JPS5867801A - Preparation of rare earth/cobalt permanent magnet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for producing rare earth cobalt permanent magnets, and relates to a method for producing rare earth cobalt permanent magnets, in which a two-stage process of heating in an empty atmosphere and sintering in a reduced pressure argon gas atmosphere is performed.

3. Rare earth cobalt-based magnets are permanent magnets with higher coercive force and larger energy product than the alnico-based magnets and ferrite-based magnets that are widely used today. In recent years, demand has particularly increased, and they are used in a wide variety of fields, including the electronics industry.

In order to maximize the magnetic properties of rare earth cobalt magnet alloys, the manufacturing method is most important, and each process must be strictly controlled. In other words, rare earth metals have a strong affinity with oxygen, and are stronger than, for example, My＊hl, ss, etc., which are effective deoxidizers for ordinary steelmaking, so rare earth cobalt magnet alloys are chemically extremely active. It has properties not found in permanent magnetic materials.

Therefore, when manufacturing rare earth cobalt magnets, it is important to process them in an inert atmosphere, and in particular, a non-oxidizing atmosphere is most important during sintering, which is at a high temperature.

Therefore, various studies have been made regarding the manufacturing method of rare earth cobalt-based magnet alloys. For example, JP-A-52-44
No. 21 proposes that it is effective to use a hydrogen-containing atmosphere during sintering.

That is, the publication describes a samarium-cobalt-based magnet.

For stones, argon gas and water at normal pressure of 760 Torr [
Comparing the magnetic properties when sintered in an F atmosphere, it was found that the sintered density is better when sintered in hydrogen.
Stone density (Br), coercive force (Hc), energy ((B
The characteristics such as l+)max) are improved, and the
a &>.

The effectiveness of sintering in a hydrogen gas atmosphere is stated as reducing only

However, hydrogen gas has the lowest density of all gases and has a very high diffusion rate, so it easily leaks to the outside from, for example, minute holes in a sintering furnace. Moreover, when hydrogen burns, the amount of heat generated is extremely large, and when it is mixed with air over a wide range of 4 to 75 + Manufacturing requires extremely strict handling controls.

In view of the above-mentioned problems, this invention is easy to handle, inexpensive,
In addition, various studies have been conducted on sintering atmospheres that can improve the properties of sintered magnet alloys.

That is, this invention forms a molded body by molding and compressing cobalt containing a rare earth metal, the cobalt-copper alloy, the cobalt-iron-copper alloy, and the cobalt-iron-nickel-copper alloy into a shell, and forms this molded body into an IX 4-2 from room temperature to 800℃ or less in a vacuum atmosphere of 10 Torr or less
Raise the temperature at a rate of 0'C/m+n, then 50~3
950-1 in a reduced pressure argon gas atmosphere of 50 Torr
This is a method for manufacturing rare earth cobalt permanent magnets, the gist of which is sintering in a temperature range of 250°C.

Next, the manufacturing method according to the present invention will be explained in detail.

First, cobalt containing rare earth metals, the above-mentioned cobalt
Copper alloys, the above cobalt-iron-copper alloys Copalto iron-
A rare earth cobalt magnet alloy powder made of a nickel-copper alloy or the like is pulverized into a fine powder with an average particle size of 2 to 10 Am, and a compression molded body of a predetermined shape is produced using a press machine in a magnetic field or the like.

Next, oxygen, water vapor, hydrogen gas, etc. adsorbed or occluded in the compression molded body are promptly removed.
In order to maximize the effect of the subsequent sintering in a reduced pressure argon atmosphere, the following I) 11-stage treatment is performed.

That is, the temperature of the molded body is raised from room temperature to 800°C or less, but at the same time as degassing treatment, IX
4 to 2 in a vacuum atmosphere of 10 Torr or less
The reason for limiting the temperature increase rate to 0"c/mln is that at a temperature increase rate of less than 4℃/mtn, it takes more than 3 hours to raise the temperature to 800℃. It is unsuitable for sludge production, and even in a vacuum atmosphere, the molded body oxidizes during this period, and 20'Cy'm
If the rate exceeds i, the heating rate is too fast to sufficiently remove the adsorbed and occluded gas in the molded body, and the effect of improving properties by sintering in a reduced pressure argon atmosphere in the next step cannot be obtained. It's for a reason.

In this temperature raising process, approximately 90% of the adsorbed and occluded gas in the molded body is released at a temperature axis of 200 to 600 "C17", so the temperature increase rate in this temperature range is set to 4 to
b After degassing treatment while preventing oxidation by keeping it in a high vacuum atmosphere of Chenghuai, sintering is performed next, but at 800℃ after the above degassing treatment.
The process of increasing the temperature to a temperature range of 950 to 1,250°C, and the sintering process of maintaining a constant temperature in the above temperature range are performed using K, Sintering is performed in an argon gas atmosphere with a reduced pressure of 50 to 350 Torr.

In addition, although the atmospheric pressure in the cooling process after sintering is not particularly specified, in order to reduce the amount of argon gas extinguished and reduce costs, argon gas is used at a reduced pressure of 50 to 350 Torr. ! Cooling in a 6 m atmosphere is preferred.

Here, argon is the limiting reason for the atmospheric pressure.
When the pressure is low enough to cause no droplets, the vapor pressure of the rare earth cobalt magnet alloy components, especially the rare earth components, is 20 to 30 Torr at temperatures above 800°C. The composition of the aggregate will be different from the specified composition, resulting in severe deterioration of the magnetic properties.
The pressure shall be 0 Torr or more. In addition, when the pressure exceeds 350 Torr, as shown in Figure 1, which shows the relationship between the argon gas pressure and the obtained magnetic properties, a sufficient increase in density cannot be obtained, and at a crossroads there is no improvement. Since the magnetic properties cannot be obtained, the pressure is set to 350 Torr or less.

゛Also, the reason why the sintering temperature axis is limited is that for rare earth cobalt magnet alloys, the optimum sintering temperature axis varies depending on its constituent components and its composition V, but the optimum sintering temperature axis is 950℃.
The sintering temperature of Kokuyu does not produce sufficient sintered density, and sintering temperatures exceeding 1250°C melt the alloy.
950 because it does not form a sintered body with good characteristics.
An example according to the present invention was constructed using a seeding temperature of 7 cm and 1250° C. to clarify its effects.

Implementation fl”1 $1. bj 99.9- or more Sm 33.8wt9
A base alloy consisting of 66.2 wt % Co with a b1 purity of 99.91 or higher was produced by arc button oxidation. Similarly, an additive alloy consisting of 5m60 wt% and Co40 wt% was prepared.

Next, after coarsely pulverizing the base alloy and the additive alloy, 50 yr of the base alloy and 6 ft of the additive alloy were mixed, and the mixture was placed in a ball mill with 120 cc of organic solvent and 500 yr of stainless steel pole, mixed and finely pulverized to 2 to 10 μm.
It was made into a fine powder. Subsequently, the fine powder was press-molded in a magnetic field of 10 KOe to produce a compression-molded body.

Next, the molded body was heated to 700°C in a vacuum atmosphere of I x 10 Torr at a heating rate of 10"C/mlB, and then heated at 1140°C for 1 hour in a reduced pressure argon gaff atmosphere of 200 Torr. After sintering, the furnace was cooled in the same atmosphere.
``IC'' was subjected to aging treatment for 5 hours to obtain a magnet according to the method of this invention.9.

9. As a comparative example, the above molded body was subjected to heating, sintering, and furnace cooling 1 aging treatment in a normal pressure argon gas atmosphere of 760 Torr using exactly the same heat pattern as the method of this invention described above to obtain a magnet. .

The magnetic properties of the obtained permanent magnet are shown in Table wi.

As is clear from Table 1, it can be seen that the rare earth cobalt based magnet produced by the method of the present invention has superior properties to the comparative example in which the magnet is sintered in an argon gas atmosphere at normal pressure.

Table 1 Actual power & Example 2 Pure jf 99.9 yen Sm 17.1 w - and P
r 16.0wt%.

A base alloy consisting of 1599.996 pure CO66.9wt rice and an additive alloy consisting of 5m60wt% and CO40wtl were prepared in the same manner as in Example 1, and then coarsely ground. Then, 50 yr of the base alloy and 6 yr of the additive alloy were blended, and a compression molded body was produced in the same manner as in Example 1.

This molded body was heated to 700°C in an empty atmosphere of I x 10 Torr at a rate of 1 oz min, and then heated to 1090°C for 1 hour in a reduced pressure argon gas atmosphere of 200 Torr. After sintering, the magnet was cooled in a furnace and further subjected to aging treatment at 900'C for 5 hours to obtain a permanent magnet according to the method of the present invention.

In addition, as a comparative example, a magnet was produced under conditions in which the sintering atmosphere was a normal pressure argon gas atmosphere of 760 Torr, and the heat pattern was flush with the method of the present invention described above.

The magnetic properties of the obtained permanent magnet are shown in Table 2.

Table 2 Example 3 Sm27.0wt1 with a purity of 99.9 or higher, a purity of 99.
81 or more Co 419wt (F @ 13.2wt)
Ni8. An alloy consisting of Owt'lG and Cu 7.9wt1G was high-frequency melted in an argon atmosphere and coarsely ground in an iron mortar. The coarsely ground powder was ball milled in an organic solvent to form a fine powder of 2 to 105 m. This fine powder was press-molded in a magnetic field of 12 KOe to produce a compression-molded body.

Next, the molded body was heated to 800°C at a rate of 10°C/min in a vacuum atmosphere of I x 10 Torr, and then heated at normal pressure (760 Torr) at 560 T/min.
b r r, 360Torr, 260Torr1
200Torr%60Torrs O,ITorr7
1200' in a reduced pressure argon gas atmosphere of plugs.
Sintering was carried out for 2 hours, followed by rapid cooling.

Next, an aging treatment was performed at 800° C. for 4 hours, and the characteristics of the obtained magnet were measured. The relationship between the argon gas atmosphere pressure and the magnetic characteristics is shown in FIG.

Table 3 shows the case where the argon gas atmosphere pressure is 200 Torr, which is the method of this invention, and the case where the pressure is 760 Torr as a comparative example.
It shows the magnetic properties of the magnet in the case of r.

3. The method of the present invention, in which the temperature is raised to 800'C or less in a surface air atmosphere and then sintered in a reduced pressure argon gas atmosphere, is effective in improving density and the accompanying improvement in magnetic properties. was obtained and was excellent.

Rare earth cobalt magnets can be manufactured.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the argon gas pressure in the sintering atmosphere and the magnetic properties of the resulting magnet.Applicant: Sumitomo Special Metals Co., Ltd.

Claims (1)

[Claims] l The rare earth cobalt magnet alloy powder is made into a compression molded body, and this molded body is heated from room temperature to 800°C or less in a vacuum atmosphere of I X 10 Torr or less for 4 to 20 degrees Celsius.
The temperature was raised at a rate of C/min, then 50-350To
r r950-1250 in a reduced pressure argon gas atmosphere
A method for manufacturing a rare earth cobalt permanent magnet, characterized by performing sintering at a temperature range of ℃.