Double gradient aging treatment method and preparation method for high performance sintered samarium cobalt permanent magnet

Abstract

The present invention relates to a dual-gradient aging treatment method and a preparation method for high-performance sintered samarium cobalt permanent magnets, belonging to the technical field of rare earth magnetic materials, and solving the problem in the prior art that high-iron samarium cobalt permanent magnets are limited by at least one of the factors of squareness and / or maximum magnetic energy product, which leads to difficulty in improving comprehensive magnetic properties. A dual-gradient aging treatment method for high-performance sintered samarium cobalt permanent magnets comprises the following steps: pre-gradient aging, isothermal aging, and post-gradient aging. The present invention realizes that the squareness and maximum magnetic energy product of the magnet are improved at the same time, and the magnet exhibits more excellent comprehensive magnetic properties.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth magnetic materials, and in particular to a double-gradient aging treatment method and a preparation method of a high-performance sintered samarium-cobalt permanent magnet. Background Art

[0002] 2:17 Sm-Co permanent magnet materials are widely used in aerospace, transportation, communications and many other fields due to their advantages such as high saturation magnetization, high Curie temperature and good temperature stability. In recent years, in high-end motor applications such as hybrid vehicles and high-speed railways, the operating temperature of the magnet is required to be close to 200°C. At present, the magnetic energy product and coercive force of high-performance 2:17 Sm-Co permanent magnet materials have exceeded those of Nd-Fe-B permanent magnet materials at around 200°C, providing a more stable magnetic field for the magnetic circuit and have been widely used. It is of great significance to develop high-performance 2:17 Sm-Co permanent magnet materials with high intrinsic coercive force.

[0003] For high-performance 2:17 Sm-Co permanent magnet materials, increasing the Fe content and reducing the content of non-ferromagnetic elements Cu and Zr has always been one of the effective methods to increase the maximum magnetic energy product of 2:17 Sm-Co magnets. However, when the Fe content exceeds 19wt%, since the 1:7H phase becomes more unstable, a 2:17R phase will be formed during solution heat treatment, and this 2:17R phase will exist in the matrix in the form of short-range ordered microtwins. This 2:17R microtwin formed during the solution process will hinder the formation of the cell wall phase during the subsequent aging process. In addition, when the Fe content in the magnet is too high, there will be defects such as stacking faults and dislocations inside the magnet, and Sm will also be generated at the grain boundaries of the magnet. n+1 Co 5n-1 The existence of these impurities and defects will further inhibit the formation of the cell wall phase, significantly deteriorate the squareness and magnetic energy product of the high-iron 2:17 type samarium-cobalt magnet, and result in poor comprehensive magnetic properties. Summary of the invention

[0004] In view of the above analysis, the present invention aims to provide a dual gradient aging treatment method and a preparation method for high-performance sintered samarium cobalt permanent magnets, so as to solve the problem in the prior art that high iron samarium cobalt permanent magnets are limited by at least one of the squareness and / or maximum magnetic energy product, which makes it difficult to improve the comprehensive magnetic properties.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] The present invention provides a double gradient aging treatment method for a high performance sintered samarium cobalt permanent magnet, the double gradient aging treatment method comprising the following steps:

[0007] (1) Pre-gradient aging: the samarium-cobalt green body is heated to T1 and then subjected to heat preservation treatment, then heated to T2 and then subjected to heat preservation treatment, and then heated to T3 and then subjected to heat preservation treatment;

[0008] (2) Isothermal aging: The samarium-cobalt green body after T3 insulation treatment is heated to T4 and then subjected to insulation treatment;

[0009] (3) Post-gradient aging: the samarium-cobalt green body after T4 insulation treatment is cooled to T5 and then subjected to insulation treatment, then cooled to T6 and then subjected to insulation treatment, then cooled to T7 and then subjected to insulation treatment, then cooled to T8 and then subjected to insulation treatment, and finally cooled to room temperature;

[0010] Among them, T1 is 200~300℃, T2=T1+200℃~T1+300℃, T3=T2+150℃~T1+250℃, T4 is 790~870℃, and T3<T4; T5=T4-140℃~T4-120℃, T6=T4-240℃~T4-220℃, T7=T4-340℃~T4-320℃, T8 is 300~400℃, and T7>T8.

[0011] Furthermore, it has at least one of the following characteristics:

[0012] (1) T2 is 450~550℃;

[0013] (2) T3 is 650~750℃.

[0014] Furthermore, it has at least one of the following characteristics:

[0015] (1) After the temperature is raised to T1, the heat preservation time t1 is 0.5-3h;

[0016] (2) After the temperature is raised to T2, during the heat preservation treatment, the heat preservation time t2 is 0.5-3h;

[0017] (3) After the temperature is raised to T3, the heat preservation time t3 is 0.5-3h;

[0018] (4) After the temperature is raised to T4, the temperature is kept warm for a period of 5-24 hours;

[0019] (5) After the temperature is lowered to T5, the temperature is kept warm for a period of 1-3 hours;

[0020] (6) After the temperature is lowered to T6, the heat preservation time t6 is 1-3h;

[0021] (7) After the temperature is lowered to T7, the heat preservation time t7 is 1-3h;

[0022] (8) After the temperature is lowered to T8, the heat preservation time t8 is 1-3h.

[0023] Furthermore, the insulation time t1 and / or t2 and / or t3 is 0.5-1h; and / or the insulation time t4 is 6-15h.

[0024] Further, the insulation time t5 is 1-1.3h; and / or, the insulation time t6 is 1-1.5h; and / or, the insulation time t7 is 1-2h; and / or, the insulation time t8 is 1-1.5h.

[0025] Furthermore, it has at least one of the following characteristics:

[0026] (1) The temperature is raised to T1, and the rate of the temperature rise is 0.5-10°C / min;

[0027] (2) The temperature is raised to T2, and the rate of the temperature increase is R2 of 0.5-10°C / min;

[0028] (3) The temperature is raised to T3, and the rate of the temperature increase is 0.5-10°C / min;

[0029] (4) The temperature is lowered to T5, and the rate of the temperature reduction R5 is 0.5-6°C / min;

[0030] (5) The temperature is lowered to T6, and the rate of the temperature reduction R6 is 0.5-6°C / min;

[0031] (6) The temperature is lowered to T7, and the rate of the temperature reduction R7 is 0.5-6°C / min;

[0032] (7) The temperature is lowered to T8, and the rate of the temperature reduction R8 is 0.5-6°C / min.

[0033] Furthermore, the heating rate R1 and / or R2 and / or R3 is 0.5-2°C / min; and / or the cooling rate R5 and / or R6 and / or R7 and / or R8 is 4-6°C / min.

[0034] Furthermore, the samarium cobalt green body is prepared from the following raw materials in weight percentage: Sm: 24.5-26.0%, Fe: 19-20%, Cu: 5-7%, Zr: 2.5-3.5%, and the balance is Co.

[0035] The present invention also provides a method for preparing a high-performance sintered samarium cobalt permanent magnet, which comprises the following steps: subjecting samarium cobalt magnet alloy powder to molding, sintering, solid solution and aging treatment; wherein the aging treatment adopts the double-gradient aging treatment method as described above.

[0036] Furthermore, the main steps of molding the samarium-cobalt magnet alloy powder include: alloy smelting, powder making, and mold pressing; wherein the alloy smelting includes: using one or more of a vacuum arc melting furnace, a micro-positive pressure induction melting furnace, and a vacuum induction melting rapid solidification furnace to smelt the metal raw material to obtain an alloy ingot;

[0037] The powder making comprises: coarsely crushing and grinding the alloy ingot to make magnetic powder of 2.5-4.5 μm;

[0038] The compression molding comprises: firstly subjecting the magnetic powder to magnetic field orientation molding, and then cold isostatic pressing to obtain a magnet green body;

[0039] The main steps of sintering and solid solution treatment include: sintering the magnet green body at 1180-1235° C. for 1.0-2.5 hours, and then performing solid solution treatment at a solid solution temperature of 1125-1185° C. for 8-24 hours to obtain a samarium-cobalt green body.

[0040] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0041] (1) The present invention provides an aging treatment method for samarium cobalt permanent magnets, which adopts a double gradient aging process system. Through three-level pre-gradient aging treatment, the phase transformation process from 2:17H to 2:17R of the magnet and the slip of dislocations are promoted, and the nucleation rate of the 1:5H cell wall phase is increased, and more 1:5H nanoprecipitate phases are generated before the 1:7H phase decomposes. In the subsequent isothermal aging process, the cell wall phase will take this as the core and begin to grow. Compared with the magnet without pre-gradient aging, the cellular structure of the magnet is more continuous, and there are more 1:5H cell wall phases inside the magnet, which effectively reduces the weak pinning area inside the magnet. Through the four-level post-gradient aging treatment, elements such as Cu and Fe are fully diffused and enter the cell wall phase and the intracellular phase respectively, so that the squareness and maximum magnetic energy product of the magnet are improved at the same time, and the magnet exhibits more excellent comprehensive magnetic properties.

[0042] (2) In some preferred embodiments, by optimizing the key parameters of the three-stage pre-gradient aging treatment, such as temperature, holding time, and heating rate, the squareness and maximum magnetic energy product of the magnet can be significantly improved, thereby more effectively improving the comprehensive magnetic properties of the magnet.

[0043] (3) In some preferred embodiments, by further optimizing the key process parameters of isothermal aging, such as temperature and holding time, a better synergistic effect can be achieved, ensuring that the 1:5H cell wall phase precipitated by the three-level pre-gradient aging can start to grow with this as the core and reach an ideal microscopic size. This helps to maximize the strong pinning effect of the 1:5H cell wall on the main phase 2:17R phase magnetic domain wall, thereby improving the squareness and maximum magnetic energy product of the magnet, and further effectively improving the comprehensive magnetic properties of the magnet.

[0044] (4) In some preferred embodiments, by further optimizing the key process parameters of the four-stage post-gradient aging, such as temperature, holding time, and cooling rate, a better synergistic effect can be achieved. This optimization ensures that elements such as Cu and Fe are fully diffused and enter the 1:5H cell wall phase and intracellular phase that have been precipitated by the three-stage pre-gradient aging and appropriately grown by isothermal aging, respectively, which can better improve the microstructure of the magnet, strengthen the pinning effect of the magnetic domain wall, and ultimately achieve a further improvement in the squareness and maximum magnetic energy product of the magnet.

[0045] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be achieved and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. In the entire drawings, the same reference symbols represent the same components;

[0047] Figure 1 Schematic diagram of the double gradient aging process in an embodiment of the present invention. DETAILED DESCRIPTION

[0048] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0049] As a precipitation hardening permanent magnet, the strong pinning effect of the cell wall 1:5H phase on the main phase 2:17R phase domain wall of the sintered Sm-Co magnet is the source of its high coercivity Hcj. Therefore, how to promote the precipitation of the 1:5H cell wall phase of the high-iron 2:17 type Sm-Co magnet and improve the microstructure of the magnet is the key to improving the squareness and maximum magnetic energy product of the high-iron samarium cobalt magnet and improving the comprehensive magnetic properties. When studying the microstructural evolution of Sm-Co sintered magnets, the inventors found that aging treatment is one of the key heat treatment processes. This process involves complex atomic diffusion and phase transformation phenomena, which significantly affect the final microstructure and magnetic properties of the magnet. However, the traditional aging treatment method currently used for sintered Sm-Co magnets is mainly isothermal aging combined with subsequent graded cooling or slow cooling, but it has limited effect on improving the magnetic properties of the magnet and has not brought obvious improvements.

[0050] Based on this, in a first aspect, the present invention provides a dual-gradient aging treatment method for a high-performance sintered samarium-cobalt permanent magnet, the dual-gradient aging treatment method comprising the following steps:

[0051] (1) Pre-gradient time effect:

[0052] First-stage pre-gradient: the samarium-cobalt green body is heated to T1 and then subjected to heat preservation treatment;

[0053] Secondary pre-gradient: then the temperature is raised to T2 and then kept warm;

[0054] Level 3 front gradient: heat up to T3 and then keep warm;

[0055] (2) Isothermal aging: The samarium-cobalt green body after T3 insulation treatment is heated to T4 and then subjected to insulation treatment;

[0056] (3) Post-gradient aging:

[0057] First-stage post-gradient: Cool the samarium-cobalt green body after T4 heat preservation to T5 and then heat preservation.

[0058] Secondary post-gradient: then cool down to T6 and keep warm.

[0059] Gradient after the third level: cool down to T7 and then keep warm.

[0060] Level 4 post-gradient: cool down to T8 and then keep warm, and finally cool to room temperature;

[0061] Among them, T1 is 200~300℃, T2=T1+200℃~T1+300℃, T3=T2+150℃~T1+250℃, T4 is 790~870℃, and T3<T4; T5=T4-140℃~T4-120℃, T6=T4-240℃~T4-220℃, T7=T4-340℃~T4-320℃, T8 is 300~400℃, and T7>T8.

[0062] Compared with the prior art, the present invention provides an aging treatment method for samarium cobalt permanent magnets, adopts a dual gradient aging process system, and promotes the phase transformation process of the magnet from 2:17H to 2:17R and the slip of dislocations through three-level pre-gradient aging treatment, and increases the nucleation rate of the 1:5H cell wall phase, and produces more 1:5H nanoprecipitate phases before the 1:7H phase decomposes. In the subsequent isothermal aging process, the cell wall phase will take this as the core and begin to grow. Compared with the magnet without the pre-gradient aging, the cellular structure of the magnet is more continuous, and the 1:5H cell wall phase inside the magnet is also more, which effectively reduces the weak pinning area inside the magnet. Through the four-level post-gradient aging treatment, elements such as Cu and Fe are fully diffused and enter the cell wall phase and the intracellular phase respectively, so that the squareness and maximum magnetic energy product of the magnet are improved at the same time, and the magnet exhibits more excellent comprehensive magnetic properties.

[0063] It should be noted that each temperature level in the dual gradient aging treatment provided by the present invention plays a specific role. They cooperate with each other to achieve the improvement of squareness and maximum magnetic energy product by promoting phase transformation, optimizing microstructure and element distribution. If the temperature setting of any link is improper, it may affect the final magnetic performance.

[0064] In particular, the temperatures of each stage in the three-stage pre-gradient aging treatment have a synergistic effect because the temperature setting of each stage is to achieve specific atomic diffusion and phase change effects. These effects are cumulative and interdependent, specifically:

[0065] First stage temperature: start and accelerate the phase transition process from 2:17H to 2:17R, while promoting the nucleation of 1:5H cell wall phase, laying a solid foundation for the subsequent stages;

[0066] Second stage temperature: on the basis of maintaining the existing transformation, further promote the phase transformation process and enhance the precipitation of 1:5H nano-precipitation phase to form a specific microstructure that is beneficial to improving magnetic properties;

[0067] The third stage temperature ensures that all expected phase transformations are completed and maximizes the desired structural characteristics (such as the amount of 1:5H cell wall phase) while preparing to enter the isothermal aging stage.

[0068] This graded temperature increase strategy not only promotes the phase transformation, atomic diffusion, nucleation of 1:5H cell wall phase and precipitation of nanoprecipitate phase required in each stage, but also ensures that these changes are cumulative and interdependent. Each temperature level is to achieve a specific effect, which in turn provides the necessary conditions for the next level of treatment. Therefore, if the number of levels of the previous gradient is insufficient or the temperature setting of any level is inappropriate, the corresponding phase transformation and precipitation of 1:5H cell wall phase cannot be effectively triggered or controlled, thereby affecting the effect of the entire aging treatment, and the predetermined microstructure adjustment goal cannot be achieved, which ultimately leads to the failure to improve the squareness and maximum magnetic energy product of the magnet as it should be.

[0069] Illustratively, T1 is 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, or 290°C.

[0070] Illustratively, T4 is 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C.

[0071] Illustratively, T2=T1+220°C~T1+280°C, T2=T1+230°C~T1+270°C, T2=T1+240°C~T1+260°C.

[0072] Illustratively, T3=T2+160℃~T1+240℃, T3=T2+170℃~T1+230℃, T3=T2+180℃~T2+220℃, T3=T2+190℃~T2+210℃.

[0073] Exemplarily, T8=320°C, 340°C, 360°C, 380°C.

[0074] Illustratively, T5=T4-135°C~T4-125°C, T6=T4-235°C~T4-225°C, T7=T4-335°C~T4-325°C.

[0075] In some preferred embodiments, by optimizing the key parameters of the three-stage pre-gradient aging process, such as temperature, holding time, and heating rate, not only can the squareness and maximum magnetic energy product of the magnet be significantly improved, thereby more effectively improving the comprehensive magnetic properties of the magnet, but also an optimal balance between efficiency and cost can be achieved. Specifically:

[0076] (a) First-stage pre-gradient: the samarium-cobalt green body is heated to T1 and then kept warm;

[0077] Preferably, in the heat preservation treatment after the temperature is raised to T1, the heat preservation time t1 is 0.5-3h, and / or, in the temperature is raised to T1, the temperature rise rate R1 is 0.5-10°C / min.

[0078] Exemplarily, the insulation time t1 is 0.8h, 1h, 1.2h, 1.5h, 2h, and 2.5h.

[0079] Exemplarily, the heating rate R1 is 0.8°C / min, 1.0°C / min, 1.2°C / min, 1.5°C / min, 1.8°C / min, 2.5°C / min, 3.0°C / min, 5.0°C / min, 7.0°C / min, and 9.0°C / min.

[0080] More preferably, during the heat preservation treatment after the temperature is increased to T1, T1 is 210-230°C, and / or the heat preservation time t1 is 0.5-1h, and / or during the temperature increase to T1, the temperature increase rate R1 is 0.5-2°C / min.

[0081] (b) Secondary pre-gradient: then the temperature is raised to T2 and then kept warm;

[0082] Preferably, during the heat preservation treatment after the temperature is raised to T2, T2 is 450-550°C; and / or the heat preservation time t2 is 0.5-3h; and / or, during the temperature is raised to T2, the temperature rise rate R2 is 0.5-10°C / min.

[0083] Illustratively, T2 is 460°C, 470°C, 490°C, 500°C, 510°C, 520°C, 530°C, or 540°C.

[0084] Exemplarily, the insulation time t2 is 0.8h, 1h, 1.2h, 1.5h, 2h, and 2.5h.

[0085] Exemplarily, the heating rate R2 is 0.8°C / min, 1.0°C / min, 1.2°C / min, 1.5°C / min, 1.8°C / min, 2.5°C / min, 3.0°C / min, 5.0°C / min, 7.0°C / min, and 9.0°C / min.

[0086] More preferably, during the heat preservation treatment after the temperature is raised to T2, T2 is 450-480°C, and / or the heat preservation time t2 is 0.5-1h; and / or during the temperature is raised to T2, the temperature rise rate R2 is 0.5-2°C / min.

[0087] (c) Third-stage pre-gradient: heating to T3 and then heat preservation;

[0088] Preferably, in the heat preservation treatment after heating to T3, T3 is 650-750°C; and / or, the heat preservation time t3 is 0.5-3h, and / or, in the heating to T3, the heating rate R3 is 0.5-10°C / min.

[0089] Illustratively, T3 is 660°C, 670°C, 690°C, 700°C, 710°C, 720°C, 730°C, or 740°C.

[0090] Exemplarily, the insulation time t3 is 0.8h, 1h, 1.2h, 1.5h, 2h, and 2.5h.

[0091] Exemplarily, the heating rate R3 is 0.8°C / min, 1.0°C / min, 1.2°C / min, 1.5°C / min, 1.8°C / min, 2.5°C / min, 3.0°C / min, 5.0°C / min, 7.0°C / min, and 9.0°C / min.

[0092] More preferably, in the heat preservation treatment after the temperature is increased to T3, T3 is 650-680°C, and / or the heat preservation time t3 is 0.5-1h, and / or, in the temperature increase to T3, the temperature increase rate R3 is 0.5-2°C / min.

[0093] By further optimizing the key process parameters of the three-stage pre-gradient aging treatment, such as temperature, holding time, and heating rate, better synergy can be achieved, which can not only enable the magnet to obtain the best magnetic properties, but also find the best balance between efficiency and cost. This optimization method is specifically reflected in the following aspects:

[0094] A. Precise temperature control: By accurately setting the temperature of each stage, we can ensure the best conditions for phase transition (such as 2:17H to 2:17R transition) and nucleation of 1:5H cell wall phase and precipitation of nano-precipitate phase, while avoiding unnecessary side reactions. This helps to form an ideal microstructure and lay a solid foundation for subsequent performance improvement.

[0095] B. Optimization of holding time: By optimizing the holding time, sufficient phase transformation and organizational structure evolution and the nucleation and precipitation of the 1:5H cell wall phase can be ensured without causing waste of resources or extending the production cycle.

[0096] C. Scientific planning of heating rate: Rationally design the heating rate to ensure smooth phase transformation at each stage and the nucleation and precipitation of the favorable 1:5H cell wall phase, while reducing heat treatment time and improving production efficiency. Rapid but controllable heating can reduce energy consumption, shorten production cycle, and thus reduce costs.

[0097] In some preferred embodiments, by further optimizing the key process parameters of isothermal aging, such as temperature and holding time, better synergy can be achieved to ensure that the 1:5H cell wall phase precipitated by the three-level pre-gradient aging can start to grow with this as the core and reach the ideal microscopic size. This helps to maximize the strong pinning effect of the 1:5H cell wall on the main phase 2:17R phase magnetic domain wall, thereby significantly improving the squareness and maximum magnetic energy product of the magnet, and thus more effectively improving the comprehensive magnetic properties of the magnet. At the same time, this optimization can also achieve the best balance between efficiency and cost. Specifically:

[0098] (2) Isothermal aging: Heat up to T4 and then keep warm;

[0099] Preferably, during the heat preservation treatment after the temperature is raised to T4, the heat preservation time t4 is 5-24h; and / or, during the temperature is raised to T4, the temperature rise rate R4 is 5-8°C / min.

[0100] Exemplarily, the insulation time t4 is 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 16h, 18h, 20h, or 22h.

[0101] Exemplarily, the heating rate R4 is 5.5°C / min, 6.0°C / min, 6.8°C / min, 7.0°C / min, and 7.3°C / min.

[0102] More preferably, in the heat preservation treatment after the temperature is raised to T4, T4 is 790-820°C; and / or the heat preservation time t4 is 6-15h; and / or R4 is 6.5-7.5°C / min.

[0103] In some preferred embodiments, better synergy can be achieved by further optimizing the key process parameters of the four-stage post-gradient aging, such as temperature, holding time, cooling rate, etc. This optimization can better ensure that elements such as Cu and Fe are fully diffused, and enter the 1:5H cell wall phase and intracellular phase after precipitation by the three-stage pre-gradient aging and proper growth by isothermal aging, respectively. It can significantly improve the microstructure of the magnet, strengthen the pinning effect of the magnetic domain wall, and ultimately achieve a significant improvement in the squareness and maximum magnetic energy product of the magnet. At the same time, this optimization can also achieve the best balance between efficiency and cost. Specifically:

[0104] (d) First-stage post-gradient: cooling the samarium-cobalt green body after T4 heat preservation treatment to T5 and then heat preservation treatment;

[0105] Preferably, in the heat preservation treatment after cooling to T5, T5 is 650-750°C, and the heat preservation time t5 is 1-3h; and / or, in the cooling to T5, the cooling rate R5 is 0.5-6°C / min.

[0106] Illustratively, T5 is 660°C, 670°C, 690°C, 700°C, 710°C, 730°C, or 740°C.

[0107] Exemplarily, the insulation time t5 is 1.1h, 1.2h, 1.5h, 2h, and 2.5h.

[0108] Exemplarily, the cooling rate R5 is 1.0℃ / min, 1.5℃ / min, 2.0℃ / min, 2.5℃ / min, 3.0℃ / min, 3.5℃ / min, 4.2℃ / min, 4.5℃ / min, 4.7℃ / min, 5.0℃ / min, 5.2℃ / min, 5.5℃ / min, and 5.7℃ / min.

[0109] More preferably, during the heat preservation treatment after cooling to T5, T5 is 680-720°C; and / or, the heat preservation time t5 is 1-1.3h; and / or, during the cooling to T5, the cooling rate R5 is 4-6°C / min.

[0110] (e) Secondary post-gradient: then cooled to T6 and kept warm;

[0111] Preferably, in the heat preservation treatment after cooling to T6, T6 is 550-650°C; and / or, the heat preservation time t6 is 1-3h; and / or, in the cooling to T6, the cooling rate R6 is 0.5-6°C / min.

[0112] Illustratively, T6 is 560°C, 570°C, 590°C, 600°C, 610°C, 630°C, 640°C.

[0113] Exemplarily, the insulation time t6 is 1.1h, 1.2h, 1.3h, 1.4h, 2h, and 2.5h.

[0114] Exemplarily, the cooling rate R6 is 1.0℃ / min, 1.5℃ / min, 2.0℃ / min, 2.5℃ / min, 3.0℃ / min, 3.5℃ / min, 4.2℃ / min, 4.5℃ / min, 4.7℃ / min, 5.0℃ / min, 5.2℃ / min, 5.5℃ / min, and 5.7℃ / min.

[0115] More preferably, during the heat preservation treatment after cooling to T6, T6 is 580-620°C; and / or, the heat preservation time t6 is 1-1.5h; and / or, during the cooling to T6, the cooling rate R6 is 4-6°C / min.

[0116] (f) Gradient after the third stage: cooling down to T7 and then heat preservation treatment;

[0117] Preferably, in the heat preservation treatment after cooling to T7, T7 is 450-550°C; and / or, the heat preservation time t7 is 1-3h; and / or, in the cooling to T7, the cooling rate R7 is 0.5-6°C / min.

[0118] Illustratively, T7 is 460°C, 470°C, 490°C, 500°C, 510°C, 530°C, 540°C.

[0119] Exemplarily, the insulation time t7 is 1.2h, 1.4h, 1.6h, 1.8h, and 2.5h.

[0120] Exemplarily, the cooling rate R7 is 1.0℃ / min, 1.5℃ / min, 2.0℃ / min, 2.5℃ / min, 3.0℃ / min, 3.5℃ / min, 4.2℃ / min, 4.5℃ / min, 4.7℃ / min, 5.0℃ / min, 5.2℃ / min, 5.5℃ / min, and 5.7℃ / min.

[0121] More preferably, in the heat preservation treatment after cooling to T7, T7 is 480-520°C; and / or, the heat preservation time t7 is 1-2h; and / or, in the cooling to T7, the cooling rate R7 is 4-6°C / min.

[0122] (g) Four-stage post-gradient: cool down to T8, keep warm, and finally cool to room temperature;

[0123] Preferably, in the heat preservation treatment after cooling to T8, T8 is 350-400°C; and / or, the heat preservation time t8 is 1-3h; and / or, in the cooling to T8, the cooling rate R8 is 0.5-6°C / min.

[0124] Exemplarily, the insulation time t8 is 1.1h, 1.2h, 1.3h, 1.4h, 1.6h, 1.8h, 2.0h, and 2.5h.

[0125] Exemplarily, the cooling rate R8 is 1.0℃ / min, 1.5℃ / min, 2.0℃ / min, 2.5℃ / min, 3.0℃ / min, 3.5℃ / min, 4.2℃ / min, 4.5℃ / min, 4.7℃ / min, 5.0℃ / min, 5.2℃ / min, 5.5℃ / min, and 5.7℃ / min.

[0126] More preferably, in the heat preservation treatment after the temperature is reduced to T8, the heat preservation time t8 is 1-1.5h; and / or, in the temperature reduction to T8, the temperature reduction rate R8 is 4-6°C / min.

[0127] In some embodiments, the samarium cobalt green body is prepared from the following raw materials by weight percentage: Sm: 24.5-26.0%, Fe: 19-20%, Cu: 5-7%, Zr: 2.5-3.5%, and the balance is Co. This high iron content formula combined with the above-mentioned double gradient aging treatment process, compared with the traditional isothermal aging and / or step cooling method, makes the squareness and maximum magnetic energy product of the high iron samarium cobalt magnet significantly improved, for example: squareness ≥ 63%, at least increased by 30%-85%, maximum magnetic energy product ≥ 31MGOe, at least increased by 8%-20%, thereby significantly improving the comprehensive magnetic properties of the high iron samarium cobalt permanent magnet.

[0128] Based on the above dual gradient aging treatment method, the present invention also provides a method for preparing a high-performance sintered samarium cobalt permanent magnet, the method for preparing the samarium cobalt permanent magnet comprising the following steps:

[0129] S1, forming samarium cobalt magnet alloy powder;

[0130] S2, sintering and solution;

[0131] S3, aging treatment; the aging treatment adopts the double gradient aging treatment method as described above.

[0132] Specifically, the main steps of molding the samarium-cobalt magnet alloy powder in step S1 include:

[0133] S11, alloy smelting;

[0134] The smelting includes: using one or more of a vacuum arc melting furnace, a slightly positive pressure induction melting furnace, and a vacuum induction melting rapid solidification furnace to smelt the metal raw material to obtain an alloy ingot;

[0135] S12, flour making;

[0136] The powder making comprises: coarsely crushing and grinding the alloy ingot to make magnetic powder of 2.5-4.5 μm;

[0137] S13, compression molding;

[0138] The compression molding comprises: firstly subjecting magnetic powder to magnetic field orientation molding, and then cold isostatic pressing to obtain a magnet green body.

[0139] In some embodiments, in step S11, a vacuum arc melting furnace is used for smelting to obtain an alloy ingot, which specifically includes the following steps: weighing samarium, cobalt, iron, copper, zirconium and other raw materials according to the required composition ratio of samarium-cobalt permanent magnets, placing the prepared raw materials in a vacuum arc melting furnace, vacuuming with a mechanical pump or a diffusion pump, and then washing 3-5 times, gradually vacuuming to 10 -3Pa, and then filled with argon to carry out smelting under negative pressure of -0.05Mpa. To ensure the uniform composition of the ingot, increase the current and stir after smelting to form a molten metal pool. After cooling to form an ingot, turn it over and smelt it again. Repeat 3 to 5 times to obtain an alloy ingot with uniform composition.

[0140] In some embodiments, in step S11, a slightly positive pressure induction melting furnace is used for smelting to obtain an alloy ingot, which specifically includes the following steps: weighing samarium, cobalt, iron, copper, zirconium and other raw materials according to the required composition ratio of samarium cobalt permanent magnets, placing the prepared raw materials into a crucible of the slightly positive pressure induction melting furnace, covering the furnace cover, and starting a mechanical pump, a Rhodes pump and a diffusion pump to evacuate the vacuum until the vacuum degree reaches 2.5×10 -2 Pa, the material in the crucible is preheated (voltage: 0.5-1.0 kV) to remove moisture on the surface of the raw materials. At this time, the vacuum in the furnace will be reduced. When the vacuum is pumped back to 2.5×10 -2 Pa, stop vacuuming, open the charging valve, fill the furnace with argon until the pressure inside the furnace is -0.04MPa, then heat at a voltage of 25.0~30.0kV, melt until all raw materials are evenly dissolved, pour molten steel, and obtain alloy steel ingots. For example, alloy steel ingots with a thickness of 30mm.

[0141] In some embodiments, in step S11, a vacuum induction melting and rapid solidification furnace is used for smelting to obtain an alloy ingot, which specifically includes the following steps: weighing samarium, cobalt, iron, copper, zirconium and other raw materials according to the required composition ratio of samarium-cobalt permanent magnets, placing the prepared raw materials into a crucible of a vacuum induction melting and rapid solidification furnace, then closing the furnace door, and gradually evacuating the furnace to 10 -3 Pa and below, low power preheating to remove moisture and adsorbed impurities in the charge, at this time the vacuum degree drops, continue to evacuate to 10 -3 Pa and below, high-purity argon (purity exceeds 99.9%) is filled, medium-frequency current is sent to melt the charge, and then high-power heating is used to melt all the charge, and electromagnetic refining and stirring are performed for 3-5 minutes to make the alloy composition uniform. After reaching the set steel pouring temperature, the alloy liquid is poured through the tundish nozzle onto the water-cooled copper surface with a roller speed of 1.0-1.5m / s, and finally cooled to obtain a quick-setting sheet. For example, a 0.3mm quick-setting sheet.

[0142] In some embodiments, in step S12, the coarse crushing specifically includes: crushing the alloy steel ingot into samarium cobalt coarse particles with an average particle size of 200-300 μm by mechanical crushing.

[0143] In some embodiments, in step S12, the grinding specifically includes: processing the samarium cobalt coarse particles into samarium cobalt magnetic powder with an average particle size of 2.5-4.5 μm by means of a high-speed nitrogen airflow mill. The grinding pressure of the airflow mill is 0.5-0.8 MPa, and the air separation wheel speed is 2500-5000 r / min.

[0144] In some embodiments, in step S13, under the protection of inert gas, the magnetic powder obtained in step S12 is oriented in an orientation magnetic field, the intensity of the orientation magnetic field is 1.5~2.3T, and the pressure is 50-100Mpa; preferably, the intensity of the orientation magnetic field is 1.8~2.2T, and the pressure is 65-85Mpa. Exemplarily, the magnetic powder is subjected to magnetic field orientation molding in a closed nitrogen atmosphere compressor. After molded magnetic field orientation molding, a pressed embryo is obtained, and its density is 40%~50% of the theoretical density of the samarium cobalt permanent magnet.

[0145] In some embodiments, in step S13, the orientation-molded pressed embryo is subjected to cold isostatic pressing, and the pressure of the cold isostatic pressing is 200-300 MPa. Further, the pressure of the cold isostatic pressing is 200-260 MPa. Exemplarily, during cold isostatic pressing, the pressed embryo is completely immersed in hydraulic oil to ensure that the pressure on the pressed embryo in all directions is consistent, and the high orientation degree of the magnet during the molding process can be maintained. After cold isostatic pressing, a magnet green body is obtained, and its density is 60%-70% of the theoretical density of the samarium cobalt permanent magnet.

[0146] Specifically, the main steps of sintering and solid solution in step S2 include: sintering the magnet green body under the protection of inert gas, the sintering temperature is 1180-1235°C, and the sintering time is 1.0-2.5h; then performing solid solution treatment under the protection of inert gas, the solid solution treatment temperature is 1125-1185°C, and the solid solution treatment time is 8-24h to obtain the samarium cobalt green body.

[0147] In some preferred embodiments, the sintering temperature is 1210-1225° C., and the sintering time is 0.5-1.5 h.

[0148] In some preferred embodiments, the temperature of the solution treatment is 1130-1160° C., and the time of the solution treatment is 15-20 hours.

[0149] Preferably, in step S2, the inert gas protection uses high-purity argon gas, and the pressure of the argon gas is 0.01-0.05Mpa; that is, the sintering uses inert gas micro-positive pressure sintering, and the micro-positive pressure, that is, the pressure of the inert gas, is 0.01-0.05Mpa. Preferably, the pressure of the inert gas is 0.03-0.05Mpa.

[0150] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments and comparative examples.

[0151] Example 1

[0152] This embodiment provides a method for preparing a high-performance sintered samarium cobalt permanent magnet using a dual gradient aging system, comprising the following steps:

[0153] 1) Prepare the raw materials according to the designed formula. According to weight percentage, samarium cobalt permanent magnet is prepared from the following raw materials: Sm25.8%, Fe 20%, Cu 5.6%, Zr 2.5%, and the balance is Co;

[0154] 2) Use a micro-positive pressure induction melting furnace to prepare alloy ingots;

[0155] According to the composition ratio in 1), weigh samarium, cobalt, iron, copper, zirconium and other raw materials, put the prepared raw materials into the crucible of the micro-positive pressure induction melting furnace, cover the furnace cover, turn on the mechanical pump, Rhodes pump and diffusion pump to evacuate, and wait until the vacuum degree reaches 2.5×10 -2 Pa, the material in the crucible is preheated (voltage: 0.7 kV) to remove moisture on the surface of the raw materials. The vacuum in the furnace will be reduced at this time. When the vacuum is pumped back to 2.5×10 -2 Pa, stop vacuuming, open the charging valve, fill the furnace with argon until the pressure inside the furnace is negative pressure -0.04MPa, then heat at a voltage of 27.0kV, melt until all raw materials are evenly dissolved, pour molten steel to obtain alloy steel ingots;

[0156] 3) The powder after mechanical crushing of the alloy ingot is further crushed into magnetic powder with an average particle size of 2.5-4.5 μm by high-speed nitrogen gas jet mill;

[0157] 4) Then, the green magnet is oriented and formed in a closed nitrogen atmosphere press, and then cold isostatically pressed to obtain the green magnet; the magnetic field strength is 1.5T, the pressure is 50Mpa, and the cold isostatic pressing pressure is 300Mpa;

[0158] 5) Sintering under inert gas with a slight positive pressure of 0.015 MPa, a sintering temperature of 1195°C, and a sintering time of 1.5 h, followed by a solid solution treatment at a temperature of 1170°C and a solid solution treatment time of 10 h to obtain a solid solution magnet, i.e., a samarium cobalt green body;

[0159] 6) Double gradient aging: First-stage pre-gradient aging treatment: heat the sintered and solid-solutionized samarium-cobalt green body to 300°C at a heating rate of 10°C / min and keep it at that temperature for 3h;

[0160] Secondary pre-gradient aging treatment: heating to 550°C at a heating rate of 10°C / min and keeping warm for 3h;

[0161] Three-stage pre-gradient aging treatment: heating to 750℃ at a heating rate of 10℃ / min and keeping warm for 3h;

[0162] Isothermal aging: The samarium-cobalt green body after the three-stage pre-gradient aging treatment was heated to 790°C at a heating rate of 5°C / min and kept at this temperature for 24h;

[0163] Primary post-gradient aging treatment: the samarium-cobalt green body treated at 790°C for 24 hours was cooled to 700°C at a cooling rate of 0.5°C / min, and then kept at this temperature for 3 hours;

[0164] Secondary post-gradient aging treatment: cool down to 600℃ at a cooling rate of 0.5℃ / min, and then keep warm for 3h;

[0165] Three-stage post-gradient aging treatment: cool down to 500°C at a cooling rate of 0.5°C / min, and then keep warm for 3h;

[0166] Four-stage post-gradient aging treatment: cool down to 400°C at a cooling rate of 0.5°C / min, then keep warm for 3h, and finally cool to room temperature.

[0167] Example 2

[0168] The difference between this embodiment and embodiment 1 is isothermal aging, and the other steps and parameters are basically the same as those of embodiment 1. In this embodiment, isothermal aging: the samarium cobalt green body after the three-stage pre-gradient aging treatment is heated to 830° C. and kept at this temperature for 12 hours.

[0169] Example 3

[0170] The difference between this embodiment and embodiment 1 is isothermal aging, and the other steps and parameters are basically the same as those of embodiment 1. In this embodiment, isothermal aging: the samarium cobalt green body after the three-stage pre-gradient aging treatment is heated to 830° C. and kept at this temperature for 20 hours.

[0171] Example 4

[0172] The difference between this embodiment and embodiment 1 lies in the three-stage pre-gradient aging and isothermal aging, and the other steps and parameters are basically the same as those of embodiment 1. In this embodiment, the first-stage pre-gradient aging treatment: the samarium cobalt green body after sintering and solid solution is heated to 250°C at a heating rate of 5°C / min and kept at this temperature for 1.5h;

[0173] Secondary pre-gradient aging treatment: heating to 500°C at a heating rate of 5°C / min and keeping warm for 1.5h;

[0174] Three-stage pre-gradient aging treatment: heat to 700℃ at a heating rate of 5℃ / min and keep warm for 1.5h.

[0175] Isothermal aging: The samarium-cobalt green body after the three-stage pre-gradient aging treatment is heated to 870°C and kept at this temperature for 5 hours.

[0176] Example 5

[0177] The difference between this embodiment and embodiment 1 lies in the three-stage pre-gradient aging and isothermal aging, and the other steps and parameters are basically the same as those of embodiment 1. In this embodiment, the first-stage pre-gradient aging treatment: the samarium cobalt green body after sintering and solid solution is heated to 250°C at a heating rate of 5°C / min and kept at this temperature for 1.5h;

[0178] Secondary pre-gradient aging treatment: heating to 500°C at a heating rate of 5°C / min and keeping warm for 1.5h;

[0179] Three-stage pre-gradient aging treatment: heat to 700℃ at a heating rate of 5℃ / min and keep warm for 1.5h.

[0180] Isothermal aging: The samarium-cobalt green body after the three-stage pre-gradient aging treatment is heated to 790°C and kept at this temperature for 15 hours.

[0181] Example 6

[0182] The difference between this embodiment and embodiment 1 lies in the three-stage pre-gradient aging and isothermal aging, and the other steps and parameters are basically the same as those of embodiment 1. In this embodiment, the first-stage pre-gradient aging treatment: the samarium cobalt green body after sintering and solid solution is heated to 230°C at a heating rate of 2°C / min and kept at this temperature for 0.5h;

[0183] Secondary pre-gradient aging treatment: heating to 480°C at a heating rate of 2°C / min and keeping warm for 0.5h;

[0184] Three-stage pre-gradient aging treatment: heat to 680℃ at a heating rate of 2℃ / min and keep warm for 0.5h.

[0185] Isothermal aging: The samarium-cobalt green body after the three-stage pre-gradient aging treatment is heated to 790°C and kept at this temperature for 15 hours.

[0186] Example 7

[0187] The difference between this embodiment and embodiment 1 lies in the three-stage pre-gradient aging and isothermal aging, and the other steps and parameters are basically the same as those in embodiment 1. In this embodiment, the first-stage pre-gradient aging treatment: the samarium cobalt green body after sintering and solid solution is heated to 210°C at a heating rate of 0.5°C / min and kept at this temperature for 1h;

[0188] Secondary pre-gradient aging treatment: heating to 450°C at a heating rate of 0.5°C / min and keeping warm for 1h;

[0189] Three-stage pre-gradient aging treatment: heat to 650℃ at a heating rate of 0.5℃ / min and keep warm for 1h.

[0190] Isothermal aging: The samarium-cobalt green body after the three-stage pre-gradient aging treatment is heated to 820°C and kept at this temperature for 6 hours.

[0191] Example 8

[0192] The difference between this embodiment and embodiment 1 lies in the three-stage pre-gradient aging and isothermal aging, and the other steps and parameters are basically the same as those of embodiment 1. In this embodiment, the first-stage pre-gradient aging treatment: the samarium cobalt green body after sintering and solid solution is heated to 220°C at a heating rate of 1.5°C / min and kept at this temperature for 0.75h;

[0193] Secondary pre-gradient aging treatment: heating to 460°C at a heating rate of 1.5°C / min and keeping warm for 0.75h;

[0194] Three-stage pre-gradient aging treatment: heat to 660℃ at a heating rate of 1.5℃ / min and keep warm for 0.75h.

[0195] Isothermal aging: The samarium cobalt green body after the three-stage pre-gradient aging treatment is heated to 800°C and kept at this temperature for 12 hours.

[0196] Example 9

[0197] The difference between this embodiment and embodiment 1 lies in the three-stage pre-gradient aging and isothermal aging, and the other steps and parameters are basically the same as those of embodiment 1. In this embodiment, the first-stage pre-gradient aging treatment: the samarium cobalt green body after sintering and solid solution is heated to 220°C at a heating rate of 1.0°C / min and kept at this temperature for 0.75h;

[0198] Secondary pre-gradient aging treatment: heating to 470°C at a heating rate of 1.0°C / min and keeping warm for 0.75h;

[0199] Three-stage pre-gradient aging treatment: heat to 670℃ at a heating rate of 1.0℃ / min and keep warm for 0.75h.

[0200] Isothermal aging: The samarium-cobalt green body after the three-stage pre-gradient aging treatment is heated to 810°C and kept at this temperature for 9 hours.

[0201] Example 10

[0202] The difference between this embodiment and embodiment 9 is the four-stage post-gradient aging, and the other steps and parameters are basically the same as those of embodiment 9. In this embodiment, the first-stage post-gradient aging treatment: the samarium cobalt green body treated at 810°C for 9 hours is cooled to 700°C at a cooling rate of 6°C / min, and then kept at this temperature for 1.3 hours;

[0203] Secondary post-gradient aging treatment: cool down to 600℃ at a cooling rate of 6℃ / min, and then keep warm for 1.5h;

[0204] Three-stage post-gradient aging treatment: cool down to 500℃ at a cooling rate of 6℃ / min, and then keep warm for 2h;

[0205] Four-stage post-gradient aging treatment: cool down to 400°C at a cooling rate of 6°C / min, then keep warm for 1.5h, and finally cool to room temperature.

[0206] Embodiment 11

[0207] The difference between this embodiment and embodiment 9 is the four-stage post-gradient aging, and the other steps and parameters are basically the same as those of embodiment 9. In this embodiment, the first-stage post-gradient aging treatment: the samarium cobalt green body treated at 810°C for 9 hours is cooled to 700°C at a cooling rate of 4°C / min, and then kept at this temperature for 1 hour;

[0208] Secondary post-gradient aging treatment: cool down to 600℃ at a cooling rate of 4℃ / min, and then keep warm for 1h;

[0209] Three-stage post-gradient aging treatment: cool down to 500°C at a cooling rate of 4°C / min, and then keep warm for 1h;

[0210] Four-stage post-gradient aging treatment: cool down to 400℃ at a cooling rate of 4℃ / min, then keep warm for 1h, and finally cool to room temperature.

[0211] Comparative Example 1

[0212] The difference between this comparative example and Example 1 is the pre-gradient aging in the aging treatment, and the other steps and parameters are basically the same as those in Example 1. In this comparative example, the aging treatment includes the following steps: heating the samarium cobalt green body after sintering and solid solution to 550°C at 10°C / min and keeping it warm for 3h; then heating it to 750°C at 10°C / min and keeping it warm for 3h; then heating it to 790°C at a heating rate of 5°C / min and keeping it warm for 24h. The samarium cobalt green body treated at 790°C for 24h is cooled to 700°C at a cooling rate of 0.5°C / min, and then kept warm for 3h; then cooled to 600°C at a cooling rate of 0.5°C / min, and then kept warm for 3h; then cooled to 500°C at a cooling rate of 0.5°C / min, and then kept warm for 3h; then cooled to 400°C at a cooling rate of 0.5°C / min, and then kept warm for 3h, and finally cooled to room temperature.

[0213] Comparative Example 2

[0214] The difference between this comparative example and Example 1 is the pre-gradient aging in the aging treatment, and the other steps and parameters are basically the same as those in Example 1. In this comparative example, the aging treatment includes the following steps: heating the samarium cobalt green body after sintering and solid solution to 300°C at 10°C / min and keeping it warm for 3h; then heating it to 750°C at 10°C / min and keeping it warm for 3h; then heating it to 790°C at a heating rate of 5°C / min and keeping it warm for 24h. The samarium cobalt green body treated at 790°C for 24h is cooled to 700°C at a cooling rate of 0.5°C / min, and then kept warm for 3h; then cooled to 600°C at a cooling rate of 0.5°C / min, and then kept warm for 3h; then cooled to 500°C at a cooling rate of 0.5°C / min, and then kept warm for 3h; then cooled to 400°C at a cooling rate of 0.5°C / min, and then kept warm for 3h, and finally cooled to room temperature.

[0215] Comparative Example 3

[0216] The difference between this comparative example and Example 1 is the pre-gradient aging in the aging treatment, and the other steps and parameters are basically the same as those in Example 1. In this comparative example, the aging treatment includes the following steps: heating the samarium cobalt green body after sintering and solid solution to 300°C at 10°C / min and keeping it warm for 3h; then heating it to 550°C at 10°C / min and keeping it warm for 3h; then heating it to 790°C at a heating rate of 5°C / min and keeping it warm for 24h. The samarium cobalt green body treated at 790°C for 24h is cooled to 700°C at a cooling rate of 0.5°C / min, and then kept warm for 3h; then cooled to 600°C at a cooling rate of 0.5°C / min, and then kept warm for 3h; then cooled to 500°C at a cooling rate of 0.5°C / min, and then kept warm for 3h; then cooled to 400°C at a cooling rate of 0.5°C / min, and then kept warm for 3h, and finally cooled to room temperature.

[0217] Comparative Example 4

[0218] The difference between this comparative example and Example 1 is the aging treatment, and the other steps and parameters are basically the same as those in Example 1. In this comparative example, the aging treatment includes the following steps: heating the samarium cobalt green body after sintering and solid solution to 790°C at 5°C / min and keeping it warm for 24 hours; cooling the samarium cobalt green body treated at 790°C for 24 hours to 700°C at a cooling rate of 0.5°C / min, and then keeping it warm for 3 hours; then cooling it to 600°C at a cooling rate of 0.5°C / min, and then keeping it warm for 3 hours; then cooling it to 500°C at a cooling rate of 0.5°C / min, and then keeping it warm for 3 hours; then cooling it to 400°C at a cooling rate of 0.5°C / min, and then keeping it warm for 3 hours, and finally cooling it to room temperature.

[0219] Comparative Example 5

[0220] The difference between this comparative example and Example 2 is the aging treatment, and the other steps and parameters are basically the same as those of Example 2. In this comparative example, the aging treatment includes the following steps: heating the samarium cobalt green body after sintering and solid solution to 830°C at 5°C / min and keeping it warm for 12 hours; cooling the samarium cobalt green body treated at 830°C for 12 hours to 700°C at a cooling rate of 0.5°C / min, and then keeping it warm for 3 hours; then cooling it to 600°C at a cooling rate of 0.5°C / min, and then keeping it warm for 3 hours; then cooling it to 500°C at a cooling rate of 0.5°C / min, and then keeping it warm for 3 hours; then cooling it to 400°C at a cooling rate of 0.5°C / min, and then keeping it warm for 3 hours, and finally cooling it to room temperature.

[0221] Comparative Example 6

[0222] The difference between this comparative example and Example 3 is the aging treatment, and the other steps and parameters are basically the same as those of Example 3. In this comparative example, the aging treatment includes the following steps: heating the samarium cobalt green body after sintering and solid solution to 830°C at 5°C / min and keeping it warm for 20 hours; cooling the samarium cobalt green body treated at 830°C for 20 hours to 700°C at a cooling rate of 0.5°C / min, and then keeping it warm for 3 hours; then cooling it to 600°C at a cooling rate of 0.5°C / min, and then keeping it warm for 3 hours; then cooling it to 500°C at a cooling rate of 0.5°C / min, and then keeping it warm for 3 hours; then cooling it to 400°C at a cooling rate of 0.5°C / min, and then keeping it warm for 3 hours, and finally cooling it to room temperature.

[0223] The magnetic properties of the sintered samarium cobalt permanent magnets obtained in the above embodiments and comparative examples were tested, and the results are shown in Table 3.

[0224] Table 1: Main parameters of aging treatment of Examples and Comparative Examples

[0225]

[0226] Table 2: Main parameters of aging treatment of Examples and Comparative Examples

[0227]

[0228] Table 3: Magnetic properties test results of sintered samarium cobalt permanent magnets obtained in Examples and Comparative Examples

[0229]

[0230] According to the data in Table 3, the squareness and magnetic energy product of Examples 1 to 11 are significantly improved compared with Comparative Examples 1 to 6. This result shows that the double gradient aging treatment method provided by the present invention can effectively optimize the squareness and magnetic energy product of the high iron samarium cobalt permanent magnet, thereby significantly improving its overall magnetic properties. In addition, by optimizing and precisely controlling the key parameters in the double gradient aging treatment process (such as the temperature, heating rate, and insulation time of the three-stage pre-gradient aging treatment), the squareness and magnetic energy product are further improved, thereby improving its overall magnetic properties.

[0231] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A double gradient aging treatment method for high performance sintered samarium cobalt permanent magnets, characterized in that: The dual gradient aging treatment method comprises the following steps: (1) Pre-gradient time effect: First-stage pre-gradient: the samarium-cobalt green body is heated to T1 and then subjected to heat preservation treatment. During the heat preservation treatment after heating to T1, T1 is 210-230°C, the heat preservation time t1 is 0.5-0.8h, and the heating rate R1 is 0.5-1.8°C / min; Secondary front gradient: then heating to T2 and then heat preservation treatment, wherein during the heat preservation treatment after heating to T2, T2 is 460-480°C, the heat preservation time t2 is 0.5-0.8h, and the heating rate R2 is 0.5-1.8°C / min; Three-stage front gradient: heating to T3 and then heat preservation treatment, wherein T3 is 660-680°C, the heat preservation time t3 is 0.5-0.8h, and the heating rate R3 is 0.5-1.8°C / min; (2) Isothermal aging: the samarium-cobalt green body after T3 insulation treatment is heated to T4 and then subjected to insulation treatment; in the insulation treatment after heating to T4, T4 is 790-810°C and the insulation time t4 is 6-15h; (3) Post-gradient aging: First-stage post-gradient: cool the samarium-cobalt green body after T4 heat preservation to T5 and then heat preservation, T5 = T4-135℃~T4-125℃; Secondary post-gradient: then cool down to T6 and then keep warm, T6 = T4-235℃~T4-225℃; Gradient after the third level: cool down to T7 and then keep warm, T7 = T4-335℃~T4-325℃; Gradient after the fourth stage: cool down to T8, keep warm, and finally cool to room temperature; T8 is 360~380℃; The double gradient aging treatment method is adopted to promote the phase transformation process from 2:17H to 2:17R of the magnet and the slip of dislocations and improve the nucleation rate of the 1:5H cell wall phase through the three-stage pre-gradient aging treatment, and generate more 1:5H nano-precipitate phases before the decomposition of the 1:7H phase; in the subsequent isothermal aging process, the cell wall phase will take this as the core and begin to grow; through the four-stage post-gradient aging treatment, the Cu and Fe elements are fully diffused and enter the cell wall phase and the intracellular phase respectively; the squareness is ≥63%, and the maximum magnetic energy product is ≥31MGOe.

2. The dual gradient aging treatment method according to claim 1, characterized in that: Having at least one of the following characteristics: (1) After the temperature is lowered to T5, the temperature is kept warm for a period of 1-3 hours; (2) After the temperature is lowered to T6, the temperature is kept warm for a period of 1-3 hours; (3) After the temperature is lowered to T7, the temperature is kept warm for a period of 1-3 hours; (4) After the temperature is lowered to T8, the temperature is kept warm for a period of 1-3 hours.

3. The dual gradient aging treatment method according to claim 2, characterized in that: The insulation time t5 is 1-1.3h; and / or, the insulation time t6 is 1-1.5h; and / or, the insulation time t7 is 1-2h; and / or, the insulation time t8 is 1-1.5h.

4. The dual gradient aging treatment method according to claim 1, characterized in that: Having at least one of the following characteristics: (1) The temperature is lowered to T5, and the rate of the temperature reduction R5 is 0.5-6°C / min; (2) The temperature is lowered to T6, and the rate of the temperature reduction R6 is 0.5-6°C / min; (3) The temperature is lowered to T7, and the rate of the temperature reduction R7 is 0.5-6°C / min; (4) The temperature is lowered to T8, and the rate of the temperature reduction R8 is 0.5-6°C / min.

5. The dual gradient aging treatment method according to claim 4, characterized in that: The cooling rate R5 and / or R6 and / or R7 and / or R8 is 4-6°C / min.

6. The dual gradient aging treatment method according to claim 1, characterized in that: The samarium-cobalt green body is prepared from the following raw materials by weight percentage: Sm: 24.5-26.0%, Fe: 19-20%, Cu: 5-7%, Zr: 2.5-3.5%, and the balance is Co.

7. A method for preparing a high performance sintered samarium cobalt permanent magnet, characterized in that: The method for preparing the samarium cobalt permanent magnet comprises the following steps: subjecting the samarium cobalt magnet alloy powder to molding, sintering, solid solution and aging treatment; wherein the aging treatment adopts the double gradient aging treatment method as claimed in any one of claims 1 to 6.

8. The method for preparing a high performance sintered samarium cobalt permanent magnet according to claim 7, characterized in that: The main steps of molding the samarium-cobalt magnet alloy powder include: alloy smelting, powder making, and mold pressing; wherein the alloy smelting includes: using one or more of a vacuum arc melting furnace, a micro-positive pressure induction melting furnace, and a vacuum induction melting rapid solidification furnace to smelt the metal raw material to obtain an alloy ingot; The powder making comprises: coarsely crushing and grinding the alloy ingot to make magnetic powder of 2.5-4.5 μm; The compression molding comprises: firstly subjecting the magnetic powder to magnetic field orientation molding, and then cold isostatic pressing to obtain a magnet green body; The main steps of sintering and solid solution treatment include: sintering the magnet green body at 1180-1235° C. for 1.0-2.5 hours, and then performing solid solution treatment at a solid solution temperature of 1125-1185° C. for 8-24 hours to obtain a samarium-cobalt green body.

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