JPS59154004A - Manufacture of permanent magnet - Google Patents

Abstract

PURPOSE:To obtain a permanent magnet with excellent magnetic characteristics by a method wherein R-Co system, such as RCo5 system and R2Co17 system, alloy powder is sintered by two steps at the specific temperature in each system. CONSTITUTION:R-Co system, such as RCo5 system and R2Co17 system, alloy powder is molded, sintered and subjected to thermal treatment to produce a permanent magnet. In the sintering process, the 1st step of the process is performed the temperature at which liquid phase exists partially, and the 2nd step is performed at the temperature 10- 100 deg.C lower than the 1st step. The sintering time of the 1st step is preferably short, that is to say, about 5-60min in order to obtain a high density sintered body and at the same time prevent crystal particles from becoming rough and large and prevent the liquid phase from oxidization. If the sintering temperature of the 2nd step were not lower than that of the 1st step by at least 10 deg.C, although the density of the sintered body would become high, the crystal particles would not be prevented from growing rough and large and the liquid phase would not be prevented from oxidization so that the 2nd step of the sintering process would be of no effect. If the temperature of the 2nd step were to low, that is to say, more than 100 deg.C lower than that of the 1st step, diffusion of the alloy elements would be slow and the sintering reaction would be significantly deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to RCo, 5 series, which is an intermetallic compound of rare earth metal (R) and cobalt (CO).

The present invention relates to a method for manufacturing R-Co based sintered permanent magnets such as R2Co and 7 series.

R-Co rare earth cobalt magnets are conventional alnico,
Their magnetic properties are significantly superior to that of ferrite magnets, so their demand has been rapidly increasing recently, although they are more expensive.

Rare earth metal elements used in R-Co-based sintered permanent magnets such as RCo5-based and R2C017-based include Y and L.
a, Ce, Pr, Nd, Pm.

Sm, Eu, Gd, Tb, Dy, Ho, Er.

It contains one or more of Tm, Yb and Lu". On the other hand, in addition to cobalt (Co) alone (that is, RCo5 type), a part of CO is Fe and Cu.

Ni, Cr, Mn, Ti, Zr, Hf, V.

Nb, Ta, Mg, B, Sn, St, A sentence.

Alloys substituted with one or more of Ge, Ir, Mo, Te, Th, W, Zn and Be (i.e. R2(Co,
Cu, Fe)r system, R2(Co, Cu, Fe, M)
t7 series).

Generally, R-Co permanent magnet alloys such as RCo5 series + R2CO17 series are produced by finely pulverizing the magnet alloy material to form a powder, aligning the powder in a certain direction in a magnetic field, shaping it, and then sintering and heat-treating it. It is obtained through the process. When manufacturing such an R-Co permanent magnet by a powder metallurgy method, it is necessary to increase the density of the sintered body in order to obtain high magnetic properties, particularly a high residual magnetic flux density Br.

Therefore, conventionally, in order to increase the density of a sintered body, liquid phase additives are often added to the raw material powder, or liquid phase sintering is often performed at a temperature at which a part of the alloy becomes liquid.

In this conventional method, 1. If sintered at a higher temperature, the density of the sintered body can be increased, but the crystal grains will become coarser, leading to a decrease in coercive force Hc, especially in RCo5-based sintered alloys. Even if liquid phase sintering is performed in an inert atmosphere, some oxygen (02) is still included, so oxidation of the liquid phase progresses due to long-term heating, and as the oxidation progresses, sintering There were drawbacks such as reaction inhibition and deterioration of magnetic properties.

Therefore, in the conventional case, the sintering temperature has been selected in consideration of preventing coarsening or oxidation of crystal grains and increasing the density of the sintered body.

The present inventors have discovered that R-Co such as RCo5 series, R2Co, and 7 series
As a result of detailed investigation of the liquid phase sintering mechanism of alloy powders, it was found that high density was achieved by performing the first stage sintering for a short time at a temperature associated with the liquid phase, and then the first stage sintering 10~ from temperature
Re-sintering at a temperature 100°C lower prevents coarsening of crystal grains, suppresses oxidation of the liquid phase, and eliminates voids due to diffusion, achieving even higher density. I discovered that it can be done.

This invention was made based on the above knowledge, and the RC
2 R-Co alloy powders such as o5 series + R2C017 series
The present invention aims to provide a method for manufacturing a permanent magnet with excellent magnetic properties by sintering it in stages or more.

That is, the present invention provides a method for producing a permanent magnet by molding, sintering, and heat treating R"Co alloy powder such as RCo5 series and R2C017 series, and in the sintering process, at a temperature partially accompanied by a liquid phase. After the first stage sintering is performed, the second stage sintering is performed at a temperature 10 to ioo'c lower than the first stage temperature.

The present invention will be described in detail below.

RCo5 series, R2O subjected to this invention method.

R-Co alloy powder such as No. 17 alloy powder is composed of an intermetallic compound of a rare earth metal (R) and cobal (Co'). This rare earth metal (R) includes Y, La, Ce,
Pr, Nd, Pm, Sm.

Eu, Gd, Tb, DV, Ha, Er, Tm.

It is selected from one or more rare earth elements such as Yb and Lu. On the other hand, Cobal (Co) is not only Co alone (i.e. RCo5 system) but also contains a part of Co such as Fe, Cu,
Ni, Cr, Mn, Ti.

Zr, Hf　, V, Nb, Ta, Mg, B, Sn.

St, AJlj, Ge, Ir, Mo, Te, Th.

Alloy system substituted with one or more of W, Zn and Be (
That is, R2 (Co, Cu, Fe) + 7 system, R2 (
Co-, Cu, Fe, M) + 7 series) are also included.

When manufacturing permanent magnets, these RCo5 series + R
One or more types of R-Co alloy materials such as 2C017 series are selected and pulverized to a predetermined average particle size to form a fine powder, and rare earth elements are added to Co (and other metals) at a predetermined level. Each powder is weighed and mixed to make a sintering raw material.

Next, the raw material powder is filled into a mold and compression molded in a magnetic field in a fixed direction to obtain an intermediate molded body. Next, the intermediate compact is sintered and heat treated to produce a final product, a permanent magnet.

In the above-mentioned sintering step, the present invention performs the first stage sintering at a temperature partially accompanied by a liquid phase, and then
The feature is that the second stage sintering is performed at a temperature lower than -ioo°C. That is, the first stage of sintering is carried out for a short time on an intermediate molded body formed from fine powder in an inert atmosphere such as argon (Ar) at a temperature that is partially accompanied by a liquid phase. The sintering time of this first stage is preferably 5 to 6
The short sintering time is approximately 0 minutes to increase the density of the sintered body, and the short sintering time prevents coarsening of crystal grains and at the same time prevents oxidation of the liquid phase.

The next second stage sintering is performed at a temperature of 10 to
Perform at a temperature 100°C lower. The reason why the sintering temperature of this second stage was limited to a temperature 10 to 100°C lower than the sintering temperature of the first stage is that there is no difference of more than 10°C from the sintering temperature of the first stage. Although the density of the sintered body becomes higher, coarsening of crystal grains or oxidation of the liquid phase cannot be prevented.
This is because there is no effect of sintering in the second stage. On the other hand, at low temperatures where the difference exceeds 100°C, the sintering temperature is too low, the diffusion of alloying elements is slow, and the sintering reaction is extremely This is because it becomes worse. Therefore, in practice, the temperature is preferably 10 to 100° C. lower than the first stage sintering temperature.

In this way, sintering the intermediate compact in two stages not only makes it possible to increase the density of the sintered compact, but also prevents coarsening of crystal grains and oxidation of the liquid phase. It has become possible to manufacture permanent magnets with excellent properties.

In addition, it is also possible to sinter the product in three or four or more stages, but this increases the manufacturing cost and does not significantly increase the effectiveness, so sintering in two stages is sufficient. I was able to get a great effect.

Hereinafter, examples of this invention method will be given and explained in more detail.

Example 1 This example is an example of manufacturing a permanent magnet of RC-Cl5 series, and first, 34.5% by weight of Sm-C.

The alloy and the 60% by weight Sm-Co alloy were each finely pulverized until the average particle size became 4 tiles, and the above fine powders were weighed and mixed so that the S weight was 36% by weight, and then a compacting pressure of 1 ton was applied. /cm2 in a magnetic field to obtain an intermediate molded body. Next, the intermediate compact was subjected to a first stage sintering at a temperature of 1240° C. for 15 minutes under an Ar atmosphere, followed by a second stage sintering at a temperature of 1180° C. for 3 hours.

After the sintered body was slowly cooled to room temperature, it was further heated to 900°C.
A permanent magnet was manufactured by adding heat treatment for 1 hour. For comparison, permanent magnets were manufactured using a conventional sintering method using alloy powders of the same composition, and the properties of the sintered bodies were compared.

The results are shown in Table 1.

As is clear from Table 1, the permanent magnet N according to the method of the present invention
It was found that O and L had a high density of 8.35 (g/cm3) and excellent magnetic properties. On the other hand, in the conventional method, permanent magnets No. 2 were sintered at a high temperature, but the sintering time was too short, so sintering was not performed sufficiently, and the magnetic properties were not so good. No again
The permanent magnets of , , and 3 were sintered at high temperature (1240°C) for a long period of time, which made it possible to increase the density, but the coercive force (RHO) was extremely low at 4.1 KOe due to coarse crystal grains. Furthermore, No. 5, sintered at a lower temperature
It was found that permanent magnet No. 6 had a low density due to the low sintering temperature, and therefore the residual magnetic flux density (Br) was low in all cases.

Example 2 A 16.8 wt % Sm-16.3 wt % Pr-Co alloy and a 60 wt % Sm-Co alloy were each finely ground to an average particle size of 4 l, and mixed at a ratio of 94:6. As in Example 1, compression molding was performed in a magnetic field to obtain an intermediate molded product. Next, the intermediate molded body was subjected to a first heating at 1150°C for 10 minutes.
After performing the second stage sintering, a second stage sintering was performed at 1120°C for 4 hours, and after cooling to room temperature, a heat treatment was added at 900°C for 1 hour. For comparison, permanent magnets were manufactured using the conventional sintering method using alloy powders of the same composition, and their properties were investigated. The results are shown in Table 2.

As shown in Table 2, permanent magnet N007 according to the method of the present invention
It had a high density and excellent magnetic properties. On the other hand, conventional permanent magnet No. 8.

9, the magnetic properties were not very good.

Example 3 This example is an example of manufacturing an R2Co, 7-based permanent magnet, in which 26% by weight Sm-12% by weight Cu-8% by weight
The Fe--Co alloy was finely pulverized to an average particle size of 4 l, and compression molded in a magnetic field at a molding pressure of 1 ton/am2 to obtain an intermediate compact. Then, the obtained intermediate molded body was heated to 124
After the first stage sintering at 0°C for 20 minutes, 1220
A second stage sintering was carried out for 1 hour at °C. Furthermore, 11
After performing solution treatment at 90° C. for 2 hours, it was rapidly cooled to room temperature. Next, it was aged at 800°C for 2 hours, slowly cooled to 400°C at a rate of 1'07 ml, and kept at 400°C for 1 hour.
It was aged for 0 hours. The results are shown in Table 3 together with the conventional method.

As shown in Table 3, the permanent magnet produced by the method of the present invention had a high density and excellent magnetic properties. On the other hand, conventional permanent magnet No. 11°12.13 did not have very good magnetic properties.

Example 4 25 wt% Sm-4 wt% Cu-22 wt% Fe-3 wt% Zr-0.05 wt% B-Co alloy with average grain size 4K
The resulting intermediate compact was pulverized at 1220°C for 15 min.
After performing the first stage sintering for 1 minute, the second stage sintering was performed at 1210°C for 1 hour. Furthermore, after performing solution treatment at 1170°C for 2 hours, it was rapidly cooled to room temperature. Furthermore, it was aged at 825℃ for 15 hours and 1℃/1℃ up to 400℃.
The sample was cooled slowly at a rate of 10 min, and aged at 400'O for 10 hours. The results are shown in Table 4 along with the conventional method.

As shown in Table 4, the permanent magnet produced by the method of the present invention had a high density and excellent magnetic properties. On the other hand, the magnetic properties of the conventional permanent magnet No. 15°16.17 were not so good.

As is clear from the above description, according to the present invention, R
Co5 system + R2Co17 system etc. (7) R-C.

When producing permanent magnets by molding, sintering, and heat treating alloy powder, the sintering process is divided into multiple stages, and in the first stage, liquid phase sintering at high temperature is performed. After that, in the second stage of sintering, the crystal grains are coarsened by sintering for a long time at a temperature lower than the first stage's sintering temperature. In addition to completely preventing oxidation of the liquid phase, we further promote the densification of the sintered body, so the sintered body has a high density and does not coarsen the crystal grains. This has the remarkable effect that an R-Co permanent magnet having excellent magnetic properties can be obtained.

Claims (1)

[Claims] (1) R-G such as RCo5 series + R2COl 7 series. In producing a permanent magnet by molding, sintering, and heat treating the alloy powder, in the sintering step, after performing the first stage sintering at a temperature partially accompanied by a liquid phase, the first stage A method for manufacturing a permanent magnet, characterized in that the second stage of sintering is performed at a temperature 10 to 100° C. lower than the eye temperature.