Method of manufacturing rare-earth magnet powder, and method of manufacturing rare-earth bond magnet

Abstract

A method of manufacturing rare-earth magnet powder having excellent magnetic properties, and a method of manufacturing a rare-earth bond magnet are provided. A nitriding step is performed, in which when nitrided rare-earth magnet powder is produced, rare-earth-element / transition metal-based alloy powder is irradiated with a microwave at an atmosphere containing nitrogen atoms, so that the nitrogen atoms are allowed to enter into a crystal lattice.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a method of manufacturing rare-earth magnet powder, and a method of manufacturing a rare-earth bond magnet.[0003]2. Description of the Related Art[0004]Recently, much attention has been paid on a rare-earth magnet as a magnet having excellent magnetic properties. Among various magnet materials for the rare-earth magnet, a magnet produced by nitriding SmFe alloy or the like (hereinafter, called nitride compound magnet) is particularly focused with attention as a magnet material having high Curie point and excellent magnetic anisotropy.[0005]Method of manufacturing a nitride compound magnet having a rare earth element as a main component typically has steps of alloy melting, crushing, nitriding, press forming, sintering, machining, magnetization and the like. Typically, in nitriding, alloy powder is subjected to heating under a gas atmosphere of N2, NH3 or the like, or a mixed gas atmosphe...

AI Technical Summary

Benefits of technology

[0023]According to the first aspect of the invention, the rare-earth-element / transition metal-based alloy powder is irradiated with the microwave, thereby self-heating of the alloy powder itself, rapid heating, and selective heating can be performed. Therefore, processing time taken for nitriding can be reduced. Moreover, the powder can be uniformly nitrided even at the inside thereof, so that rare-earth magnet powder having high magnetic properties can be obtained.

[0025]According to the third and fourth aspects of the invention, since the microwave irradiated in the nitriding step is in the frequency of 1 GHz to 30 GHz, a phenomenon that solid-phase diffusion preferentially proceeds rather than nitriding can be suppressed, and the powder can be uniformly nitrided even at the inside thereof.

[0026]According to the fifth aspect of the invention, since grain diameter of the alloy powder as a nitriding object is 2 to 90 μm, oxidation and excessive nitriding of the alloy powder can be suppressed, and the alloy powder can be uniformly nitrided.

[0027]According to the sixth aspect of the invention, since atmosphere in the nitriding step is in a pressure of is 0.1 to 5 MPa, the alloy powder can be uniformly nitrided, and formation of an amorphous state in alloy due to excessive nitriding caused by excessive pressure can be prevented.

[0028]According to the seventh aspect of the invention, since microwave irradiation is performed while the alloy powder is heated in the nitriding step, nitriding of the alloy powder can be more efficiently accelerated.

[0029]According to the eighth aspect of the invention, since a rare-earth bond magnet is produced by using the rare-earth magnet powder subjected to nitriding, and a resin binder or a metal binder, a bond magnet having excellent magnetic properties can be obtained.

Problems solved by technology

However, in a method of performing heating at high pressure as the method described in JP-A-5-109518 or JP-A-5-135978, there is a problem that nitriding is inadequate, so that a region being not nitrided is formed in a rare-earth-element / transition metal-based magnet material, consequently the magnetic material is nonuniformly nitrided.

As a result, nitriding easily proceeds only in a particular portion of the rare-earth-element / transition metal-based magnet material, resulting in nonuniform nitriding.

Moreover, when hydrogen is remained in a magnet, the magnet becomes gradually significantly brittle in a long-term use condition, which is not preferable.

However, in this case, processing time is increased and thus production efficiency is reduced, in addition, cost is extremely increased.

Moreover, even if the nitrogen gas is substituted or evacuated, oxygen is hard to be perfectly removed from the inside of the alloy powder.

In this way, each of the methods has various problems, and each value of magnetic properties of the rare-earth-element / transition metal-based magnet nitrided by each method is still considerably low compared with a theoretical value at present.

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