g / cm³. 3 The raw clay.

[0044] The sintering process is as follows: the green body obtained by pressing is sintered under vacuum conditions at a temperature of 1040-1100℃ for 5-10 hours.

[0045] As long as the above process parameters are followed, the required qualified product can be obtained. For example, in the rapid solidification process, after the raw materials are fully melted, the temperature range of 1350 to 1550°C can be maintained. There are no special requirements for the specific temperature. The thickness of the rapid solidification sheet can be 0.2 to 0.4 mm, which will not affect the quality of the product obtained by subsequent processes.

[0046] Example 1

[0047] High-performance, low-temperature-coefficient rare-earth permanent magnet materials are prepared using the following material selection and methods:

[0048] (1) The weight percentage of the neodymium iron boron substrate alloy 1 is (Pr 25 Nd 75 ) 29 Dy 0.5 Co5Cu 0.2 Al 0.2 Zr 0.1 B 0.98 Fe 64.02 Neodymium iron boron blanks were prepared by rapid solidification, hydrogen rupture, air jet milling, molding, and sintering processes.

[0049] (2) Alloy 2 has a weight percentage of Tb 60 Cu5Co 35 Fine powder A was obtained by rapid coagulation, hydrogen pulverization, and air jet milling.

[0050] (3) The neodymium iron boron blank is processed into a square piece of 20mm×20mm×5mm;

[0051] (4) Diffusion: Fine powder A is applied to the surface of the square piece. The amount of fine powder A applied is 0.8% of the weight of the magnet. Diffusion is carried out at 900℃ for 20 hours and tempered at 510℃ for 4 hours.

[0052] Comparative Example 1

[0053] The difference from Example 1 is that fine powder A was not applied and diffusion treatment was not performed; otherwise, it is the same as Example 1.

[0054] Comparative Example 2

[0055] The difference from Example 1 is that the NdFeB substrate alloy 1 has a weight percentage of (Pr 25 Nd 75 ) 29 Dy 0.5 Tb 0.48 Co 5.28 Cu 0.2 Al 0.2 Zr 0.1 B 0.98 Fe 63.26 The fine powder A was not coated, and no diffusion treatment was performed; otherwise, it was the same as in Example 1.

[0056] Comparative Example 3

[0057] The difference from Example 1 is that 0.48% pure Tb was applied, while the rest were the same as in Example 1.

[0058] Comparative Example 4

[0059] The difference from Example 1 is that the NdFeB substrate alloy 1 has a weight percentage of (Pr 25 Nd 75 ) 29 Dy 0.5Tb 0. 5Co 10 Cu 0.2 Al 0.2 Zr 0.1 B 0.98 Fe 58.52 Diffused fine powder A, otherwise the same as in Example 1; Comparative Example 5

[0060] The difference from Example 1 is that the NdFeB substrate alloy 1 has a weight percentage of (Pr 25 Nd 75 ) 26 Dy6Tb 0.5 Co5Cu 0.2 Al 0.2 Zr 0.1 B 0.98 Fe 61.02 Diffused fine powder A, otherwise the same as in Example 1;

[0061] Example 2

[0062] High-performance, low-temperature-coefficient rare-earth permanent magnet materials are prepared using the following material selection and methods:

[0063] (1) Alloy 1 has a weight percentage of (Pr) 25 Nd 75 ) 29.5 Co8Cu 0.2 Al 0.2 Zr 0.1 B 0.98 Fe 61.02 Neodymium iron boron blanks were prepared by rapid solidification, hydrogen rupture, air jet milling, molding, and sintering processes.

[0064] (2) Alloy 2 has a weight percentage of Dy 70 Cu8Co 22 Fine powder B is obtained by rapid coagulation, hydrogen pulverization, and air jet milling;

[0065] (3) The neodymium iron boron blank is processed into a square piece of 20mm×20mm×5mm;

[0066] (4) Diffusion: Fine powder B is applied to the surface of the square piece. The amount of fine powder B applied is 1.2% of the weight of the magnet. Diffusion is carried out at 900℃ for 30 hours and tempered at 510℃ for 4 hours.

[0067] The magnetic properties of the sintered rare earth permanent magnet materials obtained in the above embodiments and comparative examples are shown in Table 1.

[0068] Table 1 Comparison of magnetic properties of materials obtained from the examples and comparative examples.

[0069]

[0070] As shown in Table 1, the material obtained in Example 1 has excellent comprehensive magnetic properties, with a remanence of over 14 kGs, a temperature coefficient of less than 0.1% / ℃, and an intrinsic coercivity of over 7 kOe at 200℃. It can be determined that the magnet is a high-performance sintered NdFeB magnet with low temperature coefficient and high stability that can be used at 200℃.

[0071] Comparative Example 1, where the substrate of Example 1 was not coated with diffusion treatment, showed that the intrinsic coercivity and temperature coefficient of the magnet were significantly inferior to those of Example 1. Comparative Example 2 also did not undergo coating with diffusion treatment; instead, the alloying elements that would otherwise be diffused into the magnet were added to the magnet during the smelting process. The final magnet composition was similar to that of Example 1, but the temperature coefficient and high-temperature stability differed considerably. Comparative Example 3 used a pure terbium diffusion scheme, resulting in a lower temperature coefficient than Example 1. Comparative Example 4 showed that a higher cobalt content in the magnet reduced its intrinsic coercivity, which could not meet the high operating temperature requirements and increased costs. Comparative Example 5 showed that a higher heavy rare earth content improved the intrinsic coercivity of the magnet, but significantly reduced its remanence, leading to a substantial increase in cost, and did not significantly improve the high-temperature stability of the magnet. Example 2 demonstrated that diffused dysprosium alloys are a good choice for applications requiring lower operating temperatures, as they can reduce costs.

[0072] The above comparison reveals that while cobalt can reduce the remanence temperature coefficient of magnets, higher is not always better. A reduction exceeding 8% excessively lowers the intrinsic coercivity of the magnet, requiring more heavy rare earth elements to compensate for this reduction, increasing costs, further decreasing remanence, and without significantly improving high-temperature stability. Compared to traditional diffusion techniques, grain boundary diffusion cobalt alloys exhibit better diffusion effects. This technology forms a (DyTb)-(CoFe)-B shell structure at the magnet's grain boundaries, grain surfaces, and surface, resulting in high-performance, low-temperature-coefficient rare earth permanent magnet materials with excellent high-temperature stability. Therefore, obtaining high-performance sintered NdFeB magnets with low temperature coefficients and high temperature stability using lower amounts of heavy rare earth elements and cobalt, and improving the utilization efficiency of cobalt and heavy rare earth elements, holds broad application prospects.

[0073] Those skilled in the art will readily understand that the above description is merely an embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-performance, low-temperature-coefficient rare-earth permanent magnet material, characterized in that, The high-performance low-temperature coefficient rare earth permanent magnet material comprises a neodymium-iron-boron base material and a rare earth cobalt alloy. Among them, the general formula of the chemical formula of the neodymium-iron-boron base material is by weight percentage (Pr i Nd j ) a L b Co c Cu d M e B f Fe 100-a-b-c-d-e-f , where 25 ≤ a ≤ 30, 0 ≤ b ≤ 5, 3 ≤ c ≤ 8, 0.1 ≤ d ≤ 0.4, 0 < e ≤ 3, 0.9 ≤ f ≤ 1, i:j = 23 - 28:72 - 77; L is a rare earth element other than Pr and Nd; M is a combination of two or more of Al, Cr, Nb, Zr, Ga, Ti, Mn, Zn, V, Mo; the general formula of the chemical formula of the rare earth cobalt alloy is by weight percentage R g X h Co 100-g-h , where R is one or both of Dy and Tb, 60 ≤ g ≤70; X is a combination of one or two or more of Cu, Al, Cr, Nb, Zr, Ga, Ti, Mn, Zn, V, Mo, and rare earth elements other than Dy and Tb, 0 < h ≤ 20; where 22 ≤ 100 - g - h ≤ 35; The above-mentioned method for preparing high-performance, low-temperature-coefficient rare-earth permanent magnet materials includes the following steps: (1) Raw material preparation: The neodymium-iron-boron base alloy has a general chemical formula weight percentage of (Pr i Nd j ) a L b Co c Cu d M e B f Fe 100-a-b-c-d-e-f , where 25 ≤ a ≤ 30, 0 ≤ b ≤ 5, 3 ≤ c ≤ 8, 0.1 ≤ d ≤ 0.4, 0 < e ≤ 3, 0.9 ≤ f ≤ 1, i:j = 23 - 28:72 - 77; L is a rare earth element other than Pr and Nd; M is a combination of two or more of Al, Cr, Nb, Zr, Ga, Ti, Mn, Zn, V, Mo; Rare earth cobalt alloys are expressed as R by weight percentage according to the general chemical formula. g X h Co 100-g-h The raw materials are prepared, wherein R is one or both of Dy and Tb, 60≤g≤70; X is one or more of Cu, Al, Cr, Nb, Zr, Ga, Ti, Mn, Zn, V, Mo, and rare earth elements other than Dy and Tb, 0<h≤20; wherein 22≤100-gh≤35; (2) Preparation of quick-setting sheets: Neodymium iron boron base alloy and rare earth cobalt alloy are placed in the crucible of quick-setting furnace and vacuum induction melting is carried out under inert gas protection. After the raw materials are fully melted, the alloy liquid is poured onto water-cooled rotating copper roller to obtain quick-setting sheet 1 and quick-setting sheet 2. (3) Hydrogen crushing: quick-setting flakes 1 and quick-setting flakes 2 are crushed in a hydrogen crushing furnace to obtain millimeter-sized hydrogen crushing medium powder 1 and hydrogen crushing medium powder 2. (4) Airflow mill: Under nitrogen protection, hydrogen-crushed medium powder 1 and hydrogen-crushed medium powder 2 are ground into fine powder 1 and fine powder 2 respectively; (5) Pressing: Fine powder 1 is oriented and pressed into shape in a magnetic field press of 1.5T or above to obtain NdFeB blank, and then isostatic pressing is performed to obtain green blank; (6) Sintering: The green body obtained by pressing is sintered; (7) Machining: Machining the blank into a magnet that is close to the specifications and dimensions of the product; (8) Diffusion: Fine powder 2 is coated on the surface of the magnet and then placed in a vacuum furnace for diffusion treatment. After that, tempering treatment is performed to obtain sintered NdFeB magnet.

2. The high-performance, low-temperature-coefficient rare-earth permanent magnet material according to claim 1, characterized in that, When b is 0, the rare earth cobalt alloy R g X h Co 100-g-h It contains Dy.

3. The high-performance, low-temperature-coefficient rare-earth permanent magnet material according to claim 1, characterized in that, The maximum operating temperature of the high-performance, low-temperature-coefficient rare-earth permanent magnet material is greater than 200℃.

4. The high-performance, low-temperature-coefficient rare-earth permanent magnet material according to claim 1, characterized in that, In step (2), after the raw materials have been fully melted, the temperature is maintained at 1350-1550℃, and then the alloy liquid is poured onto the water-cooled rotating copper roller.

5. The high-performance, low-temperature-coefficient rare-earth permanent magnet material according to claim 1, characterized in that, In step (2), the average thickness of quick-setting sheet 1 and quick-setting sheet 2 is 0.2 to 0.4 mm.

6. The high-performance, low-temperature-coefficient rare-earth permanent magnet material according to claim 1, characterized in that, In step (3), the average particle size of fine powder 1 and fine powder 2 is 2-4 μm.

7. The high-performance, low-temperature-coefficient rare-earth permanent magnet material according to claim 1, characterized in that, The density of the green body in step (5) is 3.8–5 g / cm³. 3 .

8. The high-performance, low-temperature-coefficient rare-earth permanent magnet material according to claim 1, characterized in that, In step (6), sintering is carried out under vacuum conditions, with a sintering temperature of 1040-1100℃ and a sintering time of 5-10h.

9. The high-performance, low-temperature-coefficient rare-earth permanent magnet material according to claim 1, characterized in that, In step (7), a machining allowance of 0.05~0.5mm is reserved in the orientation direction.

10. The high-performance, low-temperature-coefficient rare-earth permanent magnet material according to claim 1, characterized in that, In step (8), the coating weight is 0.1~2% of the magnet's weight.

11. The high-performance, low-temperature-coefficient rare-earth permanent magnet material according to claim 1, characterized in that, In step (9), diffusion treatment is carried out in a vacuum furnace at 800-950°C for 1-48 hours.

12. The high-performance, low-temperature-coefficient rare-earth permanent magnet material according to claim 1, characterized in that, In step (9), tempering is performed at 400-650°C for 2-10 hours.

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