JPS6048883B2 - Permanent magnet manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to samarium (Sm)-cobalt (Co) based permanent magnets, particularly Sm.

Regarding the manufacturing method of Co-based permanent magnets, in more detail, it has excellent magnetic properties such as residual magnetic flux density (Br), coercive force (IHc), and maximum energy product ((BH) max), and has good oxidation resistance. The present invention also relates to an excellent method of manufacturing permanent magnets.
Conventionally, various compositions have been proposed for permanent magnets of the RM system (R is a rare earth element such as Sm, Ce, Y, etc.; M is Co and a metal element such as Cu, Fe, etc. together with Co). For these permanent magnets, the maximum energy product ((BH) max) and residual magnetic flux density (Br) are particularly important characteristics in applications such as motors, and it is desirable that these values be as large as possible.

However, these values also depend on the coercive force (IHc) of the magnet.
It is difficult to increase it unless it exceeds a certain value. Therefore, in order to obtain a permanent magnet with large (BH)max and Br, it is necessary to increase IHc.
By the way, Sm.

(Co, Cu, Fe, Ti) system magnets, it is known that Br can be increased by increasing the Fe content or decreasing the Cu content. However, increasing the Fe content or C
As IHc decreases when u content is reduced, F
By increasing the e content and decreasing the Cu content, Br and (B
H) max cannot be improved. Therefore, the composition of conventional sm2 (Co, Cu, Fe, Ti) magnets has been determined with the aim of increasing Br as much as possible while maintaining IHc above a certain value. For example, in Japanese Patent Publication No. 55-15096, 10
~3% Y and other rare earth elements, 0.2-7% by weight
Ti, 5-20 wt% Cu, 2-15 wt% JF
e) Permanent magnets made by molding metal powder whose main component is Co in a magnetic field and then sintering it have excellent oxidation resistance and IHc,
It is disclosed that it has excellent magnetic properties such as (BH)Max. Also, in Japanese Patent Application Laid-open No. 52-109191,
23-3% Sm, O. 2-1.5 wt% Ti,
A permanent magnet is disclosed in which a metal powder whose main components are 9 to 13% by weight Cu, 3 to 12% by weight Fe, the balance being CO is molded in a magnetic field and then sintered. However, these compositions are the result of compromising adaptation to changes in residual magnetic flux density and coercive force that occur with variations in Cu content and Fe content, so they cannot necessarily be said to be sufficient. It was hot.

By the way, if you can reduce the Cu content that lowers Br, increase the Fe content that improves Br, and simultaneously maintain IHc above a certain value, you can create a permanent magnet with excellent magnetic properties with large Br and (BH)Max. can be obtained.

In order to achieve the above-mentioned problems, the present inventors conducted extensive research on the composition and heat treatment process of the alloy that constitutes the permanent magnet, and as a result, the composition of the alloy was determined to be Sm (CO, Cu, Fe, Ti).
When expressed by the formula of z, if Z > 6.9 and a specific aging treatment is performed after sintering, IHc increases even by increasing the amount of Fe and decreasing the amount of Cu, contrary to conventional knowledge. Based on this finding, we found that Br and (BH
) Max. He developed a highly improved permanent magnet and has already applied for a patent as Japanese Patent Application No. 103434/1983.

In order to further improve the magnetic properties and oxidation resistance of Sm2cO, permanent magnets, the present inventors have conducted further research on the composition and treatment process of permanent magnets, and as a result, have found that metal powders of various compositions have been sintered. The fact that after sintering, the IHc of the obtained permanent magnet increases significantly if the sintered body is held at a temperature of 600°C or more and less than 700°C for a predetermined time and slowly cooled at a cooling rate of 5°C/Min or less. This discovery led to the completion of the present invention.

3. The present invention uses Sm which has excellent magnetic properties such as Br, (BH)Max, and IHc, and also has excellent oxidation resistance.

The purpose of this invention is to provide a method for manufacturing a CO,, system permanent magnet. The method for manufacturing a permanent magnet of the present invention includes samarium 2
64-2% by weight, 0.2-3% by weight of titanium, and 3-3% by weight of copper.
9% by weight of iron, 10-14% by weight of iron, and the balance mainly of cobalt.
It is characterized in that after being maintained in a temperature range below °C for a predetermined period of time, it is slowly cooled at a cooling rate of 5 °C or less per minute.

In the raw metal powder, the Sm content is 26 to 29% by weight, and if it is less than 2% by weight, there is no increase in IHc, and if it exceeds 29% by weight, IHc decreases and at the same time Br. (BH) Max cannot be increased.

Ti is 0.2 to 3% by weight, and Ti is 0.2 to 3% by weight. When the heel weight is less than %, IHc does not increase significantly, and when it exceeds 3% by weight, Br decreases. Cu is 3 to 9% by weight, and if it is less than 3% by weight, no increase in IHc can be achieved;
If it exceeds % by weight, Br decreases and at the same time the heat treatment effect described below decreases, and as a result, (BH)Max does not particularly increase. Fe is 10 to 14% by weight, and if it is less than w weight%, the heat treatment effect is small, and if it exceeds 14 weight%, IHc decreases and the heat treatment effect is small,
Therefore, (BH)Max decreases. The remainder of the raw metal powder is CO. The permanent magnet of the present invention is manufactured as follows.

That is, first, a predetermined pressing die is filled with metal powder having the above-mentioned mixing ratio, and then compression molded in a magnetic field to form a molded body.The molded body is then placed in an inert atmosphere such as vacuum, nitrogen, or rare gas. sinter. The sintering temperature is usually 1050-1250°C. The obtained sintered body is then subjected to a predetermined heat treatment, which is the second feature of the present invention. That is, first, the sintered body is held in an inert atmosphere as described above at a temperature of 600° C. or more and less than 700° C. for a predetermined period of time. When the processing temperature is outside this range, the IHc and (BH)Max of the obtained permanent magnet decrease significantly. Further, at this time, the processing time is usually 0.1 seconds to 1 hour, which is sufficient. Thereafter, the sintered body is slowly cooled at a cooling rate of 5°C/Min or less to become the permanent magnet of the present invention.

At this time, when the cooling degree is greater than 5°C/Min,
Increase in IHc is not sufficient.

The present invention will be explained below based on examples.

First, a permanent magnet was manufactured as follows. Each metal element was blended in a predetermined composition ratio, approximately 4k9 of the mixture was melted in a vacuum high-frequency induction heating furnace, and then cooled, and the resulting ingot was coarsely ground and then ground in a jet mill to form a fine powder. This fine powder was filled into a predetermined pressing die, and compression molded at a pressure of 2t0n/d while applying a magnetic field of 20,000 Oe. The obtained molded body was subjected to a sintering treatment at a predetermined temperature and a predetermined time in an argon atmosphere, and then immediately cooled to room temperature, then held again at a predetermined temperature for a predetermined time, and then subjected to an annealing treatment. In the following, % represents weight %. Example 11Hc
, (BH)Max(7) Cu content dependence and effect of heat treatment Composition: Sm27.7%, TiO. 7%, Fell. 8%
, CU2-11.5%, CO balance Sintering conditions: 1195°C x 1 hour Heat treatment: After holding at 650°C for 1 hour, slow cooling at a cooling rate of 2°C/Min.

For comparison, another permanent magnet (Comparative Example 1) was manufactured in the same manner as in Example 1, except that no heat treatment was performed.

The Cu content of the obtained permanent magnet and IHc, (BH)Ma
The relationship with x is shown in Figure 1.

In the figure, curve A: IHc of Example 1, curve a: 1. 'Hc, curve B: (BH)Max of Example 1
) Curve b: represents (BH)Max of Comparative Example 1. As is clear from the figure, the permanent magnet of the present invention has a large IHc even with a CU of 9% or less, and the peak of (BH)Max, which was CU: 10 to 11% before heat treatment, is 7 to 8.
% or less, and the value of (BH)Max also increases considerably.

Example 2 Samples 21 to 23 according to Example and comparative sample 21
-31 were produced.

The composition and sintering conditions of each sample are shown in the table. The conditions for the heat treatment were as follows. The heat treatment patterns indicated by numbers in the table are as follows. 1: 1 at 650℃
Slow cooling at +2°C/Min.

2: Slow cooling at 600°C for 1 hour + 100C/Mln.

3: Cool slowly at 750°C for 1 hour + 2°C/Min.

4: Slowly cool at 550°C for 1 hour + 2°C/Min.

Comparative examples have compositions or heat treatments outside the scope of the present invention. Br, I[ C, (BH
) Max is also listed in Table 1. Example 3 Dependence of (BH)Max on cooling rate Composition: Sm27.7%, TiO. 7O%, Cu7.9%
Fell. 8%, CO balance.

'0 Sintering conditions: 1195°C x 1 hour Heat treatment: After holding at 650°C for 3 times, slowly cooling at various cooling rates.

FIG. 2 shows the relationship between the (BH)Max of the obtained permanent magnet and the cooling rate.

As is clear from the figure, (BH)Max increases when the cooling rate is 5°C/Min or less.

As explained above, the permanent magnet obtained by the present invention has significantly improved magnetic properties.

This is R for Sm2cO, 7 series permanent magnets. C
The structure has a two-phase separated cell structure consisting of O, , and RC phases, and this is thought to be due to improvements in the structure morphology and the magnetic properties of both phases. In addition,
Since the permanent magnet obtained by the present invention contains Ti, its oxidation resistance is also improved.

[Brief explanation of the drawing]

Figure 1 shows the IHc, (BH)Max (7) Cu content dependence and the effect of heat treatment, and Figure 2 shows the (BH)Max and cooling rate of the permanent magnet with the composition shown in Example 3. It is a relationship diagram.

Claims (1)

[Claims] 1 26-29% samarium and 0.2-3% titanium
% by weight, 3-9% by weight of copper, and 10-14% by weight of iron.
The remainder is sintered metal powder, which is mainly cobalt, and
A method for manufacturing a permanent magnet, which comprises maintaining the temperature in a temperature range of 0°C or more and less than 700°C for a predetermined period of time, and then slowly cooling it at a cooling rate of 5°C or less per minute.