阅读说明：本技术 一种低温度系数Sm2Co17型烧结磁体及其制备方法 (Low-temperature coefficient Sm2Co17Molded sintered magnet and method for producing same ) 是由 俞能君 单杰峰 张朋越 泮敏翔 吴琼 葛洪良 于 2019-12-24 设计创作，主要内容包括：本发明公开了一种低温度系数Sm-2Co-(17)型烧结磁体及其制备方法,本发明通过分别制备合金铸锭Sm(CoFeCuZr)z合金和RECuZr合金,分别破碎后制成粉末,将合金粉末混合,球磨,然后进行磁场取向和冷等静压处理制成压坯,后进行烧结、固溶和回火处理,制得低温度系数Sm-2Co-(17)型烧结磁体。本发明的制备方法能够制得剩磁温度系数较低的磁体,而且该磁体的磁性能较高,所用的重稀土含量较少,成本较低。(The invention discloses a low temperature coefficient Sm 2 Co 17 The invention relates to a type sintered magnet and a preparation method thereof, wherein alloy ingots Sm (CoFeCuZr) z alloy and RECuZr alloy are respectively prepared, the alloy ingots Sm (CoFeCuZr) z alloy and the RECuZr alloy are respectively crushed to prepare powder, the alloy powder is mixed and ball-milled, then the powder is subjected to magnetic field orientation and cold isostatic pressing treatment to prepare pressed compacts, and then sintering, solid solution and tempering treatment are carried out to prepare the low-temperature coefficient Sm 2 Co 17 The sintered magnet is molded. The preparation method can prepare the magnet with lower temperature coefficient of remanence, and the magnet has higher magnetic performance, less content of heavy rare earth and lower cost.)

1. Low-temperature coefficient Sm₂Co₁₇The preparation method of the molded sintered magnet is characterized by comprising the following steps of:

1) weighing raw materials according to the mass percent of each element in Sm (CoFeCuZr) z alloy, mixing, and carrying out vacuum melting on the mixed raw materials to prepare an alloy ingot; wherein, in the Sm (CoFeCuZr) z alloy, the mass percentage of Sm is 20%, the mass percentage of Co is 72.5%, the mass percentage of Fe is 5%, the mass percentage of Cu is 2%, and the mass percentage of Zr is 0.5%;

2) weighing and mixing the raw materials according to the components of the RECuZr alloy, carrying out vacuum induction melting or arc melting on the mixed raw materials to prepare an alloy ingot, and carrying out high-energy ball milling to prepare RECuZr alloy powder; in the RECuZr alloy, RE is one or more of Dy, Er, Ho, Tb, Lu and Gd, and the components in percentage by mass are as follows: 50-80% of RE, 15-40% of Cu and 5-10% of Zr;

3) crushing the alloy ingot prepared in the step 1) to prepare Sm (CoFeCuZr) z alloy coarse powder, uniformly mixing the Sm (CoFeCuZr) z alloy coarse powder with the RECuZr alloy powder prepared in the step 2) in proportion, and then performing ball milling to prepare alloy powder, wherein the granularity of the alloy powder is 2-5 mu m; wherein the addition amount of the RECuZr alloy powder accounts for 10-40% of the mass of the Sm (CoFeCuZr) z alloy coarse powder;

4) carrying out magnetic field orientation and cold isostatic pressing treatment on the alloy powder prepared in the step 3) to prepare a pressed blank;

5) sintering and solution treatment are carried out on the pressed compact prepared in the step 4), and then the pressed compact is returnedFire treatment to obtain the low temperature coefficient Sm₂Co₁₇The sintered magnet is molded.

2. A low temperature coefficient Sm as claimed in claim 1₂Co₁₇The preparation method of the type sintered magnet is characterized in that the magnetic field in the step (4) is oriented and formed, the oriented magnetic field is 2T, the cold isostatic pressure is 350MPa, and the cold isostatic time is 5 min.

3. A low temperature coefficient Sm as claimed in claim 1₂Co₁₇The preparation method of the molded sintered magnet is characterized in that in the step (5), the sintering process is as follows: the sintering temperature is 1190-1240 ℃, and the sintering time is 1-3 h; the solid solution temperature is 1160-1195 ℃, and the solid solution time is 1-9 h; the tempering treatment process comprises the following steps: keeping the temperature at 800-850 ℃ for 5-20 h, then cooling to 720 ℃ at 0.6 ℃/min, keeping the temperature for 3h, then cooling to 630 ℃ at 0.9 ℃/min, then cooling to 490 ℃ at 1.2 ℃/min, then slowly cooling to 380 ℃ at 2 ℃/min, and then cooling to room temperature.

4. Low-temperature coefficient Sm₂Co₁₇Sintered magnet of the type produced by the production method according to any one of claims 1 to 3.

Technical Field

The invention belongs to the field of permanent magnet material preparation, and particularly relates to a low-temperature coefficient Sm₂Co₁₇A sintered magnet and a method for producing the same.

Background

With the development of the fields of aerospace, national defense industry and the like, the conventional samarium-cobalt permanent magnet and neodymium-iron-boron permanent magnet cannot meet the requirements. Conventional Sm₂Co₁₇Although the curie temperature of the sintered magnet is far higher than that of the neodymium iron boron permanent magnet, the intrinsic coercive force of the sintered magnet is reduced along with the rise of the working temperature, so that the stable working performance cannot be maintained, and the magnet is very necessary to have a lower temperature coefficient. Existing abnormal temperature coefficient Sm₂Co₁₇The intrinsic coercive force of the magnet increases with the increase of temperature within a certain temperature range, but the intrinsic coercive force is low (about 0.1T), and thus it is difficult to meet the actual performance requirements. While conventional RE (CoFeCuZr)_z(RE is Sm, Dy, Er, Gd) to prepare Sm with low temperature coefficient₂Co₁₇The proportion of heavy rare earth elements can reach 60 percent when the magnet is sintered, and the price of the heavy rare earth elements is much more expensive than that of light rare earth elements, so that the price of the magnet is greatly improved. Therefore, a low temperature coefficient Sm was sought₂Co₁₇The novel method of the sintered magnet has important significance.

Disclosure of Invention

Aiming at the situation, in order to overcome the defects of the prior art, the invention provides a low-temperature coefficient Sm₂Co₁₇A sintered magnet and a method for producing the same.

In order to achieve the purpose, the invention provides the following technical scheme:

low-temperature coefficient Sm₂Co₁₇The preparation method of the molded sintered magnet comprises the following steps:

1) weighing raw materials according to the mass percent of each element in Sm (CoFeCuZr) z alloy, mixing, and carrying out vacuum melting on the mixed raw materials to prepare an alloy ingot; wherein, in the Sm (CoFeCuZr) z alloy, by mass percent, Sm is 15-25%, Co is 55-88.5%, Fe is 4-14%, Cu is 2-4%, and Zr is 0.5-2%;

2) weighing and mixing the raw materials according to the components of the RECuZr alloy, carrying out vacuum induction melting or arc melting on the mixed raw materials to prepare an alloy ingot, and carrying out high-energy ball milling to prepare RECuZr alloy powder; in the RECuZr alloy, RE is one or more of Dy, Er, Ho, Tb, Lu and Gd, and the components in percentage by mass are as follows: 50-80% of RE, 15-40% of Cu and 5-10% of Zr;

3) crushing the alloy ingot prepared in the step 1) to prepare Sm (CoFeCuZr) z alloy coarse powder, uniformly mixing the Sm (CoFeCuZr) z alloy coarse powder with the RECuZr alloy powder prepared in the step 2) in proportion, and then performing ball milling to prepare alloy powder, wherein the granularity of the alloy powder is 2-5 mu m; wherein the addition amount of the RECuZr alloy powder accounts for 10-40% of the mass of the Sm (CoFeCuZr) z alloy coarse powder;

4) carrying out magnetic field orientation and cold isostatic pressing treatment on the alloy powder prepared in the step 3) to prepare a pressed blank;

5) sintering and solution treatment are carried out on the pressed compact prepared in the step 4), and then tempering treatment is carried out to prepare the low temperature coefficient Sm₂Co₁₇The sintered magnet is molded.

Further, the magnetic field in the step (4) is oriented and formed, the oriented magnetic field is 2T, the cold isostatic pressure is 350MPa, and the cold isostatic time is 5 min.

Further, in the step (5), the sintering process is as follows: the sintering temperature is 1190-1240 ℃, and the sintering time is 1-3 h; the solid solution temperature is 1160-1195 ℃, and the solid solution time is 1-9 h; the tempering treatment process comprises the following steps: keeping the temperature at 800-850 ℃ for 5-20 h, then cooling to 720 ℃ at 0.6 ℃/min, keeping the temperature for 3h, then cooling to 630 ℃ at 0.9 ℃/min, then cooling to 490 ℃ at 1.2 ℃/min, then cooling to 380 ℃ at 2 ℃/min, and then cooling to room temperature.

Low-temperature coefficient Sm₂Co₁₇The sintered magnet is prepared by the preparation method.

The invention has the beneficial effects that:

(1) the invention respectively prepares alloy ingot Sm (CoFeCuZr)_zRespectively crushing the alloy and the RECuZr alloy to prepare powder, mixing the alloy powder, ball-milling, then carrying out magnetic field orientation and cold isostatic pressing treatment to prepare a compact, and then carrying out sintering, solid solution and tempering treatment to prepare the low temperature coefficient Sm₂Co₁₇The sintered magnet is molded.

(2) The preparation method can prepare the magnet with lower temperature coefficient of remanence, and the magnet has higher magnetic performance, less content of heavy rare earth and lower cost.

Detailed Description

The technical solutions of the present invention are described in further detail below, and it should be noted that the specific embodiments are only for describing the present invention in detail, and should not be construed as limiting the present invention.

Example 1

(1) Alloy Sm (CoFeCuZr)_zAccording to the mass percentage, Sm is 15%, Co is 77.5%, Fe is 5%, Cu is 2%, Zr is 0.5%, the raw materials are weighed according to the mass ratio of the above elements, the raw materials are mixed and subjected to vacuum induction melting, the power is 45kW, and the vacuum degree is less than 5 x 10^-2Pa, refining for 5-10 min after the metal is melted to prepare an alloy ingot, and coarsely crushing until the particle size of the powder is 300-500 mu m.

(2) The alloy RECuZr (RE is Dy and Er) is measured according to the mass percentage, Dy is 40 percent, Er is 30 percent, Cu is 20 percent, and Zr is 10 percent, the raw materials are weighed according to the mass ratio of the elements, the raw materials are mixed and subjected to vacuum induction melting, the power is 45kW, and the vacuum degree is less than 5 x 10^-2Pa, refining for 5-10 min after the metal is melted to prepare an alloy ingot, and performing high-energy ball milling to prepare DyErCuZr alloy powder with the powder granularity of 50-200 nm.

(3) Sm (CoFeCuZr) obtained in the step (1)_zUniformly mixing the alloy coarse powder and DyErCuZr alloy powder obtained in the step (2) according to a mass ratio, wherein the addition amount of the DyErCuZr alloy powder accounts for Sm (CoFeCuZr)_zAnd (3) 20% of the mass of the alloy coarse powder, and then ball-milling the alloy coarse powder to prepare alloy powder, wherein the granularity of the main phase alloy powder is 2-5 mu m. The magnet after mixing comprises the following components in percentage by mass: 12.5% of Sm, 6.67% of Dy, 5% of Er, 5% of Cu, 2.08% of Zr, 4.17% of Fe, and 64.58% of Co;

(4) and (4) carrying out magnetic field orientation and cold isostatic pressing treatment on the alloy powder obtained in the step (3) to prepare a pressed blank, wherein the orientation magnetic field is 2T, the cold isostatic pressing pressure is 350MPa, and the cold isostatic pressing time is 5 min. In the preparation process of the sintered magnet, the anisotropic magnet can be obtained through orientation forming, and the density of a pressed compact can be improved through cold isostatic pressing treatment, so that the sintered magnet is beneficial to sintering and compacting.

(5) Sintering and solution treatment are carried out on the prepared pressed compact, and then tempering treatment is carried out to prepare the low temperature coefficient Sm₂Co₁₇The sintered magnet comprises the following sintering processes: the sintering temperature is 1200 ℃, and the sintering time is 2 hours; the solid solution temperature is 1175 ℃, and the solid solution time is 7 h; the tempering treatment process comprises the following steps: keeping the temperature at 800 ℃ for 10h, cooling to 720 ℃ at 0.6 ℃/min, keeping the temperature for 3h, cooling to 630 ℃ at 0.9 ℃/min, cooling to 490 ℃ at 1.2 ℃/min, cooling to 380 ℃ at 2 ℃/min, and cooling to room temperature. In the tempering treatment process, the temperature is reduced for multiple times, so that the diffusion of elements is facilitated, the squareness of the magnet can be optimized, and the coercivity can be improved.

Comparative examples 1 to 1

(1) According to the overall magnet formulation described in example 1, in mass percent: 12.5% of Sm, 6.67% of Dy, 5% of Er, 5% of Cu, 2.08% of Zr, 4.17% of Fe and 64.58% of Co, weighing the raw materials according to the mass ratio of the elements, mixing the raw materials, and carrying out vacuum induction melting, wherein the power is 45kW, and the vacuum degree is less than 5 x 10^-2Pa, refining for 5-10 min after the metal is melted to prepare an alloy ingot, and coarsely crushing the alloy ingot until the particle size of the powder is 300-500 mu m.

(2) SmDyEr (CoF) obtained in the step (1)eCuZr)_zCrushing the alloy coarse powder, and performing ball milling to prepare alloy powder with the particle size of 2-5 microns.

(3) And (3) carrying out magnetic field orientation and cold isostatic pressing treatment on the alloy powder obtained in the step (2) to prepare a pressed blank, wherein the orientation magnetic field is 2T, the cold isostatic pressing pressure is 350MPa, and the cold isostatic pressing time is 5 min.

(4) Sintering and solution treatment are carried out on the prepared pressed compact, and then tempering treatment is carried out to prepare the low temperature coefficient Sm₂Co₁₇The sintered magnet comprises the following sintering processes: the sintering temperature is 1200 ℃, and the sintering time is 2 hours; the solid solution temperature is 1175 ℃, and the solid solution time is 7 h; the tempering treatment process comprises the following steps: keeping the temperature at 800 ℃ for 10h, cooling to 720 ℃ at 0.6 ℃/min, keeping the temperature for 3h, cooling to 630 ℃ at 0.9 ℃/min, cooling to 490 ℃ at 1.2 ℃/min, cooling to 380 ℃ at 2 ℃/min, and cooling to room temperature.

Comparative examples 1 to 2 different amounts of heavy rare earth

The weight percentage of the material is as follows: 10 percent of Sm, 8.17 percent of Dy, 6 percent of Er, 5 percent of Cu, 2.08 percent of Zr, 4.17 percent of Fe and 64.58 percent of Co, weighing the raw materials according to the mass ratio of the elements, mixing the raw materials, and carrying out vacuum induction melting, wherein the power is 45kW, and the vacuum degree is less than 5 x 10^-2Pa, refining for 5-10 min after the metal is melted to prepare an alloy ingot, and coarsely crushing the alloy ingot until the particle size of the powder is 300-500 mu m.

(2) SmDyEr (CoFeCuZr) obtained in the step (1)_zCrushing the alloy coarse powder, and performing ball milling to prepare alloy powder with the particle size of 2-5 microns.

(3) And (3) carrying out magnetic field orientation and cold isostatic pressing treatment on the alloy powder obtained in the step (2) to prepare a pressed blank, wherein the orientation magnetic field is 2T, the cold isostatic pressing pressure is 350MPa, and the cold isostatic pressing time is 5 min.

(4) Sintering and solution treatment are carried out on the prepared pressed compact, and then tempering treatment is carried out to prepare the low temperature coefficient Sm₂Co₁₇The sintered magnet comprises the following sintering processes: the sintering temperature is 1200 ℃, and the sintering time is 2 hours; the solid solution temperature is 1175 ℃, and the solid solution time is 7 h; the tempering treatment process comprises the following steps: incubation at 800 ℃ for 10h, followed byCooling to 720 deg.C at 0.6 deg.C/min, keeping the temperature for 3h, cooling to 630 deg.C at 0.9 deg.C/min, cooling to 490 deg.C at 1.2 deg.C/min, cooling to 380 deg.C at 2 deg.C/min, and cooling to room temperature.

Comparative examples 1 to 3 without adding heavy rare earth

Heavy rare earth is not added, Dy and Er are replaced by Sm, and the Dy and Er are calculated by mass percent: 24.17% of Sm, 5% of Cu, 2.08% of Zr, 4.17% of Fe and 64.58% of Co, weighing the raw materials according to the mass ratio of the elements, mixing the raw materials, and carrying out vacuum induction melting, wherein the power is 45kW, and the vacuum degree is less than 5 × 10^-2Pa, refining for 5-10 min after the metal is melted to prepare an alloy ingot, and coarsely crushing the alloy ingot until the particle size of the powder is 300-500 mu m.

(2) And (2) crushing the alloy coarse powder obtained in the step (1), and performing ball milling to prepare alloy powder, wherein the particle size of the powder is 2-5 microns.

(3) And (3) carrying out magnetic field orientation and cold isostatic pressing treatment on the alloy powder obtained in the step (2) to prepare a pressed blank, wherein the orientation magnetic field is 2T, the cold isostatic pressing pressure is 350MPa, and the cold isostatic pressing time is 5 min.

(4) Sintering and solution treatment are carried out on the prepared pressed compact, and then tempering treatment is carried out to prepare the low temperature coefficient Sm₂Co₁₇The sintered magnet comprises the following sintering processes: the sintering temperature is 1200 ℃, and the sintering time is 2 hours; the solid solution temperature is 1175 ℃, and the solid solution time is 7 h; the tempering treatment process comprises the following steps: keeping the temperature at 800 ℃ for 10h, cooling to 720 ℃ at 0.6 ℃/min, keeping the temperature for 3h, cooling to 630 ℃ at 0.9 ℃/min, cooling to 490 ℃ at 1.2 ℃/min, cooling to 380 ℃ at 2 ℃/min, and cooling to room temperature.

The magnetic properties of the prepared magnets were measured by a BH tester (or a pulse magnetometer), and the magnetic property data of example 1 and comparative examples 1-1, 1-2, and 1-3 at room temperature (20 ℃ C.) and 200 ℃ C. are shown in Table 1.

TABLE 120 ℃ and 200 ℃ magnetic Performance data for example 1 and comparative example

By comparing example 1 with comparative example 1-1, the magnetic properties of the magnet produced by the method of the present invention are superior to those of the magnet produced by comparative example 1-1. Under the same usage amount of heavy rare earth elements, the temperature range of the magnet prepared in the embodiment 1 is 20-200 ℃, the remanence temperature coefficient is-0.02%/DEG C, and the temperature range of the magnet prepared in the invention is 20-200 ℃, and the remanence temperature coefficient is obviously superior to that of the magnet prepared in the comparative example 1-1 (-0.027%/DEG C).

Comparative examples 1-2 the residual magnetization temperature coefficient of the magnet was optimized by further increasing the contents of heavy rare earths Dy and Er in the magnet, the Dy/Er content being 11.67% by mass in example 1; the temperature coefficient of remanence of the magnet prepared in example 1 was-0.02%/deg.C within the temperature range of 20-200 deg.C. In the comparative examples 1-2, the Dy/Er content is 14.17 percent by mass percent, the use amount of the heavy rare earth is increased, the temperature coefficient of remanence of the magnet prepared in the comparative examples 1-2 is-0.021%/° C within the temperature range of 20-200 ℃, the temperature coefficient is slightly higher than that of the magnet prepared in the example 1, and the magnetic performance of the magnet prepared in the comparative examples 1-2 is obviously lower than that of the magnet prepared in the example 1. This shows that the residual magnetism temperature coefficient of the magnet can be reduced by increasing the content of heavy rare earth Dy and Er, but the prepared magnet has lower magnetic performance, and the content of heavy rare earth is increased, so that the cost is greatly increased. The preparation method can prepare the magnet with lower temperature coefficient of remanence, and the magnet has higher magnetic performance and less content of heavy rare earth.

In comparative examples 1 to 3, no rare earth element was added, and it can be seen from Table 1 that, although the magnetic properties of the magnets prepared in comparative examples 1 to 3 were slightly superior to those of example 1, the temperature coefficient of remanence thereof was-0.031%/deg.C within the temperature range of 20 to 200 deg.C, which was significantly inferior to the magnets prepared in example 1. This indicates that the prepared magnet has a high temperature coefficient of remanence without adding heavy rare earth, which is not favorable for preparing a magnet with a low temperature coefficient of remanence.

Example 2

(1) Alloy Sm (CoFeCuZr)_zThe raw materials are weighed according to the mass ratio of the elements, and then the raw materials are mixed into the mixture, wherein Sm is 20 percent, Co is 72.5 percent, Fe is 5 percent, Cu is 2 percent, and Zr is 0.5 percentVacuum induction melting with power of 45kW and vacuum degree of less than 5 x 10^-2Pa, refining for 5-10 min after the metal is melted to prepare an alloy ingot, and coarsely crushing until the particle size of the powder is 300-500 mu m;

(2) alloy RECuZr (RE is Dy and Gd), wherein Dy is 40 percent, Gd is 30 percent, Cu is 20 percent, and Zr is 10 percent, the raw materials are weighed according to the mass ratio of the elements, the raw materials are mixed and subjected to vacuum induction melting, the power is 45kW, and the vacuum degree is less than 5 x 10^-2Pa, refining for 5-10 min after the metal is melted to prepare an alloy ingot, and performing high-energy ball milling to prepare Dy GdCuZr alloy powder with the powder granularity of 50-200 nm.

(3) Sm (CoFeCuZr) obtained in the step (1)_zUniformly mixing the alloy coarse powder and DyGdCuZr alloy powder obtained in the step (2) according to a mass ratio, wherein the addition amount of the DyGdCuZr alloy powder accounts for Sm (CoFeCuZr)_z25% of the mass of the alloy coarse powder, and then ball-milling to prepare alloy powder, wherein the granularity of the main-phase alloy powder is 2-5 μm; after mixing, according to the mass percentage: 16.0% of Sm, 8.0% of Dy, 6.0% of Gd, 5.6% of Cu, 2.4% of Zr, 4.0% of Fe, and 58.0% of Co;

(4) and (4) carrying out magnetic field orientation and cold isostatic pressing treatment on the alloy powder obtained in the step (3) to prepare a pressed blank, wherein the orientation magnetic field is 2T, the cold isostatic pressing pressure is 350MPa, and the cold isostatic pressing time is 5 min.

(5) Sintering and solution treatment are carried out on the prepared pressed compact, and then tempering treatment is carried out to prepare the low temperature coefficient Sm₂Co₁₇The sintered magnet comprises the following sintering processes: the sintering temperature is 1225 ℃, and the sintering time is 2 hours; the solid solution temperature is 1170 ℃, and the solid solution time is 5 h; the tempering treatment process comprises the following steps: keeping the temperature at 800 ℃ for 10h, cooling to 720 ℃ at 0.6 ℃/min, keeping the temperature for 3h, cooling to 630 ℃ at 0.9 ℃/min, cooling to 490 ℃ at 1.2 ℃/min, cooling to 380 ℃ at 2 ℃/min, and cooling to room temperature.

Comparative example 2-1

According to the overall magnet formulation described in example 1, in mass percent: 16.0% of Sm, 8.0% of Dy, 6.0% of Gd, 5.6% of Cu, 2.4% of Zr, 4.0% of Fe,co is 58.0 percent, the raw materials are weighed according to the mass ratio of the elements, the raw materials are mixed and subjected to vacuum induction melting, the power is 45kW, and the vacuum degree is less than 5 x 10^-2Pa, refining for 5-10 min after the metal is melted to prepare an alloy ingot, and coarsely crushing the alloy ingot until the particle size of the powder is 300-500 mu m.

(2) And (2) crushing the alloy coarse powder obtained in the step (1), and performing ball milling to prepare alloy powder, wherein the particle size of the powder is 2-5 microns.

(3) And (3) carrying out magnetic field orientation and cold isostatic pressing treatment on the alloy powder obtained in the step (2) to prepare a pressed blank, wherein the orientation magnetic field is 2T, the cold isostatic pressing pressure is 350MPa, and the cold isostatic pressing time is 5 min.

(4) Sintering and solution treatment are carried out on the prepared pressed compact, and then tempering treatment is carried out to prepare the low temperature coefficient Sm₂Co₁₇The sintered magnet comprises the following sintering processes: the sintering temperature is 1225 ℃, and the sintering time is 2 hours; the solid solution temperature is 1170 ℃, and the solid solution time is 5 h; the tempering treatment process comprises the following steps: keeping the temperature at 800 ℃ for 10h, cooling to 720 ℃ at 0.6 ℃/min, keeping the temperature for 3h, cooling to 630 ℃ at 0.9 ℃/min, cooling to 490 ℃ at 1.2 ℃/min, cooling to 380 ℃ at 2 ℃/min, and cooling to room temperature.

Comparative examples 2-2 different amounts of heavy rare earth

In the present comparative example, the following were measured by mass percent: 13% of Sm, 9.5% of Dy, 7.5% of Gd, 5.6% of Cu, 2.4% of Zr, 4.0% of Fe and 58.0% of Co, weighing the raw materials according to the mass ratio of the elements, mixing the raw materials, and carrying out vacuum induction melting, wherein the power is 45kW, and the vacuum degree is less than 5 × 10^-2Pa, refining for 5-10 min after the metal is melted to prepare an alloy ingot, and coarsely crushing the alloy ingot until the particle size of the powder is 300-500 mu m.

(2) And (2) crushing the alloy coarse powder obtained in the step (1), and performing ball milling to prepare alloy powder, wherein the particle size of the powder is 2-5 microns.

(3) And (3) carrying out magnetic field orientation and cold isostatic pressing treatment on the alloy powder obtained in the step (2) to prepare a pressed blank, wherein the orientation magnetic field is 2T, the cold isostatic pressing pressure is 350MPa, and the cold isostatic pressing time is 5 min.

(4) Sintering and solution treatment are carried out on the prepared pressed compact, and then tempering treatment is carried out to prepare the low temperature coefficient Sm₂Co₁₇The sintered magnet comprises the following sintering processes: the sintering temperature is 1225 ℃, and the sintering time is 2 hours; the solid solution temperature is 1170 ℃, and the solid solution time is 5 h; the tempering treatment process comprises the following steps: keeping the temperature at 800 ℃ for 10h, cooling to 720 ℃ at 0.6 ℃/min, keeping the temperature for 3h, cooling to 630 ℃ at 0.9 ℃/min, cooling to 490 ℃ at 1.2 ℃/min, cooling to 380 ℃ at 2 ℃/min, and cooling to room temperature.

Comparative examples 2 to 3 without adding heavy rare earth

In the comparative example, heavy rare earth elements are not added, and the weight percentages are as follows: 30.0% of Sm, 5.6% of Cu, 2.4% of Zr, 4.0% of Fe and 58.0% of Co, weighing the raw materials according to the mass ratio of the elements, mixing the raw materials, and carrying out vacuum induction melting, wherein the power is 45kW, and the vacuum degree is less than 5 x 10^-2Pa, refining for 5-10 min after the metal is melted to prepare an alloy ingot, and coarsely crushing the alloy ingot until the particle size of the powder is 300-500 mu m.

(2) And (2) crushing the alloy coarse powder obtained in the step (1), and performing ball milling to prepare alloy powder, wherein the particle size of the powder is 2-5 microns.

(3) And (3) carrying out magnetic field orientation and cold isostatic pressing treatment on the alloy powder obtained in the step (2) to prepare a pressed blank, wherein the orientation magnetic field is 2T, the cold isostatic pressing pressure is 350MPa, and the cold isostatic pressing time is 5 min.

(4) Sintering and solution treatment are carried out on the prepared pressed compact, and then tempering treatment is carried out to prepare the low temperature coefficient Sm₂Co₁₇The sintered magnet comprises the following sintering processes: the sintering temperature is 1225 ℃, and the sintering time is 2 hours; the solid solution temperature is 1170 ℃, and the solid solution time is 5 h; the tempering treatment process comprises the following steps: keeping the temperature at 800 ℃ for 10h, cooling to 720 ℃ at 0.6 ℃/min, keeping the temperature for 3h, cooling to 630 ℃ at 0.9 ℃/min, cooling to 490 ℃ at 1.2 ℃/min, cooling to 380 ℃ at 2 ℃/min, and cooling to room temperature.

The magnetic properties of the prepared magnets were measured by a BH tester (or a pulse magnetometer), and the magnetic property data of example 2 and comparative examples 2-1, 2-2, and 2-3 at room temperature (20 ℃ C.) and 200 ℃ C. are shown in Table 2.

TABLE magnetic Performance data at 220 ℃ and 200 ℃ for example 2 and comparative example

The composition of the magnet prepared in example 2 was the same as that of the magnet prepared in comparative example 2-1, and it is understood from the data in Table 2 that the magnetic properties of the magnet prepared by the method of the present invention are slightly superior to those of the magnet prepared in comparative example 2-1. Under the same usage amount of heavy rare earth elements, the temperature coefficient of remanence of the magnet prepared in the example 2 is-0.0198%/DEG C within the temperature range of 20-200 ℃, and the temperature coefficient of remanence of the magnet prepared in the comparative example 2-1 is-0.0267%/DEG C within the temperature range of 20-200 ℃. The temperature coefficient of remanence of the magnet prepared by the method is obviously superior to that of the magnet prepared by the comparative example 2-1 in the temperature range of 20-200 ℃.

Comparative example 2-2 the residual magnetism temperature coefficient of the magnet was optimized by further increasing the contents of heavy rare earths Dy and Gd in the magnet, the Dy/Gd content in example 2 being 14% by mass; the temperature coefficient of remanence at 20-200 degree is-0.0198%/degree, the Dy/Gd content in comparative example 2-2 is 17% by mass, 20-200 degree, the temperature coefficient of remanence is-0.0211%/degree, higher than that in the example. The magnetic properties of the magnet obtained in comparative example 2-2 were significantly lower than those of example 2. This shows that the residual magnetism temperature coefficient of the magnet can be reduced by increasing the content of heavy rare earth Dy and Gd, but the magnetic performance of the prepared magnet is lower, and the content of heavy rare earth is increased, so that the cost is greatly increased. The preparation method can prepare the magnet with lower temperature coefficient of remanence, and the magnet has higher magnetic performance and less content of heavy rare earth.

Comparative examples 2 to 3 in which both Dy and Gd were replaced with Sm without adding a heavy rare earth element, it can be seen from table 1 that, although the magnetic properties of the magnets prepared in comparative examples 2 to 3 were slightly superior to those of example 2, the temperature coefficient of remanence of comparative examples 2 to 3 was-0.0316%/° c within the temperature range of 20 to 200 ℃, which is significantly inferior to that of the magnets prepared in example 2. This indicates that the prepared magnet has a high temperature coefficient of remanence without adding heavy rare earth, which is not favorable for preparing a magnet with a low temperature coefficient of remanence.

It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.