JPH0513207A - Manufacture of r-t-b-based permanent magnet - Google Patents

Abstract

PURPOSE:To add an additive which enhances a coercive force without lowering a Curie temperature, to selectively put the additive which enhances the coercive force into a grain boundary and to enhance the coercive force without lowering a residual flux density. CONSTITUTION:The manufacturing method of an R-T-B-based permanent magnet is featured by using a liquid mixed body composed of the following as a starting raw material: the magnetic powder of an R-T-B-based alloy which uses a transition metal T as a main component and which contains rare-earth elements R including yttrium and boron B; and an alloy composed of one or more kinds of Ga, In and Sn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic anisotropic magnet material composed of a rare earth / transition metal / boron alloy, and more particularly to a magnetic anisotropic Nd-Fe-B magnet having a large magnetic energy product. .

[0002]

2. Description of the Related Art Permanent magnets consisting essentially of rare earths, transition metals, and boron (hereinafter referred to as RTB-based permanent magnets) have been attracting attention because they are inexpensive and have a high energy product. R ₂ T ₁₄ B with a tetragonal crystal structure (R is Y
This is because the intermetallic compound represented by (rare earth element including) exhibits excellent magnetic properties. This intermetallic compound has a tetragonal crystal structure. For example, the lattice constant of Nd ₂ Fe ₁₄ B is Ao = 0.878 nm and Co = 1.218 nm. However, while this RTB-based permanent magnet has the above-mentioned advantages, it has a disadvantage of poor thermal stability due to the low Curie temperature. Generally, in order to improve the thermal stability, improving the Curie temperature or coercive force is used. The use of additives is effective for improving the Curie temperature of the RTB magnet.
For example, by substituting a part of Fe with Co, the Curie temperature is improved and the reversible temperature coefficient of the magnet is improved (Japanese Patent Laid-Open No. 59-64733). In addition, the combined addition of Co and Ga improves both the Curie temperature and the coercive force.
64-7503). According to the latter method, Ga mainly enters the crystal grain boundary and acts as a pinning site for suppressing magnetization reversal, and Co forms a solid solution in the R ₂ Fe ₁₄ B 1 phase which is the main phase to improve the Curie temperature.

[0003]

The method of improving thermal stability described in the prior art has the following problems. That is, addition of Dy improves coercive force and thermal stability,
Dy is expensive and has a shortage of resources. Further, although the addition of Co improves the Curie temperature, it lowers the crystal magnetic anisotropy, and therefore the coercive force decreases. Also,
Addition of Ga has a drawback that the Curie temperature is lowered due to the fact that Ga also forms a solid solution in the main phase. An object of the present invention is to develop an R-Fe-B based permanent magnet material having improved Curie temperature and coercive force.

[0004]

The present invention firstly provides an RTB-based alloy containing a transition metal T as a main component and a rare earth element R containing yttrium and boron B, or a melt-quenched thin piece or ribbon thereof. The present invention relates to an RTB-based permanent magnet characterized by being manufactured by mixing a magnetic powder obtained by means such as pulverization and a low melting point metal, and then warm working. Ga-In-Sn ternary alloy, Ga-In
It was discovered that the binary alloy, Ga-Sn binary alloy, is a stable liquid at room temperature. Further, these alloys also have good fluidity and wettability. Further, in the R-T-B system permanent magnet, the constituent elements of the above-mentioned alloy improve not only Ga but also coercive force. Therefore, these Ga, In, and Sn-based liquid alloy, by adding to the R-T-B-based magnetic powder, not a solid solution an additional element to the R ₂ T ₁₄ B main phase, solving the problems described above were did.

[0005]

【Example】

(Example 1) An alloy having a composition of Nd ₁₄ Fe ₈₀ B ₆ was prepared by arc melting. The peripheral speed of this alloy is 30 in Ar atmosphere.
It was injected onto a single roll rotating at m / sec to produce an irregular flake flakes having a thickness of about 30 μm. As a result of X-ray diffraction, it was found to be a mixture of amorphous and crystalline. Then, the magnetic powder obtained by pulverizing the flaky flakes to 500 μm or less and 60 wt% Ga-20
A liquid alloy of wt% In-20 wt% Sn was put in a mixer and stirred. The obtained powder is molded under a pressure of 6 tons / cm ^2.
And the density is 5.7g / c
In c, a molded body having a diameter of 28 mm and a height of 47 mm was produced.
The obtained molded body was hot-pressed at 740 ° C. and 2 ton / cm ² , and had a high density of 7.4 g / cc and a diameter of 30 m.
A molded product having a height of m and a height of 30 mm was obtained. Next, the densified compact was further compressed at 740 ° C.
The value was obtained by dividing mm by the height 7.5 mm after the upsetting) to be 4 so as to give a magnetic anisotropy by warm working by upsetting. After measuring the magnetic properties of the obtained magnetically anisotropic warm-worked magnet, a cross section including the compression axis direction of the magnet was subjected to elemental analysis linearly in the compression direction using EPMA. As shown in FIG. 1, when Ga is added by adding the liquid alloy according to the present invention, it can be seen that the residual magnetic flux density decreases more gradually as the Ga content increases, as compared with the prior art. Furthermore, the coercive force is rapidly improved by adding Ga. According to FIG. 2, it can be seen that the Ga addition method according to the present invention has a sharper Ga peak in the Nd-rich portion (Nd-rich phase at the flake boundary) as compared with the prior art. From the above results, Nd by the Ga addition method according to the present invention
It is considered that Ga is allowed to enter the rich flake boundary more selectively than in the conventional technique, thereby improving the coercive force and maintaining the residual magnetic flux density. (Example 2) In Example 1, the flaky composition was changed to Nd ₁₄ Fe.
Ga was added at 1 at% by the same addition method as _72.5 Co _7.5 B ₆ to prepare a warm-worked magnet. Further, as Comparative Example 2, a warm-worked magnet was produced by adding the same amount to the conventional method of arc melting. Further, as Comparative Example 3, a thin piece having a composition of Nd14Fe72.5Co7.5B6 was similarly prepared without adding Ga to prepare a warm-worked magnet. The results are shown in Table 1.
Shown in.

[0006]

[Table 1] From the results in Table 1, it can be seen that Ga addition was successful and the coercive force was improved without lowering the Curie temperature. Also in this result, as shown in FIG. 2, Ga is a flake boundary (grain boundary).
It is believed that this is due to selective entry into. Although the above description has been made by combining the ultra-quenching method and the warm working method, the present invention is not limited thereto, and known means such as a mechanical alloying method and a powder metallurgy method can be applied. .

[0007]

According to the present invention, an additive that improves the coercive force can be added without lowering the Curie temperature. Further, an additive that improves the coercive force can be selectively added to the crystal grain boundary, and the coercive force can be improved without lowering the residual magnetic flux density.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between magnetic properties and Ga content in one embodiment of a permanent magnet according to the present invention together with a comparative example.

FIG. 2 is a diagram showing an element distribution of a cross section in one example of the permanent magnet according to the present invention together with a comparative example.

Claims (5)

[Claims] 1. A liquid mixture of a magnetic powder of an RTB-based alloy containing a transition metal T as a main component and a rare earth element R containing yttrium and boron B, and an alloy of Ga and one or more of In and Sn. R-T characterized by using body as a starting material
-A method for manufacturing a B-based permanent magnet. 2. The liquid mixture is Ga—In, Ga—Sn,
The method for producing an RTB-based permanent magnet according to claim 1, wherein the method is one or more kinds of Ga-In-Sn alloys. 3. The RT according to claim 1, wherein the starting material is a permanent magnet by powder metallurgy.
-A method for manufacturing a B-based permanent magnet. 4. The method for producing an RTB-based permanent magnet according to claim 1, wherein the starting material is made into a permanent magnet by a liquid quenching method and a warm working method. 5. The method for producing an RTB-based permanent magnet according to claim 1, wherein the starting material is made into a permanent magnet by mechanical alloying.