Method for manufacturing rare earth sintered neodymium-iron-boron magnet

Abstract

To provide an (R1, R2)-T-B-M rare earth sintered neodymium-iron-boron magnet that has a low residual magnetic flux temperature coefficient and a coercive force temperature coefficient with coercive force and residual magnetism balanced well, a method for manufacturing the same, and praseodymium hydride.SOLUTION: An element composition of a rare earth sintered neodymium-iron-boron magnet is represented as (R1,R2)-T-B-M), and the element composition of a rare earth sintered neodymium-iron-boron magnet is composed of a sintered body containing principal phase crystal grains and a grain boundary phase, wherein the principal phase crystal grains consist of a (R1,R2)2T14B phase, the Pr concentration C1 at an edge of a principal phase crystal grain is higher than the Pr concentration C2 in the center of the principal phase crystal grain, and the R1 concentration of a grain boundary phase is higher than the R1 concentration of the principal phase crystal grain. Further, the grain boundary phase has an average thickness of 20 to 60 nm. The coercive force and residual magnetic flux density of the rare earth sintered neodymium-iron-boron magnet are balanced well.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention provides a rare earth sintered neodymium-iron-boron magnet, a method for manufacturing the same, and the use of praseodymium hydride.

Background Art

[0002] As the demand for hybrid vehicles, electric vehicles, and energy-saving air conditioner compressors increases, the demand for permanent magnet materials with high coercivity and low temperature coefficients is increasing. The use of a large amount of heavy rare earth elements can improve the coercivity and temperature coefficient of permanent magnet materials. However, this results in a significant increase in cost and a partial sacrifice of the residual magnetic flux density and magnetic energy product. An alloy sheet with an atomic composition of Nd14.1Co1.34Cu0.04FebalB5.84 for each element is manufactured, and the alloy sheet is hydrogen pulverized into coarse powder with a particle size of 10 to 100 μm. After that, the coarse powder is made into fine powder with an average particle size of 3.38 μm by jet milling in a nitrogen atmosphere, and DyHx powder with an average particle size of 1.8 μm is mixed with the fine powder. It is hydrostatically isotropically pressed at a magnetic field of 1800 kA / m and 300 MPa, and the green body is sintered at 1040 to 1060 °C for 2 h under vacuum conditions, then gas-cooled and quenched, and then annealed at 900 °C and 500 °C for 2 h respectively. In this method, it is necessary to use heavy rare earth Dy, and DyHx powder is directly mixed with the fine powder. In this method, the coercivity of the magnet can be significantly improved, but the residual magnetic flux density decreases too much, and the balance between coercivity and residual magnetic flux density cannot be achieved.

[0003] Adding Co and Ni elements can improve the temperature coefficient of the magnet. However, excessive addition of Co and Ni elements will lead to a decrease in magnet performance, and Co and Ni elements are strategic elements with relatively high prices. CN111696742A discloses a method for manufacturing a high-performance neodymium-iron-boron permanent magnet material without heavy rare earths. An anisotropic magnet material (Nd, Pr)xFe(100-x-y-z)ByMz and an auxiliary phase material PraNi100-b are prepared. After uniformly mixing the anisotropic magnet material and the auxiliary phase material to form mixed magnetic powder, orientation press molding, sintering, and annealing treatments are sequentially performed to obtain a high-performance neodymium-iron-boron material without heavy rare earths. CN104575899A discloses a method for manufacturing a sintered neodymium-iron-boron magnet in which the average thickness of the grain boundary phase of the obtained magnet is increased by directly mixing the main alloy powder and the rare earth cobalt compound powder and then molding. These methods can improve the coercivity of the magnet, but cannot suppress the decrease in the residual magnetic flux density and cannot achieve a good balance between the coercivity and the residual magnetic flux density.

Summary of the Invention

[0004] In one aspect, the present invention provides an (R1, R2)-T-B-M rare earth sintered neodymium-iron-boron magnet that can achieve a good balance between the coercivity and the residual magnetism of the rare earth sintered neodymium-iron-boron magnet. Further, the rare earth sintered neodymium-iron-boron magnet according to the present invention has a low temperature coefficient of residual magnetic flux density and a low temperature coefficient of coercivity.

[0005] In another aspect, the present invention provides a method for manufacturing an (R1, R2)-T-B-M rare earth sintered neodymium-iron-boron magnet. Different from the conventional methods, this manufacturing method can achieve a good balance between the coercivity and the residual magnetic flux density of the rare earth sintered neodymium-iron-boron magnet in order to suppress the decrease in the residual magnetic flux density.

[0006] In another aspect, the present invention provides the use of praseodymium hydride.

[0007] In one aspect, the present invention provides a (R1,R2)-T-B-M rare earth sintered neodymium-iron-boron magnet, wherein the rare earth sintered neodymium-iron-boron magnet is composed of a sintered body containing main phase crystal grains and a grain boundary phase, the main phase crystal grains are composed of a (R1,R2)2T14B phase, and the Pr concentration C1 at the edge of the main phase crystal grains is higher than the Pr concentration C2 at the center of the main phase crystal grains, the R1 concentration in the grain boundary phase is higher than the R1 concentration in the main phase crystal grains, and the average thickness of the grain boundary phase is 20 to 60 nm, R1 is one or more selected from Nd and Gd elements, and Nd is 50 at% or more of the total atomic number of R1, R2 is a Pr element, T is one or more selected from Fe, Co and Ni elements, and Co and Ni are 3 at% or less of the total atomic number of T, B is a boron element, M is one or more selected from Al, Cu, Ga, Zn, Bi, Zr, Ti, Nb, V, Mo and W elements, and the total atomic number of M is 5 at% or less of the sintered body, to provide a (R1,R2)-T-B-M rare earth sintered neodymium-iron-boron magnet.

[0008] According to the rare earth sintered neodymium-iron-boron magnet of the present invention, preferably, the Pr concentration gradually decreases from the edge of the main phase crystal grains toward the center of the main phase crystal grains.

[0009] According to the rare earth sintered neodymium-iron-boron magnet of the present invention, preferably, the Pr concentration C1 at the edge of the main phase crystal grains is 0.25 wt% or more higher than the Pr concentration C2 at the center of the main phase crystal grains.

[0010] According to the rare earth sintered neodymium-iron-boron magnet of the present invention, preferably, as the composition of the sintered body, R1: 28 to 31 wt%, R2: 0.1 to 5 wt%, B: 0.6 to 1.6 wt%, Co: 0.1 to 3.9 wt%, Cu: 0.05 to 1.0 wt%, Zr: 0.06 to 0.25 wt%, Ga: 0.1 to 0.3 wt%, and the balance is substantially Fe.

[0011] According to the rare earth sintered neodymium-iron-boron magnet of the present invention, preferably, the content of Zr in the sintered body is 0.1 to 0.16 wt%, and the content of Ga is 0.15 to 0.25 wt%.

[0012] According to the rare earth sintered neodymium-iron-boron magnet of the present invention, preferably, it does not contain heavy rare earth elements.

[0013] According to the rare earth sintered neodymium-iron-boron magnet of the present invention, preferably, the residual magnetic flux density of the rare earth sintered neodymium-iron-boron magnet is 14.50 kGs or more, the intrinsic coercive force is 14.0 kOe or more, the residual magnetic flux density temperature coefficient in the range of 20 to 150 °C is less than 0.113% / °C, and the coercive force temperature coefficient in the range of 20 to 150 °C is less than 0.573% / °C.

[0014] In another aspect, the present invention (a) A step of melting R1, T, B, and M, which are raw materials of a rare earth sintered neodymium-iron-boron magnet, to obtain a master alloy sheet. (b) A step of crushing the master alloy sheet into alloy coarse powder with an average particle size D50 of 20 to 500 μm. (c) A step of crushing the alloy coarse powder into magnetic powder with an average particle size D50 of 1 to 10 μm by jet milling with praseodymium-containing powder, wherein the praseodymium-containing powder is hydrogenated praseodymium or Pr-M alloy powder. (d) A step of pressing the magnetic powder in a magnetic field and obtaining a green body through isostatic hydrostatic pressing treatment. (e) A step of obtaining a rare earth sintered permanent magnet by subjecting the green body to vacuum heat treatment and two-stage annealing. Provided is a method for manufacturing the rare earth sintered neodymium-iron-boron magnet including

[0015] According to the manufacturing method of the present invention, preferably, based on the mass of the alloy coarse powder, the usage amount of the praseodymium-containing powder is 0.1 to 5.0 wt%.

[0016] In another aspect, the present invention relates to the use of hydrogenated praseodymium for improving the balance coefficient between the residual magnetic flux density and the coercive force of the rare earth sintered neodymium-iron-boron magnet, wherein the alloy coarse powder is pulverized into magnetic powder by jet milling with hydrogenated praseodymium powder, and based on the mass of the alloy coarse powder, the usage amount of the hydrogenated praseodymium powder is 0.1 to 5.0 wt%, the composition of the alloy coarse powder is R1-T-B-M, R1 is one or more selected from the Nd and Gd elements, and Nd is 50 at% or more of the total number of atoms of R1, T is one or more selected from the Fe, Co, and Ni elements, and Co and Ni are 3 at% or less of the total number of atoms of T, B is a boron element, M is one or more selected from the Al, Cu, Ga, Zn, Bi, Zr, Ti, Nb, V, Mo, and W elements, and the total number of atoms of M is 5 at% or less of the sintered body, The calculation formula for the balance coefficient E between the residual magnetic flux density and the coercive force is as follows: E = X2 / X1 X1 = (Br1 - Br2) / Br1 X2 = (Hcj2 - Hcj1) / Hcj1 (Br1 represents the residual magnetic flux density of the rare earth sintered neodymium-iron-boron magnet obtained without adding hydrogenated praseodymium powder in the jet milling process, and the unit is kGs, Br2 represents the residual magnetic flux density of the rare earth sintered neodymium-iron-boron magnet obtained by adding hydrogenated praseodymium powder in the jet milling process, and the unit is kGs, Hcj1 represents the coercivity of a rare earth sintered neodymium-iron-boron magnet obtained without adding hydrogenated praseodymium powder in a jet milling process, with the unit of kOe. Hcj2 represents the coercivity of a rare earth sintered neodymium-iron-boron magnet obtained by adding hydrogenated praseodymium powder in a jet milling process, with the unit of kOe.) Provided is the use of hydrogenated praseodymium to improve the balance coefficient between the residual magnetic flux density and the coercivity of a rare earth sintered neodymium-iron-boron magnet.

[0017] The rare earth sintered neodymium-iron-boron magnet according to the present invention has a relatively high coercivity and residual magnetic flux density, and can achieve a good balance between the two. Furthermore, the rare earth sintered neodymium-iron-boron magnet according to the present invention has a relatively low temperature coefficient of residual magnetic flux density and a temperature coefficient of coercivity.

Brief Description of the Drawings

[0018]

Figure 1

Modes for Carrying Out the Invention

[0019] Hereinafter, the present invention will be described in more detail, but the present invention is not limited thereto.

[0020] In the present invention, the residual magnetic flux density means the numerical value of the magnetic flux density corresponding to the zero magnetic field strength in the saturation magnetic hysteresis curve, and is usually denoted as Br or Mr, with the unit of tesla (T) or gauss (Gs). 1 Gs = 0.0001 T.

[0021] In the present invention, the coercive force, also called the intrinsic coercive force, refers to the magnetic field strength when the magnetic field is monotonically decreased from the saturation magnetization state of the magnet to zero, then increased in the reverse direction, and the magnetization intensity is decreased to zero along the saturation magnetic hysteresis curve. It is usually denoted as Hcj, and the unit is oersted (Oe) or ampere per meter (A / m). 1 Oe = 79.6 A / m. Hcj is the intrinsic coercive force at room temperature.

[0022] In the present invention, the inert gas includes helium gas, neon gas, argon gas, krypton gas, xenon gas, etc. Vacuum means the absolute vacuum degree, and the smaller the numerical value, the higher the vacuum degree.

[0023] In the present invention, the average particle size D50 refers to the equivalent diameter of the largest particle when the cumulative distribution in the particle size distribution curve is 50%.

[0024] In the present invention, "at%" refers to the atomic percentage.

[0025] The present invention aims to achieve a good balance between the residual magnetic flux density and the coercive force of the magnet. The calculation formula for the balance coefficient E between the residual magnetic flux density and the coercive force is as follows.

[0026] E = X2 / X1 X1 = (Br1 - Br2) / Br1 X2 = (Hcj2 - Hcj1) / Hcj1 Br1 represents the residual magnetic flux density of the rare earth sintered neodymium-iron-boron magnet obtained without adding the modified powder, and the unit is kGs. In some embodiments, Br1 represents the residual magnetic flux density of the rare earth sintered neodymium-iron-boron magnet obtained without adding the hydrogenated praseodymium powder in the jet milling process, and the unit is kGs.

[0027] Br2 represents the remanent magnetic flux density of the rare earth sintered neodymium-iron-boron magnet obtained by adding the modified powder, and the unit is kGs. In some embodiments, Br2 represents the remanent magnetic flux density of the rare earth sintered neodymium-iron-boron magnet obtained by adding hydrogenated praseodymium powder to the jet milling process, and the unit is kGs.

[0028] Hcj1 represents the coercivity of the rare earth sintered neodymium-iron-boron magnet obtained without adding the modified powder, and the unit is kOe. In some embodiments, Hcj1 represents the coercivity of the rare earth sintered neodymium-iron-boron magnet obtained without adding hydrogenated praseodymium powder to the jet milling process, and the unit is kOe.

[0029] Hcj2 represents the coercivity of the rare earth sintered neodymium-iron-boron magnet obtained by adding the modified powder, and the unit is kOe. In some embodiments, Hcj2 represents the coercivity of the rare earth sintered neodymium-iron-boron magnet obtained by adding hydrogenated praseodymium powder to the jet milling process, and the unit is kOe.

[0030] In the present invention, by adding praseodymium-containing powder to the jet milling process of pulverizing alloy coarse powder into fine magnetic powder, the thickness of the grain boundary phase of the obtained magnet is maintained within a certain range, and since praseodymium shows a gradient distribution in the main phase particles, it has been found that a good balance between the remanent magnetic flux density and the coercivity of the magnet can be achieved. Based on this, the present invention is completed.

[0031] <Rare earth sintered neodymium-iron-boron magnet> The rare earth sintered neodymium-iron-boron magnet according to the present invention has an element composition represented by the following formula. (R1,R2)-T-B-M

[0032] The rare earth sintered neodymium-iron-boron magnet is composed of a sintered body containing main phase crystal grains and a grain boundary phase. In some embodiments, the rare earth sintered neodymium-iron-boron magnet has the same meaning as the sintered body.

[0033] R1 is one or more selected from Nd and Gd elements. Nd is 50 at% or more of the total number of R1 atoms, preferably Nd is 80 at% or more of the total number of R1 atoms, more preferably Nd is 95 at% or more of the total number of R1 atoms. According to one embodiment of the present invention, R1 is Nd.

[0034] R2 is Pr element.

[0035] T is one or more selected from Fe, Co and Ni elements. Co and Ni are 3 at% or less of the total number of T atoms, preferably Co and Ni are 2 at% or less of the total number of T atoms, more preferably Co and Ni are 1 to 1.5 at% of the total number of T atoms. According to one embodiment of the present invention, T is Fe and Co.

[0036] B is boron element.

[0037] M is one or more selected from Al, Cu, Ga, Zn, Bi, Zr, Ti, Nb, V, Mo and W elements. Preferably M is Cu, Zr and Ga. The total number of M atoms is 5 at% or less of the sintered body, preferably 4 at% or less, more preferably 3 at% or less, and most preferably 0.1 to 2 at%. According to one embodiment of the present invention, the total number of M atoms is 0.3 to 1 at% of the sintered body.

[0038] The rare earth sintered neodymium-iron-boron magnet according to the present invention has main phase crystal grains composed of the (R1, R2)2T14B phase. The inventors have found that the Pr concentration C1 at the edge of the main phase crystal grains is higher than the Pr concentration C2 at the center of the main phase crystal grains. The Pr concentration C1 at the edge of the main phase crystal grains is 0.25 wt% or more higher than the Pr concentration C2 at the center of the main phase crystal grains. Preferably, the Pr concentration C1 at the edge of the main phase crystal grains is 0.40 wt% or more higher than the Pr concentration C2 at the center of the main phase crystal grains, and more preferably, the Pr concentration C1 at the edge of the main phase crystal grains is 0.50 wt% or more higher than the Pr concentration C2 at the center of the main phase crystal grains. In some embodiments, the concentration difference (C1 - C2) between the Pr concentration C1 at the edge of the main phase crystal grains and the Pr concentration C2 at the center of the main phase crystal grains is in the range of 0.25 to 0.70 wt%, preferably in the range of 0.40 to 0.70 wt%, and more preferably in the range of 0.45 to 0.65 wt%. According to one embodiment of the present invention, the concentration difference (C1 - C2) between the Pr concentration C1 at the edge of the main phase crystal grains and the Pr concentration C2 at the center of the main phase crystal grains is 0.53 to 0.57 wt%. If the Pr concentration difference is too small, it is disadvantageous for improving the coercive force. If the Pr concentration difference is too large, it has an adverse effect on the residual magnetic flux density, the temperature coefficient of the residual magnetic flux density, and the temperature coefficient of the coercive force. The Pr concentration difference within the above range is advantageous for achieving a good balance between the coercive force and the residual magnetic flux density of the magnet.

[0039] According to one embodiment of the present invention, the Pr concentration gradually decreases along the direction from the edge of the main phase crystal grains to the center of the main phase crystal grains. Therefore, the Pr concentration shows a gradient distribution. Thereby, a better balance between the coercive force and the residual magnetic flux density of the magnet can be further ensured.

[0040] The R1 concentration A1 of the grain boundary phase is higher than the R1 concentration A2 of the main phase crystal grains. The average thickness L of the grain boundary phase is 20 - 60 nm, preferably 20 - 40 nm, and more preferably 22 - 27 nm. If the thickness of the grain boundary phase is too small, the coercivity of the magnet cannot be significantly improved. If the thickness of the grain boundary phase is too large, the residual magnetic flux density will decrease significantly, and the temperature coefficients of the residual magnetic flux density and the coercivity will increase significantly. The grain boundary phase thickness within the above range is advantageous for achieving a good balance between the coercivity and the residual magnetic flux density of the magnet.

[0041] The sintered body according to the present invention contains elements such as R1, R2, B, Co, Cu, Zr, Ga, and Fe. In some embodiments, the sintered body according to the present invention consists of R1, R2, B, Co, Cu, Zr, Ga, and Fe.

[0042] Based on the mass of the sintered body, the content of R1 may be 28 - 31 wt%, preferably 28 - 30 wt%, and more preferably 28 - 29 wt%.

[0043] Based on the mass of the sintered body, the content of R2 may be 0.1 - 5 wt%, preferably 1.0 - 3 wt%, more preferably 1.5 - 2.5 wt%, and most preferably 1.7 - 2.0 wt%.

[0044] Based on the mass of the sintered body, the content of B may be 0.6 - 1.6 wt%, preferably 0.7 - 1.3 wt%, and more preferably 0.9 - 1.0 wt%.

[0045] Based on the mass of the sintered body, the content of Co may be 0.1 - 3.9 wt%, preferably 0.7 - 1.3 wt%, and more preferably 0.9 - 1.0 wt%.

[0046] Based on the mass of the sintered body, the content of Cu may be 0.05 - 1.0 wt%, preferably 0.10 - 0.70 wt%, and more preferably 0.12 - 0.20 wt%.

[0047] Based on the mass of the sintered body, the content of Zr may be 0.06 to 0.25 wt%, preferably 0.1 to 0.16 wt%, and more preferably 0.13 to 0.15 wt%.

[0048] Based on the mass of the sintered body, the content of Ga may be 0.1 to 0.3 wt%, preferably 0.15 to 0.25 wt%, and more preferably 0.18 to 0.20 wt%.

[0049] The balance is Fe.

[0050] By controlling each element within the above ranges, it is advantageous to obtain a rare earth sintered neodymium-iron-boron magnet in which the coercive force and the residual magnetic flux density achieve a good balance.

[0051] According to one embodiment of the present invention, the rare earth sintered neodymium-iron-boron magnet according to the present invention does not contain heavy rare earth elements. The heavy rare earth elements are terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Thereby, the cost can be reduced, and a better balance between the coercive force and the residual magnetic flux density can be ensured.

[0052] The rare earth sintered neodymium-iron-boron magnet according to the present invention has a residual magnetic flux density of 14.50 kGs or more, preferably 14.60 kGs or more, more preferably 14.65 kGs or more. The residual magnetic flux density may be less than 16.1 kGs, preferably less than 15.8 kGs, more preferably 15.5 kGs. The intrinsic coercive force is 14.0 kOe or more, preferably 16.3 kOe or more, more preferably 16.5 kOe or more. The intrinsic coercive force may be less than 29 kOe, preferably less than 25 kOe, more preferably less than 19 kOe. The temperature coefficient of the residual magnetic flux density within the temperature range of 20 to 150 °C is less than 0.113% / °C, preferably less than 0.110% / °C, more preferably less than 0.109% / °C. The temperature coefficient of the residual magnetic flux density may exceed 0, preferably exceed 0.05% / °C, more preferably exceed 0.08% / °C. The temperature coefficient of the coercive force within the range of 20 to 150 °C is less than 0.573% / °C, preferably less than 0.570% / °C, more preferably less than 0.565% / °C. The temperature coefficient of the coercive force exceeds 0, preferably exceeds 0.1% / °C, more preferably exceeds 0.3% / °C.

[0053] The balance coefficient E between the residual magnetic flux density and the coercive force of the rare earth sintered neodymium-iron-boron magnet according to the present invention may be 25 or more, preferably 35 or more, more preferably 39 or more. The balance coefficient E may be 150 or less, preferably 100 or less, more preferably 80 or less. The definition of the balance coefficient E is as described above.

[0054] <Manufacturing method of rare earth sintered neodymium-iron-boron magnet> The manufacturing method of the rare earth sintered neodymium-iron-boron magnet according to the present invention includes (a) a melting step, (b) a crushing step, (c) a jet milling step, (d) a forming step, and (e) a sintering and aging treatment step. These will be described in detail below.

[0055] Melting step The raw materials of the rare earth sintered neodymium-iron-boron magnet containing R1, T, B and M are melted to obtain a master alloy sheet. Preferably, the raw materials of the rare earth sintered neodymium-iron-boron magnet consist of R1, T, B and M. R1 is one or more selected from the Nd and Gd elements. Nd is 50 at% or more of the total number of atoms of R1, preferably Nd is 80 at% or more of the total number of atoms of R1, more preferably Nd is 95 at% or more of the total number of atoms of R1. According to one embodiment of the present invention, R1 is Nd. T is one or more selected from the Fe, Co and Ni elements. Co and Ni are 3 at% or less of the total number of atoms of T, preferably Co and Ni are 2 at% or less of the total number of atoms of T, more preferably Co and Ni are 1 to 1.5 at% of the total number of atoms of T. According to one embodiment of the present invention, T is Fe and Co. B is a boron element. M is one or more selected from the Al, Cu, Ga, Zn, Bi, Zr, Ti, Nb, V, Mo and W elements. Preferably, M is Cu, Zr and Ga. The total number of atoms of M is 5 at% or less of the raw materials, preferably 4 at% or less, more preferably 3 at% or less, most preferably 0.1 to 2 at%. According to one embodiment of the present invention, the total number of atoms of M is 0.3 to 1 at% of the raw materials.

[0056] The raw materials of the rare earth sintered neodymium-iron-boron magnet according to the present invention contain elements such as R1, B, Co, Cu, Zr, Ga, and Fe. In some embodiments, the raw materials of the rare earth sintered neodymium-iron-boron magnet according to the present invention consist of R1, B, Co, Cu, Zr, Ga, and Fe. Based on the mass of the raw materials of the rare earth sintered neodymium-iron-boron magnet, the content of R1 may be 28-31 wt%, preferably 28-30 wt%, and more preferably 28-29 wt%. The content of B may be 0.6-1.6 wt%, preferably 0.7-1.3 wt%, and more preferably 0.9-1.0 wt%. The content of Co may be 0.1-3.9 wt%, preferably 0.7-1.3 wt%, and more preferably 0.9-1.0 wt%. The content of Cu may be 0.05-1.0 wt%, preferably 0.10-0.70 wt%, and more preferably 0.12-0.20 wt%. The content of Zr may be 0.06-0.25 wt%, preferably 0.1-0.16 wt%, and more preferably 0.13-0.15 wt%. The content of Ga may be 0.1-0.3 wt%, preferably 0.15-0.25 wt%, and more preferably 0.18-0.20 wt%. The balance is Fe. According to one embodiment of the present invention, the raw materials of the rare earth sintered neodymium-iron-boron magnet according to the present invention may not contain heavy rare earth elements. The heavy rare earth elements are terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0057] The raw materials are blended according to the composition of the rare-earth sintered neodymium-iron-boron magnet. In some embodiments, the raw materials consist of Nd, B, Co, Cu, Zr, Ga, and Fe. The content of Nd may be 28-31 wt%, preferably 28-30 wt%, more preferably 28-29 wt%. The content of B may be 0.6-1.6 wt%, preferably 0.7-1.3 wt%, more preferably 0.9-1.0 wt%. The content of Co may be 0.1-3.9 wt%, preferably 0.7-1.3 wt%, more preferably 0.9-1.0 wt%. The content of Cu may be 0.05-1.0 wt%, preferably 0.10-0.70 wt%, more preferably 0.12-0.20 wt%. The content of Zr may be 0.06-0.25 wt%, preferably 0.1-0.16 wt%, more preferably 0.13-0.15 wt%. The content of Ga may be 0.1-0.3 wt%, preferably 0.15-0.25 wt%, more preferably 0.18-0.20 wt%. The balance is Fe.

[0058] Melting may be performed in a vacuum melting furnace. The average thickness of the obtained master alloy sheet may be 0.05-1.00 mm, preferably 0.1-0.8 mm, more preferably 0.2-0.5 mm.

[0059] Crushing process The master alloy sheet is crushed into alloy coarse powder. The average particle size D50 of the alloy coarse powder is 20-500 μm, preferably 50-300 μm, more preferably 80-150 μm. The alloy coarse powder can be obtained by adopting a method such as hydrogen crushing. For example, the master alloy sheet may be subjected to a hydrogen absorption and dehydrogenation treatment in a hydrogen crushing furnace to form alloy coarse powder.

[0060] Jet milling process In the traditional jet milling process, alloy coarse powder is directly crushed into alloy fine powder. In the present invention, by adding praseodymium-containing powder to the jet milling process, it promotes coating at least a part of the alloy fine powder with the praseodymium-containing powder. The alloy coarse powder and the praseodymium-containing powder are crushed into magnetic powder by jet milling. The average particle size D50 of the magnetic powder is 1 to 10 μm, preferably 2 to 7 μm, and more preferably 3 to 5 μm.

[0061] The praseodymium-containing powder according to the present invention may be hydrogenated praseodymium or Pr-M alloy powder. In the Pr-M alloy powder, M is one or more selected from the elements of Al, Cu, Ga, Zn, Bi, Zr, Ti, Nb, V, Mo and W. Preferably, M is Cu, Zr and Ga. The Pr-M alloy powder is not a Pr-Ni alloy powder or a Pr-Co alloy powder. These two types of alloy powders are expensive, and on the other hand, they are not very effective in improving the balance between the residual magnetic flux density and the coercive force of the magnet, and are even inferior to the Pr-M alloy powder of the present invention.

[0062] According to one embodiment of the present invention, the praseodymium-containing powder is hydrogenated praseodymium powder. Such powder is not only inexpensive and easily available, but also has a very remarkable effect of improving the balance between the residual magnetic flux density and the coercive force of the magnet. Such a technical effect cannot be predicted.

[0063] According to another embodiment of the present invention, the Pr-M alloy powder is a Pr-Cu alloy powder. Pr in the Pr-Cu alloy powder is 50 at% or more, preferably 60 at% or more, and more preferably 65 to 75 at%.

[0064] Based on the mass of the alloy coarse powder, the usage amount of the praseodymium-containing powder is 0.1 to 5.0 wt%, preferably 1.0 to 4.0 wt%, and more preferably 1.5 to 2.5 wt%.

[0065] The jet milling process may be carried out in a nitrogen atmosphere.

[0066] Forming process Place the magnetic powder in a magnetic field and press it, and then obtain a green body through isostatic pressing treatment such as hydrostatic pressure.

[0067] The forming process may be press-formed with a forming press. Preferably, it is carried out under nitrogen protection.

[0068] The magnetic field strength exceeds 1.0 T, preferably exceeds 1.5 T, and more preferably exceeds 1.7 T.

[0069] The density of the green body may be 2.5 - 5.5 g / cm3, preferably 3.5 - 5.0 g / cm3, and more preferably 4.0 - 4.5 g / cm3.

[0070] Sintering and aging treatment process Obtain a rare earth sintered permanent magnet by subjecting the green body to vacuum heat treatment and two-stage annealing treatment.

[0071] The vacuum condition of the vacuum heat treatment means that the absolute vacuum degree is less than 0.5 Pa, preferably less than 0.3 Pa, and more preferably less than 0.1 Pa. The heat treatment temperature may be 850 - 1300 °C, preferably 950 - 1200 °C, and more preferably 1000 - 1100 °C. The heat treatment time may be 2 - 10 h, preferably 3 - 8 h, and more preferably 4 - 7 h.

[0072] The primary annealing temperature may be 600 - 1050 °C, preferably 700 - 1000 °C, and more preferably 800 - 950 °C. The primary annealing time may be 1 - 6 h, preferably 2 - 5 h, and more preferably 3 - 4 h. The primary annealing is carried out under vacuum conditions. The vacuum condition means that the absolute vacuum degree is less than 0.5 Pa, preferably less than 0.3 Pa, and more preferably less than 0.1 Pa.

[0073] The secondary tempering temperature may be 300 to 700 °C, preferably 400 to 600 °C, more preferably 450 to 550 °C. The secondary tempering time may be 3 to 10 h, preferably 4 to 8 h, more preferably 5 to 7 h. The secondary tempering is carried out under vacuum conditions. The vacuum conditions mean that the absolute vacuum degree is less than 0.5 Pa, preferably less than 0.3 Pa, more preferably less than 0.1 Pa.

[0074] <Use of hydrogenated praseodymium> The present invention provides the use of hydrogenated praseodymium for improving the balance coefficient between the residual magnetic flux density and the coercive force of a rare earth sintered neodymium-iron-boron magnet. The balance coefficient between the residual magnetic flux density and the coercive force can be represented as E and is calculated by the following formula.

[0075] E = X2 / X1 X1 = (Br1 - Br2) / Br1 X2 = (Hcj2 - Hcj1) / Hcj1 Br1 represents the residual magnetic flux density of a rare earth sintered neodymium-iron-boron magnet obtained without adding hydrogenated praseodymium powder in the jet milling process, and the unit is kGs. Br2 represents the residual magnetic flux density of a rare earth sintered neodymium-iron-boron magnet obtained by adding hydrogenated praseodymium powder in the jet milling process, and the unit is kGs. Hcj1 represents the coercive force of a rare earth sintered neodymium-iron-boron magnet obtained without adding hydrogenated praseodymium powder in the jet milling process, and the unit is kOe. Hcj2 represents the coercive force of a rare earth sintered neodymium-iron-boron magnet obtained by adding hydrogenated praseodymium powder in the jet milling process, and the unit is kOe.

[0076] The balance coefficient E between the residual magnetic flux density and the coercive force of the rare earth sintered neodymium-iron-boron magnet according to the present invention may be 25 or more, preferably 35 or more, more preferably 39 or more. The balance coefficient E may be 150 or less, preferably 100 or less, more preferably 80 or less.

[0077] In the use according to the present invention, the alloy coarse powder and the hydrogenated praseodymium powder are pulverized into coarse powder by jet milling. Based on the mass of the alloy coarse powder, the usage amount of the hydrogenated praseodymium powder is 0.1 to 5.0 wt%, preferably 1.0 to 4.0 wt%, and more preferably 2.0 to 3.0 wt%. In addition to the jet milling process, the use according to the present invention may further include a melting process, a crushing process, a forming process, and a sintering / aging treatment process. The specific process conditions are as described above.

[0078] The composition of the alloy coarse powder according to the present invention has R1-T-B-M, and is preferably R1-T-B-M.

[0079] R1 is one or more selected from the elements Nd and Gd. Nd is 50 at% or more of the total number of atoms of R1, preferably Nd is 80 at% or more of the total number of atoms of R1, and more preferably Nd is 95 at% or more of the total number of atoms of R1. According to one embodiment of the present invention, R1 is Nd.

[0080] T is one or more selected from the elements Fe, Co, and Ni. Co and Ni are 3 at% or less of the total number of atoms of T, preferably Co and Ni are 2 at% or less of the total number of atoms of T, and more preferably Co and Ni are 1 to 1.5 at% of the total number of atoms of T. According to one embodiment of the present invention, T is Fe and Co.

[0081] B is the boron element.

[0082] M is one or more selected from the elements Al, Cu, Ga, Zn, Bi, Zr, Ti, Nb, V, Mo, and W. Preferably, M is Cu, Zr, and Ga. The total number of atoms of M is 5 at% or less of the alloy coarse powder, preferably 4 at% or less, more preferably 3 at% or less, and most preferably 0.1 to 2 at%. According to one embodiment of the present invention, the total number of atoms of M is 0.3 to 1 at% of the alloy coarse powder.

[0083] The alloy coarse powder according to the present invention contains elements such as R1, B, Co, Cu, Zr, Ga, and Fe. In some embodiments, the alloy coarse powder according to the present invention consists of R1, B, Co, Cu, Zr, Ga, and Fe. Based on the mass of the alloy coarse powder, the content of R1 may be 28-31 wt%, preferably 28-30 wt%, more preferably 28-29 wt%. The content of B may be 0.6-1.6 wt%, preferably 0.7-1.3 wt%, more preferably 0.9-1.0 wt%. The content of Co may be 0.1-3.9 wt%, preferably 0.7-1.3 wt%, more preferably 0.9-1.0 wt%. The content of Cu may be 0.05-1.0 wt%, preferably 0.10-0.70 wt%, more preferably 0.12-0.20 wt%. The content of Zr may be 0.06-0.25 wt%, preferably 0.1-0.16 wt%, more preferably 0.13-0.15 wt%. The content of Ga may be 0.1-0.3 wt%, preferably 0.15-0.25 wt%, more preferably 0.18-0.20 wt%. The balance is Fe. According to one embodiment of the present invention, the alloy coarse powder according to the present invention does not contain heavy rare earth elements. The heavy rare earth elements are terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0084] According to one embodiment of the present invention, the alloy coarse powder may consist of Nd, B, Co, Cu, Zr, Ga and Fe. The content of Nd may be 28-31 wt%, preferably 28-30 wt%, more preferably 28-29 wt%. The content of B may be 0.6-1.6 wt%, preferably 0.7-1.3 wt%, more preferably 0.9-1.0 wt%. The content of Co may be 0.1-3.9 wt%, preferably 0.7-1.3 wt%, more preferably 0.9-1.0 wt%. The content of Cu may be 0.05-1.0 wt%, preferably 0.10-0.70 wt%, more preferably 0.12-0.20 wt%. The content of Zr may be 0.06-0.25 wt%, preferably 0.1-0.16 wt%, more preferably 0.13-0.15 wt%. The content of Ga may be 0.1-0.3 wt%, preferably 0.15-0.25 wt%, more preferably 0.18-0.20 wt%. The balance is Fe.

[0085] In the jet milling process, raw materials including alloy coarse powder and hydrogenated praseodymium powder are pulverized into magnetic powder by jet milling. The average particle size D50 of the magnetic powder may be 1-10 μm, preferably 2-7 μm, more preferably 3-5 μm. The jet milling process may be carried out in a nitrogen atmosphere.

[0086] Example 1 Melting process: The raw materials were formulated with 29.0% Nd, 1.0% B, 1.0% Co, 0.15% Cu, 0.15% Zr, 0.2% Ga and the balance of Fe by mass percentage, and the raw materials were melted in a vacuum melting and rapid solidification furnace to produce an alloy sheet with an average thickness of 0.3 mm.

[0087] Hydrogen crushing process: The alloy sheet was subjected to hydrogen storage and dehydrogenation treatment in a hydrogen crushing furnace to obtain alloy coarse powder with an average particle size D50 of 100 μm.

[0088] Jet milling process: Based on alloy coarse powder, 2.0 wt% of hydrogenated praseodymium powder was added and uniformly mixed. Then, it was pulverized into magnetic powder with an average particle size D50 of 4.0 μm by jet milling using nitrogen gas as the medium.

[0089] Forming process: The magnetic powder was applied to a nitrogen-protected forming press, and a 1.8 T magnetic field was applied for orientation to form a green body. The density of the green body was 4.3 g / cm3.

[0090] Sintering and aging treatment process: The green body was placed in a vacuum sintering furnace with an absolute vacuum degree of less than 0.1 Pa and sintered at 1070 °C for 5 h to obtain a sintered magnet. Then, the sintered magnet was subjected to a one-step annealing at 900 °C for 3 h and a two-step annealing at 500 °C for 5 h under the condition of an absolute vacuum degree of less than 0.1 Pa to obtain a rare-earth sintered neodymium-iron-boron magnet.

[0091] The rare-earth sintered neodymium-iron-boron magnet was processed into a sample column of D10×10 mm, and the magnetic properties of the magnet at room temperature and 150 °C were measured with a BH tester, and the residual magnetic flux density temperature coefficient α and coercive force temperature coefficient β in the range of 20~150 °C were calculated.

[0092] The microstructure of the rare-earth sintered neodymium-iron-boron magnet was observed with a sigma500 field emission scanning electron microscope (see Figure 1), and composition analysis was performed using an EDS detector.

[0093] The average thickness L of the grain boundary phase, the Pr concentration difference (C1-C2) between the main phase grain edge and the main phase grain center, and the magnetic performance parameters of the rare-earth sintered neodymium-iron-boron magnet are shown in Table 1 and Table 2.

[0094] Examples 2~3 and Comparative Examples 1~2 In the jet milling process, the usage amount of hydrogenated praseodymium powder was changed, and the other processes were the same as those in Example 1. The average thickness L of the grain boundary phase, the Pr concentration difference (C1-C2) between the main phase grain edge and the main phase grain center, and the magnetic performance parameters of the rare-earth sintered neodymium-iron-boron magnet are shown in Table 1 and Table 2.

[0095] Example 4 In the jet milling process, 3.0%wt of Pr68Cu32 alloy was added, and the other processes were the same as in Example 1. The average thickness L of the grain boundary phase of the rare earth sintered neodymium-iron-boron magnet, the Pr concentration difference (C1-C2) between the edge of the main phase crystal grain and the center of the main phase crystal grain, and the magnetic performance parameters are shown in Table 1 and Table 2.

[0096] Comparative Example 3 In the melting process, the raw materials were formulated according to 29.0% Nd, 2.0% Pr, 1.0% B, 1.0% Co, 0.15% Cu, 0.15% Zr, 0.2% Ga, and the balance of Fe by mass percentage. In the jet milling process, no hydrogenated praseodymium powder was added, and the other processes were the same as in Example 1. The average thickness L of the grain boundary phase of the rare earth sintered neodymium-iron-boron magnet, the Pr concentration difference (C1-C2) between the edge of the main phase crystal grain and the center of the main phase crystal grain, and the magnetic performance parameters are shown in Table 1 and Table 2.

[0097] TIFF0007696481000001.tif72170

[0098] Comparative Examples 4 - 9 Sintered neodymium-iron-boron magnets were manufactured according to Examples 1 - 6 of CN111696742A. The average thickness L of the grain boundary phase of the rare earth sintered neodymium-iron-boron magnet, the Pr concentration difference (C1-C2) between the edge of the main phase crystal grain and the center of the main phase crystal grain, and the magnetic performance parameters are shown in Table 2.

[0099] Comparative Examples 10 - 13 Sintered neodymium-iron-boron magnets were manufactured according to Examples 1 - 4 of CN104575899A. The average thickness L of the grain boundary phase of the rare earth sintered neodymium-iron-boron magnet, the Pr concentration difference (C1-C2) between the edge of the main phase crystal grain and the center of the main phase crystal grain, and the magnetic performance parameters are shown in Table 2.

[0100] TIFF0007696481000002.tif224170TIFF0007696481000003.tif40170Note: Br1 represents the residual magnetic flux density of the rare earth sintered neodymium-iron-boron magnet obtained without adding the modified powder, with the unit of kGs; Br2 represents the residual magnetic flux density of the rare earth sintered neodymium-iron-boron magnet obtained by adding the modified powder, with the unit of kGs; Hcj1 represents the coercive force of the rare earth sintered neodymium-iron-boron magnet obtained without adding the modified powder, with the unit of kOe; Hcj2 represents the coercive force of the rare earth sintered neodymium-iron-boron magnet obtained by adding the modified powder, with the unit of kOe.

[0101] As can be seen from Tables 1 to 2, in the present invention, the alloy coarse powder is pulverized into magnetic powder by jet milling with praseodymium-containing powder, and then a rare earth sintered neodymium-iron-boron magnet is obtained through processes such as molding and sintering. Thereby, the residual magnetic flux density and the coercive force of the magnet can be made compatible, achieving a perfect balance between the two, and the balance coefficient is 25 or more. In this case, the Pr concentration C1 at the edge of the main phase crystal grains is 0.25 wt% or more higher than the Pr concentration C2 at the center of the main phase crystal grains, and the average thickness of the grain boundary phase is 20 to 60 nm. When using an appropriate amount of hydrogenated praseodymium powder, the balance coefficient between the residual magnetic flux density and the coercive force becomes as high as 35 or more (see Example 1).

[0102] As can be seen from Table 3, the magnets of Comparative Examples 1 to 13 cannot simultaneously satisfy the following conditions. (1) The Pr concentration C1 at the edge of the main phase crystal grains is 0.25 wt% or more higher than the Pr concentration C2 at the center of the main phase crystal grains. (2) The average thickness of the grain boundary phase is 20 to 60 nm.

[0103] As can be seen from Table 2, in Comparative Example 1, no praseodymium hydride powder was added, and the residual magnetic flux density and coercive force were relatively low. In Comparative Example 2, the amount of praseodymium hydride powder used was too large, and the residual magnetic flux density decreased too much, so the balance coefficient was relatively low. In Comparative Example 3, even when Pr was added in the raw material mixing step, the coercive force did not improve significantly, and the balance coefficient was relatively low. In Comparative Examples 4 to 9, PrNi alloy powder was directly mixed with fine magnetic powder, and the coercive force was significantly improved, but the residual magnetic flux density decreased too much, and the balance coefficient was less than 20. In Comparative Examples 11 and 12, (PrNd)Co alloy powder was directly mixed with fine magnetic powder, and the coercive force could be improved, but the residual magnetic flux density decreased too much, and the balance coefficient was 10 or less. In Comparative Examples 10 and 13, DyCo or TbCo alloy powder was directly mixed with fine magnetic powder, and the coercive force was significantly improved, but the residual magnetic flux density further decreased, and the balance coefficient became very low.

[0104] TIFF0007696481000004.tif116170

[0105] The present invention is not limited to the above embodiments, and all modifications, improvements, substitutions, etc. that can be conceived by those skilled in the art without departing from the spirit of the present invention are included in the scope of the present invention.

Claims

1. A method for producing a (R1, R2)-TBM rare earth sintered neodymium-iron-boron magnet, comprising the steps of: The rare earth sintered neodymium-iron-boron magnet is composed of a sintered body containing main phase crystal grains and a grain boundary phase, the main phase crystal grains are composed of an (R1, R2)2T14B phase, a Pr concentration C1 at an edge of the main phase crystal grains is higher than a Pr concentration C2 at a center of the main phase crystal grains, The R1 concentration of the grain boundary phase is higher than the R1 concentration of the main phase crystal grains, and the average thickness of the grain boundary phase is 20 to 40 nm; R1 is one or more elements selected from Nd and Gd, and Nd accounts for 50 at % or more of the total number of atoms of R1; R2 is a Pr element; T is one or more elements selected from Fe, Co, and Ni, and Co and Ni account for 3 at % or less of the total number of atoms of T; B is elemental boron; M is one or more elements selected from Al, Cu, Ga, Zn, Bi, Zr, Ti, Nb, V, Mo and W, and the total atomic number of M is 5 at % or less of the sintered body; The composition of the sintered body is R1: 28 to 31 wt%, R2: 0.1 to 5 wt%, B: 0.6 to 1.6 wt%, Co: 0.1 to 3.9 wt%, Cu: 0.05 to 1.0 wt%, Zr: 0.06 to 0.25 wt%, Ga: 0.1 to 0.3 wt%, and the balance is substantially Fe; The rare earth sintered neodymium-iron-boron magnet has a residual magnetic flux density of 14.50 kGs or more, an intrinsic coercivity of 14.0 kOe or more, a temperature coefficient of residual magnetic flux density within the range of 20 to 150°C of less than 0.113% / °C, and a temperature coefficient of coercivity within the range of 20 to 150°C of less than 0.573% / °C; The process is as follows: (a) melting R1, T, B and M, which are the raw materials for a rare earth sintered neodymium-iron-boron magnet, to obtain a master alloy sheet; (b) grinding the master alloy sheet into a coarse alloy powder having an average particle size D50 of 20-500 μm; (c) pulverizing the alloy coarse powder with a praseodymium-containing powder by jet milling to obtain a magnetic powder having an average particle size D50 of 1 to 10 μm, wherein the praseodymium-containing powder is a praseodymium hydride or Pr-M alloy powder; (d) pressing the magnetic powder in a magnetic field and then subjecting it to hydrostatic isostatic pressing to obtain a green body; and (e) subjecting the green body to a vacuum heat treatment and two-stage tempering to obtain a rare earth sintered permanent magnet; A method for producing an (R1, R2)-TBM rare earth sintered neodymium-iron-boron magnet, comprising:

2. 2. The method according to claim 1, wherein the amount of the praseodymium-containing powder used is 0.1 to 5.0 wt % based on the mass of the coarse alloy powder.

3. The balance factor between the residual magnetic flux density and the coercive force of the rare earth sintered neodymium-iron-boron magnet is 25 or more, The balance coefficient between the residual magnetic flux density and the coercive force is represented as E, and the calculation formula is as follows: It is E = X2 / X1 X1=(Br1-Br2) / Br1 X2=(Hcj2-Hcj1) / Hcj1 The Br1 was obtained without adding praseodymium hydride powder in the jet milling process. represents the residual magnetic flux density of a rare earth sintered neodymium-iron-boron magnet, and is expressed in kGs. The Br2 was obtained by adding praseodymium hydride powder in a jet milling process. It represents the residual magnetic flux density of a rare earth sintered neodymium-iron-boron magnet, and is expressed in kGs. The Hcj1 was obtained without adding praseodymium hydride powder in the jet milling process. represents the coercive force of the rare earth sintered neodymium-iron-boron magnet, and is expressed in kOe. The Hcj2 was obtained by adding praseodymium hydride powder in a jet milling process. It represents the coercive force of rare earth sintered neodymium-iron-boron magnets and is characterized by its unit of kOe. The method according to claim 1 or 2,

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