JP2002083730A - Dispersed solution coating device and method of manufacturing rare earth magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating device, capable of uniformly coating the top of a base plate for sintering with a dispersed solution obtained by dispersing powder in a liquid, to uniformly apply the powder on the base plate. SOLUTION: This dispersed solution coating device 1 coats the top of a base plate 5 for sintering a magnet with a dispersed solution 3, obtained by dispersing oxide powder having a specific gravity larger than that of a liquid, in the liquid. This dispersed solution coating device 1 is equipped with a vessel 10 for housing the dispersed solution 3, an agitator 12 for agitating the dispersion 3 housed in the vessel 10, a transport passage 20 for transporting the dispersed solution 3 from the vessel 10 to the base plate 5 and a homogenizer 26 for homogenizing the dispersed solution 3, by applying a mechanical force at least to a part of the dispersed solution 3 flowing in the transport passage 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating apparatus for coating a dispersion of an oxide powder in a liquid on a base plate for magnet sintering, and a rare earth magnet using the coating apparatus. In particular, the present invention relates to a coating apparatus for applying a homogenized dispersion liquid on a base plate, and a method for manufacturing a rare earth magnet using the coating apparatus.

[0002]

2. Description of the Related Art Rare earth sintered magnets are produced by pressing an alloy powder formed by pulverizing an alloy for a rare earth magnet (raw material alloy), followed by a sintering step and an aging heat treatment step. At present, two types of rare earth sintered magnets, samarium / cobalt magnets and neodymium / iron / boron magnets, are widely used in various fields. Above all, neodymium-iron-boron magnets (hereinafter referred to as "RT- (M) -B magnets"), R is a rare earth element containing Y (yttrium), T is Fe (iron), Co (cobalt) ), Transition metal elements including Ni (nickel), M is an additive element, B is boron and a compound of boron and carbon), exhibit the highest maximum magnetic energy product among various magnets, Is relatively cheap, so it has been actively used in various electronic devices.

In a sintering step at the time of manufacturing a magnet, a pressed compact (compact) is placed on a sintering base plate made of a material having high heat resistance such as stainless steel or molybdenum. Is put into the sintering furnace. The press-formed body placed in the sintering furnace is heated to a high temperature (for example, 1000 to 1100 ° C.) in an inert gas atmosphere. The heated pressed body is sintered with shrinkage,
A rare earth sintered magnet is obtained.

[0004] When sintering, if the press-formed body is directly placed on the sintering base plate, the formed body and the base plate may be locally welded. This is because a rare earth element such as Nd, which is a main component of the RT- (M) -B-based magnet, causes a eutectic reaction with the metal element contained in the base plate at a temperature lower than the sintering temperature. When the base plate and the molded body are locally welded,
The dimensional shrinkage of the molded body due to sintering does not proceed smoothly, and cracks and chips occur in the sintered body. Further, even when welding does not occur, the friction between the base plate and the formed body (sintered body) becomes uneven, so that the formed body may be cracked on the side contacting the base plate. There is. Further, if the eutectic reaction product adheres to the sintering base plate, there is a problem that it takes time and effort to remove the attached matter from the base plate when reusing the sintering base plate.

[0005] In order to prevent welding between the sintering base plate and the compact, there has conventionally been known a method of laying powder on a sintering base plate and placing the compact thereon to perform sintering. (Eg, Japanese Patent Application Laid-Open No. 4-154903). As the laying powder, a powder formed of a material having low reactivity with a molded body and good stability at high temperatures is used. When the compact contains a rare earth metal, a material having low reactivity with the rare earth metal, such as a rare earth oxide (for example, neodymium oxide), is used as the spreading powder. The use of the spreading powder can prevent welding between the base plate and the compact, so that breakage or deformation of a crack or the like generated at the base plate contact portion of the rare earth magnet can be prevented.

[0006] As a method of spreading the bedding powder on the base plate, LP
There are known a method of spraying using a gas, a method of dispersing a litter in a volatile dispersion medium such as ethanol, and then applying the powder on a base plate. Also, JP-A-11-5435
No. ₃ discloses a method in which an organic solvent such as ethanol or acetone is added to a litter formed of Dy ₂ O ₃ or CaF ₂ to form a slurry, and the slurry is applied on a base plate using a brush or the like. Has been described.

[0007]

However, it is difficult to uniformly spread the litter on the base plate by the method of spraying litter with gas. If the laying powder is not evenly spread on the base plate, the friction generated between the formed body and the base plate when the formed body is partially welded to the base plate during sintering or when the formed body shrinks When the (resistance) is partially different, the compact does not shrink uniformly. As a result, breakage (cracks, etc.) and undesired deformation of the sintered body occur. In particular, when the shape of the molded body is long, shrinkage of the molded body becomes uneven, and cracks and deformation are likely to occur.

In a method of applying a dispersion liquid in which a powder is dispersed in a volatile liquid such as ethanol or a slurry in which an organic solvent is added to a powder on a base plate using a brush or the like, Since the work of coating on a plate takes time, productivity has been reduced. In order to spread the laying powder (powder) evenly on the base plate, it is necessary to apply a dispersion or slurry-like material to the base plate uniformly with a small thickness. It is difficult to apply uniformly on a board.

In addition, rare earths are used in volatile liquids such as ethanol.
When powders such as oxides are dispersed, volatile liquid
The difference in specific gravity between powder and powder is relatively large (for example, ethanol
And R _TwoO_Three(Rare-earth oxide)
0.8 and 7 to 8), the liquid in the dispersion
Easy to separate from powder. When using such dispersions
In this case, it is difficult to keep the powder concentration in the dispersion liquid uniform.
It is difficult. Therefore, even if the dispersion is applied evenly on the base plate
Even if it does, the concentration of the applied dispersion may
These dispersions are often different.
It is difficult to spread the powder (powder) evenly on the base plate
Was. If the spreading powder cannot be spread evenly, the sintered body may be damaged.
And undesirable deformations are likely to occur.

[0010] In addition, when a coating material in the form of a dispersion or slurry is to be automatically applied to a base plate via a pipe, the coating material may clog the pipe. In particular, in the case where coating is discontinuously performed with a time interval between each base plate and the like, the supply of the coating material is temporarily stopped or delayed, and if the flowability of the coating material flowing through the pipe deteriorates, powder Precipitates and clogs the pipes.

The present invention has been made in view of the above points, and a main object of the present invention is to transfer a dispersion of oxide powder (spreading powder) to a liquid through a transfer path such as a pipe or a tube. An object of the present invention is to provide a coating apparatus capable of uniformly applying a powder on an sintering base plate without clogging, thereby uniformly spreading oxide powder on the base plate.

Another object of the present invention is to spread an oxide powder evenly on a sintering base plate using the above-mentioned coating apparatus, thereby forming a compact formed on the base plate during sintering. It is an object of the present invention to provide a method for manufacturing a rare earth magnet that prevents cracks and the like from occurring.

[0013]

SUMMARY OF THE INVENTION A dispersion liquid coating apparatus according to the present invention applies a dispersion liquid in which an oxide powder having a specific gravity greater than that of the liquid is dispersed on a liquid on a base plate for magnet sintering. An apparatus, a container for containing the dispersion, a stirrer for stirring the dispersion contained in the container, a transfer path for transferring the dispersion from the container to the base plate, and the transfer path A homogenizing device for homogenizing the dispersion by applying a mechanical force to at least a part of the flowing dispersion.

In a preferred embodiment, the homogenizer generates an unsteady flow in at least a part of the dispersion flowing through the transfer path.

In a preferred embodiment, the unsteady flow is a flow in a direction opposite to a direction from the container toward the base plate.

In a preferred embodiment, the apparatus has a discharge path connected to the transfer path and capable of discharging the dispersion flowing in the opposite direction.

[0017] In a preferred embodiment, the homogenizer can eject a fluid into the dispersion flowing through the transfer path.

[0018] In a preferred embodiment, the fluid is air.

In a preferred embodiment, the apparatus has a discharge path connected to the transfer path and capable of discharging at least a part of the fluid.

In a preferred embodiment, the discharge path extends into the container.

In a preferred embodiment, the homogenizer can generate the unsteady flow in the dispersion in the vicinity of a connection between the transfer path and the container.

In a preferred embodiment, a metering pump is provided on the transfer path downstream of the homogenizer.

In a preferred embodiment, there is provided a spreading device for spreading the dispersion liquid supplied onto the base plate via the transfer path on the base plate.

In a preferred embodiment, the spreading device includes a water-absorbing roller provided so as to be in contact with the surface of the base plate.

In a preferred embodiment, the homogenizing device applies a mechanical force to the transfer path.

In a preferred embodiment, the homogenizer shakes the transfer path.

[0027] In a preferred embodiment, the apparatus further comprises a plate cleaning device for cleaning the plate before applying the dispersion, wherein the plate cleaning device removes the powder on the plate. The apparatus includes a powder emitting unit to be collided and a rocking device for rocking the powder discharging unit, wherein the homogenizing device is connected to the rocking device of the bed plate cleaning device, and the rocking device Shakes the transfer path.

In a preferred embodiment, the transfer path includes a nozzle connected to an end of the transfer path opposite to the container side, and a gas supply path connected to the nozzle. Using the gas supplied to
The dispersion is sprayed on the base plate.

In a preferred embodiment, the liquid is formed from a volatile liquid.

In a preferred embodiment, the oxide powder is formed from a rare earth oxide powder.

In the method for producing a rare earth magnet according to the present invention, a step of preparing a base plate for magnet sintering and the method of dispersing the oxide powder by using any one of the above-described dispersion coating apparatuses. A step of applying a dispersion onto the base plate; and a step of placing a compact produced by press-molding a rare earth magnet alloy powder on the base plate on which the dispersion is applied; And sintering the compact placed on the substrate.

In a preferred embodiment, the base plate has a surface roughness Rmax of 1 μm or more and 300 μm or less.

In a preferred embodiment, the surface roughness Ra of the base plate is 0.1 μm or more and 150 μm or less.

In a preferred embodiment, the concentration of the dispersion is from 200 g / liter to 500 g / liter.

In the method for producing a rare earth magnet according to the present invention, a step of preparing a base plate for magnet sintering and a step of preparing a dispersion liquid in which an oxide powder having a specific gravity greater than the liquid is dispersed in a liquid. Applying the molded body formed by pressing the alloy powder for rare earth magnet onto the base plate on which the dispersion liquid has been applied; and forming the molded body placed on the base plate. And a step of sintering the body, wherein the surface roughness Rmax of the base plate is 1 μm or more and 300 μm or less.

In the method for producing a rare earth magnet according to the present invention, a step of preparing a base plate for magnet sintering and a step of preparing a dispersion liquid in which an oxide powder having a specific gravity greater than the liquid is dispersed in a liquid are carried out. Applying the molded body formed by pressing the alloy powder for rare earth magnet onto the base plate on which the dispersion liquid has been applied; and forming the molded body placed on the base plate. And sintering the body, wherein the surface roughness Ra of the base plate is 0.1 μm or more and 150 μm or less.

[0037] In a preferred embodiment, the concentration of the dispersion is from 200 g / liter to 500 g / liter.

In a preferred embodiment, the powder has an average particle size of 1 μm to 20 μm.

The rare earth magnet according to the present invention is a rare earth magnet manufactured by any of the manufacturing methods described above.

In this specification, the term “dispersion liquid” means a powder in which a powder is dispersed, and a liquid in which a powder is non-uniformly dispersed in a liquid or a powder. Also includes those whose parts are settled.

[0041]

Embodiments of the present invention will be described below with reference to the drawings.

[Dispersion Coating Apparatus] (Embodiment 1) First, reference will be made to FIG. The dispersion liquid applying apparatus 1 of the present embodiment is disposed close to a shot blaster 7 for cleaning the surface of the sintering base plate 5. The shot blaster 7 removes deposits on the surface of the base plate 5 by causing powder such as alumina to collide with the surface of the base plate 5. The base plate 5 whose surface has been cleaned by the shot blaster 7 is transported to a position where the dispersion liquid is applied by a transport device 8 including a plurality of rotating rollers and the like.
Here, the dispersion coating device 1 coats the surface of the base plate 5 with a dispersion obtained by dispersing powder spread into a liquid. The base plate 5 on which the dispersion liquid 3 is applied by the dispersion liquid application device 1 is preferably carried to a robot 9 having a suction device 9a or the like by a moving device 8 when the application surface is dried, and is stacked at a predetermined place. Is held. Thereafter, the base plate 5 is carried to an arrangement device (not shown) for arranging the compact on the base plate.

Hereinafter, the configuration of the dispersion liquid coating apparatus 1 will be described. The dispersion liquid coating apparatus 1 includes a tank 10 containing a dispersion liquid 3 in which an oxide powder such as a rare earth oxide is dispersed in a volatile liquid such as alcohol, and the dispersion liquid 3 on the base plate 5 from the tank 10. Transport tube 20 for transporting and dispersion liquid 3 to base plate 5
And a spreading device 30 capable of spreading on the top.

A stirrer 12 for stirring the dispersion 3 contained in the tank 10 is attached to the tank 10 of the dispersion coating device 1. The stirrer 12 has a blade 12a located near the bottom of the tank, and the blade 12a is rotated at a rotation speed of, for example, 180 rpm by a motor 12b via a stirring rod. The dispersion liquid 3 is agitated by the rotation of the blades 12a, and precipitation of the oxide powder (spread powder) in the dispersion liquid is prevented.

A transportation tube 20 communicating with the tank 10 is connected near the bottom of the tank 10. Tank 10
The tip of the transport tube 20 extending from the
Is connected to a nozzle 24 provided so as to be located above the base plate 5. The metering pump 22 draws the dispersion 3 from the tank 10 at a predetermined flow rate,
The dispersion liquid 3 can be dropped on the base plate 5 from 4. Adjustment of the amount of the dispersion liquid 3 dropped on the base plate 5 (time interval at which the dropping is performed) is performed by adjusting the output of the metering pump 22 or mechanically sandwiching the transport tube 20 to deform it in the radial direction. This is performed by adjusting the flow rate of the dispersion liquid.

In the vicinity of the connection between the tank 10 and the transport tube 20, the transport tube 20 is provided with an air supply capable of intermittently blowing compressed air (air) into the dispersion 3 flowing through the transport tube 20. The tube 26 is connected. The operation of supplying air to the transport tube 20 is as follows.
It is controlled by the opening and closing operation of a solenoid valve 26a provided between the compressed air holding section (air source) and the air supply tube 26. The air supply tube 26 has a drain 26b.
The drain 26b is provided so that all the dispersion liquid 3 in the tank 10 can be discharged by opening a valve at the time of maintenance or the like. The drain 26b is not used during normal operation because the valve is closed.

A discharge tube 28 is connected to the transport tube 20 on the downstream side of the air supply tube 26 (at a position between the air supply tube 26 and the stationary pump 22). The tip of the discharge tube 28 is connected to the tank 10
Extends inside.

Next, a change in the flow of the dispersion liquid 3 in the transport tube 20 caused by the supply of air from the air supply tube 26 will be described with reference to FIG.

As shown in FIG. 2A, in a state where air is not supplied, the dispensing liquid 3 is drawn into the dispensing liquid 3 by the dispensing liquid 22 so that the dispersing liquid 3 moves from the tank 10 to the dispensing pump 22 in a steady state. Flows in

At this time, the dispersion 3 in the tank 10 is constantly stirred by the stirrer 12. However,
It is difficult to completely stir the dispersion 3 in the tank 10 by the stirrer 12, and near the bottom of the tank 10, the oxide powder 3 a precipitates or the oxides in the dispersion do not even precipitate. The concentration of the powder 3a becomes very high.

In this case, the outlet of the tank 10 (the tank 10
In some cases, the oxide powder 3a may accumulate in the transport tube 20 in the vicinity of the connection between the transport tube 20 and the transport tube 20). The accumulation of the powder 3a is performed by the metering pump 22.
This is likely to occur because the amount of the dispersion liquid 3 dropped on the base plate 5 is small and the flow velocity of the dispersion liquid 3 flowing in the transport tube 20 is relatively low. When the accumulation amount of the powder 3a gradually increases, the inside of the transport tube 20 becomes clogged, and the dispersion liquid 3 cannot be appropriately supplied. Further, when the dispersion liquid 3 flows through the transport tube 20, the powder 3 a may accumulate in the transport tube 20, particularly at a location where the flow of the dispersion liquid 3 is slow. Also in this case, the inside of the transport tube 20 may be clogged by the deposited powder 3a.

Therefore, as shown in FIG. 2B, air is intermittently ejected from the air supply tube 26 into the transport tube 20. In the figure, the flow of air is indicated by white arrows. By ejecting the air, a non-stationary reverse flow (backflow) different from the steady flow before the air ejection can be generated in the dispersion 3. In the figure, the flow of the dispersion is indicated by black arrows. As shown, the air is preferably supplied so as to be ejected from the transport tube 20 into the tank 10. In this manner, the oxide powder 3a deposited at the connection portion between the transport tube 20 and the tank 10, which is the portion where the powder is particularly easily deposited, can be pushed back into the tank 10. In addition, tank 1
Since the oxide powder that precipitates at the bottom of the zero can be dispersed in the dispersion, the dispersion can also be stirred.

The supply of air causes a reverse flow in the dispersion 3 flowing from the nozzle 24 to the tank 10 over the entire transport tube 20. The flow velocity of this reverse flow can be set to be higher than the flow velocity of the steady flow. Thereby, the oxide powder 3a that has accumulated and stagnated in the transport tube 20 can be moved and dispersed. Therefore, it is possible to prevent the transport tube 20 from being clogged by the powder 3a. Also, since the dispersion in the transport tube can be homogenized,
It is possible to prevent the concentration of the dispersion liquid 3 dropped from the nozzle 24 onto the base plate 5 from changing over time.

As described above, in this embodiment, by supplying air into the transport tube 20, the transport tube 2
A force that changes the flow of the dispersion 3 is applied to the dispersion 3 flowing in the chamber 0 so that the powder 3a is not unevenly distributed,
Thereby, the dispersion 3 is homogenized.

The oxide powder 3 a deposited in the transport tube 20 is moved by the flow of the dispersion 3 sucked up toward the tank 10. At this time,
Part of the dispersion 3 is discharged from the discharge tube 28.
By providing the discharge tube 28, the dispersion liquid 3 flowing backward flows also to the discharge tube 28,
In the vicinity or the like, the negative pressure of the dispersion liquid 3 does not become extremely negative, and the backflow from the pump 22 to the tank 10 can be more easily generated.

The discharge tube 28 also supplies air which has not been directed from the air supply tube 26 to the tank 10 or air which remains in the transport tube 20 and which may be directed to the metering pump 22 after air is supplied.
It also has the function of discharging from zero. As a result, the air does not reach the metering pump 22, so that the operation of the metering pump 22 is not hindered, and a desired amount of the dispersion liquid 3 can be dropped from the nozzle 24 onto the base plate 5 during the coating operation.

The dispersion liquid and the air discharged from the discharge tube 28 in this manner are supplied to the tank 1 as shown in FIG.
Returned to 0. In this way, the discharged dispersion can be reused, so that no waste occurs.

When the backflow of the dispersion liquid 3 is generated by the supply of air, the dispersion liquid 3 is drawn from the nozzle 24, so that the dispersion liquid 3 cannot be dropped on the base plate 5. Therefore, the supply of the air is performed during a period in which the application operation to the base plate 5 is not performed (for example, after the application of one base plate is completed, until the next base plate is carried to the application device 1). It is desirable to be executed during

Next, reference is made to FIG. FIG. 3 shows a connection form of the transport tubes 20 and the like in a case where the dispersion liquid is applied to the base plate from the plurality of nozzles 24 using the plurality of transport tubes 20. As shown, the transport tube 20
If the air supply tube 26 and the discharge tube 28 are connected to each other, it is possible to supply air from the air supply tube 26 to each transport tube 20 and discharge the dispersion liquid and the air from the discharge tube 28. Is possible. Therefore, it is possible to appropriately remove or disperse the powder accumulated in each transport tube 20 and to prevent clogging in each transport tube and uneven concentration of the dispersion liquid.

Next, referring to FIGS. 4 and 5, a spreading device 30 for spreading the dispersion liquid dropped on the base plate.
Will be described.

The spreading device 30 shown in FIG. 4 includes a plurality of rollers 3 provided corresponding to the nozzles 24 for applying the dispersion liquid dropped from the plurality of nozzles 24 onto the base plate 5.
2 is provided. The spreading device 30 has a limited area where the molded body on the base plate 5 is placed, and is used when it is sufficient to apply the dispersion only to the limited area. 32. When it is necessary to apply the dispersion over the entire surface of the base plate, a single roller having a length corresponding to the width of the base plate may be used.

Each roller 32 is desirably mounted so as to be vertically movable within a predetermined range with respect to the fixed portion 34 and is designed to be mounted on the base plate 5 by its own weight. The surface of each roller 32 is preferably made of a water-absorbing material such as felt.

As shown in FIG. 5A, after the dispersion liquid 3 is dropped onto the base plate 5 from the nozzle 24, the base plate 5 is moved with respect to the rollers 32 by the transfer device 8, and as shown in FIG.
(B) As shown in FIG.
Is placed on the base plate 5 while absorbing the excess dispersion liquid 3.
Spread in a uniform thickness. Since the roller 32 is placed on the base plate 5 by its own weight, even if the base plate itself has a slight deformation such as a warp or a variation in thickness, the dispersion liquid 3 is uniformly deposited on the base plate 5. Can be applied. When a plurality of base plates 5 are continuously coated,
Even if there is some variation in the thickness of each base plate, the dispersion 3 can be applied to each base plate with a uniform thickness.

According to the dispersion liquid applying apparatus 1 of the present embodiment,
Even in the case of using a dispersion in which a powder formed of an oxide such as a rare earth oxide is dispersed in a liquid such as alcohol, the concentration of the tube is relatively low while preventing the tube from being clogged by the sedimentation of the powder. A uniform dispersion can be applied on the base plate at a uniform thickness.

Hereinafter, the flow of the operation of the dispersion liquid applying apparatus will be described with reference to FIGS. 6 and 7.

As shown in FIG. 6, the dispersion apparatus shown in FIG.
And a spreading device 30 having a roller 32 for spreading the dispersion liquid 3 on the base plate 5.

The spreading device 30 is connected to a traversing cylinder for moving the spreading device 30 in the horizontal direction. The traverse cylinder is provided with a forward sensor for detecting that the spreading device 30 has moved to the forward position, and a retreat sensor for detecting that the spreading device 30 has moved to the retreat position. .

The roller 32 of the spreading device 30 is connected to an elevating cylinder for moving the roller 32 in the vertical direction. The elevating cylinder is provided with an ascending sensor for detecting that the roller 32 has moved to the ascending position and a descending sensor for detecting that the roller 30 has moved to the ascending position.

Further, the dispersion liquid applying apparatus has a base plate sensor for detecting whether or not the base plate 5 conveyed by the conveying device 8 (see FIG. 1) is at a predetermined position in the conveying path. I have.

As shown in FIG. 7, in the dispersion liquid coating apparatus having the above-described structure, first, a dispersion medium and an oxide powder having a predetermined ratio measured in advance are charged into a tank 10.
The stirrer is operated (Step S40). In addition, start operation of the metering pump in a state where the dispersion is stirred,
Thereby, the dispersion liquid 3 from the tank 10 is dropped via the nozzle 24.

Next, when it is confirmed by the base plate sensor that the base plate 5 has been carried to a predetermined place (step S42), the spreader 30 is moved to the forward position by the traversing cylinder (step S44). ). When it is confirmed by the advance sensor that the spreader 30 has reached the advance position (step S46), the roller 32 is moved to the descending position using the elevating cylinder (step S4).
8). Whether the roller 32 has moved to the lowering position is determined by a lowering sensor connected to the lifting cylinder (step S50).

The spreading device 30 can appropriately spread the dispersion liquid 3 dropped on the base plate 5 when the spreading device 30 moves to the forward position and the roller 32 moves to the descending position. . This is because when the spreading device 30 is in the forward position even during a time other than the coating process, it becomes a hindrance when the robot 9 (see FIG. 1) moves the base plate that has already been coated to another place. Because there is. If the roller 32 is at the lowered position when the base plate is not present, the roller 32 and the transport device 8 (see FIG. 1)
This is because the rollers 32 may come into contact with each other, and the rollers 32 may be worn away. Note that, as described above, the spreader 30
When the roller 32 is moved, the nozzle 24 for dropping the dispersion liquid is desirably fixed to the roller support member so that the relative position with respect to the roller 32 does not change.

The roller 32 is moved to the position as described above, and the base plate 5 is moved by the transport device 8, whereby the dispersion liquid is applied onto the base plate 5 (step S).
52). The application of the dispersion liquid is performed until the base plate sensor determines that the base plate 5 does not exist (that is, the dispersion liquid is applied to the entire base plate) (step S54).
After the application step, the roller 32 is moved to the ascending position using the elevating cylinder and the ascending sensor connected thereto (steps S56 and S58). Further, the spreading device 30 is moved backward using the traversing cylinder (step S60).

At this time, the opening / closing operation of the electromagnetic valve 26a attached to the air supply tube 26 is performed a plurality of times (up to 20 times).
Times) repeatedly to supply air intermittently into the transport tube (step S62). As a result, an unsteady backflow is generated in the dispersion, and the precipitate of the oxide powder in the transport tube can be dispersed.

Although the metering pump is operating while the air is being supplied, the dispersion liquid in the transport tube has a reverse flow, so that the dispersion liquid is not dropped from the nozzle 24. Therefore, after the step of applying the dispersion liquid to the base plate (S54) is completed as described above, the air supply step (step S54) is performed.
62) is set.

Thereafter, it is confirmed by the retreat sensor that the spreader 30 has moved to the retreat position (step S64), and one application operation is completed. Further, when the base plate to be applied is transferred to the coating device by the transfer device, the coating device returns to step S42 and
The coating operation of the next base plate is performed.

(Embodiment 2) Hereinafter, the configuration of the dispersion liquid applying apparatus of Embodiment 2 will be described with reference to the drawings. In addition,
In the drawings, members having the same configuration as the members of the dispersion liquid applying apparatus of Embodiment 1 are given the same reference numerals.

First, reference is made to FIG. The dispersion liquid coating apparatus 201 according to the second embodiment includes a tank 10 containing a dispersion liquid 3 in which an oxide powder such as a rare earth oxide is dispersed in a volatile liquid such as alcohol, and the tank 10 on the base plate 5. A transport tube 220 for carrying the dispersion 3 and a transport tube 220
End (end opposite to the side connected to tank 10)
And a nozzle 224 connected to the Tank 10
In the same manner as in the first embodiment, a stirrer 12 for stirring the dispersion 3 is attached.

An air supply tube 226 provided with a valve 226a is connected to the nozzle 224.
By opening a and supplying air to the nozzle 224, the dispersion liquid 3 can be jetted onto the base plate 5. The diameter of the injection port of the nozzle 224 is, for example, 2 mm, and the discharge pressure of the dispersion 3 from the nozzle 224 is, for example, 2 kg / cm.
² As the nozzle for ejecting the dispersion by supplying the air as described above, for example, a Lumina automatic spray gun PR series manufactured by Fuso Seiki Co., Ltd. can be used.

The dispersion liquid coating device 201 is arranged close to a shot blaster 207 for cleaning the surface of the sintering base plate 5. The shot blaster 207 includes a powder emitting unit 272 that emits the powder 70 formed of alumina or the like. The powder blasting unit 207 moves the powder 70 against the upper surface of the base plate 5 moved in the direction indicated by the arrow P by the transport device 8.
Collide. The powder emitting unit 272 is fixed to a shaft 274 extending along the moving direction of the base plate 5. A rotating device (not shown) can rotate the shaft 274 in either the forward or reverse direction, and thereby can swing the powder emitting unit 272 around the shaft 274. The shot blaster 207 can clean the entire upper surface of the base plate 5 by emitting the powder while swinging the powder emission unit 272 while the base plate 5 is moving.

As shown in FIG. 9, the shaft 274 is provided with a nozzle 224 for jetting the dispersion 3 onto the base plate 5.
22 is fixed. Thus, when the shaft 274 is rotated to swing the powder emitting unit 272, the nozzle 222 is also swung. Therefore, FIG.
As shown in (2), the nozzle 224 can move on the base plate 5 in a direction substantially orthogonal to the traveling direction of the base plate 5, and spray the dispersion 3 over the entire upper surface of the base plate 5. Can be.

At this time, the transport tube 220 that carries the dispersion 3 to the nozzle 224 is also shaken as the nozzle 224 moves. Therefore, a mechanical force (sway) is applied to the dispersion 3 flowing in the transport tube 220. At this time, since the litter in the dispersion liquid 3 can move in the transport tube 220, the dispersion liquid 3 is homogenized and the litter is unevenly distributed in the dispersion liquid to prevent the transportation tube 220 from being clogged. You.

Further, in order to more reliably prevent the deposition of the litter in the transport tube 220, the transport tube 220
(Not shown) may be provided. It is preferable that such a vibrating device effectively vibrates particularly a place where the litter tends to settle in the transport tube, and is attached, for example, in the vicinity of a connection portion between the tank 10 and the transport tube 220.

In the present embodiment, the dispersion liquid 3 is always jetted from the nozzle 224. In this case, when the dispersion liquid 3 is continuously applied to the plurality of base plates 5, the dispersion liquid 3 is jetted even when the base plate 5 does not exist below the nozzle 224. In order to prevent this, it is preferable not to stop the injection of the dispersion 3.

[Manufacturing Method of Rare Earth Sintered Magnet] Hereinafter, RT- (M) using the dispersion coating apparatus 1 or 201 will be described.
A method for producing a -B rare earth sintered magnet will be described.

In order to manufacture an RT- (M) -B-based magnet, first, an RT-
A slab of the (M) -B alloy is prepared. Strip casting is disclosed, for example, in US Pat. No. 5,383,978. Specifically, Nd: 30 wt%, B: 1.
0 wt%, Al: 0.2 wt%, Co: 0.9 wt%,
An alloy having a composition of Cu: 0.2 wt%, the balance being Fe and unavoidable impurities is melted by high frequency melting to form a molten alloy. After maintaining this molten alloy at 1350 ° C,
The alloy melt is quenched by the single roll method and the thickness is 0.3m
m flake alloy is obtained. 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. /
Seconds, the degree of supercooling is 200 ° C.

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

To the alloy powder thus obtained, 0.3% by weight 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 in a magnetic field 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 .

On the other hand, a sintering base plate on which a compact is to be placed is prepared. The sintering base plate is formed of a high melting point metal such as stainless steel or molybdenum, and is preferably formed of molybdenum. Molybdenum is suitable as a material for the base plate for sintering because it has low reactivity with a compact containing a rare earth metal element, has good thermal conductivity, and has good heat resistance.

As will be described later, an average particle size of 1 μm to several tens μm (particularly 1 μm to 2 μm)
It is preferable to use an oxide powder having a particle diameter of 0 μm), but when using an oxide powder having such a particle size, the surface roughness Ra (average roughness) of the base plate for sintering is 0.1 μm to 150 μm. It is preferable that the thickness is 0.1 μm to 10.0 μm.
m is desirable. If the surface roughness Ra is less than 0.1 μm, the unevenness on the surface of the base plate is too small, and the powder moves (slids) on the base plate, so that it becomes difficult to spread the spread powder uniformly on the base plate. Further, when the surface roughness Ra exceeds 150 μm, the powder does not function as a spreading powder due to too large irregularities, and the friction between the base plate and the molded body increases. This is because even if welding does not occur, the sintered body may be cracked. For the same reason, it is desirable that the surface roughness Rmax (maximum roughness) of the sintering base plate be 1 μm to 300 μm. The surface roughness Ra and Rmax of the base plate can be measured in accordance with JIS standards by using, for example, a small surface roughness measuring device (Surftest SJ-301) manufactured by Mitutoyo Corporation.

While the sintering base plate is repeatedly used, the surface roughness of the base plate gradually increases due to, for example, the inability to remove the residue attached to the base plate after sintering. However, as described above, the roughness Ra of the base plate is 150 μm.
If the roughness is not more than 300 μm and the roughness Rmax is not more than 300 μm, it is possible to appropriately prevent the occurrence of cracks in the sintered body by laying the spreading powder. In addition, you may make it change the size of spreading powder according to the magnitude | size of the surface roughness of a base plate.

Next, using a dispersion coating apparatus 1 or 201, a dispersion in which an oxide powder is dispersed in a liquid is uniformly coated on a sintering base plate. It is desirable to use a volatile liquid such as ethanol or methanol as the dispersion medium (liquid). When a volatile liquid is used, the time for drying the base plate after applying the dispersion liquid to the base plate can be shortened. Ethanol is particularly preferable because of its low cost. Further, it is desirable that the oxide powder be formed of a material having stable properties at the sintering temperature and low reactivity with the compact containing the rare earth metal element. Examples of such a material include rare earth oxides such as neodymium oxide and yttrium oxide, and oxides such as zirconia and alumina.

The average particle size of the oxide powder used as the spreading powder is preferably 1 μm to several tens μm. If the particle size of the powder is smaller than 1 μm, the powder may enter between the irregularities formed on the surface of the base plate and may not function as a laying powder. Also,
If it is larger than tens of μm, it may not be uniformly dispersed in the dispersion. Furthermore, if the particle size of the bedding powder is too large,
There is also a problem that the inside of the transport tube of the dispersion liquid application device is easily clogged with the litter. Note that a more preferable range of the average particle size of the oxide powder is 1 μm to 20 μm, and a more preferable range is 1 μm to 10 μm.

The concentration of the dispersion is desirably 10 g / l or more (10 g of powder per 1 liter of the dispersion medium). When the concentration is less than 10 g / liter,
This is because the amount of the powder spread on the base plate becomes relatively small, and the effect as the spread powder may not be obtained.
The concentration of the dispersion is desirably 500 g / liter or less. If the concentration of the dispersion is too high, clogging of the transport tube of the coating apparatus is likely to occur, and the powder will be consumed unnecessarily much. The concentration of the dispersion is more preferably 200 g / liter or more and 500 g / liter or less.

After the dispersion is applied by the dispersion applying apparatus 1 or 201, the volatile dispersion medium is preferably evaporated. Thereby, the oxide powder in the dispersion can be spread as a spread powder on the sintering base plate. If the dispersion liquid coating apparatus 1 or 201 is used, the time required for the coating step can be reduced without the need for labor, and the spread powder can be evenly spread on the base plate.

On the sintering base plate on which the laying powder has been laid, a number of compacts produced by using a press as described above are arranged. Next, the plurality of sintering base plates on which the formed bodies are arranged are accommodated in a sintering case in a state of being stacked at intervals by using a spacer. The sintering case is composed of, for example, a box and a lid put on the box, and by using the sintering case, the molded body is sintered in an exposed state in a sintering furnace. prevent. When the sintering case is not used, the rare earth element of the compact may be oxidized by oxygen present in the furnace, and in this case, the properties of the magnet are greatly deteriorated.

This sintering case is transported to a sintering device,
After inserting the sintering case into the preparation room provided at the entrance of the sintering device and sealing the preparation room, to prevent oxidation,
The preparation chamber is evacuated until the atmospheric pressure becomes about 2 Pascal. Next, the sintering case is transported to the binder removal chamber, where the binder removal treatment (temperature: 250 to 600 degrees,
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. During the binder removal treatment, various gases such as organic gas and water vapor are generated from the molded body. Therefore, it is desirable that a getter capable of absorbing these gases be placed in the sintering case in advance.

After the binder removal treatment, the sintering case is transported to the sintering chamber and subjected to 1000 g in an argon atmosphere.
焼 結 1100 ° C. for about 2 to 5 hours. At this time, the dispersion coating device 1 or 20 is placed on the sintering base plate.
Since the spreading powder is spread evenly using No. 1, the molded body is prevented from being welded to the base plate, and the possibility of cracking or breakage of the sintered body can be reduced. In addition, the compact is shrunk during sintering, but since the laying powder is evenly spread on the base plate, the compact shrinks evenly,
Undesirable deformation is prevented.

Thereafter, the sintering case is transferred to a cooling chamber, where it is subjected to a cooling process until the temperature of the sintering case is reduced to about room temperature. The cooled sintered body is inserted into an aging furnace, and a normal aging process is performed. The aging treatment is performed, for example, at a pressure of an atmospheric gas such as argon of about 2 Pascal and at a temperature of 400 to 600 ° C. for about 3 to 7 hours.

The method for producing a rare earth sintered magnet of the present invention is not limited to a 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, when 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 a transition metal element containing Fe, Co and Ni. When T is less than 67 at%, the 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 of the demagnetization curve also deteriorates. Therefore, the content of T is preferably in the range of 67 to 85 at%. Note that T may be composed only of Fe, but the addition of Co increases the Curie temperature and improves heat resistance. Preferably, at least 50 at% of T is occupied by Fe. When the ratio of Fe is below 50at%, because the saturation magnetization itself Nd ₂ Fe _{1 4} B type compound is reduced.

B is boron or a compound 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 decreases 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%.

An additive element M may be added for the purpose of improving the magnetic properties and corrosion resistance of the powder. Al, Ti, Cu, V, Cr, Ni, G
At least one element selected from the group consisting of a, Zr, Nb, Mo, In, Sn, Hf, Ta, and W can be suitably used. Such an additive element M may not be added at all. When adding, add 10at%
It is preferable to set the following. If the addition amount exceeds 10 at%, not the ferromagnetism but the second phase will precipitate and the magnetization will decrease.

Although the method for producing the RT- (M) -B sintered magnet has been described above, the sintering base plate on which the spreading powder is uniformly spread by the dispersion coating apparatus 1 or 201 is described. Can be used to produce a samarium-cobalt sintered magnet. In the production of the rare earth sintered magnet in which a liquid phase is generated at the time of sintering, the dispersion liquid coating apparatus 1 or 201
By using the sintering base plate on which the laying powder is spread by using the method described above, there is no welding with the base plate, so that the sintered body can be prevented from being damaged or deformed.

Example 1 57.2 mm × 44.7 mm × 18.4 mm was obtained by using a sintering base plate on which laying powder (oxide powder) was spread by the dispersion liquid coating apparatus 1 of the first embodiment.
400 (R-Fe-B) sintered magnets having dimensions of (weight 335 g) were produced. As the sintering base plate, a plate material (surface roughness Ra = 0.1 μm) formed from a Mo alloy was used. In addition, a powder of a rare earth oxide having an average particle size of 3 μm represented by R ₂ O ₃ was used as the spreading powder.
150 g of rare earth oxide powder was dispersed in 3 liters of ethanol in the above tank 10. The discharge pressure of the dispersion liquid at the nozzle 24 of the dispersion liquid coating apparatus 1 is 2 k.
The output of the pump 22 and the like were set so as to be g / cm ² .

When sintering was performed at a temperature of 1045 ° C. in an argon atmosphere, one of 400 sintered bodies cracked. In addition, significant deformation was recognized in 2 out of 400 pieces.

(Comparative Example 1) An R-Fe-B based sintered magnet was manufactured under the same conditions as in Example 1 except that no spreading powder was spread.
00 pieces were produced. In the sintered body, 20 out of 400 cracks occurred.

The R-Fe-B based sintering was performed under the same conditions as in the example, except that the dispersion was applied to the base plate by hand without using the dispersion coating apparatus 1. 400 magnets were produced. Among the sintered compacts, 4 out of 400 sintered bodies showed significant deformation.

(Example 2) Using a sintering plate on which laying powder (oxide powder) was spread by the dispersion liquid coating apparatus 201 of Embodiment 2, 57.2 mm x 44.7 mm x 18.4 m was used.
400 (R-Fe-B) sintered magnets having a size of m (weight 335 g) were produced.

As the sintering base plate, a plate material formed from a Mo alloy was used. The surface roughness Ra of the sintering base plate is 0.1
sintering base plate (base plate 1) having a surface roughness Rmax of 1 μm and a sintering base plate (base plate 2) having a surface roughness Ra of 150 μm and a surface roughness Rmax of 300 μm. ) And were used.

[0112] Further, as the spreading powder, N having an average particle size of 1 µm was used.
Dispersion coating device 2 using powder formed from d-oxide
300 g of rare earth oxide powder was dispersed in 1 liter of ethanol in the above tank 10. In addition, the discharge pressure of the dispersion liquid at the nozzle 224 of the dispersion liquid application device 2 is 2
Air was supplied to the nozzle 224 so as to be kg / cm ² .

When sintering was performed at a temperature of 1045 ° C. in an argon atmosphere, cracks occurred in the sintered body in 0 of the 400 base plates 1. In addition, 4
One out of 00 pieces.

(Comparative Example 2) The surface roughness Ra was 200 μm,
The surface roughness Rmax was 400 μm and the surface roughness was relatively large (Ra> 150 μm, Rmax> 300 μm).
-400 Fe-B based sintered magnets were produced. Of the sintered compacts, cracks occurred in 10 out of 400 pieces.

From the results of Example 2 and Comparative Example 2, by setting the surface roughness of the sintering base plate in an appropriate range, the litter works effectively, and the generation of cracks in the sintered body is reduced. It can be seen that it can be significantly reduced.

[0116]

According to the dispersion coating apparatus of the present invention, a dispersion obtained by dispersing an oxide powder such as a rare earth oxide in a liquid such as alcohol is uniformly coated on a sintering base plate. Therefore, the spreading powder can be evenly spread on the sintering base plate.

By using the sintering base plate on which the laying powder is evenly spread as described above, the compact placed on the sintering base plate is damaged or deformed during sintering. Is prevented, and the manufacturing efficiency of the magnet can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a dispersion liquid application device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a change in the flow of a dispersion liquid flowing through a transport tube. FIG.
(B) shows when air is supplied.

FIG. 3 is a diagram showing a connection configuration of tubes when a plurality of transport tubes are used.

FIG. 4 is a perspective view showing a state in which a dispersion liquid is applied on a sintering base plate.

FIG. 5 is an enlarged sectional view showing a state in which a dispersion liquid is applied onto a sintering base plate.

FIG. 6 is a diagram schematically showing a dispersion liquid application device according to the first embodiment of the present invention.

FIG. 7 is a flowchart showing an operation of the dispersion liquid application device shown in FIG.

FIG. 8 is a diagram illustrating a configuration of a dispersion liquid application device according to a second embodiment of the present invention.

9 is a perspective view showing a part of the dispersion liquid application device shown in FIG.

10 is an enlarged front view showing a state in which a dispersion liquid is applied to a sintering base plate by the dispersion liquid application apparatus shown in FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dispersion liquid applicator 3 Dispersion liquid 5 Sintering base plate 7 Shot blaster 8 Transfer device 9 Robot 10 Tank 12 Stirrer 20 Transport tube 22 Metering pump 24 Nozzle 26 Air supply tube 28 Discharge tube 30 Spreading device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B05D 7/24 302 B05D 7/24 302A B22F 3/00 B22F 3/00 F 3/10 3/10 M / / C04B 35/64 C04B 35/64 K (72) Inventor Tsuyoshi Wada 1850 Minato, Wakayama-shi, Wakayama Prefecture Sumitomo Special Metals Co., Ltd. Wakayama Office F-term (reference) 4D075 AC02 AC47 AC54 AC77 BB65X DA06 DC16 DC19 EA10 EA31 EB31 EB01 4F041 AA02 AB01 BA01 BA42 4F042 AA02 BA16 CA06 CB02 CB19 DA01 DD09 DF15 4K018 AA27 BA18 CA11 DA00 DA39 KA45 5E062 CC02 CC03 CD04 CF04

Claims (27)

[Claims] 1. An apparatus for applying a dispersion liquid in which an oxide powder having a specific gravity greater than that of a liquid is dispersed in a liquid on a base plate for magnet sintering, comprising: a container accommodating the dispersion liquid; A stirrer for stirring the dispersion liquid contained in the container, a transfer path for transferring the dispersion liquid from the container to the base plate, and mechanically moving at least a part of the dispersion liquid flowing through the transfer path. A homogenizer for homogenizing the dispersion by applying a force. 2. The dispersion liquid application device according to claim 1, wherein the homogenization device generates an unsteady flow in at least a part of the dispersion flowing through the transfer path. 3. The dispersion liquid applying apparatus according to claim 2, wherein the unsteady flow is a flow in a direction opposite to a direction from the container to the base plate. 4. The dispersion liquid applying apparatus according to claim 3, further comprising a discharge path connected to the transfer path and capable of discharging the dispersion liquid flowing in the opposite direction. 5. The apparatus according to claim 2, wherein the homogenizing device is capable of ejecting a fluid into the dispersion flowing through the transfer path.
5. The dispersion liquid application device according to any one of items 1 to 4. 6. The dispersion liquid application device according to claim 5, wherein the fluid is air. 7. The dispersion liquid applying apparatus according to claim 5, further comprising a discharge path connected to the transfer path and capable of discharging at least a part of the fluid. 8. The dispersion liquid applying apparatus according to claim 4, wherein the discharge path extends into the container. 9. The apparatus according to claim 2, wherein the homogenizer can generate the unsteady flow in the dispersion in the vicinity of a connection between the transfer path and the container. The dispersion coating apparatus according to any one of the preceding claims. 10. A metering pump provided on the transfer path downstream of the homogenizer.
10. The dispersion coating device according to any one of items 1 to 9. 11. The dispersion liquid applying apparatus according to claim 2, further comprising a spreading device that spreads the dispersion liquid supplied onto the base plate via the transfer path on the base plate. 12. The dispersion applying device according to claim 11, wherein the spreading device includes a water-absorbing roller provided so as to be in contact with the surface of the base plate. 13. The dispersion application device according to claim 1, wherein the homogenization device applies a mechanical force to the transfer path. 14. The dispersion liquid application device according to claim 13, wherein the homogenization device swings the transfer path. 15. A base plate cleaning device for cleaning the base plate before applying the dispersion liquid, wherein the base plate cleaning device causes the powder to impinge on the base plate. A swinging device for swinging the body emitting portion and the powder emitting portion, wherein the homogenizing device is connected to the swinging device of the bed plate cleaning device, and the movement of the swinging device 15. The dispersion liquid application device according to claim 14, wherein the transfer path is swung. 16. A nozzle connected to an end of the transfer path opposite to the container side, and a gas supply path connected to the nozzle, wherein the gas is supplied from the gas supply path to the nozzle. The dispersion liquid application device according to any one of claims 13 to 15, wherein the dispersion liquid is sprayed on the base plate using the gas. 17. The dispersion liquid applying apparatus according to claim 1, wherein the liquid is formed from a volatile liquid. 18. The dispersion liquid applying apparatus according to claim 1, wherein the oxide powder is formed of a rare earth oxide powder. 19. A step of preparing a base plate for magnet sintering, and a dispersion obtained by dispersing the oxide powder using the dispersion coating apparatus according to claim 1. Applying a compact formed by pressing the alloy powder for a rare earth magnet onto the base plate to which the dispersion has been applied; and placing the compact on the base plate. And sintering the formed compact. 20. A surface roughness Rmax of the base plate is 1 μm.
20. The method for producing a rare earth magnet according to claim 19, wherein the diameter is not less than 300 μm. 21. A surface roughness Ra of the base plate is 0.1 μm.
The method for producing a rare-earth magnet according to claim 19 or 20, wherein the thickness is at least 150 µm. 22. The method of manufacturing a rare earth magnet according to claim 19, wherein the concentration of the dispersion is 200 g / liter or more and 500 g / liter or less. 23. A step of preparing a base plate for magnet sintering; a step of applying a dispersion of a powder of an oxide having a specific gravity larger than that of the liquid to a liquid, on the base plate; A step of placing a compact formed by pressing the alloy powder for a rare earth magnet on the base plate on which the dispersion is applied, and a step of sintering the compact placed on the base plate A method for producing a rare earth magnet, wherein the surface roughness Rmax of the base plate is 1 μm or more and 300 μm or less 24. A step of preparing a base plate for magnet sintering, and a step of applying a dispersion liquid in which an oxide powder having a specific gravity greater than that of the liquid is dispersed in a liquid, on the base plate; A step of placing a compact formed by pressing the alloy powder for a rare earth magnet on the base plate to which the dispersion is applied, and a step of sintering the compact placed on the base plate A method for producing a rare earth magnet, wherein the surface roughness Ra of the base plate is 0.1 μm or more and 150 μm or less. 25. The method for producing a rare earth magnet according to claim 23, wherein the concentration of the dispersion is 200 g / liter or more and 500 g / liter or less. 26. An average particle size of the powder is 1 μm to 20 μm.
The method for producing a rare earth magnet according to any one of claims 23 to 25, wherein the diameter is μm. 27. A rare earth magnet manufactured by the manufacturing method according to claim 19.