Rare earth permanent magnet and its production method and application

Abstract

The application discloses a rare earth permanent magnet and a preparation method and application thereof. The rare earth permanent magnet comprises the following components: R 30-32wt%; B 0.93-0.96wt%; M 0.07-0.16wt%; Ga 0.12-0.22wt%; Cu 0.05-0.18wt%; Co 0.2-1.42wt%; Al 0-0.55wt% and not 0; and Fe balance. The rare earth permanent magnet further reduces the content of Dy and has higher remanence and coercive force.

Description

Technical Field

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

[0002] In Re-TB-based rare-earth permanent magnet materials, replacing part of Nd with Dy or Tb can generally improve the coercivity of the magnet. However, this method has some obvious drawbacks: first, Dy is relatively scarce in nature, resulting in high costs; second, Dy and Fe will form antiferromagnetic coupling, which will reduce magnetic properties, especially significantly reduce the energy product.

[0003] CN106298138A discloses a method for manufacturing rare-earth permanent magnets, which can reduce the content of heavy rare earth element Dy, but the Dy content is still relatively high, and the coercivity needs to be further improved. CN110428947A discloses a rare-earth permanent magnet material with a heavy rare earth content greater than 1 wt%, which is still relatively high.

[0004] CN111883327A discloses a permanent magnet that uses a composite gold method to distribute heavy rare earth elements around the main phase grains, reducing the amount of heavy rare earth elements used, but its heavy rare earth content is still relatively high.

[0005] CN111952032A discloses a method for preparing sintered NdFeB permanent magnets, comprising the following steps: Step 1: The raw material of the main phase alloy is rapidly solidified into thin sheets using a rapid solidification thin-sheet process, and then crushed using a hydrogen-based crushing method and an air jet mill; Step 2: The raw material of the additive phase is rapidly solidified into thin sheets using a rapid solidification thin-sheet process, and then crushed using a hydrogen-based crushing method and an air jet mill; Step 3: The additive phase powder is added to the main phase alloy powder, and then mixed uniformly under argon or nitrogen protection; Step 4: Orientation and pressing; Step 5: High-vacuum low-temperature orientation pre-sintering to obtain a green blank; Step 6: Immersion of the green blank in a slurry made of heavy rare earth carbonate nanoparticles; Step 7: Pressure low-temperature sintering; Step 8: Heat treatment to obtain a sintered NdFeB permanent magnet. Although this preparation method can reduce the heavy rare earth content to a certain extent, the process is relatively cumbersome.

[0006] CN113903590A discloses a process for preparing neodymium iron boron permanent magnet materials, including first preparing a main alloy powder, then preparing an auxiliary alloy powder, mixing the two to prepare a blank with uniform density, and then preparing sintered neodymium iron boron permanent magnet materials through vacuum sintering and tempering. Although this process does not add heavy rare earth elements, the intrinsic coercivity of the permanent magnet material is significantly reduced. Summary of the Invention

[0007] In view of this, one object of the present invention is to provide a rare-earth permanent magnet with a further reduced content of heavy rare-earth Dy, and which exhibits high remanence and coercivity. Another object of the present invention is to provide a method for producing the said rare-earth permanent magnet. A further object of the present invention is to provide applications of the said rare-earth permanent magnet. The present invention achieves the above objects through the following technical solutions.

[0008] On one hand, the present invention provides a rare earth permanent magnet, comprising the following components:

[0009] R 30~32wt%,

[0010] B 0.93~0.96wt%,

[0011] M 0.07~0.16wt%,

[0012] Ga 0.12~0.22wt%,

[0013] Cu 0.05–0.18 wt%,

[0014] Co 0.2–1.42 wt%,

[0015] Al 0–0.55 wt%, and not 0,

[0016] Fe balance;

[0017] Wherein, R is a rare earth element, and R includes at least Nd; R includes RH, and RH is a heavy rare earth element;

[0018] Among them, based on the total weight of rare earth permanent magnets, the RH content is less than 0.5 wt%;

[0019] Among them, based on the total weight of rare earth permanent magnets, the Dy content in RH is less than 0.1 wt%;

[0020] Wherein, M is Zr and / or Ti.

[0021] The rare-earth permanent magnet according to the present invention is preferably:

[0022] M is Zr;

[0023] The R also includes Pr;

[0024] The RH also includes Ho, and the content of Ho is greater than 0.01 wt% and less than 0.5 wt%.

[0025] On the other hand, the present invention also provides a method for producing the rare earth permanent magnet as described above, comprising the following steps:

[0026] 1) Melting and spinning process: The molten magnetic raw material is poured onto a rotating copper roller, cooled and formed into a spinning sheet;

[0027] The surface roughness of the rotating copper roller is 3.2–12.5 μm; the average thickness of the resulting spun blade is 0.26–0.34 mm.

[0028] 2) Magnetic powder forming process: The obtained spun wafers are subjected to hydrogen crushing to obtain alloy powder; the alloy powder is then used to form magnetic powder using a nested air jet mill.

[0029] The alloy powder has an average particle size of 50–1000 μm; the magnetic powder has an average particle size of 2.0–2.5 μm; and the magnetic powder has a D90 / D10 ratio of 3.5–4.2.

[0030] According to the production method of the present invention, preferably, the nested air jet mill includes a grinding chamber and a nested sorting unit;

[0031] The nested sorting unit includes a first sorting wheel, a second sorting wheel, a material distribution cylinder, and a material discharge cylinder;

[0032] The first sorting wheel is used to prevent particles larger than a set particle size from entering the nested sorting unit;

[0033] The second sorting wheel is used to sort out particles smaller than the set particle size and discharge them into the dispensing cylinder;

[0034] The dispensing cylinder is used to discharge particles smaller than a set particle size;

[0035] The discharge cylinder is used to collect magnetic powder of a set particle size;

[0036] The first sorting wheel surrounds the outer periphery of the second sorting wheel, the first sorting wheel is connected to the discharge cylinder, and the second sorting wheel is connected to the distribution cylinder; the discharge cylinder surrounds the outer periphery of the distribution cylinder, and the outlet of the distribution cylinder extends to the outside of the discharge cylinder.

[0037] According to the production method of the present invention, preferably:

[0038] The outer contour of the grinding chamber is composed of a connected cylindrical structure and an inverted conical cylinder structure; the cylindrical structure is located above the conical cylinder structure.

[0039] The grinding chamber has an airflow inlet and a feeding port; the airflow inlet is disposed on the conical cylinder structure; the feeding port is located below the airflow inlet and is disposed on the conical cylinder structure, and is used to add the alloy powder into the grinding chamber.

[0040] According to the production method of the present invention, preferably, in the melting and spinning process, the magnet raw material is melted at 1350-1550°C under argon protection.

[0041] According to the production method of the present invention, preferably, it further includes the following steps:

[0042] 3) Molding process: The magnetic powder is pressed into a green blank;

[0043] 4) Sintering process: sintering the green blank to form a sintered magnet; and

[0044] 5) Tempering process: The sintered magnet is tempered to obtain the rare earth permanent magnet.

[0045] According to the production method of the present invention, preferably:

[0046] The magnetic powder is pressed into a green blank under the action of an orientation magnetic field with a magnetic field strength greater than 1.6T;

[0047] The sintering process includes: sintering the green blank under a vacuum of 1×10⁻⁶. -2 Sintering begins at a temperature below Pa, held at 300–350℃ for 1–2 hours, held at 500–650℃ for 1–2 hours, held at 800–900℃ for 3–5 hours, and then held at 1000–1100℃ for 1–6 hours.

[0048] According to the production method of the present invention, preferably, the tempering process includes: holding at 850-950°C for 1.5-4 hours, filling with inert gas, and air-cooling to below 150°C; then holding at 450-650°C for 2-5 hours.

[0049] In another aspect, the present invention also provides the application of the rare earth permanent magnets described above in automobile drive motors, hydroelectric generators, wind turbine generators, compressor motors and marine propulsion motors.

[0050] The rare-earth permanent magnet of the present invention further reduces the content of heavy rare-earth Dy, while maintaining high remanence and coercivity. Furthermore, the Tb content is further reduced. The production method of the rare-earth permanent magnet of the present invention further reduces the heavy rare-earth content and forms a high-performance rare-earth permanent magnet by further controlling the surface roughness of the rotating copper roller in the melting and slagging process and by using a nested air jet mill to prepare magnetic powder within a specific particle size range. Attached Figure Description

[0051] Figure 1 This is a metallographic diagram of the wafer obtained in Example 1 of the present invention.

[0052] Figure 2 This is a schematic diagram of the structure of a nested airflow mill device according to the present invention.

[0053] Figure 3 This is a photograph showing the grain size of the rare-earth permanent magnet in Example 1 of the present invention.

[0054] The annotations in the attached figures are explained as follows:

[0055] 100-Grinding chamber, 200-Nested sorting unit, 211-First sorting wheel, 212-Discharge cylinder, 221-Second sorting wheel, 222-Distribution cylinder, 300-Compressed air unit, 400-Feeding unit, 500-Base. Detailed Implementation

[0056] 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.

[0057] The "average particle size" mentioned in this invention refers to the D50 particle size, which represents the equivalent diameter of the largest particle when the cumulative distribution in the particle size distribution curve is 50%. In this invention, D90 represents the equivalent diameter of the largest particle when the cumulative distribution in the particle size distribution curve is 90%, and D10 represents the equivalent diameter of the largest particle when the cumulative distribution in the particle size distribution curve is 10%.

[0058] The "remanence" mentioned in this invention refers to the magnetic flux density corresponding to the point where the magnetic field strength is zero on the saturation hysteresis loop, usually denoted as Br, with units of Tesla (T) or Gauss (Gs). The "coercivity" mentioned in this invention is "intrinsic coercivity," which refers to the magnetic field strength when the magnetic field is monotonically reduced to zero from the saturation magnetization state of the magnet and then increased in the opposite direction, causing its magnetization intensity to decrease to zero along the saturation hysteresis loop, usually denoted as Hcj, with units of Oersted (Oe).

[0059] Unless otherwise stated, the content of each component is based on the total weight of the rare earth permanent magnet.

[0060] Rare Earth Permanent Magnets

[0061] The rare-earth permanent magnet of the present invention is an RTB-based permanent magnet. The rare-earth permanent magnet of the present invention comprises the following components: R, B, M, Ga, Cu, Co, Al, and Fe. The rare-earth permanent magnet of the present invention may also contain unavoidable impurities. Preferably, the rare-earth permanent magnet of the present invention is composed of the following components: R, B, M, Ga, Cu, Co, Al, and Fe.

[0062] In this invention, R represents a rare earth element. R can be 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), yttrium (Y), and scandium (Sc). R includes both light rare earth elements and heavy rare earth elements (RH). Light rare earth elements can be lanthanum, cerium, praseodymium, neodymium, promethium, samarium, and europium. Heavy rare earth elements (RH) can be gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

[0063] In this invention, R includes Nd, and preferably, R includes Nd and Pr. In some specific embodiments, the light rare earth elements in R are only Nd and Pr. The heavy rare earth elements RH may include Dy, Tb and / or Ho. Preferably, the heavy rare earth elements RH include only Dy, Tb and Ho.

[0064] The content of R can be 30-32 wt%, preferably 30.5-32 wt%, more preferably 31-32 wt%, and even more preferably 31.3-31.8 wt%, for example 31.51 wt%.

[0065] Based on the total weight of the rare earth permanent magnet, the content of heavy rare earth element RH is less than 0.5 wt%. Preferably, the content of heavy rare earth element RH is not 0.

[0066] Based on the total weight of the rare earth permanent magnet, the Dy content in the heavy rare earth element RH can be less than 0.1 wt%, preferably less than 0.06 wt%; more preferably, less than or equal to 0.055 wt%, and even more preferably, less than or equal to 0.05 wt% and not 0.

[0067] Based on the total weight of the rare earth permanent magnets, the Tb content in RH can be greater than 0.06 wt% and less than 0.12 wt%; preferably, greater than 0.07 wt% and less than 0.11 wt%; more preferably, greater than 0.08 wt% and less than or equal to 0.1 wt%.

[0068] Based on the total weight of the rare earth permanent magnet, the Ho content in RH can be greater than 0.01 wt% and less than 0.5 wt%, preferably greater than 0.04 wt% and less than 0.5 wt%, more preferably greater than 0.05 wt% and less than 0.45 wt%, even more preferably greater than 0.06 wt% and less than 0.4 wt%, and even more preferably greater than 0.08 wt% and less than 0.4 wt%.

[0069] In this invention, the content of B can be 0.93 to 0.96 wt%, preferably 0.94 to 0.96 wt%, and more preferably 0.95 to 0.96 wt%.

[0070] In this invention, M is selected from at least one of Zr and Ti. Preferably, M is Zr. The content of M can be 0.07 to 0.16 wt%, more preferably 0.08 to 0.15 wt%, and even more preferably 0.1 to 0.14 wt%.

[0071] In this invention, the content of Ga can be 0.12 to 0.22 wt%, preferably 0.14 to 0.21 wt%, more preferably 0.16 to 0.2 wt%, and even more preferably 0.17 to 0.19 wt%.

[0072] In this invention, the Cu content can be 0.05 to 0.18 wt%, preferably 0.07 to 0.18 wt%, and more preferably 0.1 to 0.178 wt%.

[0073] In this invention, the content of Co can be 0.2 to 1.42 wt%, preferably 0.5 to 1.41 wt%, more preferably 0.9 to 1.42 wt%, and even more preferably 1.1 to 1.42 wt%.

[0074] In this invention, the Al content can be 0 to 0.55 wt%, and is not 0; preferably 0.01 to 0.55 wt%, more preferably 0.08 to 0.5 wt%.

[0075] Using the above formula is beneficial to improving the remanence and coercivity of rare earth permanent magnets.

[0076] <Production Methods>

[0077] The method for producing rare earth permanent magnets according to the present invention includes: 1) a melting and spinning process; and 2) a magnetic powder forming process. Optionally, the method of the present invention further includes 3) a forming process; 4) a sintering process; and 5) a tempering process. These are described in detail below.

[0078] Melting and strip casting process

[0079] The melting and spinning process of the present invention is as follows: the molten magnetic raw material is poured onto a rotating copper roller, cooled and formed into a spinning sheet.

[0080] The surface roughness Ra of the rotating copper roller of the present invention is 3.2–12.5 μm, preferably 4.5–10 μm, and more preferably 5.5–8.5 μm. This is beneficial for obtaining spun sheets with uniform thickness distribution and good microstructure consistency.

[0081] The average thickness of the obtained spun magnet can be 0.26–0.34 mm, preferably 0.27–0.33 mm, and more preferably 0.28–0.33 mm. In the metallographic structure of the spun magnet obtained by the present invention, the main phase grains are uniformly separated into 3–5 μm lamellar crystals by a thin layer of Nd-rich phase. This is beneficial for obtaining magnetic powder with uniform particle size. When the thickness is too large, dendritic α-Fe phase will appear in the spun magnet fiber structure. Its appearance will lead to a reduction in the main phase and an increase in the Nd-rich phase, resulting in a decrease in hard magnetic properties; if the thickness is too thin, it will affect the grain orientation of the magnet and is not conducive to improving remanence.

[0082] The melting and spinning process of the present invention is carried out in a vacuum or inert atmosphere, which can prevent the magnet raw material and the spools made therefrom from being oxidized.

[0083] The melting and spinning process of this invention can be carried out in a vacuum medium-frequency rapid solidification induction furnace. The melting temperature of this invention can be 1350-1550℃, preferably 1450-1500℃. According to one embodiment of the invention, in the melting and spinning process, the magnetic raw material is melted at 1450-1500℃ under argon protection at 0.04-0.06 MPa. According to a specific embodiment of the invention, the raw material is placed in a vacuum medium-frequency rapid solidification induction furnace, evacuated to below 1 Pa, and then filled with argon (Ar) for protection up to 0.04-0.06 MPa. The furnace is then heated and melted, and the melted alloy is poured onto a rotating copper roller with a surface roughness Ra of 3.2-12.5 μm to prepare a spinning sheet with a thickness of 0.26-0.34 mm.

[0084] Magnetic powder forming process

[0085] In this invention, the obtained wafers are subjected to hydrogen crushing to obtain alloy powder; the alloy powder is then used to form magnetic powder using a nested air jet mill. To prevent oxidation of the wafers, alloy powder, and magnetic powder obtained from their crushing, the magnetic powder forming process of this invention is carried out in a vacuum or inert atmosphere.

[0086] In the hydrogen crushing process of this invention, the hydrogen crushing process first involves absorbing hydrogen at a low temperature into the spun alloy (master alloy). The reaction between the master alloy and hydrogen gas induces volume expansion of the master alloy lattice, causing the master alloy to break down into alloy powder. Then, the alloy powder is heated for high-temperature dehydrogenation. According to a preferred embodiment of this invention, the hydrogen crushing is preferably carried out in a hydrogen crushing furnace. In the hydrogen crushing process of this invention, the hydrogen absorption temperature is 20°C to 400°C, preferably 20°C to 100°C; the hydrogen absorption pressure is 50°C to 600 kPa, preferably 100°C to 300 kPa; and the dehydrogenation temperature is 400°C to 850°C, preferably 500°C to 700°C.

[0087] The average particle size of the alloy powder can be 50-1000 μm, preferably 80-800 μm, and more preferably 100-500 μm.

[0088] This invention employs an air jet milling process to grind the alloy powder into magnetic powder. The air jet milling process utilizes an airflow to accelerate the alloy powder, causing it to collide and break apart. The airflow can be a nitrogen stream, preferably a high-purity nitrogen stream. The N2 content in the high-purity nitrogen stream can be above 99.0 wt%, preferably above 99.9 wt%. The pressure of the airflow can be 0.1–2.0 MPa, preferably 0.5–1.0 MPa, and more preferably 0.6–0.7 MPa.

[0089] The present invention preferably uses a nested airflow mill to form magnetic powder from alloy powder (i.e., the powder to be ground).

[0090] The nested air jet mill device of the present invention includes a grinding chamber, a nested sorting unit, a compressed air unit, a feeding unit, and a base.

[0091] The grinding chamber is used to grind alloy powder (the powder to be ground) to obtain ground magnetic alloy powder. The outer contour of the grinding chamber consists of a connected cylindrical structure and an inverted conical structure. The cylindrical structure is located above the conical structure. The grinding chamber has an airflow inlet and a feeding port. The airflow inlet is located on the conical structure. A compressed air unit can introduce high-pressure airflow into the grinding chamber through the airflow inlet. There are at least two airflow inlets, which are evenly distributed. The feeding port may be located below one of the airflow inlets and is located on the conical structure; it is used to add the powder to be ground (i.e., alloy powder) into the grinding chamber. A feeding unit adds the alloy powder into the grinding chamber through the feeding port. The feeding unit may include a feeding screw.

[0092] The nested sorting unit is used to sort the ground magnetic alloy powder to obtain magnetic powder of a set particle size. The nested sorting unit includes a first sorting wheel, a second sorting wheel, a distribution cylinder, and a discharge cylinder. The first sorting wheel prevents particles larger than the set particle size from entering the nested sorting unit. The second sorting wheel sorts out particles smaller than the set particle size and discharges them into the distribution cylinder. The distribution cylinder discharges particles smaller than the set particle size. The discharge cylinder collects the magnetic powder of the set particle size.

[0093] The first sorting wheel surrounds the outer circumference of the second sorting wheel. Both the first and second sorting wheels are arranged horizontally. The first sorting wheel is connected to the discharge cylinder. The length directions of the first sorting wheel and the discharge cylinder are the same, and their central axes can coincide.

[0094] The second sorting wheel and the dispensing cylinder are aligned in length, and their central axes can coincide. According to one embodiment of the present invention, the diameter of the second sorting wheel is one-half to three-quarters of the diameter of the first sorting wheel, preferably two-thirds to three-quarters.

[0095] The discharge cylinder surrounds the outer circumference of the distribution cylinder, and the outlet of the distribution cylinder extends to the outside of the discharge cylinder. The first sorting wheel blocks the entry of large particles, while the second sorting wheel effectively discharges ultrafine powder (or ultrafine particles, which are nano-sized particles or particles smaller than 1 micrometer). By controlling the structural differences between the first and second sorting wheels and controlling the rotation speed of the sorting wheels, the particle size and distribution of the magnetic powder can be effectively controlled, thereby obtaining magnetic powder of a set particle size.

[0096] In this invention, the rotational clearance of the first sorting wheel can be 0.1–0.15 mm. The rotational clearance of the second sorting wheel can be 0.1–0.15 mm.

[0097] The air classifier mill apparatus of the present invention further includes an air classifier outlet. There can be two air classifier outlets, respectively located at the outlet of the distribution cylinder and the outlet of the discharge cylinder. In some embodiments, the outlet of the distribution cylinder and the outlet of the discharge cylinder serve as air classifier outlets.

[0098] The nested air jet mill of the present invention can obtain magnetic powder with fine particle size and good distribution.

[0099] The air jet mill can operate at speeds of 2500–3500 r / min. The working pressure is 0.55–0.65 MPa.

[0100] In this invention, the average particle size of the obtained magnetic powder is 2.0–3.5 μm, preferably 2.3–3.0 μm, and more preferably 2.4–2.6 μm. The D90 / D10 ratio of the obtained magnetic powder is 3.4–4.2, preferably 3.5–4.1, and more preferably 3.6–4.0. This is beneficial for further reducing the heavy rare earth content and obtaining high-performance magnets.

[0101] The smaller the D90 / D10 ratio, the better the particle size uniformity.

[0102] Molding process

[0103] The molding process of the present invention is as follows: pressing the magnetic powder into a green blank.

[0104] The magnetic powder is pressed into a green body under the action of an orientation magnetic field with a strength greater than 1.6T. To prevent oxidation of the magnetic powder, the forming process of the present invention is carried out in a vacuum or inert atmosphere. In the forming process, the magnetic powder pressing process preferably employs a molding pressing process and / or an isostatic pressing process. The isostatic pressing process of the present invention can be carried out in an isostatic press (e.g., a cold isostatic press). The pressure can be 10-100MPa, preferably 15-50MPa, more preferably 18-25MPa; the holding time is 10-100s, preferably 30-60s. According to a preferred embodiment of the present invention, firstly, the magnetic powder is pressed using a molding pressing process, and then the magnetic powder is pressed using an isostatic pressing process. In the forming process of the present invention, the orientation magnetic field direction is parallel to or perpendicular to the magnetic powder pressing direction. In the present invention, the strength of the orientation magnetic field is at least 1.6 Tesla (T), preferably at least 1.8T. Preferably, the molded green compact is removed and vacuum-sealed, then placed in an isostatic press and pressurized to 18–25 MPa. After holding the pressure, the green compact is removed. In this invention, the density of the green compact can be 4.0–7.0 g / cm³. 3 The preferred concentration is 4.2–5.5 g / cm³. 3 .

[0105] Sintering process

[0106] The green blank is sintered to form a sintered magnet.

[0107] To prevent oxidation of the green blank during sintering, the sintering process of the present invention is carried out in a vacuum or inert atmosphere. According to a preferred embodiment of the present invention, the sintering process is carried out in a vacuum sintering furnace. The sintering process of the present invention is as follows: sintering the green blank under vacuum conditions and programmed temperature control to form a sintered magnet.

[0108] In the sintering process of this invention, the vacuum degree can be lower than 1.0 Pa, preferably lower than 5.0 × 10⁻⁶ Pa. -1 Pa. The sintering process of the present invention includes: sintering the green blank under a vacuum of 1×10⁻⁶. -2 Sintering begins at a temperature below Pa, held at 300–350°C for 1–2 hours, then at 500–650°C for 1–2 hours, then at 800–900°C for 3–5 hours, and finally at 1000–1100°C for 1–6 hours. Inert gas is then introduced, followed by air cooling to below 150°C. Preferably, the green compact is sintered under a vacuum of 1×10⁻⁶ Pa. -2Sintering begins at a temperature below Pa, held at 300–330°C for 1–1.5 hours, then at 550–600°C for 1.5–2 hours, then at 850–900°C for 4–5 hours, and finally at 1020–1080°C for 4–5 hours. The mixture is then filled with inert gas and air-cooled to below 150°C. In this invention, the inert gas can be argon.

[0109] Tempering process

[0110] The tempering process of the present invention is as follows: the sintered magnet is tempered to obtain the rare earth permanent magnet.

[0111] The sintered magnet is tempered under vacuum and programmed temperature control to obtain the rare-earth permanent magnet. In the tempering process of this invention, the vacuum level can be below 1.0 Pa, preferably below 5.0 × 10⁻⁶ Pa. -1 Pa. Preferably, the tempering process includes: holding at 850–950°C for 1.5–4 hours, filling with inert gas, and air-cooling to below 150°C; then holding at 450–650°C for 2–5 hours, filling with inert gas, and air-cooling to below 70°C. More preferably, holding at 880–900°C for 2–3 hours, filling with inert gas, and air-cooling to below 150°C; then holding at 500–600°C for 4–5 hours, filling with inert gas, and air-cooling to below 70°C.

[0112] This invention utilizes specific processes and equipment to form magnets with a low content of heavy rare earth elements while simultaneously exhibiting high remanence and coercivity, resulting in magnets with superior performance. This invention can reduce the content of neodymium-rich iron at grain boundaries, forming Nd6Fe at the grain boundaries. 13 The Ga antiferromagnetic phase causes the neodymium-rich phase to transform from ferromagnetic to antiferromagnetic, blocking the exchange coupling of the main phase grains and thus increasing the coercivity of the magnet.

[0113] <Application>

[0114] The present invention also provides the application of the rare earth permanent magnets described above in automobile drive motors, hydroelectric generators, wind turbines, compressor motors and marine propulsion motors.

[0115] Example 1 and Comparative Example 1

[0116] The rare earth permanent magnets of Example 1 and Comparative Example 1 were produced according to the following steps, and the content of each component of the obtained rare earth permanent magnets is shown in Table 1 below.

[0117] (1) Prepare the magnet raw materials according to the magnet composition (i.e., weight percentage), place them in a vacuum medium-frequency rapid solidification induction furnace, evacuate to below 1 Pa, preheat at 120 kW, increase the vacuum, and evacuate again to below 1 Pa. Purge with argon to 0.05 MPa, and then melt at 1450 °C. Pour the melted magnet raw materials (i.e., alloy melt) onto a rotating copper roller with a surface roughness Ra of 6.3 μm to obtain a spun sheet with a thickness of 0.30 mm. The metallographic structure of the spun sheet in Example 1 is shown in [reference needed]. Figure 1 .

[0118] (2) The spun alloy sheet is placed in a hydrogen crushing furnace and crushed into alloy powder of 200 μm through a low-temperature hydrogen absorption and high-temperature dehydrogenation reaction. The alloy powder is mixed and ground into magnetic powder using a nested air jet mill. Magnetic powder with an average particle size of 2.46 μm and D90 / D10 = 3.66 is then screened out. The structure of the nested air jet mill is as follows: Figure 2 As shown below.

[0119] (3) The magnetic powder was mixed evenly, oriented and pressed into shape under a magnetic field strength of 2.0T, vacuum sealed, and then the density was increased in a cold isostatic press to obtain a density of 4.2 g / cm³. 3 The green billet. The holding pressure of cold isostatic pressing is 18 MPa, and the holding time is 30 s.

[0120] (4) Place the green billet in a vacuum sintering furnace and evacuate it to a vacuum level of 1×10⁻⁶. -2 Sintering begins at a temperature below Pa, with holding times of 300℃ for 1 hour and 600℃ for 2 hours. Then, the temperature is held at 850℃ for 4.5 hours, adjusted to 1050℃, held for another 4.5 hours, purged with argon gas, and air-cooled below 150℃.

[0121] (5) In a vacuum of 1×10 -2 The rare earth permanent magnets below Pa underwent a two-stage tempering process. Tempering was performed at 900℃ for 3 hours, followed by argon-filled air cooling below 150℃; tempering was then performed at 550℃ for 5 hours, followed by argon-filled air cooling below 70℃. Performance test results are shown in Table 2. Grain size photographs of the rare earth permanent magnets in Example 1 are shown below. Figure 3 .

[0122] Figure 2 The nested air jet mill includes a grinding chamber 100, a nested sorting unit 200, a compressed air unit 300, a feeding unit 400, and a base 500.

[0123] The grinding chamber 100 grinds alloy powder (i.e., the powder to be ground) to obtain ground magnetic alloy powder. The outer contour of the grinding chamber 100 consists of a connected cylindrical structure and an inverted conical structure. The cylindrical structure is located above the conical structure. The grinding chamber 100 is provided with a feed port and an airflow inlet. There are at least two airflow inlets, which are evenly distributed. The airflow inlets are located on the conical structure of the grinding chamber 100. The compressed air unit 300 includes compressed air nozzles. The number of compressed air nozzles is consistent with the number of airflow inlets. Compressed air is introduced into the airflow inlets of the grinding chamber 100 through the compressed air nozzles.

[0124] The feeding port is located on the conical cylindrical structure of the grinding chamber 100. The feeding port is situated below the airflow inlet. The feeding unit 400 is connected to the feeding port and feeds the powder to be ground (i.e., alloy powder) into the grinding chamber 100. The feeding unit 400 includes a feeding screw. The feeding screw is horizontally positioned. The feeding screw can feed the powder to be ground into the grinding chamber 100.

[0125] The nested sorting unit 200 sorts the ground magnetic alloy powder to obtain magnetic powder of a set particle size. The nested sorting unit 200 is located on top of the grinding chamber 100.

[0126] The nested sorting unit 200 includes a first sorting wheel 211, a second sorting wheel 221, a material distribution cylinder 222, and a discharge cylinder 212.

[0127] The first sorting wheel 211 prevents particles larger than the set particle size from entering the nested sorting unit 200. The second sorting wheel 221 sorts out particles smaller than the set particle size and discharges them into the distribution cylinder 222. The distribution cylinder 222 discharges particles smaller than the set particle size. The discharge cylinder 212 collects magnetic powder of the set particle size.

[0128] The first sorting wheel 211 surrounds the outer periphery of the second sorting wheel 221. Both the first sorting wheel 211 and the second sorting wheel 221 are arranged horizontally. The first sorting wheel 211 is connected to the discharge cylinder 212. The length directions of the first sorting wheel 211 and the discharge cylinder 212 are the same, and their central axes can coincide. The length directions of the second sorting wheel 221 and the distribution cylinder 222 are the same, and their central axes can coincide. The diameter of the second sorting wheel 222 is two-thirds to three-quarters of the diameter of the first sorting wheel 211. The discharge cylinder 212 surrounds the outer periphery of the distribution cylinder 222, and the outlet of the distribution cylinder 222 extends to the outside of the discharge cylinder 212.

[0129] The air jet mill also includes two air jet outlets. The outlet of the feed cylinder 222 and the outlet of the discharge cylinder 212 are also air jet outlets.

[0130] Figure 2In the diagram, the direction of the dashed arrow indicates the airflow direction, and the curved arrow indicates the rotation direction of the first sorting wheel 211 and the second sorting wheel 221.

[0131] The grinding chamber 100 is mounted on the base 500. The base 500 is used to stably support and fix the grinding chamber 100.

[0132] Table 1

[0133]

[0134] Table 2

[0135]

[0136] Comparative Example 2

[0137] According to Example 1 of CN106298138A, the component contents are as follows:

[0138] The composition is as follows: Nd 30.46wt%, B 0.974wt%, Cu 0.097wt%, Co 0.428wt%, Dy 0.746wt%, Al 0.248wt%, Nb 0.284wt%, Ga 0.053wt%, with the balance being Fe. Comparing this to Example 1 of the present invention, it can be seen that, while maintaining essentially the same remanence and meeting practical requirements, the coercivity of the rare-earth permanent magnet of the present invention is significantly improved. More importantly, the Dy content of the rare-earth permanent magnet of the present invention is significantly reduced.

[0139] 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 composed of the following components: R 30~32wt%, B 0.93~0.96wt%, M 0.08~0.16wt%, Ga 0.16~0.2wt%, Cu 0.1–0.18 wt%, Co 1.1~1.42wt%, Al 0.08~0.55wt%, Fe balance; Wherein, R represents rare earth elements, and R includes at least Nd and Pr; R includes RH, which represents heavy rare earth elements; RH includes only Dy, Tb, and Ho; Of these, based on the total weight of the rare earth permanent magnets, the RH content is less than 0.5 wt%; Specifically, based on the total weight of the rare earth permanent magnets, the Dy content in RH is less than or equal to 0.05 wt% and not 0; the Tb content in RH is greater than 0.07 wt% and less than 0.1 wt%; and the Ho content in RH is greater than 0.06 wt% and less than 0.4 wt%. Wherein, M is Zr.

2. The method for producing rare earth permanent magnets according to claim 1, characterized in that, Includes the following steps: 1) Melting and spinning process: The molten magnetic raw material is poured onto a rotating copper roller, cooled and formed into a spun sheet; The surface roughness of the rotating copper roller is 3.2–12.5 μm; the average thickness of the resulting spun ladle is 0.26–0.34 mm. 2) Magnetic powder forming process: The obtained spun wafers are subjected to hydrogen crushing to obtain alloy powder; the alloy powder is then used to form magnetic powder using a nested air jet mill. The alloy powder has an average particle size of 50–1000 μm; the magnetic powder has an average particle size of 2.0–2.5 μm; and the magnetic powder has a D90 / D10 ratio of 3.5–4.

2.

3. The production method according to claim 2, characterized in that, The nested air jet mill includes a grinding chamber and a nested sorting unit; The nested sorting unit is located at the top of the grinding chamber; the nested sorting unit includes a first sorting wheel, a second sorting wheel, a dispensing cylinder, and a discharge cylinder; The first sorting wheel is used to prevent particles larger than a set particle size from entering the nested sorting unit; The second sorting wheel is used to sort out particles smaller than the set particle size and discharge them into the dispensing cylinder; The dispensing cylinder is used to discharge particles smaller than a set particle size; The discharge cylinder is used to collect magnetic powder of a set particle size; The first sorting wheel surrounds the outer periphery of the second sorting wheel, the first sorting wheel is connected to the discharge cylinder, and the second sorting wheel is connected to the distribution cylinder; the discharge cylinder surrounds the outer periphery of the distribution cylinder, and the outlet of the distribution cylinder extends to the outside of the discharge cylinder.

4. The production method according to claim 3, characterized in that: The outer contour of the grinding chamber is composed of a connected cylindrical structure and an inverted conical cylinder structure; the cylindrical structure is located above the conical cylinder structure. The grinding chamber has an airflow inlet and a feeding port; the airflow inlet is disposed on the conical cylinder structure; the feeding port is located below the airflow inlet and is disposed on the conical cylinder structure, and is used to add the alloy powder into the grinding chamber.

5. The production method according to claim 2, characterized in that, In the melting and spinning process, the magnet raw material is melted at 1350-1550°C under argon protection.

6. The production method according to claim 2, characterized in that, It also includes the following steps: 3) Molding process: The magnetic powder is pressed into a green blank; 4) Sintering process: sintering the green blank to form a sintered magnet; and 5) Tempering process: The sintered magnet is tempered to obtain the rare earth permanent magnet.

7. The production method according to claim 6, characterized in that: The magnetic powder is pressed into a green blank under the action of an orientation magnetic field with a magnetic field strength greater than 1.6T; The sintering process includes: sintering the green blank under a vacuum of 1×10⁻⁶. -2 Sintering begins at a temperature below Pa, held at 300–350℃ for 1–2 hours, held at 500–650℃ for 1–2 hours, held at 800–900℃ for 3–5 hours, and then held at 1000–1100℃ for 1–6 hours.

8. The production method according to claim 6, characterized in that, The tempering process includes: holding at 850–950℃ for 1.5–4 hours, filling with inert gas, and air-cooling to below 150℃; then holding at 450–650℃ for 2–5 hours.

9. The application of the rare earth permanent magnet according to claim 1 in automobile drive motors, hydroelectric generators, wind turbine generators, compressor motors and marine propulsion motors.

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