JPH04144206A - Rare earth bonded magnet - Google Patents

Abstract

PURPOSE:To improve density without deteriorating magnetic characteristics, and obtain superior magnetic characteristics, by binding magnetic powder obtained by pulverizing bulk type alloy whose basic composition is composed of specified elements, and spherical type magnetic powder having the similar composition, by using resin. CONSTITUTION:Basic composition of bulk type alloy is the following; rare earth metals (at least one kind of rare earth element containing Y), cobalt Co, to which iron Fe, copper Cu, zirconium Zr, etc., are added in the case of need, and inevitable impurities of manufacturing. Magnetic powder obtained by pulverizing said alloy and spherical type magnetic powder having the similar composition are bound by using resin. The bulk type alloy is casted alloy or sintered magnet which is heat-treated and cured in a magnetic field. The spherical magnetic powder is obtained by using a quenching solidification method such as a gas atomization method, a rotary electrode method, and a centrifugal atomization method.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to rare earth bonded magnets.

[Prior Art] Conventionally, bonded magnets combine magnetic powder with a resin, so the magnetic properties obtained are lower than those of bulk magnets such as sintered magnets due to the inclusion of non-magnetic resin. Therefore, one possible way to improve the poor magnetic properties is to increase the density, but specific examples include reducing the amount of resin and increasing the molding pressure. However, these improvement measures naturally have their limits due to the problem of frictional force between powders, and so attempts have been made to improve the density by adding liquid or solid lubricants.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, a liquid or solid lubricant that does not contribute to the magnetic properties is added to improve the density (=improve the magnetic properties), so the magnetic properties inevitably deteriorate. It has the following problems.

Therefore, the present invention is intended to solve these problems, and its purpose is to provide a rare earth bonded magnet with improved density and high magnetic properties without impairing the magnetic properties.

[Means for Solving the Problems] The rare earth bonded magnet of the present invention has a basic composition of rare earth metals,
A magnetic powder made by pulverizing a bulk alloy made of cobalt and, if necessary, iron, copper, zirconium, etc. and impurities unavoidable during manufacturing, is bonded with a spherical magnetic powder having a similar composition using a resin. It is characterized by

Further, the bulk alloy is a cast alloy or a sintered magnet that has been heat-treated and magnetically hardened.

Further, the spherical magnetic powder is characterized in that it is obtained using a rapid solidification method such as a gas atomization method, a two-rotation electrode method, or a centrifugal atomization method.

[Function] According to the above configuration of the present invention, magnetic powder obtained by pulverizing a bulk magnet and spherical magnetic powder having the same composition are bonded with resin, thereby achieving the combination effect of large particles and small particles and the spherical shape. High density can be achieved by the powder colloid effect, and because no non-magnetic material is added, rare earth bonded magnets with high magnetic properties can be obtained.

In other words, the shape of the magnetic powder obtained by crushing the bulk alloy is
The result is an irregular shape with many irregularities on the surface. Therefore, when the amount of resin is reduced or the molding pressure is increased in order to improve the density in order to improve performance, these powders come into contact with each other. However, since the frictional force between them is large and it is difficult for them to slide against each other, it is difficult to increase the filling rate and increase the density.

One of the effects of the present invention is the combination effect of large particles and small particles, which is achieved by combining 200cc of soybean and 2.
This can be seen from the fact that even if you mix 00cc of rice, it will not become 400cc. In other words, since small spherical powders are inserted between large irregularly shaped powders, they can be packed more densely than when each powder is packed alone.

In addition, the rolling effect of spherical particles is caused by small spherical powders getting stuck between powders that have a large frictional force due to irregular shapes and unevenness, and by rolling when small spherical powders slide between irregularly shaped powders. Significantly reduces frictional force,
High filling, that is, high density can be achieved.

Incidentally, as a rare earth magnet whose basic composition is a rare earth metal and cobalt, Sm-Co system is known, but rare earth metals include Sm, Y, La, Ce, P.
r.

Any rare earth metal group such as Nd or Mitsushi metal may be used. That is, examples of rare earth metals include Y and La.

Ce, Pr, Nd, Pm, Sm, Eu, G
d, Tb, Dy, Ho, Er, Tm.

It may be one or more of the rare earth elements Yb and Lu. Furthermore, the atomic ratio of Sm and Co is 1:
5, SmCos, or a part of Co replaced with a transition metal group other than Co such as Fe or Cu, for example, the atomic ratio of a rare earth metal group such as Sm and a transition metal group consisting of Co, Fe, Cu and Zr. Sm2(Co, where 2=17
Fe, Cu.

Zr)
It is not limited to a specific composition system.

[Examples] Hereinafter, the present invention will be described in detail based on Examples.

(Example-1) In both weight ratios, S m 24.7%, Fe22.
9%.

It was melted and cast in an argon atmosphere using a high frequency melting furnace to have a composition of 5.3% Cu, 1.9% Zr, and the balance Co. The obtained ingot was heated at 1160℃ for 24 hours.
After time solution treatment and holding at 800°C for 4 hours,
Continuous cooling aging was performed at a cooling rate of 0.5°C/min to 400°C. Then, the powder was ground to a particle size of 10 to 30 μm to obtain magnetic powder.

Next, using the same ingot, spherical fine powder, most of which had a diameter of 1 to 30 μm, was obtained by argon gas atomization and subjected to the same heat treatment.

Mix the above two types of powder in a ratio of 98:2,
Mixed and kneaded with epoxy resin of 17kO by weight%
The magnet was oriented in a magnetic field of e, pressed at 50 kg/mm2, and cured to produce a bonded magnet of 8 x 8 x 12 mm. This is referred to as present invention 1.

Further, as Comparative Example 1, a bonded magnet made of only cast alloy powder was created, and as Comparative Example 2, a bonded magnet was created in which 0.5% by weight of oleic acid was added to Comparative Example 1 as a lubricant.

Table 1 shows the magnetic properties of each bonded magnet.

As can be seen from Table 1, the bonded magnet of Comparative Example 1 has a low density, resulting in a low residual magnetic flux density (Br) and a low maximum energy product ((BH)max). Further, although the bonded magnet of Comparative Example 2 has a higher density, the improvement in Br is slight because it contains a lubricant (which does not contribute to the magnetic properties). On the other hand, the bonded magnet of Invention 1 has a higher density without much change in coercive force (iHc), and B r , (BH)ma
x has also been greatly improved.

In other words, the present invention can greatly improve magnetic properties.

(Example-2) Both have a weight ratio of 25.5% Sm and 15% Fe.

The composition was melted in an argon atmosphere using a high-frequency melting furnace to obtain a composition of 8% Cu, 1.5% Zr, and the balance Co.
The ingot obtained by casting was crushed to a size of 3 to 5 μm, and compression molded at a pressure of 15 kOe/mm 2 in a magnetic field of 10 kOe. This green body is 1150-1250
℃ for 1 hour, solution treated at 1100-1220℃ for 1 hour, aged at 850℃ for 1 hour, and heated to 400℃ at 1℃.
Continuous cooling in minutes. The sintered magnet obtained here was pulverized to a size of mostly 10 to 30 μm to obtain magnetic powder.

Using this magnetic powder, 8% of gas atomized powder was mixed as in Example 1 (Invention 2), sintered magnet powder was used alone (Comparative Example 3), and Comparative Example 3
Three types of bonded magnets were prepared, including one in which 0.5% by weight of stearic acid was added as a lubricant (Comparative Example 4). The results are shown in Table 2.

As is clear from Table 2, compared to Comparative Examples 3 and 4, Invention 2 has high magnetic properties similar to Example-1.

In other words, the present invention is effective regardless of whether the starting material is a cast alloy magnetically hardened by heat treatment or a sintered magnet, and the effect remains the same even if other starting materials are used. Therefore, the invention is not limited to starting materials.

Furthermore, the compositions of the two types of magnetic powders do not necessarily have to be the same.

(Example 3) A spherical powder was produced from the alloy of Example 1 using a rotating electrode method and a centrifugal atomization method in the same manner as the gas atomization method. Using these spherical powders, bonded magnets were created in the same manner as in Examples 1 and 2. Specifically, a powder obtained by pulverizing the cast alloy of Example 1 and a spherical powder prepared by a rotating electrode method and a centrifugal atomization method were mixed at a ratio of 96:4, respectively. -2 powder obtained by crushing the sintered magnet and spherical powder produced by the rotating electrode method.92
Invention 5 is a mixture of 8 and 8. Table 3 shows the magnetic properties of bonded magnets made from each powder.

As is clear from Table 3, the present invention does not depend on the method for producing spherical powder, and any method may be used as long as spherical powder can be obtained. It also does not depend on the amount of spherical powder.

[Effects of the Invention] As described above, according to the present invention, the basic composition is a rare earth metal, cobalt, and iron as necessary.

By combining magnetic powder obtained by pulverizing a bulk alloy containing copper, zirconium, etc. and impurities unavoidable in manufacturing with a spherical magnetic powder having a similar composition using a resin, Since the density of bonded magnets can be increased, bonded magnets with high magnetic properties can be obtained, and furthermore, by using this, high torque and small motors can be realized, which has great effects in terms of applications. It is something.

that's all Applicant: Seiko Epson Corporation

Claims (3)

[Claims] (1) The basic composition is rare earth metal (at least one rare earth element including Y; hereinafter abbreviated as R), cobalt (
Magnetic powder that has the same composition as the magnetic powder obtained by pulverizing a bulk alloy consisting of Co) and, if necessary, iron (Fe), copper (Cu), zirconium (Zr), etc., and impurities that are unavoidable in manufacturing. A rare earth bonded magnet characterized by bonding spherical magnetic powder with resin. (2) The rare earth bonded magnet according to claim 1, wherein the bulk alloy is a cast alloy or a sintered magnet that has been magnetically hardened by heat treatment. (3) The rare earth bonded magnet according to claim 1, wherein the spherical magnetic powder is obtained using a rapid solidification method such as a gas atomization method, a rotating electrode method, or a centrifugal atomization method.