JPH05217721A - Manufacture of rare earth-transition metal magnet - Google Patents

Abstract

PURPOSE:To perform pulverization more simply and also low in degree of oxidation by finely pulverizing low fusing point FE-TM alloy and RE-TM-B alloy under the mixture of the RE2TM14B1-phase powder. CONSTITUTION:If the fine pulverization of RE-TM alloy, which is abundant in ductility and is hard to pulverize and besides which is lower in fusing point than RE2TM14B1 phase and is large in RE/TM ratio, or RE-TM-B alloy is performed under the existence of RE2TM14B1, the harder RE2TM14B1 phase works as an assistant for fine pulverization, so the pulverization becomes easy. Moreover, average concentration of RE element falls, and the activity of powder at large drops, so oxidizing property is weakened, consequently the handling of fine pulverization becomes easy, and also the concentration of oxygen at the time of being made a magnet is reduced, so the property of a product, especially, the coercive force can be improved. In a word, not only the pulverization efficiency of the RE-TM alloy or RE-TM-B alloy higher in RE concentration than RE2TM14B1 can be elevated, but also the danger of ignition falls, so the handling becomes easy, and the concentration of oxygen of a magnet can be maintained low, therefore the magnetic property can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rare earth-transition metal magnet, which is excellent not only in magnetic characteristics but also in corrosion resistance and temperature characteristics.

[0002]

RE-Fe- was developed as a high-performance magnet material.
Demand for B type magnets (for example, Japanese Patent Laid-Open No. 61-34242) has been rapidly increasing in recent years, centering on motor materials thereof, as OA / FA equipment has become smaller.

However, RE-Fe-B magnets are light rare earth elements such as Nd, which have extremely high activity as components, and easily rust.
Since it contains a large amount of Fe, it has poor corrosion resistance, and as a result, its magnetic properties deteriorate and its reliability as an industrial material is lacking.

Therefore, in order to improve the corrosion resistance, for example, a sintered magnet is subjected to surface plating (JP-A-63-77103), coating treatment (JP-A-60-63901), etc. It cannot be said that the anticorrosion treatment is effective for a long period of time, and the cost increases due to such treatment, and further, there is a problem that the magnetic flux is lost due to the protective film.

As a solution to the above problem, the applicant company previously developed a rare earth-transition metal-boron-based magnet alloy in which Fe in the RE-Fe-B based magnet was replaced with Co and Ni to a high concentration. However, it was disclosed in Japanese Patent Laid-Open No. 2-4939. Since this magnet has excellent corrosion resistance and the Curie point is increased, the reliability as a material is greatly improved.

Further, as a result of further research based on the metallographical study of the magnet, the inventors have found that RE ₂ (which is the main phase of the magnet and has a high saturation magnetic flux density and magnetic anisotropy). Fe,
Co, Ni) ₁₄ B _1- phase powder and RE-T with a lower melting point than the main phase
A so-called "powder two-phase mixing method" in which M phase or RE-TM-B intermetallic compound powder is mixed as a raw material and liquid phase sintering is performed to obtain a permanent magnet having further improved corrosion resistance and magnetic properties. It has been found that it can be manufactured (JP-A-3-250607).

In the powder two-phase mixing method described above, the RE-TM alloy and / or RE-TM-B alloy having a melting point lower than that of the main phase functioning as a sintering aid has corrosion resistance for rare earth-transition metal magnets. In addition to providing, it has the function of cleaning the interface with the main phase during sintering and improving the coercive force.

Such low melting point RE-TM alloy and / or RE-
The TM-B alloy powder is manufactured by melting raw materials weighed to a predetermined composition in a vacuum or an inert atmosphere by arc melting, high frequency melting, etc. to prepare an ingot, and then coarsely pulverizing and finely pulverizing the ingot. It was Further, prior to the coarse pulverization, a homogenous treatment or a hydrogen embrittlement treatment may be performed.

[0009]

By the way, in the above fine pulverization, a fine powder having an average particle diameter: several μm or less was used by using a ball mill, a jet mill, etc., but a low melting point RE-TM alloy and / or RE was used. -TM-B alloy is RE ₂ TM
_Since it is more ductile than ₁₄ B ₁ , fine pulverization was extremely difficult. In addition, this low melting point alloy has a larger RE / TM ratio than RE ₂ TM ₁₄ B ₁ and a relatively large amount of RE, so it is highly oxidative in the fine powder state and ignites in the atmosphere, so it is easy to handle. Since magnets need delicate attention and are easy to take in oxygen and oxidize even if they do not ignite, a magnet produced from such a powder has a problem that the coercive force is slightly low.

The present invention advantageously solves the above-mentioned problems, and in the production of rare earth-transition metal magnets, fine grinding of RE-TM alloy and / or RE-TM-B alloy having a low melting point is more preferable. It is intended to be carried out easily and with a small degree of oxidation.

[0011]

Means for Solving the Problems That is, the present invention
E ₂ TM ₁₄ B ₁ (where RE is one or more selected from Y, Sc and lanthanoids. TM is Fe, Co and Ni
One or more selected from the above. ) Phase powder and RE-TM having a lower melting point (where RE and TM are
Same as above) and / or RE-TM-B (where RE,
(TM is the same as the above) In a method for producing a rare earth-transition metal-based sintered magnet, which comprises mixing powder including an alloy based on the above, compression-molding the mixture, and sintering the mixture. A method for producing a rare earth-transition metal magnet, comprising finely pulverizing a TM-based alloy and / or a RE-TM-B-based alloy while mixing RE ₂ TM ₁₄ B ₁ phase powder.

[0012]

According to the present invention, RE-TM is rich in ductility, hard to be crushed, has a lower melting point than RE ₂ TM ₁₄ B ₁ phase and has a large RE / TM ratio.
Milling of the alloy and / or RE-TM-B alloy is performed with RE ₂ TM ₁₄ B ₁
In the presence of, the harder RE ₂ TM ₁₄ B ₁ phase acts as a grinding aid, so that grinding becomes easier. In addition, the average RE element concentration decreases and the activity of the powder as a whole decreases, so the oxidizability is weakened, so handling of the fine powder becomes easier and the oxygen concentration when used as a magnet is reduced. The coercive force can be improved. The fine pulverization according to the present invention includes not only dry pulverization but also cyclohexane,
It may be wet grinding using alcohol or other liquid.

The fine pulverization according to the present invention is preferably carried out until the average particle diameter of the fine powder particles becomes about 1 to 10 μm.
When it is less than 1 μm, in addition to the fact that it is very difficult to pulverize it, the oxidation property is too strong and the characteristics are likely to be deteriorated according to the present invention. Because it will decrease. Also RE ₂ TM
The mixing ratio of the RE-TM based alloy and / or the RE-TM-B based alloy to ₁₄ B ₁ is preferably about 3.0 to 20 by weight. The reason is that if it is less than 3.0, the magnet characteristics, especially the residual magnetic flux density is deteriorated, while if it exceeds 20, the sinterability is deteriorated. If the above mixing ratio is satisfied, a desired magnet composition is also satisfied, and thus the obtained mixed powder can be used as it is as a sintering raw material.

Here, the RE ₂ TM _I14 B ₁ phase means, for example, Nd ₂ (F
It has a high saturation magnetic flux density such as e, Co, Ni) ₁₄ B ₁ phase and is the main phase of this magnet alloy. Further, as the low melting point alloy powder, one having the following composition is suitable. RE-TM series RE ₁ TM _1-X , RE ₇ TM ₃ , RE ₃ TM. RE-TM-B system RETM ₄ B, RE ₂ TM ₅ B ₂ ,, RE ₂ TM ₇ B ₃ ,, RE ₂ TM ₅ B ₃ ,, RETM ₂ B ₂ ,, RE ₂
TMB _{3 The} low melting point RE-TM and RE-TM-B alloys listed above are
The compound is not limited to the single-phase compound as described above, and a mixed crystal of two or more of these may be used.

Furthermore, the mixing ratio of both is 95:
It is preferably about 5 to 40:60. This is because if the ratio of the two is out of the above range, there is a disadvantage that the coercive force and the saturation magnetic flux density are significantly deteriorated. Here, the formula unit corresponds to a case where Nd ₂ Fe ₁₄ B is regarded as one molecule (this is called a formula in a solid state), for example. As described above, the particle size of each powder to be mixed is preferably about 0.5 to 5 μm for easy handling and homogeneous mixing.

[0016]

【Example】

And an ingot by arc melting a RE-TM alloy represented by the composition of Example 1 Nd ₃ Ni. The ingot, (10% H ₂ + A
r) After embrittlement treatment at 300 ° C for 1 hour in an atmosphere, coarse crushing was performed with a stamp mill to obtain an average particle size of 250 µm. Nd ₃ when this powder was ground with a rotary ball mill using zirconia beads together with 5 times the weight of RE ₂ TM ₁₄ B ₁ powder, which had been ground in advance with a jet mill to an average particle size of several μm.
Figure 1 shows the results of an investigation of changes over time in the average particle size of Ni.
Shown in. In addition, FIG. 1 also shows, for comparison, the results of an investigation in which a coarse powder of Nd ₃ Ni was similarly pulverized by a ball mill in the same manner. The target particle size is an average particle size: several μm. As is clear from the figure, according to the present invention, RE ₂ TM ₁₄
When crushed in the presence of B _1, the crushing time could be shortened significantly.

Nd ₃ obtained in the same manner as in the above embodiment
The same amount of coarse Ni powder as RE ₂ TM ₁₄ B ₁ coarse powder (average particle size 250
After mixing evenly with a rocking mixer, it was pulverized by a jet mill using Ar and finely pulverized, and then fine powder with an average particle size of several μm was dropped in the atmosphere from a height of 15 cm. Did not ignite. On the other hand, the coarse powder of Nd ₃ Ni prepared in the same manner was pulverized with a similar jet mill to an average particle diameter of several μm by itself, and when it was dropped under the same conditions, it ignited and completely oxidized. ..

Example 2 Nd ₃ Ni coarse powder obtained in the same manner as in Example 1 was mixed with 8 times the weight of Nd ₂ (Fe _0.62 Co _0.30 Ni _0.08 ) ₁₄ B ₁ (RE / TM ratio = 1 /
7) was mixed with the same method as in Example 1, and the mixed powder was finely pulverized by a jet mill to obtain fine powder having an average particle diameter of several μm. Then, this mixed powder was compression-molded in a magnetic field of 12 kOe and then sintered at 1025 ° C. for 2 hours. When the oxygen concentration and magnetic characteristics of the obtained magnet were examined, the oxygen content was 3000 p.
pm, and the coercive force was 15.8 kOe.

On the other hand, Nd ₃ Ni and Nd ₂ (Fe _0.62 Co _0.30 Ni _0.08 )
₁₄ B ₁ and ₁₄ B ₁ were individually finely pulverized, then mixed in a rocking mixer in the above proportion, and then molded and sintered in the same manner.
The oxygen concentration and coercive force of the magnet thus obtained are
It was 5000 ppm and 12.2 kOe.

Example 3 Nd ₃ Ni coarse powder obtained in the same manner as in Example 1 was mixed with 18 times the weight (mixing ratio: 18) of Nd ₂ (Fe _0.62 Co _0.30 Ni _0.08 ) ₁₄ B ₁ and After mixing in the same manner as in No. 1, the mixed powder was treated in the same procedure as in Example 2 to produce a magnet. The oxygen concentration and coercive force of the magnet thus obtained were 2500 ppm,
It was 14.2 kOe.

On the other hand, Nd ₃ Ni and Nd ₂ (Fe _0.62 Co _0.30 Ni _0.08 )
₁₄ B ₁ and ₁₄ B ₁ were individually finely pulverized and mixed as in Example 2, and similarly shaped and sintered to obtain an oxygen concentration and a coercive force of a magnet of 4500 ppm and 10.1, respectively. It was kOe.

[0022]

As described above, according to the present invention, the RE-TM alloy having the RE concentration higher than that of the RE ₂ TM ₁₄ B ₁ phase as compared with the conventional manufacturing method,
Not only can the efficiency of crushing the RE-TM-B alloy be increased, but the risk of ignition is reduced, making it easier to handle, and the oxygen concentration of the magnet can be kept low, so that the magnetic characteristics can be improved.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the average particle size and the pulverization time when the method of the present invention and Nd ₃ Ni were finely pulverized.

Claims (1)

[Claims] 1. RE ₂ TM ₁₄ B ₁ (where RE is one or more selected from Y, Sc and lanthanoids.
Is one or more selected from Fe, Co and Ni. ) Phase and RE- whose melting point is lower than that
TM (here, RE and TM are the same as above) alloy and / or RE
-TM-B (where RE and TM are the same as above) are mixed with a powder of an alloy, and the mixture is compression-molded and then sintered to obtain a rare earth-transition metal-based sintered magnet. In the production method, the low melting point RE-TM type alloy and / or RE-TM-B type alloy is finely pulverized while mixing RE ₂ TM ₁₄ B ₁ phase powder. Magnet manufacturing method.