JP2001143950A - METHOD OF MANUFACTURING R-Fe-B SINTERED MAGNET, METHOD OF PREPARING ALLOY POWDER MATERIAL FOR R-Fe-B SINTERED MAGNET, AND METHOD OF PRESERVING THE MATERIAL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the productivity of an R-Fe-B sintered magnet by reducing the cracking, chipping, etc., of a molded article by improving the press- molderability, particularly, the compressibility of an alloy powder material used for forming the magnet. SOLUTION: A method of manufacturing R-Fe-B sintered magnet includes a step (a) of preparing a first-state alloy powder material which is prepared by giving a first quantity or more of lubricant to the surface of alloy powder for R-Fe-B sintered magnet, a step (b) of preparing a second-state alloy powder material prepared by reducing the quantity of the lubricant given to the first- state alloy powder material to a second quantity or smaller by volatilizing the lubricant, and a step (c) of forming a molded article by press-molding the second-state alloy powder material. The method also includes a step (d) of sintering the molded article.

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 a compact of the obtained powder, and subjecting to aging treatment. Currently, samarium-cobalt magnets and neodymium-
Two types of 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 magnetic energy product among various magnets and is relatively inexpensive, so that it is actively employed in various electronic devices. R
-Fe-B based rare earth magnet is composed mainly of a main phase consisting tetragonal compound of R ₂ Fe ₁₄ B, consisting of Nd, etc. R-rich phase and B-rich phase. Note that a part of Fe may be replaced with a transition metal such as Co or Ni. The R-Fe-B-based rare earth sintered magnet to which the present invention is suitably applied,
For example, it is described in U.S. Pat. No. 4,770,723 and U.S. Pat. No. 4,792,368.

[0003] In order to produce such a rare earth alloy as a magnet, an ingot casting method has been conventionally used in which a molten metal of a raw material alloy is put into a mold and cooled relatively slowly. The alloy ingot produced by the ingot casting method is pulverized through a known pulverizing process. The alloy powder thus produced is compression-molded by various powder presses, and then conveyed into a sintering chamber where it undergoes a sintering process.

[0004] In recent years, a single-roll, twin-roll,
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 attracted 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.

A 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.

In the present specification, the solidified alloy mass obtained by cooling the molten metal is referred to as "alloy mass", and is formed by a rapid cooling method such as an alloy ingot obtained by a conventional ingot casting method and a strip casting method. It includes various forms of solid alloys, such as the resulting alloy flakes. The alloy powder to be subjected to press molding is a coarse powder (for example, having an average particle size of 10 μm to 10 μm) obtained by grinding these alloy ingots using, for example, a hydrogenation grinding method and / or various mechanical grinding methods. (500 μm).

[0007] However, there is a problem that the alloy powder produced by the quenching method represented by the strip cast alloy is particularly easily oxidized. In general, rare earth alloy powders are easily oxidized, and there is a risk of heat generation and ignition. However, since the R-rich phase that is easily oxidized easily appears on the surface of the quenched alloy powder particles, the risk is particularly high. Can be

In order to avoid this problem, for example, a method of forming a thin oxide film on the surface of a rare earth alloy powder is disclosed in Japanese Patent Publication No. 6-6728 (applicant: Sumitomo Special Metals Co., Ltd., filing date: 1986). July 24). Also, this publication discloses that in order to obtain excellent magnetic properties,
The average particle size of the rare earth alloy powder used for press molding is
It is disclosed that it is preferably in the range of 1.5 μm to 5 μm. When the average particle size is smaller than 1.5 μm,
The ratio of the oxide becomes too large, leading to a decrease in magnetic properties,
If it is larger than 5 μm, magnetization reversal occurs easily,
It is not preferable because the holding power is reduced.

[0009] Further, in the specification of US Patent No. 5,666,635 (assignee: Sumitomo Special Metals Co., Ltd.), in order to improve the compressibility (press formability) of rare earth alloy powder,
0.02 wt% to 5.0 wt% of a lubricant obtained by liquefying at least one fatty acid ester is added to a coarse powder of an R-Fe-B based sintered magnet alloy having an average particle size of 10 µm to 500 µm.
A technique is disclosed in which after addition and mixing, jet mill pulverization using an inert gas is performed to produce fine powder having an average particle size of 1.5 μm to 5 μm.

[0010]

However, as a result of investigations made by the present inventors, even if the above-mentioned conventional technique is used, cracks or chipping of a compact of an alloy powder which is considered to be caused by poor compressibility during press molding. There is a problem that such is likely to occur. This problem is particularly remarkable when using a rare earth alloy powder having a relatively sharp particle size distribution in which the small particle side and the large particle side of the rare earth alloy powder are removed in order to obtain the above average particle diameter. Was.

The present invention has been made to solve the above problems, and a main object of the present invention is to provide an R—Fe—B
By improving the press formability, especially the compressibility, of the alloy powder material for the sintered magnet for R-Fe-B sintered magnets, it is possible to reduce cracks and chips in the compact and improve the productivity. An object of the present invention is to provide a production method and a method for preparing an alloy powder material for an R-Fe-B based sintered magnet.

[0012]

The present inventor has made various studies in view of the above-mentioned problems of the prior art, and as a result, after preparing an alloy powder material whose surface is coated with a rare earth alloy powder lubricant, In the meantime, the content of the lubricant contained in the alloy powder material fluctuates before press forming, and the resulting variation (and / or uniformity) of the lubricant content is related to the compressibility of the powder material. As a result, it has been thought that cracks or chips may be generated in the compact of the powder material.

[0013] Therefore, further investigation was made. Before press-forming the alloy powder whose surface was coated with a lubricant,
By volatilizing the lubricant contained in the alloy powder material to a predetermined amount or less, the compressibility can be further improved, and it has been found that the occurrence of cracking or chipping of the compact can be reduced, and the present invention Reached.

In the specification of the present application, a powder consisting of a rare earth alloy alone (including an oxide film formed by oxidizing the surface of the rare earth alloy powder) is referred to as a “rare earth alloy powder”. The rare earth alloy powder whose surface is covered with a lubricant is referred to as “rare earth alloy powder material”. The “rare earth alloy powder material” may contain an excess lubricant other than the surface of the rare earth alloy powder, and may further contain a binder (binder) in some cases.

The method for producing an R—Fe—B sintered magnet according to the present invention comprises the steps of: (a) applying a lubricant of at least a first amount to the surface of the alloy powder for the R—Fe—B sintered magnet; Preparing the obtained first-state alloy powder material; and (b) evaporating a portion of the lubricant of the first-state alloy powder material to reduce the amount of the lubricant to a second amount or less. Preparing a reduced second-state alloy powder material; (c) press-forming the second-state alloy powder material to form a compact; and (d) firing the compact. Tying.

In one embodiment, the step (a)
The method may include a step of pulverizing the coarse powder of the alloy while supplying the lubricant.

[0017] In another embodiment, the step (a) may include a step of mixing the alloy powder and the lubricant while supplying the lubricant to the alloy powder prepared in advance. Good.

It is preferable that the step (b) includes a step of flowing an inert gas into an airtight container containing the alloy powder material in the first state.

[0019] After the step (b), the method further includes a step of storing the alloy powder material in the second state in a state where an inert gas is flown in the container or another airtight container. Is also good.

The method may further include a step of sampling the alloy powder material in the second state stored in the container and performing a composition analysis, and thereafter, the step (c) may be performed. .

The average particle size of the alloy powder is 3 μm to 6 μm.
It is preferably within the range of m.

The specific surface area of the alloy powder determined by the BET method is preferably in the range of 0.45 to 0.55 m ² / g.

It is preferable that the first amount is 0.15 wt% or more of the weight of the alloy powder.

It is preferable that the second amount is 0.12 wt% or less of the weight of the alloy powder.

As the lubricant, a lubricant containing a fatty acid ester as a main component can be used.

In the step (a), the lubricant is
It may be applied to the surface of the alloy powder in a state diluted with a solvent. The lubricant diluted with the solvent may be supplied in a step of finely pulverizing the coarse powder of the alloy, or may be mixed with the alloy powder while supplying the alloy powder prepared in advance. It is preferable that the total of the solvent and the lubricant contained in the alloy powder material in the second state is 0.5 wt% or less of the weight of the alloy powder. As the solvent, a petroleum-based solvent can be used. Also in this case, a lubricant containing a fatty acid ester as a main component can be used as the lubricant.

In another aspect of the present invention, there is provided a method for preparing an alloy powder material for an R-Fe-B based sintered magnet, wherein a lubricant is provided on the surface of the alloy powder.

The method for preparing the alloy powder material according to the present invention comprises:
(A) On the surface of the alloy powder for the R-Fe-B based sintered magnet,
Preparing a first state alloy powder material to which a first amount or more of lubricant is applied; and (b) performing the lubrication by volatilizing a part of the lubricant of the first state alloy powder material. Preparing a second state alloy powder material in which the amount of the agent has been reduced to a second amount or less.

In one embodiment, the step (a)
Includes a step of mixing the alloy powder and the lubricant while supplying the lubricant to the alloy powder prepared in advance.

The step (b) preferably includes a step of flowing an inert gas into a hermetically sealed container containing the alloy powder material in the first state.

The average particle size of the alloy powder is 3 μm to 6 μm.
It is preferably within the range of m.

The specific surface area of the alloy powder by the BET method within the range of 0.45 to 0.55 m ² / g can be suitably used.

Preferably, the first amount is at least 0.15 wt% of the weight of the alloy powder.

It is preferable that the second amount is 0.12 wt% or less of the weight of the alloy powder.

As the lubricant, a lubricant containing a fatty acid ester as a main component can be used.

In the step (a), the lubricant is
It may be applied to the surface of the alloy powder in a state diluted with a solvent. The lubricant diluted with the solvent may be supplied in a step of finely pulverizing the coarse powder of the alloy, or may be mixed with the alloy powder while supplying the alloy powder prepared in advance. It is preferable that the total of the solvent and the lubricant contained in the alloy powder material in the second state is 0.5 wt% or less of the weight of the alloy powder. As the solvent, a petroleum-based solvent can be used. Also in this case, a lubricant containing a fatty acid ester as a main component can be used as the lubricant.

According to yet another aspect of the present invention, RF
A method for storing an alloy powder material for an e-B based sintered magnet is provided.

The method for storing the alloy powder material according to the present invention is as follows.
An alloy powder material in which a predetermined amount or less of a lubricant is applied to the surface of the alloy powder for the R-Fe-B based sintered magnet is stored in an airtight container with an inert gas flowing therethrough. .

The average particle size of the alloy powder is 3 μm to 6 μm.
It is preferably within the range of m.

The alloy powder having a specific surface area determined by the BET method within the range of 0.45 to 0.55 m ² / g can be suitably used.

It is preferable that the predetermined amount is 0.12% by weight or less of the weight of the alloy powder. As the lubricant, a fatty acid ester-based lubricant can be used.

The alloy powder material may contain the lubricant and the solvent, and in this case, the total of the lubricant and the solvent is preferably 0.5 wt% or less of the weight of the alloy powder. . As the solvent, a petroleum-based solvent can be used. Also in this case, a lubricant containing a fatty acid ester as a main component can be used as the lubricant.

[0043]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a method for producing an R—Fe—B based sintered magnet of the present invention will be described with reference to the drawings. The method for preparing and storing the alloy powder material for an R-Fe-B based sintered magnet according to the present invention is as follows.
Although it can be carried out independently of other steps in the method of manufacturing the B-based sintered magnet, it will be described as a part of the method of manufacturing the R-Fe-B-based sintered magnet for simplicity.

The method for producing an R—Fe—B based sintered magnet according to the embodiment of the present invention comprises the steps of: (a) applying a first amount or more of lubricant to the surface of the alloy powder for the R—Fe—B based sintered magnet; Preparing a first state alloy powder material to which an agent has been applied; and (b) evaporating a part of the lubricant of the first state alloy powder material to reduce the amount of the second lubricant. Preparing a second state alloy powder material reduced to an amount or less;
(C) forming a compact by press-molding the alloy powder material in the second state; and (d) sintering the compact.

That is, according to the present invention, an amount (first amount) of lubricant that is greater than or equal to an amount necessary to obtain predetermined press formability (compressibility and difficulty of occurrence of chipping or cracking) is provided. Prepared alloy powder material (first state) and volatilized excess lubricant to provide alloy powder material with required amount (less than or equal to second amount) of lubricant (second state) Get.

This is based on the finding that excellent press formability can be obtained when the amount of the lubricant is equal to or less than a predetermined amount (second amount), as will be shown later with specific data. That is, if the amount of the lubricant is more than the predetermined amount, the press formability is greatly reduced. However, since the predetermined amount is relatively small, it is difficult to uniformly and directly apply a predetermined amount of the lubricant to the surface of the alloy powder. Therefore, an alloy powder material (first state) to which an amount of lubricant (first amount) that can sufficiently coat the surface of the alloy powder sufficiently is prepared, and the lubricant is volatilized from this alloy powder material. By doing so, surplus lubricant is uniformly removed, and an alloy powder material in which the surface of the alloy powder is uniformly coated with a predetermined amount of lubricant is obtained. Since the volatility of the lubricant is uniform, the surplus lubricant can be uniformly removed.

Step (a) can be performed using a known method, for example, as follows.

First, an alloy powder to be subjected to press molding is, for example, an alloy ingot produced by a conventional ingot casting method or an alloy flake made by an alloy flake produced by a quenching method represented by a strip casting method. The coarse powder obtained by pulverization using a hydrogenation pulverization method and / or various mechanical pulverization methods (methods using a stamp mill device, a jaw crusher device, a brown mill device, etc.) is finely ground using a jet mill. Obtained by grinding (U.S. Pat. No. 5,666,635)
No.). At this time, the average particle size of the coarse powder is 10 μm or more.
The average particle size of the alloy powder finally subjected to press molding is preferably in the range of about 1 μm to 500 μm.
It is preferably in the range of about 10 μm, from about 3 μm to
More preferably, it is in the range of about 6 μm. The range of the average particle size is determined by the above-mentioned US Pat. No. 5,666,635.
Although it is slightly different from the description (1.5 μm to 5 μm), the above range has been confirmed to be preferable from the viewpoint of press moldability and magnetic properties by the study of the present inventors and other collaborators. . In particular, in order to ensure excellent compressibility, it is preferable that the average particle size is about 3 μm or more.

The application of the lubricant to the surface of the rare earth alloy powder may be performed by finely pulverizing the coarse alloy powder while supplying the lubricant. For example, US Pat.
As described in US Pat. No. 6,635, this can be done by adding a lubricant to the coarse powder and then milling it using a jet mill. The lubricant may be applied to the surface of the rare earth alloy powder by spraying the lubricant into a jet mill while finely pulverizing the alloy coarse powder.

Alternatively, the lubricant is applied to the surface of the rare earth alloy powder by mixing the alloy powder and the lubricant while supplying the lubricant to the previously prepared alloy powder (the finely pulverized powder). Can also be performed. In the method of adding and mixing a lubricant to an alloy powder having a predetermined average particle diameter (particle size distribution) prepared in advance, the total amount of the alloy powder is reduced due to the volatilization of a part of the added lubricant. It is preferable because the lubricant can be coated more uniformly, more quickly, and more reliably on the surface of the alloy powder without fear of being mixed with the lubricant. The lubricant may be added to and mixed with the alloy powder in the recovery tank after collecting the alloy powder in a recovery tank or the like of a jet mill, or may be added to the alloy powder after being transferred to another container. On the other hand, it may be added and mixed.

The lubricant is not particularly limited as long as at least a part thereof is volatilized in a later step, and examples thereof include a lubricant containing a fatty acid ester as a main component. As described below, it is particularly preferable that the lubricant is volatilized by flowing an inert gas,
Liquid lubricants that are volatile at room temperature are preferred. Specific examples of the fatty acid ester include methyl caproate, methyl caprylate, and methyl laurate.
In addition to the lubricant, other compounds such as a binder may be added.

The lubricant itself may be added and mixed singly. However, if the lubricant diluted with a solvent is added and mixed, the surface of the alloy powder can be uniformly coated with a relatively small amount of the lubricant. There is also an advantage that can be. In addition, there is an advantage that the surface of the alloy powder can be uniformly coated even in a solid state in which the lubricant itself cannot be uniformly mixed with the alloy powder. However, if the lubricant is in a solid state, it is difficult to volatilize the lubricant due to air flow. Therefore, it is preferable to use a liquid lubricant having volatility at room temperature. As the solvent, a petroleum solvent represented by isoparaffin, a naphthenic solvent, or the like can be used.

The first amount of the lubricant contained in the alloy powder material in the first state obtained in the step (a) is, of course, included in the alloy powder material in the second state which is finally subjected to press forming. More than the second amount of lubricant. Further, the first amount depends on a method used for applying a lubricant to the surface of the alloy powder (a surface treatment method such as a mixing method or a pulverizing method).
The amount is set such that the lubricant can be applied to almost all surfaces of the alloy powder particles. At this time, since the lubricant is provided in excess, the amount of the lubricant present varies depending on the location of the alloy powder, but the necessary minimum amount of the lubricant is provided on substantially all surfaces. I just want to. The minimum necessary amount of the lubricant is stably present on the surface of the alloy powder without being easily volatilized due to the interaction (physical adsorption or chemical adsorption) with the surface of the alloy powder. Therefore, once a sufficient amount of lubricant is applied to the surface of the alloy powder, in the subsequent volatilization step, the amount does not become less than the necessary minimum amount, and the amount of lubrication sufficient to obtain sufficient press formability is obtained. An alloy powder material in which the agent is applied to the surface of the alloy powder is obtained.

It is considered that the first amount and the second amount can be appropriately changed depending on the type of the alloy powder (for example, the average particle size and the specific surface area), but various types of R—Fe—B based sintered magnets can be used. Alloy powder (average particle size of about 2.8 to about 6.0 μm, B
Specific surface area by the ET method (about 0.45 m ² / g to about 0.5
As a result of studying about 5 m ² / g), the first amount is preferably in a range of about 0.15 wt% to about 5.0 wt% based on the rare earth alloy powder. When converted in terms of surface area, about 0.27 g / m ² to about 0.90 g / m ²
Is preferably within the range. The amount of lubricant added is about 0.
If the amount is less than 15 wt%, it becomes difficult to uniformly coat the surface of the alloy powder with the lubricant, and as a result, the press formability may eventually decrease. Further, when press-forming while applying a magnetic field, it becomes difficult to orient each particle of the alloy powder in the direction of the magnetic field, and there is a possibility that the magnetic properties of the finally obtained magnet may be deteriorated. If the added amount of the lubricant is more than about 5.0 wt%, the lubricant is added to the second
It takes a long time to evaporate to less than the amount, and the productivity decreases. Preferably, the first amount is not less than about 2 times and not more than about 4 times the second amount. In the present specification,
“Average particle size” means “mass median diamete
r: MMD) ".

Step (b) can be performed in various ways. For example, a method of flowing an inert gas into a container containing the alloy powder in the first state, a method of evacuating the container, a method of flying the alloy powder in the inert gas using a spray dryer or the like, A method of placing an alloy powder on a net and blowing up an inert gas from below may be used. Among these, a method of flowing an inert gas into a container containing the alloy powder is desirable in that the lubricant can be efficiently vaporized and that the method can be performed with a simple device. Of course, this container may be a container in which a lubricant is added to and mixed with the alloy powder, or may be a container in which the alloy powder to which the lubricant is added is transferred. It should be noted that the term “inert gas” as used herein includes not only inert gas (Ar, He, etc.) in a narrow sense but also nitrogen gas. Since inexpensive nitrogen gas can be suitably used,
In the following, description will be made with nitrogen gas.

For example, by supplying nitrogen gas from, for example, a nitrogen cylinder to an airtight container made of stainless steel or the like and allowing nitrogen gas to flow out from an exhaust port, air can be generated in the container. The volatilization rate can be adjusted by controlling the flow rate of the nitrogen gas. The flow rate of the nitrogen gas may be appropriately set according to the volume of the container, the amount of the alloy powder material, the amount of the lubricant to be volatilized, the speed of the volatilization, and the like.

Here, the airtight container means a container having airtightness such that air does not enter the container except from the inlet and outlet of the nitrogen gas. Since the inside of the container becomes a positive pressure by the nitrogen gas which can be supplied from the outside, not so high airtightness is required. It is also an advantage of using airflow that a relatively airtight container can be used.

In order to obtain good press formability (especially compressibility), according to the results of the study on the alloy powder described above, the amount of lubricant (the second amount) is about 0% with respect to the alloy powder. .12 wt% or less. When converted in terms of surface area, it is preferably about 0.27 g / m ² or less. Alternatively, dilute the lubricant with a solvent (about 4 times to about 20 times).
), It is preferable that the total of both is about 0.5 wt% or less based on the alloy powder. When this is converted in terms of surface area, it is preferably about 0.90 g / m ² or less.

The lubricant is supplied to the second container by the air in the container.
Can be stably stored in this container. For example, if the alloy powder material is stored in a highly airtight container, unless the airtightness is very high, the alloy powder will absorb oxygen in the atmosphere and the inside of the container will be in a depressurized state, which will further suction the atmosphere. A phenomenon occurs. When the alloy powder is oxidized, the magnetic properties are degraded, and even heat generation or ignition may occur. With the use of nitrogen gas flow, the alloy powder material can be stored in a relatively simple container in a state where it is shielded from the atmosphere. Since the lubricant does not need to be volatilized by the flow of the nitrogen gas, the flow rate of the nitrogen gas may be adjusted so that the atmosphere does not enter the container.

Normally, the composition of the alloy powder affects the magnetic properties. Therefore, the composition of the alloy powder is analyzed for product management. That is, after the composition analysis of the produced alloy powder material is completed, it is subjected to the press forming step. At least during this period (typically, day and night), the alloy powder material that is easily oxidized must be stably stored, and can be stored as it is by using a method of controlling the amount of lubricant using a flow of nitrogen gas. So convenient. By using the air flow, the alloy powder material can be stably stored for two weeks or more (in some cases, one month or more). In addition, when the place where the alloy powder material is manufactured and the place where the steps after the press forming step are executed are different, if there is only a simple airtight container and nitrogen cylinder, the alloy powder can be stored stably. Can be transported.

Steps (c) and (d) can be performed by a known method. These steps can be performed, for example, using the methods described in US Pat. No. 5,666,635.

The press forming of the alloy powder material is performed, for example, by using an electric press and orienting in a magnetic field of about 0.8 MA / m to 1.3 MA / m while applying 0.5 ton / cm ^{2 to} 1.0 ton.
3.9 g / c if compression molded at a pressure of ton / cm ²
A compact having a compact density of m ^{3 to} 4.6 g / cm 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 aged, for example, at a temperature of about 450 ° C. to about 800 ° C. for about 1 to 8 hours to obtain an R—Fe—B based sintered magnet. In addition, in order to reduce the amount of carbon contained in the sintered magnet and improve the magnetic properties, it is preferable to remove (remove) the lubricant covering the surface of the alloy powder by heating before the sintering step. The heat removal step is performed 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 manufacturing method of this embodiment, R-Fe
Since the alloy powder material for the -B based sintered magnet has excellent press formability (particularly compressibility), cracks and chipping of the formed body are reduced, and the R-Fe-B based sintered magnet Productivity can be improved.

[0064]

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 wt%, B: 1.0 wt%, D
y: 1.2 wt%, Al: 0.2 wt%, Co: 0.9
An alloy flake having a composition consisting of wt%, balance Fe and unavoidable impurities was produced by a strip casting method. This alloy flake was pulverized by a hydrogenation pulverization method to obtain an alloy coarse powder. This alloy coarse powder was finely pulverized in a nitrogen gas atmosphere using a jet mill to obtain an alloy powder having an average particle size of 3.5 μm. This pulverizing step is suitably performed by using the apparatus and method described in Japanese Patent Application No. 11-62848.

The obtained alloy powder was transferred into a rocking mixer, and a lubricant diluted with methyl caproate: isoparaffin = 1: 9 (weight ratio) was mixed with the alloy powder while spraying, whereby excess alloy was added. (First state alloy powder material) obtained by applying the lubricant to the surface of the alloy powder. This mixing step of the lubricant and the alloy powder can be suitably performed by using the apparatus and method described in Japanese Patent Application No. 11-50171.

The embodiment will be further described with reference to FIG. The obtained alloy powder material (about 250 kg) was accommodated in a stainless steel airtight container (content: about 700 liters) 1 as shown in the schematic diagram of FIG. Nitrogen gas as an inert gas is supplied into the container 1 from the gas inflow pipe 3 fixed to the lid 5 at a rate of 10 liter / min, and is discharged from the gas discharge pipe 4 so that the alloy powder material 2 in the container 1 Was supplied with nitrogen gas.

FIG. 2 is a graph showing the relationship between the total amount of the lubricant and the solvent contained in the alloy powder material 2 (indicated by weight% based on the alloy powder) and the air flow time.

As is apparent from FIG. 2, the content of both decreases with the flow time, indicating that the lubricant and the solvent are volatilized. Under the above flow conditions, about 2 wt% of the lubricant and the solvent were added in about 0.5 minutes after about 120 minutes.
t%, and after about 300 minutes, about 0.2 wt%
Has decreased to After that, it was volatilized gradually until about 1200 minutes, decreased to about 0.06 wt%, and hardly changed even after about 72 hours and further 2 weeks.

After about 1200 minutes, the lubricant was not volatilized and became a constant value because the interaction between the surface of the alloy powder and the lubricant caused the lubricant to be relatively strong on the surface of the powder. Probably because it is retained. Therefore, when a method of removing the excessively applied lubricant by volatilizing the surface of the alloy powder is employed, at least a minimum amount of the lubricant is stably retained on the surface of the alloy powder by the interaction with the surface. Therefore, there is no shortage of lubricant. By using this phenomenon, excess lubricant is removed,
An alloy powder material containing a preferred amount of lubricant can be easily prepared. In addition, by flowing nitrogen gas, the air can be prevented from entering the container,
An alloy powder material containing a preferable amount of a lubricant can be stably stored for a long period of time.

The contents of the lubricant and the solvent were measured by a pyrolysis gas chromatography method using decomposition temperatures of 250 ° C., 500 ° C. and 800 ° C., and column temperatures of:
The test was performed under the conditions of 50 ° C. → 5 ° C./min→200° C.

Next, the result of evaluating the press formability of the alloy powder material will be described.

As described above, the lubricant and the solvent were volatilized by the flow of the nitrogen gas in the container 1, and the press formability of the alloy powder material containing different amounts of the lubricant and the solvent was evaluated. At each airflow time at each point shown in FIG. 2, the alloy powder material 2 was collected from the container 1, and about 7.5 g of the alloy powder material 2 was charged into a cylindrical container having an inner diameter of 10 mm.
Press molding was performed under a pressure of about 9.8 × 10 ⁵ Pa. FIG. 3 shows the result of examining the relationship between the total content of the lubricant and the solvent in the alloy powder material and the height of the obtained molded body (which has an inverse correlation with the compressibility).

As is apparent from FIG. 3, as the total content of the lubricant and the solvent decreases, the height of the molded body decreases and the compressibility improves. In particular, it can be seen that the compressibility improves when the total content of the lubricant and the solvent is about 0.5 wt% or less, and the effect is remarkable when the total content is about 0.3 wt% or less.

FIG. 4 shows the relationship between the content of the lubricant in the alloy powder material and the height (compressibility) of the obtained compact.
FIG. 4 shows the lubricant (0.2 wt%) in the same manner as above.
Only the results obtained for the alloy powder material obtained by adding only the alloy powder to the alloy powder are shown. Each point is similar to FIG. 3, and the flow time is 0 minute, about 60 minutes, about 120 minutes, about 120 minutes. 18
It corresponds to 0 minutes, about 300 minutes, about 600 minutes and about 1200 minutes. Even when only the lubricant was applied, the lubricant was volatilized by the flow of the nitrogen gas as in the case where the lubricant was diluted. However, when the solvent was not diluted with the solvent, it was observed that the solvent was less likely to evaporate than when the solvent was diluted.

Also in this case, as is apparent from FIG. 4, as the content of the lubricant decreases, the height of the compact decreases, and the compressibility improves. In particular, it can be seen that when the content of the lubricant is about 0.12 wt% or less, the compressibility is improved, and when the content is about 0.08 wt% or less, the effect is remarkable.

Further, for each of the alloy powder materials used in the evaluations of FIGS. 3 and 4, the occurrence of chipping or cracking in press molding was evaluated (about 1,000 samples).
Before removing excess lubricant by the flow of nitrogen gas, about 100 compacts were chipped or cracked, but in the sample added with the lubricant diluted with the solvent (Fig. 3), the total When the amount is about 0.5 wt% or less, 10 pieces or less (defective rate 1
% Or less, and at about 0.3 wt% or less, the number decreased to 5 or less (defective rate 0.5% or less). In the sample to which only the lubricant was added (FIG. 4), the defective rate was 1% or less when the amount of the lubricant was about 0.12 wt% or less, and the defective rate was 0.5% or less when the amount of the lubricant was about 0.08 wt% or less. .

From the above results, it has been clarified that the volatilization of the lubricant contained in the alloy powder material can improve the press formability of the alloy powder. This is because if the lubricant is more than necessary in the alloy powder material, the compressibility is adversely affected, and the content of the lubricant is reduced to a certain amount or less by volatilizing the lubricant. This is considered to be due to the ability to improve the performance.

The fact that the compressibility is improved as the content of the lubricant is reduced is that when the alloy powder is press-molded without adding a lubricant, as a problem before the problem of the compressibility is caused by the problem of forming the compact. This is completely different from the fact that cracking and chipping frequently occur, but the surface of the alloy powder is bonded (adsorbed) by the action of the alloy powder,
There is a lubricant that does not dissociate, which does not evaporate,
It is presumed to contribute to the improvement of compressibility.

As described above, nitrogen gas is supplied in the container 1 for 24 hours.
The alloy powder material 2 after flowing for a time is oriented using an electric press in a magnetic field of about 1.3 MA / m,
compression molded at a pressure of ton / cm ² , about 4.3 g / cm ³
A molded body having a width of 10 mm, a height of 10 mm and a length of 20 mm having a molded body density of 10 mm was obtained.

The obtained molded body was placed in an Ar atmosphere for about 108 hours.
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 magnetic properties of the obtained sintered magnet were iHc
(Coercive force) about 1 MA / m, Br (residual magnetic flux density) 1.2
5T, (BH) max (maximum energy product) about 260k
J / m ^ThreeMet.

[0083]

As described above, according to the present invention, R-Fe-B having excellent press formability (particularly compressibility) is obtained.
A method for preparing an alloy powder material for a sintered sintered magnet and a method for producing an R—Fe—B based sintered magnet using the same are provided.
Further, according to the present invention, there is provided a method for stably storing an alloy powder material for an R-Fe-B-based sintered magnet having excellent press formability (particularly compressibility). As a result, according to the present invention, it is possible to reduce cracking or chipping of the compact of the alloy powder material for the R-Fe-B based sintered magnet, and to improve the productivity of the R-Fe-B based sintered magnet. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic view of a container 1 for volatilizing a lubricant contained in an alloy powder material 2 by flowing nitrogen gas.

FIG. 2 is a graph showing a relationship between a nitrogen gas flow time and a total content of a lubricant and a solvent in an alloy powder material.

FIG. 3 is a graph showing the relationship between the total content of a lubricant and a solvent in an alloy powder material and the height (compressibility) of the obtained compact.

FIG. 4 is a diagram showing the relationship between the content of a lubricant in an alloy powder material and the height (compressibility) of the obtained compact.

[Brief description of reference numerals]

 DESCRIPTION OF SYMBOLS 1 Container 2 Alloy powder material 3 Gas inflow pipe 4 Gas discharge pipe 5 Lid

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 1/053 H01F 1/08 B 1/06 1/04 H 1/08 1/06 A

Claims (35)

[Claims] 1. A method for producing an R—Fe—B based sintered magnet, comprising: (a) providing a surface of an alloy powder for an R—Fe—B based sintered magnet;
Preparing a first state alloy powder material to which a first amount or more of lubricant has been applied; and (b) performing the lubrication by volatilizing a part of the lubricant of the first state alloy powder material. Preparing a second state alloy powder material in which the amount of the agent is reduced to a second amount or less; and (c) forming a compact by press-forming the second state alloy powder material. And (d) sintering the compact. 2. The step (a) includes a step of pulverizing a coarse powder of the alloy while supplying the lubricant.
The method according to claim 1. 3. The method according to claim 1, wherein the step (a) includes a step of mixing the alloy powder and the lubricant while supplying the lubricant to the alloy powder prepared in advance. Production method. 4. The method according to claim 1, wherein the step (b) includes a step of flowing an inert gas into an airtight container containing the alloy powder material in the first state. Method. 5. The method according to claim 1, further comprising, after the step (b), storing the alloy powder material in the second state in a state in which an inert gas is flown in the container or another hermetic container. The method according to claim 4, wherein 6. The method according to claim 1, further comprising a step of sampling the alloy powder material in the second state stored in the container and performing a composition analysis, after which the step (c) is performed. 5. The production method according to 5. 7. An alloy powder having an average particle size of 3 μm to 6 μm.
2. The method according to claim 1, wherein the thickness is in the range of μm. 8. The method according to claim 1, wherein the specific surface area of the alloy powder by the BET method is in a range of 0.45 to 0.55 m ² / g. 9. The method according to claim 1, wherein the first amount is at least 0.15 wt% of the weight of the alloy powder. 10. The method according to claim 1, wherein the second amount is 0.12% by weight or less of the weight of the alloy powder. 11. The method according to claim 1, wherein a main component of the lubricant is a fatty acid ester. 12. The method according to claim 1, wherein, in the step (a), the lubricant is applied to a surface of the alloy powder in a state diluted with a solvent. 13. The method according to claim 12, wherein a total of the solvent and the lubricant contained in the alloy powder material in the second state is 0.5 wt% or less of a weight of the alloy powder. 14. The solvent according to claim 1, wherein the solvent is a petroleum solvent.
3. The production method according to 2. 15. The method according to claim 12, wherein a main component of the lubricant is a fatty acid ester. 16. A method for preparing an alloy powder material for an R—Fe—B based sintered magnet, wherein a lubricant is provided on the surface of the alloy powder, comprising: (a) an R—Fe—B based sintered magnet; On the surface of the alloy powder
Preparing a first state alloy powder material to which a first amount or more of lubricant has been applied; and (b) performing the lubrication by volatilizing a part of the lubricant of the first state alloy powder material. Preparing a second state alloy powder material in which the amount of the agent has been reduced to a second amount or less. 17. The method according to claim 16, wherein the step (a) includes mixing the alloy powder and the lubricant while supplying the lubricant to the alloy powder prepared in advance.
Preparation method described in 1. 18. The preparation according to claim 16, wherein the step (b) includes a step of flowing an inert gas into an airtight container containing the alloy powder material in the first state. Method. 19. The alloy powder has an average particle size of 3 μm or more.
17. The preparation method according to claim 16, which is in the range of 6 [mu] m. 20. The method according to claim 16, wherein the specific surface area of the alloy powder by the BET method is in a range of 0.45 to 0.55 m ² / g. 21. The preparation method according to claim 16, wherein the first amount is 0.15% by weight or more of the weight of the alloy powder. 22. The preparation method according to claim 16, wherein the second amount is 0.12% by weight or less of the weight of the alloy powder. 23. The method according to claim 16, wherein the main component of the lubricant is a fatty acid ester. 24. The method according to claim 16, wherein in the step (a), the lubricant is applied to the surface of the alloy powder in a state diluted with a solvent. 25. The preparation method according to claim 24, wherein the total of the solvent and the lubricant contained in the alloy powder material in the second state is 0.5 wt% or less of the weight of the alloy powder. 26. The solvent according to claim 2, wherein the solvent is a petroleum solvent.
4. The preparation method according to 4. 27. The method according to claim 24, wherein the main component of the lubricant is a fatty acid ester. 28. A method for storing an alloy powder material for an R—Fe—B based sintered magnet, wherein a predetermined amount or less of a lubricant is applied to the surface of the alloy powder for the R—Fe—B based sintered magnet. A method of storing an alloy powder material in an airtight container with an inert gas flowing therethrough. 29. The alloy powder has an average particle size of 3 μm or more.
29. The storage method according to claim 28, which is in a range of 6 m. 30. The storage method according to claim 28, wherein the specific surface area of the alloy powder by the BET method is in a range of 0.45 to 0.55 m ² / g. 31. The storage method according to claim 28, wherein the predetermined amount is 0.12% by weight or less of the weight of the alloy powder. 32. The storage method according to claim 28, wherein a main component of the lubricant is a fatty acid ester. 33. The alloy powder material according to claim 28, wherein the alloy powder material includes the lubricant and a solvent, and a total of the lubricant and the solvent is 0.5 wt% or less of a weight of the alloy powder. How to save. 34. The solvent according to claim 33, wherein the solvent is a petroleum solvent.
Storage method described in. 35. The storage method according to claim 33, wherein a main component of the lubricant is a fatty acid ester.