KR101995542B1 - Manufacturing method of rare earth magnet - Google Patents

Abstract

The present invention provides a rare earth magnet sintered body comprising: a rare earth magnet sintered body including R, Fe, and B as a composition; Aging the heavy rare earth hydrogen compound in an organic solvent; Wet-coating the surface of the sintered body with the aged heavy rare-earth hydrogen compound; And subjecting the coating material to heat treatment to effect grain boundary diffusion.

Description

TECHNICAL FIELD [0001] The present invention relates to a rare-

The present invention relates to a method of manufacturing a rare-earth magnet.

In recent years, energy-saving and environmentally-friendly green growth projects have emerged as new issues. In the automobile industry, hybrid cars, which use internal combustion engines using fossil raw materials in parallel with motors, and hydrogen, which are environmentally friendly energy sources, And a fuel cell vehicle that drives the motor using the generated electricity. Since these environmentally friendly automobiles are commonly driven by electrical energy, permanent magnet type motors and generators are inevitably employed. In order to further improve energy efficiency in terms of magnetic materials, rare earth magnets Technical demand for sintered magnets is increasing. In addition to the driving motor, other aspects for improving the fuel efficiency of the environmentally friendly automobile are to achieve weight reduction and miniaturization of the automotive parts used in the steering device and electric device. For example, in order to achieve weight reduction and miniaturization, It is essential to replace the ferrite used in the past with a rare earth sintered magnet exhibiting better magnetic performance.

The above-mentioned environmentally-friendly automobiles are expected to be used in the future due to reasons such as rising oil prices due to an increase in energy consumption, solving health problems caused by environmental pollution, and a policy of regulating carbon generation due to long- Production is expected to increase gradually.

On the other hand, the permanent magnets employed in these environmentally friendly vehicles are required to maintain a high performance in terms of coercive force of 25 to 30 kOe or more, since the original function should be maintained stably without losing the performance of the magnet even in a high temperature environment of 200 캜.

Theoretically, the residual magnetic flux density of the permanent magnet is determined by conditions such as the saturation magnetic flux density of the main phase constituting the material, the degree of anisotropy of the crystal grains and the density of the magnet, and as the residual magnetic flux density increases, The advantage is that the efficiency and power of the device can be improved in various applications. On the other hand, the coercive force, which indicates the different performance of the permanent magnet, plays a role in maintaining the intrinsic performance of the permanent magnet in response to an environment in which the magnet is to be desorbed, such as heat, reverse magnetic field and mechanical impact. It can be used not only in high temperature appliances and high power devices but also because it can be manufactured by using a thin magnet so that its weight is reduced and its economic value is increased.

In order to produce the rare earth sintered magnets with high coercive force, 5 to 10 wt% of Nd or Pr alloy such as Nd or Pr is substituted with heavy rare earth such as Dy or Tb. However, the heavy rare earth such as Dy or Tb used at this time is 4 ~ 10 times higher than Kyung Hee soil such as Nd or Pr, and because there is a resource limitation that the reserves are not abundant globally, In order to expand the utilization field and solve the problem of smooth supply and demand, a new magnet manufacturing method is needed to improve the coercive force while minimizing the content of heavy rare earth.

From this point of view, research institutes and rare earth magnet manufacturing companies around the world have been working on developing coercivity while minimizing the use of heavy rare earths from the 2000s. As a representative method developed so far, a rare earth sintered magnet A rare earth metal-based diffusion method has been proposed which diffuses heavy rare earth on the surface of rare earth magnets to minimize the amount of heavy rare earths.

In the rare-earth grain boundary diffusion method, a sintered magnet is prepared and then a heavy rare earth compound such as heavy rare earth fluoride is coated on the surface of the magnet by various methods such as powder coating, vapor deposition and plating, and heated at 700 ° C or higher in argon or vacuum atmosphere, And the middle rare earths that have been applied to the surface gradually diffuse and penetrate along the magnetic grain boundaries. When the rare earths have penetrated into the magnet along the grain boundaries by the diffusion reaction, heavy rare earths are concentrated around the grain boundaries. Due to the intrinsic properties of the rare earth sintered magnet, magnetic defects that decrease the coercive force are mostly distributed in the grain boundaries. If the medium rare earths are distributed intensively, the coercive force is improved by removing the magnetic defects from the heavy rare earth.

When heavy rare earth fluoride is used for grain boundary diffusion, fluorine acts as an impurity. To solve this problem, heavy rare-earth hydrogen compounds were considered. However, as a result of the diffusion of the heavy rare earth hydrogen compounds, the process of managing and treating the generated hydrogen gas due to the generation of a large amount of hydrogen gas is added, and there is a danger of explosion and there is a great difficulty in mass production, There is no problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems,

There is provided a process for producing a rare-earth magnet capable of remarkably suppressing the generation of hydrogen gas and significantly improving magnet characteristics such as coercive force by agglomerating in a grain boundary using an intermediate rare earth compound containing a heavy rare earth hydride and aging in an organic solvent .

It is another object of the present invention to provide a rare earth magnet manufacturing method capable of improving the coercive force of a magnet while reducing the amount of heavy rare earths used.

As means for solving the above problem,

The present invention relates to a method for producing a rare-earth magnet sintered body, comprising the steps of preparing a rare-earth magnet sintered body containing R, Fe and B as constituent components (R is at least one selected from rare earth elements including Y and Sc) Aging in a solvent, wet-coating the surface of the sintered body with the aged heavy rare-earth hydrogen compound, and heat-treating the coating to diffuse the grain boundary.

The present invention also provides a process for producing a rare-earth magnet, wherein the heavy rare earth coating amount is in the range of 0.1 to 5% by weight relative to the rare earth magnet sintered body.

Further, the heavy rare earth hydrogen compound includes at least one of Dy-H and Tb-H.

Further, the organic solvent provides a process for producing a rare earth magnet containing an alcohol.

In addition, the above-mentioned aging step provides a method of producing a rare-earth magnet aging within a range of 10 ° C to 50 ° C within a range of 1 hour to 10 days.

Further, the heavy rare earth hydrogen compound has a mean particle size within the range of 0.5 to 8.5 mu m.

In addition, the step of wet-coating provides a method for producing a rare-earth magnet by slurrying it with an organic solvent used for aging.

Also, the temperature of the grain boundary diffusion step is in the range of 600 to 1000 占 폚.

Further, there is provided a method of manufacturing a rare-earth magnet further comprising a step of heat-treating the silicon substrate within a temperature range of 500 ° C to 900 ° C after the grain diffusion step to remove stress.

The method for producing a rare-earth magnet according to an embodiment of the present invention is a method for producing rare-earth magnets by using a rare earth metal compound containing a heavy rare earth hydride, Can be significantly improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it is needless to say that the present invention is not limited to these embodiments and can be modified into various forms.

Wherever certain parts of the specification are referred to as "comprising ", the description does not exclude other parts and may include other parts, unless specifically stated otherwise. Also, when a portion such as a layer, a film, an area, a plate, or the like is referred to as being "above" another portion, this includes not only the case directly above another portion but also the case where another portion is located in the middle. When a portion of a layer, film, region, plate, or the like is referred to as being "directly on" another portion, it means that no other portion is located in the middle.

A method for producing a rare-earth magnet according to an embodiment of the present invention includes the steps of preparing a rare-earth magnet sintered body containing R, Fe, and B as constituent components, aging a rare-earth hydrogen compound in an organic solvent, A step of wet-coating with a rare-earth hydrogen compound, and a step of heat-treating and spreading the coating by intergranular diffusion. Optionally, after the intergranular diffusion step, heat treatment is performed within a range of 600 ° C to 800 ° C to remove stress.

Each step will be described in detail below.

(1) preparing a rare earth magnet sintered body

The rare earth magnet sintered body can be prepared by the following method.

In order to prepare the rare earth magnet sintered body, a rare earth magnet powder containing R, Fe, and B as a composition component may be used. Here, R may be selected from one or more rare earth elements including Y and Sc, and one or more metal M may be selected as a composition component. Specific examples of M include Al, Ga, Cu, Ti, W, Pt, Au, Cr, Ni, Co, Ta and Ag. The rare earth magnet powder is not limited, but Nb-Fe-B sintered magnet powder can be used.

The composition of the rare earth magnet powder is not limited, but R is in the range of 27 to 36 wt%, M is in the range of 0 to 5 wt%, B is in the range of 0 to 2 wt%, and the balance Fe.

In one embodiment, the alloy of the above composition may be dissolved in a vacuum induction heating method and made into an alloy using a strip casting method. In order to improve the grindability of the gut of these alloys, hydrogen treatment and dehydrogenation treatment are carried out at a temperature ranging from room temperature to 600 ° C., and then grinding is carried out using a pulverizing method such as a jute mill, an atit tamil ball mill, It can be produced as a uniform and fine powder. It is preferable to carry out the step of producing the powder of 1 to 10 mu m from the gut as the alloy in a nitrogen or inert gas atmosphere in order to prevent oxygen from being contaminated and deteriorating the magnetic properties.

Then, magnetic field molding is performed using fine powder. As an example thereof, a kneaded powder is filled in a mold, a direct current magnetic field is applied by electromagnets located on the left and right sides of the mold, the kneaded powder is oriented, and compression molding is performed by upper / can do. The magnetic field forming process is preferably performed in a nitrogen or inert gas atmosphere in order to prevent oxygen from being contaminated and deteriorating magnetic properties.

After the magnetic field is formed, the formed body is sintered. The sintering conditions are not limited, but it is preferable to perform the sintering at a temperature within the range of 900 to 1100 ° C, and the temperature raising rate at 700 ° C or higher is preferably controlled within the range of 0.5 to 15 ° C / min.

As an example, a compact obtained by magnetic field molding is charged into a sintering furnace and sufficiently maintained at a temperature of 400 DEG C or lower in a vacuum atmosphere to completely remove the remaining impurity organic matter. The temperature is further raised to 900 to 1100 DEG C and maintained for 1 to 4 hours, Densify. The sintering atmosphere is preferably performed in an inert atmosphere such as vacuum and argon, and it is preferable to adjust the temperature raising rate at a temperature of 700 ° C or higher to 0.1 to 10 ° C / min., Preferably 0.5 to 15 ° C / min.

Alternatively, the sintered body after sintering may be stabilized by heat treatment in the range of 400 to 900 ° C for 1 to 4 hours, and then the sintered body may be processed to a predetermined size to produce a rare earth magnet sintered body.

(2) aging the rare-earth hydrogen compound in an organic solvent

The medium rare-earth hydrogen compound used for grain boundary diffusion is first aged in an organic solvent before wet application. In the case of not undergoing the aging process, compared with the case of aging, the generation of hydrogen gas is remarkably large, and the diffusion of the grain boundaries is unstable, and the coercive force shows a remarkable difference.

The organic solvent is not limited, but an alcohol solvent is preferable, and a polyhydric alcohol solvent such as ethanol, methanol, glycol and the like can be used. The aging step is not limited, but the aging is preferably performed within the range of 10 to 50 占 폚 within the range of 1 to 10 days, particularly preferably within the range of 1 to 10 days. Below this range, the effect of increasing the coercive force is insignificant, and when it exceeds the above range, the process time is longer than the coercive force improvement, which is inefficient.

The heavy rare earth hydrogen compound may include at least one selected from Dy-H and Tb-H, and may further include Ho-H. It is preferable to use the middle rare earth hydrogen compound having an average particle diameter in the range of 0.5 to 8.5 mu m. If it exceeds the above range, the grain boundary diffusion efficiency is lowered and the improvement of the coercive force is insignificant.

(3) wet-coating the surface of the sintered body with a heavy rare earth hydrogen compound

The aged rare-earth hydrogen compound is wet-coated on the surface of the sintered body by the above process. It is preferable that the aged rare-earth hydrogen compound is slurried with an organic solvent and applied, and it is preferable to slurry the organic solvent used in the aging process. Specifically, a heavy rare earth hydrogen compound is put into an organic solvent such as alcohol to make a slurry and aged, and then the sintered body is dipped in a slurry to be wet-coated.

The application amount of the rare earth magnet is preferably in the range of 0.1 to 5% by weight based on the rare earth magnet sintered body. Below this range, the increase of the coercive force is insignificant, and if it is out of the above range, the amount of heavy rare earth is increased compared with the effect, which is not preferable.

In addition to the heavy rare earth hydrogen compounds, heavy rare earth fluorides, heavy rare earth oxides, heavy rare earth oxides, transition metals, and the like may be mixed and wet-coated for intergranular diffusion.

(4) Grain diffusion step

Next, the step of heat-treating the coating material to diffuse the heavy rare earth by intergranular diffusion will be described in more detail as follows.

The coating material is charged into a heating furnace and subjected to heat treatment in a vacuum or an inert gas atmosphere at a temperature of 600 to 1,000 占 폚 to cause interlayer diffusion of heavy rare earths. The diffusion reaction may be carried out by raising the temperature at a temperature raising rate of 0.1 to 20 ° C / min. And maintaining the temperature within the range of 0.5 to 50 hours.

The coating material is charged into a heating furnace and slowly heated in a vacuum or argon atmosphere to reach a temperature in the range of 650 to 950 DEG C and then the heavy rare earth hydrogen compound is decomposed into a heavy rare earth metal while maintaining the temperature for 1 to 20 hours, So that the penetration reaction can proceed.

(5) Stress removing step

On the other hand, in the diffusion process, as the diffusion temperature increases, the amount of heavy soil penetrated into the magnet increases but the coercive force decreases rather. When the diffusion temperature is kept at 950 ° C for 4 hours, a serious crack is generated in the magnet It is expected that this is due to the fact that as the diffusion reaction progresses rapidly, the difference in the amount of heavy rare earth elements diffused on the surface and inside of the magnet becomes larger and the residual stress inside the magnet is generated.

In an embodiment of the present invention, in order to prevent residual stress from occurring in the magnet due to such a rapid diffusion, the rate of temperature rise from 700 ° C. at which the diffusion reaction starts to the respective diffusion temperatures is set to 0.1 to 20 ° C./min And adjusting the diffusion rate to prevent this. As another method, after the diffusion reaction is completed, heat treatment may be performed within the range of 500 ° C to 900 ° C to remove the stress. As a specific example, a first heat treatment for stress relief for 0.5 to 10 hours is performed in a temperature range of 600 to 900 ° C and a second heat treatment is performed for 1 to 10 hours in a temperature range of 500 to 600 ° C, Stress can be removed.

The method may further include a step of selectively treating the thus obtained diffusion with a metal, epoxy or resin system. Specifically, the finished product after completion of the grain boundary diffusion and post-heat treatment can be subjected to surface treatment such as Ni coating, Zn coating, electrodeposition coating and epoxy coating by finishing or pickling treatment.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

A rare earth sintered magnet comprising 27 to 36 parts by weight of RE, 64 to 73 parts by weight of Fe, 0 to 5 parts by weight of TM, and 0 to 2 parts by weight of B as a starting material. -> magnetic field forming process -> sintered body manufactured by sintering process and processed to size 12.5mm * 12.5mm * 5mm (magnetic field direction) was used.

The sintered body was immersed in an alkaline degreasing agent solution to remove foreign substances such as oil and surface rust on the surface, and then rubbed with a ceramic ball having a pie size of 5 to 10 to remove the oil component on the surface of the magnet , And the magnet was again cleaned several times with distilled water to completely remove the remaining degreasing agent. As a successive process, the degreased workpiece is immersed in a dilute nitric acid solution in a range of 1 to 10% in concentration to pick up the degreased workpiece for 1 to 5 minutes to completely remove the rust formed during processing. After the pickling, And transferred to distilled water. The remaining nitric acid on the surface of the magnet was removed using an ultrasonic washing machine and sufficiently dried.

To uniformly coat the surface of the sintered body with the heavy rare earth, the ratio of the Dy-H compound having an average particle diameter of 8.5 탆 and the alcohol was adjusted to 50%: 50%, uniformly kneaded, And allowed to stand for aging. Thereafter, the sintered body was immersed in a slurry of the aged heavy rare earth compound so that the coating amount of the heavy rare earth was 0.7 to 1.0 wt% of the weight of the magnet product.

In order to spread the applied rare earth compound to the grain boundary, the coating material was charged into a heating furnace, heated at a heating rate of 1 캜 / min in an argon atmosphere, maintained at 900 캜 for 5 hours, Decomposed and diffused into the magnet so that the penetration reaction proceeds. After the diffusion treatment, the diffusion layer was removed, and then the stress relieving heat treatment was performed at a temperature in the range of 850 ° C for 5 hours. Then, the magnet subjected to the final heat treatment at 500 ° C for one hour was evaluated for magnetic properties.

Table 1 shows the results of measurement of magnetic properties after intergranular diffusion according to aging time of Dy-H slurry. Comparisons 1-1 and 1-2 show the results of comparison between the case of no diffusion treatment and the case of diffusion of Dy-H slurry And the magnetic properties were evaluated.

As a result, the coercive force was remarkably improved as compared with the case where the fermentation was not performed, and the fermentation time was improved even when fermented for 1 hour and preferably aged for 1 to 10 days.

division Medium rare earth particle size
(탆) Slurry aging time
(Work) Diffusion / heat treatment conditions Coercivity
Hcj
(kOe) Diffusion temperature
(° C) Heat treatment temperature
(° C) Comparison 1-1 × × - - 22.0 Comparison 1-2 8.5 0 900 850/500 24.8 Sample 1-1 8.5 1 hours 900 850/500 25.9 Sample 1-2 8.5 One 900 850/500 26.5 Samples 1-3 8.5 2 900 850/500 27.4 Samples 1-4 8.5 5 900 850/500 28.0 Samples 1-5 8.5 10 900 850/500 28.0

Example 2

The results are shown in Table 2, except that the average particle size of the heavy rare earth compounds in Example 1 was changed as shown in Table 2 and the aging was performed for 5 days. It was confirmed that the coercive force was improved as the particle size of the rare earth metal compound was smaller.

division Medium rare earth particle size
(탆) Slurry aging time
(Work) Diffusion / heat treatment conditions Coercivity
Hcj
(kOe) Diffusion temperature
(° C) Heat treatment temperature
(° C) Comparison 1-1 × × - - 22.0 Sample 2-1 8.5 5 900 850/500 28.0 Sample 2-2 6.0 5 900 850/500 29.7 Sample 2-3 4.0 5 900 850/500 30.2 Sample 2-4 2.5 5 900 850/500 30.9 Sample 2-5 1.0 5 900 850/500 31.6

Example 3

The results are shown in Table 3, except that Tb-H was used instead of Dy-H as the heavy rare earth compound in Example 1. The results are shown in Table 3. < tb > < TABLE > The results are similar to those of Dy-H.

division Medium rare earth particle size
(탆) Slurry aging time
(Work) Diffusion / heat treatment conditions Coercivity
Hcj
(kOe) Diffusion temperature
(° C) Heat treatment temperature
(° C) Comparison 1-1 × × - - 22.0 Comparison 3-2 8.5 0 900 850/500 26.1 Sample 3-1 8.5 0.1 900 850/500 28.5 Sample 3-2 8.5 One 900 850/500 30.7 Sample 3-3 8.5 2 900 850/500 31.4 Sample 3-4 8.5 5 900 850/500 32.0 Sample 3-5 8.5 10 900 850/500 32.0

Example 4

The results are shown in Table 4, except that Tb-H was used instead of Dy-H as the heavy rare earth compound in Example 2. Table 4 shows the results. The results are similar to those of Dy-H.

division Medium rare earth particle size
(탆) Slurry aging time
(Work) Diffusion / heat treatment conditions Coercivity
Hcj
(kOe) Diffusion temperature
(° C) Heat treatment temperature
(° C) Comparison 1-1 × × - - 22.0 Sample 4-1 8.5 5 900 850/500 32.0 Sample 4-2 6.0 5 900 850/500 32.7 Sample 4-3 4.0 5 900 850/500 33.3 Sample 4-4 2.5 5 900 850/500 33.8 Sample 4-5 1.0 5 900 850/500 34.5

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereby. something to do. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (9)

Preparing a rare-earth magnet sintered body containing R, Fe and B as constituent components, wherein R is selected from rare earth elements including Y and Sc;
Aging the heavy rare earth hydrogen compound in an organic solvent within a range of 10 to 50 DEG C for 1 to 10 days;
Wet-coating the surface of the sintered body with the aged heavy rare-earth hydrogen compound;
And a step of subjecting the coating material to heat treatment and grain boundary diffusion after the wet coating step.
The method according to claim 1,
Wherein the amount of the heavy rare earth hydrogen compound applied to the rare earth magnet sintered body is in the range of 0.1 to 5 wt%.
The method according to claim 1,
Wherein at least one of Dy-H and Tb-H is selectively contained in the heavy rare earth hydrogen compound.
The method according to claim 1,
Wherein the organic solvent comprises an alcohol.
delete The method according to claim 1,
Wherein the heavy rare earth metal compound has an average particle diameter in the range of 0.5 to 8.5 mu m.
The method according to claim 1,
Wherein the wet coating is performed by applying a slurry with an organic solvent used in aging.
The method according to claim 1,
Wherein the temperature of the grain boundary diffusion step is in the range of 600 to 1000 占 폚.
The method according to claim 1,
Further comprising the step of heat-treating after the intergranular diffusion step within a range of 500 ° C to 900 ° C to remove stress.