JPH01239901A - Rare-earth magnet and its manufacture - Google Patents

Abstract

PURPOSE:To improve oxidation-resistant properties and the moldability by a method wherein low melting point metal is mixed with magnetic alloy powder in a specific volume ratio and dispersed uniformly on the surfaces of the powder particles. CONSTITUTION:Low melting point metal is mixed with magnetic alloy whose composition is expressed by RxFe1-x-y-zByXz (wherein R denotes one or two or more among rare-earth elements, X denotes one or two or more among Co, Ni, Mn, Cr, Mo, Nb, V, Cu, Ti, Zn, Pb, Sn, C, P, Si, Al, Ca and N, 8<=x<=20, 2<=y<=15 and 0<=z<=8). The volume ratio of the low melting point metal to the mixture is not higher than 10%. The low melting point metal is mixed in the melted state at a temperature not higher than 800 deg.C and dispersed uniformly so as to cover the surfaces of the powder particles of the magnetic alloy. With this constitution, oxidation-resistant properties and the moldability for powder compression molding and hot press can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to the improvement of R-Fe-B rare earth magnets, and also includes a method for producing the same.

[Conventional technology I R-Fe-B rare earth magnets, represented by Nd-Fe-811 stone, have excellent magnetic properties and have the advantage that raw materials are cheaper than conventional rare earth magnets. Because of this, it is rapidly becoming popular.

On the other hand, this magnetic alloy has the disadvantages of low heat resistance and oxidation resistance, and is difficult to process due to the brittleness characteristic of intermetallic compounds. In addition, when an anisotropic magnet is made from this magnet alloy through the process of ultra-quenching → hot pressing and upsetting, the thermal history during the process coarsens the crystal grains and lowers the coercive force iHc. ,
A coercive force improving element such as Ga must be added.

As a countermeasure to such problems, it has been disclosed, for example, that a powder having a melting point lower than that of the rare earth element is added to a partially oxidized magnetic alloy powder or a powder containing a large amount of Feff1 as a sintering aid. (Unexamined Japanese Patent Publication No. 61-263201 >
, the applicant also proposed adding metal as a binder during hot pressing (Japanese Patent Application No. 62-230855).
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However, these methods involve mixing powders together and require good dispersion, but the quality of dispersion depends on the average particle size, particle size distribution, specific gravity, etc. of the powders to be mixed, and good results are difficult to achieve. What you can get is limited. In particular, powders such as Pb and A1, which have a large specific gravity difference with the magnet alloy powder, and powders such as Qa, which have a fine powder of 1 q at room temperature.
Those that are difficult to analyze are not suitable for the above method.

[Problem to be Solved by the Invention 1 The purpose of the present invention is to solve the problem of R-FC! - To provide a rare earth magnet that improves oxidation resistance reliably, prevents a decrease in coercive force, and has good squareness by drastically improving the conventionally proposed method for the purpose of improving the magnetic properties of B rare earth magnets. It is in.

In manufacturing the magnet, it is also an object of the present invention to provide a method for manufacturing a rare earth magnet that improves formability during hot pressing and workability during plastic deformation for imparting anisotropy. be done.

[Means for Solving the Problems 1] The rare earth magnet of the present invention has the following characteristics: RX Foi-x-y-z By Xz [R is one or more rare earth elements, X is Co, Ni, Mn, C
r, Mo, Nb, V.

CI, Ti, Zn, Pb, 3n, C, P, S
i.

AfJ, (representing one or more types of 3a and N, respectively, 8≦x≦20, 2≦y≦15.O≦2≦8) and a magnetic alloy containing inevitable impurities; ao o'c
It is made of a mixture with a low melting point metal having a lower melting point, the low melting point metal occupies 1096 or less of the volume of the mixture, and is formed by molding a material that is present in a uniformly dispersed state on the surface of the powder of the magnetic alloy.

Examples of low melting point metals include Al, Ga, In, T, and Q.

Zn, Cd, Hg, Sn, Pb and [one or more metals selected from 3i, alloys thereof,
or low melting point alloy l-3,5Nd or 8ρ
-2.5Dy is appropriate. When used, it is necessary that it accounts for 0.5% or more of the mixture by weight, but it should not exceed 10%.

The method for producing a rare earth magnet of the present invention includes the following components: RX Fol-X-y-Z BV and magnetic alloy powder containing unavoidable impurities.
A low melting point metal having a melting point lower than aoo'c is mixed in a proportion where the latter accounts for 10% or less of the mixture by volume at a temperature that is above the melting point of the low melting point metal and below 800°C, and a magnet is formed. It consists of uniformly dispersing a low melting point metal on the surface of alloy powder and then forming it.

Molding can be performed by various means such as hot pressing, hot isostatic pressing, and discharge sintering. Separately, the term "molding" here also includes the use of a thermosetting resin, typically epoxy resin, in an amount of usually 5% or less by weight to make a so-called plastic magnet.

By plastically deforming it at a temperature of O'C, it becomes anisotropic.

It goes without saying that the molded body of magnetic alloy powder imparted with anisotropy can be magnetized as it is and made into a product, but it is also possible to crush it and knead the resulting powder with a thermosetting resin.
An anisotropic plastic magnet can also be obtained by curing the magnet while orienting it in a magnetic field.

[Function 1] The rare earth magnet alloy itself used in the present invention is known, and the reasons for limiting the composition are also known.

A feature of the invention therefore lies in the use of low melting point metals. Low melting point metals are in a molten state! By mixing the i-magnetic alloy powder, it is possible to uniformly disperse the powder so as to cover the entire surface of the powder.

This improves the moldability during powder molding and hot pressing, and makes it easier to obtain a high-density molded body. Furthermore, the workability during plastic deformation is also increased, which is advantageous for imparting anisotropy.

If this rare earth magnet alloy is left at a high temperature exceeding 800°C for a long time, the crystal grains will become coarse and the magnetic properties, particularly the coercive force, will decrease, so it is mixed with a low melting point metal at a temperature below 800°C.

When hot molding is carried out, any means can be used as described above. Unless the temperature is 500°C or higher, the compact will not have the required density, but for the reasons mentioned above,
Again, the temperature must not exceed 800°C. The same applies to plastic deformation for imparting anisotropy.

It is desirable to uniformly disperse the low melting point metal on the surface of the magnet alloy powder in as small a quantity as possible, but it is usually required to be 0.5% or more by weight. If more than 10% is used, the magnetic properties will be significantly degraded due to dilution of the magnet alloy, so this is the upper limit.

[Example 1] Raw materials were melted in a vacuum melting furnace to have an alloy composition of 14Nd-81Fe-5B in atomic ratio.

The molten metal is poured into a single-roll metal ribbon manufacturing device and rapidly cooled.
Thin slices approximately 20μ thick were obtained.

This flake was crushed until it passed 60 meshes, and then
A certain amount of low melting point metals as shown in the table were blended and mixed for 10 minutes under heating in a V-type mixer with vacuum suction.

Subsequently, the mixture was heated to a temperature of 700°C using a vacuum hot press device.
It was molded by heating and pressing at a temperature of 1.51 mm/cm at a pressure of 1.51 mm/cm for 3 minutes.

Regarding the compact, the state of dispersion of the low melting point metal therein was examined, and the magnetic properties of the isotropic magnet obtained from the compact were measured.

For comparison, the same low melting point metals used in the above examples were mixed at room temperature and molded in the same manner. Regarding the molded object,
The above observations and magnetic measurements were carried out.

The above results are summarized in Table 1. In Table 1 and the following tables, the numbers marked with * are comparative examples.

[Example 2] The molded bodies Nα1.3, 7, and 9 obtained by 1q in Example 1 were further heated to 700°C and subjected to upset processing at a processing rate of 60% to align the axes of easy magnetization in the pressing direction. An anisotropic magnet was obtained.

Again, for comparison, the molded product N obtained by mixing low melting point metals at room temperature and hot press molding in Example 1.
o, 2.4, and 8.10 were similarly upset.

In addition to observing the occurrence of cracking due to upset processing, the magnetic properties of the obtained anisotropic fli1 stone were measured.

The results are summarized in Table 2.

In addition, demagnetization curves were drawn for the anisotropic magnets of Nα7 and Nα8*, and the squareness was examined. The results are shown in FIG.

Table 2 ◎ No cracking ○ Fine cracking △ Significant cracking on the outer periphery [Example 3] Comparison between the molded body that becomes an isotropic magnet at 1q in Example 1 and the anisotropic magnet obtained in Example 2. Each of the molded bodies was coarsely pulverized to 60 mesh or less, and kneaded with 2% epoxy resin. It is molded at a pressure of 7 tons/Ct/l,
I made it into a bond magnet. An anisotropic powder was magnetically oriented with an applied magnetic field of 15 KOe to form an anisotropic magnet.

A bonded magnet was also created using the same process for a molded article prepared for comparison.

The magnetic properties of each were measured and the results shown in Table 3 were obtained.

Table 3 [Effects of the invention] According to the method for manufacturing a rare earth magnet of the present invention, R-Fe7B
When manufacturing permanent magnets from rare earth magnet powder, it is possible to operate with good formability and workability.
This effect can also be obtained when a molded body is plastically worked to impart anisotropy.

In this way, the magnet of the invention has high magnetic properties.

[Brief explanation of the drawing]

FIG. 1 is a demagnetization curve of a magnet obtained in an example of the present invention. Patent Applicant Daido Steel Co., Ltd. Agent Patent Attorney Souo Suga Figure 1-H [KOel

Claims (7)

[Claims] (1) R_xFe_1_-_x_-_y_-_zB_y
X_z [R is one or more rare earth elements, X is C
o, Ni, Mn, Cr, Mo, Nb, V, Cu, Ti,
Each represents one or more of Zn, Pb, Sn, C, P, Si, Al, Ga and N, and the components of 8≦x≦20, 2≦y≦15, 0≦z≦8] It consists of a mixture of a magnetic alloy containing unavoidable impurities and a low melting point metal having a melting point lower than 800°C, the low melting point metal occupies 10% or less of the mixture by volume, and is uniformly distributed on the surface of the magnetic alloy powder. Rare earth magnets are formed by molding materials that exist in a dispersed state. (2) Al, Ga, In, Tl, Z as low melting point metals
One or more metals selected from n, Cd, Hg, Sn, Pb and Bi, alloys thereof, or low melting point alloys Al-3.5Nd or Al-2.5Dy
The rare earth magnet according to claim 1, wherein the rare earth magnet uses: (3) R_xFe_1_-_x_-_y_-_zB_y
X_z [wherein R and X have the above meanings, x, y
and z are the values given above. ] A magnetic alloy powder having the following components and containing unavoidable impurities;
A low melting point metal having a melting point lower than 800°C is mixed in a proportion where the latter accounts for 10% or less of the mixture by volume at a temperature that is above the melting point of the low melting point metal and below 800°C, and a magnetic alloy powder is obtained. A method for producing rare earth magnets, which consists of uniformly dispersing a low melting point metal on the surface of the magnet and then forming it. (4) The manufacturing method according to claim 3, wherein the shaping is performed by hot pressing, hot isostatic pressing, or discharge sintering. (5) The manufacturing method according to claim 3, further comprising the step of imparting anisotropy by plastically deforming at a temperature of 500 to 800° C. after molding. (6) The manufacturing method according to claim 3, wherein the molding is performed using a thermosetting resin that accounts for 5% or less of the mixture by weight. (7) After imparting anisotropy through plastic deformation, the molded body is pulverized, and the resulting powder is mixed with 5% or less of a thermosetting resin by weight, and the mixture is cured while being oriented in a magnetic field. 5
manufacturing method.