JP4513977B2 - Rare earth sintered magnet coating method, painting tray - Google Patents

Description

  The present invention relates to a method for coating a rare earth sintered magnet.

Rare earth sintered magnets such as neodymium-based sintered magnets represented by R-T-B (R is one or more rare earth elements, T is Fe or Fe and Co) are oxidized or used in the atmosphere used. It is easy to be hydroxylated, and if this causes corrosion on the surface, the magnetic properties will be deteriorated and uneven.
Therefore, conventionally, the magnet surface has been painted by various surface treatment methods such as plating and painting. Coatings by painting are frequently used except for special applications because they are excellent in oil resistance, chemical resistance and salt spray resistance and are inexpensive.
As a technique for coating, for example, Patent Document 1 discloses a configuration in which an oxidation-resistant resin film is formed on the surface of a permanent magnet, and Patent Document 2 describes a coating liquid using a thermosetting acrylic resin or epoxy resin. The coating configuration is shown.

JP-A-60-63901 JP 2000-331811 A

When painting, the control of the film thickness is very important. This is because if the film thickness is too small, the required conditions such as sufficient corrosion resistance cannot be satisfied, and conversely if the film thickness is too large, the magnetic properties are deteriorated.
In order to perform coating by painting, there is a spray method in addition to the dipping method described in Patent Document 2. As described in Patent Document 2, in the case of the dip method, since the film thickness distribution in each magnet is likely to be non-uniform, the film thickness formed on the magnet surface is made uniform by using a centrifugal method or the like. It is necessary to blow off the excess paint while trying. For this reason, the uniformity of the film in one magnet solid cannot be maintained by this centrifugation method. In addition, it takes extra work for one step, and when a large number of magnets are processed at once by a centrifugal method, the acting centrifugal force differs between the magnet located on the inner circumference side and the magnet located on the outer circumference side. Thus, there will be a difference in film thickness within the same lot.
Further, in the case of rare earth sintered magnets, sparks may be generated when the magnets are in direct contact with each other. Therefore, the dipping method in which a large number of magnets are accommodated in a basket and immersed in a paint is not preferable in this respect.

On the other hand, in the spray method, a large number of magnets are arranged on a net-like tray and the surface is coated by spraying paint from an oblique upper side with a nozzle, so that the problem of the dip method as described above can be avoided. At this time, in the magnet located in the outermost peripheral part on a tray, there exists a problem that the film thickness of a film will become smaller than the upper surface in the side surface which faces an outer peripheral side.
The present invention has been made on the basis of such a technical problem, such as a coating method of a rare earth sintered magnet capable of achieving a uniform film thickness even in a magnet located on the outermost peripheral portion of a tray in a spray method. The purpose is to provide.

The inventors have sought the cause of the film thickness of the side surface facing the outer peripheral side being smaller than the upper surface in the magnet located at the outermost peripheral part on the tray.
Initially, the spraying time of the paint by the spray is considered that the time that the paint is sprayed on the side of the magnet located on the outermost peripheral part is shorter than the magnets of other parts, because of the relationship of the spray operation to the magnet on the tray I tried to double. As a result, although the film thickness on the side surface of the magnet could be secured by this, the film thickness of the film on the upper surface of the magnet was correspondingly larger than the magnets at other positions.
When magnets are arranged on a tray, the magnetic pole surface of the magnet often becomes the upper surface, so it is not preferable that the film thickness of the upper surface be excessive. From the viewpoint of magnetic characteristics, it is preferable that the film thickness of the magnetic pole face of the magnet be minimized.

As a result of further studies, it was found that in the magnets other than the outermost peripheral portion, the paint sprayed on the upper surface of the adjacent magnet rebounds and adheres to the side surface of the magnet.
The rare earth sintered magnet coating method of the present invention made from such knowledge is a method of forming a film on the surface of the rare earth sintered magnet by spraying a paint on the surface of the rare earth sintered magnet, With the step of arranging the rare earth sintered magnets side by side on the tray and the stepped or protruding part protruding upward on the outer peripheral side of the rare earth sintered magnet located at the outermost periphery among the plurality of rare earth sintered magnets And a step of spraying the paint.
In the process of spraying paint, the outer peripheral side of the rare earth sintered magnet located on the outermost circumference on the tray is used to form a stepped portion or a convex portion on the outer peripheral side of the rare earth sintered magnet located on the outermost circumference. It is preferable to set a dummy member on the surface. In addition to this, a stepped portion or a convex portion may be formed on the tray on the outer peripheral side of the rare earth sintered magnet located on the outermost periphery.
In the step of spraying the paint, the paint is sprayed obliquely from above on the rare earth sintered magnet on the tray .
In this way, when the paint is sprayed on the outer peripheral side of the rare earth sintered magnet located on the outermost periphery, with the stepped or protruding portion protruding upward, the rare earth sintered magnet located on the outermost periphery, The paint adheres well to the side facing the outer periphery. This is mainly because the paint rebounds on the upper surface of the stepped part or the convex part, and the paint adheres to the side surface facing the outer peripheral side of the rare earth sintered magnet located on the outermost periphery.
Further, in the step of spraying the paint, the film thickness on the side surface of the rare earth sintered magnet can be made larger than the film thickness of the paint film on the upper surface of the rare earth sintered magnet.
Here, the rare earth sintered magnet is a rectangular parallelepiped of 65 × 14 × 6 mm, the stepped portion or convex portion has the same size as the rare earth sintered magnet, and the rare earth sintered magnet and the stepped portion or convex portion are spaced from each other by 10 mm. It can be arranged side by side so as to be less than 70 mm, the height of the stepped portion or convex portion can be an area of 5 mm to 8 mm, and the width of the stepped portion or convex portion can be 10 mm or more.

The present invention is not limited to rare earth sintered magnets, and can be applied to various other objects to be painted. That is, the present invention is a method of spraying paint on the surface of an object to be coated, the step of arranging a plurality of objects to be arranged on a tray, and a coating located on the outermost periphery among the plurality of objects to be coated And a step of spraying a paint in a state where a stepped portion or a protruding portion protruding upward is formed on the outer peripheral side of the object.
At this time, in the step of spraying the paint, the paint is rebounded on the upper surface of the stepped portion or the convex portion by forming a stepped portion or a convex portion on the outer peripheral side of the object to be coated located on the outermost periphery. The coating film thickness on the side surface can be ensured by adhering the paint to the side surface facing the outer peripheral side of the coating object located at the outermost periphery.

The present invention is a tray used for forming a film on the surface of a rare earth sintered magnet by spraying paint on the surface of the rare earth sintered magnet, and when a plurality of rare earth sintered magnets are arranged on the upper surface, A stepped portion or convex portion that protrudes upward is formed on the outer peripheral side of the rare earth sintered magnet located at the outermost periphery, and the stepped portion or convex portion is formed when spraying paint from obliquely above, A coating tray characterized in that the coating material is rebounded on the upper surface of the stepped portion or the convex portion, and the coating material adheres to the side surface facing the outer peripheral side of the rare earth sintered magnet located on the outermost periphery. You can also.

  According to the present invention, the spray is sprayed in the spray method by spraying the paint in a state in which the stepped portion or the protruding portion protruding upward is formed on the outer peripheral side of the rare earth sintered magnet or the coating object on the outermost periphery. It is possible to ensure the film thickness of the side surface even in the magnet and the coating object located at the outermost peripheral part of the film.

The present invention will be described in detail based on the following embodiments.
First, a method for manufacturing a rare earth sintered magnet will be described. First, the magnet to which the present invention is applied will be described.
The present invention is preferably applied to a neodymium-based sintered magnet represented by R-T-B (R is one or more rare earth elements and T is Fe or Fe and Co). Of course, the present invention is not limited to this, and it is also effective to apply the present invention to other rare earth sintered magnets.

The RTB-based sintered magnet contains 25 to 37 wt% of rare earth element (R). Here, R has a concept including Y. Therefore, one or two of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Selected from more than species. If the amount of R is less than 25 wt%, the R ₂ T ₁₄ B phase, which is the main phase of the RTB-based sintered magnet, is not sufficiently generated, and α-Fe having soft magnetism is precipitated and retained. The magnetic force is significantly reduced. On the other hand, when R exceeds 37 wt%, the volume ratio of the R ₂ T ₁₄ B phase, which is the main phase, decreases, and the residual magnetic flux density decreases. Further, R reacts with oxygen, the amount of oxygen contained increases, and accordingly, the R-rich phase effective for the generation of coercive force decreases, leading to a decrease in coercive force. Therefore, the amount of R is set to 25 to 37 wt%. A desirable amount of R is 28 to 35 wt%.

Further, the RTB-based sintered magnet to which the present invention is applied contains 0.5 to 4.5 wt% of boron (B). When B is less than 0.5 wt%, a high coercive force cannot be obtained. On the other hand, when B exceeds 4.5 wt%, the residual magnetic flux density tends to decrease. Therefore, the upper limit of B is set to 4.5 wt%. A desirable amount of B is 0.5 to 1.5 wt%, and a more desirable amount of B is 0.8 to 1.2 wt%.
The RTB-based sintered magnet to which the present invention is applied can contain Co in an amount of 5.0 wt% or less (excluding 0), preferably 0.1 to 3.0 wt%. Co forms the same phase as Fe, but is effective in improving the Curie temperature and the corrosion resistance of the grain boundary phase.

  The RTB-based sintered magnet to which the present invention is applied allows the inclusion of other elements. For example, elements such as Al, Cu, Zr, Ti, Bi, Sn, Ga, Nb, Ta, Si, V, Ag, and Ge can be appropriately contained. On the other hand, it is desirable to reduce impurity elements such as oxygen, nitrogen, and carbon as much as possible. In particular, the amount of oxygen that impairs magnetic properties is preferably 7000 ppm or less, more preferably 5000 ppm or less. This is because when the amount of oxygen is large, the rare-earth oxide phase, which is a nonmagnetic component, increases and the magnetic properties are deteriorated.

Such an R-T-B system sintered magnet is manufactured through the following processes.
Hereinafter, the content of each process is demonstrated. In the following description, an R-T-B system sintered magnet, which is a neodymium-based sintered magnet, will be described as an example of the rare earth sintered magnet. However, the present invention can be applied to other SmCo-based rare earth sintered magnets. Needless to say.
<Raw material alloy adjustment>
The raw material alloy of the RTB-based sintered magnet can be produced by a strip casting method or other known melting methods in a vacuum or an inert gas, preferably in an Ar atmosphere. In the strip casting method, a molten metal obtained by melting a raw metal in a non-oxidizing atmosphere such as an Ar gas atmosphere is ejected onto the surface of a rotating roll. The melt rapidly cooled by the roll is rapidly solidified in the form of a thin plate or flakes (scales). This rapidly solidified alloy has a homogeneous structure with a crystal grain size of 1 to 50 μm. The raw material alloy can be obtained not only by the strip casting method but also by a melting method such as high frequency induction melting. In order to prevent segregation after dissolution, for example, it can be solidified by pouring into a water-cooled copper plate. An alloy obtained by the reduction diffusion method can also be used as a raw material alloy.

<Crushing>
The raw material alloy is subjected to a grinding process. The pulverization process includes a coarse pulverization process and a fine pulverization process. First, the raw material alloy is coarsely pulverized until the particle size becomes about several hundred μm. The coarse pulverization is desirably performed in an inert gas atmosphere using a stamp mill, a jaw crusher, a brown mill or the like. Prior to coarse pulverization, it is effective to perform pulverization by allowing hydrogen to be stored in the raw material alloy and then releasing it. The hydrogen releasing treatment is performed for the purpose of reducing hydrogen as an impurity as a rare earth sintered magnet. The temperature of heating and holding for releasing hydrogen is 200 ° C. or higher, desirably 350 ° C. or higher. The holding time varies depending on the relationship with the holding temperature, the thickness of the raw material alloy, etc., but is at least 30 minutes or longer, preferably 1 hour or longer. The hydrogen release treatment is performed in a vacuum or Ar gas flow. The hydrogen storage process and the hydrogen release process are not essential processes. This hydrogen pulverization can be regarded as coarse pulverization, and mechanical coarse pulverization can be omitted.

  After the coarse pulverization process, the process proceeds to the fine pulverization process. A jet mill is mainly used for fine pulverization, and a coarsely pulverized powder having a particle size of about several hundreds of μm has an average particle size of 1 to 10 μm, preferably 2 to 6 μm. The jet mill releases a high-pressure inert gas from a narrow nozzle to generate a high-speed gas flow, accelerates the coarsely pulverized powder with this high-speed gas flow, collides with the coarsely pulverized powder, and collides with the target or the container wall. This is a method of generating a collision and crushing. A lubricant may be added to and mixed with the coarse powder before pulverization, or a lubricant may be added and mixed after pulverization or both.

<Molding in magnetic field>
The finely pulverized powder (magnetic material) obtained as described above is molded in a magnetic field to obtain a molded body. In the present embodiment, a parallel magnetic field forming method, which is a forming method in which the pressing direction and the direction of the applied magnetic field are parallel, is used. An orthogonal magnetic field forming method in which the pressing direction and the direction of the applied magnetic field are orthogonal can also be used.
The molding pressure in the magnetic field molding may be in the range of 30 to 300 MPa (0.3 to 3 ton / cm ² ). The orientation becomes better as the molding pressure is lower, but if the molding pressure is too low, the strength of the molded body will be insufficient and problems will occur when processing the molded body. To do. The final relative density of the molded body obtained by molding in a magnetic field is preferably 50 to 65%.
The magnetic field applied in the present invention may be about 800 to 1600 kA / m (10 to 20 kOe). The applied magnetic field is not limited to a static magnetic field, and may be a pulsed magnetic field. A static magnetic field and a pulsed magnetic field can be used in combination. When a pulsed magnetic field is used, a magnetic field as high as about 2400 kA / m (30 kOe) can be used.

<Sintering>
The molded body obtained by molding in a magnetic field is sintered in a vacuum or an inert gas atmosphere to obtain an R-T-B system sintered magnet. Although it is necessary to adjust sintering temperature by various conditions, such as a composition, a grinding | pulverization method, the difference of an average particle diameter, and a particle size distribution, what is necessary is just to sinter at 1000-1200 degreeC for about 1 to 10 hours.
After sintering, the obtained sintered body can be subjected to an aging treatment. This process is an important process for controlling the coercive force. In the case where the aging treatment is performed in two stages, it is effective to hold for a predetermined time in the vicinity of 800 ° C. and 600 ° C. When the heat treatment at around 800 ° C. is performed after sintering, it is particularly effective because the coercive force increases. In addition, since the coercive force is greatly increased by heat treatment at around 600 ° C., when the aging treatment is performed in one stage, the aging treatment at around 600 ° C. is preferably performed.

<Film formation>
The rare earth sintered magnet obtained as described above, particularly the RTB-based sintered magnet, forms a coating film on its surface. As the paint used for coating, any of acrylic resin-based paint, epoxy resin-based paint, and phenol resin-based paint can be used, and other paints can be used.
The thickness of the coating needs to be varied depending on the size of the magnet body, the required level of corrosion resistance, etc., but may be set as appropriate within a range of 3 to 30 μm. A desirable film thickness is 5 to 20 μm.

Now, in order to form a film as described above, a spray method in which paint is sprayed from a nozzle is used.
At this time, as shown in FIG. 1, a predetermined number of magnet bodies (rare earth sintered magnets, objects to be coated) 10 are arranged side by side on a net-like or plate-like tray 11. As shown in FIG. 2, in a state where a predetermined number of magnet bodies 10 are arranged on the tray 11, the interval S1 between the magnet bodies 10 is 8 to 10 mm in both the X direction and the Y direction in FIG. 10-70 mm.
As shown in FIG. 2, the nozzle 20 that sprays the paint is held at a predetermined angle at which the paint can be sprayed on at least two surfaces of the magnet body 10 having a substantially rectangular parallelepiped shape, for example. Specifically, the angle of the center line of the nozzle 20 with respect to the surface of the tray 11 is preferably 30 to 60 °. The nozzle 20 is moved in parallel with the upper surface of the tray 11 while maintaining the predetermined angle by an arm or a driving mechanism (not shown), thereby spraying the paint onto the magnet body 10 on the tray 11.

Here, as shown in FIG. 1, a dummy work (dummy member) 30 is disposed on the outer periphery of the tray 11.
The dummy work 30 is arranged at a predetermined interval S2 with respect to the magnet body 10 located on the outermost periphery among the plurality of magnet bodies 10 arranged on the tray 11. The interval S2 is 8 to 70 mm, preferably 10 to 60 mm in both the X direction and the Y direction. The height h of the dummy work 30 is preferably 0.8 to 1.3 times the height of the magnet body 10 with respect to the surface of the tray 11.
Furthermore, the width w of the dummy work 30 is 0.7 to 3 times, preferably 0.85 to 1.5 times the width of the magnet body 10 (the dimension in the same direction as the width w of the dummy work 30). At this time, if the magnet body 10 is a rectangular parallelepiped or a cube, the width of the magnet body 10 can be set to the dimension of one side thereof, and if the magnet body 10 is cylindrical, the diameter thereof can be set.

In this way, when the paint is sprayed from the nozzle 20 with the dummy work 30 set, the mist-like paint rebounds on the upper surface of the dummy work 30 and adheres to the side surface of the magnet body 10, and the dummy work 30. It stays in a concave space A surrounded by the work 30 and the magnet body 10 at the outermost periphery, and this makes it easier for paint to adhere to the side surfaces of the magnet body 10.
As a result, in the magnet body 10 arranged on the outermost peripheral portion of the tray 11, it is possible to sufficiently secure the film thickness of the coating formed on the side surface.

Furthermore, the thickness of the coating on the side surface of the magnet body 10 is adjusted by adjusting the distance S1 between the magnet bodies 10 adjacent to each other and the distance S2 between the dummy workpiece 30 and the magnet body 10 located at the outermost periphery. If the distances S1 and S2 are 8 to 70 mm, preferably 10 to 60 mm, as shown in FIG. 3, the side surface 10b is larger than the film thickness of the coating on the upper surface 10a of the magnet body 10. It is possible to increase the film thickness of the film.
The upper surface 10a of the magnet body 10 is often a magnetic pole surface, and it is preferable that the thickness of the coating on this portion be the minimum necessary. On the other hand, the side surface 10b of the magnet body 10 is preferably made as thick as possible in order to ensure corrosion resistance. By setting it as the above conditions, it becomes possible to realize a rare earth sintered magnet provided with a film having such a film thickness distribution.

  Instead of the dummy work 30, as shown in FIG. 4, a convex portion 40 or a stepped portion may be formed on the outer peripheral portion of the tray 11 so as to be in the same state as the dummy work 30 is set. good.

Here, since the effect by using the said structure was confirmed, the result is shown below.
An alloy having a composition of 29.5 wt% Nd-3.0 wt% Dy-1.0 wt% B-0.5 wt% Co-remainder Fe is prepared by strip casting, coarsened by hydrogen absorption and discharge, A raw material alloy powder having an average particle size of 4 μm was obtained by pulverizing with nitrogen gas in a mill.
This raw material alloy powder was molded in a magnetic field to produce a compact. After sintering the produced molded object on the conditions of 1100 degreeC x 2 hours, 800 degreeC and 600 degreeC aging treatment were performed for 1 hour each, and the RTB type sintered magnet was obtained.
The obtained RTB-based sintered magnet was processed into a 65 mm × 14 mm × 6 mm rectangular parallelepiped shape.

A film was formed on the surface of the processed RTB-based sintered magnet as follows.
Example 1
As shown in FIG. 1, R-T-B system sintered magnets are arranged on the tray with an interval S1 of 12 mm in both the X direction and the Y direction. A stainless steel block machined to the same dimensions as the magnet was disposed as a dummy workpiece at an interval S2 of 12 mm with respect to the outermost peripheral RTB-based sintered magnet.
And the coating material was sprayed on the RTB system sintered magnet from the nozzle by the spray method. A phenol resin paint was used as the paint. At this time, the angle of the central axis of the nozzle with respect to the tray surface is 45 °, the spray angle of the paint from the nozzle (spray spread angle) is 60 °, and the flow rate is 30 cc / min from diagonally upward in the Y direction in FIG. The paint was sprayed.
The nozzle was moved at a speed of 800 mm / sec in a movement pattern M as shown in FIG. When the nozzle moved from position P1 to position P2 while spraying the paint, the tray was rotated 90 °. Then, the paint was sprayed while moving the nozzle in the same movement pattern (however, this time the nozzle was moved from the position P2 toward the position P1). Thereafter, similarly, the 90 ° rotation of the tray and the spraying of the paint while moving the nozzle were repeated twice.
After the spraying of the paint was completed, the RTB-based sintered magnet with the paint sprayed on the surface was placed in a thermostatic bath and heat-treated at 150 ° C. for 20 minutes to completely cure the paint resin.

Subsequently, the R-T-B system sintered magnet was turned upside down, and the spraying of the paint and the 90 ° rotation of the tray were similarly repeated four times. Then, after the spraying of the paint was completed, the RTB-based sintered magnet having the paint sprayed on the surface was placed in a thermostatic bath and heat-treated at 150 ° C. for 20 minutes to completely cure the paint resin.
In this way, a film was formed on the surface of the RTB-based sintered magnet.

(Comparative Example 1)
On the tray, RTB-based sintered magnets were arranged at intervals of 12 mm in both the X direction and the Y direction, as shown in FIG. At this time, the dummy work used in Example 1 was not set on the tray.
And the coating material was sprayed from the nozzle on both surfaces of the RTB system sintered magnet by the spray method on the same conditions as Example 1, and the film was formed on the surface of the RTB system sintered magnet.

(Comparative Example 2)
As Comparative Example 2, a film was formed on the surface of the RTB-based sintered magnet by using the dipping method instead of the spray method. For this purpose, the processed R-T-B system sintered magnets are arranged side by side in a bowl-shaped jig, which is immersed in a phenol resin coating solution together with the jig, and the entire surface of the R-T-B system sintered magnet. The paint was applied to. Subsequently, the paint was centrifuged and dried using a centrifuge. The rotation speed of the centrifuge at this time was 400 rpm, and the drying time was 30 seconds.
After the application of the paint was completed, the RTB-based sintered magnet was placed in a thermostatic bath and heat-treated at 150 ° C. for 20 minutes to completely cure the paint resin.
In this way, a film was formed on the surface of the RTB-based sintered magnet by the dip method.

About the R-T-B system sintered magnets of Example 1, Comparative Example 1, and Comparative Example 2 obtained as described above, 9 samples were extracted as samples, and at the center positions of the upper surface and side surfaces of each sample, respectively. The film thickness was measured by SEM observation. The samples extracted in Example 1 and Comparative Example 1 were extracted from the positions (1) to (9) shown in FIG.
As a result, the film formed by the dip method of Comparative Example 2 has a very large variation of 3.81 to 8.84 μm on the top surface and 3.26 to 6.69 μm on the side surface, and sufficient quality control at the time of mass production. It was confirmed that it was a difficult level to do.

FIG. 5 is a diagram showing the thickness of the coating on the top surface of the RTB-based sintered magnet of Example 1 and Comparative Example 1, and FIG. 6 is a diagram showing the thickness of the coating on the side facing the outer peripheral side.
As shown in FIGS. 5 and 6, in the sample of Comparative Example 1 in which no dummy workpiece was used, the upper surface and the side surface at the sample positions (4), (5), and (6) that were located in the tray central row. The thickness of the coating was small, and all were 5 μm or more. However, at the sample positions (1), (2), (3), (7), (8), and (9) that were located in the outermost row of the trays, the coating on the upper surface was 5.62 to 6.45 μm. The variation was small, and the thickness of all 5μm or more was secured. On the other hand, the coating on the side of the portion facing the outer periphery was 4.26-5.17μm, and the variation was small. It was less than 5 μm, and it was confirmed that a sufficient film thickness could not be secured.
On the other hand, in the sample of Example 1 using a dummy workpiece, it is 6.04 to 7.56 μm regardless of the position on the tray, the variation is small, and the thickness of the coating on the upper surface and the side surface is all in all locations. Both were confirmed to be 5 μm or more.
Thereby, by arranging a dummy work on the outer side of the R-T-B system sintered magnet on the outermost peripheral side, the film thickness of the side surface film is ensured without increasing the film thickness of the upper surface film. It was confirmed that

Next, in order to confirm the degree of the effect of the dummy workpiece, the distance between the dummy workpiece and the outermost R-T-B system sintered magnet was changed to 0 to 200 mm under the same conditions as described above.
As a result, as shown in FIG. 7, the thickness of the coating on the upper surface of the outermost R-T-B type sintered magnet regardless of the distance between the dummy workpiece and the outermost R-T-B type sintered magnet. It was almost constant. On the other hand, the thickness of the coating on the side surface varies depending on the distance between the dummy workpiece and the outermost peripheral RTB-based sintered magnet, and the dummy workpiece and the outermost peripheral RTB system. When the distance from the sintered magnet is less than 5 mm, the thickness of the coating on the side surface is clearly smaller than the upper surface of the RTB-based sintered magnet. In addition, when the distance between the dummy workpiece and the outermost RTB-based sintered magnet is 10 μm or more and less than 70 μm, the thickness of the coating on the side surface with respect to the upper surface of the RTB-based sintered magnet is increased. Was confirmed.
Thus, the thickness of the coating on the side surface of the outermost RTB-based sintered magnet can be ensured by the distance between the dummy workpiece and the outermost RTB-based sintered magnet. Moreover, the thickness of the coating on the side surface of the outermost R-T-B type sintered magnet can be made thicker than the upper surface by the distance between the dummy work and the outermost R-T-B type sintered magnet. It can be said that there is.
The relationship between the distance between the dummy workpiece and the outermost peripheral RTB-based sintered magnet and the thickness of the coating is not limited to the outermost peripheral RTB-based sintered magnet. It is clear that the same can be said for the interval between the R-T-B system sintered magnets arranged side by side. That is, the thickness of the coating on the side surface of the RTB-based sintered magnet can be varied depending on the interval between the RTB-based sintered magnets adjacent to each other on the tray. It can be said that the thickness of the coating on the side surface of the RTB-based sintered magnet can be made larger than that of the upper surface depending on the interval between the -B-based sintered magnets.

Subsequently, under the same conditions as in Example 1, the height of the dummy workpiece was changed to 5 to 12 mm. Here, the thickness of the upper surface and the side surface of the coating was measured for the RTB-based sintered magnet disposed on the outermost peripheral portion (position (2) in FIG. 1) on the tray.
As a result, as shown in FIG. 8, in the region where the height of the dummy work exceeds 5 mm and is 8 mm or less, the RTB-based sintered magnet has a height of 6 mm. It was confirmed that the thickness of the side surface becomes larger than the thickness of the coating on the upper surface of the sintered magnet. Furthermore, when the height of the dummy workpiece was 10 mm or more, it was confirmed that the thickness of the coating on the side surface of the RTB-based sintered magnet was less than 5 μm, and a sufficient film thickness could not be secured.
Thus, by making the height of the dummy work appropriate, the film thickness of the side film of the R-T-B system sintered magnet can be secured, and moreover, the side film thickness is higher than the film thickness of the upper surface. It was confirmed that the thickness could be increased.

Further, under the same conditions as in Example 1, the width of the outermost RTB-based sintered magnet and the dummy workpiece was changed to 3 to 20 mm.
As a result, as shown in FIG. 9, the width of the RTB-based sintered magnet is 14 mm, whereas the width of the dummy work is 4 mm or less, It was confirmed that the thickness of the coating on the upper surface was less than 5 μm and a sufficient film thickness could not be secured. Therefore, when the width of the dummy workpiece is narrow (thin) and has a simple wall shape, it can be said that the effect of maintaining the film thickness of the coating on the side surface of the RTB-based sintered magnet is low. In other words, it is more likely that the paint rebounds on the upper surface of the dummy work than the mist paint stays between the dummy work and the outermost RTB-based sintered magnet. It can be inferred that the contribution is high in terms of securing the film thickness of the coating on the side surface of the B-based sintered magnet.
Moreover, when the width of the dummy workpiece was 10 mm or more, it was confirmed that the thickness of the side surface was larger than the thickness of the coating on the side surface of the RTB-based sintered magnet.

  In this way, when forming a film on the surface of the RTB-based sintered magnet by the spray method, the outermost peripheral side is formed by forming a dummy workpiece on the outer peripheral side or a stepped portion or a convex portion similar thereto. In the RTB-based sintered magnet, it is possible to ensure the thickness of the coating on the side surface facing the outer peripheral side. In addition, by appropriately setting the width and height of the dummy workpiece and the distance between the dummy workpiece and the outermost RTB-based sintered magnet, the coating on the outermost RTB-based sintered magnet The thickness can be made thicker on the side surface than the upper surface, or thicker on the upper surface than the side surface while ensuring a sufficient film thickness. In particular, in an RTB-based sintered magnet, the upper and lower surfaces are often used as magnetic pole surfaces in the spraying process for forming a film. In such a case, it is preferable that the magnetic pole surface (upper surface) has a minimum coating thickness. On the other hand, it is preferable that the side surface has a sufficiently thick film for ensuring durability. From this point of view, it can be said that the present method capable of forming a film having a film thickness larger on the side surface than on the upper surface is very effective.

In the coating method of the RTB system sintered magnet in this Embodiment, it is a top view which shows the state which has arranged the dummy workpiece | work on the tray. It is a figure which shows the positional relationship of the RTB type | system | group sintered magnet and dummy workpiece | work on a tray. It is a perspective view which shows a RTB type sintered magnet. It is a figure which shows an example of the tray which provided the convex part in the outer peripheral part. It is a figure which shows the thickness of the film in the upper surface of the RTB type sintered magnet of Example 1 and Comparative Example 1. It is a figure which shows the thickness of the film in the side surface of the RTB type sintered magnet of Example 1 and Comparative Example 1. It is a figure which shows the relationship between the space | interval of the outermost RTB system sintered magnet and a dummy workpiece, or the space | interval between adjacent RTB system sintered magnets, and the thickness of a film. It is a figure which shows the relationship between the height of a dummy workpiece | work, and the thickness of a film. It is a figure which shows the relationship between the width | variety of a dummy workpiece | work, and the thickness of a film.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Magnet body (rare earth sintered magnet, coating object), 10a ... Upper surface, 10b ... Side surface, 11 ... Tray, 20 ... Nozzle, 30 ... Dummy work (dummy member), 40 ... Projection

Claims (6)

A method of forming a coating on the surface of the rare earth sintered magnet by spraying paint on the surface of the rare earth sintered magnet,
Arranging the plurality of rare earth sintered magnets side by side on a tray;
With respect to the rare earth sintered magnet on the tray , a stepped portion or a convex portion protruding upward is formed on the outer circumferential side of the rare earth sintered magnet located on the outermost circumference among the plurality of rare earth sintered magnets. Spraying the paint from obliquely above ;
Including
In the step of spraying the coating material, the stepped portion or the protruding portion is formed on the outer peripheral side of the rare earth sintered magnet located on the outermost periphery, so that the coating material is formed on the upper surface of the stepped portion or the protruding portion. The coating method of the rare earth sintered magnet is characterized in that the paint is adhered to a side surface facing the outer circumferential side of the rare earth sintered magnet located on the outermost circumference .   In the step of spraying the paint, in order to make the stepped portion or the convex portion formed on the outer peripheral side of the rare earth sintered magnet located on the outermost periphery, the rare earth firing located on the outermost periphery on the tray is performed. The method for coating a rare earth sintered magnet according to claim 1, wherein a dummy member is set on the outer peripheral side of the magnetized magnet.   In the step of spraying the paint, the outer peripheral side of the rare earth sintered magnet located on the outermost periphery in order to make the stepped portion or the convex portion formed on the outer peripheral side of the rare earth sintered magnet located on the outermost periphery. The method for coating a rare earth sintered magnet according to claim 1, wherein the stepped portion or the convex portion is formed on the tray.   2. The step of spraying the coating material is characterized in that the film thickness of the coating film on the side surface of the rare earth sintered magnet is made larger than the film thickness of the coating film of the coating material on the upper surface of the rare earth sintered magnet. 4. The method for coating a rare earth sintered magnet according to any one of items 1 to 3.   The rare earth sintered magnet is a rectangular parallelepiped of 65 × 14 × 6 mm, and the stepped portion or the convex portion has the same dimensions as the rare earth sintered magnet,
  The rare earth sintered magnet and the stepped portion or the convex portion are arranged side by side so that the distance between them is 10 mm or more and less than 70 mm, and the height of the stepped portion or the convex portion is an area of 5 mm to 8 mm, and The method for coating a rare earth sintered magnet according to any one of claims 1 to 4, wherein a width of the stepped portion or the convex portion is 10 mm or more. A tray used for forming a film on the surface of the rare earth sintered magnet by spraying paint on the surface of the rare earth sintered magnet,
When the plurality of rare earth sintered magnets are arranged on the upper surface, a stepped portion or a convex portion protruding upward is formed so as to have a predetermined interval on the outer peripheral side of the rare earth sintered magnet located on the outermost periphery ,
When the paint is sprayed obliquely from above, the stepped portion or the convex portion rebounds the paint on the upper surface of the stepped portion or the convex portion, and the outer periphery of the rare earth sintered magnet located at the outermost periphery. A coating tray , wherein the paint is adhered to a side surface facing the side .

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