A high-temperature resistant samarium cobalt permanent magnet and a preparation method thereof

Abstract

The present invention discloses a high-temperature resistant samarium cobalt permanent magnet and a preparation method thereof. The composition of the magnet is expressed by weight percentage as: Sm u Gd v Co w Cu a Zr b Ti c Fe d , where u = 19.4% - 23.92%, v = 1.41% - 3.76%, w = 34.44% - 51.28%, a = 5.3% - 11.32%, b = 2.91% - 4.6%, c = 0.3% - 0.8%, and d = the balance; the alloy is prepared through steps of alloy melting and casting into flakes, hydrogen crushing, air-flow milling for powder making, orientation forming, isostatic pressing, sintering, solution treatment and aging treatment. The method is simple and the process is easy to control. The prepared high-temperature resistant samarium cobalt permanent magnet has magnetic properties at 550 °C: Hcj ≥ 7.5 kOe, (BH)max ≥ 9 MGOe, solving the problems that the magnetic properties of existing samarium cobalt magnets drop sharply at temperatures above 350 °C and their application range is limited.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic materials, and relates to a high-temperature resistant samarium cobalt permanent magnet and a preparation method thereof. Background Art

[0002] Due to its good magnetic properties, high temperature resistance and temperature stability, samarium cobalt permanent magnets have been widely used and play a very important role in many fields such as military, aerospace, rail transit and instrumentation. Samarium cobalt magnets are the second generation of rare earth permanent magnets, mainly divided into two types: 1:5 type and 2:17 type. The main characteristics of samarium cobalt permanent magnets are high magnetic properties and good temperature properties, and the highest working temperature can reach 250 - 350 °C. However, after the use temperature of samarium cobalt permanent magnets exceeds 350 °C, their coercivity will drop sharply, with a higher negative temperature coefficient and become unstable. Once the use temperature exceeds 670 °C, it will even be completely demagnetized, unable to meet the requirements of some high-temperature application scenarios, such as aerospace, national defense and military industry, and cutting-edge science and technology and other fields, all require permanent magnets to work continuously and stably in a high-temperature environment (above 400 °C). However, for high-temperature resistant permanent magnetic materials, stable magnetic field stability is the most important indicator to measure high-temperature resistant permanent magnetic materials. Therefore, the research and development of high-temperature resistant permanent magnets has become one of the research hotspots.

[0003] At present, researchers have tried to improve the temperature coefficient by introducing rare earth auxiliary alloys, such as adding a certain amount of heavy rare earth elements such as Er, Dy, Ho, Gd, Sm, etc. as temperature compensation to improve the high-temperature stability of samarium cobalt magnets. However, this method will reduce the saturation magnetization intensity of the magnet, thereby leading to a decrease in the maximum magnetic energy product of the magnet. At the same time, since rare earth Sm is an easily volatile element, the magnetic properties of the magnet will be affected by the volatilization of Sm during high-temperature service. In addition, the long-term service of samarium cobalt magnets at high temperatures will also cause their magnetic properties to degrade due to oxidation, greatly reducing their service life and limiting the further application of samarium cobalt magnets.

[0004] Therefore, it is of great significance to develop high-temperature resistant samarium cobalt permanent magnets with stable magnetic properties through reasonable design of alloy composition and regulation of microstructure. Summary of the Invention

[0005] The present invention aims to provide a high-temperature resistant samarium cobalt permanent magnet and a preparation method thereof. The composition is expressed by weight percentage as: Sm u Gd v Co w Cu a Zr b Ti c Fe d, where u = 19.4% - 23.92%, v = 1.41% - 3.76%, w = 34.44% - 51.28%, a = 5.3% - 11.32%, b = 2.91% - 4.6%, c = 0.3% - 0.8%, and d = the balance; this alloy is prepared through the steps of alloy melting and casting into sheets, hydrogen crushing, airflow milling into powder, orientation forming, isostatic pressing, sintering, solution treatment, and aging treatment. The method is simple, the process is easy to control, and the prepared high-temperature-resistant samarium cobalt permanent magnet has magnetic properties at 550 °C: Hcj ≥ 7.5 kOe, (BH)max ≥ 9 MGOe.

[0006] The technical solution of the present invention is as follows:

[0007] A high-temperature-resistant samarium cobalt permanent magnet, the composition of which is expressed by weight percentage as: Sm u Gd v Co w Cu a Zr b Ti c Fe d , where u = 19.4% - 23.92%, v = 1.41% - 3.76%, w = 34.44% - 51.28%, a = 5.3% - 11.32%, b = 2.91% - 4.6%, c = 0.3% - 0.8%, and d = the balance.

[0008] The present invention also provides a preparation method for a high-temperature-resistant samarium cobalt permanent magnet, which is prepared in the following order of steps:

[0009] (1) Alloy melting and casting into sheets

[0010] The first cast sheet and the second cast sheet are respectively prepared by rapid solidification melting and casting. The composition of the first cast sheet is expressed by weight percentage as Sm f Co g Cu h Zr i Fe k , where f = 20% - 26%, g = 35% - 52%, h = 5% - 11%, i = 3% - 5%, k = the balance, and the weight percentage of the composition of the second cast sheet is Gd 47 Co 28 Ti 10 Cu 15 ;

[0011] (2) Coarse crushing

[0012] The first cast sheet and the second cast sheet are respectively hydrogen crushed to obtain the first coarse powder and the second coarse powder;

[0013] (3) Airflow milling into powder

[0014] An antioxidant is added to a coarse powder and a second coarse powder respectively, and after stirring for 30 to 60 minutes, jet milling is carried out under a grinding pressure of 0.5 to 0.6 MPa to obtain a first fine powder and a second fine powder with a D50 of 4 to 6 μm respectively; the second fine powder and the first fine powder are mixed to form a mixed fine powder, and then a lubricant is added and stirred for 1.5 to 4 hours to obtain a uniform samarium-cobalt double alloy fine powder;

[0015] In this step, the particle size of the powder mainly affects the grain size of the sintered magnet, and thus affects the magnetic properties of the magnet. When the particle size of the mixed fine powder is greater than 6 μm, after sintering, the grains of the magnet are relatively large, which will reduce the Hcj of the magnet. When the particle size of the mixed fine powder is less than 4 μm, after high-temperature sintering, the grains of the magnet grow abnormally, resulting in an overall low comprehensive performance of Br, Hcj, and Hk / Hcj of the magnet;

[0016] (4) Orientation forming and cold isostatic pressing

[0017] The samarium-cobalt double alloy fine powder is taken for pressing and orientation forming, and then it is cold isostatically pressed under a pressure of 180 to 220 MPa for 10 to 30 s to obtain a green compact with a density of 6.0 to 6.8 g / cm 3 of the green compact;

[0018] In this step, the density of the green compact is crucial and affects the density of the magnet. When the density is less than 6.0 g / cm 3 , the density of the magnet is relatively low. After isostatic pressing, the corners of the magnet are chipped, and there are a large number of holes in the internal structure of the sintered product, which is not dense and will reduce the Hcj and Hk / Hcj of the magnet. When the density is greater than 6.8 g / cm 3 , it will lead to a low orientation degree of the magnet, thereby reducing the Br of the magnet;

[0019] (5) Sintering and solution treatment

[0020] The green compact is heated to 1180 - 1230 °C and held for 2 - 4 h, then cooled to 1160 - 1200 °C and held for 3 - 5 h for solution treatment, and then quickly air-cooled to room temperature;

[0021] In this process, after solution treatment, the Gd element in the master alloy diffuses into the main alloy to form (SmGd) 2 (Co, Fe) 17 intracellular phase.

[0022] (6) Aging treatment

[0023] The product of step (5) is subjected to aging treatment to obtain a samarium-cobalt permanent magnet.

[0024] As a limitation of the present invention:

[0025] (1) In step (1), the casting temperature of the first cast sheet is 1380 - 1480 °C, and the thickness is 0.15 - 0.45 mm. The casting temperature of the first cast sheet affects the composition, microstructure, and grain size of the master alloy. The thickness consistency of the cast sheet affects the particle size of the master alloy powder and the grain size of the final product.

[0026] The casting temperature of the second cast sheet is 1360 - 1470 °C, and the thickness is 0.1 - 0.35 mm.

[0027] (2) In step (3), the addition amount of the second fine powder accounts for 3 - 8% of the total weight of the two fine powders.

[0028] The addition amounts of the first fine powder and the second fine powder affect the composition and structure of the magnet, and thus affect the comprehensive magnetic properties of the magnet such as Br and Hcj in the end.

[0029] (3) In step (4), the orientation magnetic field is 1.8 - 2.2 T, and the molding pressure is 3 - 5 MPa.

[0030] (4) In step (6), the aging treatment is divided into three stages. The first-stage aging treatment is carried out at 810 °C for 15 h, followed by the first temperature drop; the second-stage aging treatment is carried out at 630 °C for 8 h, followed by the second temperature drop; the third-stage aging treatment is carried out at 400 °C for 3 h, and then the samarium-cobalt permanent magnet is obtained after the third temperature drop.

[0031] The elemental composition of the alloy is closely related to the aging treatment process. Different alloy elemental compositions and their contents have different sensitivities to the aging time during different aging treatment processes. That is, the number of plate-like phases formed by alloys with different compositional elements during the aging treatment process is different, and the formation of plate-like phases affects the progress of the aging process. Therefore, the aging treatment for different alloy compositions is different, which is related to the formation, growth, and element migration and distribution of cell wall phases and plate-like phases. Aging treatment has an important impact on the magnetic properties (coercivity, magnetic energy product, etc.) of magnets. Aging treatment mainly conducts microstructure and composition phase transformation on the sintered green body. The aging treatment process affects the levels of Hcj and Hk / Hcj. Specifically, in the first-stage aging treatment, the temperature is high and the holding time is long. During this process, the formation, distribution, and growth of phases such as cell wall phases and plate-like phases can occur in the high-temperature environment. The plate-like phases generated at this time provide a path for the element migration during low-temperature aging and accelerate the progress of the aging process. The size of the cellular structure and the distribution of each element in each phase are the key factors determining the coercivity. In the second-stage aging treatment, the temperature is lower than that of the first-stage aging treatment, and the holding time is shorter than that of the first-stage aging. During this process, the composition and structure of the cell wall phase and plate-like phase are further optimized to promote the integrity of their tissue morphology (shape, size, and integrity) and element migration. The third-stage aging treatment refines the grains, further promotes the migration and diffusion of elements, forms occupancy, and thus improves the overall performance of the magnet.

[0032] During the aging process, the aging temperature and time are crucial, directly affecting the formation, growth, and integrity of phases, and ultimately affecting the performance of the magnet. If the aging time is short, the coercivity will decrease. However, when the aging time is extended, the coercivity will gradually increase until it reaches a peak. However, when the aging time is further extended, the cellular structure of the alloy will be damaged, a few remaining complete cells will grow, and coarse plate-like structures will be formed, and the coercivity and magnetic energy product will gradually decrease.

[0033] (5) In step (3), the addition amount of the antioxidant in the first coarse powder or the second medium coarse powder is 0.5 to 1‰ of the mass of the first coarse powder or the second coarse powder, and the antioxidant is an ester; the addition amount of the lubricant is 0.5 to 0.8‰ of the mass of the mixed fine powder, and the lubricant is an alkane.

[0034] As a further limitation of the present invention, the cooling rates of the first cooling and the second cooling are 0.2 to 0.6 °C / min, and the third cooling is to cool to 20 to 30 °C by air cooling with argon filling.

[0035] During the multi-stage aging process, the cooling rate during cooling affects the internal structural state of the alloy, thereby affecting the change in the magnetic properties of the alloy. An appropriate cooling rate enables the magnetic properties of the alloy to reach a better level. During the first aging treatment of the alloy, a cellular microstructure has already formed. During the cooling process, as the temperature decreases, the solubility of each element in the various phase products formed by the first-stage aging of the alloy will change, which is necessary for the redistribution of components between the matrix and the decomposition products, and this will cause differences in the magnetic properties of the decomposition products. The cooling rate of the present invention is conducive to the continuous migration of each atom and thus conducive to the improvement of magnetic properties.

[0036] The present invention mainly adopts a dual-alloy process and introduces high-melting-point Gd 47 Co 28 Ti 10 Cu 15 rare earth auxiliary alloy. By forming a high Curie temperature SmGd 2 (Co, Fe) 17 rhombohedral cellular structure and SmGd(CoTiCu) 5 cell wall phase, the regulation of the composition of the final samarium-cobalt permanent magnet, the improvement of the high-temperature resistance performance and the improvement of the magnetic properties are realized, and it has good high-temperature stability. In the alloy of the present invention, Gd and Co elements enable the alloy to form a samarium-gadolinium intracellular phase SmGd 2 (Co, Fe) 17 , which increases the Curie temperature of the samarium-cobalt magnet and optimizes the temperature coefficient of the magnet at high temperatures. At the same time, the addition of high-melting-point Ti elements plays a pinning role in the growth of the intracellular phase, constructs a fine-grained region within a certain range, and Ti elements can well compensate for the intracellular defects caused by Fe elements, so that the room-temperature coercivity and magnetic energy product of the magnet are improved, thereby improving the coercivity and magnetic energy product of the magnet at variable temperatures. The addition of Cu elements at the grain boundaries forms SmGd(CoTiCu) 5 alloy phase is distributed in the cell wall phase of the magnet, continuously and uniformly distributed on the grain boundaries, optimizes the grain boundary microstructure, improves the room-temperature coercivity of the samarium-cobalt magnet, and at the same time improves the squareness and Curie temperature of the samarium-cobalt magnet, so as to optimize the high-temperature use performance of the magnet.

[0037] As a whole, the above preparation method of the present invention is an organic whole among each step, closely related and inseparable. Through the overall preparation process of the present invention, the temperature stability of the prepared magnet can be enhanced.

[0038] After adopting the technical solution of the present invention, the beneficial effects obtained by the present invention are as follows:

[0039] 1. For the samarium-cobalt magnet prepared by the present invention, by adopting a dual-alloy process and introducing high-melting-point Gd 47 Co 28 Ti10 Cu 15 The rare earth auxiliary alloy powder, adopting the main-auxiliary double alloy process, can reduce the remanence of the magnet less while optimizing the cell wall phase distribution and greatly improving the coercivity. By introducing Ti, Cu, and Gd elements simultaneously, not only a samarium-cobalt permanent magnet with high temperature resistance is obtained, making it have temperature stability at high temperatures, but also the coercivity and magnetic energy product of the magnet during temperature change are improved. The samarium-cobalt permanent magnet with high temperature resistance prepared by the present invention reaches the magnetic properties of the samarium-cobalt magnet at 550 °C: Hcj≥7.5 kOe, (BH)max≥9 MGOe.

[0040] 2. The samarium-cobalt permanent magnet prepared by the present invention solves the problems of the sharp decline in magnetic properties of the existing samarium-cobalt magnet at temperatures above 350 °C and the limited scope of its use.

[0041] 3. The preparation method of the present invention is simple, the process is easy to control, the cycle is short, the cost is low, and it is easy to industrialize production.

[0042] The present invention is applicable to the preparation of samarium-cobalt permanent magnets with high temperature resistance.

[0043] The following will be further described in detail in conjunction with specific embodiments. Specific Embodiments

[0044] In the following examples, unless otherwise specified, the reagents used are all commercially available reagents, and the following experimental methods and detection methods are all existing experimental methods and detection methods unless otherwise specified.

[0045] Example 1

[0046] This example is a preparation method of a samarium-cobalt permanent magnet with high temperature resistance, which is carried out in the following steps in sequence:

[0047] (1) Alloy melting and casting into sheets

[0048] According to the ratio design, the compositions of the first cast sheet and the second cast sheet are designed. The composition of the first cast sheet is expressed by weight percentage as Sm 25 Co 51.5 Cu 9 Zr 3.5 Fe 11 , and the weight percentage of the composition of the second cast sheet is Gd 47 Co 28 Ti 10 Cu 15 , and the first cast sheet and the second cast sheet are respectively prepared by the rapid solidification and spinning melting method and casting. The first cast sheet process has a casting temperature of 1430 °C and a thickness of 0.15 - 0.45 mm; the second cast sheet process controls the casting temperature at 1450 °C and a thickness of 0.1 - 0.35 mm;

[0049] (2) Coarse crushing

[0050] The first ingot and the second ingot are respectively subjected to hydrogen crushing to obtain the first coarse powder and the second coarse powder;

[0051] (3) Jet milling

[0052] Antioxidants are respectively added to the first coarse powder and the second coarse powder (the addition amount of the antioxidant in the first coarse powder is 0.8‰ of the mass of the first coarse powder, and the addition amount of the antioxidant in the second coarse powder is 0.8‰ of the mass of the second coarse powder). After stirring for 60 min, jet milling is carried out under a grinding pressure of 0.55 MPa to respectively obtain the first fine powder and the second fine powder with D50 of 4 - 6 μm; the second fine powder and the first fine powder are mixed to form a mixed fine powder (the addition amount of the second fine powder accounts for 6% of the total weight of the two fine powders), and then a lubricant is added (the addition amount of the lubricant is 0.6‰ of the mass of the mixed fine powder), and after stirring for 2 h, a uniform samarium-cobalt double alloy fine powder is obtained;

[0053] (4) Orientation forming and cold isostatic pressing

[0054] The samarium-cobalt double alloy fine powder is taken for pressing and orientation forming, with an orientation magnetic field of 1.8 T and a forming pressure of 5 MPa, and then it is cold isostatically pressed at 180 MPa for 15 s to obtain a green compact with a density of 6.3 g / cm 3 ;

[0055] (5) Sintering and solution treatment

[0056] The green compact is kept at 1215 °C for 3 h, then cooled to 1185 °C and kept for 4 h for solution treatment, and then quickly air-cooled to room temperature;

[0057] (6) Aging treatment

[0058] The product in step (5) is subjected to aging treatment, which is divided into three stages. The first-stage aging treatment is carried out at 810 °C for 15 h, and then the first cooling is carried out at a cooling rate of 0.2 °C / min; the second-stage aging treatment is carried out at 630 °C for 8 h, and then the second cooling is carried out at a cooling rate of 0.5 °C / min; the third-stage aging treatment is carried out at 400 °C for 3 h, and then argon is filled and air-cooled for the third cooling to 20 - 30 °C to obtain the samarium-cobalt permanent magnet.

[0059] The composition of the product prepared in this example is expressed by weight percentage: Sm 23.5 Gd 2.82 Co 50.09 Ti 0.6 Cu 9.36 Zr 3.29 Fe 10.34 ;

[0060] The product prepared in this example was tested by using a NIM-6500 tester to obtain the final magnetic properties of the samarium cobalt magnet at 550° C.: Hcj was 7.72 kOe, and (BH)max was 9.21 MGOe.

[0061] Embodiment 2-4

[0062] Examples 2-4 respectively prepare a high temperature resistant samarium cobalt permanent magnet, and the preparation method thereof is similar to that of Example 1, except that the technical parameters in the preparation process are different, as shown in the following table.

[0063]

[0064]

[0065] Example 5 Comparative Example

[0066] Comparative Example 1:

[0067] This comparative example prepares a method for preparing a high temperature resistant samarium cobalt permanent magnet. The preparation process is similar to that of Example 1, except that the composition of the first casting sheet is different, as follows:

[0068] (1) The ingredients are prepared according to the formula design, and the weight percentage of the first casting composition is Sm 16 Co 51.5 Cu 10 Zr 3.5 Fe 19 The weight percentage of the second casting composition is Gd 47 Co 28 Ti 10 Cu 15 .

[0069] (2) The prepared product of Comparative Example 1 was tested using a NIM-6500 tester to obtain the final magnetic properties of the samarium cobalt magnet at 550° C., as shown in Table 1.

[0070] Comparative Example 2:

[0071] In this comparative example, a high temperature resistant samarium cobalt permanent magnet is prepared. The preparation process is similar to that of Example 1, except that the composition of the first casting sheet is different, as follows:

[0072] (1) The ingredients are prepared according to the formula design, and the weight percentage of the first casting composition is Sm 30 Co 51.5 Cu 10 Zr 3.5 Fe 5 The weight percentage of the second casting composition is Gd 47 Co 28 Ti10 Cu 15 。

[0073] (2) The prepared product of Comparative Example 2 was tested by a NIM-6500 tester to obtain the magnetic properties of the samarium cobalt magnet at the final 550 °C, as shown in Table 1 specifically.

[0074] Comparative Example 3:

[0075] A high-temperature resistant samarium cobalt permanent magnet was prepared in this comparative example. The preparation process was similar to that of Example 1, except that the composition of the second cast sheet was different, specifically as follows:

[0076] (1) Ingredients were proportioned according to the designed formula composition. The weight percentage of the first cast sheet composition was Sm 25 Co 51.5 Cu 9 Zr 3.5 Fe 11 , and the weight percentage of the second cast sheet composition was (Pr 25 Nd 75 ) 47 Co 28 Ti 10 Cu 15 。

[0077] (2) The prepared product of Comparative Example 3 was tested by a NIM-6500 tester to obtain the magnetic properties of the samarium cobalt magnet at the final 550 °C, as shown in Table 1 specifically.

[0078] Comparative Example 4:

[0079] A high-temperature resistant samarium cobalt permanent magnet was prepared in this comparative example. The preparation process was similar to that of Example 1, except that the composition of the second cast sheet was different, specifically as follows:

[0080] (1) Ingredients were proportioned according to the designed formula composition. The weight percentage of the first cast sheet composition was Sm 25 Co 51.5 Cu 9 Zr 3.5 Fe 11 , and the weight percentage of the second cast sheet composition was Gd 47 Co 28 Al 10 Cu 15 。

[0081] (2) The prepared product of Comparative Example 4 was tested by a NIM-6500 tester to obtain the magnetic properties of the samarium cobalt magnet at the final 550 °C, as shown in Table 1 specifically.

[0082] Comparative Example 5:

[0083] In this comparative example, a high temperature resistant samarium cobalt permanent magnet is prepared. The preparation process is similar to that of Example 1, except that the composition of the second casting sheet is different, as follows:

[0084] (1) The ingredients are prepared according to the formula design, and the weight percentage of the first casting composition is Sm 25 Co 51.5 Cu 9 Zr 3.5 Fe 11 The weight percentage of the second casting composition is Gd 47 Al 28 Ti 10 Cu 15 .

[0085] (2) The prepared product of Comparative Example 5 was tested using a NIM-6500 tester to obtain the final magnetic properties of the samarium cobalt magnet at 550° C., as shown in Table 1.

[0086] Comparative Example 6:

[0087] In this comparative example, a high temperature resistant samarium cobalt permanent magnet is prepared. The preparation process is similar to that of Example 1, except that the composition of the second casting sheet is different, as follows:

[0088] (1) The ingredients are prepared according to the formula design, and the weight percentage of the first casting composition is Sm 25 Co 51.5 Cu 9 Zr 3.5 Fe 11 The weight percentage of the second casting composition is Gd 47 Co 28 Ti 10 Ga 15 .

[0089] (2) The prepared product of Comparative Example 6 was tested using a NIM-6500 tester to obtain the final samarium cobalt magnet Br and Hcj at 550° C., as shown in Table 1.

[0090]

[0091] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of protection of the claims of the present invention.

Claims

1. A high-temperature resistant samarium cobalt permanent magnet, characterized in that, The components are expressed in weight percentages as: Sm u Gd v Co w Cu a Zr b Ti c Fe d , where u = 19.4% - 23.92%, v = 1.41% - 3.76%, w = 34.44% - 51.28%, a = 5.3% - 11.32%, b = 2.91% - 4.6%, c = 0.3% - 0.8%, and d = the balance; The preparation method of the high-temperature resistant samarium cobalt permanent magnet is prepared in the following step sequence: (1) Alloy melting and casting The first casting and the second casting are respectively prepared by a rapid solidification melting method and casting. The composition of the first casting is expressed by weight percentage as Sm f Co g Cu h Zr i Fe k , where f = 20% - 26%, g = 35% - 52%, h = 5% - 11%, i = 3% - 5%, k = the balance. The weight percentage of the composition of the second casting is Gd 47 Co 28 Ti 10 Cu 15 ; (2) Coarse crushing The first casting and the second casting are respectively subjected to hydrogen crushing to obtain the first coarse powder and the second coarse powder; (3) Jet milling Antioxidants are respectively added to the first coarse powder and the second coarse powder, and after stirring for 30 - 60 min, jet milling is carried out under a grinding pressure of 0.5 - 0.6 MPa to respectively obtain first fine powder and second fine powder with D50 of 4 - 6 μm; the second fine powder and the first fine powder are mixed to form a mixed fine powder, the addition amount of the second fine powder accounts for 3 - 8% of the total weight of the two fine powders, and then a lubricant is added and stirred for 1.5 - 4 h to obtain a uniform samarium cobalt double alloy fine powder; (4) Orientation forming, cold isostatic pressing Take the samarium-cobalt double alloy fine powder for pressing and orientation forming, and then perform cold isostatic pressing on it under a pressure of 180-220 MPa for 10-30 s to obtain a green compact with a density of 6.0-6.8 g / cm 3 ³; (5) Sintering and solution treatment The green body is heat-preserved at 1180 - 1230 °C for 2 - 4 h, and then cooled to 1160 - 1200 °C for heat-preserving for 3 - 5 h for solution treatment, and then quickly air-cooled to room temperature; (6) Aging treatment The product of step (5) is subjected to aging treatment to obtain a samarium cobalt permanent magnet.

2. The preparation method of a high-temperature resistant samarium cobalt permanent magnet according to claim 1, characterized in that, In step (1), the casting temperature of the first casting is 1380 - 1480 °C, and the thickness is 0.15 - 0.45 mm; the casting temperature of the second casting is 1360 - 1470 °C, and the thickness is 0.1 - 0.35 mm.

3. The preparation method of a high-temperature resistant samarium cobalt permanent magnet according to claim 1, characterized in that, In step (4), the orientation magnetic field is 1.8 - 2.2 T, and the forming pressure is 3 - 5 MPa.

4. The preparation method of a high-temperature resistant samarium cobalt permanent magnet according to claim 1, characterized in that, In step (6), the aging treatment is divided into three stages. The first-stage aging treatment is heat-preserved at 810 °C for 15 h, and then cooled for the first time; the second-stage aging treatment is heat-preserved at 630 °C for 8 h, and then cooled for the second time; the third-stage aging treatment is heat-preserved at 400 °C for 3 h, and then cooled for the third time to obtain a samarium cobalt permanent magnet.

5. The preparation method of a high-temperature resistant samarium cobalt permanent magnet according to claim 1, characterized in that, In step (3), the addition amount of the antioxidant in the first coarse powder or the second medium coarse powder is 0.5 - 1‰ of the mass of the first coarse powder or the second coarse powder, and the addition amount of the lubricant is 0.5 - 0.8‰ of the mass of the mixed fine powder.

6. The preparation method of a high-temperature resistant samarium cobalt permanent magnet according to claim 4, characterized in that, The cooling rates of the first cooling and the second cooling are 0.2 - 0.6 °C / min, and the third cooling is air-cooled with argon filling to 20 - 30 °C.

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