JP7501277B2 - Manufacturing method of sintered magnet - Google Patents

Description

The present disclosure relates to a method for producing a sintered magnet .

Generally, sintered magnets are manufactured by preparing magnet powder, applying a magnetic field to a magnet alloy to create a compact, and then heating and sintering (firing) the compact. When manufacturing bow-shaped sintered magnets, it is well known that cracks and chips are likely to occur when the compact is heated and sintered, due to the difference in shrinkage rate between the sintering base plate and the compact.

For example, in Patent Document 1, a bow-shaped compact made of a rare earth magnet alloy is sintered using a sintering plate with an average surface roughness Ra of 0.7 to 45 μm, thereby preventing the compact from cracking or chipping.

JP 2002-305122 A

Chipping of green bodies is likely to occur not only during sintering, but also when the green bodies are transported. In particular, when green bodies are stacked on a base plate to improve transport efficiency, chipping is likely to occur when the stacked green bodies tip over or become misaligned. In order to prevent chipping, the number of layers can be reduced, but this would decrease productivity. Patent Document 1 does not disclose a base plate that prevents chipping due to tipping or misalignment and improves productivity.

Therefore, the purpose of this disclosure is to provide a method for manufacturing base plates and sintered magnets that can improve productivity.

In view of the above, the base plate of the present disclosure, in exemplary embodiment 1, is a base plate having a first plate-shaped member made of a non-magnetic material having a first main surface and a second main surface located on the opposite side thereof, with a recess formed along the surface direction, and a second plate-shaped member made of a soft magnetic material provided in the recess of the first member.

In aspect 2, the recess is formed on the first main surface of the first member, which is the base plate described in aspect 1.

In aspect 3, the base plate according to aspect 2 has a protective layer on at least the first main surface side of the second member.

In aspect 4, the base plate is as described in any one of aspects 1 to 3, in which a plurality of recesses are formed and the second member is provided in each of the plurality of recesses.

In view of the above, the present disclosure provides a method for producing a sintered magnet, in exemplary aspect 5, comprising:
A method for producing a sintered magnet using the base plate described in any one of aspects 1 to 4, comprising the steps of: a powder preparation step of preparing powder for a magnet; a molding step of molding the magnet powder to obtain a green body; a stacking step of stacking the green body on the first main surface side of a second member; and a sintering step of heating and sintering the green body.

In aspect 6, the method for producing a sintered magnet according to aspect 5 is such that the molded body has a shape selected from the group consisting of an arch shape, a block shape, and a ring shape.

The manufacturing method of the base plate and sintered magnet disclosed herein makes it possible to improve productivity.

1A and 1B are diagrams showing a base plate according to an embodiment, in which (a) shows a cross-sectional view of the base plate, and (b) shows a top view of the base plate with a protective layer omitted. 13A and 13B are diagrams showing a base plate according to another embodiment, in which (a) shows a cross-sectional view of a base plate having a plurality of second members provided thereon, and (b) shows a cross-sectional view of a base plate having a second member provided within a first member. FIG. 2 is a schematic cross-sectional view of a molded body stacked on a base plate according to an embodiment of the present invention.

Below, an exemplary embodiment of a base plate 1 will be described with reference to Figs. 1 and 2. Fig. 1 shows a base plate according to the embodiment, where (a) shows a cross-sectional view of the base plate and (b) shows a top view of the base plate with the protective layer omitted. The base plate 1 has a first member 2, a second member 3, and a protective layer 4.

The first member 2 has a plate-like shape and has a first main surface M1 and a second main surface M2 opposite the first main surface M1. A recess 2a is formed in the first main surface M1. The recess 2a is formed along the surface direction of the first main surface M1, and is formed at a position where the molded body G described below is to be disposed.

The material of the first member 2 is a non-magnetic material, and more preferably, a paramagnetic material such as Al is used.

The base plate 1 is placed near the molding device so that the green bodies G can be stacked as soon as they are molded. As a result, it is strongly affected by the leakage magnetic field generated by the molding device. At this time, if the material of the first member 2 is easily affected by the leakage magnetic field, the base plate 1 will move, and the stacked green bodies G will tend to tip over or shift out of position, which will lead to chipping. However, by making the material of the first member 2 a non-magnetic material, the influence of the leakage magnetic field can be reduced, making the base plate 1 less likely to move. Therefore, the stacked green bodies G will be less likely to tip over or shift out of position. As a result, it is possible to suppress the occurrence of chipping and increase the number of stacks, which will improve productivity.

The second member 3 has a plate-like shape and is provided in the recess 2a of the first member 2. The second member 3 is made of a soft magnetic material, such as Fe.

The second member 3 needs only to be fixed to the recess 2a of the first member 2, and the means for doing so is not particularly important, for example, by adhesive, bolts, or insertion.

When the material of the second member 3 is a soft magnetic material as in the embodiment, the second member 3 is affected by the leakage magnetic field, so the movement of the compact G can be suppressed and chipping due to tipping or misalignment can be suppressed. Even if the second member 3 is affected by the leakage magnetic field, the weight of the first member 2 and the weight of the compact G are added, making it difficult for the base plate 1 to move, so chipping due to tipping or misalignment can be suppressed. As a result, the number of tiers can be increased, improving productivity.

Furthermore, if the material of the second member 3 is a soft magnetic material, the magnetic force of the compact G will cause it to weakly adhere to the second member 3. This improves handling and maintenance, and makes it possible to prevent the compacts from falling over or chipping. Furthermore, when stacking the compacts G, the compacts G, which have magnetic force, may attract each other and become misaligned, which may result in the compacts falling over or chipping. However, since the compacts G weakly adhere to the second member 3, the compacts G to be stacked will not easily attract the compacts G already placed therein. This makes it difficult for the compacts G to become misaligned, which prevents the compacts from falling over or chipping, and allows for a larger number of stacks, thereby improving productivity.

The protective layer 4 is provided particularly to suppress rust on the second member 3 and to improve the maintainability of magnetic powder that adheres to the second member 3 when the second member 3 becomes slightly magnetic. In the embodiment, it is provided on the first main surface M1 of the first member 2 and the surface on the first main surface M1 side of the second member 3. By providing it in this manner, it is possible to suppress the occurrence of collapse or chipping of the compact G due to rust, and to suppress defects in the product appearance due to magnetic powder adhering to the compact G, thereby improving productivity. Note that the method of providing the protective layer 4 is not limited to this, but it is preferable to provide it at least on the second member 3.

The material of the protective layer 4 is, for example, a resin material such as urethane rubber, but is not limited to this and any material that inhibits rust and improves the maintenance of the attached magnetic powder may be used.

However, the embodiment of the base plate 1 is not limited to this. Figure 2 shows a base plate according to another embodiment, where (a) shows a cross-sectional view of a base plate 11 in which a plurality of second members 13 are provided, and Figure 2(b) shows a cross-sectional view of a base plate 21 in which a second member 23 is provided within a first member 22. The same reference numerals are used for the same configurations as in the embodiment.

As shown in FIG. 2(a), multiple recesses 12a may be provided in the first member 12, and the second members 13 may be disposed in each recess 12a. In this case, if the space between the second members 13 is too wide, a leakage magnetic field will pass between the second members 13, making the compact G susceptible to the effects of the leakage magnetic field, so it is desirable to narrow the space. Therefore, although multiple recesses 12a are provided in FIG. 2(a), it is also possible to provide one recess 12a and provide multiple second members 13 so that the second members 13 are in contact with each other.

2(b), a recess 22a may be formed in the first member 22 so that the second member 23 is not exposed to the first main surface M3 side and the second main surface 4 side. In this case, even if the second member 23 rusts, it does not affect the compact G, so there is no need to provide a protective layer 4 on the first main surface M3 on which the compact G is placed. The protective layer 4 may be provided on the first main surface M3 to improve maintainability due to adhesion of magnetic powder, but in this case, it is preferable to provide it at least on the second member 23. Also, the first member 22 may have multiple recesses 22a and the second member 23 may be placed in each recess 22a, or one recess 22a may be provided and multiple second members 23 may be provided.

Next, a method for manufacturing a sintered magnet using the base plate 1 will be described with reference to Figure 3. First, magnet powder is prepared (powder preparation process). The magnet powder is prepared from an appropriate alloy depending on the desired sintered magnet. For example, for a ferrite sintered magnet, a powder made by finely pulverizing a calcined body is prepared, and for a rare earth sintered magnet, a powder made by finely pulverizing a rare earth alloy (such as an Nd-Fe-B alloy) is prepared.

Next, the magnet powder is molded to obtain a green body G (molding process). In order to increase production efficiency, a molding device capable of producing multiple green bodies G is used, and a magnetic field is applied to the magnet powder. Note that the molding device is not limited to this, and a single-cavity device may also be used. At this time, it is desirable to place a base plate 1 near the molding device so that the green bodies G can be stacked as soon as they are molded. Also, although the green bodies G are formed in a bow shape, this is not limited thereto, and any shape that can be stacked, such as an arch, block, or ring, may be used.

Figure 3 shows a schematic cross-sectional view of the molded bodies G stacked on the base plate 1 according to the embodiment. As shown in Figure 3, the molded bodies G are stacked on the first main surface M1 side of the second member 3 (stacking process). Stacking in this manner can prevent chipping due to the molded bodies G falling or shifting in position, and can increase the number of stacked bodies, improving productivity. Note that the effect of improving productivity can be obtained even when stacking one body at a time, but a greater effect can be obtained when stacking multiple bodies at once, as many molded bodies G can be stacked efficiently.

Then, the green bodies G are heated and sintered (fired) (sintering process). At this time, the stacked green bodies G are replaced with sintering materials before sintering. Sintering the green bodies G produces sintered magnets.

This disclosure has industrial applicability in that it provides a manufacturing method for base plates and sintered magnets that can improve productivity.

1, 11, 21... base plate 2, 12, 22... first member 2a, 12a, 22a... recess 3, 13, 23... second member 4... protective layer M1, M3... first main surface M2, M4... second main surface G... molded body

Claims (5)

A method for producing a sintered magnet using a base plate including a plate-like first member made of a non-magnetic material having a first main surface and a second main surface located on the opposite side thereof, with a recess formed along a surface direction, and a plate-like second member made of a soft magnetic material and provided in the recess of the first member, the method comprising the steps of:
a powder preparation step of preparing powder for magnets;
a molding step of molding the powder for magnets to obtain a green body;
a stacking step of stacking the molded bodies on the first main surface side of the second member;
a sintering step of heating and sintering the compact;
A method for producing a sintered magnet comprising the steps of: The method for producing a sintered magnet according to claim 1 , wherein the recess of the base plate is formed in the first main surface of the first member. The method for producing a sintered magnet according to claim 2 , further comprising the step of: forming a protective layer on at least a surface of said base plate on a side of said first main surface of said second member; 4. The method for producing a sintered magnet according to claim 1, wherein a plurality of recesses are formed in the base plate , and the second member is provided in each of the plurality of recesses. The method for producing a sintered magnet according to claim 1 , wherein the molded body has a shape selected from the group consisting of an arch shape, a block shape, and a ring shape.

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