Rare earth permanent magnets, their manufacturing methods, and electrical equipment

Abstract

A rare earth permanent magnet having good resistance to demagnetization, a manufacturing method thereof, and a built-in rare earth permanent magnet electric machine are provided. [Solution] The rare earth permanent magnet contains light rare earth elements and heavy rare earth elements, the light rare earth elements consisting essentially of Nd, and the heavy rare earth elements consisting essentially of Dy and Tb. Along the width direction, there are two initial peripheral regions A1 and one initial central region A2, each located on either side of the central region and symmetrical about the central axis of the central region. The peripheral regions have an outer edge and an inner edge, the outer edge being far from the central region and the inner edge being close to the central region. Along the direction of the central axis from the outer edge of the peripheral regions to the central region, the weight percentage of Dy gradually increases and the weight percentage of Tb gradually decreases, and the average coercivity of the peripheral regions is greater than the average coercivity of the central region.

Description

[Technical Field]

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

[0002] Conventionally, R2Fe 14 R-Fe-B rare earth sintered magnets, which have B as the main phase, are among the most highly performing permanent magnets. Niha It is used in voice coil motors for hard disk drivers, motors for hybrid vehicles, and various home appliances.

[0003] Electric machine Decrease in magnetic Endurance The resistance is the resistance of the motor to the external magnetic field during the operation process. of influence Resistant to It refers to the ability to vinegar. Generally speaking, the higher the demagnetization resistance of an electric motor, the higher its stability and reliability. The demagnetization resistance of an electric motor is closely related to the materials used. For example, in the case of a permanent magnet electric motor, the coercive force of the permanent magnetic material is an important factor affecting the demagnetization resistance.

[0004] In order to be suitable for use in high-temperature environments, rare earth permanent magnetic materials are required to have excellent heat resistance and high coercive force.

[0005] CN113506665A discloses a method for increasing the coercivity of bonded neodymium iron boron magnets through efficient diffusion, which involves coating the edges of the bonded neodymium iron boron magnets with a grain boundary diffusing agent containing heavy rare earths, light rare earths, or no rare earths, and then heat treating the magnets. However, the coercivity of the magnets obtained by this method still needs to be improved.

[0006] CN115732215A discloses a method for producing a low demagnetization rate bonded neodymium iron boron magnetic material, which includes laser processing a sintered bonded neodymium iron boron magnetic material to obtain a pre-treated bonded neodymium iron boron magnetic material, and 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, wherein the heavy rare earth film is prepared from a single heavy rare earth element and an auxiliary element, and the heavy rare earth bonded neodymium iron boron magnetic material is sequentially subjected to vacuum diffusion, laser weight removal, and electroplating to obtain a low demagnetization rate bonded neodymium iron boron magnetic material.

[0007] CN111653404A discloses a bonded neodymium iron boron magnet with the formula R1-R2-Fe-MB, which has a composite structure with regions of high coercivity and high remanence, 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. The bonded neodymium iron boron magnet has regions of high coercivity with a high R2 content and regions of low R2 content with high remanence, where R2 forms a film on two opposing surfaces of an R1-Fe-MB-based matrix magnet, the two opposing surfaces being non-perpendicular to the magnet's magnetization direction and non-perpendicular to the pressing direction when the magnet is formed. This allows for a reduction in the amount of heavy rare earth used and prevents thermal demagnetization at high temperatures. Summary of the Invention

[0008] One object of the present invention is to provide a rare earth permanent magnet with good resistance to demagnetization. The magnet is suitable for built-in rare earth permanent magnet electric machines. Another object of the present invention is to provide a method for manufacturing such a rare earth permanent magnet. Another object of the present invention is to provide an electric machine. In order to achieve the above objects, the present invention employs the following configuration.

[0009] On the other hand, the present invention is directed to a composition containing a light rare earth element and a heavy rare earth element, the light rare earth element essentially containing Nd, the heavy rare earth element essentially containing Dy and Tb, and RFe 14 B is the main phase, where R is a rare earth element, The rare earth permanent magnet has two edge portions and one central portion along the width direction, the two edge portions being located on both sides of the central portion and symmetrical with respect to the central axis of the central portion, the peripheral portion has an outer edge and an inner edge, the outer edge being farther from the central portion and the inner edge being closer to the central portion, and the weight percentage of Dy gradually increasing and the weight percentage of Tb gradually decreasing along a central axis direction from the outer edge of the peripheral portion toward the central portion; A rare earth permanent magnet is provided in which the average value of the coercive force at the periphery is greater than the average value of the coercive force at the center.

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

[0011] In the rare earth permanent magnet according to the present invention, the difference between the minimum value of the coercive force at the periphery and the minimum value of the coercive force at the center preferably 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 peripheral portion 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] The rare earth permanent magnet according to the present invention preferably further contains Pr in addition to the light rare earth element, 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 provides a method for producing a method for manufacturing a semiconductor device, comprising the steps of: (1)R2Fe 14a sintered bonded neodymium iron boron magnet having B as a main phase, two initial peripheral portions and one initial central portion along the width direction, the two initial peripheral portions being located on either side of the initial central portion and symmetrical about the central axis of the initial central portion, and R being a rare earth element; (2) depositing a terbium-containing material on one of the surfaces of the initial peripheral portion along the orientation direction, followed by drying, and then depositing a dysprosium-containing material on one of the surfaces of the initial central portion, followed by drying, to obtain a first deposit; (3) depositing a terbium-containing material on another surface of the initial peripheral portion of the first deposit along the orientation direction, followed by drying, and then depositing a dysprosium-containing material on another surface of the initial central portion of the first deposit, followed by drying, to obtain a second deposit; (4) heat-treating the second deposit to obtain the rare earth permanent magnet, wherein the initial peripheral portion corresponds to the peripheral portion and the initial central portion corresponds to the central portion; The present invention provides a method for producing the rare earth permanent magnet, comprising:

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

[0016] In the manufacturing method according to the present invention, preferably, in step (1), the sintered bonded neodymium iron boron magnet has the following composition, based on the total weight of the sintered bonded neodymium iron boron magnet: PrNd 28-32wt%, B 0.89~0.98wt%, Dy 0.01 to 1.15 wt%, Cu 0.01 to 0.25 wt%, Co 0.01 to 1.85 wt%, Ga 0.01 to 0.30 wt%, M 0.01 to 0.20 wt%, and 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 to 1:4.

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

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

[0019] [Figure 1] 1 is a schematic diagram of the initial edge and center portions of a sintered bonded neodymium iron boron magnet of the present invention, where A1 represents the initial edge portion and A2 represents the initial center portion. DETAILED DESCRIPTION OF THE INVENTION

[0020] Below are the specifics Fruit The present invention will be further explained with reference to examples, but the scope of the present invention is not limited thereto.

[0021] The "coercive force" described in this invention is also called the intrinsic coercive force, and refers to the strength of the magnetic field that decreases monotonically from the saturated magnetization state of a magnet to zero and then increases conversely, decreasing the magnetization strength along the saturation hysteresis curve until it reaches zero. cj or MHc, and its unit is oersted (Oe) or amperes per meter (A / m). 1Oe=79.6A / m. H cj is the intrinsic coercivity at room temperature.

[0022] The "residual magnetic flux density" described in this invention refers to the numerical value of the magnetic flux density corresponding to the magnetic field strength of zero on the saturation hysteresis curve, and is usually expressed as Br or Mr, with units of tesla (T) or gauss (Gs).

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

[0024] <Rare earth permanent magnet> The rare earth permanent magnet of the present invention contains a light rare earth element and a heavy rare earth element, the light rare earth element essentially containing Nd, the heavy rare earth element essentially containing Dy and Tb, and RFe 14 The main phase is B. Here, R represents a rare earth element. In one embodiment, R represents a light rare earth element. The light rare earth element further includes 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 of the present invention may have a hexahedral structure, with two peripheral portions and one central portion, the two peripheral portions being located on either side of the central portion and 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 peripheral portion is the same as the length of the central portion. The width of the central portion is greater than the sum of the widths of the two peripheral portions. The width of the peripheral portion may be 1.5 to 3.5 mm. The width of the central portion may be 6 to 20 mm. In a specific embodiment, the width of the peripheral portion is 2 to 3.1 mm, and the width of the central portion 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 direction.

[0027] The peripheral portion has an outer edge and an inner edge, the outer edge being far from the central portion and the inner edge being close to the central portion. In some embodiments, the boundary between the inner edge and the central portion is clear. In other embodiments, the boundary between the inner edge and the central portion is not clear. There is partial fusion between the inner edge and the central portion.

[0028] outer margin of the margin mosquito Along the direction of the central axis from the center toward the center, the weight percentage of Dy gradually increases and the weight percentage of Tb gradually decreases.

[0029] Preferably, the outer edge of the margin mosquito The maximum weight percentage of Dy is less than 1.5 wt% along the central axis from the outer edge of the peripheral portion toward the center. More preferably, the maximum weight percentage of Dy is less than 1 wt% along the central axis from the outer edge of the peripheral portion toward the center. In one specific embodiment according to the present invention, the minimum weight percentage of Dy is more than 0.5 wt% and the maximum weight percentage of Dy is less than 2 wt% along the central axis from the outer edge of the peripheral portion toward the center.

[0030] outer margin of the margin mosquitoAlong the direction of the central axis from the outer edge of the peripheral portion toward the center, the maximum weight percentage of Tb is less than 1 wt% and the minimum weight percentage of Tb is less than 0.05 wt%. Preferably, along the direction of the central axis from the outer edge of the peripheral portion toward the center, the maximum 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 peripheral portion toward the center, the maximum 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 peripheral portion toward the center, the difference between the maximum weight percentage of Dy and the minimum weight percentage of Dy exceeds 0.2 wt%.

[0031] The average coercive force of the peripheral regions is greater than the average coercive force of the central region. The difference between the minimum coercive force of the peripheral regions and the minimum coercive force of the central region is greater than 60 kA / m, for example, greater than 100 kA / m, or even greater than 120 kA / m. According to one embodiment of the present invention, the minimum coercive force of the peripheral regions is greater than 1950 kA / m, for example, greater than 2015 kA / m. According to one embodiment of the present invention, the minimum coercive force of the central region is greater than 1850 kA / m, for example, greater than 1875 kA / m. The present invention finds that such rare earth permanent magnets have high residual magnetic flux density, high coercive force, and good resistance to demagnetization, making them suitable for built-in rare earth permanent magnet electric motors.

[0032] <Manufacturing method> The present invention also provides a method for producing the rare earth permanent magnet described above, which comprises the steps of: (1) providing an initial sintered bonded neodymium iron boron magnet, (2) obtaining a first deposit, (3) obtaining a second deposit, and (4) heat treating, which advantageously results in the rare earth permanent magnet having a hexahedral structure with two peripheral portions and a central portion described above.

[0033] Initially Sintered Bonded Neodymium Iron Boron Magnets of provide R2Fe 14 Sintered bonded neodymium iron boron magnet with B as the main phase ofThe sintered bonded neodymium iron boron magnet has a hexahedral structure. It has two initial edge portions and one initial center portion along the width direction. The two initial edge portions are located on either side of the initial center portion and are symmetrical about the central axis of the initial center portion.

[0034] In the sintered bonded neodymium iron boron magnet, R is a rare earth element, including 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: 28-32 wt% PrNd, 0.89-0.98 wt% B, 0.01-1.15 wt% Dy, 0.01-0.25 wt% Cu, 0.01-1.85 wt% Co, 0.01-0.30 wt% Ga, 0.01-0.20 wt% M, and the balance Fe, where M is at least one element selected from the group consisting of Ti, Zr, Mo, and Nb. The weight ratio of Pr to Nd is 1:3 to 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 Dy weight percentage 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%, and 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% or 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] Obtaining the first attachment A terbium-containing material is applied to one surface of the initial peripheral portion of the sintered bonded neodymium iron boron magnet along the orientation direction, followed by drying, and a dysprosium-containing material is applied to one surface of the initial central portion, followed by drying, to obtain a first application body, wherein the one surface of the initial peripheral portion and the one surface of the initial central portion of the sintered bonded neodymium iron boron magnet are substantially flush with each other.

[0037] The terbium-containing substance may be applied to one of the surfaces of the initial peripheral portion by printing or spraying. The terbium-containing substance may be terbium hydride or powder of metallic terbium and its alloy. The terbium-containing substance (e.g., terbium powder) may be mixed with an organic solvent to form a terbium slurry, and the mass concentration of the terbium slurry 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. This allows for accurate application of terbium, a high adhesion rate, and good reproducibility.

[0038] The controlled weight gain 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%. Weight gain of terbium = (weight after covering with terbium metal paint - original weight before covering with terbium metal paint) / original weight before covering with terbium metal paint × 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 is used to deposit terbium, and a printing device may be used for printing.

[0040] The dysprosium-containing substance may be applied to one of the surfaces of the initial central portion by printing or spraying. The dysprosium-containing substance may be dysprosium hydride or metallic dysprosium and its alloys. The dysprosium-containing substance (e.g., dysprosium powder) may be mixed with an organic solvent to form a dysprosium slurry, and the mass concentration of the dysprosium slurry 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. This allows for accurate application of dysprosium, a high adhesion rate, and good reproducibility.

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

[0042] Obtaining the second attachment A terbium-containing material is deposited on another surface of the initial peripheral portion of the first deposit along the orientation direction and dried, and a dysprosium-containing material is deposited on another surface of the initial central portion and dried to obtain a second deposit, which is approximately flush with the other surface of the initial peripheral portion and the other surface of the initial central portion of the first deposit.

[0043] The first deposited body may be turned over and terbium or dysprosium may be deposited on the other side, to which the heavy rare earth element is not attached, by the same specific steps as those for obtaining the first deposited body.

[0044] A terbium-containing substance is deposited on the other surface of the initial peripheral portion of the first deposition body along the orientation direction by printing or spraying. The terbium-containing substance may be terbium hydride or metallic terbium and its alloy powder. The terbium-containing substance (e.g., terbium powder) may be mixed with an organic solvent to form a terbium slurry. The mass concentration of the terbium slurry 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. This allows for accurate deposition of terbium, resulting in a high deposition rate and good reproducibility.

[0045] The controlled weight gain 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%. Weight gain of terbium = (weight of first deposited body after being covered with terbium metal paint - original weight of first deposited body before being covered with terbium metal paint) / original weight of first deposited body before being covered with terbium metal paint × 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 center portion by printing or spraying. The dysprosium-containing material may be dysprosium hydride or powder of metallic dysprosium and its alloy. The dysprosium-containing material (e.g., dysprosium powder) may be mixed with an organic solvent to form a dysprosium slurry. The mass concentration of the dysprosium slurry 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 gain of dysprosium is 0.2 to 0.425 wt%, and preferably 0.3 to 0.325 wt%. Weight gain of dysprosium = (weight of first deposited body after being covered with dysprosium metal paint - original weight of first deposited body before being covered with dysprosium metal paint) / original weight of first deposited body before being covered with dysprosium metal paint × 100%. The drying temperature may be 120 to 200°C, preferably 150 to 200°C, and more preferably 180 to 190°C. This allows dysprosium to be deposited accurately, resulting in a high deposition rate and good reproducibility.

[0048] Heat Treatment The second deposit is heat treated to obtain the rare earth permanent magnet. In the present invention, the second attachment body is subjected to several pre-heating and pre-warming steps. Offered to , Next Cooling, then one post-heating stage and one post-holding stage Offered to , cooling again death, Do so child and in , rare earth permanent magnets Get Preferably, the pre-heating stage is 3 to 4 pre-heating stages. Including For example, there may be four pre-heating stages, which are a first pre-heating stage, a second pre-heating stage, a third pre-heating stage, and a fourth pre-heating stage. Each pre-heating stage is followed by one pre-warming stage. but To be continued.

[0049] The first pre-heating step and the first pre-heating step include heating the second adhesion body to 100 to 120 ° C. and keeping it at this temperature for 1 to 1.5 hours (hours), The second pre-heating step and the second pre-heating step include raising the temperature from 100-120 ° C to 180-200 ° C and keeping the temperature at this temperature for 1 to 1.5 hours; The third pre-heating step and the third pre-heating step 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 step and the fourth pre-heating step include successively raising the temperature to 850 to 950°C and maintaining the temperature at this temperature for 8 to 24 hours. Preferably, the temperature is successively raised to 900 to 920°C. The temperature maintenance time is preferably 10 to 11 hours.

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

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

[0052] According to one embodiment of the present invention, the second adhering body is heated to 100-200°C and kept at this temperature for 1-3 hours. Then, the temperature is increased to 450-550°C and kept at this temperature for 1-1.5 hours. Then, the temperature is increased to 850-950°C and kept at this temperature for 8-24 hours. Then, heating is stopped and the body is cooled to below 90°C using inert gas. Then, the temperature is increased to 450-520°C and kept at this temperature for 4-7 hours. death , stop heating do . after that, The rare earth permanent magnet is obtained by cooling it to below 60°C using inert gas, which is advantageous for obtaining a rare earth permanent magnet with stable performance.

[0053] <Electrical equipment> The present invention also provides an electric machine including the rare earth permanent magnet. The counter electromotive force decay rate α of the electric machine at high temperatures is less than 0.5%. Specifically, the counter electromotive force decay rates α of the electric machine at 120°C, 140°C, and 160°C are 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 in an electric machine, and the counter electromotive force V0 is measured at room temperature (e.g., 25°C). Load experiments are conducted at 120°C, 140°C, and 160°C, and the counter electromotive force V is measured again after recovery to room temperature (e.g., 25°C). t and calculate the corresponding attenuation factor α by employing the following formula: α=(V0-V t ) / V0×100%.

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

[0055] <Test Method> Measurement of magnetic properties: A magnetic tester from Belgium's Metis is used to measure the magnetic properties at room temperature. Unless otherwise specified, "%" below indicates percentage by weight.

[0056] Example 1 A sintered bonded neodymium iron boron magnet measuring 39 mm (length) x 17.8 mm (width) x 4 mm (thickness) was prepared, and the surface of the magnet was polished. The composition of the sintered bonded neodymium iron boron magnet is shown in Table 1 below. TIFF0007811983000002.tif18170Note: The weight ratio of Pr to Nd is 1:3.

[0057] As shown in Figure 1, the sintered bonded NdFeB magnet has two initial peripheral portions A1 and one initial central portion A2 along its width. The two initial peripheral portions A1 are located on either side of the initial central portion A2 and are symmetrical about the central axis of the initial central portion A2.

[0058] The sintered bonded neodymium iron boron magnet was placed in a printing device. Terbium slurry was applied by printing onto one surface of each of the two initial peripheral portions A1 (each having an area of ​​39 mm × 2.8 mm) along the orientation direction and dried at 180°C. The weight gain of terbium (Tb) was 0.074%. Then, dysprosium slurry was applied by printing onto one surface of the initial central portion A2 (having an area of ​​39 mm × 12.2 mm) and dried at 180°C to obtain a first deposit. The weight gain of dysprosium (Dy) was 0.31%.

[0059] The first deposit was turned over. The above process was repeated, and terbium slurry was applied by printing on the other surface of each of the two initial peripheral portions A1 (i.e., the surface on which terbium was not printed, each having an area of ​​39 mm × 2.8 mm), and then dried at 180 °C. The weight gain of terbium Tb was 0.078%. Then, dysprosium slurry was applied by printing on the other surface of the initial central portion A2 (having an area of ​​39 mm × 12.2 mm), and then dried at 180 °C to obtain a second deposit. The weight gain of dysprosium Dy was 0.32%.

[0060] The second deposit was heat-treated to obtain a rare earth permanent magnet. The specific heat treatment steps were as follows: heat to 100°C and hold at 100°C for 1 hour, then heat to 200°C and hold at 200°C for 1 hour, then heat to 500°C and hold at 500°C for 1 hour, then heat to 920°C and hold at 920°C for 10 hours, then stop heating and cool to below 90°C using argon gas, then heat to 490°C and hold at 490°C for 5 hours, stop heating, and cool to below 60°C using argon gas to obtain a rare earth permanent magnet. The initial edge portion A1 of the sintered bonded NdFeB magnet corresponded to the edge portion of the rare earth permanent magnet, i.e., the edge portion of the rare earth permanent magnet and the initial edge portion A1 of the sintered bonded NdFeB magnet had the same shape, width, and length. The initial central portion A2 of the sintered bonded neodymium iron boron magnet was formed corresponding to the central portion of the rare earth permanent magnet, i.e., the central portion of the rare earth permanent magnet and the initial central portion A2 of the sintered bonded neodymium iron boron magnet had the same shape, width, and length.

[0061] The rare earth permanent magnet was sliced ​​widthwise (17.8 mm) into 1 mm-wide pieces (39 mm x 1.0 mm x 4 mm slice dimensions). Specifically, a total of seven pieces were cut from right to left into the rare earth permanent magnet obtained from the sintered bonded neodymium iron boron magnet shown in Figure 1. The resulting slices were then cut in the middle lengthwise to obtain two samples (5 mm x 1.0 mm x 4 mm sample dimensions). The magnetic properties of one of the samples were tested, and the composition of the other was measured. The test results are shown in Table 2. Because the peripheral portions were symmetrical, only one of the peripheral portions was analyzed.

[0062] TIFF0007811983000003.tif57170 Note: Slice 3 includes a small central portion.

[0063] As can be seen, 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 central axis from the outer edge of the peripheral portion toward the center. The average coercivity of the peripheral portion is greater than the average coercivity of the center portion.

[0064] Comparative Example 1 Comparative Example 1 and The only difference in Example 1 is that the terbium (Tb) deposited at the initial periphery is replaced with dysprosium (Dy). The 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. Composition of the sintered bonded neodymium iron boron magnet is a table As shown in 1.

[0066] As shown in Figure 1, the sintered bonded NdFeB magnet has two initial peripheral portions A1 and one initial central portion A2 along its width. The two initial peripheral portions A1 are located on either side of the initial central portion A2 and are symmetrical about the central axis of the initial central portion A2.

[0067] The sintered bonded neodymium iron boron magnet was placed in a printing device. Dysprosium slurry was applied by printing along the orientation direction onto one surface of each of the two initial peripheral portions A1 (each measuring 39 mm × 2.8 mm) and dried at 180°C. The weight gain of the dysprosium Dy was 0.074%. Then, dysprosium slurry was applied by printing onto one surface of the initial central portion A2 (39 mm × 12.2 mm) and dried at 180°C to obtain a first deposit. The weight gain of the dysprosium Dy was 0.31%.

[0068] The first deposit was turned over. The above process was repeated, and dysprosium slurry was applied by printing on the other side of each of the two initial peripheral portions A1 (i.e., the side on which dysprosium was not printed, each having an area of ​​39 mm × 2.8 mm), and then dried at 180 ° C. The weight gain of dysprosium Tb was 0.078%. Then, dysprosium slurry was applied by printing on the other side of the initial central portion A2 (having an area of ​​39 mm × 12.2 mm), and then dried at 180 ° C. to obtain a second deposit. The weight gain of dysprosium Dy was 0.32%.

[0069] The second deposit was heat-treated to obtain a rare earth permanent magnet. The specific heat treatment steps were as follows: heat to 100°C and hold at 100°C for 1 hour, then heat to 200°C and hold at 200°C for 1 hour, then heat to 500°C and hold at 500°C for 1 hour, then heat to 920°C and hold at 920°C for 10 hours, then stop heating and cool to below 90°C using argon gas, then heat to 490°C and hold at 490°C for 5 hours, stop heating, and cool to below 60°C using argon gas to obtain a rare earth permanent magnet. The initial edge portion A1 of the sintered bonded NdFeB magnet corresponded to the edge portion of the rare earth permanent magnet, i.e., the edge portion of the rare earth permanent magnet and the initial edge portion A1 of the sintered bonded NdFeB magnet had the same shape, width, and length. The initial central portion A2 of the sintered bonded neodymium iron boron magnet was formed corresponding to the central portion of the rare earth permanent magnet, i.e., the central portion of the rare earth permanent magnet and the initial central portion A2 of the sintered bonded neodymium iron boron magnet had the same shape, width, and length.

[0070] The rare earth permanent magnet was sliced ​​widthwise (17.8 mm) into 1 mm-wide pieces (39 mm x 1.0 mm x 4 mm slice dimensions). Specifically, the rare earth permanent magnet obtained from the sintered bonded neodymium iron boron magnet shown in Figure 1 was cut from right to left into a total of seven pieces. The resulting slices were then cut in the middle lengthwise to obtain two samples (5 mm x 1.0 mm x 4 mm sample dimensions). The magnetic properties of one of the samples were tested, and the composition of the other was measured. The test results are shown in Table 3. Because the peripheral portion was symmetrical, only one of the peripheral portions was analyzed.

[0071] TIFF0007811983000004.tif91170

[0072] The rare earth permanent magnets obtained in Example 1 and Comparative Example 1 were attached to an electric machine, and the back electromotive force V0 was measured at room temperature. Load experiments were then carried out at high temperatures of 120°C, 140°C, and 160°C, and the back electromotive force V t was measured and the corresponding attenuation factor α was calculated by adopting the following formula: α=(V0-V t ) / V0×100%. The calculation results are shown in Table 4.

[0073] TIFF0007811983000005.tif35170

[0074] As can be seen from the table, the attenuation rate of Example 1 is very small (less than 0.5%), indicating small 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 above-described embodiments, and any modifications, improvements, substitutions, etc. that may occur to those skilled in the art are intended to be included within the scope of the present invention, provided that they do not deviate from the spirit of the present invention.

Claims

1. A rare earth alloy containing a light rare earth element and a heavy rare earth element, the light rare earth element essentially containing Nd, the heavy rare earth element essentially containing Dy and Tb, and R 2 Fe 14 B is the main phase, where R is a rare earth element, The rare earth permanent magnet has two edge portions and one central portion along the width direction, the two edge portions being located on both sides of the central portion, and being symmetrical with respect to the central axis of the central portion; the peripheral portion has an outer edge and an inner edge, the outer edge being farther from the central portion and the inner edge being closer to the central portion, and the weight percentage of Dy gradually increases and the weight percentage of Tb gradually decreases along a central axis direction from the outer edge of the peripheral portion toward the central portion; A rare earth permanent magnet characterized in that the average value of the coercive force of the peripheral portion is greater than the average value of the coercive force of the central portion.

2. 2. The rare earth permanent magnet according to claim 1, wherein the length of the peripheral 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 peripheral portions.

3. 2. The rare earth permanent magnet according to claim 1, wherein the difference between the minimum coercive force of the peripheral portion and the minimum coercive force of the central portion exceeds 60 kA / m.

4. 2. The rare earth permanent magnet of claim 1, wherein, along the direction of the central axis from the outer edge of the peripheral portion toward the center portion, 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. 5. The rare earth permanent magnet according to claim 4, wherein the light rare earth element further includes 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 process, (1) R 2 Fe 14 a sintered bonded neodymium iron boron magnet having B as a main phase, two initial peripheral portions and one initial central portion along the width direction, the two initial peripheral portions being located on either side of the initial central portion and symmetrical about a central axis of the initial central portion, and R being a rare earth element; (2) depositing a terbium-containing material on one of the surfaces of the initial peripheral portion along the orientation direction, followed by drying, and then depositing a dysprosium-containing material on one of the surfaces of the initial central portion, followed by drying, to obtain a first deposit; (3) depositing a terbium-containing material on another surface of the initial peripheral portion of the first deposit along the orientation direction, followed by drying, and then depositing a dysprosium-containing material on another surface of the initial central portion of the first deposit, followed by drying, to obtain a second deposit; (4) heat-treating the second deposit to obtain the rare earth permanent magnet, wherein an initial peripheral portion forms corresponding to the peripheral portion and an initial central portion forms corresponding to the central portion; 6. The method for producing a rare earth permanent magnet according to claim 1, further comprising:

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

8. In step (1), based on the total weight of the sintered bonded neodymium iron boron magnet, the sintered bonded neodymium iron boron magnet has: PrNd 28-32wt%, B 0.89-0.98 wt%, Dy 0.01 to 1.15 wt%, Cu 0.01 to 0.25 wt%, Co 0.01 to 1.85 wt%, Ga 0.01 to 0.30 wt%, M 0.01 to 0.20 wt%, and Fe, balance, wherein M is at least one selected from Ti, Zr, Mo, and Nb; wherein the weight ratio of Pr to Nd is 1:3 to 1:4; 7. The manufacturing method according to claim 6.

9. In step (2), the drying temperature is 120 to 200°C, the weight gain of terbium is 0.075 to 0.25 wt%, and the weight gain of dysprosium is 0.2 to 0.425 wt%, In step (3), the drying temperature is 120 to 200°C, the weight gain of terbium is 0.075 to 0.25 wt%, and the weight gain of dysprosium is 0.2 to 0.425 wt%.

7. The manufacturing method according to claim 6.

10. The attenuation rate α of the back electromotive force of the electric machine is less than 0.5%, and α is calculated by the following formula: α=(V 0 -IN t ) / IN 0 ×100% yes、 where V 0 is the back electromotive force at room temperature in the initial state, and V t is the back electromotive force returning to room temperature after the high temperature load experiment An electric machine comprising the rare earth permanent magnet according to any one of claims 1 to 5.

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