Preparation method for improving performance of samarium-cobalt magnet

Abstract

The invention belongs to the technical field of rare earth permanent magnet materials, and particularly relates to a preparation method for improving the performance of a samarium-cobalt magnet. In order to simply and efficiently improve the magnetic performance of the samarium-cobalt magnet, the samarium-cobalt magnet subjected to sintering solution treatment is subjected to vacuum plastic packaging, then pre-stress treatment is performed, and finally aging treatment is performed to obtain the final-state samarium-cobalt magnet.

Description

Technical Field

[0001] This invention belongs to the field of rare earth permanent magnet materials technology, specifically relating to a preparation method for improving the performance of samarium cobalt magnets. Background Technology

[0002] As a second-generation rare-earth permanent magnet material, samarium cobalt magnets possess the strongest magnetic properties at high temperatures, making them difficult to replace with other permanent magnet materials in high-temperature applications such as aerospace, defense, and microwave communication technology. In recent years, with the rapid development of my country's rail transit and the increasing emphasis on energy conservation and emission reduction in industry, the demand for samarium cobalt magnets, the only material capable of meeting these requirements, has increased rapidly, driving its development towards higher performance.

[0003] Currently, researchers are not only improving the magnetic properties of samarium-cobalt magnets by designing formulations to increase the Fe content and appropriately reduce the content of non-ferromagnetic elements Cu and Zr, but also further exploring the magnetic potential of samarium-cobalt magnets through process optimization, equipment upgrades, and technological innovation. Patent CN112927920A discloses a method for preparing high-performance samarium-cobalt permanent magnets by applying compressive stress during isothermal aging. This method not only improves the magnetic properties of the magnets but also shortens the preparation process for magnets of the same grade. However, the preparation process is relatively complex and has high requirements for the shape and size of the magnets. Patent CN118156014A uses ultra-high pressure pre-aging treatment to improve the coercivity of samarium-cobalt magnets, but this is also limited by the shape and size of the magnets and requires investment in new equipment (a six-sided press). Patent CN113539596A prepares high-performance samarium-cobalt magnets through microwave heating. Although this method can significantly shorten the magnet preparation cycle, the coercivity remains low without long-term aging treatment. Furthermore, it introduces a new microwave sintering furnace, increasing production costs. The aforementioned existing technologies suffer from low production efficiency and high equipment investment.

[0004] Therefore, based on the deepening understanding of the phase transition mechanism of samarium cobalt magnets, this invention proposes that samarium cobalt magnets undergo prestressing treatments such as cold isostatic pressing after sintering and solution treatment to change the internal defects of the material, thereby accelerating the solid-state phase transition process and significantly improving the magnetic properties of samarium cobalt magnets. Summary of the Invention

[0005] This invention provides a method for improving the performance of samarium-cobalt magnets to address the aforementioned problems. The method involves applying prestress to the magnet before aging treatment to promote the decomposition and transformation of the 1:7 phase in the solution-treated state, forming a complete nanocellular structure, thereby improving the coercivity and energy product of the magnet.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a method for preparing samarium-cobalt magnets with improved performance, comprising the following steps:

[0008] Step 1: Vacuum encapsulate the sintered solution-treated samarium cobalt magnet;

[0009] Step 2: Perform prestressing treatment on the vacuum-sealed samarium-cobalt magnet;

[0010] Step 3: The prestressed samarium cobalt magnet is subjected to aging treatment to obtain a high-performance samarium cobalt magnet.

[0011] Furthermore, the prestressing treatment in step 2 is performed by cold isostatic pressing, hot isostatic pressing, or by applying a certain pressure through pressurizing equipment (various hydraulic presses).

[0012] Furthermore, the cold isostatic pressing conditions are to hold the pressure at 50~300 MPa for 0.5~10 min.

[0013] Furthermore, the samarium cobalt magnet in the sintered solution-treated state of step 1 is prepared through the following steps:

[0014] (1) Remove the surface oxide scale from the metal raw materials samarium (Sm), cobalt (Co), iron (Fe), copper (Cu), and zirconium (Zr), and then perform vacuum medium-frequency induction melting to obtain alloy ingots, or perform vacuum rapid solidification melting to obtain rapid solidification sheets.

[0015] (2) The alloy ingot or quick-setting sheet is sequentially subjected to jaw crusher coarse crusher, disc mill fine crusher and air jet mill to obtain magnetic powder;

[0016] (3) The magnetic powder is oriented and shaped under a magnetic field, and then cold isostatically pressed to obtain a green body;

[0017] (4) The green blank is sintered, then cooled to a certain temperature for solid solution treatment, and then rapidly air-cooled to room temperature to obtain a sintered solid solution treated samarium cobalt magnet.

[0018] Furthermore, the particle size of the magnetic powder in step (2) is 3~6 μm.

[0019] Furthermore, in step (3), the strength of the magnetic field is 1~3 T; the pressure of cold isostatic pressing is 100~300 MPa, and the time is 10~60 s.

[0020] Furthermore, the chemical formula of the samarium-cobalt magnet is Sm(Co) bal. Fe u Cu v Zr w ) z , where z represents the atomic ratio of rare earth element Sm to the total of Co+Fe+Cu+Zr elements, z is between 7 and 8, u=0.10~0.35, v=0.04~0.1, w=0.01~0.08.

[0021] Furthermore, in step 3, the aging treatment is carried out at 790~850℃ for 3~20 h, followed by slow cooling to 400℃ at a cooling rate of 0.5~1.5℃ / min, and then holding at that temperature for 1~10 h, and finally cooling to room temperature to obtain the final magnet.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] This invention uses prestressing methods such as cold isostatic pressing to significantly improve the coercivity and magnetic energy product of Sm-Co sintered magnets, and can also shorten the subsequent aging treatment time (preparation process). This achieves cost reduction and efficiency improvement of samarium-cobalt magnets without the need for additional equipment investment. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the samarium-cobalt magnet preparation process of the present invention;

[0025] Figure 2 Sm(Co) obtained in Example 1 without prestressing treatment bal. Fe 0.305 Cu 0.07 Zr 0.04 ) 7.6 Comparison of hysteresis loops of magnets;

[0026] Figure 3 Sm(Co) obtained in Example 1 without prestressing treatment bal. Fe 0.305 Cu 0.07 Zr 0.04 ) 7.6 A schematic diagram of the nanocellular structure of a magnet. Detailed Implementation

[0027] To further illustrate the technical solution of the present invention, the present invention will be further described below through embodiments.

[0028] like Figure 1 As shown, a method for preparing a samarium-cobalt magnet with improved performance according to the present invention includes the following steps:

[0029] Step 1: Vacuum encapsulate the sintered solution-treated samarium cobalt magnet;

[0030] Step 2: Perform prestressing treatment on the vacuum-sealed samarium cobalt magnet. The prestressing treatment can be cold isostatic pressing, hot isostatic pressing, or applying a certain pressure through various hydraulic presses. The cold isostatic pressing condition is to hold the pressure at 50~300 MPa for 0.5~10 min.

[0031] Step 3: The prestressed samarium cobalt magnet is placed in a sintering furnace for aging treatment. The aging treatment is carried out at 790-850℃ for 3-20 h, and then slowly cooled to 400℃ at a cooling rate of 0.5-1.5℃ / min. The temperature is then held for 1-10 h, and the magnet is cooled to room temperature in the furnace to obtain the final magnet.

[0032] In this invention, the chemical formula of the samarium cobalt magnet is Sm(Co) bal. Fe u Cu v Zr w ) z , where z represents the atomic ratio of rare earth element Sm to the total of Co+Fe+Cu+Zr elements, z is between 7 and 8, u=0.10~0.35, v=0.04~0.1, w=0.01~0.08.

[0033] The specific preparation process of sintered solution-treated samarium cobalt magnets is as follows:

[0034] (1) According to Sm(Co) bal. Fe u Cu v Zr w ) z Weigh out metal raw materials with a purity >99.9wt.% including samarium (Sm), cobalt (Co), iron (Fe), copper (Cu), and zirconium (Zr), remove the surface oxide scale by mechanical grinding, and then place them in a vacuum medium-frequency induction melting furnace (or vacuum rapid solidification melting furnace) to obtain alloy ingots (or rapid solidification sheets).

[0035] (2) The alloy ingot or quick-setting sheet is successively crushed by jaw crusher, then by disc mill, and finally by air jet mill to obtain magnetic powder with a particle size of 3~6 μm.

[0036] (3) Orient the magnetic powder under a magnetic field of 1~3 T, and then cold isostatically press it under a pressure of 100~300 MPa for 10~60 s to obtain a green body;

[0037] (4) The green blank is sintered at 1170~1220 ℃ for 1~3 h, then cooled to 1150~1190 ℃ for solution treatment for 3~20 h, and then rapidly air-cooled to room temperature to obtain sintered solution-treated samarium cobalt magnet.

[0038] Example 1

[0039] In this embodiment, a traditional alloy ingot casting process was used to prepare an alloy with a nominal composition of Sm(Co). bal. Fe 0.305 Cu 0.07 Zr 0.04 ) 7.6 Sintered and solution-treated samarium-cobalt magnets. Two pieces measuring Φ10×10 mm were cut from the same magnet.3 Cylindrical samples were prepared. One sample was vacuum-sealed and placed in a cold isostatic pressing apparatus, where it was held at 200 MPa for 2 min. The treated sample and an untreated control sample were then marked and placed together in a vacuum sintering furnace for aging treatment. The aging treatment regime was as follows: holding at 820℃ for 15 h, followed by slow cooling to 400℃ at a rate of 0.7℃ / min and holding at that temperature for 1 h, and finally cooling to room temperature with the furnace to obtain the final magnet.

[0040] Compared to conventional magnets, the remanence B of the specimens treated with cold isostatic pressing prestressing is higher. r From 10.07 kG to 10.29 kG, coercivity H cj The maximum energy product (BH) increased from 32.97 kOe to 33.80 kOe. max From 23.30 MGOe to 24.76 MGOe, such as Figure 2 As shown. Furthermore, the increased coercivity of the magnet stems from the formation of a more complete nanocellular structure after prestressing treatment, as... Figure 3 As shown.

[0041] Example 2

[0042] In this embodiment, a rapid solidification process was used to prepare a product with a nominal composition of Sm(Co). bal. Fe 0.305 Cu 0.07 Zr 0.04 ) 7.6 Sintered and solution-treated samarium-cobalt magnets. Two pieces measuring Φ10×10 mm were cut from the same magnet. 3 Cylindrical samples were prepared. One sample was vacuum-sealed and placed in a cold isostatic pressing apparatus, where it was held at 200 MPa for 2 min. The treated sample and an untreated control sample were then marked and placed together in a vacuum sintering furnace for aging treatment. The aging treatment regime was as follows: holding at 815℃ for 20 h, followed by slow cooling to 400℃ at a rate of 0.7℃ / min and holding at that temperature for 1 h, and finally cooling to room temperature in the furnace to obtain the final magnet.

[0043] Compared to conventional magnets, the remanence B of the specimens treated with cold isostatic pressing prestressing is higher. r From 10.03 kG to 10.13 kG, coercivity H cj The maximum energy product (BH) increased from 28.42 kOe to 29.03 kOe. max It increased from 21.48 MGOe to 22.37 MGOe.

[0044] Example 3

[0045] In this embodiment, a commercially available XGS28H samarium cobalt magnet that has not undergone aging treatment was selected. Four pieces with dimensions of Φ10×10 mm were cut from the same sintered and solution-treated magnet. 3 Cylindrical samples were prepared. Three of these samples were vacuum-sealed and placed in a cold isostatic press, where they were held at 200 MPa for 1 min, 2 min, and 4 min respectively. One sample was kept as a control. The four marked samples were then placed together in a vacuum sintering furnace for aging treatment. The aging treatment regime was as follows: first, the sample was held at 830 ℃ for 6 h, then slowly cooled to 400 ℃ at a cooling rate of 0.7 ℃ / min and held for 1 h, and finally cooled to room temperature in the furnace to obtain the final magnet.

[0046] Compared to conventional magnets, the remanence B of the specimens treated with cold isostatic pressing (COP) increases with increasing holding time. r Coercivity H cj And the maximum magnetic energy product (BH) max It shows a trend of first increasing and then decreasing, reaching its maximum value after holding the pressure for 2 minutes, and its remanence B r From 10.95 kG to 11.00 kG, coercivity H cj The maximum energy product (BH) increased from 34.98 kOe to 35.18 kOe. max It increased from 27.72 MGOe to 28.11 MGOe.

[0047] Example 4

[0048] In this embodiment, XGS34H commercial samarium cobalt magnets that have not undergone aging treatment were selected. Six pieces with dimensions of Φ10×10 mm were cut from the same sintered solution-treated magnet. 3 Cylindrical samples were prepared. Five of these samples were vacuum-sealed and placed in a cold isostatic press, where they were held for 2 minutes at pressures of 50, 100, 150, 200, and 250 MPa, respectively. One sample was kept as a control. The six marked samples were then placed together in a vacuum sintering furnace for aging treatment. The aging treatment regime was as follows: first, the sample was held at 830 ℃ for 5 hours, then slowly cooled to 400 ℃ at a cooling rate of 0.7 ℃ / min and held for 1 hour, and finally cooled to room temperature in the furnace to obtain the final magnet.

[0049] Compared to conventional magnets, the magnetic properties of the specimens treated with cold isostatic pressing (COP) are significantly enhanced. Furthermore, the remanence (B) of the magnet increases with increasing COP. r Coercivity H cj And the maximum magnetic energy product (BH) max It shows a trend of first increasing and then decreasing, reaching its maximum value at a holding pressure of 150 MPa, and its remanence Br The weight increased from 10.90 kG to 11.64 kG, an increase of 6.79%, with a coercivity of H. cj The energy product increased from 13.79 kOe to 33.52 kOe, an increase of 143.09%, with the maximum energy product (BH) increasing. max It increased from 26.34 MGOe to 31.35 MGOe, an increase of 19.02%.

[0050] The specific test results of the magnetic properties of the Sm-Co sintered magnets in Examples 1 to 4 are shown in Table 1.

[0051] Table 1 Magnetic property test results

[0052]

[0053] The foregoing has shown and described the main features and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0054] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing samarium-cobalt magnets with improved performance, characterized in that, Includes the following steps: Step 1: Vacuum encapsulate the sintered solution-treated samarium cobalt magnet; Step 2: Perform prestressing treatment on the vacuum-sealed samarium cobalt magnet; Step 3: The prestressed samarium cobalt magnet is subjected to aging treatment to obtain a high-performance samarium cobalt magnet.

2. The method for preparing a samarium-cobalt magnet with improved performance according to claim 1, characterized in that, In step 2, the prestressing treatment is performed by cold isostatic pressing, hot isostatic pressing, or by applying a certain pressure through a pressurizing device.

3. The preparation method for improving the performance of samarium-cobalt magnets according to claim 2, characterized in that, The conditions for cold isostatic pressing are to hold the pressure at 50~300 MPa for 0.5~10 min.

4. The method for preparing a samarium-cobalt magnet with improved performance according to claim 1, characterized in that, The samarium cobalt magnet in the sintered solution-treated state in step 1 is prepared by the following steps: (1) Remove the surface oxide scale from the metal raw materials samarium, cobalt, iron, copper and zirconium, and then perform vacuum medium frequency induction melting to obtain alloy ingots, or perform vacuum rapid solidification melting to obtain rapid solidification sheets. (2) The alloy ingot or quick-setting sheet is sequentially subjected to jaw crusher coarse crusher, disc mill fine crusher and air jet mill to obtain magnetic powder; (3) The magnetic powder is oriented and shaped under a magnetic field, and then cold isostatically pressed to obtain a green body; (4) The green blank is sintered, then cooled to a certain temperature for solid solution treatment, and then rapidly air-cooled to room temperature to obtain a sintered solid solution treated samarium cobalt magnet.

5. The method for preparing a samarium-cobalt magnet with improved performance according to claim 4, characterized in that, The particle size of the magnetic powder in step (2) is 3~6 μm.

6. The preparation method for improving the performance of samarium-cobalt magnets according to claim 4, characterized in that, In step (3), the magnetic field strength is 1~3 T; the pressure of cold isostatic pressing is 100~300 MPa, and the time is 0.5~1 min.

7. The method for preparing a samarium-cobalt magnet with improved performance according to claim 1, characterized in that, The chemical formula of the samarium cobalt magnet is Sm(Co) bal. Fe u Cu v Zr w ) z , where z represents the atomic ratio of rare earth element Sm to the total of Co+Fe+Cu+Zr elements, z is between 7 and 8, u=0.10~0.35, v=0.04~0.1, w=0.01~0.

08.

8. The method for preparing a samarium-cobalt magnet with improved performance according to claim 1, characterized in that, In step 3, the aging treatment is carried out at 790~850℃ for 3~20 h, followed by slow cooling to 400℃ at a cooling rate of 0.5~1.5℃ / min, and then holding at that temperature for 1~10 h until the magnet is cooled to room temperature to obtain the final magnet.

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