JPS58180005A - Manufacture of rare-earth intermetallic compound magnet - Google Patents

Abstract

PURPOSE:To obtain the rare-earth intermetallic powder magnet, thermal stability thereof is excellent and shape density thereof is high and which has high magnetic flux density, by utilizing only coarse powder, grain size thereof is adjusted at specific value. CONSTITUTION:Ingot acquired by melting an alloy, which contains rare-earth metals and consists of 25.7% Sm, 13.7% Fe, 7.6% Cu, 2.6% Hf, and the remainder Co in wt%, through high-frequency dissolution is homogenized in an argon atmosphere, water-hardened and age-treated in the argon atmosphere. The material is coarse-ground and fine-ground by using a jaw crusher and a disk mill, a jet mill, etc. after aging, coarse powder coarse-ground is classified by using a screen of 635 meshes, and the coarse powder of +635 meshes is obtained. Coarse powder and fins of the grain size of 20-500 micron of rare-earth intermetallic compound powder acquired in this manner are each kneaded with an epoxy group binder, and pressed in a magnetic field of approximately 8,000Oe.

Description

Detailed Description of the Invention The present invention provides rare earth metals R (Sm, Y, La, Ce, Nd,
Rn, missing metal, etc.) and one or more other elements (
The present invention relates to a method for manufacturing a matrix magnet comprising a precipitation hardening rare earth intermetallic compound powder magnet (CosNt, Fe, Cu, Mn, Cr, etc.) and a suitable binder.

Generally, sintering methods, casting methods, powder methods, and the like are known as methods for producing rare earth magnets. Although the sintering method provides higher magnetic properties than the powder method, it has the disadvantage that it is hard and brittle and cannot be subjected to complex processing.

The casting method also has the same drawbacks as the sintering method in that its workability is inferior to the powder method, and complex processing cannot be performed. In recent years, in order to improve the shortcomings of the sintering and casting methods, powder obtained by mechanically crushing lumps of rare earth metal compounds produced by metallurgical methods, etc., is mixed with organic resins, etc. Matrix magnets, which are formed from molded or pulverized powder and then impregnated with organic resin, are attracting industrial attention.However, conventional powder magnets are mainly manufactured from fine powder with a particle size of 20μ or less. For,
One of the disadvantages is that it has significantly lower thermal stability than sintered magnets, and therefore suffers from large changes over time and low reliability. Another drawback is that when molding fine powder of 20 μm or less, the brush lines between the powders during molding are large and the resistance during molding is large, making it difficult to increase the density of the molded product.

The present invention aims to improve the above-mentioned drawbacks and provide a rare earth intermetallic powder magnet that has excellent thermal stability, high compact density (filling rate), and high flux density. .

It is generally accepted that as the particle size of rare earth intermetallic compound powder increases, the moldability decreases and the compact density (filling rate) decreases. However, when the same volume is filled with the same amount of powder and molded, K.

The smaller the particle size, the larger the surface area. Therefore, the frictional resistance due to contact between powders during molding increases as the powder particle size becomes smaller, so that the compact density (filling rate) becomes more difficult to knead when the powder particle size is small. Therefore, in order to increase the density of the compact and the potential of the magnetic flux density obtained, it is important to use powder with a particle size as large as possible. In addition, from the perspective of thermal stability, rare earth intermetallic compound fine powder itself is very easily oxidized and unstable, and even if it is left at room temperature for a long time in the air, its magnetic properties will gradually change. deteriorates. This deterioration progresses at an accelerated rate as the ambient temperature rises above room temperature, and is particularly noticeable at temperatures above 60°C. Therefore, matrix magnets manufactured by molding such thermally unstable reef powder cannot avoid aging due to oxidation, etc., even if an appropriate binder is selected and protected, and compared to sintered magnets, etc. Because of its extremely poor thermal stability, its applications are naturally limited. Therefore, in order to obtain a thermally stable matrix magnet, it is desirable to use powder with a large particle size.

Based on these two considerations, the present inventors conducted a detailed study on the relationship between the particle size of rare earth intermetallic compounds, compact density, thermal stability, magnetic properties, etc., and found that the particle size was 20 to 500 μm.
It has been discovered that if a rare earth intermetallic compound matrix magnet is manufactured using only coarse powder adjusted to Ta. Note that the upper limit of the particle size is 5oOμ, which means that if the particle size exceeds 500μ, the
As the degree of orientation decreases as a result of gloriage deterioration,
This is because a decrease in magnetic flux density is unavoidable, and the lower limit of 20
μ takes into consideration thermal stability and compact density. Furthermore, the reason for using precipitation-hardened rare earth magnets is that, for example, powders of Sm-Co and rare earth intermetallic compounds that have a nucleation type coercive force mechanism do not oxidize the surface even if the particle size is increased. This is because magnetization reversal easily occurs, so the effect on thermal stability is not very large. Examples of the present invention will be described in detail below.

Example 1 Weight* Sm25.7%, Fe1! L7%, C
An ingot obtained by melting an alloy consisting of 7.6% U, 24% Hf, and the balance CO by high-frequency hydrolysis,
After homogenization treatment and water quenching at 820°C for 2 hours in an argon atmosphere, aging treatment was performed at 820°C for 2 hours in an argon atmosphere. After aging, coarse pulverization and fine pulverization were performed using a dike crusher, a disk mill, a jet mill, and the like.

Coarse powder coarsely ground with a disc mill is made into 635 pieces (
The mixture was classified using a 20 μm sieve to obtain a coarse powder of +665 mesh size. The coarse powder thus obtained and the fine powder (average particle diameter of about 4 μm) obtained by jet mill pulverization were each kneaded with an epoxy binder and pressed in an i-field of about 80,000 e. After measuring the magnetic properties after press molding with a B-H) laser, set it in a thermostat set at 150°C and hold it in air for 2000 hours, then measure the magnetic properties again with a B-H) laser. did.

The results are shown in Table 1 and FIG.

As is clear from Table 1, when coarse powder of 20μ or more is used, the density of the compact after molding is higher than when fine powder is used, and the saturation magnetic flux density and residual magnetic flux density are higher and better. Magnetic properties are obtained, and thermal instability is also greatly improved.

Example 2 An ingot having the same composition as Example 1 was subjected to aging treatment, and the obtained ingot was coarsely ground using a disk mill.

This coarse powder is 665 mesh, 325 mesh, 150
It was classified using six types of sieves: mesh, 100 mesh, 80 mesh, and 32 mesh. Each of the classified powders was kneaded with an epoxy binder and molded in the same manner as in Example 1, and the density and magnetic properties of the molded product after molding were measured. The results are shown in Table 2 and FIG.

It can be seen from Table 2 and FIG. 2 that as the number diameter increases, the density of the compact increases. However, the particle size was 500μ (
When the mesh size exceeds 32 mesh, the density of the compact decreases to 4 due to the agro-T resin in one particle, even though it is high.
On the contrary, the values of $ and 4πIr decrease.

Example 6 Example 21 The death pieces A1 to 6 in Table 2 were
After saturation magnetization in a pulsed magnetic field of 000e and measuring open flux, magnetization was carried out for 10 minutes in a constant temperature bath set at 100℃.
After being left in the air for 00 hours, it was again saturated and magnetized with a 500,000 e pulse magnetic field, and the open flux was measured. Table 3 shows the rate of decrease in open flux at that time, that is, the irreversible demagnetization rate.

Table 3 From Table 6, it can be seen that when the particle size becomes 20 μm or less, the thermal stability deteriorates significantly.

Reference Example 1 An ingot obtained by stacking an alloy of weight * Sm 55% and balance cobalt by arc melting was aged at 1000°C for 1 hour, and then placed in a disk building. Half of the mixture was classified using a 525 mesh sieve to obtain +325 mesh coarse powder. The resulting coarse powder and fine powder were each kneaded with an epoxy binder, then molded in a magnetic field, aged in air at 100° C. for 1000 hours in the same manner as in Example 5, and then their irreversible demagnetization rates were measured. The irreversible demagnetization rate when fine powder is used is 22 degrees, and when coarse powder is used it is about 16 degrees, so even if coarse powder is used, irreversible demagnetization of 10 degrees or more is inevitable and a remarkable effect can be expected. do not have.

As is clear from the examples above, in the production of matrix magnets using precipitation hardening rare earth intermetallic compound magnet powder as a raw material, by adjusting the powder particle size to 44 to 500μ, a high magnetic flux density and good thermal stability can be achieved. It is something that can agglomerate magnets. Note that in this example, Sm-Fe-Co
Although the -Cu-Hf system has been described as an example [9')fi, the present invention can be widely applied to precipitation-hardened heavy rare earth intermetallic compound matrix magnets, and is limited to the 8m-Fe-Co-Cu-Hf system. It's not a thing.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the density of a compact and magnetic properties when the mixing ratio of fine powder and coarse powder was changed in stages in Example 1, and Figure 2 is a diagram showing the relationship between the density of a compact and magnetic properties when the particle size of coarse powder was varied. FIG. 3 is a diagram showing the relationship between density and magnetic properties. 72 rf2J

Claims (1)

[Claims] In a method for manufacturing a powder magnet using a precipitation hardening intermetallic compound magnet consisting of one or more rare earth metals R and at least one other element, the particle size of the rare earth intermetallic compound powder is 20 to 500 microns. A method for producing a rare earth intermetallic compound magnet, which adjusts the % mold to % mold.