KR102045406B1 - Method Of rare earth sintered magnet - Google Patents

Abstract

The present invention relates to a method for manufacturing a rare-earth permanent magnet. According to the present invention, the method for manufacturing a rare-earth permanent magnet comprises: a step of manufacturing a rare-earth permanent magnet of composition of xwt%RE-ywt%B-zwt%TM-bal.wt%Fe (RE=rare-earth element, TM=3d transition element, x=28~35, y=0.5~1.5, z=0~15); a step of processing the rare-earth permanent magnet in a predetermined size; a step of washing the rare-earth permanent magnet sintered; a step of applying heavy rare-earth metal hydrogen compound onto the surface of the rare-earth permanent magnet washed; a step of laminating the rare-earth permanent magnet applied with the heavy rare-earth metal hydrogen compound in a lamination box by release agent powder at multiple layers; a step of inserting the lamination box in which the rare-earth permanent magnet applied with the heavy rare-earth metal hydrogen compound is laminated by the multiple layers into a heating furnace and diffusing the rare-earth element onto a crystal grain of the rare-earth permanent magnet at a vacuum atmosphere or an inert gas atmosphere; a stress removing heat treatment step of inserting the rare-earth permanent magnet in which the heavy rare-earth metal is diffused onto the crystal grain of the rare-earth permanent magnet into the heating furnace and removing the stress and performing heat treatment at the vacuum atmosphere or the inert gas atmosphere; and a final heat treatment step of performing heat treatment after the stress removing heat treatment step.

Description

Method of manufacturing rare earth permanent magnets {Method Of rare earth sintered magnet}

The present invention is to prevent the fusion of rare earth permanent magnets located in the upper and lower portions by placing a release agent between the rare earth permanent magnet when laminating the rare earth permanent magnet coated with heavy rare earth metal in multiple stages to improve the magnetic properties of the rare earth permanent magnet In addition, the present invention relates to a method for producing a rare earth permanent magnet, in which the diffusivity of the heavy rare earth metal applied to the rare earth permanent magnet is equalized.

Recently, the energy reduction and environmentally friendly green growth projects have emerged as a new issue, and the automobile industry is using hybrid cars using internal combustion engines using fossil raw materials in combination with motors or hydrogen, an environmentally friendly energy source, as alternative energy. The research on the fuel cell vehicle which generates and drives the motor has been actively conducted.

Since these environmentally friendly cars are driven by electric energy, permanent magnet motors and generators are inevitably employed. In terms of magnetic materials, rare earth permanent motors exhibiting higher residual flux density and stable coercive force to further improve energy efficiency. The technical demand for magnets is increasing.

In addition, other aspects for improving fuel efficiency of automobiles should be realized in light weight and miniaturization of automotive parts. For example, in the case of motors, in order to realize light weight and miniaturization, permanent magnet materials are used in addition to the design of the motor. It is essential to replace magnets with rare earth permanent magnets that exhibit better magnetic performance.

Rare earth NdFeB sintered magnets are increasingly being used for motors such as hybrid cars, and the coercive force Hcj is required to be further increased. In order to increase the coercive force (Hcj) of the NdFeB sintered magnet, a method of substituting a part of Nd with Dy or Tb is known, but the resources of Dy and Tb are insufficient and ubiquitous. The problem is that the residual magnetic flux density (Br) and the maximum energy product ((BH) max) of the NdFeB sintered magnet decrease.

In recent years, Dy or Tb adheres to the surface of an NdFeB sintered magnet by sputtering, and when heated to 700 to 1000 ° C., the coercive force Hcj can be increased without substantially reducing the residual magnetic flux density (Br) of the magnet. It was found that there is. (Non-patent documents 1 to 3)

Dy and Tb adhering to the magnet surface are sent to the inside of the sintered body through the grain boundaries of the sintered body, and from each grain inside the particles of the main phase RE ₂ Fe ₁₄ B (RE is a rare earth element) from the grain boundaries. At this time, since the RE rich phase of the grain boundary is liquefied by heating, the diffusion rate of Dy and Tb in the grain boundary is much faster than the diffusion rate into the columnar particles from the grain boundary.

By adjusting the heat treatment temperature and time by using the difference in the diffusion rate, a high concentration of Dy or Tb can be realized only in a region (surface region) extremely close to the grain boundaries of the columnar particles in the sintered body throughout the sintered body. have. Since the coercive force (Hcj) of the NdFeB sintered magnet is determined according to the state of the surface region of the columnar particles, the NdFeB sintered magnet having a high grain Dy or Tb concentration has a high coercive force. When the concentration of Dy or Tb is increased, the residual magnetic flux density (Br) of the magnet decreases, but since such a region is only the surface area of each columnar particle, the residual magnetic flux density (Br) hardly decreases for the entire columnar particle. Do not. In this way, the coercive force (Hcj) is large, and the residual magnetic flux density (Br) can produce NdFeB sintered magnets, which do not substitute Dy or Tb, and high-performance magnets that do not change much. This method is called grain boundary diffusion method.

As an industrial production method of NdFeB sintered magnet by grain boundary diffusion method, Dy or Tb fluoride or oxide fine powder layer is formed on the surface of NdFeB sintered magnet and heated, or Dy or Tb fluoride or oxide powder A method of embedding and heating an NdFeB sintered magnet in a mixed powder of a powder of perhydrogenated Ca has already been published (Non-Patent Documents 4 and 5).

The heavy rare earth metal Dy or Tb hydrogen compound slurry is applied to the surface of the NdFeB sintered magnet, and then laminated in a multi-layer, charged in a diffusion furnace and heated, whereby the laminated upper and lower NdFeB sintered magnets are fused to each other by the weight of the sintered magnet stacked thereon. In this case, the applied heavy rare earth metal is not uniformly diffused to the grain boundaries of the sintered magnet. In addition, the inconvenience of having to separate the sintered magnet is generated.

Conventionally, the rare earth permanent magnet sintered body is placed on an alumina plate, and the alumina plate is laminated on the rare earth permanent magnet sintered body, and then stacked in a diffusion furnace and heated, but the alumina plate used in such a lamination method has a thickness. It cannot be thinned below 5mm and has a disadvantage in that the rare earth permanent magnet sintered body is not charged when it is charged once in the charging path, and the alumina plate has a heat insulation function, and when heated, it is heated to the diffusion temperature in the contact with the alumina plate. There is a disadvantage that the difference in the diffusion rate on the surface of the rare earth permanent magnet sintered body, and the difference in the depth of heavy rare earth metal on the surface of the rare earth permanent magnet sintered body is generated when the diffusion is heated later than the surface.

Patent Literature 1 discloses a technique of dispersing a metal sintered rare earth metal powder between sintered compacts and sintering, and then immersing in a nitric acid aqueous solution to separate the sintered compacts. This is inconvenient to be immersed in an aqueous solution of nitric acid, and then washed.

Patent Literature 2 discloses a technique of dispersing a rare earth metal powder compact by sintering the oxide powder between the compacts during sintering. At this time, the oxide is reduced at the molding temperature, the amount of oxygen on the surface of the rare earth permanent magnet is increased, there is a disadvantage that the magnetic properties deteriorate.

Japanese Laid-Open Patent Publication No. 2006-097092 (published April 13, 2006) Japanese Patent Laid-Open No. 2001-335808 (published 04 December 2001)

[Non-Patent Document 1] KT Park et al, "Effect of Metal-Coating and Consecutive Heat Treatment on Coercivity of Thin Nd-Fe-B Sintered Magnets", Proceedings of the Sixteenth International Workshop on Rare-Earth Magnets and their Applications (2000), pp 257-264 [Non-Patent Document 2] Naoyuki Ishigaki et al, "Surface Modification and Characteristics Improvement of Micro-sized Neodymium Sintered Magnet", NEOMAX Technical Report, published by Kabusiki Kaisha NEOMAX, vol 15 (2005), pp 15-19 [Non-Patent Document 3] Ken-ichi Machida et al, "Grain Boundary Modification and Magnetic Characteristics of Sintered NdFeB Magnet", Speech Summaries of 2004 Spring Meeting of Japan Society of Powder and Powder Metallurgy, published by the Japan Society of Powder and Powder Metallurgy, 1-47A [Non-Patent Document 4] Kouichi Hirota et al, "Increase in Coercivity of Sintered NdFeB Magnet by Grain Boundary Diffusion Method", Speech Summaries of 2005 Spring Meeting of Japan Society of Powder and Powder Metallurgy, published by the Japan Society of Powder and Powder Metallurgy, p143 [Non-Patent Document 5] Ken-ichi Machida et al, "Magnetic Characteristics of Sintered NdFeB Magnet with Modified Grain Boundary", Speech Summaries of 2005 Spring Meeting of Japan Society of Powder and Powder metallurgy, published by the Japan Society of Powder and Powder Metallurgy, p144

The present invention is to solve the problems occurring when the rare earth permanent magnet sintered body is laminated in this way, specifically, when the rare earth permanent magnet coated with heavy rare earth metal is laminated in multiple stages by placing a release agent between the rare earth permanent magnet rare earth permanent magnet It is to provide a method for producing a rare earth permanent magnet to prevent fusion to each other and to equalize the diffusibility of heavy rare earth metal applied to the rare earth permanent magnet.

Another object of the present invention is to reduce the difference in the depth of diffusion of heavy rare earth metal on the surface of the rare earth permanent magnet because there is no difference in the diffusion rate on the rare earth permanent magnet surface when the heavy rare earth metal grain boundary diffusion.

Another object of the present invention is to prevent the deterioration of magnetic properties of the rare earth permanent magnet by reducing the release agent at the diffusion temperature to increase the amount of oxygen on the surface of the rare earth permanent magnet.

Another object of the present invention is to reduce the thickness of the release agent positioned between the rare earth permanent magnet to increase the amount of charge by heating the rare earth permanent magnet once compared to the conventional alumina plate.

In order to achieve the object as described above, the method for producing a rare earth permanent magnet according to the present invention, xwt% RE-ywt% B-zwt% TM-bal.wt% Fe (RE = rare earth element, TM = 3d transition element preparing a rare earth alloy having a composition of x = 28 to 35, y = 0.5 to 1.5, and z = 0 to 15); Grinding the prepared alloy to a size of 1.0 to 5.0 μm or less; Magnetizing the ground alloy by magnetic field orientation and compression molding to produce a rare earth permanent magnet; Sintering the magnetized rare earth permanent magnet; Processing the sintered rare earth permanent magnet to a predetermined standard; Cleaning the sintered rare earth permanent magnet; Applying a heavy rare earth metal hydrogen compound to the surface of the washed rare earth permanent magnet; The rare earth permanent magnet to which the rare earth hydrogen compound is applied is placed in a stacking box, and the rare earth permanent magnet to which the releasing agent powder, the rare earth metal hydrogen compound is applied, the releasing agent powder, and the rare earth permanent magnet to which the heavy rare earth metal hydrogen compound is applied are in order. Stacking the coated rare earth permanent magnets in multiple stages; Charging a multi-layer laminated box in which the rare earth permanent magnets coated with the rare earth metal hydrogen compound are stacked in a heating furnace, and diffusing the rare earths in a crystalline phase of the rare earth permanent magnets in a vacuum or inert gas atmosphere; A stress removing heat treatment step of charging a rare earth permanent magnet having rare earth diffused therein into the grain boundary phase of the rare earth permanent magnet in a heating furnace and performing stress relief heat treatment in a vacuum or inert gas atmosphere; And a final heat treatment step of performing heat treatment after the stress relief heat treatment step.

In the method for preparing a rare earth permanent magnet according to the present invention, a method for producing a heavy rare earth metal hydrogen compound is obtained by melting one or more heavy rare earth metals in an argon atmosphere at a high temperature by induction heating, followed by heavy rare earth metals by chill molding casting. Prepare ingots. The heavy rare earth metal ingot prepared above was coarsely ground in a size of several mm to several cm, and then charged into a vacuum furnace. After evacuating the inside of the vacuum furnace using a vacuum pump, the hydrogen was again filled at atmospheric pressure and stored at room temperature. Heavy rare earth metal hydride is prepared while heating to 500 ℃ range. The heavy rare earth metal hydrogen compound is kneaded in an alcohol solvent to prepare a heavy rare earth metal hydrogen compound slurry by grinding the heavy rare earth metal powder into a size of 1 to 2 μm by a wet grinding method.

The heavy rare earth metal used in the heavy rare earth metal hydrogen compound application step is characterized in that the heavy rare earth metal hydrogen compound containing one or more heavy rare earth metals of Nd, Pr, La, Ce, Ho, Dy, Tb. . The heavy rare earth metal is preferably Dy.

In the method for producing a rare earth permanent magnet according to the present invention, the release agent powder used in the step of laminating the rare earth permanent magnet coated with the heavy rare earth metal hydrogen compound is characterized in that at least one of carbon powder, alumina powder, BN powder, and MoS2 powder. do.

In the method for preparing a rare earth permanent magnet according to the present invention, the release agent powder used in the step of laminating the rare earth permanent magnet coated with the heavy rare earth metal hydrogen compound is a release agent powder slurry kneaded with an organic solvent, which is alcohol, more specifically, ethanol. It features.

In the method of manufacturing a rare earth permanent magnet according to the present invention, the rare earth permanent magnet coated with the heavy rare earth metal hydrogen compound is laminated in two to ten layers.

In the method for producing a rare earth permanent magnet according to the present invention, the release agent powder slurry is applied to a predetermined thickness by spray coating. The release agent powder slurry coating thickness is applied in the range of 0.2 mm to 2 mm, and preferably in the range of 0.5 mm to 1.5 mm.

In the manufacturing method of the rare earth permanent magnet according to the present invention, the release agent powder does not react with the rare earth permanent magnet and the rare earth metal at the diffusion temperature of the heavy rare earth metal hydrogen compound, and the heavy rare earth metal is the rare earth metal as the grain boundary of the rare earth permanent magnet. Characterized in that the material does not interfere with the diffusion.

In the method for preparing a rare earth permanent magnet according to the present invention, the size of the release agent powder used in the step of laminating the rare earth permanent magnet coated with the heavy rare earth metal hydrogen compound is characterized by having a powder particle size in the range of 10 nm to 500 μm. Preferably, the size of the release agent powder is characterized in that it has a powder particle size in the range of 1 ~ 10㎛.

In the method for producing a rare earth permanent magnet according to the present invention, the diffusion temperature in the step of diffusing the heavy rare earth metal into the grain boundary phase of the rare earth permanent magnet is 6 hours at 900 ℃ or 10 hours at 800 ℃ temperature, 9 hours at 850 ℃ temperature It is characterized by maintaining.

In the method for producing a rare earth permanent magnet according to the present invention, the heat treatment temperature is performed for 2 to 15 hours under a stress removing heat treatment of the rare earth permanent magnet having the rare earth diffused therein in a 400 to 1000 ° C range. Preferably, the stress relief heat treatment is performed for 8 to 12 hours at a temperature of 850 to 950 ° C.

According to the method of manufacturing a rare earth permanent magnet according to the present invention, when the rare earth permanent magnet coated with heavy rare earth metal is laminated in multiple stages, a release agent may be placed between the rare earth permanent magnets to prevent the rare earth permanent magnets from being fused to each other. have.

According to the method for producing a rare earth permanent magnet according to the present invention, when the rare earth permanent magnet coated with heavy rare earth metal is laminated in multiple stages, the difference between the heating temperature in the face of the release agent located between the rare earth permanent magnet and the surface not in contact with the release agent Low, there is an effect that the diffusion of heavy rare earth metal applied to the rare earth permanent magnet surface is even.

According to the method of manufacturing a rare earth permanent magnet according to the present invention, there is no difference in the diffusion rate on the surface of the rare earth permanent magnet during the grain boundary diffusion of the heavy rare earth metal, thereby reducing the difference in the depth of diffusion of the heavy rare earth metal on the surface of the rare earth permanent magnet. .

 According to the method for preparing a rare earth permanent magnet according to the present invention, the release agent does not react with the rare earth permanent magnet and the heavy rare earth metal at the diffusion temperature, so the rare earth metal does not interfere with the diffusion of the heavy rare earth metal into the grain boundary phase of the rare earth permanent magnet. The magnetic properties of the permanent magnets do not deteriorate.

According to the method of manufacturing a rare earth permanent magnet according to the present invention, the thickness of the release agent positioned between the rare earth permanent magnets becomes thin, and thus the charging amount of the rare earth permanent magnet is increased by one heating of the rare earth permanent magnet as compared with the conventional alumina plate.

1 is a flowchart illustrating a method of manufacturing a rare earth permanent magnet according to the present invention;
2 is a flow chart of laminating a rare earth permanent magnet coated with a rare earth metal according to the present invention via a release agent.
Figure 2 is an illustration of a rare earth permanent magnet laminated structure coated with a heavy rare earth metal of the prior art,
Figure 4 is an illustration of a rare earth permanent magnet laminated structure coated with a rare earth metal according to the present invention.

Hereinafter, the present invention will be described in more detail. Hereinafter, "upward", "downward", "forward" and "rear" and other directional terms are defined based on the states shown in the figures.

[Manufacturing method]

[Preparation process]

As a starting powder, a powder made of a rare earth alloy is prepared. The rare earth alloy is at least one selected from RE = Y, La, Ce, Pr, Nd, Dy, Tb, and Sm, and at least one selected from Fe, TM = 3d transition metal, B, and RE-Fe. Alloys, or RE-Fe-TM alloys, RE-Fe-B alloys, and RE-Fe-TM-B alloys. More specifically, Nd-Fe-B alloy, Nd-Fe-Co alloy, Nd-Fe-Co-B alloy, etc. are mentioned. A powder made of a known rare earth alloy used for the rare earth sintered magnet can be used for the raw material powder.

The raw material powder is pulverized by a pulverizing apparatus such as a jet mill, an atrita mill, a ball mill, a vibration mill, or the like by melting a molten cast ingot made of an alloy of a desired composition or a thin body obtained by a quench solidification method. It can manufacture using the atomization method like the maize method. You may further grind | pulverize and use the powder obtained by the manufacturing method of a well-known powder, and the powder manufactured by the atomizing method. By changing grinding | pulverization conditions and manufacturing conditions suitably, the particle size distribution of a raw material powder and the shape of each particle which comprises a powder can be adjusted. Although the shape of particle | grains does not matter in particular, it is easy to densify as it becomes closer to a true spherical particle, and particle | grains tend to rotate by application of a magnetic field. By using the atomizing method, a powder having high sphericity can be obtained.

In this case, the process of preparing the raw material powder from the alloy ingot is preferably carried out in nitrogen or inert gas atmosphere in order to prevent the contamination of oxygen and deterioration of magnetic properties.

A raw material powder is one of the characteristics characterized by containing the fine particle whose particle diameter is 2-10 micrometers. The particle size of the raw material powder is a value measured by a laser diffraction particle size distribution device.

The finer the raw material powder is, the easier it is to increase the packing density. Therefore, the maximum particle size is more preferably 10 µm or less.

A lubricant may be added to the raw material powder. When a mixture containing a lubricant is used, each particle constituting the raw material powder is easily rotated when the magnetic field is applied, and the orientation is easily increased. As the lubricant, various materials and forms (liquid and solid) that do not substantially react with the raw material powder may be used. Examples of the liquid lubricant include ethanol, machine oil, silicone oil, castor oil, and the like, and solid lubricants include metal salts such as zinc stearate, hexagonal boron nitride, and wax. The addition amount of a lubricating agent is 0.01 mass% or more and about 10 mass% or less with respect to 100 g of raw material powder with a liquid lubricant, and 0.01 mass% or more and 5 mass% or less with respect to the mass of a raw material powder are mentioned with a solid lubrication agent.

[Mold Filling Process]

The molding die of a desired shape and size is prepared so as to obtain a press-molded article of a desired shape and size. The molding die can be used in the manufacture of a compacted compact, which is conventionally used for a raw material of a sintered magnet, and typically, one having a die and a vertical punch. In addition, hydrostatic press (Cold Isostatic Press) can be used.

[Orientation process]

When the raw material powder is filled in the molding die, a direct current generated by applying a pulse current to the electromagnets located on the left and right sides of the molding die in a nitrogen atmosphere to generate a high magnetic field to completely orient the powder and then apply a direct current. A rare earth permanent magnet is produced by compression molding while maintaining the direction of the powder already fully oriented by the magnetic field.

[Sintering process]

The rare earth permanent magnet obtained by the magnetic field molding is charged into a sintering furnace and sufficiently maintained in a vacuum atmosphere and at 400 ° C. or lower to completely remove residual impurities.

It sinters again on conditions of 900 degreeC-1200 degreeC which are sintering conditions, holding time: 0.5 hour-3 hours, atmosphere: vacuum, argon. Preferably the temperature range of 1,000-1,100 degreeC is preferable, and the holding time of 1 to 2 hours and 30 minutes is preferable.

[Predetermined size machining process]

Sintered rare earth permanent magnets are processed into 12.5 * 12.5 * 5mm magnets.

[Cleaning Process]

After dipping the rare earth permanent magnet into the alkaline degreasing agent solution, rubbing it with a ceramic ball of 2 ~ 10mm in size and removing the oil component on the magnet surface, the remaining magnet was cleaned by distilled water several times. Degreaser was completely removed.

[Application process of heavy rare earth metal hydrogen compound on the washed rare earth permanent magnet]

In the method for preparing a rare earth permanent magnet according to the present invention, a method for producing a heavy rare earth metal hydrogen compound is obtained by melting one or more heavy rare earth metals at high temperature by induction heating in an argon atmosphere, followed by heavy rare earth metals by chill molding casting. Prepare ingots. The heavy rare earth metal ingot prepared above was coarsely ground in size of several mm to several cm, and then charged into a vacuum furnace. After evacuating the inside of the vacuum furnace using a vacuum pump, the hydrogen was again filled at atmospheric pressure and stored at room temperature. Heavy rare earth metal hydride is prepared while heating to 500 ℃ range. The heavy rare earth metal hydrogen compound is kneaded in an alcohol solvent to prepare a heavy rare earth metal hydrogen compound slurry by grinding the heavy rare earth metal powder into a size of 1 to 2 μm by a wet grinding method.

The heavy rare earth metal used in the heavy rare earth metal hydrogen compound application step is characterized in that the heavy rare earth metal hydrogen compound containing one or more heavy rare earth metals of Nd, Pr, La, Ce, Ho, Dy, Tb. . The heavy rare earth metal is preferably Dy.

The surface of the workpiece washed with the heavy rare earth metal hydride slurry is deposited in a beaker with the slurry prepared for uniform application of the heavy rare earth metal hydride compound, and then uniformly dispersed using an ultrasonic cleaner to deposit the workpiece. While maintaining for 2 minutes, the heavy rare earth metal hydride is uniformly applied to the rare earth permanent magnet surface.

[Method Lamination Process of Release Agent for Permanent Magnets Coated with Heavy Rare Earth Metal Hydrogen Compounds]

In the method for producing a rare earth permanent magnet according to the present invention, the rare earth permanent magnet 30 coated with the heavy rare earth metal hydrogen compound in the laminated box 10, a release agent powder, a rare earth permanent magnet coated with a heavy rare earth metal hydrogen compound, and a mold release powder (50), the rare earth permanent magnet (30) coated with the rare earth metal hydrogen compound is laminated in multiple stages as shown in FIG.

The release agent powder used in the step of laminating the rare earth permanent magnet coated with the heavy rare earth metal hydrogen compound may use at least one of carbon powder, alumina powder, BN powder, and MoS 2 powder.

In addition, the release agent powder 50 is preferably slurryed release agent powder 50 kneaded with an organic solvent which is an alcohol.

Spraying the slurry release agent powder and the organic solvent in the bottom of the laminated box 10, the rare earth permanent magnet coated with the heavy rare earth metal hydrogen compound on the release agent powder, and the slurry release agent powder and the organic solvent in the slurry form The spraying and the rare earth permanent magnets coated with the rare earth metal hydrogen compound are laminated in this order, and the rare earth permanent magnets coated with the heavy rare earth metal hydrogen compound are laminated, and the lamination is successively stacked in two to ten layers.

The laminated release agent powder (50) slurry coating thickness is applied in the range of 0.2mm ~ 2mm, preferably in the range of 0.5mm ~ 1.5mm.

The release agent powder 50 does not react with the rare earth permanent magnet or the heavy rare earth metal at the diffusion temperature of the heavy rare earth metal hydrogen compound, and the rare earth metal uses a material that does not prevent the rare earth from diffusing the rare earth onto the grain boundary of the permanent earth magnet. .

The size of the release agent powder 50 is characterized in that it has a powder particle size in the range of 10nm ~ 500㎛. Preferably the release agent powder has a particle size in the range of 1-10 μm.

The particle size of the release agent powder 50 and the coating thickness of the release agent powder 50 are heated at an equal temperature on the rare earth permanent magnet surface 30 to which the heavy rare earth metal hydrogen compound is applied during heating in the diffusion furnace, thereby increasing the diffusion speed and the depth of diffusion. It has the effect of keeping the function constant.

In addition, when the rare earth permanent magnet 30 coated with a rare earth metal hydrogen compound is laminated, a thinner release agent powder 50 may be sprayed to deposit a large number of permanent magnets.

This can increase the number of lamination 10 to 15% compared to the lamination method using the conventional alumina plate 40, the productivity is improved.

In FIG. 3 and FIG. 4, reference numeral 10 denotes a laminated box cover.

[Global diffusion process]

Charge the rare earth metal hydrogen compound coated rare earth permanent magnet laminated box 10 into a diffusion furnace and heat the heating rate at a heating rate of 1 ℃ / min. In an argon atmosphere while maintaining the diffusion temperature It is decomposed into heavy rare earth metals and diffused into the rare earth permanent magnets, so that the penetration reaction proceeds.

Preferably it is maintained for 6 hours at 900 ° C temperature or 10 hours at 800 ° C temperature, 9 hours at 850 ° C temperature.

By heating in this way, grain boundary diffusion can be easily carried out, so that the high characteristics of the rare earth permanent magnets, that is, the residual magnetic flux density (Br) or the maximum energy product ((BH) max) are higher than before the grain boundary diffusion treatment. It can hold | maintain and can make high coercive force (Hcj). The grain boundary diffusion method is also effective for thin-walled magnets. It is especially effective for the thickness of 5 mm or less.

[Stress Removal Heat Treatment and Final Heat Treatment]

After removing the heavy rare earth metal hydride slurry coating layer remaining on the surface after the grain boundary diffusion treatment, the stress relief heat treatment is performed at 400 ~ 1,000 ℃ temperature for 2 to 15 hours. Preferably, the stress relief heat treatment is performed for 8 to 12 hours at a temperature of 850 to 950 ° C.

After the stress relief heat treatment, the final heat treatment is performed at 400 ~ 600 ℃ temperature for 0.5 to 3 hours. Preferably, the final heat treatment is performed at 450 to 550 ° C. for 1.5 to 2.5 hours.

Hereinafter, more specific embodiment of this invention is described using a comparative example and an Example.

Table 1 shows a comparison of magnetic properties and fusion between stacking of rare earth permanent magnets in diffusion furnaces and 31wt% Nd-1wt% B-2wt% TM-Bal.Bal.wt% Fe (TM = Cu, Al, Nb , Co) After preparing a rare earth permanent magnet, the rare earth permanent magnet was divided into a 12.5 * 12.5 * 5mm size magnet.

Sample
Produce
Condition Process conditions Magnetic properties Adhesion Release Agent Heavy Rare Earth Hydrogen Compound Coating Amount Rare earth permanent magnets
Stacking number Residual flux
Density, Br (kG) Coercivity, Hcj
(kOe) Comparative Example 1 Alumina plate 1.0% 5th floor 14.0 17.8 Good Example 1 Carbon powder 1.0% 5th floor 13.9 19.5 Good Example 2 Alumana Powder 1.0% 5th floor 13.8 20.1 Good Example 3 MoS2 Powder 1.0% 5th floor 13.7 20.3 Good Example 4 Carbon powder 1.0% 10th floor 13.9 19.5 Good Example 5 Alumana Powder 1.0% 10th floor 13.8 20.1 Good Example 6 MoS2 Powder 1.0% 10th floor 13.7 20.3 Good

After dividing the rare earth permanent magnet into alkaline degreasing agent solution, rubbing it with a 2-10 mm ceramic ball to remove oil from the surface of the rare earth permanent magnet, and the rare earth permanent magnet was washed several times with distilled water. The remaining degreasing agent was thereby completely removed.

As a method of preparing a coating material for applying a rare earth diffusion material on the surface of the rare earth permanent magnet, Dy metal was melted at high temperature by an induction heating method in an argon atmosphere, and then prepared as a metal ingot by a chill molding casting method. After the manufactured metal ingots were coarsely crushed into a few mm to several cm in size, they were charged into a vacuum furnace, and after vacuuming the inside of the vacuum furnace using a vacuum pump, the hydrogen was again filled at atmospheric pressure and normal temperature to 500 ° C. The Dy hydrogen compound was produced while heating. The prepared Dy hydrogen compound was kneaded in an alcohol solvent to prepare a slurry of Dy hydrogen compound while grinding the rare earth alloy powder to a size of 1.5 μm by wet grinding.

The washed rare earth permanent magnet surface was uniformly dispersed using an ultrasonic cleaner containing Dy hydrogen compound slurry solution, and the Dy hydrogen compound was uniformly applied on the rare earth permanent magnet surface while maintaining the rare earth permanent magnet for 1 to 2 minutes after deposition.

Up to the above process, both Comparative Examples and Examples 1 to 6 are the same.

[Comparative Example]

As a method of loading the rare earth permanent magnets coated with the Dy hydrogen compound in a lamination box, the alumina plate was stacked in five layers using a 10 mm thickness of the existing alumina plate and loaded into a diffusion furnace.

The diffusion furnace was heated in an argon atmosphere at a heating rate of 1 ° C./min. And maintained at 900 ° C. for 6 hours to decompose Dy hydrogen compounds into Dy and diffuse into the magnet to allow penetration to proceed. After the diffusion treatment, the diffusion layer was removed from the surface, and then a stress relief heat treatment was performed at 900 ° C. for 10 hours, followed by a final heat treatment at 500 ° C. for 2 hours.

There was no fusion of residual magnetic flux density of 14.0 Br (kG) and coercive force of 17.8 Hcj (kOe) when using the conventional alumina plate as a comparative example.

Example 1

A mold release agent of carbon powder was used as a method of loading the rare earth permanent magnet coated with the Dy hydrogen compound into a lamination box. The average particle size of the carbon powder used was 5.0 µm, and the mold release slurry was uniformly sprayed to a thickness of 1 mm. Rare earth permanent magnets were stacked in five layers and loaded into the diffusion furnace.

The diffusion furnace was heated in an argon atmosphere at a heating rate of 1 ° C./min. And maintained at 900 ° C. for 6 hours to decompose Dy hydrogen compounds into Dy and diffuse into the magnet to allow penetration to proceed. After the diffusion treatment, the diffusion layer was removed from the surface, and then a stress relief heat treatment was performed at 900 ° C. for 10 hours, followed by a final heat treatment at 500 ° C. for 2 hours.

Example 2

A release agent of an alumina powder was used as a method of loading the rare earth permanent magnet coated with the Dy hydrogen compound into a lamination box. The average particle size of the alumina powder used was 5.1 µm, and the mold release slurry was uniformly sprayed to a thickness of 1 mm. Rare earth permanent magnets were stacked in five layers and loaded into the diffusion furnace.

The diffusion furnace was heated in an argon atmosphere at a heating rate of 1 ° C./min. And maintained at 900 ° C. for 6 hours to decompose Dy hydrogen compounds into Dy and diffuse into the magnet to allow penetration to proceed. After the diffusion treatment, the diffusion layer was removed from the surface, and then a stress relief heat treatment was performed at 900 ° C. for 10 hours, followed by a final heat treatment at 500 ° C. for 2 hours.

Example 3

A release agent of MoS ₂ powder was used as a method of loading the rare earth permanent magnet coated with the Dy hydrogen compound into a lamination box. The average particle size of the MoS ₂ powder used was 5.1 µm, and the mold release slurry was uniformly sprayed to a thickness of 1 mm. Rare earth permanent magnets were stacked in five layers and loaded into the diffusion furnace.

The diffusion furnace was heated in an argon atmosphere at a heating rate of 1 ° C./min. And maintained at 900 ° C. for 6 hours to decompose Dy hydrogen compounds into Dy and diffuse into the magnet to allow penetration to proceed. After the diffusion treatment, the diffusion layer was removed from the surface, and then a stress relief heat treatment was performed at 900 ° C. for 10 hours, followed by a final heat treatment at 500 ° C. for 2 hours.

When the release agents of Examples 1 to 3 were used, the residual magnetic flux density was 13.7 to 13.9 Br (kG), which was not significantly different from that of 14.0 Br (kG) of the comparative example, and the coercive force of Examples 1 to 3 was 19.5 to 20.3 Hcj (kOe). ), The coercive force of the comparative example was 17.8 Hcj (kOe) improved results. This may be due to the fact that the heating temperature is uniform across the surface of the rare earth permanent magnet due to the thin release agent, so that the diffusion rate and the depth of the heavy rare earth metal are equalized. In addition, in Examples 1-3, there was no fusion.

Example 4

A mold release agent of carbon powder was used as a method of loading the rare earth permanent magnet coated with the Dy hydrogen compound into a lamination box. The average particle size of the carbon powder used was 5.0 µm, and the mold release slurry was uniformly sprayed to a thickness of 1 mm. Rare earth permanent magnets were stacked in 10 layers and charged into the diffusion furnace.

The diffusion furnace was heated in an argon atmosphere at a heating rate of 1 ° C./min. And maintained at 900 ° C. for 6 hours to decompose Dy hydrogen compounds into Dy and diffuse into the magnet to allow penetration to proceed. After the diffusion treatment, the diffusion layer was removed from the surface, and then a stress relief heat treatment was performed at 900 ° C. for 10 hours, followed by a final heat treatment at 500 ° C. for 2 hours.

Example 5

A release agent of an alumina powder was used as a method of loading the rare earth permanent magnet coated with the Dy hydrogen compound into a lamination box. The average particle size of the alumina powder used was 5.1 µm, and the mold release slurry was uniformly sprayed to a thickness of 1 mm. Rare earth permanent magnets were stacked in 10 layers and charged into the diffusion furnace.

The diffusion furnace was heated in an argon atmosphere at a heating rate of 1 ° C./min. And maintained at 900 ° C. for 6 hours to decompose Dy hydrogen compounds into Dy and diffuse into the magnet to allow penetration to proceed. After the diffusion treatment, the diffusion layer was removed from the surface, and then a stress relief heat treatment was performed at 900 ° C. for 10 hours, followed by a final heat treatment at 500 ° C. for 2 hours.

Example 6

A release agent of MoS ₂ powder was used as a method of loading the rare earth permanent magnet coated with the Dy hydrogen compound into a lamination box. The average particle size of the MoS ₂ powder used was 5.1 µm, and the mold release slurry was uniformly sprayed to a thickness of 1 mm. Rare earth permanent magnets were stacked in 10 layers and charged into the diffusion furnace.

The diffusion furnace was heated in an argon atmosphere at a heating rate of 1 ° C./min. And maintained at 900 ° C. for 6 hours to decompose Dy hydrogen compounds into Dy and diffuse into the magnet to allow penetration to proceed. After the diffusion treatment, the diffusion layer was removed from the surface, and then a stress relief heat treatment was performed at 900 ° C. for 10 hours, followed by a final heat treatment at 500 ° C. for 2 hours.

When the release agents of Examples 4 to 6 were used, the residual magnetic flux density was 13.7 to 13.9 Br (kG), which did not show a significant difference from the 14.0 Br (kG) of the comparative example, and the coercive force of Examples 4 to 6 was 19.5 to 20.3 Hcj (kOe). ), The coercive force of the comparative example was 17.8 Hcj (kOe) improved results. This may be due to the fact that the heating temperature is uniform across the surface of the rare earth permanent magnet due to the thin release agent, so that the diffusion rate and the depth of the heavy rare earth metal are equalized. In addition, in Examples 4-6, there was no fusion.

In addition, this invention is not limited to the aspect of embodiment mentioned above, It is possible to change suitably, without deviating from the summary of this invention. For example, the composition of the raw material powder, the shape and size of the molded body, the magnetic field application rate, the sintering conditions, and the like can be appropriately changed.

Claims (5)

xwt% RE-ywt% B-zwt% TM-bal.wt% Fe (RE = rare earth element, TM = 3d transition element, x = 28-35, y = 0.5-1.5, z = 0-15) Preparing an alloy;
Grinding the prepared alloy to a size of 1.0 to 5.0 μm or less;
Magnetizing the ground alloy by magnetic field orientation and compression molding to produce a rare earth permanent magnet;
Sintering the magnetized rare earth permanent magnet;
Processing the rare earth permanent magnet to a predetermined standard;
Cleaning the processed rare earth permanent magnet;
Applying a heavy rare earth metal hydrogen compound to the surface of the washed rare earth permanent magnet;
Stacking the rare earth permanent magnets to which the heavy rare earth metal hydrogen compound is applied in a multi-layer by laminating a release agent powder in a lamination box;
Charging a multi-layer stack box in which the rare earth permanent magnets coated with the rare earth metal hydrogen compound are stacked in a heating furnace, and diffusing the rare earths in the vacuum or inert gas atmosphere onto the grain boundaries of the rare earth permanent magnets;
A stress removing heat treatment step of charging a rare earth permanent magnet in which heavy rare earth metal is diffused into the grain boundary of the rare earth permanent magnet in a heating furnace, and performing stress relief heat treatment in a vacuum or inert gas atmosphere;
After the stress relief heat treatment step after the final heat treatment step; consisting of,
The mediator in the lamination step via the release agent powder,
It is a release agent powder slurry which knead the release agent powder and the organic solvent,
The release agent powder does not react with the rare earth permanent magnet or the heavy rare earth metal at the diffusion temperature of the heavy rare earth metal hydrogen compound, so that the rare earth metal does not interfere with the diffusion of the rare earth into the grain boundary of the rare earth permanent magnet.
The size of the release agent powder is a powder particle size in the range of 1 ~ 10㎛,
The release agent powder slurry is applied by spraying the spray method,
Method for producing a rare earth permanent magnet, characterized in that the coating thickness of the release agent powder slurry is applied in the range of 0.2 ~ 2mm. The method of claim 1,
Heavy rare earth metal used in the application step of the heavy rare earth metal hydrogen compound is a rare earth permanent metal, characterized in that the heavy rare earth metal hydrogen compound containing one or more heavy rare earth metals of Nd, Pr, La, Ce, Ho, Dy, Tb Method of manufacturing a magnet. delete delete delete

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