Method for improving coercivity of samarium-cobalt magnet by rapid temperature rising and falling pretreatment
By employing a pretreatment method involving rapid heating, short-time holding, and rapid cooling, the challenge of improving the coercivity of samarium-cobalt magnets was solved. This resulted in a highly efficient and simplified fabrication process, enhancing the coercivity of samarium-cobalt magnets and meeting the stability requirements of high-temperature devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XI AN JIAOTONG UNIV
- Filing Date
- 2023-05-08
- Publication Date
- 2026-06-09
AI Technical Summary
Existing technologies struggle to effectively improve the coercivity of samarium-cobalt magnets without causing abnormal growth of cellular structures and early phase decomposition. Traditional pretreatment processes involve slow heating rates, which affect the formation of subsequent precipitated phases.
A pretreatment method of rapid heating-short holding-rapid cooling is adopted to promote the formation of SmCo5 precipitates by providing high-density initial defects before isothermal aging, thereby improving the coercivity of samarium cobalt magnets.
The method significantly improves the coercivity of samarium cobalt magnets, simplifies the preparation process, saves time and energy costs, and the prepared samarium cobalt magnets have high stability at room temperature, meeting the requirements of high-temperature devices.
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Figure CN116504477B_ABST
Abstract
Description
Technical Field
[0001] This disclosure belongs to the field of rare earth permanent magnet materials technology, and in particular to a rapid heating and cooling pretreatment method for improving the coercivity of samarium cobalt magnets. Background Technology
[0002] Rare earth permanent magnet materials are a class of permanent magnet materials based on intermetallic compounds formed by rare earth metal elements and transition metal elements. The second-generation rare earth permanent magnet material, 2:17 samarium cobalt, possesses excellent high-temperature magnetic properties, high Curie temperature, strong temperature stability, and strong corrosion resistance. It is widely used in high-temperature devices such as new motors, traveling wave tubes, and inertial navigation devices. Especially in special application areas (operating temperatures above 300℃) where neodymium iron boron magnets are difficult to match, the application of 2:17 samarium cobalt is irreplaceable.
[0003] High coercivity is crucial for the high stability of magnets under service conditions. The high coercivity of samarium cobalt magnets originates from the pinning effect of SmCo5 precipitates relative to the domain walls. To a certain extent, the higher the content of SmCo5 precipitates in the magnet, the stronger the pinning effect, and the higher the coercivity. The non-uniform desolvation process of the precipitates mainly occurs during the isothermal aging stage, where the precursor SmCo7 phase decomposes into Sm2Co. 17 Intracellular phase and SmCo5 cell wall precipitation phase 。 Therefore, besides adjusting the original component ratio, improving the isothermal aging process is generally used to promote the formation of precipitated phases and thus improve coercivity. For example, extending the aging time or using staged aging can improve the coercivity of magnets; however, this method involves a long preparation process and easily causes abnormal growth of cellular structures, resulting in limited effectiveness in improving coercivity. There are also methods to improve the coercivity of magnets by introducing intermediate pre-aging processes, but traditional pre-aging techniques have slow heating rates, inevitably leading to early phase decomposition during the pretreatment process, slowing down the precipitation kinetics in subsequent aging. Therefore, we urgently need a new aging process that simultaneously avoids abnormal growth of cellular structures and early phase decomposition, while promoting the formation of precipitated phases, thereby effectively improving the coercivity of magnets.
[0004] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the present disclosure aims to propose a rapid heating and cooling pretreatment method for improving the coercivity of samarium-cobalt magnets. This method utilizes rapid heating and cooling pretreatment to obtain high-density initial defects, providing numerous nucleation sites for SmCo5 precipitates, thereby promoting their formation and achieving high coercivity. Prior to isothermal aging, the magnet undergoes a rapid heating-short-time holding-rapid cooling process to accelerate precipitate formation, resulting in a significant improvement in the coercivity of the samarium-cobalt magnet.
[0006] To achieve the above objectives, this disclosure provides the following technical solution:
[0007] A method for improving the coercivity of samarium cobalt magnets includes the following steps:
[0008] The first step involves melting the metal raw materials in a vacuum induction furnace according to a specific ratio to obtain an ingot. The ingot contains an atomic percentage of Sm(Co). bal Fe u Cu v Zr w ) z Samarium cobalt magnets, 0.10≤u≤0.35, 0.04≤v≤0.10, 0.01≤w≤0.08, 7≤z≤8;
[0009] The second step is to crush the ingot to obtain alloy powder.
[0010] The third step is to mold the alloy powder in a magnetic field, and then cold isostatically press it to obtain a green blank.
[0011] The fourth step is to sinter the green blank and perform a solution treatment to obtain a sintered magnet;
[0012] The fifth step involves heating the sintered magnet in a heat treatment furnace from room temperature to 400-800°C at a heating rate of 50-150°C / s, holding it at that temperature for 30-300s, and then cooling it down to room temperature at a cooling rate of 5-50°C / s.
[0013] The sixth step involves aging the sintered magnet and then cooling it to room temperature to obtain a samarium cobalt magnet. The aging process consists of two steps: the first step involves aging at a temperature of 810–900°C for 5–40 hours, followed by a second aging process at a temperature of 0.7°C / min to 400°C for 1–20 hours, and then cooling to room temperature to obtain the samarium cobalt magnet.
[0014] In the method for improving the coercivity of samarium-cobalt magnets, in the first step, the samarium-cobalt magnet is prepared with an atomic percentage of Sm(Co). bal Fe u Cu v Zr w )z Where 0.10≤u≤0.35, 0.04≤v≤0.10, 0.01≤w≤0.08, and 7≤z≤8.
[0015] In the method for improving the coercivity of samarium-cobalt magnets, in the second step, the particle size of the alloy powder is 4~6 μm.
[0016] In the method for improving the coercivity of samarium cobalt magnets, in the third step, the molding pressure is ~150 MPa, the magnetic field strength is >1.0T, and the cold isostatic pressing pressure is 200~300 MPa.
[0017] In the method for improving the coercivity of samarium cobalt magnets, in the fourth step, the sintering temperature is 1190-1220℃, the sintering time is 0.5-3h, the solution treatment temperature is 1130-1190℃, and the sintering time is 1-8h.
[0018] In the method for improving the coercivity of samarium cobalt magnets, in the fifth step, the magnet is heated from room temperature to 600-900°C in a rapid heat treatment furnace at a heating rate of 50-150°C / s, held at that temperature for 30-300s, and then cooled to room temperature at a cooling rate of 5-50°C / s.
[0019] In the method for improving the coercivity of samarium cobalt magnets, the sixth step involves two aging processes. The first aging process is carried out at a temperature of 810–900°C for 5–40 hours. Then, the temperature is lowered to 400°C at a cooling rate of ~0.7°C / min for a second aging process, which lasts for 1–20 hours. Finally, the magnet is cooled to room temperature to obtain the final magnet.
[0020] A samarium cobalt magnet is obtained by processing it to increase the coercivity of the samarium cobalt magnet.
[0021] Compared with the prior art, the beneficial effects of this disclosure are as follows:
[0022] This invention employs a rapid heating-short holding-rapid cooling process on the magnet before isothermal aging. By obtaining a high density of initial defects, the formation of subsequent SmCo5 precipitates is accelerated, significantly improving the coercivity of the samarium-cobalt magnet. The fabrication process of this invention is simple and short, effectively saving time and energy costs in magnet manufacturing. Therefore, this invention has broad market prospects. Furthermore, the samarium-cobalt magnet prepared by this invention exhibits high coercivity at room temperature, meeting the high stability requirements of magnets in current traction motors and navigation instruments, and is of great significance for the development of related magnetic devices. Attached Figure Description
[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.
[0024] In the attached diagram:
[0025] Figure 1 This is a schematic diagram of a rapid heating and cooling pretreatment method for improving the coercivity of a samarium-cobalt magnet according to an embodiment of this disclosure;
[0026] Figure 2 The Sm(Co) obtained in Example 1 with and without rapid heating and cooling pretreatment are examples of this. bal. Fe 0.305 Cu 0.07 Zr 0.04 ) 7.6 Comparison of hysteresis loops of magnets;
[0027] Figure 3 The Sm(Co) obtained in Example 1 with and without rapid heating and cooling pretreatment are shown. bal. Fe 0.305 Cu 0.07 Zr 0.04 ) 7.6 The positron annihilation spectrum of the initial magnet.
[0028] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation
[0029] Specific embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
[0030] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions of preferred embodiments of this disclosure are for the purpose of implementing the general principles of the specification and are not intended to limit the scope of this disclosure. The scope of protection of this disclosure is determined by the appended claims.
[0031] To facilitate understanding of the embodiments of this disclosure, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific examples. The accompanying drawings do not constitute a limitation on the embodiments of this invention.
[0032] To better understand, such as Figures 1 to 3 As shown, a method for improving the coercivity of samarium-cobalt magnets includes the following steps:
[0033] The first step involves melting the metal raw materials in a vacuum induction furnace according to a specific ratio to obtain an ingot. The ingot contains an atomic percentage of Sm(Co). bal Fe u Cu v Zr w ) z Samarium cobalt magnets, 0.10≤u≤0.35, 0.04≤v≤0.10, 0.01≤w≤0.08, 7≤z≤8;
[0034] The second step is to crush the ingot to obtain alloy powder.
[0035] The third step is to mold the alloy powder in a magnetic field, and then cold isostatically press it to obtain a green blank.
[0036] The fourth step is to sinter the green blank and perform a solution treatment to obtain a sintered magnet;
[0037] The fifth step involves heating the sintered magnet in a heat treatment furnace from room temperature to 400-800°C at a heating rate of 50-150°C / s, holding it at that temperature for 30-300s, and then cooling it down to room temperature at a cooling rate of 5-50°C / s.
[0038] The sixth step involves aging the sintered magnet and then cooling it to room temperature to obtain a samarium cobalt magnet. The aging process consists of two steps: the first step involves aging at a temperature of 810–900°C for 5–40 hours, followed by a second aging process at a temperature of 0.7°C / min to 400°C for 1–20 hours, and then cooling to room temperature to obtain the samarium cobalt magnet.
[0039] In a preferred embodiment of the method for improving the coercivity of samarium-cobalt magnets, in the first step, the samarium-cobalt magnet is prepared with an atomic percentage of Sm(Co). bal Fe u Cu v Zr w ) z Where 0.10≤u≤0.35, 0.04≤v≤0.10, 0.01≤w≤0.08, and 7≤z≤8.
[0040] In a preferred embodiment of the method for improving the coercivity of samarium-cobalt magnets, in the second step, the particle size of the alloy powder is 4~6 μm.
[0041] In a preferred embodiment of the method for improving the coercivity of samarium-cobalt magnets, in the third step, the molding pressure is ~150 MPa, the magnetic field strength is >1.0T, and the cold isostatic pressing pressure is 200~300 MPa.
[0042] In a preferred embodiment of the method for improving the coercivity of samarium-cobalt magnets, in the fourth step, the sintering temperature is 1190–1220°C, the sintering time is 0.5–3 h, the solution treatment temperature is 1130–1190°C, and the sintering time is 1–8 h.
[0043] In a preferred embodiment of the method for improving the coercivity of a samarium-cobalt magnet, in the fifth step, the magnet is heated from room temperature to 600-900°C in a rapid heat treatment furnace at a heating rate of 50-150°C / s, held at that temperature for 30-300s, and then cooled to room temperature at a cooling rate of 5-50°C / s.
[0044] In a preferred embodiment of the method for improving the coercivity of samarium cobalt magnets, the sixth step involves two aging processes. The first aging process is carried out at a temperature of 810–900°C for 5–40 hours. Then, the temperature is lowered to 400°C at a cooling rate of ~0.7°C / min for a second aging process, which lasts for 1–20 hours. Finally, the magnet is cooled to room temperature to obtain the final magnet.
[0045] In the method for improving the coercivity of samarium cobalt magnets, in the fourth step, the sintering temperature is 1190-1220℃, the sintering time is 0.5-3h, the solution treatment temperature is 1130-1190℃, and the sintering time is 1-8h.
[0046] In the method for improving the coercivity of samarium-cobalt magnets, the ingot comprises Sm(Co) atoms. bal. Fe 0.305 Cu 0.07 Zr 0.04 ) 7.6Samarium cobalt magnets.
[0047] In the method for improving the coercivity of samarium cobalt magnets, the green blank is sintered at 1190°C for 0.5 h; then it is solution treated at 1150°C for 4 h and cooled to room temperature to obtain a solid solution magnet.
[0048] In the method for improving the coercivity of a samarium-cobalt magnet, the solid solution magnet is placed in a heat treatment furnace and heated from room temperature to 780°C at a heating rate of 50°C / s under an argon atmosphere, held at that temperature for 3 minutes, and then cooled to room temperature at a cooling rate of 5-50°C / s.
[0049] In the method for improving the coercivity of samarium cobalt magnets, the solid solution magnet is placed in a muffle furnace and heated to 810°C. After holding at this temperature for 15 hours, it is cooled to 400°C at a cooling rate of 0.7°C / min and held at this temperature for 1 hour. Subsequently, it is cooled to room temperature with the furnace to obtain the samarium cobalt magnet.
[0050] In the method for improving the coercivity of samarium cobalt magnets, the coercivity of samarium cobalt magnets... H cj Not less than 30.34kOe, knee point field H k Not less than 19.20 kGOe.
[0051] The samarium-cobalt magnet obtained by the aforementioned preparation method.
[0052] Example 1
[0053] In this embodiment, the samarium-cobalt magnet has the chemical formula Sm(Co) bal. Fe 0.305 Cu 0.07 Zr 0.04 ) 7.6 Specifically, it includes the following steps:
[0054] 1. Metal raw materials are placed in a vacuum induction furnace according to the specified proportions to obtain ingots;
[0055] 2. The ingot is mechanically crushed, then subjected to medium crushing and air jet milling to obtain alloy powder with a particle size of 4~6 μm;
[0056] 3. The alloy powder is molded in a magnetic field of >1.0T at ~150 MPa, and then cold isostatically pressed at 200~300 MPa to obtain a green blank;
[0057] 4. The obtained green body was sintered at 1190℃ for 0.5h; then it was solution treated at 1150℃ for 4h and cooled to room temperature to obtain a solid solution magnet;
[0058] 5. Place the solution-treated magnet in a rapid heat treatment furnace and heat it to 780°C at a rate of ~50°C / s under an argon atmosphere. Hold it at that temperature for 3 minutes, and then cool it to room temperature at a rate of ~5-50°C / s.
[0059] 6. The magnet obtained by rapid heat treatment is placed in a muffle furnace and heated to 810℃. After holding at this temperature for 15 hours, it is cooled to 400℃ at a cooling rate of 0.7℃ / min and held at this temperature for 1 hour. Then, it is cooled to room temperature with the furnace to obtain the final magnet.
[0060] 7. Perform performance tests on the final-state magnets. Compared with magnets of the same composition that have undergone the same heat treatment process without rapid heat treatment, the coercivity of the magnets after rapid heating and cooling pretreatment is [increased / decreased]. H cj From 26.20 kOe to 30.34 kOe, knee point field H k It increased from 14.43 kOe to 19.20 kOe.
[0061] Example 2
[0062] This embodiment is performed in basically the same manner as Embodiment 1, except that the rapid heating and cooling pretreatment temperature in step 5 is 760℃. Coercivity of the magnet. H cj From 26.20 kOe to 28.37 kOe, knee point field H k It increased from 14.43 kOe to 17.41 kGOe.
[0063] Example 3
[0064] This embodiment is carried out in basically the same manner as Embodiment 1, except that the magnet composition is Sm(Co) bal. Fe 0.22 Cu 0.07 Zr 0.03 ) 7.4 In step 4, the sintering temperature is 1220℃, and the solution treatment temperature is 1170℃. The coercivity of the magnet. H cj From 32.20 kOe to 34.76 kOe, knee point field H k It increased from 21.43 kOe to 24.80 kOe.
[0065] Example 4
[0066] This embodiment is carried out in basically the same manner as Embodiment 1, except that the magnet composition is Sm(Co) bal. Fe 0.22 Cu0.07 Zr 0.03 ) 7.4 In step 4, the sintering temperature is 1220℃ and the solution treatment temperature is 1170℃. In step 6, the first-stage aging temperature is 850℃, and the magnet is directly cooled to room temperature without undergoing a second-stage aging process. The coercivity of the magnet... H cj From 29.37 kOe to 31.28 kOe, knee point field H k It increased from 19.45 kOe to 21.44 kGOe.
[0067] Although the embodiments of this disclosure have been described above in conjunction with the accompanying drawings, this disclosure is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of this disclosure, and all of these are within the scope of protection of this invention.
Claims
1. A method for improving the coercivity of samarium-cobalt magnets, characterized in that, Includes the following steps: The first step involves melting the metal raw materials in a vacuum induction furnace according to a specific ratio to obtain an ingot. The ingot contains an atomic percentage of Sm(Co). bal Fe u Cu v Zr w ) z Samarium cobalt magnets, 0.10≤u≤0.35, 0.04≤v≤0.10, 0.01≤w≤0.08, 7≤z≤8; The second step is to crush the ingot to obtain alloy powder. The third step is to mold the alloy powder in a magnetic field, and then cold isostatically press it to obtain a green blank. The fourth step is to sinter the green blank and perform a solution treatment to obtain a sintered magnet; The fifth step involves heating the sintered magnet in a heat treatment furnace from room temperature to 400-800°C at a heating rate of 50-150°C / s, holding it at that temperature for 30-300s, and then cooling it down to room temperature at a cooling rate of 5-50°C / s. The sixth step involves aging the sintered magnet and then cooling it to room temperature to obtain a samarium cobalt magnet. The aging process consists of two steps: the first step involves aging at a temperature of 810–900°C for 5–40 hours, followed by a second aging process at a temperature of 0.7°C / min to 400°C for 1–20 hours, and then cooling to room temperature to obtain the samarium cobalt magnet.
2. The method for improving the coercivity of samarium-cobalt magnets according to claim 1, characterized in that, In the second step, the alloy powder particle size is 4~6 μm.
3. The method for improving the coercivity of a samarium-cobalt magnet according to claim 1, characterized in that, In the third step, the molding pressure is 150 MPa, the magnetic field strength is >1.0T, and the cold isostatic pressing pressure is 200~300 MPa.
4. The method for improving the coercivity of a samarium-cobalt magnet according to claim 1, characterized in that, In the fourth step, the sintering temperature is 1190~1220℃, the sintering time is 0.5~3h, the solution treatment temperature is 1130~1190℃, and the sintering time is 1~8h.
5. The method for improving the coercivity of a samarium-cobalt magnet according to claim 1, characterized in that, In the fifth step, the magnet is heated from room temperature to 600-800℃ in a rapid heat treatment furnace at a heating rate of 50-150℃ / s, held at that temperature for 30-300s, and then cooled to room temperature at a cooling rate of 5-50℃ / s.
6. A samarium-cobalt magnet, characterized in that, It is prepared by the method according to any one of claims 1 to 5.