JPS6347301A - Production of permanent magnet powder - Google Patents

Abstract

PURPOSE:To produce permanent magnet powder having superior magnetic characteristics and useful for a resin magnet or the like by pulverizing a sintered body of a permanent magnet alloy and heating the resulting powder. CONSTITUTION:An ingot of a permanent magnet alloy represented by a formula RxMyBz (where R is one or more kinds of rare earth elements, M is Fe and/or Co, 8<=x<=30, 2<=z<=20 and y=100-x-z) is cast. The ingot is crushed, sintered and aged, the aged sintered body is pulverized to <=10mum particle size and the resulting powder is heat-treated at 500-1,000 deg.C. Thus, the coercive force reduced by the pulverization is restored and the permanent magnet powder usable for a resin magnet or the like is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for producing permanent magnet powder used in resin-bonded magnets and the like.

C. Background Art Recently, high-performance sintered permanent magnets containing rare earth elements have been developed. Among such rare earth permanent magnets, rare earth-Fe-B magnets are attracting attention as having superior magnetic properties than rare earth Co magnets.

This magnet has extremely high (BH)ll1ax, so
It is expected that it will be used as a material for resin-bonded magnets (hereinafter referred to as "resin magnets"), which are in high demand and have strong demands for smaller size and lighter weight.

However, this method of obtaining magnetic powder from rare earth-Fe-B alloys has the following problems, and the reality is that no product with satisfactory performance has yet been obtained. For example, a method of heat-treating an ingot obtained by melting a rare earth-Fe-B alloy using an arc furnace, etc., and then crushing it to obtain a powder heat-treats the fine metal structure, which is a factor in having a high coercive force. It is extremely difficult to form in a process. On the other hand, in the case of a method in which a sintered magnet with high magnetic properties is first created by a normal powder metallurgy method and then finely pulverized, 200 to 3
When finely pulverized to a particle size of 00 μm or less, there is a problem in that the coercive force is significantly reduced.

In addition, a method has also been developed in which a thin ribbon of this alloy is created by an ultra-quenching method, and the thin ribbon is crushed and used for a resin magnet. However, in order to have sufficient coercive force, it must be finely pulverized to the order of submicrons. When such a fine powder is used, there is a problem that distortion that adversely affects magnetic properties occurs during processing of the powder, and oxidation is promoted due to an increase in surface area, making it impossible to obtain a desirable anisotropic magnet.

[Purpose of the invention]

In view of the above points, an object of the present invention is to provide a method for producing permanent magnet powder that has excellent magnetic properties even when used in resin magnets and the like.

[Disclosure of the invention]

In order to achieve the above object, the present invention is characterized in that when obtaining permanent magnet powder by pulverizing a sintered body made of a permanent magnet alloy, the sintered body fine powder obtained by the pulverization is heated. The gist of this paper is a method for producing permanent magnet powder.

This invention creates a sintered magnet made of a permanent magnet alloy having a predetermined composition. For example, this can be done in the following steps. Rare earth elements such as Nd, Dy, and Ce are
and/or one or more CO and B in a predetermined amount, and an ingot is melted using an arc melting furnace or the like. That is, an ingot having a compositional formula of R, M, and B is prepared. Here, R represents a rare earth element, and M represents Fe and/or Co among transition metal elements. And X is 8 or more and 30
and y is 2 or more and 20 or less, and 2 is the value obtained by subtracting X and y from 100. This is because if x, y, and z are outside these ranges, it is difficult to obtain a permanent magnet with high magnetic properties.

The ingot thus obtained is crushed and the powder is sintered. Thereafter, aging treatment is performed under appropriate heat treatment conditions. The obtained permanent magnet alloy sintered body is pulverized and then heated. This heat treatment can recover the decrease in coercive force caused by pulverization.

Conventionally, when a sintered body is finely pulverized to a particle size that can be used for resin magnets, it has been difficult to ensure a coercive force above a certain value. However, as a result of intensive research, the inventors discovered that the coercive force could be increased by pulverizing the sintered body and then heating it. It is preferable to adjust the particle size of the powder at this time to 10 μm or more. This is because if the powder is smaller than this, the surface area will increase significantly and oxidation will easily occur during heating, which is undesirable. On the other hand, the heating temperature is 500
It is desirable to carry out at a temperature in the range of ~1000°C. At temperatures below 500°C, no significant effect of recovering coercive force can be obtained;
This is because if the temperature exceeds 00°C, welding will occur in a part of the powder, which is not preferable.

The fine powder thus obtained is mixed with an epoxy resin or the like to create a resin magnet. However, a rubber magnet may be created by mixing this fine powder with rubber or the like.

Next, examples will be described.

(Example 1) Using an arc melting furnace etc., the composition formula is N d , DY
Fe? ? A magnetic alloy was melted to form BB, and an ingot was created. The obtained ingot was coarsely pulverized in an iron mortar, and further pulverized with a jet mill in a N2 gas stream to obtain a particle size of approximately 2 to 3 μm. This fine powder was inserted into a mold, and while applying a magnetic field of 20 kOe, it was heated at 2t/cl.
] Pressurized and molded at a pressure of I. Next, the molded body was placed in a vacuum furnace, and after the vacuum was closed to 5×10 −'torr or less, high-purity Ar gas was introduced and sintered at 1080° C. for 1 hour.

Thereafter, it was cooled to room temperature at a cooling rate of 300° C./win. Next, this sintered body was heated at 900°C for 2 hours, cooled to room temperature at a cooling rate of 60°C/h, and then aged at 650°C for 1 hour. Br at this time is 11.3k
G, iHc is 13.0koe, (BH)m
ax was 32MGOe.

After pulverizing such a sintered body, the powder was placed in a vacuum furnace, heated at 900°C for 2 hours, and then cooled to room temperature at a rate of 60°C/hr. After adjusting the particle size of the resulting powder, it was placed in a Teflon container and solidified using an epoxy resin while applying a magnetic field.

The thus-prepared resin magnet, together with the powder before heating, was measured using a DC magnetization measuring device to determine the coercive force (iHc).
) was measured. The results are shown in Table 1.

Furthermore, Table 2 shows the measurement results of the coercive force when the heating temperature was changed from 600 to 800° C. for powders having a particle size of 74 to 149 μm.

Table 1 Table 2 (Note) The particle size of the powder is 74 to 149 μm.

As shown in Table 1, if heat treatment is not performed, when the particle size becomes 49 μm or less, the coercive force becomes extremely small and it cannot be used as a resin magnet. In contrast, when heat-treated, the particles have a sufficiently high coercive force even if the particle size is 149 μl or less, and can be used in resin magnets.

On the other hand, it is clear that even if the heating conditions are changed to the temperature range shown in Table 2, a sufficiently high coercive force is maintained.

(Example 2) Using an arc furnace, the composition formula is CeN d 14F e
-, 7B8, and Example 1
A sintered magnet was created in the same manner. The magnetic properties at this time are Br of 13.3 kG and iHc of 8.7 kO.
e, and (BH)max was 41.0 MGOe. This sintered magnet was finely pulverized and heat treated in the same manner as in Example 1, and its coercive force was measured.

The results are shown in Table 3.

As in Example 1, it can be seen that even if the particle size of the powder is minute and is in Tables 3 and 4, it has a high coercive force with each heat treatment.

Note that 200μ of the powders obtained in Examples 1 and 2
Direct pressure molding was performed for those with a diameter of less than m to create resin magnets. The magnetic properties at that time are shown in Table 4.

It is clear that all of them have excellent magnetic properties as resin magnets.

It goes without saying that the method for producing permanent magnet powder according to the present invention is not limited to permanent magnets containing rare earth elements.

〔Effect of the invention〕

Since the method for producing permanent magnet powder according to the present invention has the above-described structure, even if a permanent magnet alloy is pulverized, a fine powder with high magnetic properties can be obtained, and this can be used for use in resin magnets, etc. I was able to obtain something that I was completely satisfied with.

Agent: Patent Attorney Takeshi Matsumoto
, Hanyu's MU6 1 To'fm1M 19 1 897 No. 3, Relationship with the case of the person making the amendment Patent applicant address 1048 Kadoma, Kadoma City, Osaka Name (583) Representative of Matsushita Electric Works Co., Ltd. ((JIM Emperor Sadao Ugai 4, agent name (7346) Patent attorney Takeshi Matsumoto
Hikoj゛-1. Correct the phrase "as a high-performance permanent magnet" to "as a high-performance permanent magnet."

(2) On page 3, lines 9 to 12 of the specification, the phrase "To make this alloy..." was replaced with "preparing a ribbon of this alloy, and crushing the ribbon." A method has also been developed in which the method is used to make isotropic resin magnets.However, in order to make anisotropic resin magnets, "

(3) On page 5, line 13 of the specification, the phrase ``If this is heated,'' should be corrected to ``If this is heated.''

(4) In the 20th line of page 10 of the specification, the phrase "as in the case of Example 1" is corrected to "as in the case of Example 1."

Claims (2)

[Claims] (1) A method for producing permanent magnet powder, which comprises heating the fine sintered powder obtained by the pulverization in obtaining the permanent magnet powder by pulverizing a sintered body made of a permanent magnet alloy. (2) Claims in which the permanent magnet alloy is expressed by the following formula, the fine sintered powder has a particle size of 10 μm or more, and the heating is performed in a temperature range of 500 to 1000°C A method for producing permanent magnet powder according to item 1. R_xM_yB_a Here, R is one or more rare earth elements, and M is Fe and/or Co. However, 8≦x≦30, 2≦z≦20, and y=100−x−z.