JPH0371602A - Method for producing rare earth-iron-boron alloy powder for sintered magnets - Google Patents

Abstract

PURPOSE:To contrive improvement in mechanical strength of compression powder mold by a method wherein, after an ingot or the coarsely crushed substance of the ingot is heated up to 600 to 1100 deg.C in a non-oxidizing atmosphere, it is pulverized into fine powder of 1 to 10mum in average diameter. CONSTITUTION:The prescribed quantity of electrolytic iron, metal Nd, metal Dy and boron is melted by high-frequency heating in vacuum, and founded using a water-cooled mold. The lump glanular substance or powder obtained by glanulating the above-mentioned ingot is heated up to 600 to 1100 deg.C in a non-oxidizing atmosphere. The lattice defect of the heated substance is sharply reduced by the above-mentioned heating, and the compression moldability can be improved. The alloy powder is liable to be oxidized in the average grain diameter of 1mum or less, and sufficient coercive force is not obtained when the average grain diameter exceeds 10mum. Therefore, the fine powder of 1 to 10mum in average grain diameter is obtained by pulverizing the material after heating. As a result, the mechanical strength of the compression powder mold can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to rare earth-iron (Fe) suitable for use in sintered magnets.
-Regarding an improvement in a method for producing boron (B) alloy powder.

[Conventional technology]

Rare earth-Re magnet materials represented by neodymium (Nd)-Fe-B alloy are samarium (Sm)-cobalt (
It is attracting attention because of its high magnetic properties and low raw material cost compared to Co)-based magnet materials. This rare earth -Fe-
The rare earth-Fe-B alloy powder used to manufacture B-based magnets is manufactured by a melting method.

The melting method uses pure iron, Fe-B alloy,
After melting and casting rare earth metals, the resulting ingot is coarsely and finely crushed.

Seedling soil 'lf4-Fe produced by such dissolution method
The -B alloy powder is then pressure-molded in a magnetic field to form a green compact, and the green compact is further sintered in a vacuum to produce a sintered magnet.

[Problem to be solved by the invention]

However, the above green compact does not have sufficient mechanical strength. This is relatively not a problem if the shape of the sintered magnet product to be manufactured is large and simple, but if the shape is thin or complex, the compacted powder or sintered This can cause cracks and chips to easily occur.

The purpose of the present invention is to solve such problems and to utilize the above melting method to produce a rare earth-F3-B alloy that has excellent mechanical strength of a green compact and is suitable for use as a raw material for sintered magnets. An object of the present invention is to provide a method for producing powder.

[Means and effects for solving the problems] The present invention achieves the above objects of the present invention by providing an ingot obtained by the above melting method or a lump obtained by coarsely crushing the ingot, 600-1100 for granules or powder in a non-oxidizing atmosphere
A method for producing rare earth-iron-boron alloy powder for sintered magnets, which comprises heating at °C and then pulverizing into a fine powder with an average particle size of 1 to 10 μm, with or without coarse crushing. .

By heating at 600 to 1100°C, the mechanical strength of the green compact obtained in the subsequent process is improved. This is presumed to be because the heating described above significantly reduces lattice defects in the object to be heated and improves its compactability. Heating temperature is 600
If the temperature is less than 1100°C, this effect will not be sufficiently exhibited, and if the temperature exceeds 1100°C, a phenomenon of melting or sintering will occur in a part of the heated object. Heating time is not particularly limited.

The object to be heated in this heating may be an ingot as it is,
The ingot may be crushed into lumps, granules, powder, etc. The object to be heated after heating is coarsely crushed or finely crushed without being coarsely crushed to form a fine powder. The average particle size of the powder after pulverization is required to be 1-10 μm, preferably 1-8 μm. If the average particle size is less than 1 μm, the alloy powder will be easily oxidized, and if it exceeds 10 μm, it will be difficult to obtain a sufficient coercive force.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

EXAMPLES AND COMPARATIVE EXAMPLES Predetermined amounts of electrolytic iron, metal Nd, metal oy, and boron (all purity 99.9% by weight) were weighed, high-frequency melted in a vacuum, and cast into a water-cooled mold. The obtained ingot was coarsely crushed with a hammer and a show crusher to give approximately 50 g of lumps, 12 to 5 meshes of granules, and 35 to 12 meshes each.
It was classified into powders with a mesh size of 35 meshes or less. These materials were heated under the conditions shown in Table 1, and then cooled to room temperature. The obtained heated material was pulverized using a vibration mill or a jet mill. Table 1 shows the average particle size (Fisher sieving method) and composition of this powder.

Next, this fine powder was press-molded, and the bending strength of the compact was measured. That is, the pressure molding was performed by moistening approximately 2.2 g of fine powder with ethanol and then performing 4. The test was carried out under a load of OOO kgf to obtain a compact having a length of 15 cm, a width of 6 cm, and a thickness of about 411 cm. In the bending test, the green compact was placed on a steel support plate with an interval of 11 m1 so as to be in contact with the surface with the largest area, and a load was applied from above the center of the green compact. The bending strength was determined from the breaking load of the green compact using the following formula. The results obtained are shown in Table 1.

Bending strength = 2.75 (breaking load)/(thickness) 2 Conventional Example The test was conducted in the same manner as in the example except that heating was not performed. The results obtained are shown in Table 1.

〔Effect of the invention〕

According to the present invention, it is possible to produce rare earth-Fe-B-based magnet powder that has excellent mechanical strength as a green compact and is suitable for use as a raw material for sintered magnets.

Claims (1)

[Claims] 1. The ingot or the lumps, granules, or powder obtained by coarsely crushing the ingot are heated to 600 to 1100 in a non-oxidizing atmosphere.
A method for producing a rare earth-iron-boron alloy powder for a sintered magnet, which comprises heating at a temperature of 0.degree.