JP2002285208A - Method for preparing rare earth alloy powder material, and method for manufacturing rare earth alloy sintered compact using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a rare earth alloy powder material by which formation of oxide film on the surface of rare earth alloy powder can be suppressed and excellent lubricity can be produced and also to provide a method for manufacturing a rare earth alloy sintered compact using it. SOLUTION: The method comprises steps of preparing ground powder of rare earth alloy and pulverizing the ground powder in the presence of a solid lubricant having sublimation property at ordinary pressure to prepare the powder material substantially constituted of fine powder of the rare earth alloy whose surface is coated with the lubricant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an R--Fe--B sintered magnet, a method for preparing an alloy powder material as a raw material used for producing an R--Fe--B sintered magnet, and a method for storing the same. About.

[0002]

2. Description of the Related Art Rare earth alloy sintered magnets (permanent magnets)
Generally, it is manufactured by pressing a rare earth alloy powder, sintering the obtained powder compact, and subjecting it to aging treatment. At present, two types of samarium / cobalt magnets and neodymium / iron / boron magnets are widely used in various fields. Among them, neodymium-iron-boron magnets (hereinafter referred to as
It is called "R-Fe-B magnet". R is a rare earth element containing Y, Fe is iron, and B is boron. ) Shows the highest maximum magnetic energy product among various magnets and is relatively inexpensive, so that it is actively employed in various electronic devices.

[0003] R-Fe-B sintered magnets are mainly composed of R ₂ Fe.
_It is composed of a main phase composed of a tetragonal compound of ₁₄ B, an R-rich phase composed of Nd and the like, and a B-rich phase. In addition,
A part of Fe may be substituted with a transition metal such as Co or Ni, and a part of boron (B) may be substituted with carbon (C). R-Fe-B based sintered magnets to which the present invention is suitably applied are described, for example, in U.S. Pat. No. 4,770,723 and U.S. Pat. No. 4,792,368.

[0004] Ingot casting has conventionally been used to produce such an R-Fe-B alloy as a magnet. According to a general ingot casting method, a rare earth metal, an electrolytic iron, and a ferroboron alloy, which are starting materials, are subjected to high-frequency melting, and the obtained molten metal is cooled relatively slowly in a mold to produce an alloy ingot.

In recent years, molten alloys have been rolled in single rolls, twin rolls,
By contacting the rotating disk, or the inner surface of the rotating cylindrical mold, etc., it cools relatively quickly, and from the molten alloy,
A quenching method typified by a strip casting method or a centrifugal casting method for producing a solidified alloy (hereinafter referred to as “alloy flake”) thinner than an ingot has been attracting attention. The thickness of the alloy piece produced by such a quenching method is generally in the range of about 0.03 mm or more and about 10 mm or less.
According to the quenching method, the molten alloy begins to solidify from the surface in contact with the chill roll (roll contact surface), and crystals grow columnar from the roll contact surface in the thickness direction. As a result, the quenched alloy produced by the strip casting method or the like has an R ₂ Fe ₁₄ B crystal having a minor axis size of about 0.1 μm to about 100 μm and a major axis size of about 5 μm to about 500 μm. It has a structure containing a phase and an R-rich phase dispersed and present at the grain boundaries of the R ₂ Fe ₁₄ B crystal phase. The R-rich phase is a non-magnetic phase in which the concentration of the rare earth element R is relatively high, and its thickness (corresponding to the width of the grain boundary) is about 1
0 μm or less.

[0006] The quenched alloy is an alloy (ingot alloy) produced by a conventional ingot casting method (die casting method).
Since the cooling is performed in a relatively short time (cooling rate: 10 ² ° C / sec or more and 10 ⁴ ° C / sec or less), the structure is refined and the crystal grain size is small. ing. Further, since the area of the grain boundary is large and the R-rich phase is widely spread in the grain boundary, there is an advantage that the dispersibility of the R-rich phase is excellent. Because of these characteristics, a magnet having excellent magnetic properties can be manufactured by using a quenched alloy.

Also, the Ca reduction method (or reduction diffusion method)
A method called is also known. The method includes the following steps. First, a mixed powder containing at least one of rare earth oxides, iron powder and pure boron powder, and at least one of ferroboron powder and boron oxide at a predetermined ratio, or an alloy powder of the above constituent elements Alternatively, mixed calcium (C)
a) and calcium chloride (CaCl) are mixed and subjected to a reduction diffusion treatment under an inert gas atmosphere. By slurrying the obtained reaction product and treating it with water,
An R-Fe-B based alloy solid is obtained.

In the present specification, a solid alloy lump is referred to as an “alloy lump”, and a molten metal such as an alloy ingot obtained by a conventional ingot casting method and an alloy flake obtained by a rapid cooling method such as a strip casting method is cooled. In addition to the solidified alloy obtained as a result, various types of solid alloys such as a solid alloy obtained by a Ca reduction method are included.

The alloy powder to be subjected to press molding is obtained by crushing these alloy lumps by, for example, a hydrogen absorbing method and / or various mechanical crushing methods (for example, using a disk mill), and obtaining a coarse powder ( For example, the average particle size is 10 μm to 50 μm.
0 μm) by, for example, fine pulverization by a dry pulverization method using a jet mill.

[0010] The average particle size of the R-Fe-B-based alloy powder to be subjected to press molding is 1 μm to 1 μm from the viewpoint of magnetic properties.
It is preferably in the range of 0 μm. The “average particle size” of the powder herein refers to the mass median diameter (MMD) unless otherwise specified.

However, in general, rare earth alloy powders are easily oxidized, and there is a risk of heat generation or even ignition. Among them, in particular, alloy powder produced by a quenching method represented by a strip cast alloy is particularly easily oxidized. The surface of the quenched alloy powder particles has an easily oxidized R
It is considered that the risk is particularly high because a rich phase is likely to appear.

In order to avoid this problem, for example, a method of forming a thin oxide film on the surface of rare earth alloy powder is disclosed in Japanese Patent Publication No. 6-6728 (applicant: Sumitomo Special Metals Co., Ltd., filing date: 1986). July 24).

On the other hand, when the powder having the small average particle size is used, there is a problem that fluidity and press moldability (including cavity filling property and compressibility) are poor and productivity is poor.

As a method for solving this problem, it has been studied to cover the surface of the alloy powder particles with a lubricant.

For example, in the specification of Japanese Patent Application Laid-Open No. 08-111308 and the corresponding US Pat. No. 5,666,635 (assignee: Sumitomo Special Metals Co., Ltd.), the average particle size is 10 μm.
A lubricant obtained by liquefying at least one kind of fatty acid ester is added to a coarse powder of an R-Fe-B-based alloy having a thickness of about 500 µm.
After adding and mixing 02% by mass to 5.0% by mass, the mixture was subjected to jet mill pulverization using an inert gas to obtain an average particle size of 1.5 μm
A technique for producing a fine powder of μm is disclosed.

Further, Japanese Patent Publication No. 7-098962 discloses that
Although the use of solid paraffin or camphor as a lubricant is disclosed, the effect of suppressing the oxidation of the alloy is low because the lubricant is added after the alloy is finely pulverized. Further, the above publication describes that it is preferable to mix solid paraffin and camphor in a wet manner in order to suppress the oxidation of the alloy.

Further, Japanese Patent No. 2915560 discloses that
As a method of coating the powder surface with a lubricant without using an organic solvent, after adding and mixing a higher fatty acid or the like as a lubricant in a dry manner to a coarse powder of an R-Fe-B-based alloy, A method of milling is disclosed.

[0018]

It is not preferable to form an oxide film as described in Japanese Patent Publication No. 6-6728, since the magnetic characteristics are deteriorated. In particular, there is a problem that it is difficult to manufacture a sintered magnet used for an application requiring a high coercive force, such as a permanent magnet for a motor.

On the other hand, although the method using the above-mentioned lubricant can improve the fluidity and the molding, the effect of preventing the rare earth alloy powder from being oxidized is not sufficient. As described in Japanese Patent Publication No. 6-6728, it is necessary to form an oxide film, and it is difficult to solve the above problem.

The present invention has been made in view of the above points, and a main object of the present invention is to provide a method of manufacturing a rare earth alloy powder material which suppresses formation of an oxide film and has excellent fluidity. An object of the present invention is to provide a method for producing a rare earth alloy sintered body using the same.

[0021]

According to the present invention, there is provided a method for preparing a rare earth alloy powder material comprising the steps of (a) preparing a coarsely pulverized powder of a rare earth alloy, and (b) solid lubricant having sublimability at room temperature. Preparing a powder material substantially consisting of the rare earth alloy fine powder, the surface of which is covered by the lubricant, by finely pulverizing the coarsely pulverized powder in the presence thereof. This achieves the above object.

In the present specification, the term "rare earth alloy powder" is used in contrast to the term "rare earth alloy powder" consisting essentially of a powder of a rare earth alloy (which may include an oxide layer on the surface).
In addition, a powder material containing a lubricant and subjected to press molding is called a “rare earth alloy powder material” and is distinguished.

The rare earth alloy may be an R—Fe—B based alloy.

Step (b) is preferably carried out in an inert gas atmosphere having an oxygen gas content of 200 ppm or less. Step (b) can be performed using a jet mill.

The oxygen content of the fine powder is 3000 pp
m or less, more preferably 2000 ppm or less.

The lubricant preferably comprises an organic molecule having a terminal CH ₃ .

The step (a) may include a step of preparing an alloy lump of the rare earth alloy and a step of coarsely pulverizing the alloy lump by a hydrogen storage method.

[0028] The alloy ingot may be an alloy flake produced by a quenching method.

The average particle size of the fine powder of the rare earth alloy is preferably in the range of 2 μm to 10 μm.

Preferably, after the step (b), a step of adding at least one of methyl caproate and methyl caprylate to the rare earth alloy powder material and mixing the same is further included.

The method for producing a rare earth alloy sintered body according to the present invention comprises the steps of: preparing a rare earth alloy powder material prepared by any of the above methods; and (c) press-forming the powder material. And (d) a step of obtaining a sintered body by sintering the molded body, whereby the object is achieved.

The method for producing a rare earth sintered magnet according to the present invention includes a step of preparing a rare earth alloy sintered body produced by the above method and a step of magnetizing the rare earth alloy sintered body.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a rare earth alloy sintered body according to an embodiment of the present invention will be described below. In the following description of the embodiments, in particular, the features of the present invention will be described with an example of a method of manufacturing a sintered magnet using an R-Fe-B-based alloy powder that is more easily oxidized than a samarium-cobalt-based alloy powder. However, the present invention is not limited to this, and can be applied to a method for manufacturing a samarium-cobalt-based alloy sintered body.

The method for producing an R—Fe—B alloy sintered body according to the present embodiment includes (a) a step of preparing a coarsely pulverized powder of an R—Fe—B alloy, and (b) sublimation at room temperature. In the presence of a solid lubricant having, by finely pulverizing the coarsely pulverized powder, preparing a powder material substantially composed of fine powder of alloy whose surface is covered by the lubricant,
(C) a step of obtaining a compact by pressing the powder material to obtain a compact; and (d) a step of obtaining a sintered compact by sintering the compact. At any point after this, a sintered magnet is obtained by magnetizing the rare earth alloy sintered body.

The coarsely pulverized powder is finely pulverized in the presence of a solid lubricant having sublimability at room temperature, so that a gaseous lubricant produced by sublimation from the solid lubricant is produced by the pulverization. Adheres to highly active surfaces. As a result, oxidation of the surface of the alloy fine powder is suppressed, and fluidity and moldability are improved. Here, “having sublimability” means having a vapor pressure of 1.00 Pa or more at 25 ° C.

Accordingly, a stable alloy powder material can be obtained without actively forming an oxide film on the surface of the alloy fine powder as described in Japanese Patent Publication No. 6-6728. That is, the content of oxygen gas is 200 ppm
Even if the coarse pulverization is performed in the following inert gas (including a rare gas and a nitrogen gas) atmosphere, oxidation of the alloy fine powder is suppressed. Further, since all of the steps of adding / mixing the lubricant and finely pulverizing can be performed by a dry method, the manufacturing process can be simplified. These steps can be performed using a jet mill.

As a solid lubricant having sublimability at room temperature, it is particularly preferable to use a lubricant comprising an organic molecule having CH ₃ at a terminal. CH _{3 at the} molecular end has a high affinity for the surface of the rare-earth alloy, is quickly attached to the active surface generated by the fine pulverization, and has a high effect of suppressing oxidation. Note that CH _{3 at} the molecular end may be included in an alkyl group such as a methyl group or an ethyl group, or an alkoxy group such as a methoxy group or an ethoxy group. Also,
The vapor pressure at room temperature (25 ° C.) is preferably 1 Pa or more.

The amount of the solid lubricant having sublimability is from 0.01% by mass to 0.1% by mass based on the mass of the rare earth alloy powder.
Preferably it is in the range of 5% by mass. If the amount is less than 0.01% by mass, the surface of the fine powder cannot be sufficiently coated, and the effect of suppressing oxidation may not be sufficiently exhibited. Further, when it is more than 0.5% by mass,
It may remain in the sintered body and deteriorate magnetic properties.
Other solid lubricants can be used together with the sublimable solid lubricant. At this time, the amount of the solid lubricant having sublimability is preferably 50% by mass or more of the total amount of the lubricant. In addition, it is preferable that the total of all the lubricants does not exceed 0.5% by mass even when the lubricant is further added later. As the non-sublimable solid lubricant used in combination with the sublimable solid lubricant, lead stearate, copper stearate, lithium stearate and stearic acid can be suitably used.

The production method of the present invention is effective in producing a magnet having a high coercive force and has an oxygen content of 300.
It is effective when a fine powder of 0 ppm or less, particularly 2000 ppm or less is used. For example, the above-mentioned Tokuhei 6-672
No. 8 according to the method described in JP-A No. 8
When pulverized by a jet mill using nitrogen gas mixed with oxygen gas, the acid content in the fine powder is 5000 ppm to 6 ppm.
000 ppm, and the magnetic properties deteriorate. For example, as described above, when the pulverization step is performed in an inert gas atmosphere having an oxygen gas content of 200 ppm or less, a fine powder having an oxygen content of 3000 ppm or less can be obtained.

Further, when the coarse powder of the R—Fe—B alloy is obtained by coarsely pulverizing an alloy lump by the hydrogen absorbing method, an easily oxidized R-rich phase is formed on the surface of the coarse powder. In many cases, the effect of the present invention is remarkable. Furthermore, when the R-Fe-B-based alloy ingot is an alloy flake produced by a quenching method represented by a strip casting method, an R-rich phase often appears on the surface of the coarse powder. As the average particle size of the coarse powder,
It is preferably in the range of 50 μm to 1 mm,
More preferably, it is in the range of 0 μm to 800 μm.

The average particle size of the fine powder obtained by finely pulverizing the coarse powder in the presence of the lubricant gas generated by sublimation of the solid lubricant is 2 μm from the viewpoint of magnetic properties and moldability. It is preferably in the range of 10 to 10 μm. BET specific surface area of the fine powder is in the range of about 0.45 m ² / g to about 0.55 m ² / g.

A lubricant may be further added to the obtained powder material. It is preferable to use either or both of methyl caproate and methyl caprylate as the lubricant to be added later. For example, the lubricant contains 2 to 20% by mass of at least one of methyl caproate and methyl caprylate as a main component, and a saturated fatty acid having 20 to 24 carbon atoms as an additional component (for example, arachidic acid, behenic acid, lignoceric acid). ) At least one of 0.005
It is preferable to use a hydrocarbon-based solvent (e.g., normal paraffin, isoparaffin, cycloparaffin) having a boiling point of 40 to 200 ° C with a boiling point of 0.5 to 0.5% by mass. Methyl caproate and methyl caprylate have excellent effects of improving fluidity and compressibility during molding.

The obtained powder material is pressed. Press molding of the alloy powder material, for example, using an electric press,
While being oriented in a magnetic field of about 0.8MA / m~1.3MA / m, when compression molded at a pressure of ^{0.5ton / cm 2 ~1.0ton / cm 2} , 3.9g / cm3~4.6g / C
A compact having a compact density of m ³ can be obtained.

The thus obtained molded body is sintered at a temperature of, for example, about 1000 ° C. to about 1180 ° C. for about 1 to 2 hours. The obtained sintered body is, for example, about 450 ° C. to about 80 ° C.
By aging at a temperature of 0 ° C. for about 1 to 8 hours, an R—Fe—B based sintered magnet is obtained. In addition, in order to reduce the amount of carbon contained in the sintered magnet and improve the magnetic characteristics, a step of heating and removing (removing) the lubricant covering the surface of the alloy powder before the sintering step is added. Is also good. The heat removal step is performed, for example, at a temperature of about 200 ° C. to 600 ° C. under a pressure of about 2 Pa for about 3 to about 6 hours.

According to the present embodiment, a method for producing an R-Fe-B-based alloy powder in which the formation of an oxide film is suppressed and which has excellent fluidity, and an R-Fe-B-based alloy sintered body using the same. Is provided.

[0046]

EXAMPLES Hereinafter, the method for producing an R-Fe-B based sintered magnet of the present invention will be described with reference to examples, but the present invention is not limited to the following examples.

Nd: 30.8% by mass, Pr: 3.6% by mass, Dy: 0.8% by mass, B: 1.0% by mass, Co:
0.9% by mass, Al: 0.23% by mass, Cu: 0.10.
An alloy flake having a composition consisting of mass%, balance Fe and unavoidable impurities was produced by a strip casting method. The thickness of the alloy flake was about 0.2 mm to about 0.4 mm and the size was about 2 to 10 mm.

This alloy flake was pulverized by a hydrogen storage method to obtain an alloy coarse powder. The hydrogen storage method is
It can be performed in a known manner. For example, Japanese Patent Application No. 2000-
The method described in 198508 can be used. The average particle size of the obtained coarse powder was 100 to 800 μm. The amount of oxygen contained in this coarse powder is about 1200 pp
m.

A predetermined amount of a lubricant shown in Table 1 below was added to the obtained coarse powder, and the mixture was finely pulverized using a jet mill shown in FIG. Jet mill pulverization was performed in a nitrogen gas atmosphere having an oxygen gas content of 200 ppm or less and a purity of 99.5% or more.

First, the pulverizing step using the jet mill device 10 will be described with reference to FIG.

The jet mill pulverizing device 10 supplies a raw material, a pulverizer 14 for supplying the coarse powder, a pulverizer 14 for pulverizing the coarse powder supplied from the raw material input unit 12, and a classifier for the pulverized powder. The apparatus includes a cyclone classifier 16 and a collection tank 18 for collecting fine powder having a predetermined particle size classified by the cyclone classifier 16.

The raw material input device 12 includes a raw material tank 20 for storing coarse powder, a motor 22 for controlling the amount of coarse powder supplied from the raw material tank 20, and a spiral feeder (screw feeder) connected to the motor 22. ) 24.

The crusher 14 has a vertically long, substantially cylindrical crusher main body 26, and a lower part of the crusher main body 26 is provided with a nozzle for ejecting an inert gas (for example, nitrogen gas) at a high speed. Are provided. A raw material input pipe 30 for inputting coarse powder into the crusher main body 26 is connected to a side portion of the crusher main body 26.

The raw material input pipe 30 is provided with a valve 32 for temporarily holding the supplied coarse powder and confining the pressure inside the crusher 14. The valve 32 includes a pair of an upper valve 32a and a lower valve 32b. And The feeder 24 and the raw material input pipe 30 are a flexible pipe 3
4 are connected.

The crusher 14 includes a classification rotor 36 provided inside and above the crusher body 26, a motor 38 provided above and outside the crusher body 26, and a connection provided above the crusher body 26. And a pipe 40. Motor 3
Reference numeral 8 drives the classification rotor 36, and the connection pipe 40 discharges the fine powder classified by the classification rotor 36 to the outside of the crusher 14.

The pulverizer 14 has a plurality of legs 4 serving as support portions.
2 is provided. A base 44 is disposed near the outer periphery of the crusher 14, and a weight detector 46 such as a load cell is provided between the leg 42 of the crusher 14 and the base 44. Based on the output from the weight detector 46, the control unit 48 controls the number of revolutions of the motor 22, and thereby can control the amount of the coarse powder to be charged.

The cyclone classifier 16 comprises a classifier body 64
An exhaust pipe 66 is inserted into the classifier main body 64 from above. On the side of the classifier body 64,
Inlet 6 for introducing the fine powder classified by the classification rotor 36
8 are provided, and the inlet 68 is connected to the connection pipe 40 by a flexible pipe 70. An outlet 72 is provided at the lower part of the classifier main body 64,
The desired fine powder collection tank 18 is connected to the outlet 72.

The flexible pipes 34 and 70 may be made of resin, rubber or the like, or may be made of a highly rigid material in a bellows shape or a coil shape so as to have flexibility. preferable. Such flexible pipes 34 and 7
When 0 is used, a change in weight of the raw material tank 20, the feeder 24, the classifier main body 64, and the collection tank 18 is not transmitted to the leg 42 of the crusher 14. Therefore, if the weight is detected by the weight detector 46 provided on the leg 42, the crusher 1
4 can accurately detect the weight of the coarse powder and the amount of change in the coarse powder, and can accurately control the amount of the coarse powder supplied into the crusher 14.

Next, the fine pulverization process by the jet mill pulverizer 10 will be described.

First, a sublimable solid lubricant (including other solid lubricants if necessary: all in powder form) is added to the coarse powder of the alloy obtained as described above using, for example, a rocking mixer. Mix.

The obtained coarse powder is put into the raw material tank 20. The coarse powder in the raw material tank 20 is supplied to the crusher 14 by the supply device 24. At this time, the supply amount of the coarse powder can be adjusted by controlling the rotation speed of the motor 22. The coarse powder supplied from the supply device 24 is temporarily stopped by the valve 32. Here, the pair of upper valve 32a and lower valve 32b alternately open and close. That is, when the upper valve 32a is open, the lower valve 32b is closed, and when the upper valve 32a is closed, the lower valve 32b is open. By alternately opening and closing the pair of valves 32a and 32b in this manner, the pressure in the crusher 14 can be prevented from flowing to the raw material input device 12 side. As a result, the coarse powder is supplied between the pair of upper valve 32a and lower valve 32b when the upper valve 32a is opened. Then, when the lower valve 32b is opened next time, it is guided to the raw material charging pipe 30 and introduced into the crusher 14. The valve 30 is driven at a high speed by a sequence circuit (not shown) different from the control circuit 48, and the coarse powder is continuously supplied into the crusher 14.

The coarse powder introduced into the crusher 14 is crushed by a high-speed injection of an inert gas from a nozzle port 28.
4 and revolves with the high-speed airflow in the device. Then, the coarse powder is finely crushed by mutual collision. In this process, the sublimable solid lubricant is sublimated by the heat generated during the grinding (grinding), and instantly becomes a fresh surface of the alloy fine powder (a newly generated highly active surface). ).

The powder particles thus finely pulverized and having the lubricant attached to the surface are ridden by an ascending airflow to classify the rotor 3.
6 and classified by the classification rotor 36, and the coarse particles are again pulverized. On the other hand, particles pulverized to a predetermined particle size or less are connected pipe 40, flexible pipe 70
Through the inlet 68 into the classifier body 64 of the cyclone classifier 16. In the classifier main body 16, relatively large particles having a predetermined particle size or more are accumulated in a recovery tank 18 provided at a lower portion. Then, it is collected by the bag filter 82. The inert gas passes through the bag filter 82, is compressed by the compressor 84, and is temporarily stored in the tank 86.
8 is injected into the crusher 14 at high speed. By circulating and using the inert gas in this manner, the consumption of the inert gas can be reduced.

Further, in the present invention, since the solid lubricant is used at room temperature, the bag filter 82 can be prevented from being clogged, so that the above-mentioned circulation type pulverizing apparatus can be constituted. become. The melting point of the solid lubricant added in the pulverization step is preferably higher than 100 ° C, and more preferably 150 ° C or higher.

As described above, the ultrafine powder is removed through the exhaust pipe 66, whereby the number ratio of the ultrafine powder (particle size 1 μm or less) in the powder collected in the collection tank 18 is adjusted to 10% or less. In this manner, when the ultrafine powder containing a large amount of R is removed, there is an advantage that the amount of R in the sintered body consumed for bonding with oxygen can be reduced and the magnetic properties can be improved. Conversely, if the proportion of the ultrafine powder containing a large amount of R is too large, the amount of oxygen contained in the fine powder can be reduced by 3000 p even if the oxygen gas content in the inert gas is reduced.
pm or less.

By the above-mentioned fine pulverizing step, for example, a fine powder having an average particle size of about 4 μm and the number of ultrafine powders of 1 μm or less being 10% or less of the whole powder can be obtained. The average particle size of the fine powder used for manufacturing the sintered magnet is preferably 2 μm or more and 10 μm or less.
According to the present invention, the surface of the fine powder is covered with a lubricant, and oxidation is suppressed.

Thereafter, when further adding a lubricant, the fine powder may be filled in a rocking mixer, and for example, a lubricant of 0.3% by mass may be added and mixed.

The obtained R-Fe-B-based alloy powder material was compression-molded at a pressure of 230 MPa using an electric press while orienting in a magnetic field of about 0.8 MA / m, and the width was 10 mm.
A molded article having a height of 15 mm and a length of 20 mm was obtained.

The obtained molded product was placed in an Ar atmosphere at about 108
Sinter at 0 ° C for about 1 hour, then in Ar atmosphere for about 60 hours.
Aging treatment was performed at 0 ° C. for about 1 hour to obtain a sintered magnet.

The lubricants shown in Table 1 below were added to the coarse powder in Table 1.
Add before milling with the amount shown in (Prior addition in Table 1)
Then, while the coarse powder was finely pulverized using the above-mentioned jet mill pulverizer 10, a lubricant was applied to the surface thereof. In Example 4, a lubricant was further added to the fine powder coated with the lubricant obtained in the above-mentioned fine pulverization step (post-addition in Table 1).

The obtained alloy powder materials according to Examples 1 to 4 and Comparative Example were left in an atmosphere at 30 ° C. and a relative humidity of 90%, the highest temperature was measured, and the temperature rise was shown in Table 1. . The degree of this temperature rise is an indicator of the degree of the oxidation reaction of the alloy. That is, when the surface of the alloy powder is not coated with the lubricant, the oxidation reaction proceeds, and the temperature rises.

The alloy powder materials of Examples 1 to 4 were formed into compacts in the atmosphere. On the other hand, with respect to the comparative example, a compact was produced as described above without exposing the alloy powder material to the atmosphere. The obtained molded bodies were sintered and magnetized to obtain sintered magnets. Table 1 also shows the results of the magnetic properties of the obtained sintered magnet and the amount of residual carbon in the sintered body.

[0073]

[Table 1]

As is clear from the results shown in Table 1, Example 1 (0.1% by mass of camphor was added in advance) and Example 2
Example 3 (0.1% by mass of ethyl vanillin was added beforehand), Example 3
(0.05% by mass of ethyl vanillin and 0.1% of lead stearate).
Alloy powder material of Example 4 (0.2% by mass of ethyl vanillin was pre-added, and methyl caproate and isoparaffin were mixed at a ratio of 15:85, and the mixture was post-added). The temperature rise when left in an atmosphere at 90 ° C. and a relative humidity of 90% is slight, and it can be seen that in these powder materials, the surface of the alloy powder is stably coated with the respective lubricant. On the other hand, in Comparative Example (0.1% by mass of lead stearate was added in advance), 30
When left in an atmosphere at a temperature of 90 ° C. and a relative humidity of 90%, the oxidation reaction proceeded violently, leading to ignition.

The magnetic properties (residual magnetic flux density B
From the results of (r, coercive force Hcj and maximum energy product) and the amount of residual carbon, it can be seen that the characteristics of Examples 1 to 4 are not inferior to those of the comparative example and have good characteristics. Moreover, despite the fact that the sintered bodies of Examples 1 to 4 were molded in the atmosphere, the oxygen content was as low as 2500 ppm or less.

Further, the fluidity and formability of the alloy powder materials of Examples 1 to 4 were good, and during the press forming process,
The occurrence of chipping and cracking was small.

[0077]

According to the present invention, the formation of an oxide film on the surface of a rare earth alloy powder is suppressed, and a method of manufacturing a rare earth alloy powder material having excellent fluidity and rare earth alloy firing using the same are provided. Provided is a method for manufacturing a body.

The present invention is particularly effective when producing a sintered magnet using an R-Fe-B-based alloy powder which is easily oxidized and produced by a quenching method.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a jet mill pulverizing apparatus 10 suitably used for performing a fine pulverizing step in the present invention.

[Brief description of reference numerals]

 DESCRIPTION OF SYMBOLS 10 Jet mill crusher 12 Material input machine 14 Crusher 16 Cyclone classifier 18 Recovery tank 20 Material tank 22, 38 Motor 24 Feeder (screw feeder) 26 Crusher main body 28 Nozzle port 30 Material input pipe 32a, 32b

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K017 AA04 BA06 BB12 CA07 DA04 EA03 EA09 EK07 4K018 AA27 BA18 BB04 BC12 BC29 BD01 KA45 5E040 AA04 BD01 CA01 HB03 HB17 5E062 CC05 CD04 CE04 CG02 CG03

Claims (12)

[Claims] (A) preparing a coarsely ground powder of a rare earth alloy; and (b) finely pulverizing the coarsely ground powder in the presence of a solid lubricant having sublimability at room temperature. Preparing a powder material substantially composed of fine powder of the rare earth alloy whose surface is covered with the lubricant. 2. The method for preparing a rare earth alloy powder material according to claim 1, wherein the rare earth alloy is an R—Fe—B based alloy. 3. The method according to claim 1, wherein the step (b) comprises:
The method for preparing a rare earth alloy powder material according to claim 1 or 2, wherein the method is performed in an inert gas atmosphere of 0 ppm or less. 4. The method for preparing a rare earth alloy powder material according to claim 3, wherein step (b) is performed using a jet mill. 5. The oxygen content of the fine powder is 3000 p
The method for preparing a rare earth alloy powder material according to any one of claims 1 to 4, which is not more than pm. 6. The method for preparing a rare earth alloy powder material according to claim 1, wherein the lubricant comprises an organic molecule having CH ₃ at a terminal. 7. The method according to claim 1, wherein the step (a) includes a step of preparing an alloy lump of the rare earth alloy and a step of coarsely pulverizing the alloy lump by a hydrogen storage method. Preparation method of rare earth alloy powder material. 8. The method for preparing a rare earth alloy powder material according to claim 7, wherein the alloy ingot is an alloy flake produced by a quenching method. 9. The fine powder of the rare earth alloy has an average particle size in a range of 2 μm to 10 μm.
The method for preparing a rare earth alloy powder material according to any one of the above. 10. The method according to claim 1, further comprising, after the step (b), adding at least one of methyl caproate and methyl caprylate to the rare earth alloy powder material, followed by mixing. The method for preparing a rare earth alloy powder material according to any one of the above. 11. A step of preparing a rare earth alloy powder material prepared by the method according to any one of claims 1 to 10, and (c) a step of pressing the powder material to obtain a compact. (D) a step of obtaining a sintered body by sintering the molded body; and a method of producing a rare earth alloy sintered body. 12. A method for producing a rare earth sintered magnet, comprising: a step of preparing a rare earth alloy sintered body produced by the method of claim 11; and a step of magnetizing the rare earth alloy sintered body.