JPH0663004B2 - Rare earth alloy crushing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for efficiently pulverizing rare earth alloys having phases having different hardnesses, and particularly to R-Fe-B-based calcination produced by powder metallurgy. The present invention relates to a crushing method during a manufacturing process of a magnet (R is one or two rare earth elements including Y).

(Prior Art and Problems) An R-Fe-B system sintered magnet manufactured by a powder metallurgy method including a crushing process, a magnetic field molding process, and a sintering process has been attracting attention as a high-performance magnet (Japanese Patent Laid-Open Publication No. Sho. 49-46008). The crushing in the manufacturing process of the magnet is divided into a crushing process of crushing an alloy ingot to several tens of μm and a fine crushing process of crushed coarse powder to several μm. Among them, there are various methods for the fine pulverization process, but a jet mill, a ball mill or the like is usually used.

The jet mill is a crushing method in which particles are introduced into a jet stream and crushed by mutual collision of particles, and there is no moving part utilizing fluid energy, and continuous crushing is possible.

A ball mill puts balls, rods, etc. as a grinding medium in a grinding chamber and grinds by dropping or rolling the medium, and is generally used in a batch system.

No matter which method is used to crush the R-Fe-B magnet alloy, R-Fe-B
The system magnet alloy R ₂ Fe ₁₄ other than B-phase R ₂ Fe ₁₄ less hardness than B phase, since the ground hard R- rich phase is present, a few μm
The crushability of crushing depends on the crushability of the R-rich phase, and as a result, the R-Fe-B alloy is harder to crush than the Sm-Co alloy, which is the same high-performance magnet alloy. Become. For example, when milling with a jet mill, the feed rate of powder to mill to about 3 μm, that is, the amount of powder that can be milled per unit time is
It is reduced to 1/3 to 1/2 that of Sm-Co alloys. When grinding with a ball mill, the time for grinding to about 3 μm is R-Fe
-B-based alloy is 1.3 to 2 times longer than Sm-Co alloy.

In order to solve this problem, a method has been proposed to improve the pulverizability by making the alloy absorb hydrogen in a pressurized state in a hydrogen atmosphere before the pulverizing step to embrittle the alloy. However, since the amount of hydrogen contained in the alloy is large and the amount of hydrogen contained in the alloy is large, problems such as ignition of powder in the magnetic field forming step after the pulverizing step and large generation of hydrogen in the sintering step remain.

(Means for Solving Problems) In order to solve such a problem, the inventors of the present invention have been keenly aware of a method capable of improving pulverizability without performing a pretreatment such as embrittlement of an alloy before the pulverization step. After further study, we noticed that the new surface of R-Fe-B magnet alloy was extremely active immediately after dry pulverization in an inert atmosphere, and H ₂ , O ₂ , H ₂ O It was found that when at least one kind of NH ₃ gas was adsorbed on this new surface, the alloy containing the R-rich phase, which is difficult to pulverize, became brittle due to hydrogenation, oxidation, nitriding, etc. The present invention has been made based on these findings, and causes the alloy to become brittle at the same time as pulverization,
A pulverization method capable of increasing the pulverizability of an alloy containing a phase that is difficult to pulverize, represented by the formula R-Fe-B (wherein R is one or more rare earth elements including Y). After coarsely crushing the rare earth alloy, 0.01 to 10% by volume of H ₂ , O ₂ , H ₂ O and N with inert gas
The gist is a method for pulverizing a rare earth alloy, which comprises pulverizing with a pulverizer in a mixed gas atmosphere with at least one selected from H ₃ .

The method of the present invention will be described in detail below. In the case of dry pulverizing an R-Fe-B alloy in an inert gas atmosphere such as argon, helium, or N ₂ , the alloy is first coarsely pulverized to about 20 to 100 μm. The fresh surface immediately after crushing with H ₂ , O ₂ , H ₂ O, NH ₃
Finely pulverizing with a fine pulverizer to about 2 to 5 .mu.m in an atmosphere gas added with.

The effect of H ₂ , O ₂ , H ₂ and NH _{3 on} the pulverizability appears to be contained in the pulverization atmosphere gas at a volume ratio of 0.01% or more. However
If the amount exceeds 10%, not only does the pulverizability not increase so much, but in the case of H ₂ and NH ₃ , the risk of operation increases, so 5% or less is preferable. For example, if H ₂ is increased to hydrogenate the inside of the powder, the powder easily ignites in the magnetic field molding process after the crushing process, and a large amount of hydrogen is generated in the sintering process. Occurs. In the case of O ₂ and H ₂ O, deterioration of magnet characteristics due to oxidation becomes a problem.

Further, when oxynitriding the inside of the powder, problems such as deterioration of magnet characteristics remain. Of H ₂ 0.01% to 10% by volume, O _2, H ₂
O, hydrogenation is in the range of the addition amount of NH _3, oxidation, although only the embrittled surface vicinity of the powder by nitriding, the grindability only embrittlement surface for grinding to proceed by a crack generated in the surface 1.3 3 times better. Moreover, since the reaction does not proceed to the inside of the powder, it is possible to suppress adverse effects on the process and magnet characteristics. N ₂ alone has little effect, but nitriding slightly improves the pulverizability, so that a synergistic effect is obtained when used as a pulverization atmosphere.

A jet mill, a ball mill or the like can be used as the fine pulverizer.

The present invention will be described below with reference to examples.

(Example 1) The raw materials were adjusted so that Nd was 33.0 wt%, Fe was 65.7 wt%, and B was 1.3 wt%, and they were melted by high frequency heating in an argon atmosphere to obtain an ingot. Next, the ingot of the above composition is roughly crushed in a nitrogen atmosphere to 40 mesh through or less, and then He
Was pulverized to 3 μm by a jet mill in various atmospheres containing H ₂ and NH ₃ . These fine powders were pressure-molded in a magnetic field of 10 kOe at a pressure of ² ton / cm ² , then sintered at 1100 ° C for 1 hour in Ar atmosphere, and further at 600 ° C in Ar atmosphere.
Heat treatment was performed for 2 hours to produce a permanent magnet. Table 1 shows the jet mill crushing atmosphere, the feed rate of the coarse powder, and the magnetic characteristics at that time. No. 1 and 7 are comparative examples and H ₂
Alternatively, the results obtained by pulverizing only NH ₃ are shown.

(Example 2) The coarse powder obtained in the same manner as in Example 1 was finely pulverized to 3 µm by a dry ball mill in various atmospheres containing Ar containing O ₂ and H ₂ O. The crushed amount was 100 g. Using these fine powders, a permanent magnet was produced under the same conditions as in Example 1. Table 2 shows the crushing atmosphere of the ball mill, the crushing time and the magnetic properties. No.2-1, 2
-6 is a comparative example.

(Example 3) The coarse powder obtained in the same manner as in Example 1 was finely pulverized to 3 µm by a jet mill in various atmospheres containing N _2, or argon and containing H ₂ , O ₂ , and NH ₃ . Table 3 shows the jet mill pulverizing atmosphere, the coarse powder supply rate, and the magnetic properties at that time. Nos. 3-1 and 3-6 are comparative examples.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takehisa Minowa 2-15-5 Kitafu, Takefu City, Fukui Prefecture Shinetsu Kagaku Kogyo Co., Ltd. Magnetic Materials Research Laboratory (56) Reference JP-A-60-119701 (JP, A) )

Claims (1)

[Claims] 1. A rare earth alloy represented by the formula R-Fe-B (wherein R represents one or more rare earth elements including Y) is roughly crushed and then mixed with an inert gas and its volume ratio. A method for pulverizing a rare earth alloy, which comprises pulverizing with a fine pulverizer in a mixed gas atmosphere with at least one selected from 0.01 to 10% of H ₂ , O ₂ , H ₂ O and NH ₃ .