Method for increasing the coercivity of samarium-cobalt permanent magnets and use

Abstract

The application discloses a method for improving coercivity of a samarium-cobalt permanent magnet and application. The method comprises the following steps: obtaining magnetic powder by ball milling of medium crushed powder through a planetary ball mill; wherein, an included angle between a rotation plane of the planetary ball mill and a horizontal plane is adjusted to be 5-85 DEG, or the rotation plane and a ball mill tank of the planetary ball mill are simultaneously adjusted, so that an included angle between a rotation shaft of the planetary ball mill and the horizontal plane is 5-85 DEG, or the rotation plane of the planetary ball mill is kept in a horizontal plane, and an included angle between a central axis of the ball mill tank and the rotation shaft of the planetary ball mill is adjusted to be 5-85 DEG. The method can improve the coercivity of the obtained samarium-cobalt permanent magnet.

Description

Technical Field

[0001] This invention relates to a method and application for improving the coercivity of samarium cobalt permanent magnets. Background Technology

[0002] Currently, rare earth permanent magnet materials have evolved to the third generation. These three generations are categorized as follows: 1:5 samarium cobalt permanent magnets (first generation); 2:17 samarium cobalt permanent magnets (second generation); and neodymium iron boron (NdFeB) permanent magnets (third generation). The emergence of NdFeB, a third-generation rare earth permanent magnet with superior magnetic properties, in the 1980s slowed the development of the samarium cobalt permanent magnet industry. In recent years, with the rapid development of emerging industries such as aerospace, rail transportation, high-power propulsion, 5G base stations, and precision instruments, samarium cobalt permanent magnets have become irreplaceable in these specialized applications due to their excellent magnetic properties, high Curie temperature, low temperature coefficient, strong corrosion resistance, and oxidation resistance.

[0003] The preparation of samarium-cobalt permanent magnet materials primarily employs powder metallurgy, a process involving numerous steps and a lengthy workflow. Material properties are highly dependent on the overall process, particularly the powder morphology and flowability, which directly influence subsequent processes and decisively impact material quality and magnetic properties. Ideally, the powder should possess good flowability, a smooth surface without sharp edges, and low impurity content. Currently, there are two methods for preparing samarium-cobalt permanent magnet alloy powder: air jet milling and ball milling. Air jet milling accelerates alloy particles to supersonic speeds using compressed gas, causing particle collisions and breakage. The resulting powder has irregular shapes and sharp edges, increasing friction between particles and reducing flowability, thus affecting the orientation during magnetic field formation. Furthermore, the stress generated by collisions enhances powder activity, making it more susceptible to oxidation. Both of these factors increase the difficulty of material preparation and negatively impact product performance and quality. Therefore, air jet milling has inherent and insurmountable drawbacks. Ball milling is a method of pulverizing materials by using anhydrous ethanol or other organic media as a protective layer and spherical grinding media, utilizing the impact and friction of the balls on the material. Traditional ball milling methods typically employ either horizontal or vertical rotation. Horizontal rotation is generally performed on a grinding table, while vertical rotation is typically achieved using a planetary ball mill. The disadvantages of these two methods are that the movement trajectory of the balls and materials is singular, primarily occurring on a horizontal or vertical plane. This also easily leads to powder accumulation on the inner wall or bottom of the mill jar, resulting in poor powder shaping ability and low grinding efficiency.

[0004] CN106057390A discloses a method for preparing samarium-cobalt permanent magnets to improve their overall magnetic properties. The method includes: melting pre-mixed raw materials containing samarium, cobalt, iron, copper, and zirconium; refining the mixture at a constant temperature; and then rapidly cooling it to obtain a samarium-cobalt alloy ingot. The samarium-cobalt alloy ingot is then coarsely crushed into coarse particles. A portion of the coarse particles is further pulverized using a ball mill to obtain ball-milled powder. Another portion of the coarse particles is further pulverized using an air jet mill to obtain air-jet milled powder. The air-jet milled powder and the ball-milled powder are mixed uniformly to obtain a mixed magnetic powder. The mixed magnetic powder is oriented and pressed into shape under a magnetic field, and then subjected to cold isostatic pressing to obtain a samarium-cobalt blank. The samarium-cobalt blank is then vacuum pre-sintered, sintered with inert gas, cooled to solidify, and air-cooled to room temperature to obtain a sintered blank. Finally, an aging treatment is performed to obtain a samarium-cobalt permanent magnet. This patent document mixes air-jet milled powder and ball-milled powder to improve the overall magnetic properties of the samarium-cobalt permanent magnet.

[0005] CN116705488A discloses a high-performance samarium cobalt magnet and its preparation method, comprising: selecting Sm, Fe, Cu, Zr, and Co as raw materials to prepare a steel ingot; coarsely crushing and pulverizing the steel ingot to obtain alloy powder with a particle size of 3.6–3.7 micrometers; pressing the alloy powder to obtain a compact; subjecting the compact to a first sintering heat treatment and a second sintering heat treatment to obtain a blank, wherein the sintering temperature of the second sintering heat treatment is 3–5°C higher than the sintering temperature of the first sintering heat treatment; and then tempering the blank to obtain the samarium cobalt magnet. This patent document improves the magnetic properties of the obtained samarium cobalt magnet by modifying the heat treatment process.

[0006] CN116504477A discloses a method for improving the coercivity of samarium-cobalt magnets through rapid heating and cooling pretreatment, comprising: melting metal raw materials in a vacuum induction furnace according to a certain ratio to obtain an ingot; crushing the ingot to obtain alloy powder; molding the alloy powder in a magnetic field, followed by cold isostatic pressing to obtain a green blank; sintering the green blank and performing solution treatment to obtain a sintered magnet; heating the sintered magnet to 400-800°C in a heat treatment furnace at a certain heating rate, holding it at that temperature, and then cooling it to room temperature at a certain cooling rate; and aging the sintered magnet and then cooling it to room temperature to obtain a samarium-cobalt magnet. Summary of the Invention

[0007] One object of the present invention is to provide a method for improving the coercivity of samarium cobalt permanent magnets, which can improve the coercivity of the obtained samarium cobalt permanent magnets. Furthermore, the obtained samarium cobalt permanent magnets have better overall magnetic properties. Another object of the present invention is to provide the use of magnetic powder obtained by ball milling with an adjusted rotation angle of a planetary ball mill in improving the coercivity of samarium cobalt permanent magnets. The present invention achieves the above objects using the following technical solutions.

[0008] On one hand, the present invention provides a method for improving the coercivity of samarium cobalt permanent magnets, comprising the following steps:

[0009] Magnetic powder is obtained by ball milling medium-sized crushed powder using a planetary ball mill; among which...

[0010] Adjust the angle between the rotating plane of the planetary ball mill and the horizontal plane to 5–85°, or simultaneously adjust the rotating plane of the planetary ball mill and the grinding jar so that the angle between the rotating axis of the planetary ball mill and the horizontal plane is 5–85°, or keep the rotating plane of the planetary ball mill horizontal and adjust the angle between the central axis of the grinding jar and the rotating axis of the planetary ball mill to 5–85°.

[0011] According to the method of the present invention, preferably, when the rotating plane of the planetary ball mill is horizontal, the inclination of the grinding jar is adjusted so that the angle between the central axis of the grinding jar and the rotating axis of the planetary ball mill is 15 to 75°.

[0012] According to the method of the present invention, preferably, the rotation plane of the planetary ball mill and the inclination of the grinding jar are adjusted simultaneously, so that the angle between the rotation axis of the planetary ball mill and the horizontal plane is 15 to 75°.

[0013] According to the method of the present invention, preferably, during ball milling, three types of grinding balls—small, medium, and large—are selected and mixed according to their diameter; the small grinding balls have a diameter of 3–8 mm and their weight accounts for 40–60% of the total weight of the grinding balls; the medium grinding balls have a diameter of 5–10 mm and their weight accounts for 20–50% of the total weight of the grinding balls; and the large grinding balls have a diameter of 8–20 mm and their weight accounts for 10–30% of the total weight of the grinding balls.

[0014] According to the method of the present invention, preferably, the milling media are selected from one or more of anhydrous ethanol, petroleum ether, and aviation gasoline.

[0015] According to the method of the present invention, preferably, the ball-to-material ratio is 6:1 to 4:1, the ball milling speed is 100 to 400 r / min, and the ball milling time is 1 to 10 h.

[0016] According to the method of the present invention, preferably, it further includes the following steps: shaping and isostatically pressing the obtained magnetic powder to obtain a compact; placing the obtained compact in a sintering furnace for heat treatment to obtain a samarium cobalt permanent magnet.

[0017] According to the method of the present invention, preferably, the samarium cobalt permanent magnet has the chemical formula Sm x Co y Fe z Cu q Zr bal In the formula, x, y, z, q, and bal represent the mass percentage of the corresponding elements, where x + y + z + q + bal = 100%.

[0018] The method according to the present invention preferably further includes the following steps:

[0019] (1) The metal alloy is batched according to the mass percentage of the elements in the general chemical formula;

[0020] (2) The metal alloy prepared in step (1) is placed in a vacuum induction melting furnace for melting to obtain an alloy ingot;

[0021] (3) The alloy ingot obtained in step (2) is coarsely crushed by a medium crusher to obtain the medium crushed powder.

[0022] On the other hand, the present invention also provides the use of magnetic powder obtained by ball milling by adjusting the rotation angle of a planetary ball mill in improving the coercivity of samarium cobalt permanent magnets, comprising the following steps:

[0023] Magnetic powder is obtained by ball milling medium-sized crushed powder using a planetary ball mill; among which...

[0024] Adjust the angle between the rotating plane of the planetary ball mill and the horizontal plane to 5–85°, or simultaneously adjust the rotating plane of the planetary ball mill and the grinding jar so that the angle between the rotating axis of the planetary ball mill and the horizontal plane is 5–85°, or keep the rotating plane of the planetary ball mill horizontal and adjust the angle between the central axis of the grinding jar and the rotating axis of the planetary ball mill to 5–85°.

[0025] This invention obtains ball-milled magnetic powder by adjusting the rotation angle of a planetary ball mill. This magnetic powder improves the coercivity of the resulting samarium cobalt permanent magnets, resulting in magnets with better overall magnetic properties. This invention believes that the magnetic powder obtained by this method has better shaping effect, which is beneficial for improving the coercivity of the samarium cobalt permanent magnets, and this method can also improve ball milling efficiency. This invention changes the rotation angle of the planetary ball mill by adjusting the traditional vertical rotation ball milling method (i.e., the angle between the rotation plane and the horizontal plane is 90°). The method of this invention is simple, has good process stability, and is conducive to widespread application. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0027] As described in the background section, in traditional ball milling, the movement trajectory of the grinding balls and materials is singular, primarily occurring in a horizontal or vertical plane. This easily leads to powder accumulation on the inner wall or bottom of the mill jar, resulting in poor powder shaping ability and low grinding efficiency. This invention unexpectedly discovers that by changing the rotation angle of the planetary ball mill, the movement trajectory of the balls and materials is altered, creating a spiral collision and grinding pattern. This increases the relative rotational effect between the grinding balls and the powder, while simultaneously generating a spiral upward vortex, reducing powder accumulation on the inner wall and bottom of the mill jar. This achieves highly efficient grinding and shaping of the powder, and such powder (i.e., the magnetic powder obtained from ball milling) is beneficial for improving the coercivity of samarium cobalt permanent magnets. This is not a conventional choice.

[0028] In this invention, the plane of rotation is defined as follows: the plane formed by rotating around the axis of rotation of the planetary ball mill at a certain angle is called the plane of rotation, and the plane of rotation is perpendicular to the axis of rotation.

[0029] <Methods to improve the coercivity of samarium cobalt permanent magnets>

[0030] The method for improving the coercivity of samarium cobalt permanent magnets according to the present invention includes the following steps: (1) smelting step; (2) coarse crushing step; (3) powdering step; (4) forming step; and (5) heat treatment step. In addition, it also includes a batching step. A detailed description follows.

[0031] Ingredient preparation steps

[0032] The ingredients are prepared according to the mass percentage of the elements in the general chemical formula of samarium cobalt permanent magnets.

[0033] In this invention, the general chemical formula of the samarium cobalt permanent magnet is Sm x Co y Fe z Cu q Zr bal In the formula, x, y, z, q, and bal represent the mass percentage of the corresponding elements, where x + y + z + q + bal = 100%.

[0034] In this invention, x is 24-26%, y is 56-58%, z is 6-7%, q is 6-8%, and bal is 100%-xyzq.

[0035] In some specific implementations, the metal alloy is prepared according to the mass percentage of the elements in the general chemical formula as described above. The purity of the metal elements is greater than or equal to 99.5%.

[0036] Smelting steps

[0037] The prepared metal alloy is placed in a vacuum induction melting furnace for melting to obtain an alloy ingot. The melting temperature and time can be those known in the art, and will not be elaborated here.

[0038] coarse crushing steps

[0039] The obtained alloy ingot is coarsely crushed using a medium crusher to obtain medium crushed powder.

[0040] The coarse crushing step can employ any methods known in the art, and will not be elaborated upon here. The particle size of the medium crushed powder is 20–26 μm.

[0041] Powdering steps

[0042] Magnetic powder is obtained by ball milling medium-sized powder using a planetary ball mill; wherein, the rotation angle of the planetary ball mill can be adjusted by any of the following methods:

[0043] (a) Adjust the angle between the rotating plane of the planetary ball mill and the horizontal plane to 5-85°;

[0044] (ii) Simultaneously adjust the rotating plane of the planetary ball mill and the grinding jar so that the angle between the rotating axis of the planetary ball mill and the horizontal plane is 5 to 85°.

[0045] (iii) Keep the rotating plane of the planetary ball mill horizontal and adjust the angle between the central axis of the grinding jar and the rotating axis of the planetary ball mill to 5-85°.

[0046] This can improve ball milling efficiency, and the resulting magnetic powder is beneficial for improving the coercivity of the resulting samarium cobalt permanent magnet.

[0047] In some embodiments, a planetary ball mill is used to grind medium-strength powder to obtain magnetic powder; wherein, the angle between the rotating plane of the planetary ball mill and the horizontal plane is adjusted to 5–85°. Preferably, the angle between the rotating plane of the planetary ball mill and the horizontal plane is adjusted to 15–75°, more preferably, the angle between the rotating plane of the planetary ball mill and the horizontal plane is adjusted to 25–65°. For example, the angle between the rotating plane of the planetary ball mill and the horizontal plane can be adjusted to 20°, 25°, 30°, 35°, 40°, 45°, 50°, or 55°. Specifically, the tilt angle of the rotating plane of the planetary ball mill is adjusted so that the angle between the rotating plane and the horizontal plane is 5–85°.

[0048] In other embodiments, a planetary ball mill is used to grind medium-sized powder into magnetic powder; wherein, the rotation plane of the planetary ball mill and the grinding jar are simultaneously adjusted so that the angle between the rotation axis of the planetary ball mill and the horizontal plane is 5–85°. Preferably, the rotation plane of the planetary ball mill and the grinding jar are simultaneously adjusted so that the angle between the rotation axis of the planetary ball mill and the horizontal plane is 15–75°. More preferably, the rotation plane of the planetary ball mill and the grinding jar are simultaneously adjusted so that the angle between the rotation axis of the planetary ball mill and the horizontal plane is 25–60°. Specifically, the tilt of the rotation plane of the planetary ball mill and the grinding jar can be adjusted simultaneously so that the angle between the rotation axis of the planetary ball mill and the horizontal plane is 5–85°.

[0049] In some further embodiments, a planetary ball mill is used to grind the medium-sized powder into magnetic powder; wherein, the plane of rotation of the planetary ball mill is kept horizontal, and the angle between the central axis of the grinding jar and the rotation axis of the planetary ball mill is adjusted to 5–85°. Preferably, the plane of rotation of the planetary ball mill is kept horizontal, and the angle between the central axis of the grinding jar and the rotation axis of the planetary ball mill is adjusted to 15–75°. More preferably, the angle between the central axis of the grinding jar and the rotation axis of the planetary ball mill is adjusted to 25–65°. Specifically, when the plane of rotation of the planetary ball mill is horizontal, the inclination of the grinding jar is adjusted so that the angle between the central axis of the grinding jar and the rotation axis of the planetary ball mill is 5–85°.

[0050] In this invention, stainless steel balls are used as grinding balls during ball milling. Three types of grinding balls—small, medium, and large—are selected and mixed according to their diameter. The small grinding balls have a diameter of 3–8 mm, preferably 3–5 mm. The weight of the small grinding balls accounts for 40–60% of the total weight of the grinding balls, preferably 45–55%. The medium grinding balls have a diameter of 5–10 mm, preferably 8–10 mm. The weight of the medium grinding balls accounts for 30–40% of the total weight of the grinding balls. The large grinding balls have a diameter of 8–20 mm, preferably 10–15 mm. The weight of the large grinding balls accounts for 10–30% of the total weight of the grinding balls, preferably 10–20%.

[0051] According to one embodiment of the present invention, the small grinding ball has a diameter of 3-4 mm and its weight accounts for 40-45% of the total weight of the grinding balls; the medium grinding ball has a diameter of 5-6 mm and its weight accounts for 40-45% of the total weight of the grinding balls; and the large grinding ball has a diameter of 8-9 mm and its weight accounts for 10-20% of the total weight of the grinding balls.

[0052] In this invention, the milling media is selected from one or more of anhydrous ethanol, petroleum ether, and aviation gasoline. Preferably, the milling media is selected from anhydrous ethanol, petroleum ether, and aviation gasoline. More preferably, the milling media is anhydrous ethanol.

[0053] In this invention, the ball-to-powder ratio (i.e., the mass ratio of grinding balls to medium-crushed powder) can be 6:1 to 4:1, preferably 5:1 to 4:1. The ball milling speed can be 100 to 400 r / min, preferably 200 to 350 r / min, more preferably 250 to 320 r / min. The ball milling time is 1 to 10 h, preferably 3 to 10 h, more preferably 4 to 8 h.

[0054] In this invention, the particle size of the obtained magnetic powder is 5-10 μm.

[0055] The magnetic powder obtained by ball milling can help improve the coercivity of the resulting samarium cobalt permanent magnet without reducing its remanence and energy product.

[0056] In this invention, there are no particular restrictions on the manufacturer and model of the planetary ball mill; those known in the art can be used.

[0057] Molding steps

[0058] The obtained magnetic powder is shaped, oriented, and isostatically pressed to obtain a compact.

[0059] The specific operating conditions for molding orientation and isostatic pressing can be those known in the art, and will not be elaborated here.

[0060] Heat treatment steps

[0061] The obtained compact is placed in a sintering furnace for heat treatment to obtain samarium cobalt permanent magnets.

[0062] Specifically, the heat treatment sequentially includes sintering, solution treatment, and aging steps. The sintering temperature can be 1150–1250℃, preferably 1180–1230℃, and more preferably 1200–1230℃. The sintering time is 1–3 hours, preferably 2–3 hours. The solution treatment temperature can be 1120–1190℃, preferably 1140–1190℃. The solution treatment time is 1–5 hours, preferably 2–5 hours, and more preferably 3–4 hours. The aging temperature can be 800–850℃, preferably 820–850℃. The aging time is 10–15 hours, preferably 12–15 hours.

[0063] According to one embodiment of the present invention, a method for improving the coercivity of a samarium cobalt permanent magnet includes the following steps:

[0064] (1) The metal alloy is prepared according to the mass percentage of the elements in the general chemical formula of samarium cobalt permanent magnets;

[0065] (2) The prepared metal alloy is placed in a vacuum induction melting furnace for melting to obtain an alloy ingot;

[0066] (3) The obtained alloy ingot is coarsely crushed by a medium crusher to obtain the medium crushed powder;

[0067] (4) Magnetic powder is obtained by ball milling medium-sized crushed powder using a planetary ball mill; wherein...

[0068] Adjust the angle between the rotating plane of the planetary ball mill and the horizontal plane to 5–85°, or simultaneously adjust the rotating plane of the planetary ball mill and the grinding jar so that the angle between the rotating axis of the planetary ball mill and the horizontal plane is 5–85°, or keep the rotating plane of the planetary ball mill horizontal and adjust the angle between the central axis of the grinding jar and the rotating axis of the planetary ball mill to 5–85°.

[0069] (5) The obtained magnetic powder is shaped, oriented, and isostatically pressed to obtain a compact;

[0070] (6) The obtained compact is placed in a sintering furnace for heat treatment to obtain samarium cobalt permanent magnets.

[0071] In this invention, a low-oxygen powder metallurgy method is used, and the low oxygen level can be controlled by methods known in the art.

[0072] <Application>

[0073] The present invention also provides the use of magnetic powder obtained by ball milling by adjusting the rotation angle of a planetary ball mill in improving the coercivity of samarium cobalt permanent magnets, comprising the following steps:

[0074] Magnetic powder is obtained by ball milling medium-sized crushed powder using a planetary ball mill; among which...

[0075] Adjust the angle between the rotating plane of the planetary ball mill and the horizontal plane to 5–85°, or simultaneously adjust both the rotating plane of the planetary ball mill and the grinding jar so that the angle between the rotating axis of the planetary ball mill and the horizontal plane is 5–85°, or keep the rotating plane of the planetary ball mill horizontal and adjust the angle between the central axis of the grinding jar and the rotating axis of the planetary ball mill to 5–85°. Detailed descriptions are provided above and will not be repeated here.

[0076] <Analytical Methods>

[0077] The change in magnetization intensity is measured by hysteresis loop, i.e., the magnetization intensity measurement method is used to obtain the remanence, coercivity, and magnetic energy product of samarium cobalt permanent magnets.

[0078] In the following embodiments, the planetary ball mill used is manufactured by Changsha Miqi and its model is XH-XQM4L.

[0079] Example 1

[0080] Ingredients: Metal alloys with the general chemical formula Smx Co y Fe z Cu q Zr bal Ingredients. In the formula, x, y, z, q, and bal represent the mass percentage of the corresponding elements, where x + y + z + q + bal = 100%. In this embodiment, x = 25.5%, y = 56.9%, z = 6.7%, q = 7%, and bal = 3.9%.

[0081] Melting: The prepared metal alloy is placed in a crucible of a vacuum induction melting furnace. After processes such as vacuuming, argon filling, and heating, the alloy components are completely melted to form an alloy ingot.

[0082] Coarse crushing: The obtained alloy ingot is coarsely crushed using a medium crusher to obtain medium crushed powder. The particle size of the medium crushed powder is 21.34 μm.

[0083] Powder Preparation: The medium-sized crushed powder was ball-milled using a planetary ball mill. Before ball milling, the rotation plane of the planetary ball mill was adjusted to form a 25° angle with the horizontal plane. Stainless steel grinding balls were used, with diameters of 3mm, 5mm, and 8mm. Based on the total weight of the grinding balls, the small grinding balls accounted for 45wt%, the medium grinding balls for 35wt%, and the large grinding balls for 20wt%. Anhydrous ethanol was used as the grinding media. The grinding balls, grinding media, and medium-sized crushed powder were added to the ball mill jar and ball-milled at a ball-to-powder ratio of 4:1, a milling speed of 250 r / min, and a milling time of 4 hours to obtain magnetic powder. The particle size of the magnetic powder was 6.7μm.

[0084] Molding: The magnetic powder is oriented and isostatically pressed to obtain a compact.

[0085] Heat treatment: The obtained compact was placed in a sintering furnace for heat treatment, which included sintering, solution treatment, and aging. The sintering temperature was 1200℃ for 2 hours; the solution treatment temperature was 1175℃ for 2 hours; and the aging temperature was 825℃ for 15 hours. Samarium cobalt permanent magnets were obtained. Performance tests are shown in Table 1.

[0086] Example 2

[0087] The only difference from Example 1 is the powder preparation step.

[0088] In this embodiment, before ball milling, the rotation plane of the planetary ball mill is adjusted to form a 45° angle with the horizontal plane. The grinding balls used are stainless steel balls with diameters of 5mm, 8mm, and 15mm. Based on the total weight of the grinding balls, the small grinding balls account for 50wt%, the medium grinding balls for 30wt%, and the large grinding balls for 20wt%. The ball-to-material ratio is 5:1, the ball milling speed is 300 r / min, and the ball milling time is 6 hours. Magnetic powder is obtained. The particle size of the magnetic powder is 6.1 μm.

[0089] The performance test results of the samarium cobalt permanent magnet obtained in this embodiment are shown in Table 1.

[0090] Example 3

[0091] The only difference from Example 1 is the powder preparation step.

[0092] In this embodiment, before ball milling, the rotation plane of the planetary ball mill is adjusted to form a 55° angle with the horizontal plane. The grinding balls used are stainless steel balls with diameters of 8mm, 10mm, and 15mm. Based on the total weight of the grinding balls, the small grinding balls account for 55wt%, the medium grinding balls for 35wt%, and the large grinding balls for 10wt%. The ball-to-material ratio is 5:1, the ball milling speed is 320 r / min, and the ball milling time is 8 hours. Magnetic powder is obtained. The particle size of the magnetic powder is 5.6μm.

[0093] The performance test results of the samarium cobalt permanent magnet obtained in this embodiment are shown in Table 1.

[0094] Table 1

[0095]

[0096] The coercivity of existing samarium cobalt permanent magnets is generally around 35 kOe. Therefore, the method of the present invention is beneficial to improving the coercivity of the obtained samarium cobalt permanent magnets without significantly reducing remanence and energy product.

[0097] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A method for improving the coercivity of samarium cobalt permanent magnets, characterized in that, The general chemical formula of the samarium cobalt permanent magnet is Sm x Co y Fe z Cu q Zr bal In the formula, x, y, z, q, and bal represent the mass percentage of the corresponding elements, where x is 24-26%, y is 56-58%, z is 6-7%, q is 6-8%, and bal is 100%-xyzq. The method includes the following steps: The alloy ingot is coarsely crushed using a medium crusher to obtain medium crushed powder; the particle size of the medium crushed powder is 20-26 μm. Magnetic powder is obtained by ball milling medium-sized crushed powder using a planetary ball mill; among which... Adjust the angle between the rotating plane of the planetary ball mill and the horizontal plane to 25–55°; select three types of grinding balls—small, medium, and large—according to their diameter and mix them; the small grinding balls have a diameter of 3–8 mm and account for 40–60% of the total weight of the grinding balls; the medium grinding balls have a diameter of 5–10 mm and account for 20–50% of the total weight of the grinding balls; the large grinding balls have a diameter of 8–20 mm and account for 10–30% of the total weight of the grinding balls; the grinding media are selected from one or more of anhydrous ethanol, petroleum ether, and aviation gasoline; the ball-to-material ratio is 6:1–4:1, the ball mill speed is 200–400 r / min, and the ball milling time is 3–10 h; The particle size of the obtained magnetic powder is 5–10 μm.

2. The method according to claim 1, characterized in that, It also includes the following steps: The obtained magnetic powder is shaped, oriented, and isostatically pressed to obtain a compact; the obtained compact is then placed in a sintering furnace for heat treatment to obtain a samarium cobalt permanent magnet.

3. The method according to claim 1, characterized in that, It also includes the following steps: (1) The metal alloy is batched according to the mass percentage of the elements in the general chemical formula; (2) The metal alloy prepared in step (1) is placed in a vacuum induction melting furnace for melting to obtain the alloy ingot.

4. The use of magnetic powder obtained by ball milling by adjusting the rotation angle of a planetary ball mill in improving the coercivity of samarium cobalt permanent magnets, characterized in that... The general chemical formula of the samarium cobalt permanent magnet is Sm x Co y Fe z Cu q Zr bal In the formula, x, y, z, q, and bal represent the mass percentage of the corresponding elements, where x is 24-26%, y is 56-58%, z is 6-7%, q is 6-8%, and bal is 100%-xyzq. Includes the following steps: The alloy ingot is coarsely crushed using a medium crusher to obtain medium crushed powder; the particle size of the medium crushed powder is 20-26 μm. Magnetic powder is obtained by grinding medium-sized powder using a planetary ball mill. The angle between the rotating plane of the planetary ball mill and the horizontal plane is adjusted to 25–55°. Three types of grinding balls—small, medium, and large—are selected and mixed according to their diameter. Small grinding balls have a diameter of 3–8 mm and account for 40–60% of the total weight; medium grinding balls have a diameter of 5–10 mm and account for 20–50% of the total weight; and large grinding balls have a diameter of 8–20 mm and account for 10–30% of the total weight. The grinding media are selected from one or more of anhydrous ethanol, petroleum ether, and aviation gasoline. The ball-to-powder ratio is 6:1–4:1, the milling speed is 200–400 r / min, and the milling time is 3–10 h. The particle size of the obtained magnetic powder is 5–10 μm.

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