JP2002025842A - Method for manufacturing rare-earth sintered magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a rare-earth sintered magnet, by which the oxidization of a rare-earth element can be suppressed fully and which excels in productivity. SOLUTION: This method for manufacturing a rare-earth sintered magnet includes (a) a step of press-molding an alloy powder for the rare-earth sintered magnet, (b) a step of housing a molded body in a case, where a flow passage for carrying in/discharging a gas from/to the outside is limited and to arrange a gas-absorbing material at least adjacent to the flow passage, and (c) a step of sintering the molded body, by heating the case housing the molded body in an evacuated atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a rare earth sintered magnet.

[0002]

2. Description of the Related Art Currently, two types of rare earth sintered magnets, samarium / cobalt magnets and neodymium / iron / boron magnets, are widely used in various fields. Among them, neodymium / iron / boron magnets (hereinafter referred to as "RT- (M) -B magnets". R is a rare earth element containing Y, and T is Fe or a mixture of Fe and Co and / or Ni. , M are additive elements (eg, Al, Ti, Cu, V, Cr, Ni, G
a, Zr, Nb, Mo, In, Sn, Hf, Ta, and W), and B is boron or a mixture of boron and carbon. ) 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] Rare earth sintered magnets are manufactured by forming a compact by pressing an alloy powder obtained by pulverizing a rare earth alloy in a magnetic field and sintering the compact in a sintering furnace. I have. In the sintering process, RT
When a rare earth element such as neodymium contained in the-(M) -B-based magnet is oxidized, the properties of the magnet are greatly deteriorated. In order to prevent this oxidation, the inside of the furnace is set in a vacuum state or a reduced pressure atmosphere of an inert gas (Ar or He or the like). When sintering multiple compacts, to improve production efficiency,
A closed type sintering case for multiple compacts ("Sintered pack")
Sometimes called. Is heated together with the sintering case. When sintering a large number of compacts, a sintering case having a sintering base plate arranged in a shelf shape is used. The compact obtained by press molding is arranged on a sintering base plate and is housed in a sintering case in a shelf shape.

However, according to Japanese Patent No. 2754098, when the sintering case and the base plate are repeatedly used, a rare earth element hydroxide is formed on the surfaces of the sintering case and the base plate, and this hydroxide is formed. There is a problem that rare earth elements are oxidized by water generated by thermal decomposition in the sintering process. The above-mentioned patent publication discloses that this problem can be solved by cleaning the inner surface of the sintering case and the surface of the base plate before sintering.

[0005]

However, if the manufacturing method described in the above-mentioned patent publication is adopted, it is necessary to perform the above-mentioned cleaning treatment every time the sintering process is used, for example, five times. There is a problem that the performance is reduced.

Further, as a result of the study by the present inventor, a sintering tray or a sintering cart was used for transferring (storing) the sintering case into and out of the sintering furnace, and these were sintered in the sintering furnace. When heated together with the case, the rare earth is generated by the water generated by the thermal decomposition of water and hydroxide (hydroxide of Ca, Mg and / or rare earth element) adsorbed on the surface of the sintering tray or sintering cart. It has been found that a problem that the element is oxidized occurs.

[0007] The above-mentioned oxidation sometimes extends not only to the surface of the sintered magnet but also to the inside thereof, causing a problem that a sintered magnet having a predetermined shape cannot be obtained. Since sintering does not progress in the oxidized part, no shrinkage occurs, and as a result, the density of the oxidized part is lower than the other parts,
Not only is it deformed, but also its magnetic properties deteriorate.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a rare-earth sintered magnet which can sufficiently suppress oxidation of a rare-earth element and has excellent productivity. It is to provide a manufacturing method.

[0009]

The method for manufacturing a rare earth sintered magnet according to the present invention comprises the steps of (a) pressing an alloy powder for a rare earth sintered magnet to form a compact, and (b) forming the compact. A step of housing the body in a case in which a flow path through which gas enters and exits from the outside is restricted, and disposing a gas absorbing material at least in the vicinity of the flow path; And sintering the molded body by heating in a reduced pressure atmosphere, whereby the object is achieved.

[0010] The gas absorbing material may be disposed in the case, or may be disposed outside the case.

The gas absorbing material preferably contains a rare earth alloy powder, and the rare earth alloy powder preferably has substantially the same composition as the alloy powder for the rare earth sintered magnet.

The average particle size of the rare earth alloy powder is preferably smaller than the average particle size of the alloy powder for the rare earth sintered magnet. That is, the specific surface area of the rare earth alloy powder is preferably larger than the specific surface area of the alloy powder for the rare earth sintered magnet.

It is more preferable that the rare earth alloy powder is magnetized.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to RT.
The method for producing the-(M) -B-based magnet will be described as an example, but the present invention can be applied to a method for producing another rare earth sintered magnet.

The method for producing a rare-earth sintered magnet according to the present invention comprises the steps of press-molding an alloy powder for a rare-earth sintered magnet to produce a compact, and providing a flow passage through which gas flows into and out of the compact. A step of arranging the gas absorbing material at least in the vicinity of the gas flow path, and sintering the molded body by heating the case containing the molded body in a reduced-pressure atmosphere, in a limited case. Inclusive. The gas absorbing material may be arranged so that the gas flowing into the case is in contact with the gas absorbing material, and even if arranged in the case,
It may be arranged outside the case.

The rare earth alloy powder to be press-molded is, for example, RT- (M) -B described in US Pat. No. 4,770,723 and US Pat. No. 4,792,368. A system rare earth alloy powder can be suitably used. Press molding is performed by various known methods.

A case for sintering is disclosed in Japanese Patent Publication No. 275.
No. 4098 can be used. For example, a closed case made of a heat-resistant metal material such as SUS310 or molybdenum having a thickness of about 2 mm can be used. What is a closed case?
It refers to a case in which the flow path through which gas flows between the inside of the case and the outside of the case is restricted. The inside of the case is not completely shut off from the outside, but gas flows into and out of the case through a restricted flow path, so that the inside of the case can be replaced with a vacuum state or a reduced pressure inert gas atmosphere. It has a simple structure.

In general, a plurality of compacts are placed in a sintering case, inserted together with the sintering case into a sintering furnace, and heated collectively. In order to efficiently store many compacts in one sintering case, a sintering base plate arranged in a shelf shape as described in Japanese Patent No. 2754098 may be used. Furthermore, in order to transfer the sintering case into the sintering furnace, a sintering tray or a sintering cart that supports the sintering case may be used. When the sintering process is automated, it is preferable to provide such a transport mechanism.

A sintering base plate, a sintering tray and a sintering carriage which are heated in a sintering furnace together with a sintering case are made of a heat-resistant material. For the sintering base plate, for example, one formed of the same metal material as the sintering case is used. For the sintering tray or sintering cart, carbon or carbon composite (for example, A carbon fiber reinforced carbon composite material (C / C composite) commercially available from Acros Co., Ltd. is used.

For example, a large number of compacts mounted on a plurality of sintering base plates are accommodated in a sintering case comprising a bottom container and a lid as described later. At this time, a gas absorbing material (hereinafter, referred to as a “getter”) fills the gap between the bottom container and the lid (the gap between the bottom container and the lid serves as a gas flow path).
Place. The space between the bottom container and the lid may be filled from inside the case or from the outside of the case. That is, when the atmosphere in the sintering furnace is replaced with an inert gas atmosphere of a vacuum state or a reduced pressure, the getter is set so that the gas flows into and out of the sintering case through at least the vicinity of the getter. Place. That is, the getter is arranged so that the gas enters and exits the inside and outside of the case near and / or through the getter.

Here, it is preferable to use a rare earth alloy powder as the getter. Substantially the same material as the alloy powder for the rare earth sintered magnet can be used. Therefore, for example, a fragment of a molded article or a defective molded article can be used, so that the rare earth alloy material can be effectively used, and no extra material cost for the getter is required. In addition, in order to efficiently exert the function as a getter, it is preferable to use a crushed defective product or a fragment of a molded product by pulverization. A mechanical pulverizer such as a jaw crusher or a pin mill can be used for pulverizing the molded body. Further, a defective sintered body may be used in a state of being roughly pulverized by hydrogen pulverization, or may be mechanically pulverized by a disk mill or a power mill. Furthermore, when finely pulverized by a jet mill, the specific surface area increases, and the gas adsorption effect improves.

Since the function as a getter is more effective as the surface area is larger, the average particle size of the rare earth alloy powder used as the getter is preferably smaller than the average particle size of the rare earth alloy powder for the sintered magnet. For example, from the viewpoint of magnetic properties and press formability, the average particle size of the rare earth alloy powder for a sintered magnet is preferably, for example, in the range of 1.5 μm to 7 μm, but the average particle size of the rare earth alloy powder used as a getter is preferred. The diameter is preferably, for example, in the range of 1.0 μm to 5 μm. The “average particle size” of the powder is, here, unless otherwise specified, the mass median diameter (mass median diameter).
eter: MMD).

When a magnetized powder is used as the rare earth alloy powder, there is an advantage that the getter can be efficiently arranged in the gap between the sintering cases by utilizing the cohesive force of the magnetic force of the powder.

Here, the reason why it is preferable to use a rare earth alloy powder as a getter will be described.

In general, in the field of powder metallurgy, in order to prevent a compact from being oxidized by oxygen or water vapor in a sintering step, the sintering atmosphere is changed to a hydrogen gas atmosphere or the compact is more easily oxidized than the compact. A method in which a getter (typically, metal Ti powder) is used is used. However, none of these methods can be used in sintering the rare earth alloy powder. When a hydrogen atmosphere is used, HDDR (Hydrogen Desproportor)
tensionation andtion
The crystal structure of the rare earth alloy sintered body changes due to a phenomenon known as Recombination (hydrogenation phase decomposition dehydrogenation recombination method), and desired magnetic properties cannot be obtained.

Further, since the rare earth element is a material that is very easily oxidized, a general getter such as a metal Ti powder cannot function as a getter for the rare earth alloy powder. Only metal calcium (Ca) is more easily oxidized than rare earth elements, but this is used as a getter, for example,
When a sintering case, sintering base plate, or sintering tray is used repeatedly, calcium adhering to these surfaces absorbs moisture in the air to form calcium hydroxide, which is heated in a sintering furnace. When this is done, the calcium hydroxide releases water, causing oxidation of the rare earth element. In addition, there is a danger of ignition of the metallic calcium exposed to the atmosphere.

Even if Ca is not used as a getter, a small amount of Ca or Mg is contained in the raw material of the rare earth alloy, and a sintering case, a sintering base plate, a sintering tray and a sintering cart are repeatedly used. , Ca and Mg are deposited on these surfaces.
In the process of repeatedly taking in and out of the sintering furnace from the atmosphere, hydroxides of Ca and Mg are formed on these surfaces, causing oxidation. Of course, even when the raw material does not contain Ca or Mg, as described in the above-mentioned Japanese Patent No. 2754098, a hydroxide of a rare earth element is formed on a sintering case or a sintering base plate. These will bring water into the sintering furnace. Further, water and hydroxide attached to the inner surface of the sintering furnace can also cause oxidation.

As described above, only water or hydroxide adhering to the solid surface (sintering case, sintering tray, sintering cart) in the sintering furnace is not the cause of the oxidizing gas, and Water and oxygen may enter the sintering furnace due to imperfections (leakage) of the kiln.

In the method for manufacturing a rare earth sintered magnet according to the present invention, the getter including the rare earth alloy powder disposed at least in the vicinity of the gas flow path is oxidized by an oxidizing gas such as water vapor or oxygen. This prevents the rare earth alloy powder for the sintered magnet constituting the compact from being oxidized. When the getter is placed outside the sintering case, the oxidizing gas is absorbed just before entering the sintering case,
When the getter is arranged in the sintering case, the oxidizing gas is absorbed immediately after entering the sintering case. In this specification, “at least the vicinity of the flow path” is a concept including the vicinity of the flow path and the inside of the flow path.

This mechanism will be described in some detail.

As the sintering case arranged in the sintering furnace controlled to a predetermined atmosphere is heated, the sintering of the compact housed therein proceeds. For example, water adsorbed on the surface of a compact placed in a sintering case in the air, for example, desorbs from the surface of the compact while the compact is heated to about 200 ° C. Is discharged outside the sintering furnace. At this time, since the temperature of the compact is sufficiently low, the rare earth alloy powder is hardly oxidized.

On the other hand, it is substantially impossible to raise the temperature in the sintering furnace uniformly, and a temperature distribution occurs. Therefore,
In the sintering furnace, there are portions where the temperature is lower (the temperature rise speed is slower) than the compact. Typically, the rate of temperature rise at the bottom of the sintering furnace is slow. Specifically, the sintering tray and the cart are heated more slowly than the compact. as a result,
After the temperature of the molded body reaches a temperature of 300 ° C. to 400 ° C. or more, the moisture (Ca
And water produced by thermal decomposition of hydroxide of Mg or hydroxide of rare earth element) are discharged into the sintering furnace. This water enters the sintering case in the process of diffusing in the sintering furnace. At this time, the temperature of the molded body has reached a temperature at which it can be oxidized by water and is in the early stage of sintering. If the molded body is exposed to water vapor at this time, it is oxidized and required for sintering. It is presumed that the density of the sintered body is reduced (that is, the sintered body is deformed) because the liquid phase is insufficient.

However, according to the present invention, since the getter is arranged at least in the vicinity of the path through which the gas flows into the sintering case, this steam is consumed by the oxidation reaction of the getter before reaching the compact. In addition, water vapor is prevented from reaching the compact. Since the getter is heated similarly to the molded body, it is in a state where it can react (absorb) with water vapor. As described above, it is important to prevent the molded body in a state where the temperature of the molded body is about 300 ° C. or higher and sintering has not sufficiently progressed from being exposed to water vapor in order to prevent a decrease in density. After the sintering has sufficiently proceeded, the compact has sufficiently shrunk, so that even if an oxidation reaction of the compact occurs, the density of the sintered compact decreases (that is, deforms).
Does not occur. Of course, the getter also has the function of trapping not only the above-mentioned water vapor but also the oxygen that enters the sintering case, and thus prevents the sintered body from being oxidized.

As described above, according to the present invention, there is provided a method of manufacturing a rare earth sintered magnet which can sufficiently suppress oxidation of a rare earth element and has excellent productivity.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Referring to FIGS. 1A and 1B,
The configuration of the sintering case 9 suitably used in the method for manufacturing a rare earth sintered magnet according to the present invention will be described.

The sintering case 9 is composed of a bottom container 90 having a bottom plate 90a and a side wall 90b, and a lid 92 covering the bottom container 90. A predetermined interval is provided in the bottom container 90 by a spacer 96. A plurality of sintering base plates 94 stacked in this manner are accommodated. On each sintering base plate 94, a large number of compacts 95 obtained by press-molding a magnet alloy powder are placed. Sintering case 9
Is heated to, for example, about 1000 ° C. or more in the sintering process, so that the bottom container 90 and the lid 92 are formed of a material having high temperature resistance (for example, SUS310).

The side wall 90b of the bottom container 90 is provided on the sintering base plate 9
4 and surrounds the periphery of the cover 4 at its upper end.
Support 2 Space surrounded by side wall 90b (storage space)
Is slightly larger (about several mm to several cm) than the size of the sintering base plate 94, and the gap between the side wall 90b and the sintering base plate 94 is designed to be small. . The reason why the gap between the side wall 90b and the sintering base plate 94 is reduced in this way is that by setting the size of the sintering base plate 94 as large as possible, more compacts 95 can be sintered. This is because it is accommodated in the case 9 to improve the accommodation efficiency in the sintering furnace. Also, by reducing the gap between the side wall 90b and the sintering base plate 94, the sintering base plate 94 can be sintered even when vibration is applied to the sintering case 9 during transportation or the like. It is possible to prevent the spacer disposed on the sintering base plate 94 from falling down by moving within the case 9.

A getter 97 for absorbing gas is placed at least near the path through which gas flows into and out of the sintering case 9. The getter 97 may also be arranged in the channel to close it. Specifically, an inner lid 98 (for example, a plate similar to the sintering base plate) is mounted on the uppermost sintering base plate 94 on which the compact 95 is mounted,
A powdery or small lump-shaped getter 97 is pushed in so as to fill a gap between the inner lid 98 and the side wall 90b of the bottom container 90. The gap between the inner lid 98 and the side wall 90b is
It is sufficiently small so that the getter 97 can be arranged so as to fill the gap between the side walls 90b.

The getter 97 first comes into contact with the gas flowing from the outside of the sintering case 9 into the inside of the sintering case 9. If the gas contains gas that reacts with the compact 95, such as water vapor or oxygen, the gas itself consumes the gas by reacting with the gas, thereby preventing the compact from being exposed to the gas. I do. Since the getter 97 contains the rare earth alloy powder, it has substantially the same reactivity as the compact 95, and thus reacts with all kinds of gases that react with the compact 95. As the getter 97, it is preferable to use a rare earth alloy powder having substantially the same composition as the rare earth alloy powder forming the compact 95. As the getter 97, a defective molding or a fragment of a molded body can be used. Further, in order to enhance the action of the getter 97, it is preferable to pulverize these and use a rare earth alloy powder having an average particle diameter smaller than that of the alloy powder forming the compact 95. Further, a coarsely or finely pulverized sintered body can be used as a getter.

When the above-mentioned sintering case 9 is used, it is necessary to stack a plurality of sintering base plates 94 in order in the storage space surrounded by the side wall 90b of the bottom container 90. As shown in FIG. 1 (b), the sintering base plate 94 is stacked in the bottom vessel 90 by using a sintering base plate 94 having a corner portion cut, and the sintering base plate 94 is supported by a fingertip. This was performed by stacking the base plates 94 one by one. This is because the gap between the side wall 90b and the sintering base plate 94 is narrow, and the sintering base plate 9
This is because 4 could not be placed in the bottom container 90. Such stacking of the sintering base plates 94 is very troublesome. Also, when stacking the sintering base plates 94,
Since the corners of the sintering base plate 94 are only unstablely supported by the fingertips, the sintering base plate 94 may be inclined. For example, when the compact 95 has a shape that easily rolls, when the sintering base plate 94 is inclined, the formed body 95 moves while rotating on the sintering base plate 94, and as a result, the formed body 95 is cracked or chipped. Or sometimes. In particular, R
In the case of a pressed body for a -T- (M) -B magnet, the pressing pressure is set smaller than that of a ferrite magnet in order to increase the degree of orientation. Easy to break when housed inside.

After the sintering process, the sintered compact is taken out of the sintering case 9 for aging treatment and transferred to another container. At this time, when using the sintering case 9, it is necessary to remove the lid 92 and the inner lid 98 of the sintering case 9 and take out the sintering base plate 94 from the bottom container 90. This operation is also performed in the bottom container 90.
It takes much time and effort as in the operation of stacking the sintering base plates 94 therein.

When the sintering case 9 is used, the getter 97 must be manually placed after the sintering base plates 94 are stacked. For this reason, from the step of accommodating the sintering base plate 94 on which the compact 95 is placed in the bottom container 90, the lid 92 is placed on the bottom container 90, and the actual case (for sintering in the state where the compact 95 is accommodated). It was not possible to automate and continuously perform the process up to the case 9).

Next, a description will be given of a sintering case suitable for storing the compact more easily than the above-mentioned sintered case 9 shown in FIG. 1 and for automatically accommodating the compact.

First, reference is made to FIGS. The sintering case 1 of the present embodiment includes a bottom plate 10 supporting a sintering base plate 30 and a lid 20 placed on the bottom plate 10. In the sintering case 1, a plurality of sintering base plates 3 are provided.
0 are accommodated in a stacked state at a predetermined interval by the columnar spacer 34. On the plate surface of each sintering base plate 30, a large number of compacts 32 obtained by press-forming magnet alloy powder are placed.

The lid 20 has a side wall 22 and an upper surface 24 formed of a high melting point metal. Lid 20 is bottom plate 1
When the sintering plate 3 is covered with the sintering base plate 3
The upper surface 24 covers the upper surface of the sintering base plate 30 so as to surround the periphery of the sintering plate 30. The shape and size of the upper surface portion 24 are determined according to the shape and size of the base plate 30 for sintering. The distance between the side wall portion 22 and the sintering base plate 30 is 3 mm to 10 m.
m is preferably set in the range of m. If the side wall portion 22 surrounds the sintering base plate 30 without substantially providing a gap, the sintering base plate 3 in the sintering case 1 can be obtained.
0 can be easily accommodated, and the displacement of the sintering base plate 30 in the sintering case 1 during transportation or the like can be suppressed. Since the lid 20 has a shape having the side wall 22, it is not easily deformed by heat.

The bottom plate 10 has a flat plate portion 10a made of a high melting point metal, and a lid 20 is formed around the flat plate portion 10a.
A peripheral portion 12 that can support the lower end portion of the side wall portion 22 over the entire periphery is provided. As shown in FIGS. 3A and 3B, the peripheral portion 12 preferably has a portion that protrudes outside the side wall portion 22 of the lid 20 even when the lid 20 is placed. Because, even when the lid 20 is covered, if such a protruding portion exists, the sintering case 1 can be easily stacked and unloaded by gripping the protruding portion. Because it can be.

On the flat portion 10a of the bottom plate 10, the peripheral portion 1
An outer peripheral wall 14 protruding upward from the vicinity of the inner peripheral wall 2 and an inner peripheral wall 16 located inside the outer peripheral wall 14 are provided.
The outer peripheral wall 14 comes into contact with the side wall 22 from the inside when the lid 20 is placed on the peripheral edge 12, and prevents the lid 20 from moving in the horizontal direction. As shown in FIG.
Is, for example, 15 ° from a direction perpendicular to the flat plate portion 10a.
It may be formed so as to be inclined inward to the extent. In this way, the lid 20 can be easily placed on the bottom plate 10 without the outer peripheral wall 14 being in the way. The inner peripheral wall 16 is higher than the outer peripheral wall 14, and the upper end of the inner peripheral wall 16 is
I support. The outer peripheral wall 14 and the inner peripheral wall 16 also function as a reinforcing member for preventing deformation of the bottom plate 10 together with a reinforcing member 18 described later.

A space (holding groove) 15 formed between the outer peripheral wall 14 and the inner peripheral wall 16 is filled with a getter 38 for absorbing impurity gas (mainly water vapor and oxygen). The getter 38 filled in the holding groove 15 is located near a path through which gas flows into and out of the sintering case 1 when the lid 20 is placed on the bottom plate 10.

Next, gas absorption by the getter 38 will be described with reference to FIG.

As shown in FIG. 5A, the getter 38
When impurity gas from outside the case flows into the case, the impurity gas can be absorbed. In the sintering step, when the steam and / or oxygen present in the sintering furnace flows into the sintering case, and thereby the oxidized compact (sintered body) after sintering, It is important to keep the getter 38 because the characteristics deteriorate. Thus, the getter 38 prevents the impurity gas such as water vapor or oxygen flowing from outside the case from causing an undesirable reaction with the sintered body.

Since the getter 38 needs to be replaced for each sintering process, it is desirable that the holding groove 15 has a shape and a size that allow the getter 38 to be easily taken out. Therefore, the distance between the outer peripheral wall 14 and the inner peripheral wall 16 (that is, the width of the holding groove 15) is set to 5 mm to 15 mm, and
It is preferable to set the height of 4 to 5 mm to 10 mm.

In order for the getter 38 to effectively absorb the gas, it is better to increase the exposed area of the getter 38 as much as possible. Therefore, the height of the inner peripheral wall 16 is set to be somewhat higher than the height of the outer peripheral wall 14 (for example, the inner peripheral wall 16 has a height of about 1.5 times or more the outer peripheral wall), and the getter 38 is set. It is preferable to stack diagonally from the outer peripheral wall 14 toward the inner peripheral wall 16.

The outer peripheral wall 14 and the inner peripheral wall 16 forming the holding groove 15 are also formed by using a member obtained by bending a long plate made of, for example, a high melting point metal into a U shape along the longitudinal direction. be able to. The outer peripheral wall 14 and the inner peripheral wall 16 can be formed by using four of these members and positioning them so as to correspond to the sides of the square, and welding the bottom portion of each member onto the flat plate portion 10a.

The getter 38 is not limited to the above-mentioned example, and may be arranged outside the case, for example, as shown in FIG. Disposing the getter on the outside has an advantage that the getter can be easily removed after the sintering step. On the other hand, as shown in FIG. 5A, when the getters 38 are arranged inside the case, relatively few getters 3 are provided.
8, the oxidizing gas can be absorbed more effectively. of course,
Getters 38 may be arranged on both the inside and outside of the case to further ensure the effect of absorbing the oxidizing gas.

Referring again to FIGS. The illustrated bottom plate 10 is on the flat plate portion 10a (on the plate surface of the bottom plate 10).
And two long reinforcing members 18 extending in parallel with each other, and a support member 19 located at the center of the plate surface.

The reason that the reinforcing member 18 is provided on the bottom plate 10 is that the bottom container 90 of the sintering case 9 is
While the shape having b is hard to be deformed by heat, the bottom plate 10 may be warped or deformed, thereby preventing the airtightness in the case from being reduced. Although the form of the reinforcing member 18 is not particularly limited, as shown in FIGS. 2 to 4, if two long members are arranged in parallel, the deformation of the bottom plate 10 can be appropriately prevented.
As shown in the cross section in FIG. 3, if the reinforcing member 18 is formed of a hollow member, the bottom plate 10 can be appropriately reinforced and the heat capacity of the bottom plate 10 as a whole does not greatly increase. The body can be heated efficiently. Reinforcing member 18 formed from a long member
Are connected to the opposite wall surfaces of the inner peripheral wall 16,
The reinforcing member 18 and the inner peripheral wall 16 are integrated, and the strength of the bottom plate is further improved.

The support member 19 provided at the center of the plate surface is
It has substantially the same height as the height of the inner peripheral wall 16.
By providing such a support member 19, it is possible to prevent the sintering base plate 30 placed thereon from bending, and to suppress the deformation of the sintered body disposed on the sintering base plate 30. Can be.

When using the sintering case 1 of this embodiment, the plurality of sintering base plates 30 on which the compacts 32 are mounted are
After being stacked in advance via a spacer 34, and the stacked product is placed on the inner peripheral wall 14 of the bottom plate 10, the lid 2
Cover with 0. For this reason, it is not necessary to accommodate the sintering base plates one by one in the case as in the case of using the sintering case 9 described above. Further, according to the sintering case 1, the sintering base plate on which the compact is mounted as in the sintering case 9 is not accommodated in the deep bottom case under unstable support. Therefore, the possibility that the molded body is cracked or chipped during the housing operation can be reduced. Further, unlike the sintering base plate 94 accommodated in the sintering case 9, it is not necessary to cut the corners to provide a gap between the sintering base plate 94 and the side wall of the container. However, it is preferable that the corners of the sintering base plate be cut off to some extent as a chamfer to prevent plate cracking. The operation of storing the compact in the sintering case 1 may be performed manually or may be performed automatically as described later.

The flat plate portion 10a of the bottom plate 10 of the sintering case 1
Is, for example, 280 mm long × 315 mm wide × 1 mm thick. The dimensions of the lid 20 are, for example, 270 mm in length × 305 mm in width × 70 mm in height and 1.5 mm in thickness. The bottom plate 10 and the lid 20 are formed of a material that can withstand heating in a sintering step or the like, for example, a high melting point metal such as stainless steel or molybdenum.
If the sintering case 1 is made of SUS310,
The deformation of the case due to heat can be reduced as compared with the case where the case is formed from 304.

The dimensions of the sintering base plate 30 are, for example,
It is 250 mm long x 300 mm wide x 1 mm thick. The sintering plate 30 is preferably formed from molybdenum. Molybdenum is suitable as a material for the base plate 30 for sintering because it has low reactivity with the molded body, good thermal conductivity, and good heat resistance.

Next, reference is made to FIG. FIG.
4 shows a cross section of a bottom plate 10 having a form different from that of the embodiment shown in FIG. As shown in FIGS. 10 (a) and 10 (b),
The edge of the bottom plate 10 may be bent upward,
It may extend further outward from the bent end.

[Apparatus for housing a compact in a sintering case]
Hereinafter, an apparatus for automatically accommodating a compact in the sintering case will be described.

First, reference is made to FIG. FIG. 6 is a view of the entire automatic storage device together with a press machine and the like as viewed from above.
The press machine 40 press-molds the alloy powder for a magnet in a magnetic field to produce a compact 32. The molded body 32 produced by the press 40 is transferred to the vicinity of the robot 42 by a moving device 41 such as a uniaxial actuator.

The plate holding unit 44 holds a large number of sintering base plates 30 in an overlapping manner.
The sintering base plate 30 is transferred to the arrangement unit 50 located near the sintering plate 2. The transfer of the sintering base plate 30 is performed, for example, using a multi-loader (not shown) provided with a suction device capable of sucking and holding the upper surface of the sintering base plate 30. This multiloader is configured to be movable in a three-dimensional direction.

The plate holding portion 44 has reactivity with the molded body 32.
Base powder for sintering 3
There may be provided a device (not shown) for spraying on
No. Spread such powder on the sintering base plate 30
For example, in the sintering process, the compact 32 is melted into the sintering base plate 30.
Wearing can be prevented. As such a powder, Dy
_TwoO_ThreePowder or CaF_TwoPowders can also be used (eg
For example, Japanese Patent Application Laid-Open No. 11-54353).

In the placement section 50, the robot 42 places a number of compacts 32 on the sintering base plate 30. At this time, the robot 42 takes the spacer 34 from the spacer holder 43 and places it on the sintering base plate 30.

Next, an apparatus for stacking a plurality of sintering base plates 30 on which the formed bodies 32 are arranged in the arrangement section 50 will be described with reference to FIG.

The illustrated apparatus includes a plate supporting device 48 capable of supporting the side edges of the sintering base plate 30 from both sides, and a lift 58 capable of moving up and down. The plate support device 48 is provided in, for example, the above-described multiloader.

As shown in FIG. 7A, of the plurality of sintering base plates 30 on which the compacts 32 are arranged, the sintering base plates 30 other than the uppermost sintering base plate 30 are: It is transferred into the temporary storage room R1 by the plate support device 48 and the lift 58, and is temporarily held here. The temporary storage room R1 includes a unit base 54.
This is a space surrounded by the partition wall 52 provided thereon and the shutter 56 provided on the partition wall 52. The shutter 56 is opened when the sintering base plate 30 is taken in and out of the temporary storage room R1, and is closed at other times. When the shutter 56 is closed, the temporary storage room R1 is substantially sealed.

An inert gas such as, for example, nitrogen gas is supplied to the temporary storage room R1, and the molded product 3 placed in the temporary storage room R1 is
The oxidation of 2 is suppressed. For example, when the sintering base plates 30 are stacked in eight stages, the compact 32 is placed on the lowermost sintering base plate 30.
It may take as long as about one hour from the placement of the molded body 32 to the placement of the compact 32 on the uppermost sintering base plate 30.
Even in such a case, if the sintering base plate 30 on which the compact 32 has already been placed is held in the inert gas atmosphere in the temporary storage chamber R1, the compact 32 can be exposed to the atmosphere for a long time. Can be prevented.

After the predetermined number of sintering base plates 30 have been stacked, the shutter 56 is opened, and as shown in FIG.
The plate supporting device 48 can lift the plurality of stacked sintering base plates 30 and move them by supporting the lowermost sintering base plate 30.

Referring back to FIG. Case holder 45
Are empty sintering cases (empty cases) 10, 2
Holds 0. The holding grooves 15 of the bottom plate 10 of the sintering case held by the case holding portion 45 are filled with getters 38 in advance by hand or the like. Using the above-described multiloader, the bottom plate 10 is sent from the case holder 45 to the storage unit 60, and the lid 20 is carried from the case holder 45 to the lid holder 46.

Next, an apparatus for accommodating the sintering base plate 30 in which the compact 32 is disposed in the accommodating section 60 in a sintering case will be described with reference to FIG.

After the bottom plate 10 carried by the plate supporting device 48 is placed on the support 62 in the storage section 60,
The plurality of sintering base plates 30 in a stacked state are carried from the placement unit 50 (see FIG. 7) to the storage unit 60 and placed on the bottom plate 10. Then, the suction device 49 of the multi loader
The lid 20 held by the lid holding section 46 (see FIG. 6) is carried to the accommodation section 60 by using the
0 is placed on the bottom plate 10 so as to cover 0. When the lid 20 is placed on the bottom plate 10, an inert gas such as nitrogen is supplied into the case for sintering so that the case is filled with the inert gas, and no air component remains in the case. Good.

A sintering case (hereinafter also referred to as an “actual case”) accommodating the sintering base plate 30 on which the compact 32 is placed.
Is moved to a temporary storage room R2 provided below the unit base 54. The movement of the actual case is as follows. With the support 62 removed and the shutter 64 opened, the multi-loader plate support device 48 descends while supporting the peripheral portion 12 (see FIGS. 2 to 4) of the bottom plate 10. It is performed by:

The temporary storage room R2 includes the unit base 54,
This is a sealable space surrounded by a shutter 64, a partition wall 66 provided on the floor, and a door 67. An inert gas such as nitrogen is supplied to the temporary storage chamber R2. By filling the temporary storage room R2 with the inert gas in this way, even when the real case is left in the temporary storage room R2 for a long time, it is possible to prevent the atmospheric components from flowing into the real case. Therefore, oxidation of the molded body 32 in the actual case can be suppressed.

The temporary storage room R 2 is provided with a transport roller 69 for facilitating the movement of the actual case, and an extrusion device 68 for extruding the actual case toward the door 67.
The actual cases 10 and 20 are sequentially stacked on the transport roller 69 by the plate supporting device 48. As shown in FIGS. 2 to 4, since the bottom plate 10 of the sintering case 1 has a portion protruding outward from the lid 20 even when the lid 20 is placed, this portion is supported by the plate. When supported by the device 48, the actual cases can be easily stacked.

The actual cases stacked in a predetermined number of stages in this manner are moved to the door 67 by the pushing device 68. The actual case moved to the front of the door 67 is taken out by opening the door 67.

The number of actual cases temporarily stored in the temporary storage room R2 can be selected as desired. For example, first, the actual cases are stacked vertically in five stages, and are moved in the direction of the door 67 so as not to be in the way, and the actual cases are stacked vertically in five stages immediately adjacent to the moved actual case. Thus, ten actual cases of 5 rows × 2 rows can be placed in the temporary storage room.

[Method of Manufacturing Rare Earth Magnet] A method of manufacturing a rare earth magnet using the above-described sintering case will be described below.

First, a rare earth magnet powder formed by a known method is prepared. In the present embodiment, RT-
In order to manufacture the (M) -B-based magnet, first, a cast of an RT- (M) -B-based alloy is prepared using a strip casting method. Strip casting is disclosed, for example, in US Pat. No. 5,383,978. In particular,
Nd: 30 wt%, B: 1.0 wt%, Al: 0.2 w
An alloy having a composition of t%, Co: 0.9 wt%, the balance of Fe and unavoidable impurities is melted by high frequency melting to form a molten alloy. After maintaining the molten alloy at 1350 ° C., the molten alloy is rapidly cooled by a single roll method to obtain a flake-shaped alloy ingot having a thickness of 0.3 mm. The rapid cooling condition at this time is, for example, a roll peripheral speed of about 1 m / sec, a cooling speed of 500 ° C./sec, and a degree of supercooling of 200 ° C.

If the flake-like alloy ingot is roughly pulverized by a hydrogen absorbing method and then finely pulverized in a nitrogen gas atmosphere using a jet mill, an alloy powder having an average particle diameter of about 3.5 μm can be obtained. .

To the alloy powder thus obtained, 0.3% by mass of a lubricant is added and mixed in a rocking mixer, and the surface of the alloy powder particles is coated with the lubricant. It is preferable to use a lubricant obtained by diluting a fatty acid ester with a petroleum solvent. In the present embodiment, methyl caproate is preferably used as the fatty acid ester, and isoparaffin is preferably used as the petroleum solvent. The weight ratio between methyl caproate and isoparaffin may be, for example, 1: 9.

Next, the above-mentioned alloy powder is compression-molded using a press machine, thereby producing a compact having a predetermined shape.
The density of the molded body is set to, for example, about 4.3 g / cm ³ .

A number of the compacts thus obtained are placed on a sintering base plate made of molybdenum. A plurality of sintering base plates on which the formed bodies are arranged are stacked at intervals with a spacer, and these are accommodated in the sintering case 1. The housing of the molded body in the sintering case 1 can be executed, for example, by using the above-described automation device.

Case 1 for sintering containing many compacts
Is placed on a sintering tray 78 made of, for example, a carbon composite, and is conveyed to a place where a sintering device 70 having the configuration shown in FIG. 9 is installed using, for example, an automatic conveying device.

The sintering apparatus 70 includes a preparation chamber 71, a binder removal chamber 72, a first sintering chamber 73, a second sintering chamber 74, a cooling chamber 75, and the like.
Through 77d. Connecting parts 77a to 77
d is configured to move between the processing chambers without exposing the sintering case 1 to the atmosphere. Case 1 for sintering
Is conveyed by rollers 76 in such a sintering apparatus 70, stops in each processing chamber, and receives necessary processes there for a predetermined time. Each process is executed according to a recipe appropriately selected from a plurality of preset recipes. From the viewpoint of improving mass productivity, it is preferable that the processing executed in each processing chamber is controlled in a unified manner by a central controller or the like. For each treatment, an optimal known process may be adopted according to the type of the rare earth magnet to be manufactured. Hereinafter, each processing step will be briefly described.

First, at least one sintering case 1 is inserted into a preparatory chamber 71 provided at the entrance of the sintering apparatus 70, and the preparatory chamber 71 is closed. The inside of the preparation chamber 71 is evacuated until the pressure becomes about Pascal. The sintering case 1 undergoes a sintering step together with the sintering tray 78 while being placed on the sintering tray 78.

Next, the sintering case 1 is removed from the binder removal chamber 72.
Where the binder is removed (temperature: 100 ° C. to 6 ° C.).
00 ° C., pressure: 2 Pascal, time: 3-6 hours). The binder removal treatment is performed to volatilize a lubricant (binder) covering the surface of the magnetic powder before the sintering step. The lubricant is mixed with the magnetic powder before the press molding in order to improve the orientation of the magnetic powder at the time of the press molding, and exists between the particles of the magnetic powder. The getter 38 held on the bottom plate 10 (FIGS.
FIG. 4) absorbs water vapor and oxygen flowing into the sintering case 1 and suppresses oxidation of the compact. When the temperature of the binder removal processing is 300 ° C. or more, the getter 38 works particularly effectively.

After the binder removal processing is completed, the sintering case 1 is transferred to the sintering chamber 73 or 74 where it is removed.
Receive a sintering process at 00 to 1100 ° C. for about 2 to 5 hours.
During this sintering process, the getter 38 absorbs water vapor and / or oxygen flowing into the sintering case 1 from the sintering chamber,
Suppresses oxidation of the sintered body. After this, the sintering case 1
The sintering case is conveyed to a cooling chamber 75, where it undergoes a cooling process until the temperature of the sintering case drops to about room temperature.

Next, the sintering case 1 is taken out of the sintering device 70 and inserted into the aging furnace, and the normal aging process is performed. In the aging treatment, for example, the pressure of the atmospheric gas such as argon is set to about 2 Pascal,
It is performed at a temperature of 0 to 600 ° C. for about 1 to 5 hours. The sintered body shrunk by the sintering process is converted into a sintering case 1
When the aging treatment is performed after the sinter is removed from the container and transferred to another container, more sintered bodies can be processed at once than in the case where the processing is performed while the sintering case is accommodated. When using the sintering case 1 of the present embodiment, the removal of the sintered body from the sintering case 1 can be easily performed by removing the lid, as in the case of using the conventional sintering case 9. It is not obstructed by the side wall of the bottom container. Therefore, work efficiency can be improved. Alternatively, the aging treatment may be performed by removing the lid of the sintering case 1 and putting the bottom plate in a state where the sintering base plate on which the sintered body is mounted on the sintering base plate is stacked on the aging treatment furnace. . in this case,
By simply removing the lid, the sintered body can be exposed to an atmosphere gas such as argon, so that rapid cooling in the aging treatment can be efficiently performed.

A plurality of sintering cases are simultaneously carried into each of the above-mentioned processing chambers, where the plurality of sintering cases are simultaneously subjected to the same processing. In addition, while the sintering process is being performed in the sintering chamber, the sintering case that has already been subjected to the sintering process is cooled in the cooling chamber, and the sintering case that will be subjected to the sintering process is removed from the binder chamber. In this case, the binder can be removed, so that each processing step can be efficiently advanced.

Generally, since a relatively long time is required for the sintering process, a plurality of sintering chambers are arranged as shown in FIG.
It is preferable that the sintering process can be performed on a large number of sintering cases. In this case, the content of each sintering process performed in a plurality of sintering chambers may be different for each sintering chamber.

The method for producing a rare earth sintered magnet of the present invention is not limited to the magnet having the above-described composition, but may be any one of R-T-
It is widely and suitably applied to (M) -B magnets. For example, as the rare earth element R, Y, La, Ca, Pr, Nd, S
A raw material containing at least one element of m, Gd, Tb, Dy, Ho, Er, Tm, and Lu can be used. To obtain sufficient magnetization, 50 of the rare earth elements R are required.
Preferably, at% or more is occupied by either or both of Pr and Nd. Rare earth element R is 10at
% Or less, the coercive force decreases due to the precipitation of the α-Fe phase. On the other hand, if the rare earth element R exceeds 20 at%, a large amount of the R-rich second phase precipitates in addition to the target tetragonal Nd ₂ Fe ₁₄ B type compound, and the magnetization decreases. For this reason, the rare earth element R is preferably in the range of 10 to 20 at% of the whole.

T is Fe or a transition metal element containing Fe and Ni and / or Co. T is 67at%
If it is less than 2, a second phase having low coercive force and low magnetization is precipitated, so that the magnetic properties deteriorate. When T exceeds 85 at%, the coercive force decreases due to the precipitation of the α-Fe phase, and the squareness also decreases. Therefore, the content of T is 67 to 85 at%.
Is preferably within the range. Note that T may be composed only of Fe, but for example, the addition of Co increases the Curie temperature and improves heat resistance. T of 50a
Preferably, at least t% is occupied by Fe. This is because the saturation magnetization itself of the Nd ₂ Fe ₁₄ B type compound decreases when the proportion of Fe is less than 50 at%.

B is boron or a mixture of boron and carbon, and is essential for stably depositing a tetragonal Nd ₂ Fe ₁₄ B type crystal structure. If the addition amount of B is less than 4 at%, the R ₂ T ₁₇ phase is precipitated, so that the coercive force is reduced and the squareness of the demagnetization curve is significantly impaired. When the amount of B added is 10
If it exceeds at%, the second phase having a small magnetization will precipitate. Therefore, the content of B is preferably in the range of 4 to 10 at%.

To further increase the magnetic anisotropy of the powder, another additive element may be added. As additional elements,
Al, Ti, Cu, V, Cr, Ni, Ga, Zr, N
At least one element selected from the group consisting of b, Mo, In, Sn, Hf, Ta, and W can be suitably used. Such additional elements need not be added at all. When adding, the addition amount is preferably set to 10 at% or less. If the addition amount exceeds 10 at%, not the ferromagnetism but the second phase will precipitate and the magnetization will decrease.
Note that the additive element M is not required to obtain magnetically isotropic magnetic powder, but Al, Cu, Ga, or the like may be added to increase the intrinsic coercive force.

[0099]

According to the present invention, there is provided a method of manufacturing a rare earth sintered magnet which can sufficiently suppress oxidation of a rare earth element and is excellent in productivity. INDUSTRIAL APPLICABILITY The present invention is suitably applied to the production of a high-performance RT- (M) -B magnet having a low oxygen content (for example, an oxygen content of 3000 ppm or less).

Further, according to the present invention, there is provided a sintering case in which the compact can be easily stored in the sintering case or taken out of the sintering case. Is greatly improved. Further, it is possible to reduce the possibility that the molded body will be damaged when housed in the sintering case.

Note that the effect of the present invention is that RT- (M)-
The present invention is also exerted when the present invention is applied to the manufacture of a sintered magnet other than the B-based magnet.

[Brief description of the drawings]

1A and 1B show a sintering case used in an embodiment of the present invention, wherein FIG. 1A is a cross-sectional view and FIG. 1B is a plan view with a lid removed.

FIG. 2 is an exploded perspective view schematically showing another sintering case used in the embodiment of the present invention.

3 shows a cross section of the sintering case shown in FIG. 2, and (a)
Is an overall view, and (b) is a partially enlarged view.

FIG. 4 is a plan view of a bottom plate included in the sintering case shown in FIG. 2;

FIGS. 5A and 5B are diagrams showing a state in which a getter held by a bottom plate absorbs a gas that is going to flow into the case from outside the case.

FIG. 6 is a plan view showing an example of a layout of an apparatus for automatically storing a compact in a sintering case.

FIG. 7 is a sectional view showing an arrangement portion of the device shown in FIG. 6;

FIG. 8 is a sectional view showing a storage section of the device shown in FIG.

FIG. 9 is a diagram showing a sintering apparatus including a sintering chamber and the like.

FIG. 10 is an enlarged cross-sectional view showing a part of a sintering case according to an embodiment different from the sintering case shown in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Bottom plate 12 Peripheral edge part 14 Outer peripheral wall 15 Holding groove 16 Inner peripheral wall 18 Reinforcement member 19 Support member 20 Cover 22 Side wall part 24 Top surface part 30 Sintering base plate 32 Molded object 34 Spacer 38 Getter

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kunihisa Kanno 1062 Oyabu, Yabu-cho, Yabu-gun, Hyogo Kinki-Sumi Tokuden Co., Ltd. F-term (reference) 4K018 AA27 BA18 BC40 CA11 DA32 DA39 DA50 KA45 5E040 AA03 BD01 CA01 5E062 CD04 CE04

Claims (6)

[Claims] (A) a step of press-molding an alloy powder for a rare-earth sintered magnet to produce a compact; and (b) a flow path through which gas flows in and out of the compact with the outside. (C) sintering the compact by heating the casing containing the compact in a reduced-pressure atmosphere; When,
A method for producing a rare earth sintered magnet, comprising: 2. The method for manufacturing a rare earth sintered magnet according to claim 1, wherein the gas absorbing material is disposed in the case. 3. The method for manufacturing a rare earth sintered magnet according to claim 1, wherein the gas absorbing material includes a rare earth alloy powder. 4. The method for producing a rare earth sintered magnet according to claim 3, wherein the rare earth alloy powder has substantially the same composition as the alloy powder for the rare earth sintered magnet. 5. An average particle size of the rare earth alloy powder is smaller than an average particle size of the alloy powder for the rare earth sintered magnet.
A method for producing a rare earth sintered magnet according to claim 3. 6. The method for manufacturing a rare earth sintered magnet according to claim 3, wherein the rare earth alloy powder is magnetized.