阅读说明：本技术 一种低熔点混合扩散提升钕铁硼磁体矫顽力的方法 (Method for improving coercive force of neodymium iron boron magnet through low-melting-point mixed diffusion ) 是由 泮敏翔 俞能君 杨杭福 吴琼 葛洪良 于 2021-09-18 设计创作，主要内容包括：本发明公开了一种低熔点混合扩散提升钕铁硼磁体矫顽力的方法,属于磁性材料技术领域。该制备方法包括：按照含重稀土低熔点(Dy,Tb)-Al-Cu合金和含高丰度稀土低熔点(Pr,Ce)-Ga-Cu合金成分分别称量各原料并进行电弧熔炼,随后分别通过高能球磨破碎和熔体快淬法及行星式低能球磨制粉,按比例混合制成糊状溶液；将糊状溶液均匀涂敷在钕铁硼磁体表面,随后进行N-(2)气保护和低磁场辅助下的一级和二级回火热处理,获得高矫顽力钕铁硼磁体。本发明工艺过程简单,易操作,有利于高性能钕铁硼磁体在更多永磁器件中的应用,以满足市场需求。(The invention discloses a method for improving the coercive force of a neodymium iron boron magnet by low-melting-point mixed diffusion, and belongs to the technical field of magnetic materials. The preparation method comprises the following steps: weighing raw materials according to the components of the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy and the high-abundance rare earth-containing low-melting-point (Pr, Ce) -Ga-Cu alloy, performing electric arc melting, then respectively performing high-energy ball milling crushing, melt rapid quenching and planetary low-energy ball milling to prepare powder, and mixing the powder according to a proportion to prepare a pasty solution; uniformly coating the pasty solution on the surface of the neodymium iron boron magnet, and then carrying out N 2 And performing primary and secondary tempering heat treatment under the assistance of gas protection and a low magnetic field to obtain the high-coercivity neodymium iron boron magnet. The invention has simple process and easy operation, and is beneficial to the application of the high-performance neodymium iron boron magnet in more permanent magnet devices so as to meet the market demand.)

1. A method for improving the coercive force of a neodymium iron boron magnet through low-melting-point mixed diffusion is characterized by comprising the following steps:

(1) respectively weighing raw materials according to the components of the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy and the high-abundance rare earth-containing low-melting-point (Pr, Ce) -Ga-Cu alloy, and carrying out arc melting to obtain a (Dy, Tb) -Al-Cu alloy and a (Pr, Ce) -Ga-Cu alloy; the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy is Dy in atomic percentage_aTb_75-aAl_bCu_25-bA and b satisfy the following relationship: a is more than or equal to 0 and less than or equal to 75, and b is more than or equal to 0 and less than or equal to 25; the low melting point (Pr, Ce) -Ga-Cu alloy containing high-abundance rare earth is Pr according to atomic percentage_aCe_75-aGa_bCu_25-bA and b satisfy the following relationship: a is more than or equal to 0 and less than or equal to 75, and b is more than or equal to 0 and less than or equal to 25;

(2) carrying out high-energy ball milling crushing on the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy obtained in the step (1), wherein the ball milling time is 4-10 h, and preparing (Dy, Tb) -Al-Cu alloy powder with the average particle size of 20-200 nm;

(3) preparing the high-abundance rare earth-containing low-melting-point (Pr, Ce) -Ga-Cu alloy obtained in the step (1) into an alloy thin strip by adopting a melt rapid quenching method, wherein the rotation speed of a copper roller is 20-40 m/s; then crushing the alloy ribbon into (Pr, Ce) -Ga-Cu alloy powder with the average particle size of 5-10 mu m by planetary low-energy ball milling, wherein the ball milling time is 1-3 h;

(4) mixing the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy powder obtained in the step (2) and the high-abundance rare earth-containing low-melting-point (Pr, Ce) -Ga-Cu alloy powder obtained in the step (3) according to a mass ratio, and then pouring the mixture into an absolute ethyl alcohol solution to prepare a pasty solution with the viscosity of 100-200 mmpa.s for later use;

(5) magnet surface treatment: degreasing and decontaminating the surface of a neodymium iron boron magnet with the cylinder size of 10 x 10 mm, degreasing for 10 s in 2% dilute nitric acid to remove an oxide film on the surface of the magnet, and finally ultrasonically cleaning the magnet in an absolute ethyl alcohol solution for 1-3 min;

(6) uniformly coating the pasty solution obtained in the step (4) on the surface of the neodymium iron boron magnet obtained in the step (5), wherein the coating thickness is 1-5 mm; followed by N₂And performing primary and secondary tempering heat treatment under the assistance of gas protection and a low magnetic field to obtain the high-coercivity neodymium iron boron magnet.

2. The method for improving the coercivity of the neodymium iron boron magnet through low-melting-point mixed diffusion according to claim 1, wherein the method comprises the following steps: the mass ratio of the (Dy, Tb) -Al-Cu alloy powder to the (Pr, Ce) -Ga-Cu alloy powder in the step (4) is 1-3: 1.

3. The method for improving the coercivity of the neodymium iron boron magnet through low-melting-point mixed diffusion according to claim 1, wherein the method comprises the following steps: the magnetic field intensity assisted by the low magnetic field in the step (6) is 0.3-1T; the temperature of the primary tempering heat treatment is 700-1000 ℃, the heat preservation time is 6-15 h, and then the primary tempering heat treatment is rapidly cooled to room temperature; the temperature of the secondary tempering heat treatment is 400-600 ℃, the heat preservation time is 4-8 hours, and then the secondary tempering heat treatment is rapidly cooled to the room temperature.

Technical Field

The invention relates to the technical field of magnetic materials, in particular to a method for improving the coercive force of a neodymium iron boron magnet through low-melting-point mixed diffusion.

Background

Rare earth is a non-renewable important strategic resource and is an indispensable key element for modifying the traditional industry, developing the emerging industry and the national defense science and technology industry. The yield of the rare earth magnetic materials and other functional materials in China accounts for about 80 percent of the total world production and is the first place of the whole world. The rare earth magnetic material is an indispensable important basic material in the high-tech fields of aerospace, high-grade numerical control machines and robots, advanced rail transit equipment, energy-saving and new energy automobiles, modern weaponry and the like.

The grain boundary diffusion technology is a new technology developed in recent years for improving the magnetic performance and reducing the weight of rare earth by sintering neodymium iron boron materials. Under the same coercive force, the content of heavy rare earth is only 20-30% of that of the traditional high coercive force sintered neodymium iron boron permanent magnet, and the remanence basically keeps unchanged. At present, the low-melting-point diffusion preparation of the high-coercivity neodymium iron boron magnet is mainly studied at home and abroad. And the research on low-melting point mixed diffusion, particularly on the composite diffusion of heavy rare earth low-melting point alloy and high-abundance low-melting point alloy is less. Therefore, the patent creatively uses the low melting point (Dy, Tb) -Al-Cu alloy containing heavy rare earth and the low melting point (Pr, Ce) -Ga-Cu alloy powder containing high-abundance rare earth as mixed diffusion sources to uniformly coat the mixed diffusion sources on the surface of the neodymium-iron-boron magnet, and then carries out N₂And performing primary and secondary tempering heat treatment under the assistance of gas protection and a low magnetic field to obtain the high-coercivity neodymium iron boron magnet.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a method for improving the coercive force of a neodymium iron boron magnet through low-melting-point mixed diffusion.

The method for improving the coercive force of the neodymium iron boron magnet by low-melting-point mixed diffusion comprises the following steps:

(1) respectively weighing raw materials according to the components of the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy and the high-abundance rare earth-containing low-melting-point (Pr, Ce) -Ga-Cu alloy, and carrying out arc melting to obtain a (Dy, Tb) -Al-Cu alloy and a (Pr, Ce) -Ga-Cu alloy; the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy is Dy in atomic percentage_aTb_75-aAl_bCu_25-bA and b satisfy the following relationship: a is more than or equal to 0 and less than or equal to 75, and b is more than or equal to 0 and less than or equal to 25; the low melting point (Pr, Ce) -Ga-Cu alloy containing high-abundance rare earth is Pr according to atomic percentage_aCe_75-aGa_bCu_25-bA and b satisfy the following relationship: a is more than or equal to 0 and less than or equal to 75, and b is more than or equal to 0 and less than or equal to 25;

(2) carrying out high-energy ball milling crushing on the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy obtained in the step (1), wherein the ball milling time is 4-10 h, and preparing (Dy, Tb) -Al-Cu alloy powder with the average particle size of 20-200 nm;

(3) preparing the high-abundance rare earth-containing low-melting-point (Pr, Ce) -Ga-Cu alloy obtained in the step (1) into an alloy thin strip by adopting a melt rapid quenching method, wherein the rotation speed of a copper roller is 20-40 m/s; then crushing the alloy ribbon into (Pr, Ce) -Ga-Cu alloy powder with the average particle size of 5-10 mu m by planetary low-energy ball milling, wherein the ball milling time is 1-3 h;

(4) mixing the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy powder obtained in the step (2) and the high-abundance rare earth-containing low-melting-point (Pr, Ce) -Ga-Cu alloy powder obtained in the step (3) according to a mass ratio, and then pouring the mixture into an absolute ethyl alcohol solution to prepare a pasty solution with the viscosity of 100-200 mmpa.s for later use;

(5) magnet surface treatment: degreasing and decontaminating the surface of a neodymium iron boron magnet with the cylinder size of 10 x 10 mm, degreasing for 10 s in 2% dilute nitric acid to remove an oxide film on the surface of the magnet, and finally ultrasonically cleaning the magnet in an absolute ethyl alcohol solution for 1-3 min;

(6) uniformly coating the pasty solution obtained in the step (4) on the surface of the neodymium iron boron magnet obtained in the step (5), wherein the coating thickness is 1-5 mm; followed by N₂And performing primary and secondary tempering heat treatment under the assistance of gas protection and a low magnetic field to obtain the high-coercivity neodymium iron boron magnet.

Further, the mass ratio of the (Dy, Tb) -Al-Cu alloy powder to the (Pr, Ce) -Ga-Cu alloy powder in the step (4) is 1-3: 1.

Further, the magnetic field intensity of the low magnetic field assistance in the step (6) is 0.3-1T; the temperature of the primary tempering heat treatment is 700-1000 ℃, the heat preservation time is 6-15 h, and then the primary tempering heat treatment is rapidly cooled to room temperature; the temperature of the secondary tempering heat treatment is 400-600 ℃, the heat preservation time is 4-8 hours, and then the secondary tempering heat treatment is rapidly cooled to the room temperature.

Compared with the prior art, the invention has the following advantages and beneficial effects: the invention creatively prepares two different low-melting-point alloy systems (heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy and high-abundance rare earth-containing low-melting-point (Pr, Ce) -Ga-Cu alloy) through different processes, simultaneously uses the two low-melting-point alloy systems as mixed diffusion sources, uniformly coats the mixed diffusion sources on the surface of the neodymium-iron-boron magnet, and then carries out N₂Gas-shielded and low-magnetic-field-assisted primary and secondary temperingAnd (4) performing heat treatment, wherein the diffusion depth of the low-melting-point alloy in the neodymium iron boron magnet is further effectively improved by the aid of a low magnetic field in the tempering heat treatment process, and finally the high-coercivity neodymium iron boron magnet is obtained. Meanwhile, the invention effectively improves the standard reaching rate of the magnetic performance of the high-performance sintered neodymium-iron-boron alloy and reduces the cost.

Detailed Description

The present invention will be described in further detail with reference to examples, but the present invention is not limited to only the following examples.

Example 1

(1) According to atom percentage, low melting point Dy containing heavy rare earth₇₀Tb₅Al₅Cu₂₀Alloy and low-melting-point Pr containing high-abundance rare earth₃₀Ce₄₅Ga₂₀Cu₅Respectively weighing each raw material for alloy components, and carrying out arc melting to obtain a (Dy, Tb) -Al-Cu alloy and a (Pr, Ce) -Ga-Cu alloy;

(2) carrying out high-energy ball milling crushing on the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy obtained in the step (1) for 4 hours to prepare (Dy, Tb) -Al-Cu alloy powder with the average particle size of 180 nm;

(3) preparing the high-abundance rare earth-containing low-melting-point (Pr, Ce) -Ga-Cu alloy obtained in the step (1) into an alloy thin strip by adopting a melt rapid quenching method, wherein the rotating speed of a copper roller is 20 m/s; then crushing the alloy ribbon into (Pr, Ce) -Ga-Cu alloy powder with the average particle size of 5 mu m by planetary low-energy ball milling, wherein the ball milling time is 1 h;

(4) mixing the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy powder obtained in the step (2) and the high-abundance rare earth-containing low-melting-point (Pr, Ce) -Ga-Cu alloy powder obtained in the step (3) according to the mass ratio of 1:1, and then pouring the mixture into an anhydrous ethanol solution to prepare a pasty solution with the viscosity of 100 mmpa.s for later use;

(5) magnet surface treatment: degreasing and decontaminating the surface of a neodymium iron boron magnet (the mark is N45) with the cylinder size of 10 x 10 mm, degreasing the surface of the magnet for 10 s in dilute nitric acid with the concentration of 2% to remove an oxide film on the surface of the magnet, and finally ultrasonically cleaning the magnet in absolute ethyl alcohol solution for 1 min;

(6) obtained in the step (4)Uniformly coating the surface of the neodymium iron boron magnet obtained in the step (5) with the pasty solution, wherein the coating thickness is 2 mm; followed by N₂And performing primary and secondary tempering heat treatment under the assistance of gas protection and a low magnetic field, wherein the magnetic field intensity is 0.5T, the temperature of the primary tempering heat treatment is 700 ℃, the heat preservation time is 9 h, then, the primary tempering heat treatment is rapidly cooled to the room temperature, the temperature of the secondary tempering heat treatment is 600 ℃, the heat preservation time is 4 h, and then, the primary tempering heat treatment is rapidly cooled to the room temperature, so that the high-coercivity neodymium-iron-boron magnet is obtained.

Through magnetic performance tests, the neodymium iron boron permanent magnet prepared by the invention has the intrinsic coercive force of 18.69 kOe, the remanence of 13.52 kG and the magnetic energy product of 44.78 MGOe.

Example 2

(1) According to atom percentage, low melting point Dy containing heavy rare earth₅₀Tb₂₅Al₁₀Cu₁₅Alloy and low-melting-point Pr containing high-abundance rare earth₅₀Ce₂₅Ga₁₀Cu₁₅Respectively weighing each raw material for alloy components, and carrying out arc melting to obtain a (Dy, Tb) -Al-Cu alloy and a (Pr, Ce) -Ga-Cu alloy;

(2) carrying out high-energy ball milling crushing on the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy obtained in the step (1) for 7 hours to prepare (Dy, Tb) -Al-Cu alloy powder with the average particle size of 100 nm;

(3) preparing the high-abundance rare earth-containing low-melting-point (Pr, Ce) -Ga-Cu alloy obtained in the step (1) into an alloy thin strip by adopting a melt rapid quenching method, wherein the rotating speed of a copper roller is 30 m/s; then crushing the alloy ribbon into (Pr, Ce) -Ga-Cu alloy powder with the average particle size of 7 mu m by planetary low-energy ball milling, wherein the ball milling time is 2 h;

(4) mixing the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy powder obtained in the step (2) and the high-abundance rare earth-containing low-melting-point (Pr, Ce) -Ga-Cu alloy powder obtained in the step (3) according to the mass ratio of 2:1, and then pouring the mixture into an anhydrous ethanol solution to prepare a pasty solution with the viscosity of 150 mmpa.s for later use;

(5) magnet surface treatment: degreasing and decontaminating the surface of a neodymium iron boron magnet (the mark is N45) with the cylinder size of 10 x 10 mm, degreasing the surface of the magnet for 10 s in dilute nitric acid with the concentration of 2% to remove an oxide film on the surface of the magnet, and finally ultrasonically cleaning the magnet in absolute ethyl alcohol solution for 2 min;

(6) uniformly coating the pasty solution obtained in the step (4) on the surface of the neodymium iron boron magnet obtained in the step (5), wherein the coating thickness is 3 mm; followed by N₂And performing primary and secondary tempering heat treatment under the assistance of gas protection and a low magnetic field, wherein the magnetic field intensity is 0.7T, the temperature of the primary tempering heat treatment is 850 ℃, the heat preservation time is 8 h, then quenching is performed to the room temperature, the temperature of the secondary tempering heat treatment is 500 ℃, the heat preservation time is 6 h, and then quenching is performed to the room temperature, so that the high-coercivity neodymium-iron-boron magnet is obtained.

Through magnetic performance tests, the neodymium iron boron permanent magnet prepared by the invention has the intrinsic coercive force of 19.21 kOe, the remanence of 13.48 kG and the magnetic energy product of 44.89 MGOe.

Example 3

(1) According to atom percentage, low melting point Dy containing heavy rare earth₃₀Tb₄₅Al₂₀Cu₅Alloy and low-melting-point Pr containing high-abundance rare earth₇₀Ce₅Ga₅Cu₂₀Respectively weighing each raw material for alloy components, and carrying out arc melting to obtain a (Dy, Tb) -Al-Cu alloy and a (Pr, Ce) -Ga-Cu alloy;

(2) carrying out high-energy ball milling crushing on the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy obtained in the step (1) for 10 hours to prepare (Dy, Tb) -Al-Cu alloy powder with the average particle size of 60 nm;

(3) preparing the high-abundance rare earth-containing low-melting-point (Pr, Ce) -Ga-Cu alloy obtained in the step (1) into an alloy thin strip by adopting a melt rapid quenching method, wherein the rotating speed of a copper roller is 40 m/s; then crushing the alloy ribbon into (Pr, Ce) -Ga-Cu alloy powder with the average particle size of 10 mu m by planetary low-energy ball milling, wherein the ball milling time is 3 h;

(4) mixing the heavy rare earth-containing low-melting-point (Dy, Tb) -Al-Cu alloy powder obtained in the step (2) and the high-abundance rare earth-containing low-melting-point (Pr, Ce) -Ga-Cu alloy powder obtained in the step (3) according to the mass ratio of 3:1, and then pouring the mixture into an anhydrous ethanol solution to prepare a pasty solution with the viscosity of 200 mmpa.s for later use;

(5) magnet surface treatment: degreasing and decontaminating the surface of a neodymium iron boron magnet (the mark is N45) with the cylinder size of 10 x 10 mm, degreasing the surface of the magnet for 10 s in dilute nitric acid with the concentration of 2% to remove an oxide film on the surface of the magnet, and finally ultrasonically cleaning the magnet in absolute ethyl alcohol solution for 3 min;

(6) uniformly coating the pasty solution obtained in the step (4) on the surface of the neodymium iron boron magnet obtained in the step (5), wherein the coating thickness is 5 mm; followed by N₂And performing primary and secondary tempering heat treatment under the assistance of gas protection and a low magnetic field, wherein the magnetic field intensity is 1T, the temperature of the primary tempering heat treatment is 980 ℃, the heat preservation time is 7 h, then quenching is performed to the room temperature, the temperature of the secondary tempering heat treatment is 400 ℃, the heat preservation time is 8 h, and then quenching is performed to the room temperature, so that the high-coercivity neodymium-iron-boron magnet is obtained.

Through magnetic performance tests, the neodymium iron boron permanent magnet prepared by the invention has the intrinsic coercive force of 21.22 kOe, the remanence of 13.39 kG and the magnetic energy product of 44.75 MGOe.