JPS61148808A - Manufacture of rare earth magnet - Google Patents

Abstract

PURPOSE:To obtain a sintered body with dimensional accuracy through preventing the sintered body and a base from sintering by sintering moldings after interposing powder of oxide samarium between the moldings and the base. CONSTITUTION:In a process in which powdered moldings including a rare earth element is sintered on a base, moldings are sintered through interposing powder of oxide samarium between the moldings and the base. Molding in a magnetic field is done by using alloy powder composed of, for instance, Sm 27wt%, Co 47.1wt%, Cu 4.6wt%, Fe 18.5wt% and Zr 2.8wt%. On the other hand, an Sm2O3 powder is sprayed by using a 300 mesh screen on a pressure plate and a platelike base made of stainless SUS304. After moldings are placed on a surface adhered by the powder of this base, on this the pressure plate is put with the surface down adhered by the powder, and are sintered in 1,200 deg.C for 1hr, a rate earth magnet is obtained.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a method for manufacturing rare earth magnets.

[Background technology]

Rare earth magnets such as S m Co are magnets whose demand has recently increased significantly as high-performance magnets having high saturation magnetization and high coercive force. In particular, they have been actively adopted in speakers and motors, which are becoming smaller and lighter. The general manufacturing method for rare earth magnets is as follows.

A magnet alloy containing rare earth elements is pulverized into a fine powder.
This is press-molded in a magnetic field. Next, this molded body is sintered at 1180°C to 1220°C and then rapidly cooled.

Then, aging treatment is performed at around 800℃ for 2 to IO hours,
A high-performance rare earth magnet is obtained by slow cooling.

By the way, thin ring magnets are used in motor rotors and the like. In order to manufacture such thin plate magnets, a method is used in which thin plates are created by sintering thick materials with the same cross-sectional shape and slicing them. This method requires a cutting allowance for slicing, resulting in material loss. Therefore, attempts have been made to form a thin plate from the beginning and sinter it. However, when a thin plate-shaped object (molded body) is sintered, warping tends to occur, so the thin plate-shaped formed body is placed on a base, and a metal or ceramic presser plate is placed on top of the formed body and then sintered. must be tied.

In this way, if a thin plate-shaped compact is sandwiched between one machine and a holding plate and sintered at the optimum sintering temperature, seizure may occur between the sintered body and the base and/or the holding plate. . When seizure occurs, it prevents uniform shrinkage and causes abnormal deformation of the sintered body. Further, there arises the problem that the sintered body cannot be removed from the base or the presser plate.

[Purpose of the invention]

In view of the above, this invention prevents seizure between the sintered body and the base, and also prevents seizure between the sintered body and the presser plate, and provides a process for obtaining a sintered body with high dimensional accuracy. The purpose is to provide a method for manufacturing rare earth magnets containing.

[Disclosure of the Invention] In order to achieve the above object, the present invention provides a method for manufacturing a rare earth magnet that includes a step of placing a compact of powder containing a rare earth element on a base and sintering the compact. The gist of the present invention is a method for producing a rare earth magnet, characterized in that the molded body is sintered with samarium oxide powder interposed between it and the base. Below, this invention will be explained in detail, especially its characteristic parts.

As the powder for the magnet used in this invention, a powder containing a rare earth element is used, and in general, an alloy powder containing a rare earth metal such as Si and Ce and cobalt is used, but the invention is not limited to this. The powder used for the magnet is one made according to a normal manufacturing method. This powder is usually finely divided. This powder for magnets is generally molded while applying a magnetic field in a direction parallel to the pressing direction, but this is not the case. It may also be formed into a thin plate. This molded body is then placed on a base made of metal or ceramic and sintered. This base is not limited to a table-shaped one, and various types such as a plate-shaped body and a sheet-shaped body can be used, and the material is not particularly limited as long as it can be used for sintering, including metals and ceramics. . In addition, when sintering a thin plate-shaped compact, as mentioned above, in order to prevent the occurrence of warping, the compact is placed on a base, and a presser plate is placed on top of the compact. It is preferable to place the molded body between the base and the holding plate. The holding plate may be made of a certain material as long as it can be used for sintering, such as metal or ceramic; for example, it may be made of the same material as the base.

Rare earth metals are very highly active metals, l・0
At temperatures above 00°C, it tends to react with the base and presser plate and become stuck. If it is a thick bulge, even if seizure occurs, it is possible to remove that part and finish it as a final product, but the yield will be poor. In particular, in the case of a thin plate-like product, it is preferable to perform sintering so that the final product can be completed with the minimum amount of polishing necessary. For these reasons, deformation or damage to the sintered body due to seizure must be avoided as much as possible.

Therefore, in this invention, samarium oxide powder is interposed between the molded body and the base by scattering the powder on the base to reduce the direct contact area between the molded body and the base. This is to prevent the above-mentioned seizure. The inventors
In order to find out what kind of powder is suitable for achieving this effect, we tried using several types of ceramic and mic powders6. As a result, the powder was A1203, CeO
2 etc. reacted with the sintered body, which adversely affected the properties of the final product, the magnet, and in the case of BN, seizure occurred between the base and the sintered body. However, samarium oxide (Sm20
3), no seizure occurred and no reaction occurred with the sintered body. Therefore, in the present invention, Sm203 (samarium oxide) powder is used as the powder.

The sintered body that has been sintered in this way does not seize at all with the base or the presser plate, or the degree of seizing that occurs is smaller than in the case of normal manufacturing methods. be. Therefore, according to the manufacturing method of the present invention, only a small amount of the portion where the seizure has occurred can be removed, which can also contribute to improving the yield. In particular, in the case of thin plate shaped bodies, the thickness of the formed body is often almost the same as the thickness of the final product, the magnet, so according to the manufacturing method of the present invention, the thin plate shaped bodies can be precisely Moreover, a thin plate magnet can be obtained by sintering with a high yield. If a thin plate magnet can be obtained by sintering a thin plate shaped body, as described above, there will be no need for cutting margins required for slicing, and the yield will further improve. Of course, with the manufacturing method of the present invention, even thick molded bodies can be sintered with good yield.

The amount of intervening powder has a large effect on the shrinkage state of the sintered body. The powder particle size is preferably 5 to 10 μm, and it is preferable to sieve the powder through a 300-mesh sieve and spread it on the base.

At this time, if the amount of powder sprinkled is too large, the shrinkage rate in the longitudinal direction (perpendicular to the pressing direction) of the sintered body will be lower than usual, and the shrinkage rate in the thickness direction (direction parallel to the pressing direction) will be lower than usual. Shrinkage rate increases. Further, a problem arises in that the surface of the sintered body becomes extremely uneven after sintering. On the other hand, if the amount of intervening powder is too small, the area of direct contact between the sintered body and the base will increase, making it more likely that seizure will occur. Specifically, the ratio of the area covered by the powder is 3 of the opposing area between the compact and the base or presser plate.
It is preferable to set it to about 0 to 50%.

The method of interposing the powder between the base and the molded body and between the molded body and the presser plate is not particularly limited, and may be performed as appropriate. Examples include the method described above and a method of sprinkling powder onto the molded body. Further, it is preferable that the intervening powder is uniformly distributed among the powders, and it is better to avoid clumping in some parts.

After sintering, the sintered body is processed into a high-performance rare earth magnet using conventional methods.

In the manufacturing method of the present invention, during sintering, seizure between the sintered body and the base does not occur at all, or occurs less frequently than in the normal method, so rare earth magnets can be manufactured with a high yield. Furthermore, the same effect can be achieved with regard to seizure between the sintered body and the presser plate. Therefore, the manufacturing method of the present invention is preferably used particularly when manufacturing a thin plate rare earth magnet by sintering a thin plate shaped body. That is,
According to the manufacturing method of the present invention, a sintered body can be obtained without seizing at all on either the base or the holding plate, or even if seizing occurs, the frequency of seizing is much lower, and thin plate-shaped rare earth magnets can be produced with high precision and high yield. You will be able to obtain it.

Examples and comparative examples of the present invention are shown below (Example 1) Sm27wt%, CO47,1wt%, Cu4.6
wt%, Fe18.5wt% + Z r2.8 wt
% of the alloy powder was molded in a magnetic field under the following molding conditions.

Molding pressure: 1 ton/ad Magnetic field parallel to the pressing direction: 20 kOe Molded object size:
・φ20m+m
w ) and presser plate (stainless steel 5US304301ImX
・Sm2O3 powder (average particle size 5)
μm, purity 99°99%) was dispersed using a 300 mesh sieve. At this time, the sieve was slightly vibrated to prevent the powder from clumping and to spread it uniformly over the entire surface. Next, the molded body was placed on the surface of the base to which the powder had adhered, and the pressing plate was placed thereon with the surface to which the powder had adhered facing down.

These were sintered at 1200°C for 1 hour. The thin plate-shaped sintered body thus obtained was processed according to a conventional manufacturing method to obtain a thin plate-shaped rare earth magnet. After repeating this method 10 times,
The number of pieces in which seizure occurred during sintering was two.

(Comparative Example 1) In the manufacturing method of Example 1, a plate-shaped base (stainless steel 5US30430n x 30wmx l a
3m2 O3 powder was not sprinkled directly on the molded body, and the presser plate (stainless steel 5US30430+n X30m+m'X
A thin plate-shaped rare earth magnet was obtained in the same manner as in Example 1, except that 1 m) was directly placed on the magnet. Although this manufacturing method is a conventional method, when this was repeated 10 times, the number of pieces that suffered from seizure during sintering was 9.

Comparing the results of Example 1 and Comparative Example 1, Example 1 (
That is, the crawling produced by the production method of the present invention was found in Comparative Example 1.
It can be seen that the number of burn-in occurrences is significantly reduced compared to the conventional method.

Next, two other embodiments of this invention will be shown.

(Example 2) In the manufacturing method of Example 1, in the sintering process, S was used instead of stainless steel 5IIS304 for the plate-shaped base and presser plate.
A thin plate-shaped rare earth magnet was obtained in the same manner as in Example 1, except that the m2 o3 sintered body was used. When this manufacturing method was repeated 10 times, no seizure occurred during sintering. Therefore, it can be said that this method has the greatest anti-seizure effect. The Sm2O3 sintered body used for the base and presser plate in this example was made by molding Sm2O3 powder and
It was produced by sintering at 00°C for 1 hour.

As can be seen from this example, a rare earth magnet is obtained by placing a powder compact containing a rare earth element on a base and sintering it, or by sandwiching it between a base and a holding plate and sintering it. In this case, the most preferable material for the base and the presser plate is Sm2O3 sintered body.

(Example 3) The manufacturing method of Example 1 was carried out in the same manner as in Example 1, except that in the sintering step, Sm2O3 powder was sprinkled on the molded body instead of on the plate-shaped base and presser plate. , a thin plate-like rare earth magnet was obtained. When this manufacturing method was repeated 10 times, the number of pieces in which seizure occurred during sintering was two, which was the same as in Example 1. As can be seen from this example and Example 1, in the manufacturing method of the present invention, the method of interposing the Sm2O3 powder between the base and the molded body and between the presser plate and the molded body is not particularly limited. be.

Note that this invention is not limited to the above embodiments.

〔Effect of the invention〕

Claims (3)

[Claims] (1) In a method for producing a rare earth magnet, which includes a step of placing a molded body of powder containing a rare earth element on a base and sintering it, samarium oxide powder is interposed between the molded body and the base. A method for producing rare earth magnets, which is characterized by sintering a compact. (2) The method for producing a rare earth magnet according to claim 1, wherein the molded body is a thin plate-like product. (3) Sintering is performed with the molded body sandwiched between a base and a holding plate, and samarium oxide powder is also interposed between the molded body and the holding plate. The manufacturing method for rare earth magnets described in Section 1.