JPH07161560A - Manufacture of rare earth magnet - Google Patents

Abstract

PURPOSE:To provide a magnet sintered body, cost of which is lower than those of alumina and yttria boards which have been used and cracking, breaking and deformation of which due to a contact reaction with alumina or the yttria board and a magnet molded form at the time of sintering variation of size of which are inhibited and which has an excellent dimensional accuracy, by developing fine powder for sintering for a rate earth magnet. CONSTITUTION:Y2O3 powder sintered at a temperature of 1000 deg.C or higher and having a particle diameter of from 5mum to 500mum is used as fine powder for sintering, and a rate earth magnet molded form is manufactured in the manufacture of a rare earth magnet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of dimensional accuracy of a magnet sintered body in a method for producing a rare earth magnet.

[0002]

2. Description of the Related Art Since rare earth magnets have high magnetic properties, demand for them has been increasing in recent years although they are expensive. Rare earth magnets are manufactured through a powder sintering process, but since they contain a large amount of rare earth elements, which are active metals, the magnet compact and the metal plate for sintering react during welding and weld, causing cracks in the magnet compact. It was a cause of chipping, deformation and the like. A thin plate made of a material such as alumina or yttria can be inserted between the magnet molding and the metal plate for sintering to prevent welding, but the alumina plate and yttria plate are vulnerable to heat shock and are difficult to reuse. is there. Further, in the case of an alumina plate, it is reduced by a rare earth element and therefore has a drawback that it serves as a supply source of oxygen.

[0003]

In order to prevent the reaction between the rare earth magnet molded body and the sintered metal plate, there is a method of using a spread powder to prevent the two from contacting each other, but this is required for the spread powder. As for performance, the magnet compact has good sliding properties, and there has never been a powder for sintering that is stable against the rare earth elements contained in the magnet compact, and the method of inserting an alumina plate or yttria plate causes the magnet compact to shrink. As a result of not averaging smoothly,
There were problems such as the size of the magnet sintered body being different between the upper and lower sides, and in the case of the ring-shaped sintered body, the inner diameter and the outer diameter of the set surface in contact with the spread powder varied. The present invention has developed a sintering bed powder for rare earth magnets, which is lower in cost than the conventionally used alumina and yttria plates, and which can be cracked, chipped, deformed or magnetized by a reaction during sintering. The present invention aims to provide a magnet sintered body that suppresses dimensional variations and has high dimensional accuracy.

[0004]

In order to solve the above problems, the inventors of the present invention have made various studies on a sintering powder suitable for sintering rare earth magnets, and have arrived at the present invention. The gist thereof is, in the method for producing a rare earth magnet, using a Y ₂ O ₃ powder having a particle diameter of 5 μm or more and 500 μm or less that is fired at a temperature of 1000 ° C. or more as a bed powder for sintering, A method for producing a rare earth magnet is characterized by sintering.

The present invention will be described in detail below. The rare earth magnet sintering bed powder of the present invention is yttria (Y ₂ O ₃ ) having a particle size of 5 to 500 μm, which is fired at a temperature of 1000 ° C. or higher.
Composed of powder. Although the performance of the spread powder is little affected by the shape of the spread powder, a spherical shape is preferable from the viewpoint of the function of the spread powder that reduces the contact resistance with the magnet molded body and improves sliding. This bed powder is usually obtained as a commercial product with a particle size of about 1
The Y ₂ O ₃ powder of μm is molded into an arbitrary shape, calcinated, crushed, and further calcinated at a temperature of 1000 ° C. or higher, and sieved for 5
It is also possible to use a dry granulation method in which the particle size is adjusted to a range of 500 μm, or a powdery Y ₂ O ₃ powder with a particle size of about 1 μm is added to a binder to form a slurry, and a spherical powder is directly produced using a spray dryer or the like. Alternatively, a wet granulation method may be used in which the particles are calcined at a temperature of 1000 ° C. or higher, sieved and adjusted to a particle diameter range of 5 to 500 μm. In the case of the dry granulation method, the corners of the particles are removed at the time of sieving and the shape becomes close to a sphere. Further, in the case of the wet granulation method, particles having a shape close to a true sphere can be obtained because the particles are solidified and dried in the air.

[0006]

[Function] As a performance required for the rare earth magnet sintering bed powder, there is no conventional sintering bed powder which has good sliding of the magnet molded body and is stable against the rare earth element contained in the magnet molded body. In the method of inserting the yttria plate, the shrinkage of the magnet compact does not proceed smoothly and evenly, and as a result, the dimensions of the magnet sintered compact are different between the top and bottom, and in the case of a ring-shaped sintered compact, it does not come into contact with the spread powder. There was a problem that the inner diameter and outer diameter of the set surface varied. The rare earth magnet sintering bed powder of the present invention is lower in cost than the conventionally used alumina and yttria plates, and suppresses cracking, chipping, deformation or dimensional variation of the magnet sintered body due to reaction during sintering. A magnet sintered body with good dimensional accuracy can be obtained.

Of the elements contained in the rare earth magnet, those having a strong activity are rare earth elements, and therefore Y ₂ O _{3 having} a lower free energy in the sintering temperature range of 1000 ° C. to 1300 ° C. than the oxide of the rare earth element. The best results were obtained when was used as bedding powder. If the particle size of the spread powder is less than 5 μm, the gap between the magnet molding and the sintering metal plate is extremely small, and the magnet molding and the sintering metal plate react, which is not preferable. If the thickness exceeds 500 μm, the reaction between the magnet compact and the metal plate for sintering does not occur, but the magnet sintered compact may have a dent in the part where the magnet compact and the spread powder are in contact with each other, or the spread powder This is not preferable because the weight per unit area increases and the amount of spread powder consumed also increases. Sintering temperature of rare earth magnet compact is 1000 ℃ ～
Since it is performed in the range of 1300 ° C, the sintering temperature of the sintering powder for sintering must be higher than the sintering temperature of the rare earth magnet compact so that unnecessary gas is not generated from the powder in this temperature range. There is. Further, in order to increase the strength of the spread powder so that the spread powder does not collapse during sintering, it is desirable to bake at 1300 ° C or higher. As a method for applying the spread powder to the metal plate for sintering, a slurry may be prepared using an organic solvent and applied with a brush, or may be sprinkled on the surface of the metal plate for sintering using a sieve or the like. .

[0008]

EXAMPLES The embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. (Examples 1 and 2) The bed powder for sintering was obtained by sieving Y ₂ O ₃ powder produced by a dry granulation method and having a particle diameter of 50 μm or less, 50 to 15 μm.
Example 1 was classified into 0 μm and 150 to 430 μm, respectively.
Used for. Also, the average particle size produced by the wet granulation method is 120
A μm Y ₂ O ₃ powder was used in Example 2. The magnet molding was ring-shaped with an outer diameter of 62 mmφ, an inner diameter of 39 mmφ and a height of 10 mm, and the magnetic powder used was Sm ₂ Co ₁₇ series. Sintering of the magnet molded body was carried out by sprinkling the spread powder on a metal plate for sintering with a sieve and placing the ring bottom surface of the magnet molded body on it, followed by firing at 1200 ° C. for 1 hour. As an evaluation method, the outer diameter of the upper and lower parts of the ring-shaped magnet after sintering was measured with a micrometer with an accuracy of 1 μm, and rounded to obtain data up to 10 μm, and the particle size of the spread powder affects the degree of dispersion. The impact was evaluated. The population was 45 for each case. The results of the examples are shown in Table 1. In the table, D1 and D2 represent the outer diameters of the upper and lower portions of the ring-shaped magnet, respectively. From these results, it can be seen that the dimensional accuracy of the example is remarkably improved as compared with the comparative example.

(Comparative Example) An average particle size of 3 as bed powder for sintering.
A magnet molding similar to that of Example 1 was sintered under the same conditions, except that a slurried metal plate for sintering was coated with a brush on a sintering metal plate using Y ₂ O ₃ powder of μm. The results are also shown in Table 1.

[0010]

[Table 1]

[0011]

According to the present invention, it is possible to manufacture a rare earth sintered magnet with high dimensional accuracy by using a powder for sintering a rare earth magnet, the yield is improved, and the cost is low and the performance is high. Since the product can be provided to the market, its utility value is extremely high in the industry.

Claims (1)

[Claims] 1. A method for producing a rare earth magnet, wherein a Y ₂ O ₃ powder having a particle size of 5 μm or more and 500 μm or less, which is fired at a temperature of 1000 ° C. or more, is used as a bed powder for sintering, and a rare earth magnet compact is baked. A method for manufacturing a rare earth magnet, which comprises bonding.