JPS5848603A - Production of magnet of intermetallic compound - Google Patents

Abstract

PURPOSE:To produce a permanent magnet having excellent density and magnetic characteristics in the stage of producing a permanent magnet by sintering the powder of an intermetallic compd. of rare earth elements and Co by changing over a sintering atmosphere plural times to a vacuum or inert gaseous atmosphere. CONSTITUTION:An intermetallic compd. consisting of rare earth elements such as Sm and Co as raw material for magnets is pulverized down to about 3mu. After the powder is compression molded to moldings in a magnetic field, the moldings are heated in a vacuum atmosphere until the sintering temp. of the moldings is attained. During the time until solutionization is finished, the atmosphere is subjected to plural times of cycles like substitution with gaseous Ar-evacuation-substitution with gaseous Ar. According to this method, the magnet of a rare earths-Co intermetallic compd. having density higher than 95% theoretical density and having excellent magnetic characteristics is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the magnetic properties of a sintered intermetallic compound magnet containing rare earth elements and cobalt as main components. Among intermetallic compounds such as rare earth elements and cobalt, especially Roof
, R50Ost (R is a rare earth element) intermetallic compounds have high crystal magnetic anisotropy and are known to be high-performance magnets.

Their production is roughly divided into the resin binding method, in which fine powder is hardened with resin such as plastic, and the sintering method, in which the fine powder is compressed and then fired at an appropriate temperature. Sintering is the mainstream method because it maximizes performance.

The reason why sintered magnets have better magnetic properties than resin-bound magnets is that the density of resin-bound magnets is at most 8 the theoretical density.
This is largely due to the fact that the sintering method allows densification to 95% or more of the theoretical density, whereas the density is 0-.

In a fine powder magnet, the magnetic properties of the magnet are By = 4π engineering sP
It can be expressed as (knee: saturation magnetic flux density, P: powder filling rate), but according to the formula, increasing the powder filling rate is an important factor in improving magnetic properties. I understand.

In other words, the sintering process is essential for improving the performance of rare earth magnets.

Sintering temperature in sintering rare earth cobalt magnets.

Although time is an important factor that influences magnetic performance, it is well known that the atmosphere during sintering is also important. Conventionally, the sintering atmosphere for rare earth cobalt magnets was usually either vacuum or inert gas, but when sintering was performed in a vacuum atmosphere, the evaporation of rare earth elements during the sintering process The drawback is that it causes significant variations in the properties within the sintered body, making it difficult to produce stably.

On the other hand, when sintered in an inert gas such as argon gas,
It is effective in preventing evaporation of rare earth elements, but the density after sintering is limited to a 30 gr, /17 (theoretical density of 96 cm).
This was an obstacle to improving magnetic properties.

The present invention presumes that the sintering atmosphere is closely related to the densification of the sintered body, and as a result of various experimental studies, the sintering atmosphere is kept in a vacuum until the desired sintering temperature is reached, and thereafter. This is based on the discovery that the density and magnetic properties of the sintered body can be improved by replacing the atmosphere multiple times (alternating with vacuum and inert gas) until the end of sintering.

The present invention will be explained below using examples.

[Example 1] First, a comparative sample was prepared by a known method. Introduction 8m54vt96. An alloy consisting of 64 wt% Oo was pulverized to an average particle size of 5 microns, and then compression molded in a magnetic field of 10,000 oersted with an r force of S ton/J.
Next, this green compact was heated at 1120°C in an argon gas atmosphere.
℃, 11! After sintering at temperatures of 1°C, 114°C, and 1150°C for 1 hour, thermal aging treatment was performed at 850°C for 1 hour, and the density magnetic properties of the sintered bodies were measured.

Next, the samples of the present invention were subjected to exactly the same steps as the conventional method described above, from composition to compressed bottom shape, and then sintered at the same temperature as the comparative samples. The atmosphere during sintering was a vacuum atmosphere until the desired sintering temperature was reached, and thereafter the atmosphere was alternately replaced with vacuum and argon gas several times until the heating was completed for 1 hour.

After sintering, thermal aging treatment was performed at 850°C for 1 hour, and the density and magnetic properties of the sintered body were measured.

! ! -1 shows the density and magnetic properties of samples produced by the conventional method and the method according to the present invention.

Table 1 From the above examples, it is recognized that the magnetic properties of the sintered magnet produced by the manufacturing method of the present invention are clearly higher than those produced by the conventional method.

[Example 2] First, 8m2a5wt%, Fe 1! LOWt
%, Zu 8vyt%, Zr 1.5vt%, balance co
The alloy was pulverized using a vibrating mill to an average particle size of 4 microns, and the resulting fine powder was compression molded in a magnetic field of 10 KOe. After compression molding, the heat treatment atmosphere, which is a characteristic of the present invention, was changed to 1160°C to 1200°C.
1 hour at a temperature of 1150℃ to 1180℃.
Solution treatment was carried out at .degree. C., and after cooling, the material was heated to 850.degree. C. for thermal aging. In the conventional method, the atmosphere during heat treatment was a vacuum until the solutionization was completed, and then an argon gas atmosphere. In the present invention, the atmosphere was kept in a vacuum until the predetermined sintering temperature was reached, and then the atmosphere was kept in a vacuum until the solutionization was completed. During this time, this cycle was repeated multiple times: argon gas replacement → vacuum evacuation → argon gas replacement.

Table 2 shows the maximum magnetic properties obtained and the sintered body (10ss
100 pieces each were prepared with an outer diameter of 1.25-φ, an inner diameter (L4 static φ, and a thickness of L 5 m) by grinding the sintered body. The results of measuring the surface magnetic flux density using the element are shown.

Table 2 According to Table 3, the maximum magnetic properties obtained by the conventional method are when processed in vacuum (BH) ynaxIF! h
2 M, G-Oe, and in argon gas treatment (
According to the method of the present invention, (BH)max 2 [
It also reaches 11M, G, Oe. Further, even when the micro parts are processed from the raw material produced by the method of the present invention, a higher surface magnetic flux density can be obtained compared to the conventional method, and at the same time,
There is little variation, and the effects of the present invention are remarkable.

As explained above, in the production of sintered deaf rare earth cobalt-based intermetallic compound magnets, the heat treatment atmosphere is kept in a vacuum until the desired sintering temperature is reached, and then the atmosphere is replaced with argon gas and then vacuumed until the heat treatment is completed. According to the method of the present invention, which is characterized in that the atmosphere is replaced by pulling → argon gas replacement and the atmosphere is replaced multiple times, the RcoB system vR1oo1? In either system, it is possible to obtain higher magnetic properties than conventional methods.

Above and below Applicant: Daini Seikosha Co., Ltd.

Claims (1)

[Claims] In a method for manufacturing rare earth cobalt-based intermetallic compound magnets by sintering, the sintering atmosphere is kept in a vacuum until the desired sintering temperature is reached, and thereafter, until sintering is completed,
A method for manufacturing a rare earth cobalt-based intermetallic compound magnet, characterized by replacing the atmosphere multiple times (alternating between a vacuum and an inert atmosphere).