Rare earth permanent magnets and methods for manufacturing the same, and electrical equipment

Abstract

The present invention provides a rare-earth permanent magnet with good demagnetizing properties, a method for manufacturing the same, and a built-in rare-earth permanent magnet electric machine. [Solution] The rare earth permanent magnet contains light rare earth elements and heavy rare earth elements, the light rare earth elements must contain Nd, and the heavy rare earth elements must contain Dy and Tb. Along the width direction, there are two initial peripheral portions A1 and one initial central portion A2, the two peripheral portions are located on either side of the central portion and are symmetrical with respect to the central axis of the central portion, the peripheral portions have an outer edge and an inner edge, the outer edge is farther from the central portion and the inner edge is closer to the central portion, along the direction of the central axis from the outer edge of the peripheral portion toward the central portion, the weight percentage of Dy gradually increases and the weight percentage of Tb gradually decreases, and the average value of the coercivity of the peripheral portions is greater than the average value of the coercivity of the central portion.

Description

[Technical Field]

[0001] This invention relates to a rare-earth permanent magnet, a method for manufacturing the same, and an electric machine containing the rare-earth permanent magnet. [Background technology]

[0002] Conventionally, R2Fe 14 R-Fe-B rare earth sintered magnets, with B as the main phase, are high-performance permanent magnets and are mainly used in voice coil motors for hard disk drivers, motors for hybrid vehicles, and various home appliances.

[0003] The demagnetism resistance of an electrical device refers to its ability to be affected by external magnetic fields during its operation. Generally speaking, the higher the demagnetism resistance of an electrical device, the greater its stability and reliability. The strength of an electrical device's demagnetism resistance is closely related to the materials used. For example, in the case of permanent magnet electrical devices, the coercivity of the permanent magnetic material is an important factor affecting its demagnetism resistance.

[0004] To adapt to high-temperature operating environments, rare-earth permanent magnetic materials require excellent heat resistance and high coercivity.

[0005] CN113506665A discloses a method for increasing the coercivity of bonded neodymium iron boron magnets by efficient diffusion, which includes coating the edges of bonded neodymium iron boron magnets with a grain boundary diffuser containing heavy rare earth elements, light rare earth elements, or no rare earth elements, and then heat-treating the magnets. The coercivity of the magnets obtained by this method still needs improvement.

[0006] CN115732215A discloses a method for producing a bonded neodymium iron boron magnetic material with low demagnetization, which includes laser treatment of a sintered bonded neodymium iron boron magnetic material to obtain a pre-treated bonded neodymium iron boron magnetic material, forming a heavy rare earth film on the surface of the pre-treated bonded neodymium iron boron magnetic material by magnetron sputtering to obtain a heavy rare earth bonded neodymium iron boron magnetic material, where the heavy rare earth film is prepared from heavy rare earth elements and auxiliary elements, and sequentially performing vacuum diffusion, laser weight removal and electroplating treatments on the heavy rare earth bonded neodymium iron boron magnetic material to obtain a bonded neodymium iron boron magnetic material with low demagnetization.

[0007] CN111653404A discloses a bonded neodymium iron boron magnet with the chemical formula R1-R2-Fe-MB, which has a composite structure having a high coercivity region and a high remanent magnetic flux density region, where R1 is a rare earth element containing at least Nd, R2 is a heavy rare earth element containing at least Dy and / or Tb, and M is a transition metal element containing at least Co, and the bonded neodymium iron boron magnet has a high coercivity region with a high R2 content and a region with a high remanent magnetic flux with a low R2 content, where R2 forms a film on two opposing surfaces of the matrix magnet surface of the R1-Fe-MB base structure, and the two opposing surfaces are not perpendicular to the magnetization direction of the magnet and are not perpendicular to the pressing direction when the magnet is formed, and the direction not perpendicular to the magnetization direction of the magnet and the pressing direction when the magnet is formed are not the same direction. This makes it possible to reduce the amount of heavy rare earth elements used and prevent the occurrence of thermal demagnetization at high temperatures. [Overview of the project]

[0008] One object of the present invention is to provide a rare-earth permanent magnet with good demagnetizing properties. This magnet is suitable for built-in rare-earth permanent magnet electrical equipment. Another object of the present invention is to provide a method for manufacturing such a rare-earth permanent magnet. Yet another object of the present invention is to provide electrical equipment. To achieve the above objects, the present invention employs the following configuration.

[0009] On the other hand, the present invention contains a light rare earth element and a heavy rare earth element, wherein the light rare earth element essentially contains Nd, and the heavy rare earth element essentially contains Dy and Tb, and R2Fe 14 B is the main phase, where R is a rare earth element. Along the width direction, the rare-earth permanent magnet has two peripheral portions and one central portion, with the two peripheral portions located on either side of the central portion and symmetrical with respect to the central axis of the central portion. The periphery has an outer periphery and an inner periphery, the outer periphery is farther from the central part, and the inner periphery is closer to the central part. Along the direction of the central axis from the outer periphery toward the central part, the weight percentage of Dy gradually increases, and the weight percentage of Tb gradually decreases. This invention provides a rare-earth permanent magnet in which the average coercivity of the peripheral region is greater than the average coercivity of the central region.

[0010] In the rare-earth permanent magnet according to the present invention, preferably, the length of the edge portion is the same as the length of the central portion, and the width of the central portion is greater than the sum of the widths of the two edge portions.

[0011] In the rare-earth permanent magnet according to the present invention, preferably, the difference between the minimum coercivity at the edge and the minimum coercivity at the center exceeds 60 kA / m.

[0012] In the rare-earth permanent magnet according to the present invention, preferably, along the direction of the central axis from the outer edge of the periphery toward the center, the maximum weight percentage of Dy is less than 2 wt%, the minimum weight percentage of Dy is greater than 0.03 wt%, the maximum weight percentage of Tb is less than 1 wt%, and the minimum weight percentage of Tb is less than 0.05 wt%.

[0013] In the rare earth permanent magnet according to the present invention, preferably, the light rare earth element further contains Pr, and the content of the rare earth element R is 29 wt% or more based on the total weight of the rare earth permanent magnet.

[0014] On the other hand, the present invention involves the following steps: (1) R2Fe 14The magnet provides a sintered bonded neodymium iron boron magnet, with B as the main phase, having two initial peripheral portions and one initial central portion along the width direction, with the two initial peripheral portions located on either side of the initial central portion and symmetrical with respect to the central axis of the initial central portion, where R is a rare earth element. (2) Along the orientation direction, the terbium-containing material is attached to one of the initial peripheral surfaces and dried, and then the dysprosium-containing material is attached to one of the initial central surfaces and dried to obtain the first attached body. (3) Along the orientation direction, a terbium-containing material is attached to the other surface of the initial peripheral portion of the first attachor, dried, and then a dysprosium-containing material is attached to the other surface of the initial central portion, dried, to obtain a second attachor. (4) The second attachment is heat-treated to obtain the rare earth permanent magnet, where the initial peripheral portion is formed corresponding to the peripheral portion, and the initial central portion is formed corresponding to the central portion. The present invention provides a method for manufacturing the above-mentioned rare earth permanent magnet, including the above-mentioned method.

[0015] In the manufacturing method according to the present invention, preferably, step (1) includes the sintered bonded neodymium iron boron magnet, where R is a rare earth element and contains Nd and Pr.

[0016] In the manufacturing method according to the present invention, preferably, in step (1), the sintered bonded neodymium iron boron magnet contains the following composition, based on the total weight of the sintered bonded neodymium iron boron magnet: PrNd 28~32 wt%, B 0.89~0.98 wt%, Dy 0.01~1.15wt%, Cu 0.01~0.25 wt%, Co 0.01~1.85 wt%, Ga 0.01~0.30 wt%, M 0.01~0.20 wt%, and Fe remainder, Here, M is at least one selected from Ti, Zr, Mo, and Nb. Here, the weight ratio of Pr to Nd is 1:3 to 1:4.

[0017] In the manufacturing method according to the present invention, preferably, in step (2), the drying temperature is all 120 to 200 °C, the weight gain rate of terbium is 0.075 to 0.25 wt%, the weight gain rate of dysprosium is 0.2 to 0.425 wt%, and in step (3), the drying temperature is all 120 to 200 °C, the weight gain rate of terbium is 0.075 to 0.25 wt%, and the weight gain rate of dysprosium is 0.2 to 0.425 wt%.

[0018] On the other hand, the present invention provides an electric machine including the above rare earth permanent magnet, where the attenuation rate α of the back electromotive force of the electric machine is less than 0.5%, and α is calculated by adopting the following formula: α = (V0 - V t ) / V0 × 100%, where V0 is the back electromotive force at room temperature in the initial state, and V t is the back electromotive force when returning to room temperature after the high-temperature load experiment. The rare earth permanent magnet according to the present invention has good demagnetization resistance and is suitable for an internal rare earth permanent magnet electric machine. The manufacturing method of the present invention can obtain a rare earth permanent magnet having a specific coercive force distribution and good demagnetization resistance. The reproducibility of the process of the present invention is good.

Brief Description of the Drawings

[0019] [Figure 1] FIG. 1 is a schematic view of the initial edge portion and the initial central portion of the sintered bonded neodymium iron boron magnet of the present invention. A1 represents the initial edge portion, and A2 represents the initial central portion.

Embodiments for Carrying Out the Invention

[0020] Hereinafter, the present invention will be further described with specific examples, but the scope of the present invention is not limited thereto.

[0021] The term "coercivity" as used in this invention, also known as intrinsic coercivity, refers to the magnetic field strength at which the magnetization strength decreases monotonically from the saturation magnetization state of a magnet to zero and then increases again, decreasing along the saturation hysteresis curve until it reaches zero. cj Alternatively, it is denoted as MHc, with units of oorsted (Oe) or amperes per meter (A / m). 1 Oe = 79.6 A / m. cj This is the intrinsic coercivity at room temperature.

[0022] The term "residual magnetic flux density" as used in this invention refers to the numerical value of the magnetic flux density corresponding to the case where the magnetic field strength is zero in the saturation hysteresis curve, and is usually denoted as Br or Mr, with units of Tesla (T) or Gauss (Gs).

[0023] In this invention, the term "inert gas" includes helium, neon, argon, krypton, and xenon. "Inert gas" refers to an atmosphere consisting of an inert gas that does not affect the performance of the magnet.

[0024] <Rare Earth Permanent Magnets> The rare earth permanent magnet in this invention contains a light rare earth element and a heavy rare earth element, wherein the light rare earth element essentially contains Nd, and the heavy rare earth element essentially contains Dy and Tb, and R2Fe 14 B is the main phase. Here, R represents a rare earth element. In one embodiment, R represents a light rare earth element. The light rare earth element further contains Pr. The weight ratio of Pr to Nd is 1:3 to 1:4. Based on the total weight of the rare earth permanent magnet, the content of the rare earth element R is 29 wt% or more, preferably 30 wt% or more, and more preferably 31 wt% or more and 33 wt% or less.

[0025] The rare-earth permanent magnet in this invention may have a hexahedral structure and has two marginal portions and one central portion. The two marginal portions are located on either side of the central portion and are symmetrical with respect to the central axis of the central portion.

[0026] In one embodiment, the rare-earth permanent magnet has a rectangular parallelepiped structure. The length of the rare-earth permanent magnet is longer than its width. The length of the edges is the same as the length of the central part. The width of the central part is greater than the sum of the widths of the two edges. The width of the edges may be 1.5 to 3.5 mm. The width of the central part may be 6 to 20 mm. In one specific embodiment, the width of the edges is 2 to 3.1 mm, and the width of the central part is 10 to 15 mm. In the present invention, the thickness of the rare-earth permanent magnet may be 1.5 to 6.5 mm, preferably 2.5 to 5.5 mm, and more preferably 3 to 5.0 mm. The orientation direction is along the thickness.

[0027] The periphery has an outer periphery and an inner periphery, with the outer periphery being far from the central part and the inner periphery being close to the central part. In one embodiment, the boundary between the inner periphery and the central part is clear. In other embodiments, the boundary between the inner periphery and the central part is not clear. There is a partial fusion between the inner periphery and the central part.

[0028] Along the direction of the central axis from the outer edge of the periphery toward the center, the weight percentage of Dy gradually increases, while the weight percentage of Tb gradually decreases.

[0029] Preferably, the maximum weight percentage of Dy is less than 1.5 wt% along the direction of the central axis from the outer edge of the periphery toward the center. More preferably, the maximum weight percentage of Dy is less than 1 wt% along the direction of the central axis from the outer edge of the periphery toward the center. In one specific embodiment of the present invention, the minimum weight percentage of Dy is greater than 0.5 wt% and the maximum weight percentage of Dy is less than 2 wt% along the direction of the central axis from the outer edge of the periphery toward the center.

[0030] Along the direction of the central axis from the outer edge of the edge portion towards the central portion, the maximum value of the weight percentage of Tb is less than 1 wt%, and the minimum value of the weight percentage of Tb is less than 0.05 wt%. Preferably, along the direction of the central axis from the outer edge of the edge portion towards the central portion, the maximum value of the weight percentage of Tb is less than 0.8 wt%. More preferably, along the direction of the central axis from the outer edge of the edge portion towards the central portion, the maximum value of the weight percentage of Tb is less than 0.7 wt%. In one specific embodiment according to the present invention, along the direction of the central axis from the outer edge of the edge portion towards the central portion, the difference between the maximum value and the minimum value of the weight percentage of Dy exceeds 0.2 wt%.

[0031] The average value of the coercivity of the edge portion is greater than the average value of the coercivity of the central portion. The difference between the minimum value of the coercivity of the edge portion and the minimum value of the coercivity of the central portion exceeds 60 kA / m, and may exceed 100 kA / m, for example, or may exceed 120 kA / m. According to one embodiment of the present invention, the minimum value of the coercivity of the edge portion is 1950 kA / m or more, and may exceed 2015 kA / m, for example. According to one embodiment of the present invention, the minimum value of the coercivity of the central portion is 1850 kA / m or more, and may exceed 1875 kA / m, for example. The present invention finds that such rare earth permanent magnets have a high residual magnetic flux density, a high coercivity, good demagnetization resistance, and are suitable for built-in rare earth permanent magnet motors.

[0032] <Manufacturing method> The present invention also provides a method for manufacturing a rare earth permanent magnet as described above, including the following steps: (1) providing an initial sintered bonded neodymium iron boron magnet, (2) obtaining a first adherent, (3) obtaining a second adherent, (4) performing heat treatment. This is advantageous for obtaining a rare earth permanent magnet having a hexahedral structure with two edge portions and a central portion as described above.

[0033] We offer initial sintered bonded neodymium iron boron magnets. R2Fe 14A sintered bonded neodymium iron boron magnet is provided, with B as the main phase. The sintered bonded neodymium iron boron magnet has a hexahedral structure. Along the width direction, it has two initial periphery portions and one initial central portion. The two initial periphery portions are located on either side of the initial central portion and are symmetrical with respect to the central axis of the initial central portion.

[0034] In the sintered bonded neodymium iron boron magnet, R is a rare earth element and includes Nd and Pr. Based on the total weight of the sintered bonded neodymium iron boron magnet, the sintered bonded neodymium iron boron magnet has the following composition: PrNd 28~32 wt%, B 0.89~0.98 wt%, Dy 0.01~1.15 wt%, Cu 0.01~0.25 wt%, Co 0.01~1.85 wt%, Ga 0.01~0.30 wt%, M 0.01~0.20 wt%, Fe remainder, where M is at least one selected from Ti, Zr, Mo, and Nb. Here, the weight ratio of Pr to Nd is 1:3~1:4. In a preferred embodiment, the sintered bonded neodymium iron boron magnet has the above composition.

[0035] Based on the total weight of the sintered bonded neodymium iron boron magnet, the PrNd content is preferably 29.0 to 31 wt%, and more preferably 29.5 to 30.5 wt%. The B content is preferably 0.93 to 0.97 wt%, and more preferably 0.94 to 0.96 wt%. The weight percentage of Dy is preferably 0.1 to 1.0 wt%, and more preferably 0.4 to 0.7 wt%. The Cu content is preferably 0.05 to 0.25 wt%, and more preferably 0.10 to 0.20 wt%. The Co content is preferably 0.1 to 1.5 wt%, more preferably 0.5 to 1.3 wt%, and more preferably 1.0 to 1.15 wt%. The Ga content is preferably 0.1 to 0.25 wt%, more preferably 0.15 to 0.23 wt%, for example, 0.18 wt% and 0.21 wt%. The M content is preferably 0.05 to 0.20 wt%, more preferably 0.10 to 0.18 wt%, and also preferably 0.15 to 0.17 wt%. M is preferably Ti.

[0036] Obtain the first attachment body. A terbium-containing material is attached to one of the initial peripheral surfaces of a sintered bonded neodymium iron boron magnet along the orientation direction, dried, and then a dysprosium-containing material is attached to one of the initial central surfaces, dried, to obtain the first attachment body. The initial peripheral surface and the initial central surface of the sintered bonded neodymium iron boron magnet are approximately coplanar.

[0037] The terbium-containing material may be applied to one of the initial edge surfaces by printing or spraying. The terbium-containing material may be terbium hydride or metallic terbium and its alloy powders. The terbium-containing material (e.g., terbium powder) may be mixed with an organic solvent to form a terbium slurry, the mass concentration of which may be 25-85 wt%, preferably 45-80 wt%, and more preferably 60-80 wt%. The organic solvent may be terpineol oil. This allows for accurate terbium application, resulting in a high adhesion rate and good reproducibility.

[0038] The controlled weight increase rate of terbium is 0.075 to 0.25 wt%, preferably 0.085 to 0.2 wt%, and more preferably 0.095 to 0.14 wt%. The weight increase rate of terbium = (weight after coating with terbium metal coating - original weight before coating with terbium metal coating) / original weight before coating with terbium metal coating × 100%. The drying temperature may be 120 to 200°C, preferably 150 to 200°C, and more preferably 180 to 190°C.

[0039] According to one embodiment of the present invention, a printing method may be used to attach terbium, and a printing device may be used when printing.

[0040] The dysprosium-containing material may be applied to one of the initial central surfaces by printing or spraying. The dysprosium-containing material may be dysprosium hydride or metallic dysprosium and its alloys. The dysprosium-containing material (e.g., dysprosium powder) may be mixed with an organic solvent to form a dysprosium slurry, the mass concentration of which may be 25-85 wt%, preferably 45-80 wt%, and more preferably 60-80 wt%. The organic solvent may be terpineol oil. This allows for accurate application of dysprosium, resulting in a high adhesion rate and good reproducibility.

[0041] The controlled weight increase rate of dysprosium is 0.2 to 0.425 wt%, preferably 0.3 to 0.325 wt%. The weight increase rate of dysprosium = (weight after coating with dysprosium metallic coating - original weight before coating with dysprosium metallic coating) / original weight before coating with dysprosium metallic coating × 100%. The drying temperature may be 120 to 200°C, preferably 150 to 200°C, and more preferably 180 to 190°C.

[0042] Obtain the second attachment body. A terbium-containing material is attached to another surface of the initial periphery of the first attachor along the orientation direction and dried, and then a dysprosium-containing material is attached to another surface of the initial central part and dried to obtain a second attachor. The second attachor is substantially coplanar with the other surface of the initial periphery and the other surface of the initial central part of the first attachor.

[0043] The first attachment can be flipped over, and terbium or dysprosium may be attached to the other side that does not have heavy rare earth elements attached. The specific steps are the same as those for obtaining the first attachment.

[0044] The terbium-containing material is attached by printing or spraying it onto another surface of the initial edge of the first adherend along the orientation direction, where the terbium-containing material may be terbium hydride or metallic terbium and its alloy powder. The terbium-containing material (e.g., terbium powder) may be mixed with an organic solvent to form a terbium slurry, the mass concentration of which may be 25-85 wt%, preferably 45-80 wt%, and more preferably 60-80 wt%. The organic solvent may be terpineol oil. This allows for accurate attachment of terbium, resulting in a high adhesion rate and good reproducibility.

[0045] The controlled weight increase rate of terbium is 0.075 to 0.25 wt%, preferably 0.085 to 0.14 wt%, and more preferably 0.095 to 0.12 wt%. The weight increase rate of terbium = (Weight of the first adsorbent after coating with terbium metal coating - Original weight of the first adsorbent before coating with terbium metal coating) / Original weight of the first adsorbent before coating with terbium metal coating × 100%. The drying temperature may be 120 to 200°C, preferably 150 to 200°C, and more preferably 180 to 190°C.

[0046] A dysprosium-containing material is attached to the other surface of the initial central portion by printing or spraying, and the dysprosium-containing material may be dysprosium hydride or metallic dysprosium and its alloy powder. The dysprosium-containing material (e.g., dysprosium powder) may be mixed with an organic solvent to form a dysprosium slurry, the mass concentration of which may be 25 to 85 wt%, preferably 45 to 80 wt%, and more preferably 60 to 80 wt%. The organic solvent may be terpineol oil.

[0047] The controlled weight increase rate of dysprosium is 0.2 to 0.425 wt%, preferably 0.3 to 0.325 wt%. The weight increase rate of dysprosium = (Weight of the first adsorbent after coating with dysprosium metallic coating - Original weight of the first adsorbent before coating with dysprosium metallic coating) / Original weight of the first adsorbent before coating with dysprosium metallic coating × 100%. The drying temperature may be 120 to 200°C, preferably 150 to 200°C, and more preferably 180 to 190°C. This allows for accurate dysprosium adhesion, resulting in a high adhesion rate and good reproducibility.

[0048] heat treatment The second attachment is heat-treated to obtain the rare earth permanent magnet. In the present invention, the second attachment may be cooled after going through several preheating and preheating stages, and then cooled again after going through one postheating and postheating stage, thereby obtaining a rare earth permanent magnet. Preferably, the preheating stage includes three to four preheating stages, for example, four preheating stages, which are the first preheating stage, the second preheating stage, the third preheating stage, and the fourth preheating stage. Each preheating stage is immediately followed by one preheating stage.

[0049] The first pre-heating stage and the first pre-holding stage include heating the second attachment to 100-120°C and holding it at this temperature for 1-1.5 hours. The second pre-heating stage and the second pre-holding stage include raising the temperature from 100-120°C to 180-200°C and holding it at this temperature for 1-1.5 hours. The third pre-heating stage and the third pre-heating stage include raising the temperature from 180-200°C to 450-550°C and maintaining the temperature at this temperature for 1-1.5 hours, preferably raising the temperature to 500-530°C. The fourth pre-heating stage and the fourth pre-holding stage include subsequently raising the temperature to 850-950°C and holding it at this temperature for 8-24 hours. Preferably, the temperature is subsequently raised to 900-920°C. The holding time is preferably 10-11 hours.

[0050] In this invention, cooling using an inert gas may be performed using argon gas.

[0051] The post-heating and post-heating stages include raising the temperature to 450-520°C and maintaining this temperature for 4-7 hours. Preferably, the temperature is raised to 490-510°C. The heat retention time is preferably 5-6 hours. This is advantageous in obtaining rare-earth permanent magnets with good performance consistency.

[0052] According to one embodiment of the present invention, the second attachment is heated to 100-200°C and maintained at this temperature for 1-3 hours. Then, the temperature is raised to 450-550°C and maintained at this temperature for 1-1.5 hours. Subsequently, the temperature is raised to 850-950°C and maintained at this temperature for 8-24 hours. Then, heating is stopped and the material is cooled to below 90°C using an inert gas. Then, the temperature is raised to 450-520°C and maintained at this temperature for 4-7 hours, heating is stopped, and the material is cooled to below 60°C using an inert gas to obtain a rare earth permanent magnet. This is advantageous for obtaining a rare earth permanent magnet with stable performance.

[0053] <Electrical equipment> The present invention also provides an electric machine containing the above-mentioned rare-earth permanent magnet. The back electromotive force attenuation rate α of the electric machine at high temperatures is less than 0.5%. Specifically, the back electromotive force attenuation rate α of the electric machine at 120°C, 140°C, and 160°C is less than 0.30%, less than 0.37%, and less than 0.40%, respectively. The rare-earth permanent magnet of the present invention is mounted on the electric machine, the back electromotive force V0 is measured at room temperature (e.g., 25°C), load tests are performed at 120°C, 140°C, and 160°C, and then the back electromotive force V0 is measured again after returning to room temperature (e.g., 25°C). t Measure the following and calculate the corresponding damping rate α using the following formula: α = (V0 - V) t ) / V0 × 100%.

[0054] <Explanation of ingredients> Terbium slurry: A terbium slurry with a mass concentration of 75 wt% terbium is formed from terbium powder and terpineol oil. Dysprosium slurry: A dysprosium slurry with a mass concentration of 75 wt% dysprosium is formed from dysprosium powder and terpineol oil.

[0055] <Testing Method> Measurement of magnetic properties: A Belgian Metis magnetic tester was used to measure the magnetic properties at room temperature. Unless otherwise specified, the "%" below indicates a percentage by weight.

[0056] Example 1 A sintered bonded neodymium iron boron magnet with dimensions of 39 mm (length) x 17.8 mm (width) x 4 mm (thickness) was provided, and the surface of the magnet was polished. The composition of the sintered bonded neodymium iron boron magnet is shown in Table 1 below. TIFF2026047003000002.tif18170 Note: The weight ratio of Pr to Nd is 1:3.

[0057] As shown in Figure 1, the sintered bonded neodymium iron boron magnet has two initial periphery portions A1 and one initial central portion A2 along the width direction. The two initial periphery portions A1 are located on either side of the initial central portion A2 and are symmetrical with respect to the central axis of the initial central portion A2.

[0058] A sintered bonded neodymium-iron-boron magnet was placed in a printing apparatus. Terbium slurry was deposited by printing on one surface of each of the two initial periphery A1 (areas of 39 mm × 2.8 mm each) along the orientation direction, and dried at 180°C. The weight increase rate of terbium Tb was 0.074%. Then, dysprosium slurry was deposited by printing on one surface of the initial central part A2 (area of ​​39 mm × 12.2 mm), and dried at 180°C to obtain the first deposit. The weight increase rate of dysprosium Dy was 0.31%.

[0059] The first deposit was flipped over. The above process was repeated, and terbium slurry was attached by printing on the other side of each of the two initial periphery A1 (i.e., the side without terbium printing, with an area of ​​39 mm × 2.8 mm each), and dried at 180°C. The weight increase rate of terbium Tb was 0.078%. Then, dysprosium slurry was attached by printing on the other side of the initial central A2 (with an area of ​​39 mm × 12.2 mm), and dried at 180°C to obtain the second deposit. The weight increase rate of dysprosium Dy was 0.32%.

[0060] A rare earth permanent magnet was obtained by heat-treating the second attached material. The specific steps of the heat treatment were as follows: the temperature was raised to 100°C and held at 100°C for 1 hour, then raised to 200°C and held at 200°C for 1 hour, then raised to 500°C and held at 500°C for 1 hour, then raised to 920°C and held at 920°C for 10 hours, then heating was stopped and the temperature was cooled to below 90°C using argon gas, then raised to 490°C and held at 490°C for 5 hours, heating was stopped and the temperature was cooled to below 60°C using argon gas to obtain the rare earth permanent magnet. The initial edge A1 in the sintered bonded neodymium iron boron magnet was formed corresponding to the edge of the rare earth permanent magnet; that is, the shape, width, and length of the edge in the rare earth permanent magnet and the initial edge A1 in the sintered bonded neodymium iron boron magnet were the same. The initial central portion A2 in the sintered bonded neodymium iron boron magnet was formed corresponding to the central portion of the rare earth permanent magnet; that is, the shape, width, and length of the central portion of the rare earth permanent magnet and the initial central portion A2 of the sintered bonded neodymium iron boron magnet were the same.

[0061] The rare-earth permanent magnet was sliced ​​along its width (width is 17.8 mm) into 1 mm wide slices (slice dimensions: 39 mm × 1.0 mm × 4 mm). Specifically, a total of seven rare-earth permanent magnets obtained from the sintered bonded neodymium iron boron magnet shown in Figure 1 were cut from right to left. Then, the middle of the resulting slices was cut along their length to obtain two samples (sample dimensions: 5 mm × 1.0 mm × 4 mm). The magnetic properties of one of these samples were tested, and the composition of the other was measured. The test results are shown in Table 2. Since the edges are symmetrical, only one edge was analyzed.

[0062] TIFF2026047003000003.tif57170 Note: Slice 3 includes a small portion of the center.

[0063] As can be seen from this, in the rare-earth permanent magnet of the present invention, the weight percentage of Dy gradually increases and the weight percentage of Tb gradually decreases along the direction of the central axis from the outer edge of the periphery toward the center. The average coercivity of the periphery is greater than the average coercivity of the center.

[0064] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the terbium Tb attached to the initial periphery is replaced with dysprosium Dy. Details are as follows.

[0065] A sintered bonded neodymium iron boron magnet with dimensions of 39 mm (length) x 17.8 mm (width) x 4 mm (thickness) was provided, and the surface of the magnet was polished. The composition of the sintered bonded neodymium iron boron magnet is shown in Table 1 below.

[0066] As shown in Figure 1, the sintered bonded neodymium iron boron magnet has two initial periphery portions A1 and one initial central portion A2 along the width direction. The two initial periphery portions A1 are located on either side of the initial central portion A2 and are symmetrical with respect to the central axis of the initial central portion A2.

[0067] A sintered bonded neodymium-iron-boron magnet was placed in a printing apparatus. Dysprosium slurry was deposited by printing on one surface of each of the two initial edge regions A1 (areas of 39 mm × 2.8 mm each) along the orientation direction, and dried at 180°C. The weight increase rate of dysprosium Dy was 0.074%. Then, dysprosium slurry was deposited by printing on one surface of the initial central region A2 (area of ​​39 mm × 12.2 mm), and dried at 180°C to obtain the first deposit. The weight increase rate of dysprosium Dy was 0.31%.

[0068] The first deposit was flipped over. The above process was repeated, and dysprosium slurry was attached by printing on the other side of each of the two initial peripheral A1 sections (i.e., the side not printed with dysprosium, with an area of ​​39 mm × 2.8 mm each), and dried at 180°C. The weight increase rate of dysprosium Tb was 0.078%. Then, dysprosium slurry was attached by printing on the other side of the initial central A2 section (with an area of ​​39 mm × 12.2 mm), and dried at 180°C to obtain the second deposit. The weight increase rate of dysprosium Dy was 0.32%.

[0069] A rare earth permanent magnet was obtained by heat-treating the second attached material. The specific steps of the heat treatment were as follows: the temperature was raised to 100°C and held at 100°C for 1 hour, then raised to 200°C and held at 200°C for 1 hour, then raised to 500°C and held at 500°C for 1 hour, then raised to 920°C and held at 920°C for 10 hours, then heating was stopped and the temperature was cooled to below 90°C using argon gas, then raised to 490°C and held at 490°C for 5 hours, heating was stopped and the temperature was cooled to below 60°C using argon gas to obtain the rare earth permanent magnet. The initial edge A1 in the sintered bonded neodymium iron boron magnet was formed corresponding to the edge of the rare earth permanent magnet; that is, the shape, width, and length of the edge in the rare earth permanent magnet and the initial edge A1 in the sintered bonded neodymium iron boron magnet were the same. The initial central portion A2 in the sintered bonded neodymium iron boron magnet was formed corresponding to the central portion of the rare earth permanent magnet; that is, the shape, width, and length of the central portion of the rare earth permanent magnet and the initial central portion A2 of the sintered bonded neodymium iron boron magnet were the same.

[0070] The rare-earth permanent magnet was sliced ​​along its width (width is 17.8 mm) into 1 mm wide slices (slice dimensions: 39 mm × 1.0 mm × 4 mm). Specifically, a total of seven rare-earth permanent magnets obtained from the sintered bonded neodymium iron boron magnet shown in Figure 1 were cut from right to left. Then, the middle of the resulting slices was cut along their length to obtain two samples (sample dimensions: 5 mm × 1.0 mm × 4 mm). The magnetic properties of one of these samples were tested, and the composition of the other was measured. The test results are shown in Table 3. Since the edges are symmetrical, only one edge was analyzed.

[0071] TIFF2026047003000004.tif91170

[0072] The rare earth permanent magnets obtained from Example 1 and Comparative Example 1 were each mounted on an electric machine, and the back electromotive force V0 at room temperature was measured. Load tests were then conducted at high temperatures of 120°C, 140°C, and 160°C, and then the back electromotive force V0 was measured again when the temperature was returned to room temperature. t The following equation was used to measure the damping rate α and calculate the corresponding damping rate α: α = (V0 - V) t ) / V0×100%. The calculation results are shown in Table 4.

[0073] TIFF2026047003000005.tif35170

[0074] As can be seen from the table, the attenuation rate of Example 1 is very small (less than 0.5%), indicating minimal demagnetization, while Comparative Example 1 shows a back electromotive force loss of 3.31% at 160°C, indicating relatively large demagnetization.

[0075] The present invention is not limited to the embodiments described above, and any modifications, improvements, substitutions, etc., that a person skilled in the art could conceive of, without departing from the spirit of the invention, are included within the scope of the present invention.

Claims

1. It contains light rare earth elements and heavy rare earth elements, wherein the light rare earth elements must contain Nd, and the heavy rare earth elements must contain Dy and Tb, R 2 Fe 14 B is the main phase, where R is a rare earth element. Along the width direction, the rare-earth permanent magnet has two peripheral portions and one central portion, with the two peripheral portions located on either side of the central portion and symmetrical with respect to the central axis of the central portion. The periphery has an outer periphery and an inner periphery, the outer periphery is farther from the central part, and the inner periphery is closer to the central part. Along the direction of the central axis from the outer periphery to the central part, the weight percentage of Dy gradually increases, and the weight percentage of Tb gradually decreases. A rare-earth permanent magnet characterized by having an average coercivity value at the periphery greater than the average coercivity value at the center.

2. The rare earth permanent magnet according to claim 1, characterized in that the length of the edge portion is the same as the length of the central portion, and the width of the central portion is greater than the sum of the widths of the two edges.

3. The rare-earth permanent magnet according to claim 1, characterized in that the difference between the minimum coercivity at the edge and the minimum coercivity at the center exceeds 60 kA / m.

4. The rare earth permanent magnet according to claim 1, characterized in that, along the direction of the central axis extending from the outer edge of the periphery to the central part, the maximum weight percentage of Dy is less than 2 wt%, the minimum weight percentage of Dy is greater than 0.03 wt%, the maximum weight percentage of Tb is less than 1 wt%, and the minimum weight percentage of Tb is less than 0.05 wt%.

5. The rare earth permanent magnet according to claim 4, characterized in that the light rare earth element further contains Pr, and the content of the rare earth element R is 29 wt% or more based on the total weight of the rare earth permanent magnet.

6. The following steps, (1) R 2 Fe 14 The magnet provides a sintered bonded neodymium iron boron magnet, with B as the main phase, having two initial peripheral portions and one initial central portion along the width direction, with the two initial peripheral portions located on either side of the initial central portion and symmetrical with respect to the central axis of the initial central portion, where R is a rare earth element. (2) Along the orientation direction, the terbium-containing material is attached to one of the initial peripheral surfaces and dried, and then the dysprosium-containing material is attached to one of the initial central surfaces and dried to obtain the first attached body. (3) Along the orientation direction, a terbium-containing material is attached to the other surface of the initial periphery of the first attachor and dried, and then a dysprosium-containing material is attached to the other surface of the initial central part and dried to obtain a second attachor. (4) The second attachment is heat-treated to obtain the rare earth permanent magnet, where the initial peripheral portion is formed corresponding to the peripheral portion, and the initial central portion is formed corresponding to the central portion. A method for manufacturing a rare earth permanent magnet according to any one of claims 1 to 5, characterized in that it includes the following:

7. The manufacturing method according to claim 6, wherein step (1) is the sintered bonded neodymium iron boron magnet, where R is a rare earth element and contains Nd and Pr.

8. Step (1) involves determining that the sintered bonded neodymium iron boron magnet contains the following composition, based on the total weight of the sintered bonded neodymium iron boron magnet: PrNd 28–32 wt%, B 0.89–0.98 wt%, Dy 0.01–1.15 wt%, Cu 0.01–0.25 wt%, Co 0.01–1.85 wt%, Ga 0.01–0.30 wt%, M 0.01–0.20 wt%, and Fe remainder, Here, M is at least one selected from Ti, Zr, Mo, and Nb. Here, the weight ratio of Pr to Nd is 1:3 to 1:

4. The manufacturing method described in feature 6.

9. In process (2), the drying temperature was 120–200°C throughout, the weight increase rate of terbium was 0.075–0.25 wt%, and the weight increase rate of dysprosium was 0.2–0.425 wt%. In process (3), the drying temperature is 120–200°C throughout, the weight increase rate of terbium is 0.075–0.25 wt%, and the weight increase rate of dysprosium is 0.2–0.425 wt%. The manufacturing method described in feature 6.

10. The attenuation rate α of the back electromotive force of the electric machine is less than 0.5%, and α is calculated using the following formula: α=(V 0 -IN t ) / IN 0 ×100% yes、 Here, V 0 is the back electromotive force at normal temperature in the initial state, and V t is the back electromotive force when it returns to room temperature after the high-temperature load test An electric machine characterized by including a rare earth permanent magnet as described in any one of claims 1 to 5.

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