Joule heating aging treatment method of samarium cobalt-based rare earth permanent magnet material

Abstract

The invention provides a Joule heating aging treatment method for a samarium cobalt-based rare earth permanent magnet material, and relates to the technical field of rare earth permanent magnet materials. The Joule heating aging treatment method of the samarium-cobalt-based rare earth permanent magnet material comprises the steps of cast ingot preparation, crushing powder preparation, forming and solution treatment, Joule heating aging treatment and cooling treatment. According to the method, the samarium-cobalt permanent magnet material is rapidly processed by Joule heating strong pulse current, atom migration and agglomeration are inhibited, high-density vacancy defects and dislocations are reserved, cell wall phase nucleation is promoted, the heat preservation time is greatly shortened, and the efficiency is improved and the cost is reduced by several times. The prepared material is uniform and fine in nano cellular structure, the key magnetic performance reaches the commercial level or even better, the process is simple, the method is suitable for industrial production, and the good application prospect is achieved.

Description

Technical Field

[0001] This invention relates to the field of rare earth permanent magnet materials technology, and in particular to a method for Joule heating aging treatment of samarium cobalt-based rare earth permanent magnet materials. Background Technology

[0002] Samarium cobalt rare-earth permanent magnets possess high Curie temperatures, excellent temperature stability, and corrosion resistance, making them the strongest permanent magnets at high temperatures. They hold broad application prospects in high-end fields such as aerospace and microwave communications. Samarium cobalt permanent magnets are typically prepared using powder metallurgy, a process that includes melting, crushing, powdering, magnetic field orientation, pressing, and heat treatment. The heat treatment process, encompassing key steps such as sintering, solution treatment, and aging, plays a decisive role in the final magnetic properties of the material.

[0003] However, traditional aging processes employ conventional heating methods such as box furnaces or tube furnaces, which suffer from slow heating rates and long processing times. This slow heating process causes dislocations in the solid solution alloy to annihilate during the heating stage, sacrificing the internal defect structure of the material and weakening the driving force for the nucleation of precipitated phases during subsequent phase decomposition. Therefore, it is necessary to compensate by extending the holding time. This not only leads to excessively long heat treatment cycles and low production efficiency, but also brings a series of problems such as high energy consumption and increased production costs, severely restricting the industrial production efficiency of samarium cobalt rare earth permanent magnet materials. In addition, prolonged high-temperature holding can easily cause the growth and coarsening of cellular structures, adversely affecting the magnetic properties of the material.

[0004] Therefore, there is an urgent need to develop a new aging treatment method that can shorten the aging process time, improve production efficiency, reduce energy consumption, and ensure that samarium cobalt-based rare earth permanent magnet materials obtain excellent magnetic properties and ideal microstructure. Summary of the Invention

[0005] In view of this, the present invention provides a Joule heating aging treatment method for samarium cobalt-based rare earth permanent magnet materials. The present invention achieves rapid heating by using Joule heating technology, effectively preserving the high-density defect structure inside the material and promoting the nucleation of the phase decomposition process. Thus, while significantly shortening the aging time, it obtains a uniform and complete nanocellular structure and excellent comprehensive magnetic properties.

[0006] The first aspect of this invention is to provide a method for Joule heating aging treatment of samarium cobalt-based rare earth permanent magnet materials, comprising the following steps: S1. Ingot preparation: Samarium-cobalt alloy ingots were prepared using powder metallurgy. S2. Crushing and grinding: Crushing the ingots into powder; S3. Shaping and solution treatment: The powder is oriented and pressed by magnetic field, followed by sintering and solution treatment to obtain a solid solution magnet; S4. Joule heating aging treatment: The solid solution magnet is heated to 810-890℃ within 20-45 min by Joule heating and held at that temperature for 5 min-5 h to complete the aging treatment. S5. Cooling treatment: After aging treatment, air-cool to room temperature; Alternatively, cool to 380℃-420℃ at a cooling rate of 10-20℃ / min for secondary aging, and then cool to room temperature; Alternatively, cool to 380℃-420℃ at a cooling rate of 10-20℃ / min and then directly cool to room temperature.

[0007] Preferably, in step S1, a samarium-cobalt alloy ingot containing Sm, Co, Fe, Cu and Zr alloying elements is prepared using powder metallurgy.

[0008] Preferably, in step S2, the ingot is ground into powder of 2-6 μm using an air jet mill or ball mill.

[0009] Preferably, in step S4, the Joule heating is achieved by using graphite as a reactor and contact heating through a short-duration strong pulse current; the heating rate is 20-40℃ / min, the aging temperature is 830℃-860℃, and the holding time is 0.5-3 h.

[0010] Preferably, in step S5, the temperature for the second-stage aging is 380℃, and the holding time for the second-stage aging is 0.5-1h. More preferably, in step S5, the cooling rate is 6-20℃ / min.

[0011] Preferably, the overall delivery time is 80-285 min.

[0012] A second aspect of the present invention is to provide a samarium-cobalt-based rare-earth permanent magnet material prepared according to the above method, the material having a uniform and complete nanocellular structure, comprising: an intracellular phase: Fe-rich Sm2Co 17 R is a rhombohedral phase; cell wall phase: Cu-rich SmCo5H hexagonal phase; lamellar phase: Zr-rich SmCo3R lamellar phase, which runs through the cellular structure. Compared with materials prepared by traditional aging processes, the nanocellular structure is more uniform and complete, and the cellular structure does not show obvious growth and coarsening.

[0013] This invention utilizes Joule heating to regulate the microstructure evolution of samarium-cobalt-based rare-earth permanent magnet materials. In traditional aging processes, the slow heating rate leads to the annihilation of dislocations in the solid solution alloy during heating, sacrificing nearby defect structures and weakening the driving force for precipitation nucleation in subsequent phase decomposition. This invention employs Joule heating technology, using graphite as a reactor and applying a short-duration, strong pulsed current to achieve rapid contact heating. This extremely fast heating rate effectively suppresses the migration and aggregation of metal atoms, efficiently generating and maintaining a high density of vacancy defects and dislocation structures within the material. These retained defects provide abundant heterogeneous nucleation sites for phase decomposition during the subsequent holding stage, promoting the precipitation and nucleation of the Cu-rich SmCo5H cell wall phase. This allows dislocations to gradually form and dissociate during the simultaneous precipitation and recrystallization process. Through this mechanism, this invention significantly shortens the holding time while obtaining a more uniform, complete, and fine nanocellular structure, effectively preventing the growth and coarsening of the cellular structure. In this tissue, intracellular Fe-rich Sm2Co 17 The rhombohedral phase provides high saturation magnetization and remanence, while the Cu-rich SmCo5H hexagonal phase provides high coercivity through domain wall pinning. The Zr-rich SmCo3R lamellar phase serves as a diffusion channel throughout the cellular structure. The synergistic effect of these three phases achieves excellent overall magnetic properties. The entire aging process time is significantly reduced from 10-40 hours in traditional processes to 80-285 minutes. While significantly improving production efficiency, key performance indicators such as remanence, intrinsic coercivity, and maximum energy product of the magnet reach or even exceed the levels of commercial magnets.

[0014] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention employs Joule heating to age samarium-cobalt-based rare-earth permanent magnet materials. By using graphite as a reactor and utilizing short-duration, high-pulse currents to achieve rapid contact heating, the material can be heated to the aging temperature in an extremely short time. This extremely rapid heating rate effectively suppresses the migration and aggregation of metal atoms, efficiently generating and maintaining a high density of vacancy defects and dislocation structures within the material. These retained defects provide abundant heterogeneous nucleation sites for the phase decomposition process, significantly promoting the precipitation and nucleation of the cell wall phase. This drastically reduces the required holding time, increases production efficiency several times over, and significantly reduces energy consumption and production costs.

[0015] The samarium-cobalt-based rare-earth permanent magnet material prepared by this invention possesses a more uniform, complete, and fine nanocellular structure. Compared with materials prepared by traditional aging processes, the cellular structure does not exhibit significant growth or coarsening. This optimized microstructure enhances the magnetic properties of the material, with key performance indicators such as remanence (Br), intrinsic coercivity (Hcj), and maximum energy product (BH)max approaching or even exceeding the levels of commercial magnets. This demonstrates that this invention can still achieve excellent overall magnetic properties while significantly shortening the aging time and improving production efficiency.

[0016] The process of this invention is simple and easy to implement, and it is suitable for industrial-scale production. It is of great significance for improving the production efficiency of samarium cobalt rare earth permanent magnet materials, reducing production costs, and promoting the widespread application of such materials in high-end fields. Detailed Implementation

[0017] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Unless otherwise specified, all experiments were repeated three times, and the results are expressed as averages.

[0019] Example 1: A method for Joule heating aging treatment of samarium cobalt-based rare earth permanent magnet materials, comprising the following steps: S1. Ingot Preparation: Samarium-cobalt alloy ingots were prepared using powder metallurgy. The elemental composition of the ingots, by weight percentage, is as follows: Sm 24%, Fe 16.8%, Cu 5.4%, Zr 1.8%, Co 52%. S2. Crushing and grinding: The ingot is crushed and ground into powder of 2-6 μm (obtained by sieving) using an air jet mill. S3. Forming and Solution Treatment: The powder is oriented in a 2 T magnetic field, and then the oriented powder is pressed into a compact under a pressure of 200 MPa to obtain a compact. The compact is sintered at 1200℃ for 2 h under an argon protective atmosphere to obtain a high-density sintered compact. The sintered compact is then solution treated at 1180℃ for 2 h, and then cooled to room temperature by strong air cooling to obtain a uniform supersaturated solid solution. S4. Joule heating aging treatment and cooling treatment: The solid solution magnet is aged by Joule heating. The temperature is increased to 830℃ at a heating rate of 20℃ / min and held for 0.5 h. Then it is cooled to 380℃ at a cooling rate of 6℃ / min and then cooled to room temperature in the furnace. The total aging time is 145 min.

[0020] Test results show that the remanence Br of the magnet is 11.36 kGs, the intrinsic coercivity Hcj is 18.19 kOe, and the maximum energy product (BH) is... max It is 28.51 MGOe.

[0021] Example 2 The difference from Example 1 is that: in S2, the powder is ground by ball milling; in S4, the temperature is raised to 840°C at a heating rate of 30°C / min and held for 1 h, then cooled to 380°C at a cooling rate of 8°C / min and held for 0.5 h, and then cooled to room temperature in the furnace. The overall aging time is 175 min.

[0022] Test results show that the remanence Br of the magnet is 11.25 kGs, the intrinsic coercivity Hcj is 21.99 kOe, and the maximum energy product (BH) is... max It is 28.48 MGOe.

[0023] Example 3 The difference from Example 1 is that in S4, the temperature is raised to 850°C at a heating rate of 30°C / min and held for 2 hours. Then, it is cooled to 380°C at a cooling rate of 10°C / min and held for 1 hour. Finally, it is cooled to room temperature in the furnace. The overall aging time is 255 minutes.

[0024] Test results show that the remanence Br of the magnet is 11.24 kGs, the intrinsic coercivity Hcj is 22.72 kOe, and the maximum energy product (BH) is... max It is 27.93 MGOe.

[0025] Example 4 The difference from Example 1 is that in S4, the temperature is raised to 830°C at a heating rate of 30°C / min, held for 3 hours, and then cooled to 380°C at a cooling rate of 6°C / min. The temperature is then cooled to room temperature in the furnace, and the overall aging time is 282 min.

[0026] Test results show that the remanence Br of the magnet is 11.21 kGs, the intrinsic coercivity Hcj is 18.09 kOe, and the maximum energy product (BH) is... max It is 26.89 MGOe.

[0027] Example 5 The difference from Example 1 is that: in S2, the powder is ground by ball milling; in S4, the temperature is raised to 840°C at a heating rate of 30°C / min, held for 0.5 h, then cooled to 380°C at a cooling rate of 12°C / min, and then cooled to room temperature in the furnace. The overall aging time is 96 min.

[0028] Test results show that the remanence Br of the magnet is 11.35 kGs, the intrinsic coercivity Hcj is 18.72 kOe, and the maximum energy product (BH) is... max It is 28.32 MGOe.

[0029] Example 6 The difference from Example 1 is that in S4, the temperature is raised to 850°C at a heating rate of 40°C / min, held for 1 hour, and then cooled to 380°C at a cooling rate of 15°C / min. Then, it is cooled to room temperature in the furnace, and the overall aging time is 112 min.

[0030] Test results show that the remanence Br of the magnet is 11.32 kGs, the intrinsic coercivity Hcj is 19.46 kOe, and the maximum energy product (BH) is... max It is 27.26 MGOe.

[0031] Example 7 The difference from Example 1 is that: in S2, the powder is ground by ball milling; in S4, the temperature is raised to 850°C at a heating rate of 30°C / min, held for 2 hours, then cooled to 380°C at a cooling rate of 20°C / min, and then cooled to room temperature in the furnace. The overall aging time is 171 min.

[0032] Test results show that the remanence Br of the magnet is 11.25 kGs, the intrinsic coercivity Hcj is 18.12 kOe, and the maximum energy product (BH) is... max It is 26.18 MGOe.

[0033] Example 8 The difference from Example 1 is that in S4, the temperature is increased to 860°C at a heating rate of 25°C / min, held for 2 hours, and then cooled to 380°C at a cooling rate of 15°C / min before being directly cooled to room temperature. The overall aging time is 186 min.

[0034] Test results show that the remanence Br of the magnet is 11.22 kGs, the intrinsic coercivity Hcj is 18.47 kOe, and the maximum energy product (BH) is... max It is 26.11 MGOe.

[0035] Currently, commercially available magnets (magnets with the grade 30H) undergo aging treatment using traditional electric furnace heating methods, with treatment times ranging from 10 to 40 hours. The resulting magnets have a remanence of 9-11 kGs, an intrinsic coercivity of 20-30 kOe, and a maximum energy product (BH). max The value is 20-30 MGOe. It is evident that this invention, while significantly shortening the aging process time, still achieves comprehensive performance comparable to commercial magnets.

[0036] Comparative Example 1 The difference from Example 1 is that: in S4, a traditional electric furnace heating method is used, the temperature is raised to 830°C at a heating rate of 10°C / min, held for 0.5 h, and then cooled to 380°C at a cooling rate of 6°C / min, and then cooled to room temperature with the furnace. The overall aging time is 186 min.

[0037] Test results show that the remanence Br of the magnet is 11.02 kGs, the intrinsic coercivity Hcj is 16.93 kOe, and the maximum energy product (BH) is... max It was 25.76 MGOe, with uneven cellular structure.

[0038] Comparative Example 2 The difference from Example 2 is that: in S4, Joule heating is used, but the heating rate is only 5°C / min (lower than the scope of the invention), the temperature is raised to 840°C, held for 1 h, then cooled to 380°C at a cooling rate of 8°C / min and held for 0.5 h, and then cooled to room temperature with the furnace. The overall aging time is 312 min.

[0039] Test results show that the remanence Br of the magnet is 11.14 kGs, the intrinsic coercivity Hcj is 15.37 kOe, and the maximum energy product (BH) is... max It is 25.18 MGOe.

[0040] Comparative Example 3 The difference from Example 1 is that the aging temperature in S4 is 800℃ (lower than the invention range of 810-890℃), the temperature is increased at a rate of 20℃ / min, held for 0.5h, then cooled to 380℃ at a rate of 6℃ / min, and then cooled to room temperature in the furnace. The overall aging time is 139 min.

[0041] Test results show that the remanence Br of the magnet is 10.79 kGs, the intrinsic coercivity Hcj is 17.34 kOe, and the maximum energy product (BH) is... max The value was 20.13 MGOe, and the cellular structure was uneven.

[0042] Comparative Example 4 The difference from Example 3 is that the aging temperature in S4 is 900℃ (higher than the invention range of 810-890℃), the temperature is increased at a rate of 30℃ / min, held for 2 hours, then cooled to 380℃ at a rate of 10℃ / min and held for 1 hour, and then cooled to room temperature in the furnace. The overall aging time is 262 minutes.

[0043] Test results show that the remanence Br of the magnet is 10.79 kGs, the intrinsic coercivity Hcj is 15.18 kOe, and the maximum energy product (BH) is... max The value was 19.61 MGOe, and the cellular tissue was significantly coarsened.

[0044] Comparative Example 5 The difference from Example 1 is that: in S4, a traditional electric furnace heating method is used, the temperature is raised to 830°C at a heating rate of 10°C / min, and held for 10 h (traditional long-term aging), and then cooled to 380°C at a cooling rate of 6°C / min, and then cooled to room temperature with the furnace. The overall aging time is 13 h.

[0045] Test results show that the remanence Br of the magnet is 11.01 kGs, the intrinsic coercivity Hcj is 17.51 ​​kOe, and the maximum energy product (BH) is... max The concentration was 25.1 MGOe, but the aging time was significantly prolonged, and the cellular tissue was uneven.

[0046] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for Joule heating aging treatment of samarium cobalt-based rare earth permanent magnet materials, characterized in that, Includes the following steps: S1. Ingot preparation: Samarium-cobalt alloy ingots were prepared using powder metallurgy. S2. Crushing and grinding: Crushing the ingots into powder; S3. Shaping and solution treatment: The powder is oriented and pressed by magnetic field, followed by sintering and solution treatment to obtain a solid solution magnet; S4. Joule heating aging treatment: The solid solution magnet is heated to 810-890℃ within 20-45 min by Joule heating and held at that temperature for 5 min-5 h to complete the aging treatment. S5. Cooling treatment: After aging treatment, air-cool to room temperature; Alternatively, cool to 380℃-420℃ at a cooling rate of 10-20℃ / min for secondary aging, and then cool to room temperature; Alternatively, cool to 380℃-420℃ at a cooling rate of 10-20℃ / min and then directly cool to room temperature.

2. The Joule heating aging treatment method for samarium cobalt-based rare earth permanent magnet materials according to claim 1, characterized in that, In step S1, a samarium-cobalt alloy ingot containing Sm, Co, Fe, Cu and Zr alloying elements is prepared using powder metallurgy.

3. The Joule heating aging treatment method for samarium cobalt-based rare earth permanent magnet materials according to claim 1, characterized in that, In step S2, the ingot is ground into powder of 2-6 μm using an air jet mill or ball mill.

4. The Joule heating aging treatment method for samarium cobalt-based rare earth permanent magnet materials according to claim 1, characterized in that, In step S4, the Joule heating is achieved by using graphite as a reactor and contact heating through a short-duration strong pulse current.

5. The Joule heating aging treatment method for samarium cobalt-based rare earth permanent magnet materials according to claim 1, characterized in that, In step S4, the heating rate is 20-40℃ / min, the aging temperature is 830℃-860℃, and the holding time is 0.5-3 h.

6. The method for Joule heating aging treatment of samarium cobalt-based rare earth permanent magnet materials according to claim 1, characterized in that, In step S5, the temperature for the second-stage aging is 380℃, and the holding time for the second-stage aging is 0.5-1 h.

7. The Joule heating aging treatment method for samarium cobalt-based rare earth permanent magnet materials according to claim 1, characterized in that, In step S5, the cooling rate is 6-20℃ / min.

8. The method for Joule heating aging treatment of samarium cobalt-based rare earth permanent magnet materials according to claim 1, characterized in that, The overall delivery time is 80-285 minutes.

9. The samarium-cobalt-based rare-earth permanent magnet material prepared by the method according to any one of claims 1-8, characterized in that, The samarium cobalt-based rare earth permanent magnet material has a uniform and complete nanocellular structure, including: intracellular phase: Fe-rich Sm2Co 17 Rhoid phase; cell wall phase: Cu-rich SmCo5H hexagonal phase; lamellar phase: Zr-rich SmCo3R lamellar phase, penetrating the cellular tissue.