JPS6253929B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder compacting method for anisotropic permanent magnets.

In a conventional method for manufacturing an anisotropic permanent magnet, a raw material ingot is first created by melting and casting a raw material having a predetermined composition. Permanent magnets are required to have various shapes and dimensions depending on the application, so in order to obtain the desired shape and dimensions, this raw material ingot is ground into particles with a predetermined particle size using a ball mill, etc. The particles are filled into a mold and compacted by applying a magnetic field to align the magnetic anisotropy direction of each particle in a direction parallel to the magnetic field. The particles obtained by this pulverization have a random shape, as shown in FIG. 1, and there is no correlation between the particles 1 and the magnetic anisotropy direction 2 of the crystal.

When such particles 1 are compacted in a magnetic field, as shown in FIG.
The magnetic anisotropy direction 2 of the crystal is parallel to the direction of the external magnetic field 3, but as shown in Fig. 3, when pressure is applied as indicated by the arrow 5, the particles are 1 rotates or moves, and the magnetic anisotropy direction 2 of the crystal is oriented in various directions depending on the particle, and is not necessarily parallel to the direction of the external magnetic field 3. In addition, because the shape of the particles 1 is random, gaps 6 inevitably occur between the particles, which reduces the packing density after molding. This is why the magnetic performance is about 50 to 70% of the theoretical value. It had the disadvantage that it could only give you something.

Furthermore, due to the gaps 6 formed between the particles, the bonding force between the particles is reduced, the mechanical strength of the permanent magnet is reduced, and cracks and cracks are more likely to occur.

A method to solve these drawbacks is to cast the crystals using zone melting so that their magnetic anisotropy is aligned in one direction, and then cut, grind, or polish the resulting raw material ingot into the desired shape and dimensions. Possible methods include processing, or zone melting using casting in the desired shape so that the desired shape is obtained from the beginning, but the former method is
The disadvantage of this method is that the more complex the desired shape, the more difficult the post-casting processing becomes, leading to a significant increase in manufacturing costs. It becomes extremely difficult to align the anisotropy direction in one direction.
Moreover, compared to the conventional method in which a large amount of raw material is melted and cast at one time, melting and casting must be performed for the number of products, which also has the disadvantage of causing a significant increase in manufacturing costs.

The present invention eliminates such drawbacks, provides a powder compacting method that aligns the magnetic anisotropy direction of crystals in one direction, and does not create gaps between particles, and provides a permanent magnet with excellent magnetic performance and mechanical strength. The purpose is to realize the following.

In other words, in the production method of the present invention, instead of the conventional method of creating particles by pulverizing a raw material ingot,
Particles are created by cutting a raw material ingot into flat plates so that the magnetic anisotropy direction of the crystal is parallel to the longest side or the shortest side that is parallel to the external magnetic field.

The raw material ingot can be cut by a well-known cutting means such as a diamond cutter, which has been conventionally used for precision cutting of hard and brittle materials such as ore and concrete.

In addition, in the conventional crushing method, it was necessary to reduce the particle size as much as possible in order to minimize the gaps between particles, but according to the present invention,
Since there are almost no gaps between particles, it is only necessary that the gaps are as small as possible to obtain the desired shape, and the particles may be cut to the optimum size depending on the purpose.

This will be explained in detail below using examples.

Example 1 FIG. 4 is a diagram showing the state of particles 1 during magnetic field forming (hereinafter referred to as transverse magnetic field forming) in which the direction of external magnetic field 3 and the direction of pressure indicated by arrow 5 are orthogonal. Particles 1 are obtained by subjecting a raw material ingot to zone melting, as shown in FIG.
As shown in the figure, the particles were cut into flat plates so that the magnetic anisotropy direction 2 of the crystal was parallel to the direction of the longest side of the particles 1.

The size ratio of particle 1 is the magnetic anisotropy direction of the crystal 2
is taken as the length direction, and width:thickness:length=3:1:10.

When this tabular grain 1 is filled into a mold and an external magnetic field 3 is applied, the longest side of the tabular grain 1, that is, the length direction, becomes uniformly parallel to the external magnetic field 3, as shown in FIG. .

When pressure is applied in this state, the length direction remains parallel to the external magnetic field 3, but the particles whose width direction is parallel to the direction of pressure are pushed by adjacent particles and rotate. All particles are gradually aligned so that the thickness direction is parallel to the direction of pressure, and finally, as shown in Figure 7, the magnetic anisotropy direction 2 of the crystal of all particles is in the direction of the external magnetic field. The particles are parallel to each other and formed into a permanent magnet with no gaps between the particles.

As a result, the magnetic performance is improved by 1.2 to 1.5 times compared to the conventional method using random-shaped particles, and the mechanical strength is also improved by 1.2 to 1.5 times, preventing the occurrence of cracks and cracks. was completed.

Example 2 FIG. 8 is a diagram showing the state of the particles 1 during compaction in a magnetic field (hereinafter referred to as longitudinal magnetic field compaction) in which the direction of the external magnetic field 3 and the direction of pressure are parallel. Particle 1 is Example 1
In the same way as above, a raw ingot in which the magnetic anisotropy direction of the crystal is aligned in one direction is cut, and as shown in FIG. 9, the magnetic anisotropy direction 2 of the crystal is the direction of the shortest side of the particle 1. Made to be parallel.

The size ratio of particle 1 is the magnetic anisotropy direction of the crystal 2
is the length direction, width:thickness:length=1:1:0.2
And so.

When this tabular grain 1 is filled into a mold and an external magnetic field 3 is applied, the shortest side, that is, the length direction, of the tabular grain 1 becomes uniformly parallel to the external magnetic field 3, as shown in FIG. .

When pressure is applied in this state, while the length direction remains parallel to the external magnetic field 3, adjacent particles are pushed together and gradually aligned so that their entire width or length sides are in contact. As shown in FIG. 10, a permanent magnet was formed in which the magnetic anisotropy direction 2 of the crystals of all particles was parallel to the direction of the external magnetic field and there were no gaps between the particles.

In particular, in the case of conventional longitudinal magnetic field forming, pressure is applied in the direction of the magnetic anisotropy of the crystal, which has the disadvantage of easily destroying the magnetic anisotropy. Since the shortest side was in the direction of the pressure, it was difficult to break, and the same effect as in Example 1 was obtained.

As described above, according to the present invention, the raw material ingot is cut into flat plates according to the direction of the external magnetic field to create particles, and the particles are formed in a magnetic field, so that magnetic performance can be improved. With,
It is possible to provide a permanent magnet with excellent mechanical strength without gaps between particles, and it has many effects.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the shape of conventional particles. FIG. 2 is a diagram showing the state of particles before pressure is applied during conventional molding in a magnetic field. FIG. 3 is a diagram showing the state of particles when pressure is applied during conventional molding in a magnetic field. FIG. 4 is a diagram showing the state of particles during transverse magnetic field forming according to the present invention. FIG. 5 is a diagram showing the raw material ingot used in the present invention. FIG. 6 is a diagram showing tabular grains used in transverse magnetic field shaping according to the present invention. FIG. 7 is a diagram showing a permanent magnet formed by transverse magnetic field forming according to the present invention. FIG. 8 is a diagram showing the state of particles during longitudinal magnetic field molding according to the present invention.
FIG. 9 is a diagram showing tabular grains used in longitudinal magnetic field shaping according to the present invention. FIG. 10 is a diagram showing a permanent magnet formed by vertical magnetic field forming according to the present invention. DESCRIPTION OF SYMBOLS 1... Tabular grain, 2... Magnetic anisotropy direction of crystal, 3... External magnetic field, 4... Shaping punch, 5...
Arrow indicating the direction of pressure, 6... gaps between particles,
7...Raw material ingot.

Claims (1)

[Claims] 1. In a method for manufacturing anisotropic permanent magnets by powder compaction in a magnetic field, a raw material ingot in which the magnetic anisotropy direction of the crystals is aligned in one direction is cut, and the magnetic anisotropy direction of the crystals is aligned in the direction of the external magnetic field. Create tabular grains with parallel longest or shortest sides,
A method for producing an anisotropic permanent magnet, comprising filling the tabular grains into a mold and compacting them while applying an external magnetic field.