Preparation method of sintered samarium-cobalt magnet

Abstract

The invention provides a preparation method of a sintered samarium-cobalt magnet, and belongs to the technical field of permanent magnet materials, and the preparation method comprises the following steps: S1, preparing a samarium-cobalt green body: after smelting and pouring raw materials, sequentially carrying out mechanical crushing, powder mixing, jet milling, molding and isostatic pressing to obtain the samarium-cobalt green body; s2, preparing a sintered samarium-cobalt precursor: heating and preserving the temperature of the samarium-cobalt green body according to a stepped heating procedure, and discharging excess gas of the samarium-cobalt green body to obtain the sintered samarium-cobalt precursor; s3, preparing a sintered samarium-cobalt magnet: pre-sintering and sintering the samarium-cobalt precursor, cooling to a solid solution temperature, preserving heat for a certain time, and air-cooling to room temperature; and slowly cooling to room temperature along with the furnace, and discharging to obtain the samarium-cobalt magnet. The process is simple and easy to operate, large-scale production is facilitated, and the purpose of considering the mechanical property and the magnetic property of the samarium-cobalt magnet is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of permanent magnetic materials, and in particular to a method for preparing a sintered samarium cobalt magnet. Background Art

[0002] Samarium cobalt permanent magnet materials have high room temperature comprehensive magnetic properties and excellent high temperature stability, so they are widely used in fields such as national defense, aerospace, electronic appliances, new energy vehicles, etc. The manufacturing methods of samarium cobalt magnets include sintering, bonding and injection molding. Sintering is mostly used in production because the upper limit of the magnetic properties of sintered samarium cobalt magnets is relatively high, which can fully demonstrate the application potential of samarium cobalt magnets. However, the preparation of samarium cobalt magnets by sintering requires a higher heating temperature and a longer insulation time. The grain size of the sintered samarium cobalt magnets is larger, which increases the risk of cracking of the samarium cobalt magnets, which are already highly brittle.

[0003] In view of the problem that samarium cobalt magnets are brittle and easy to crack, technicians in this field have made many explorations to improve the mechanical properties of samarium cobalt magnets. There are generally two technical ideas. One is to add toughening components. For example, the patent with publication number CN112017831B, entitled A method for preparing high-toughness samarium cobalt magnets, discloses the addition of copper-based nanowires and carbon nanotubes as toughness materials during the powder mixing stage. Although this improves the mechanical stability of the samarium cobalt magnet, it will damage the magnetic properties of the samarium cobalt magnet.

[0004] The other is to improve and adjust the process of preparing samarium cobalt magnets. For example, the patent with publication number CN117116645A, entitled "A high-strength and high-magnetic performance samarium cobalt magnet and its preparation method", discloses that the samarium cobalt green body before sintering is packaged; the patent with publication number CN118507238A, entitled "A preparation method of samarium cobalt permanent magnet with high mechanical properties", discloses that after the tempering, the blank is subjected to multiple heat treatments while applying magnetic fields and stress; the patent with publication number CN117711793A, entitled "A preparation method of samarium cobalt permanent magnet with high mechanical properties", discloses that the blank is subjected to multiple heat treatments while applying magnetic fields and stress; The patent of the method discloses that the mechanical properties are improved by reducing the cooling rate of tempering to promote the full diffusion and uniform distribution of copper elements; the patent with publication number CN118280716B, entitled A high-temperature and high-bending-strength samarium-cobalt magnet and its preparation process, discloses that the regularity and continuity of the cellular structure are improved by extending the second tempering and heat preservation time, and adding a heat insulation layer to the samarium-cobalt magnet. The above-mentioned technical solutions have a certain effect on improving the mechanical properties of the samarium-cobalt magnet, but increase the production cost and are not suitable for promotion in large-scale production. Summary of the invention

[0005] In view of this, the present invention provides a method for preparing a sintered samarium cobalt magnet, which has a simple process, is easy to operate, is convenient for large-scale production, and achieves the purpose of taking into account both the mechanical properties and magnetic properties of the samarium cobalt magnet.

[0006] To achieve the above object, the present invention provides a method for preparing a sintered samarium cobalt magnet, comprising the following steps: S1. Prepare a samarium cobalt green compact: After melting and casting the raw materials, successively perform mechanical crushing, powder mixing, jet milling, forming, and isostatic pressing to obtain a samarium cobalt green compact; S2. Prepare a sintered samarium cobalt precursor: Heat and hold the samarium cobalt green compact according to a stepped heating program to discharge the excess gas from the samarium cobalt green compact and obtain a sintered samarium cobalt precursor; S3. Prepare a sintered samarium cobalt magnet: The samarium cobalt precursor is pre-sintered, sintered, solution-treated, and then air-cooled; then it is tempered and cooled in the furnace, and the samarium cobalt magnet is obtained after taking out of the furnace.

[0007] Optionally, the stepped heating program in S2 includes three stages, and each stage includes a heating stage and a holding stage. The temperatures of the three stages in chronological order are: 100 - 150 °C, 300 - 400 °C, 950 - 1050 °C; the holding times of the first stage and the third stage are the same, both being 20(M + 1) ± 10 min, and the holding time of the second stage is 40(M + 2) ± 20 min, where M is the weight of a single samarium cobalt green compact, and 0.5 kg ≤ M ≤ 5 kg.

[0008] In the technical solution of the present invention, the holding section steps in the heating stage of the samarium cobalt green compact have different functions. The holding in the first stage is to discharge the moisture in the samarium cobalt green compact, the holding in the second stage is to discharge the gas generated by the decomposition of the organic additive, and the holding in the third stage is mainly to make the internal and external temperatures of the samarium cobalt green compact uniform, form a samarium cobalt precursor with a consistent temperature, and prepare for the subsequent pre-sintering and sintering.

[0009] In the present invention, the holding time of the second holding before sintering is significantly longer than that of the first holding because the inventors found that the adverse effect on the magnetic properties of the samarium cobalt magnet is mainly due to the increase in the carbon and sulfur contents, while the oxygen and hydrogen contents have no obvious effect on the magnetic properties. The holding temperature for exhaust in the second stage is related to the type of additive used in the mixing. If other additives are used, the holding temperature in this stage should also be adjusted accordingly.

[0010] Optionally, when 0.5 ≤ M ≤ 1.5 kg, the heating rates of the first stage and the second stage are both (2 / M ± 1) °C / min, and the heating rate of the third stage is (8 / M ± 2) °C / min; when 1.5 kg < M ≤ 3 kg, the heating rates of the first stage and the second stage are both (M ± 1) °C / min, and the heating rate of the third stage is (12 / M ± 2) °C / min; when 3 < M ≤ 5 kg, the heating rates of the first stage and the second stage are both (M / 2 ± 1) °C / min, and the heating rate of the third stage is (15 / M ± 1) °C / min.

[0011] In the prior process of the front stage of conventional sintering, the heating rate after exhaust is relatively low, generally within 4 °C / min. Especially when the weight of the samarium-cobalt green compact is large, the heating rate is even lower. Otherwise, the cracking risk of the samarium-cobalt blank will increase. In the present invention, the exhaust insulation time is relatively long and the exhaust is relatively sufficient, which is beneficial to reducing the cracking risk of the samarium-cobalt blank and increasing the upper limit of the heating rate.

[0012] In the present invention, the temperature and time settings in the insulation stage are to enable the samarium-cobalt green compact to exhaust sufficiently, ensuring the magnetic properties of the samarium-cobalt magnet, especially the magnetic induction coercivity (H cb ), and the inflection point of the demagnetization curve (H k ) do not decrease; and the increase in the heating rate in the third stage can significantly refine the grain size of the samarium-cobalt blank and improve its bending strength. Increasing the heating rate on the basis of sufficient exhaust of the samarium-cobalt green compact takes into account both the magnetic properties and mechanical properties of the samarium-cobalt magnet.

[0013] Optionally, the raw materials in S1 include 5 elements of Sm, Co, Fe, Cu, and Zr, and the mass percentages of each element are respectively: Sm, 24 - 28%; Fe, 13 - 18%; Cu, 3 - 8%; Zr, 2 - 5%, and the rest is Co, and the sum of the mass percentages of each element is 100%.

[0014] Optionally, the raw materials in S1 include 6 elements of Sm, Co, Fe, Cu, Zr, and Hf, and the mass percentages of each element are respectively: Sm, 20 - 24%; Fe, 13 - 18%; Cu, 3 - 5%; Zr, 2 - 4%; Hf, 8 - 10%; and the rest is Co, and the sum of the mass percentages of each element is 100% Optionally, the melting and casting of the raw materials in S1 include putting the raw materials into a melting furnace or a vacuum rapid solidification furnace to obtain a samarium-cobalt ingot or a sputtering sheet by melting and casting.

[0015] Optionally, a lubricant is added before powder mixing in S1. The lubricant is a stearate powder, and the addition amount accounts for 0.05 - 0.5 wt% of the raw materials, and the powder mixing time is 60 - 180 min.

[0016] Optionally, the particle size of the powder obtained after airflow milling in S1 is 3.5 - 5.0 μm, and the density of the green compact after forming is 3.8 - 4.2 g / cm 3 After isostatic pressing, the density of the green compact is 5.0 - 5.4 g / cm 3 .

[0017] Optionally, the pre-sintering temperature in S3 is 1130 - 1190 °C, and the insulation time is 30 - 90 min; the sintering temperature is 1180 - 1220 °C, and the insulation time is 120 - 240 min; the solution temperature is 1150 - 1200 °C, and the insulation time is 120 - 600 min.

[0018] Optionally, the tempering in S3 includes a first-stage tempering and a second-stage tempering, and the temperature of the second-stage tempering is lower than that of the first-stage tempering.

[0019] Optionally, the temperature of the first-stage tempering is 800-850 °C, the heating rate is 3-8 °C / min, and the holding time is 240-1200 min; the temperature of the second-stage tempering is 380-420 °C, the cooling rate is 0.3-1.0 °C / min, and the holding time is 120-240 min.

[0020] The above technical solutions of the present invention at least include the following beneficial effects: 1. The technical solution of the present invention adapts the green body weight to the exhaust time and heating rate during the exhaust stage, which can ensure sufficient exhaust before sintering without reducing the density and magnetic properties of the samarium cobalt magnet, while reducing the grain size of the samarium cobalt magnet and improving the mechanical properties of the samarium cobalt magnet.

[0021] 2. In the technical solution of the present invention, by adjusting the holding time of the exhaust process in the front stage of sintering and the heating rate after exhaust, no other components need to be added, and no additional processes are required. The operation is simple and suitable for large-scale production.

[0022] 3. The technical solution of the present invention is beneficial to improving the sintering qualification rate and material utilization rate of the samarium cobalt magnet, and reducing the production cost. Description of the Drawings Figure 1 It is a schematic process curve diagram of heating and holding in the front stage of sintering when the single weight M of the green body is in the range of (0.5-1.5) kg in the present invention; Figure 2 It is an SEM diagram of the samarium cobalt magnet of Example 1 of the present invention; Figure 3 It is an SEM diagram of the samarium cobalt magnet of Example 4 of the present invention; Figure 4 It is an SEM diagram of the samarium cobalt magnet of Example 5 of the present invention; Figure 5 It is an SEM diagram of the samarium cobalt magnet of Example 7 of the present invention. Detailed Embodiments

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention fall within the scope of protection of the present invention. Figures 1-5

[0024] ​Example 1 A preparation method of a sintered samarium cobalt magnet is as follows: Prepare a samarium cobalt green compact: The raw material formula consists of 5 elements, namely Sm, Co, Fe, Cu, and Zr. The mass percentages of each element are as follows: Sm, 25.8%; Co, 49.5%; Fe, 15.2%; Cu, 6.5%; Zr, 3%. The above raw materials are melted and cast into a samarium cobalt ingot using a vacuum melting furnace; the samarium cobalt ingot is crushed into coarse powder using a crusher, 0.3 wt% of lubricant is added, and the mixture is mixed for 120 min; then the coarse powder is sent to a jet mill to grind out samarium cobalt fine powder with a particle size of 4.5 μm; the samarium cobalt fine powder is sent to a molding press for molding, and the density after molding is 4.0 g / cm 3 ; then isostatic pressing is carried out, and after pressing, it is a samarium cobalt green compact with a density of 5.2 g / cm 3 , and the weight of a single green compact is 1 kg; Prepare a sintered samarium cobalt precursor: The samarium cobalt green compact is placed in a sintering furnace, evacuated and then heated, and the temperature is raised and the gas is exhausted according to a stepped program: The temperature is raised to 120 °C at a rate of 2 °C / min and held for 40 min; then the temperature is still raised to 340 °C at a rate of 2 °C / min and held for 120 min; then the temperature is raised to 980 °C at a rate of 8 °C / min and held for 40 min. After the temperature-raising and gas-exhausting stage, it becomes a sintered samarium cobalt precursor; Prepare a sintered samarium cobalt magnet: The samarium cobalt precursor is continuously heated to 1150 °C for pre-sintering, filled with argon to 20 kPa, and held for 40 min; then the temperature is raised to 1206 °C for sintering and held for 120 min; then the temperature is lowered to 1182 °C for solution treatment and held for 120 min. Argon is filled to atmospheric pressure before the end of the solution treatment. After the solution treatment, the blower is turned on for air cooling, and the blank is taken out of the furnace when it cools to room temperature; then it is transferred to a furnace for tempering. The temperature is raised to 820 °C at a rate of 5 °C / min and held for 720 min; then the temperature is lowered to 400 °C at a rate of 0.8 °C / min and held for 180 min. After that, it is cooled to room temperature in the furnace and taken out to obtain a samarium cobalt magnet.

[0025] Example 2 A preparation method of a sintered samarium cobalt magnet is as follows: Prepare a samarium cobalt green compact: The raw material formula consists of 5 elements, namely Sm, Co, Fe, Cu, and Zr. The mass percentages of each element are as follows: Sm, 25.8%; Co, 49.5%; Fe, 15.2%; Cu, 6.5%; Zr, 3%. The above raw materials are melted and cast into a samarium cobalt ingot using a vacuum melting furnace; the samarium cobalt ingot is crushed into coarse powder using a crusher, 0.3 wt% of lubricant is added, and the mixture is mixed for 120 min; then the coarse powder is sent to a jet mill to grind out samarium cobalt fine powder with a particle size of 4.5 μm; the samarium cobalt fine powder is sent to a molding press for molding, and the density after molding is 4.0 g / cm 3; Then isostatic pressing is carried out, and after pressing, it becomes a samarium-cobalt green compact with a density of 5.2 g / cm 3 , and the weight of a single green compact is 2 kg; Preparing a sintered samarium-cobalt precursor: Put the samarium-cobalt green compact into a sintering furnace, heat it after evacuating, and raise the temperature and exhaust gas according to a stepped program: Raise the temperature to 120 °C at a rate of 2 °C / min and hold for 60 min; Then still raise the temperature to 340 °C at a rate of 2 °C / min and hold for 160 min; Then raise the temperature to 980 °C at a rate of 6 °C / min and hold for 60 min. After passing through the temperature-raising and exhaust-gas section, it becomes a sintered samarium-cobalt precursor; Preparing a sintered samarium-cobalt magnet: The samarium-cobalt precursor is continuously heated to 1150 °C for pre-sintering, filled with argon to 20 kPa, and held for 60 min; Then raise the temperature to 1206 °C for sintering and hold for 150 min; Then cool down to 1182 °C for solution treatment and hold for 150 min. Before the end of the solution treatment, fill with argon to atmospheric pressure. After the solution treatment, turn on the blower for air cooling. When the blank is cooled to room temperature, take it out of the furnace; Then carry out tempering in a rotary furnace, raise the temperature to 820 °C at a rate of 5 °C / min and hold for 900 min; Then cool down at a rate of 0.7 °C / min to 400 °C and hold for 180 min. After the end, cool with the furnace to room temperature and take it out of the furnace to obtain a samarium-cobalt magnet.

[0026] Example 3 A method for preparing a sintered samarium-cobalt magnet, the steps are as follows: Preparing a samarium-cobalt green compact: The raw material formula is 5 elements of Sm, Co, Fe, Cu, and Zr, and the mass percentages of each element are: Sm, 25.8%; Co, 49.5%; Fe, 15.2%; Cu, 6.5%; Zr, 3%. The above raw materials are melted and cast into a samarium-cobalt ingot by a vacuum melting furnace; The samarium-cobalt ingot is crushed into coarse powder by a crusher, 0.3 wt% of lubricant is added, and the mixture is mixed for 120 min; Then the coarse powder is sent into a jet mill to grind out samarium-cobalt fine powder with a particle size of 4.5 μm; The samarium-cobalt fine powder is sent into a molding press for molding, and the density after molding is 4.0 g / cm 3 ; Then isostatic pressing is carried out, and after pressing, it becomes a samarium-cobalt green compact with a density of 5.2 g / cm 3 , and the weight of a single green compact is 4 kg; Preparing a sintered samarium-cobalt precursor: Put the samarium-cobalt green compact into a sintering furnace, heat it after evacuating, and raise the temperature and exhaust gas according to a stepped program: Raise the temperature to 100 °C at a rate of 2 °C / min and hold for 100 min; Then still raise the temperature to 340 °C at a rate of 2 °C / min and hold for 240 min; Then raise the temperature to 980 °C at a rate of 5 °C / min and hold for 100 min. After passing through the temperature-raising and exhaust-gas section, it becomes a sintered samarium-cobalt precursor; Preparation of sintered samarium-cobalt magnet: The samarium-cobalt precursor is further heated to 1150 °C for pre-sintering, filled with argon to 20 kPa, and held for 80 min; then it is heated to 1206 °C for sintering and held for 180 min; then it is cooled to 1182 °C for solution treatment and held for 180 min. Argon is filled to atmospheric pressure before the end of the solution treatment. After the solution treatment, the blower is turned on for air cooling. The blank is taken out of the furnace when it is cooled to room temperature; then it is transferred to a furnace for tempering, heated to 820 °C at a heating rate of 5 °C / min and held for 1080 min; then it is cooled to 400 °C at a rate of 0.5 °C / min and held for 180 min. After that, it is cooled to room temperature in the furnace and taken out to obtain the samarium-cobalt magnet.

[0027] Example 4 The difference from Example 1 is only that the heating rate in the third stage of preparing the sintered samarium-cobalt precursor is 6 °C / min, and the other raw materials and process steps are the same as those in Example 1.

[0028] Example 5 The difference from Example 1 is only that the heating rate in the third stage of preparing the sintered samarium-cobalt precursor is 10 °C / min, and the other raw materials and process steps are the same as those in Example 1.

[0029] Example 6 The difference from Example 1 is only that the holding time in the second stage of preparing the sintered samarium-cobalt precursor is 100 °C / min, and the other raw materials and process steps are the same as those in Example 1.

[0030] Example 7 The difference from Example 1 is only that the holding time in the second stage of preparing the sintered samarium-cobalt precursor is 140 °C / min, and the other raw materials and process steps are the same as those in Example 1.

[0031] Example 8 The difference from Example 1 is only that the raw material formula is different. The raw material formula consists of 6 elements: Sm, Co, Fe, Cu, Zr, and Hf. The mass percentages of each element are as follows: Sm, 24%; Co, 46%; Fe, 14%; Cu, 4%; Zr, 3%; Hf, 9%.

[0032] Comparative Example 1 The difference from Example 1 is only that the holding time in the second stage of preparing the sintered samarium-cobalt precursor is 60 °C / min, and the heating rate in the third stage is 3 °C / min. The other raw materials and process steps are the same as those in Example 1.

[0033] Comparative Example 2 The difference from Example 1 is only that the holding time in the second stage of preparing the sintered samarium-cobalt precursor is 60 °C / min, and the heating rate in the third stage is 8 °C / min. The other raw materials and process steps are the same as those in Example 1.

[0034] Comparative Example 3 The difference from Example 1 is only that the holding time in the second stage for preparing the sintered samarium cobalt precursor is 60 °C / min, and the heating rate in the third stage is 12 °C / min. The remaining raw materials and process steps are the same as those in Example 1. Comparative Example 4 The difference from Example 1 is only that the holding time in the second stage for preparing the sintered samarium cobalt precursor is 160 °C / min, and the heating rate in the third stage is 3 °C / min. The remaining raw materials and process steps are the same as those in Example 1.

[0035] Comparative Example 5 The difference from Example 1 is only that the holding time in the second stage for preparing the sintered samarium cobalt precursor is 160 °C / min, and the heating rate in the third stage is 8 °C / min. The remaining raw materials and process steps are the same as those in Example 1.

[0036] Comparative Example 6 The difference from Example 1 is only that the holding time in the second stage for preparing the sintered samarium cobalt precursor is 160 °C / min, and the heating rate in the third stage is 12 °C / min. The remaining raw materials and process steps are the same as those in Example 1.

[0037] Comparative Example 7 The difference from Example 1 is only that the holding time in the second stage for preparing the sintered samarium cobalt precursor is 120 °C / min, and the heating rate in the third stage is 3 °C / min. The remaining raw materials and process steps are the same as those in Example 1.

[0038] Comparative Example 8 The difference from Example 1 is only that the holding time in the second stage for preparing the sintered samarium cobalt precursor is 120 °C / min, and the heating rate in the third stage is 12 °C / min. The remaining raw materials and process steps are the same as those in Example 1.

[0039] The density of the samarium cobalt magnets prepared in each example and comparative example was measured by the drainage method. Then, a cylinder with a size of ϕ8×10 was cut out, and the cylinder was crushed and ground into powder to measure the contents of oxygen, hydrogen, carbon, and sulfur. The results are shown in Table 1 below: Table 1 Density and Contents of Oxygen, Hydrogen, Carbon, and Sulfur of Each Samarium Cobalt Magnet in Examples and Comparative Examples

[0040] As can be seen from Table 1, the densities of the samarium-cobalt magnets in each example and comparative example are all above 8.35 and the differences are not significant, indicating that the technical solution of the present invention will not reduce the density of the sintered samarium-cobalt magnet. Compared with Comparative Examples 4-8, the contents of oxygen, hydrogen, carbon, and sulfur in the green bodies of samarium-cobalt in each example are not significantly different after sintering. Even compared with Comparative Example 4, there is no obvious increase, which shows that the exhaust process in the front stage of sintering of the present invention is sufficient to discharge the excess gas in the green body of samarium-cobalt.

[0041] Holes were drilled in the samarium-cobalt magnets prepared in each example and comparative example, and then the magnetic properties were tested; each samarium-cobalt magnet was processed to a size of 20×6×5↑, and the flexural strength was tested. The data of the magnetic properties and flexural strength of the samarium-cobalt magnets in each example and comparative example are shown in Table 2 below: Table 2 Data of magnetic properties and flexural strength of samarium-cobalt magnets in different examples and comparative examples

[0042] As can be seen from Table 2, the remanence of the samarium-cobalt magnets in each example and comparative example has little difference, while the flexural strength of the samarium-cobalt magnets in the examples has been significantly improved overall compared with the comparative examples, including the samarium-cobalt magnets in Comparative Examples 2, 5, 6, and 8 also have relatively high flexural strength. Combining with Figures 2-5 the SEM images, it can be seen that the improvement of the flexural strength of the samarium-cobalt magnets in each example is due to the reduction of the overall grain size, and the reduction of the grain size is because of the increase in the heating rate after the green body of samarium-cobalt is exhausted. The H cb and H k of the samarium-cobalt magnets in Comparative Examples 1-3 are lower than those in the examples and other comparative examples, indicating that the exhaust of the green body of samarium-cobalt is not thorough enough and the holding time in the exhaust section is insufficient. The significant decrease in the flexural strength of the samarium-cobalt magnet in Comparative Example 3 is because the exhaust is insufficient and the heating rate is too fast at the same time, resulting in microcracks inside the samarium-cobalt magnet.

[0043] In summary, the method provided by the present invention can improve the mechanical properties of samarium-cobalt magnets without damaging their magnetic properties. At the same time, no new processes or new materials are introduced, the cost changes little, and the process is suitable for large-scale production.

[0044] The above is the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a sintered samarium cobalt magnet, characterized in that, It includes the following steps: S1. Prepare the samarium-cobalt green compact: After melting and casting the raw materials, successively perform mechanical crushing, powder mixing, air jet milling, forming, and isostatic pressing to obtain the samarium-cobalt green compact; S2. Prepare the sintered samarium-cobalt precursor: Heat up and keep the temperature of the samarium-cobalt green compact according to a stepped heating program to obtain the sintered samarium-cobalt precursor; S3. Prepare the sintered samarium-cobalt magnet: The samarium-cobalt precursor is pre-sintered, sintered, and solution-treated and then air-cooled; Then, after tempering and furnace cooling, the samarium-cobalt magnet is obtained when taken out of the furnace.

2. The preparation method of the sintered samarium cobalt magnet according to claim 1, wherein The stepped heating program in S2 includes three stages, and each stage includes a heating-up stage and a heat-preservation stage. The temperatures of the three stages in chronological order are: 100 - 150 °C, 300 - 400 °C, 950 - 1050 °C; the heat-preservation times of the first stage and the third stage are the same, both being 20(M + 1) ± 10 min, and the heat-preservation time of the second stage is 40(M + 2) ± 20 min, where M is the weight of a single samarium-cobalt green compact, and 0.5 kg ≤ M ≤ 5 kg.

3. The preparation method of the sintered samarium cobalt magnet according to claim 2, characterized in that, When 0.5 ≤ M ≤ 1.5 kg, the heating-up rates of the first stage and the second stage are both (2 / M ± 1) °C / min, and the heating-up rate of the third stage is (8 / M ± 2) °C / min; when 1.5 kg < M ≤ 3 kg, the heating-up rates of the first stage and the second stage are both (M ± 1) °C / min, and the heating-up rate of the third stage is (12 / M ± 2) °C / min; when 3 < M ≤ 5 kg, the heating-up rates of the first stage and the second stage are both (M / 2 ± 1) °C / min, and the heating-up rate of the third stage is (15 / M ± 1) °C / min.

4. The preparation method of the sintered samarium cobalt magnet according to claim 1, characterized in that, The raw materials in S1 include 5 elements of Sm, Co, Fe, Cu, and Zr, and the mass percentages of each element are respectively: Sm, 24 - 28%; Fe, 13 - 18%; Cu, 3 - 8%; Zr, 2 - 5%, and the rest is Co, and the sum of the mass percentages of each element is 100%.

5. The preparation method of the sintered samarium cobalt magnet according to claim 1, characterized in that, The raw material melting and casting in S1 includes putting the raw materials into a melting furnace or a vacuum rapid solidification furnace to melt and cast to obtain a samarium-cobalt ingot or a sputtering target.

6. The preparation method of the sintered samarium cobalt magnet according to claim 1, wherein A lubricant is added before powder mixing in S1. The lubricant is a stearate powder, and the addition amount accounts for 0.05 - 0.5 wt% of the raw materials, and the powder mixing time is 60 - 180 min.

7. The method for preparing a sintered samarium cobalt magnet according to claim 1, wherein The particle size of the powder obtained after airflow milling in S1 is 3.5 - 5.0 μm, and the green density after forming is 3.8 - 4.2 g / cm 3 , and the green density after isostatic pressing is 5.0 - 5.4 g / cm 3 .

8. The preparation method of the sintered samarium cobalt magnet according to claim 1, characterized in that The pre-sintering temperature in S3 is 1130 - 1190 °C, and the heat-preservation time is 30 - 90 min; the sintering temperature is 1180 - 1220 °C, and the heat-preservation time is 120 - 240 min; the solution treatment temperature is 1150 - 1200 °C, and the heat-preservation time is 120 - 600 min.

9. The preparation method of the sintered samarium cobalt magnet according to claim 1, wherein, The tempering in S3 includes the first-stage tempering and the second-stage tempering, and the temperature of the second-stage tempering is lower than that of the first-stage tempering.

10. The preparation method of the sintered samarium cobalt magnet according to claim 9, characterized in that, The temperature of the first-stage tempering is 800 - 850 °C, the heating-up rate is 3 - 8 °C / min, and the heat-preservation time is 240 - 1200 min; the temperature of the second-stage tempering is 380 - 420 °C, the cooling rate is 0.3 - 1.0 °C / min, and the heat-preservation time is 120 - 240 min.

Images