Preparation method for efficiently improving coercive force of neodymium-iron-boron magnet

Abstract

The invention discloses a preparation method for efficiently improving the coercive force of a neodymium-iron-boron magnet, and belongs to the technical field of magnetic materials. The preparation method comprises the steps that a low-melting-point Dy45Nd35Co5Cu10Ga5 diffusion source alloy thin strip is prepared through a melt rapid quenching method, and magnetization treatment under pulses is conducted on a cylindrical neodymium-iron-boron magnet of a certain mark; and then the diffusion source alloy thin strips are flatly laid on the upper surface and the lower surface of the neodymium-iron-boron magnet to be diffused one by one under the magnetic adsorption effect and then subjected to subzero treatment and subsequent in-situ grain boundary diffusion high-pressure torsion heat treatment and tempering heat treatment, and the final high-coercivity magnet is obtained. The method is simple in technological process, easy to operate and beneficial to application of the high-coercivity neodymium-iron-boron magnet in more permanent magnet devices so as to meet market requirements.

Description

Technical Field

[0001] This invention relates to the field of magnetic materials, specifically to a method for preparing neodymium iron boron magnets with high efficiency. Background Technology

[0002] Rare earth elements are key raw materials for high-tech industries and are also non-renewable resources. How to fully and efficiently utilize rare earth materials is a common challenge faced by many rare earth application companies. High-performance rare earth magnetic materials are widely used in high-tech fields such as national defense and intelligent manufacturing, exhibiting superior performance. However, the addition of rare earth elements results in high costs (rare earth material costs account for approximately 80% of raw material costs). Grain boundary diffusion technology, developed in recent years, is a technique that can effectively improve the magnetic properties of sintered NdFeB magnets. It primarily uses rare earth metal or compound powders as a diffusion source, performing diffusion heat treatment at a specific temperature to enhance the magnetic properties of NdFeB magnets. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a method for efficiently enhancing the coercivity of neodymium iron boron magnets, which effectively overcomes the shortcomings of existing technologies.

[0004] This invention is achieved through the following technical solution: a method for efficiently improving the coercivity of neodymium iron boron magnets, comprising the following steps:

[0005] (1) A low-melting-point diffusion source alloy thin strip was prepared by melt quenching method. The composition of the diffusion source alloy thin strip was Dy by atomic percentage. 45 Nd 35 Co5Cu 10 For Ga5, the rotation speed of the copper roller during rapid quenching of the melt is 5–20 m / s;

[0006] (2) A cylindrical neodymium iron boron magnet with a size of 10×8 was magnetized under the action of a pulse current to obtain a neodymium iron boron magnet with a surface magnetic field of 400-800 Gs.

[0007] (3) Using magnetic adsorption, the diffusion source alloy strips obtained in step (1) are laid flat on the upper and lower surfaces of the neodymium iron boron magnet obtained in step (2), and then subjected to deep cryogenic treatment.

[0008] (4) The magnets processed in step (3) are subjected to in-situ grain boundary diffusion high-pressure torsion heat treatment and tempering heat treatment to obtain high coercivity NdFeB magnets.

[0009] As a preferred technical solution, the neodymium iron boron magnet in step (2) is of grade N40, N38M, N42SH, N38UH or N40EH, the magnetization period of the pulse magnetization treatment is 4 to 6 seconds, and the pulse current is 1000 to 10000A.

[0010] As a preferred technical solution, the cryogenic treatment temperature in step (3) is -180 to -130°C, the treatment time is 10 to 30 minutes, and then the magnet is placed in a vacuum environment to be warmed to room temperature, and the above cryogenic and warming treatment is repeated 2 to 5 times.

[0011] As a preferred technical solution, the in-situ grain boundary diffusion high-pressure torsion heat treatment in step (4) has a treatment temperature of 800-950℃, a heat treatment time of 200-400min, a pressure of 50-100MPa applied during the heat treatment, a torsion number of 1-3 turns, and is cooled to room temperature after the treatment is completed.

[0012] As a preferred technical solution, the tempering heat treatment temperature in step (4) is 400-500℃, the tempering time is 50-100min, and the temperature is cooled to room temperature after tempering.

[0013] As a preferred technical solution, the melt rapid quenching method forms the diffusion source alloy strip by spraying melt onto the surface of a high-speed rotating copper roller and instantly cooling and solidifying it.

[0014] As a preferred technical solution, the pulse magnetization treatment causes the surface of the neodymium iron boron magnet to form a residual magnetic field that can adsorb the diffusion source alloy strip, thereby achieving an adhesion method that does not require adhesives or solvents.

[0015] As a preferred technical solution, the cryogenic treatment is achieved through liquid nitrogen circulation or a compressor refrigeration device, which generates microcrack zones inside the magnet to increase the contact area between the diffuser and the magnet.

[0016] As a preferred technical solution, the diffusion source alloy strip has a thickness of 20-80 μm to ensure diffusion uniformity and adhesion stability.

[0017] The beneficial effects of this invention are as follows: This invention prepares a low-melting-point Dy45Nd35Co5Cu10Ga5 diffusion source alloy thin strip using a melt rapid quenching method, and then magnetizes a cylindrical NdFeB magnet of a certain grade under pulsed conditions. Subsequently, the diffusion source alloy thin strip is laid flat on the upper and lower surfaces of the NdFeB magnet to be diffused under magnetic adsorption, followed by cryogenic treatment and subsequent in-situ grain boundary diffusion high-pressure torsion heat treatment and tempering heat treatment to obtain the final high coercivity magnet. This invention designs a new diffusion source adhesion method, namely, obtaining a certain surface magnetic intensity of the NdFeB magnet through pulsed magnetization treatment, ensuring sufficient adhesion strength between the diffusion source alloy thin strip and the magnet substrate, and avoiding the adverse effects of solvents or adhesives on magnet performance. At the same time, cryogenic treatment can create a magnet with microcrack zones inside, significantly increasing the contact area between the diffuser and the magnet, and changing the limitation of the diffusion magnet depth. This invention simplifies the process, is easy to operate, has low cost, and is suitable for large-scale mass production. Detailed Implementation

[0018] All features disclosed in this specification, or steps in all methods or processes disclosed herein, may be combined in any way, except for mutually exclusive features and / or steps.

[0019] Example 1

[0020] (1) Low melting point Dy was prepared by melt rapid quenching method according to atomic percentage. 45 Nd 35 Co5Cu 10 Ga5 diffusion source alloy thin strip, copper roller rotation speed is 5m / s;

[0021] (2) A cylindrical NdFeB magnet with grade N40 and size 10×8 was subjected to pulse magnetization treatment. The magnetization period was 4s and the pulse current was 1000A to obtain a NdFeB magnet with surface magnetism of 400Gs.

[0022] (3) The low melting point Dy obtained in step (1) 45 Nd 35 Co5Cu 10 Under the magnetic adsorption, Ga5 diffusion source alloy strips are laid flat on the upper and lower surfaces of the NdFeB magnet to be diffused obtained in step (2). Then the magnet is placed in a cryogenic equipment for cryogenic treatment. The cryogenic treatment temperature is -135℃ and the treatment time is 10min. Then the magnet is placed in a vacuum environment to be warmed to room temperature. This step is repeated 3 times.

[0023] (4) The magnet after the cryogenic treatment in step (3) is subjected to in-situ grain boundary diffusion high pressure torsion heat treatment and tempering heat treatment. The in-situ heat treatment temperature of the in-situ grain boundary diffusion high pressure torsion heat treatment is 800℃, the heat treatment time is 380min, the pressure is 95MPa, the number of torsion turns is 3 turns, and then it is cooled to room temperature. The tempering heat treatment temperature is 400℃, the tempering time is 90min, and then it is cooled to room temperature to obtain the final high coercivity magnet.

[0024] The NdFeB magnet prepared using this invention has the following magnetic properties measured: remanence of 12.9 kG, intrinsic coercivity of 15.8 kOe, and magnetic energy product of 42.3 MGOe.

[0025] Example 2

[0026] (1) Low melting point Dy was prepared by melt rapid quenching method according to atomic percentage. 45 Nd 35 Co5Cu 10 Ga5 diffusion source alloy thin strip, copper roller rotation speed is 10m / s;

[0027] (2) A cylindrical NdFeB magnet with grade N38M and size 10×8 was subjected to pulse magnetization treatment with a magnetization period of 5s and a pulse current of 5000A to obtain a NdFeB magnet with a surface magnetic field of 550Gs.

[0028] (3) The low melting point Dy obtained in step (1) 45 Nd 35 Co5Cu 10 Under the magnetic adsorption, Ga5 diffusion source alloy strips are laid one by one on the upper and lower surfaces of the NdFeB magnet to be diffused obtained in step (2). Then the magnet is placed in a cryogenic equipment for cryogenic treatment. The cryogenic treatment temperature is -155℃ and the treatment time is 18min. Then the magnet is placed in a vacuum environment to warm up to room temperature. This step is repeated 3 times.

[0029] (4) The magnet after the cryogenic treatment in step (3) is subjected to in-situ grain boundary diffusion high pressure torsion heat treatment and tempering heat treatment. The in-situ heat treatment temperature of the in-situ grain boundary diffusion high pressure torsion heat treatment is 880℃, the heat treatment time is 290min, the pressure is 70MPa, the number of torsion turns is 3 turns, and then it is cooled to room temperature. The tempering heat treatment temperature is 450℃, the tempering time is 75min, and then it is cooled to room temperature to obtain the final high coercivity magnet.

[0030] The neodymium iron boron magnet prepared using this invention has the following magnetic properties measured: remanence is 12.5 kG, intrinsic coercivity is 19.2 kOe, and magnetic energy product is 39.8 MGOe.

[0031] Example 3

[0032] (1) Low melting point Dy was prepared by melt rapid quenching method according to atomic percentage. 45 Nd 35 Co5Cu 10 Ga5 diffusion source alloy thin strip, copper roller rotation speed is 20m / s;

[0033] (2) A cylindrical NdFeB magnet with grade N40EH and size 10×8 was subjected to pulse magnetization treatment. The magnetization period was 6s and the pulse current was 8000A, resulting in a NdFeB magnet with a surface magnetic field of 750Gs to be diffused.

[0034] (3) The low melting point Dy obtained in step (1) 45 Nd 35 Co5Cu 10 Under the magnetic adsorption, Ga5 diffusion source alloy strips are laid one by one on the upper and lower surfaces of the NdFeB magnet to be diffused obtained in step (2). Then the magnet is placed in a cryogenic equipment for cryogenic treatment. The cryogenic treatment temperature is -175℃ and the treatment time is 30min. Then the magnet is placed in a vacuum environment to be warmed to room temperature. This step is repeated 3 times.

[0035] (4) The magnet after the cryogenic treatment in step (3) is subjected to in-situ grain boundary diffusion high-pressure torsion heat treatment and tempering heat treatment. The in-situ heat treatment temperature is 950℃, the heat treatment time is 215min, the pressure is 55MPa, the number of torsion turns is 3 turns, and then it is cooled to room temperature. The tempering heat treatment temperature is 500℃, the tempering time is 50min, and then it is cooled to room temperature to obtain the final high coercivity magnet.

[0036] The neodymium iron boron magnet prepared using this invention has the following magnetic properties measured: remanence is 12.4 kG, intrinsic coercivity is 35.8 kOe, and magnetic energy product is 42.5 MGOe.

[0037] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions conceived without inventive effort should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for efficiently increasing the coercivity of neodymium-iron-boron magnets, characterized in that The method comprises the following steps: (1) A low melting point diffusion source alloy ribbon is prepared by a melt quenching method, and the composition of the diffusion source alloy ribbon is Dy 45 Nd 35 Co5Cu 10 Ga5, and the rotating speed of the copper roller in the melt quenching process is 5-20 m / s; (2) A cylindrical Nd-Fe-B magnet with a size of 10x8 is magnetized under the action of a pulse current to obtain a Nd-Fe-B magnet to be diffused with a surface magnetism of 400-800 Gs; (3) The diffusion source alloy ribbon obtained in step (1) is laid on the upper and lower surfaces of the Nd-Fe-B magnet obtained in step (2) by magnetic adsorption, and deep cooling treatment is performed thereon; (4) The magnet treated in step (3) is subjected to in-situ grain boundary diffusion high-pressure torsion heat treatment and tempering heat treatment to obtain a high-coercivity Nd-Fe-B magnet.

2. The method of claim 1, wherein the method comprises: The Nd-Fe-B magnet in step (2) has a grade of N40, N38M, N42SH, N38UH or N40EH, the magnetization cycle of the pulse magnetization treatment is 4-6 s, and the pulse current is 1000-10000 A. ​ 3. The method of claim 1, wherein the method further comprises: adding a rare earth element to the melt. The deep cooling treatment in step (3) is performed at a temperature of -180 to -130 ℃ for 10-30 min, and then the magnet is placed in a vacuum environment to warm up to room temperature, and the above deep cooling and warming up treatment is repeated for 2-5 times.

4. The method of claim 1, wherein the method is characterized by: The in-situ grain boundary diffusion high-pressure torsion heat treatment in step (4) is performed at a temperature of 800-950 ℃ for 200-400 min, a pressure of 50-100 MPa is applied during the heat treatment, and the magnet is twisted for 1-3 turns, and then cooled to room temperature.

5. The method of claim 1, wherein the method is characterized by: The tempering heat treatment in step (4) is performed at a temperature of 400-500 ℃ for 50-100 min, and then cooled to room temperature.

6. The method of claim 1, wherein the method is performed at a temperature of 800- 1000°C. The melt rapid quenching method sprays the melt onto the surface of a high-speed rotating copper roller and instantaneously cools and solidifies to form the diffusion source alloy ribbon.

7. The method of claim 1, wherein the method is characterized by: The pulse magnetization treatment forms a residual magnetic field on the surface of the Nd-Fe-B magnet, which can adsorb the diffusion source alloy ribbon, thereby realizing the attachment without the need for adhesives or solvents.

8. The method of claim 1, wherein the method is characterized by: The deep cooling treatment is realized by liquid nitrogen circulation or a compressor refrigeration device to generate micro-crack zones in the magnet to increase the contact area between the diffusion material and the magnet interface.

9. The method of claim 1, wherein the method is characterized by: The diffusion source alloy ribbon has a thickness of 20-80 μm to ensure diffusion uniformity and attachment stability.