Rare earth permanent magnets, methods and applications

Abstract

This invention discloses a rare-earth permanent magnet, a method thereof, and its uses. The rare-earth permanent magnet is obtained by diffusion of a sintered NdFeB magnet with a thickness of less than 12 mm in at least one direction through a diffusion source. The sintered NdFeB magnet is composed of R, B, Cu, Ga, Co, Zr, Fe, and unavoidable impurities. R is one or more rare-earth elements other than the heavy rare-earth elements Dy, Tb, and Ho, and must contain Nd. Based on the weight of the sintered NdFeB magnet, the R content is 30–33 wt%, the B content is 0.91–0.95 wt%, and the Co content is 0.95–1.5 wt%. The rare earth permanent magnet of this invention has a Cu content of 0.1–0.25 wt%, a Zr content of 0.08–0.22 wt%, a Ga content of 0.08–0.25 wt%, and the balance being Fe. The diffusion source consists of RE, Ga, Cu, and Al in a mass ratio of 87–93:3–5:3–5:1.5–2.5. RE is selected from at least two of Pr, Dy, and Tb, and must contain Pr. The mass ratio of Pr to RE is 9–14:86–97. The weight ratio of the diffusion source to the sintered NdFeB magnet is 0.4–1.2:100. The rare earth permanent magnet of this invention has good overall magnetic properties.

Description

Technical Field

[0001] This invention relates to a rare earth permanent magnet, a method thereof, and its uses. Background Technology

[0002] In the field of magnets, the maximum magnetic energy product (BH) max The magnetic energy product (Binduction) is the maximum value of the product of magnetic flux density (B) and magnetic field strength (H) on the demagnetization curve of a permanent magnet material. It represents the magnetic energy stored per unit volume of the magnet and directly affects the performance and cost-effectiveness of magnetic devices. A larger magnetic energy product requires less magnetic material to produce the same effect. Coercivity (Hcj) is a characteristic of magnetic materials, referring to the magnetic field strength required to reduce the magnetization of a material to zero after it has been magnetized to magnetic saturation. Coercivity represents the ability of a magnetic material to resist demagnetization. In practical applications, the industry often uses (BH). max The sum of the values ​​of and Hcj represents the overall magnetic properties of a magnetic material; the larger the value, the better the overall magnetic properties.

[0003] Furthermore, squareness is an important parameter describing the shape characteristics of the hysteresis loop in magnetic materials. It is mainly used to measure how close the hysteresis loop is to an ideal rectangle, and is directly related to the magnetization stability and application scenarios of the material. By controlling the crystal structure, magnetic domain distribution, or preparation process of the material, squareness can be optimized to meet different technical requirements.

[0004] CN116895416A discloses an RTB rare-earth permanent magnet. By coating a diffusion source on the surface of the magnet parallel to the orientation direction and performing grain boundary diffusion, the thickness limitation of traditional grain boundary diffused magnets in the orientation direction can be overcome, achieving the fabrication of grain boundary diffused magnets with a thickness ≥20mm in the orientation direction. Simultaneously, combined with the provided grain boundary diffusion treatment process, the magnet can ensure the same improvement in magnetic performance as traditional grain boundary diffused magnets. Furthermore, since the uniformity of the main phase grain size can be improved during grain boundary diffusion, the squareness of the grain boundary diffused magnet is not reduced compared to the base magnet; in fact, the squareness of some diffused magnets is even better than that of the base magnet before diffusion. However, the squareness and overall magnetic performance of this magnet still need further improvement.

[0005] CN113871122B discloses a method for manufacturing a low-heavy rare-earth magnet. The low-heavy rare-earth magnet is prepared from a neodymium iron boron magnet main alloy and a low-heavy rare-earth diffusion source. The chemical formula of the low-heavy rare-earth diffusion source is RxH. y M 1-x-yWhere R refers to at least one of Nd, Pr, Ce, La, Ho, and Gd, H refers to at least one of Tb and Dy, and M refers to at least one of Al, Cu, Ga, Ti, Co, Mg, Zn, and Sn. The low-heavy rare earth diffusion source structure is a uniformly distributed RH phase and RHM phase. The low-heavy rare earth diffusion source is coated onto the surface of the NdFeB magnet main alloy, followed by diffusion and tempering treatment to obtain a low-heavy rare earth magnet. The magnet's grain boundary structure includes a main phase, an R shell, a transition metal shell, and a triangular region. The overall magnetic properties of the magnet obtained by this method are relatively low.

[0006] CN114974776B discloses a method for preparing neodymium iron boron rare earth magnets. By designing a diffusion source and a magnet to cooperate in diffusion, followed by diffusion and aging treatment, a high-performance heavy rare earth-free magnet is obtained. The diffusion source is fabricated by depositing a heavy rare earth-free alloy film on a diffusion source sheet, followed by aging treatment to form a novel diffusion source. The diffusion source sheet is an R... α RH δ M β B γ Fe 100-α-β-γ-δ The heavy rare earth-free film layer has the chemical formula R n M m Aging treatment is performed to form a new type of diffusion source. The overall magnetic properties and squareness of the magnets obtained by this method still need improvement. Summary of the Invention

[0007] In view of this, one object of the present invention is to provide a rare-earth permanent magnet with good overall magnetic properties and good squareness. Another object of the present invention is to provide a method for preparing the rare-earth permanent magnet as described above. The method of the present invention is beneficial for improving the overall magnetic properties and squareness of the obtained rare-earth permanent magnet, and also beneficial for improving the utilization efficiency of heavy rare earth elements. A further object of the present invention is to provide the use of a diffusion source in improving the overall magnetic properties and squareness of rare-earth permanent magnets.

[0008] The present invention achieves the above objectives using the following technical solutions.

[0009] On the one hand, the present invention provides a rare earth permanent magnet, which is obtained by diffusion of a sintered NdFeB magnet with a thickness of less than 12 mm in at least one direction through a diffusion source;

[0010] The diffusion source is attached to two opposite surfaces of the sintered NdFeB magnet in a direction perpendicular to the thickness of less than 12 mm;

[0011] The sintered NdFeB magnet is composed of R, B, Cu, Ga, Co, Zr, Fe, and unavoidable impurities; R is one or more rare earth elements other than heavy rare earth elements Dy, Tb, and Ho, and must contain Nd; based on the weight of the sintered NdFeB magnet, the R content is 30-33 wt%, the B content is 0.91-0.95 wt%, the Co content is 0.95-1.5 wt%, the Cu content is 0.1-0.25 wt%, the Zr content is 0.08-0.22 wt%, the Ga content is 0.08-0.25 wt%, and the balance is Fe;

[0012] The diffusion source is composed of RE, Ga, Cu and Al in a mass ratio of 87-93:3-5:3-5:1.5-2.5; RE is selected from at least two of Pr, Dy and Tb, and must contain Pr, with a mass ratio of Pr to RE of 9-14:86-97;

[0013] The weight ratio of the diffusion source to the sintered NdFeB magnet is 0.4–1.2:100.

[0014] According to the rare earth permanent magnet of the present invention, preferably, in the sintered NdFeB magnet, R is Pr and Nd.

[0015] According to the rare earth permanent magnet of the present invention, preferably, based on the weight of the sintered NdFeB magnet, the R content is 30.5-32 wt%, the B content is 0.91-0.93 wt%, the Co content is 1-1.3 wt%, the Cu content is 0.15-0.23 wt%, the Zr content is 0.09-0.2 wt%, the Ga content is 0.09-0.2 wt%, and the Fe is the balance.

[0016] According to the rare earth permanent magnet of the present invention, preferably, the mass ratio of RE, Ga, Cu and Al in the diffusion source is 88-92:3.5-4.5:3.5-4.5:1.7-2.3.

[0017] According to the rare earth permanent magnet of the present invention, preferably, the mass ratio of Pr to RE in the diffusion source is 10-13.5:89-94.5.

[0018] On the other hand, the present invention also provides a method for preparing the rare earth permanent magnet as described above, comprising the following steps:

[0019] (1) Initial sintered NdFeB magnets are prepared from raw materials including R, B, Cu, Ga, Co, Zr and Fe.

[0020] (2) The initial sintered NdFeB magnet is processed so that the thickness of the magnet in at least one direction is less than 12 mm, thus obtaining a sintered NdFeB magnet;

[0021] (3) Attach the diffusion source to two opposite surfaces of the sintered NdFeB magnet in a direction perpendicular to the thickness of less than 12 mm to obtain the attached magnet; wherein the weight ratio of the diffusion source to the processed sintered NdFeB magnet is 0.4 to 1.2:100;

[0022] (4) The attached magnet is kept at 500-1000℃ for 0.5-20h, cooled to below 80℃, and then kept at 400-700℃ for 0.5-10h to obtain a rare earth permanent magnet.

[0023] According to the method of the present invention, preferably, in step (3), the attachment method is selected from at least one of spraying, magnetron sputtering and screen printing.

[0024] According to the method of the present invention, preferably, in step (4), the attached magnet is kept at 700-1000°C for 5-15 hours, cooled to below 80°C, and then kept at 450-600°C for 3-8 hours.

[0025] The method according to the present invention is preferably:

[0026] In step (1), the raw materials of the initial sintered NdFeB magnet, including R, B, Cu, Ga, Co, Zr and Fe, are melted, hydrogenated and air-jet milled in sequence to obtain magnetic powder with an average particle size of less than or equal to 10 μm; the magnetic powder is pressed into shape to obtain a blank; the blank is sintered to obtain the initial sintered NdFeB magnet.

[0027] In step (1), the billet is sintered in a vacuum sintering furnace with a vacuum degree of less than or equal to 0.1 Pa. The sintering temperature is 950 to 1150 °C and the sintering time is 2 to 10 h.

[0028] In another aspect, the present invention also provides the use of a diffusion source in simultaneously improving the overall magnetic properties and squareness of rare earth permanent magnets. The diffusion source is composed of RE, Ga, Cu and Al in a mass ratio of 87-93:3-5:3-5:1.5-2.5, wherein RE is selected from at least two of Pr, Dy and Tb, and must contain Pr, and the mass ratio of Pr to RE is 9-14:86-97, including the steps described above.

[0029] The rare-earth permanent magnets of this invention exhibit good overall magnetic properties and squareness. The method of this invention is beneficial for improving the overall magnetic properties and squareness of the obtained rare-earth permanent magnets, and for improving the utilization efficiency of heavy rare earth elements. According to a preferred embodiment of this invention, a diffusion source with a specific composition is used as a grain boundary diffusion source for a sintered NdFeB magnet with a certain composition, which can improve the squareness and overall magnetic properties of the obtained magnet. The squareness can reach 0.995. When the unit of maximum energy product is MGOe and the unit of coercivity is kOe, the value of the overall magnetic properties is greater than 75, reaching 75.71. Detailed Implementation

[0030] 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.

[0031] The "vacuum degree" mentioned in this invention refers to the absolute vacuum degree; the smaller the value, the higher the vacuum degree.

[0032] The "average particle size" mentioned in this invention refers to the equivalent diameter of the largest particle when the cumulative distribution in the particle size distribution curve is 50%.

[0033] In this invention, the "inert gas" includes helium, neon, argon, krypton, and xenon. An "inert atmosphere" refers to an atmosphere in which an inert gas or nitrogen is formed and does not affect the performance of the magnet.

[0034] Rare Earth Permanent Magnets

[0035] This invention provides a rare-earth permanent magnet, which is obtained by diffusion of a sintered NdFeB magnet with a thickness of less than 12 mm in at least one direction through a diffusion source; wherein, the diffusion source is attached to two opposite surfaces of the sintered NdFeB magnet perpendicular to the direction with a thickness of less than 12 mm; the sintered NdFeB magnet is composed of R, B, Cu, Ga, Co, Zr, Fe, and unavoidable impurities; R is one or more of any rare earth elements other than heavy rare earth elements Dy, Tb, and Ho, and must contain Nd; based on the weight of the sintered NdFeB magnet, the R content is 30-33 wt%, and the B content is 0.91-0.95 wt%. The rare earth permanent magnet has the following composition: t%, Co content 0.95–1.5 wt%, Cu content 0.1–0.25 wt%, Zr content 0.08–0.22 wt%, Ga content 0.08–0.25 wt%, and the balance being Fe; wherein the diffusion source is composed of RE, Ga, Cu, and Al in a mass ratio of 87–93:3–5:3–5:1.5–2.5; RE is selected from at least two of Pr, Dy, and Tb, and must contain Pr, with a Pr to RE mass ratio of 9–14:86–97; wherein the weight ratio of the diffusion source to the sintered NdFeB magnet is 0.4–1.2:100. Such a rare earth permanent magnet exhibits good overall magnetic properties and squareness.

[0036] Generally, the rare earth elements include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), as well as scandium (Sc) and yttrium (Y). In this invention, R is one or more of any rare earth element other than the heavy rare earth elements Dy, Tb, and Ho, and must contain Nd. Preferably, R is selected from one or more of Pr, Nd, La, Ce, Er, and Y, and must contain Nd.

[0037] According to a specific embodiment of the present invention, in the sintered NdFeB magnet, R is Pr and Nd.

[0038] In this invention, based on the weight of the sintered NdFeB magnet, the R content can be 30-33 wt%, preferably 30.5-32 wt%, more preferably 31-31.8 wt%, for example 31 wt%, 31.3 wt%, 31.4 wt%, 31.5 wt%, 31.6 wt%, 31.7 wt%, and 31.8 wt%.

[0039] In this invention, B represents boron. Based on the weight of the sintered NdFeB magnet, the B content is 0.91–0.95 wt%, preferably 0.91–0.93 wt%, and more preferably 0.91–0.92 wt%. If the B content is outside the range of this invention, it will lead to a decrease in overall magnetic properties and squareness.

[0040] In this invention, Co is cobalt. Based on the weight of the sintered NdFeB magnet, the Co content is 0.95 to 1.5 wt%, preferably 1 to 1.3 wt%, more preferably 1 to 1.2 wt%, for example, 1 wt%, 1.1 wt%, or 1.2 wt%.

[0041] In this invention, Cu is copper. Based on the weight of the sintered NdFeB magnet, the Cu content is 0.1–0.25 wt%, preferably 0.15–0.23 wt%, more preferably 0.18–0.22 wt%, for example, 0.18 wt%, 0.19 wt%, 0.20 wt%, 0.21 wt%, and 0.22 wt%. If the Cu content is outside the range of this invention, it will lead to a decrease in overall magnetic properties and squareness.

[0042] In this invention, Zr is zirconium. Based on the weight of the sintered NdFeB magnet, the Zr content is 0.08–0.22 wt%, preferably 0.09–0.2 wt%, and more preferably 0.1–0.15 wt%.

[0043] In this invention, Ga refers to gallium. Based on the weight of the sintered NdFeB magnet, the Ga content is 0.08–0.25 wt%, preferably 0.09–0.2 wt%, more preferably 0.1–0.15 wt%, and even more preferably 0.1–0.12 wt%. If the Ga content is outside the range of this invention, it will lead to a decrease in overall magnetic properties and squareness.

[0044] According to a specific embodiment of the present invention, based on the weight of the sintered NdFeB magnet, the R content is 30.5-32 wt%, the B content is 0.91-0.93 wt%, the Co content is 1-1.3 wt%, the Cu content is 0.15-0.23 wt%, the Zr content is 0.09-0.2 wt%, the Ga content is 0.09-0.2 wt%, and the Fe is the balance.

[0045] When using the diffusion source of the present invention, the sintered NdFeB magnet of the present invention is more conducive to improving the overall magnetic properties and squareness of the resulting rare earth permanent magnet.

[0046] In this invention, the diffusion source can be composed of RE, Ga, Cu, and Al in a mass ratio of 87–93:3–5:3–5:1.5–2.5. Preferably, the mass ratio of RE, Ga, Cu, and Al is 88–92:3.5–4.5:3.5–4.5:1.7–2.3. More preferably, the mass ratio of RE, Ga, Cu, and Al is 90–92:4–4.2:4–4.2:1.8–2. In the diffusion source, preferably, the mass ratio of Pr to RE is 10–13.5:89–94.5. In some specific embodiments, RE is Pr and Dy, and the mass ratio of Pr to Dy is 9–14:77–83. Preferably, the mass ratio of Pr to Dy is 10–13.5:79–81. More preferably, the mass ratio of Pr to Dy is 10–12:80–81. In some other specific implementations, RE is Pr and Tb, with a mass ratio of Pr to Tb of 9–14:77–83.

[0047] According to a specific embodiment of the present invention, in the diffusion source, the mass ratio of RE, Ga, Cu and Al is 88-92:3.5-4.5:3.5-4.5:1.7-2.3, wherein RE is Pr and Dy, and the mass ratio of Pr and Dy is 9-14:77-83.

[0048] The present invention has found that if the composition of the diffusion source is not within the scope of the present invention, the comprehensive magnetic properties and squareness of the obtained rare earth permanent magnet cannot be improved more significantly, the utilization efficiency of heavy rare earth cannot be improved more effectively, and the technical effects of the present invention cannot be obtained.

[0049] In this invention, the weight ratio of the diffusion source to the sintered NdFeB magnet is preferably 0.6–1.2:100, more preferably 0.7–1.1:100, and even more preferably 0.8–0.9:100. This composition and the amount of diffusion source used are beneficial for achieving higher overall magnetic properties and squareness of the resulting rare-earth permanent magnet, and also for improving the utilization efficiency of heavy rare earth elements.

[0050] <Methods for Preparing Rare Earth Permanent Magnets>

[0051] This invention also provides a method for preparing the rare-earth permanent magnet as described above, the method comprising the following steps: (1) preparation of an initial sintered NdFeB magnet; (2) processing steps; (3) attachment steps; and (4) diffusion heat treatment steps. The method of this invention is beneficial for improving the overall magnetic properties and squareness of the obtained rare-earth permanent magnet, and for improving the utilization efficiency of heavy rare earth elements. A detailed description follows.

[0052] Preparation of initial sintered NdFeB magnets

[0053] Initial sintered NdFeB magnets are prepared from raw materials including R, B, Cu, Ga, Co, Zr, and Fe.

[0054] The initial sintered NdFeB magnet of the present invention is composed of R, B, Co, Cu, Zr, Ga, Fe, and unavoidable impurities; wherein R is one or more rare earth elements other than heavy rare earth elements Dy, Tb, and Ho, and must contain Nd; based on the weight of the initial sintered NdFeB magnet, the R content is 30-33 wt%, the B content is 0.91-0.95 wt%, the Co content is 0.95-1.5 wt%, the Cu content is 0.1-0.25 wt%, the Zr content is 0.08-0.22 wt%, the Ga content is 0.08-0.25 wt%, and the balance is Fe. The composition of the initial sintered NdFeB magnet is the same as that of the sintered NdFeB magnet; therefore, the detailed description of the composition of the initial sintered NdFeB magnet is described above and will not be repeated here.

[0055] According to one embodiment of the present invention, raw materials for an initial sintered NdFeB magnet, comprising R, B, Cu, Ga, Co, Zr, and Fe, are sequentially melted, hydrogen-crushed, and jet-milled to obtain magnetic powder with an average particle size of less than or equal to 10 μm; the magnetic powder is pressed into a blank to obtain a green body; and the green body is sintered to obtain an initial sintered NdFeB magnet. Specifically, the process includes: a melting process; a crushing process and a jet-milling process; a pressing process; and a sintering process.

[0056] The smelting process, hydrogen crushing, and air jet milling can all be performed using those known in the art. The raw materials for the initially sintered NdFeB magnets are smelted to obtain alloy sheets. Smelting can be carried out in a vacuum or inert atmosphere. The alloy sheets are hydrogen crushed into coarse magnetic powder. The coarse magnetic powder is then passed through an air jet mill to form magnetic powder. The average particle size of the coarse magnetic powder is 20–300 μm, preferably 50–300 μm, more preferably 80–300 μm. The average particle size of the magnetic powder is less than or equal to 10 μm, preferably 1–10 μm, more preferably 3–6 μm.

[0057] Magnetic powder is pressed in a magnetic field and then subjected to isostatic pressing to obtain a green body. To prevent oxidation of the magnetic powder, pressing and isostatic pressing are carried out in a vacuum or inert atmosphere. Molding pressing is preferred. The orientation magnetic field direction is parallel or perpendicular to the magnetic powder pressing direction. To obtain high remanence, a certain orientation magnetic field strength is required, preferably greater than 1.0T, more preferably greater than 1.5T, and even more preferably greater than 1.7T.

[0058] The blank is vacuum sintered to obtain an initial sintered NdFeB magnet. The vacuum degree during sintering is less than or equal to 0.1 Pa, preferably less than or equal to 0.01 Pa, and more preferably less than or equal to 0.001 Pa. The sintering temperature can be 950–1150 °C, preferably 980–1100 °C, and more preferably 1000–1070 °C. The sintering time can be 2–10 h, preferably 3–8 h, and more preferably 4–7 h. The density of the resulting initial sintered NdFeB magnet is greater than or equal to 7.2 g / cm³. 3 For example, it can be 7.55 g / cm³. 3 .

[0059] Processing steps

[0060] The initial sintered NdFeB magnet is processed so that the thickness of the magnet in at least one direction is less than 12 mm (this direction can be an orientation direction or not an orientation direction) to obtain a sintered NdFeB magnet.

[0061] In this invention, preferably, the thickness of the magnet in at least one direction is less than 10 mm, more preferably, the thickness of the magnet in at least one direction is less than 6 mm.

[0062] In some embodiments, the processed sintered NdFeB magnets are rectangular parallelepipeds. Specific processing methods are employed as known in the art.

[0063] According to one specific embodiment of the present invention, before processing, the initial sintered NdFeB magnet is in the shape of a cuboid, with its length greater than its width, its width greater than its height, and its height greater than or equal to 30 mm. After processing, the sintered NdFeB magnet is in the shape of a cuboid, with its height less than 12 mm.

[0064] In other embodiments, the processed sintered NdFeB magnet is cylindrical with a height of less than 12 mm (i.e., a thickness of less than 12 mm).

[0065] Attachment process

[0066] A diffusion source is attached to two opposing surfaces of a sintered NdFeB magnet, perpendicular to surfaces with a thickness of less than 12 mm, to obtain an attached magnet; wherein the weight ratio of the diffusion source to the sintered NdFeB magnet is 0.4–1.2:100. This is beneficial for improving the overall magnetic properties and squareness of the resulting rare-earth permanent magnet, and also for improving the utilization efficiency of heavy rare earth elements.

[0067] The specific composition and amount of the diffusion source are detailed above and will not be repeated here.

[0068] In this invention, the attachment method is not particularly limited and can be any method known in the art. According to one embodiment of the invention, the attachment method is selected from at least one of spraying, magnetron sputtering, and screen printing. According to a specific embodiment of the invention, the diffusion sources of RE, Ga, Cu, and Al can be formed into powder and attached by spraying to two opposing surfaces of a sintered NdFeB magnet in a direction perpendicular to a thickness of less than 12 mm.

[0069] Diffusion heat treatment process

[0070] The attached magnet is kept at 500–1000℃ for 0.5–20 hours, cooled to below 80℃, and then kept at 400–700℃ for 0.5–10 hours to obtain a rare-earth permanent magnet. This method is beneficial for obtaining a rare-earth permanent magnet with stable performance.

[0071] In this invention, the holding temperature for diffusion heat treatment can be 500–1000°C, preferably 700–950°C, and more preferably 850–900°C. The holding time can be 0.5–20 h, preferably 2–15 h, and more preferably 5–10 h. After the heat treatment holding is completed, the temperature is lowered to below 80°C, preferably below 60°C, for example, to room temperature. Then, the temperature is raised to 400–700°C for holding, preferably 450–650°C, and more preferably 500–600°C. The holding time can be 0.5–10 h, preferably 2–8 h, more preferably 4–7 h, and more preferably 5–6 h.

[0072] <Applications>

[0073] This invention provides the use of a diffusion source in simultaneously improving the overall magnetic properties and squareness of rare-earth permanent magnets. The diffusion source comprises RE, Ga, Cu, and Al in a mass ratio of 87–93:3–5:3–5:1.5–2.5, wherein RE is selected from at least two of Pr, Dy, and Tb, and must contain Pr; the mass ratio of Pr to RE is 9–14:86–97. The invention includes the following steps:

[0074] (1) Initial sintered NdFeB magnets are prepared from raw materials including R, B, Cu, Ga, Co, Zr and Fe.

[0075] (2) The initial sintered NdFeB magnet is processed so that the thickness of the magnet in at least one direction is less than 12 mm, thus obtaining a sintered NdFeB magnet;

[0076] (3) Attach the diffusion source to two opposite surfaces of the sintered NdFeB magnet in a direction perpendicular to the thickness of less than 12 mm to obtain the attached magnet; wherein the weight ratio of the diffusion source to the sintered NdFeB magnet is 0.4 to 1.2:100;

[0077] (4) The attached magnet is kept at 500-1000℃ for 0.5-20h, cooled to below 80℃, and then kept at 400-700℃ for 0.5-10h to obtain a rare earth permanent magnet;

[0078] R is one or more rare earth elements other than heavy rare earth elements Dy, Tb, and Ho, and must contain Nd. Based on the weight of the initial sintered NdFeB magnet, the R content is 30–33 wt%, the B content is 0.91–0.95 wt%, the Co content is 0.95–1.5 wt%, the Cu content is 0.1–0.25 wt%, the Zr content is 0.08–0.22 wt%, the Ga content is 0.08–0.25 wt%, and the balance is Fe. This specific composition of the diffusion source is beneficial for improving the overall magnetic properties and squareness of the resulting magnet when used as a diffusion source for sintered NdFeB magnets with this specific composition, and also for improving the utilization efficiency of heavy rare earth elements. A detailed description is provided above and will not be repeated here. The composition of the initial sintered NdFeB magnet is the same as that of the sintered NdFeB magnet; therefore, a detailed description of the composition of the initial sintered NdFeB magnet is provided above and will not be repeated here.

[0079] <Testing Methods>

[0080] Performance determination: The magnetic properties of rare-earth permanent magnets were measured at room temperature using a BH magnetometer, and the maximum energy product (BH) was then obtained. max (Unit: MGOe), intrinsic coercivity Hcj (unit: kOe), and squareness Hk / Hcj.

[0081] Among them, (BH) max The sum of the values ​​of and Hcj is denoted as (BH). max +Hcj represents the overall magnetic properties of rare-earth permanent magnets. (BH) max The sum of the values ​​of Hcj and Dy, divided by the amount of Dy, is denoted as [(BH). max The amount of heavy rare earth elements (+Hcj] / Dy represents the utilization efficiency of heavy rare earth elements, which can also be referred to as the Dy utilization efficiency in the following examples and comparative examples.

[0082] Example 1

[0083] 1) Preparation of initial sintered NdFeB magnets:

[0084] Raw materials were prepared by weight percentage using 31.5 wt% PrNd (Pr to Nd weight ratio of 1:3), 0.92 wt% B, 1.0 wt% Co, 0.20 wt% Cu, 0.15 wt% Zr, 0.10 wt% Ga, and the balance Fe. The raw materials were then melted in a vacuum melting and rapid solidification furnace to produce alloy sheets with an average thickness of 0.3 mm. The alloy sheets were then subjected to hydrogen absorption and dehydrogenation treatment in a hydrogen crushing furnace to form coarse magnetic powder of approximately 300 μm. This coarse magnetic powder was then ground in a nitrogen-mediated air jet mill to an average particle size of 4.0 μm. The magnetic powder was then oriented and formed into a billet under a 1.8 T magnetic field in a nitrogen-protected forming press. The density of the resulting billet was 4.3 g / cm³. 3 The blank was placed in a vacuum sintering furnace with a vacuum degree of less than 0.1 Pa and sintered at 1070℃ for 5 hours to obtain the initial sintered NdFeB magnet. Its density is 7.55 g / cm³. 3 It is rectangular in shape and measures 50mm × 40mm × 30mm.

[0085] 2) Processing steps: The initial sintered NdFeB magnet is cut and processed to obtain a cuboid-shaped sintered NdFeB magnet with dimensions of 38mm×23.5mm×5mm.

[0086] 3) Adhesion process: The composition of the diffusion source, by weight percentage, is Pr 10 Dy 80 The diffusion source, Ga4Cu4Al2, was alloyed into a powder and sprayed onto two opposing surfaces of a sintered NdFeB magnet perpendicular to its 5mm thickness (the dimensions of these two surfaces are 38mm x 23.5mm). The weight ratio of the diffusion source to the sintered NdFeB magnet was 0.8:100.

[0087] 4) Diffusion heat treatment process: The attached magnet is subjected to a vacuum degree of less than 1.0 × 10⁻⁶. -2The rare earth permanent magnet was obtained by holding it at 900℃ for 8 hours, cooling it to room temperature, and then holding it at 500℃ for 5 hours.

[0088] The squareness of the obtained rare earth permanent magnets is shown in Table 2, the comprehensive magnetic properties are shown in Table 3, and the Dy utilization efficiency is shown in Table 4.

[0089] Comparative Example 1

[0090] The only difference from Example 1 is the composition of the diffusion source used. In this comparative example, the diffusion source used is composed of Pr. 60 Dy 30 Ga4Cu4Al2.

[0091] The squareness of the obtained rare earth permanent magnets is shown in Table 2, and the comprehensive magnetic properties are shown in Table 3.

[0092] Comparative Example 2

[0093] The only difference from Example 1 is the composition of the diffusion source used. In this comparative example, the diffusion source used is composed of Pr. 13.9 Dy 80 Ga 0.1 Cu4Al2.

[0094] The squareness of the obtained rare earth permanent magnets is shown in Table 2, the comprehensive magnetic properties are shown in Table 3, and the Dy utilization efficiency is shown in Table 4.

[0095] Comparative Example 3

[0096] The only difference from Example 1 is the composition of the diffusion source used. In this comparative example, the diffusion source used has a composition of Dy. 80 Ga 14 Cu4Al2.

[0097] The squareness of the obtained rare earth permanent magnets is shown in Table 2, the comprehensive magnetic properties are shown in Table 3, and the Dy utilization efficiency is shown in Table 4.

[0098] Comparative Example 4

[0099] The only difference from Example 1 is the composition of the diffusion source used. In this comparative example, the diffusion source used is composed of Pr. 13.9 Dy 80 Ga4Cu 0.1 Al2.

[0100] The squareness of the obtained rare earth permanent magnets is shown in Table 2, the comprehensive magnetic properties are shown in Table 3, and the Dy utilization efficiency is shown in Table 4.

[0101] Comparative Example 5

[0102] The only difference from Example 1 is the composition of the diffusion source used. In this comparative example, the diffusion source used has a composition of Dy. 80 Ga4Cu 14 Al2.

[0103] The squareness of the obtained rare earth permanent magnets is shown in Table 2, the comprehensive magnetic properties are shown in Table 3, and the Dy utilization efficiency is shown in Table 4.

[0104] Comparative Example 6

[0105] The only difference from Example 1 is the composition of the diffusion source used. In this comparative example, the diffusion source used is composed of Pr. 11.9 Dy 80 Ga4Cu4Al 0.1 .

[0106] The squareness of the obtained rare earth permanent magnets is shown in Table 2, the comprehensive magnetic properties are shown in Table 3, and the Dy utilization efficiency is shown in Table 4.

[0107] Comparative Example 7

[0108] The only difference from Example 1 is the composition of the diffusion source used. In this comparative example, the diffusion source used has a composition of Dy. 80 Ga4Cu4Al 12 .

[0109] The squareness of the obtained rare earth permanent magnets is shown in Table 2, the comprehensive magnetic properties are shown in Table 3, and the Dy utilization efficiency is shown in Table 4.

[0110] Table 1. Composition of diffusion sources (by weight)

[0111] Example 1 10 80 4 4 2 Comparative Example 1 60 30 4 4 2 Comparative Example 2 13.9 80 0.1 4 2 Comparative Example 3 0 80 14 4 2 Comparative Example 4 13.9 80 4 0.1 2 Comparative Example 5 0 80 4 14 2 Comparative Example 6 11.9 80 4 4 0.1 Comparative Example 7 0 80 4 4 2

[0112] Comparative Example 8

[0113] The only difference from Example 1 is that the elemental composition of the sintered NdFeB magnet is different.

[0114] In this comparative example, the raw materials were prepared by weight percentage as follows: 31.5 wt% PrNd, 0.92 wt% B, 1.0 wt% Co, 0.20 wt% Cu, 0.15 wt% Zr, 0.30 wt% Ga, and the balance Fe.

[0115] The squareness of the obtained rare earth permanent magnets is shown in Table 2, the comprehensive magnetic properties are shown in Table 3, and the Dy utilization efficiency is shown in Table 4.

[0116] Table 2

[0117]

[0118] As shown in Table 2, the squareness of the magnet after diffusion is low in Comparative Example 1 because the Dy content in the diffusion source is too low.

[0119] In Comparative Examples 2 to 5, when the amount of Ga or Cu in the diffusion source was too small, the squareness was not further improved; when the amount was too large, the squareness was significantly reduced. In Comparative Example 6, the squareness was low because the Al content in the diffusion source was low; in Comparative Example 7, the squareness was significantly reduced because the Al content in the diffusion source was too high.

[0120] In Comparative Example 8, the excessive Ga content in the sintered NdFeB magnet also led to a decrease in squareness.

[0121] Table 3

[0122]

[0123] Note: In Table 3, the maximum magnetic energy product (BH) max The unit for coercivity Hcj is MGOe, and the unit for coercivity Hcj is kOe. In Table 3, only numerical values ​​are used for both in the calculation, without units.

[0124] As shown in Table 3, Example 1 has higher overall magnetic properties.

[0125] Table 4

[0126] Example 1 11799 Comparative Example 2 11611 Comparative Example 3 11116 Comparative Example 4 11569 Comparative Example 5 10996 Comparative Example 6 11517 Comparative Example 7 10577 Comparative Example 8 11396

[0127] Note: In Table 4, the unit of maximum magnetic energy product is MGOe, and only the numerical value is used in the calculation. The unit of Dy is wt%. For example, the amount of diffusion source is 0.8wt% of the magnet weight. If Dy accounts for 80wt% of the diffusion source composition, then the weight of Dy in the diffusion source accounts for 0.64wt% of the magnet weight. Then, the overall magnetic performance is divided by the amount of Dy, which is 0.64%.

[0128] As shown in Table 4, the Dy utilization efficiency of Example 1 is higher than that of Comparative Examples 2-8.

[0129] In summary, the use of a diffusion source with a specific composition in this invention is beneficial to improving the overall magnetic properties and squareness of the obtained rare earth permanent magnet (the parent material is a sintered NdFeB magnet with a specific composition), and also beneficial to improving the utilization efficiency of heavy rare earth elements.

[0130] 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 rare-earth permanent magnet, characterized in that, It is obtained by diffusion of sintered NdFeB magnets with a thickness of less than 12 mm in at least one direction through a diffusion source; The diffusion source is attached to two opposite surfaces of the sintered NdFeB magnet in a direction perpendicular to the thickness of less than 12 mm; The sintered NdFeB magnet is composed of R, B, Cu, Ga, Co, Zr, Fe, and unavoidable impurities; R is one or more rare earth elements other than heavy rare earth elements Dy, Tb, and Ho, and must contain Nd; based on the weight of the sintered NdFeB magnet, the R content is 30-33 wt%, the B content is 0.91-0.95 wt%, the Co content is 0.95-1.5 wt%, the Cu content is 0.1-0.25 wt%, the Zr content is 0.08-0.22 wt%, the Ga content is 0.08-0.25 wt%, and the balance is Fe; The diffusion source is composed of RE, Ga, Cu and Al in a mass ratio of 87-93:3-5:3-5:1.5-2.5; RE is selected from at least two of Pr, Dy and Tb, and must contain Pr, with a mass ratio of Pr to RE of 9-14:86-97; The weight ratio of the diffusion source to the sintered NdFeB magnet is 0.4–1.2:

100.

2. The rare-earth permanent magnet according to claim 1, characterized in that, In the sintered NdFeB magnet, R is Pr and Nd.

3. The rare earth permanent magnet according to claim 1, characterized in that, Based on the weight of the sintered NdFeB magnet, the R content is 30.5–32 wt%, the B content is 0.91–0.93 wt%, the Co content is 1–1.3 wt%, the Cu content is 0.15–0.23 wt%, the Zr content is 0.09–0.2 wt%, the Ga content is 0.09–0.2 wt%, and the Fe content is the balance.

4. The rare-earth permanent magnet according to claim 1, characterized in that, In the diffusion source, the mass ratio of RE, Ga, Cu and Al is 88–92:3.5–4.5:3.5–4.5:1.7–2.

3.

5. The rare-earth permanent magnet according to claim 1, characterized in that, In the diffusion source, the mass ratio of Pr to RE is 10–13.5:89–94.

5.

6. A method for preparing a rare-earth permanent magnet as described in any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Initial sintered NdFeB magnets are prepared from raw materials including R, B, Cu, Ga, Co, Zr and Fe. (2) The initial sintered NdFeB magnet is processed so that the thickness of the magnet in at least one direction is less than 12 mm, thus obtaining a sintered NdFeB magnet; (3) Attach the diffusion source to two opposite surfaces of the sintered NdFeB magnet in a direction perpendicular to the thickness of less than 12 mm to obtain the attached magnet; wherein the weight ratio of the diffusion source to the processed sintered NdFeB magnet is 0.4 to 1.2:100; (4) The attached magnet is kept at 500-1000℃ for 0.5-20h, cooled to below 80℃, and then kept at 400-700℃ for 0.5-10h to obtain a rare earth permanent magnet.

7. The method according to claim 6, characterized in that, In step (3), the attachment method is selected from at least one of spraying, magnetron sputtering and screen printing.

8. The method according to claim 6, characterized in that, In step (4), the attached magnet is kept at 700-1000℃ for 5-15 hours, cooled to below 80℃, and then kept at 450-600℃ for 3-8 hours.

9. The method according to claim 6, characterized in that: In step (1), the raw materials of the initial sintered NdFeB magnet, including R, B, Cu, Ga, Co, Zr and Fe, are melted, hydrogenated and air-jet milled in sequence to obtain magnetic powder with an average particle size of less than or equal to 10 μm; the magnetic powder is pressed into shape to obtain a blank; the blank is sintered to obtain the initial sintered NdFeB magnet. In step (1), the blank is sintered in a vacuum sintering furnace with a vacuum degree of less than or equal to 0.1 Pa, the sintering temperature is 950 to 1150 °C, and the sintering time is 2 to 10 h.

10. The use of a diffusion source in simultaneously improving the overall magnetic properties and squareness of rare-earth permanent magnets, characterized in that, The diffusion source is composed of RE, Ga, Cu and Al in a mass ratio of 87-93:3-5:3-5:1.5-2.5, wherein RE is selected from at least two of Pr, Dy and Tb, and must contain Pr, and the mass ratio of Pr to RE is 9-14:86-97, and a rare earth permanent magnet is prepared by the method described in claim 6.

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