JPH11214234A - Manufacture of rare earth resin bonded magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To coat an inner part which is not easily coated with resin, by setting the ratio of the inner diameter of a cylindrical mold to the outer diameter within a specified range and by almost uniformly forming an organic film whose composition is different from that of an organic binder on the inner and outer circumference planes of the cylindrical mold. SOLUTION: After grinding a powder having an atomic ratio of Nd11 Fe80 B8 obtained by a super rapid cooling method into approximately 177 μm, epoxy resin is added and compression-molded. The mold is thermally set at approximately 150 deg.C to manufacture a magnet, and then organic material coating is performed by an impregnation method on the magnet. The ratio of the inner diameter of the cylindrical mold to the outer diameter is within a range of 1/6-24/25, and a coating film (organic film) such as of fluorine resin is almost uniformly formed on the inner and outer circumference planes of the cylindrical mold. At that time, the coating film thickness is 2-100 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a magnet powder having a basic composition of a rare earth metal, iron, and boron, which is formed by a super-quenching method, to which an organic binder is added. The present invention relates to a method for producing a high-performance rare-earth resin-bonded magnet having excellent oxidation resistance and immersed in an organic liquid by a method.

[0002]

2. Description of the Related Art Permanent magnets are roughly divided into three types: ferrite magnets, alnico magnets, and rare earth magnets.
The demand for rare-earth magnets has greatly increased with the recent miniaturization and higher efficiency of OA equipment and FA equipment.

[0003] Rare earth magnets are roughly classified into rare earth / cobalt and rare earth / iron based on their composition. Rare-earth and iron-based magnets were announced by General Motors (GM) and Sumitomo Special Metals in 1983, and both have Nd, Fe, and B as their main components. Sumitomo Special Metals employs the sintering method, while the sintering method is used.

In the case of the ultra-quenching method, a ribbon-shaped magnet powder having a thickness of about 20 μm is obtained, and each of them has a submicron order (0.1 to 0.1 μm) smaller than the critical radius of a single magnetic domain particle.
0.5 μm). Therefore 177μm
Even when the powder is pulverized into the following bulk powder, it is kept in a state where a coercive force is generated, so that it can be used as a raw material for a resin-bound magnet. Using the above raw materials and adding a thermosetting resin or a thermoplastic resin, magnets can take advantage of the resin-bonded magnets that can be formed into complex shapes, making them thinner, like cylindrical magnets, plate-like magnets, etc. And used in electronic equipment. However, since the composition contains a large amount of iron, it is easily rusted, and when incorporated in a motor speaker, a relay, or the like, the performance is remarkably deteriorated due to rust or oxidation, which deteriorates the magnet performance.

[0005] Therefore, an organic substance is sprayed on the surface to apply a coating, thereby obtaining oxidation resistance.

[0006]

However, the rare-earth and iron-based resin-bonded magnets having a cylindrical shape,
Even if the organic material coating is sprayed on a thing with a height of 5 or less, the organic material does not reach the inside, so the coating film thickness is extremely thin, and if it is going to be thick, it will be coated too thick on the outside, There was a problem that the dimensions could not be controlled. Therefore, in order to solve such a conventional problem, the present invention coats the magnet surface with an organic substance by immersing the magnet in an organic substance liquid by a dipping method, and spraying a resin on an inner part which is difficult to coat by spraying. The purpose is to prevent air, moisture, solvents, chemicals, etc., and to prevent oxidation and rust.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a method for manufacturing a rare earth resin-bonded magnet according to the present invention is directed to a magnet powder mainly composed of a rare earth metal, iron and boron and manufactured by a super-quenching method. A rare earth element formed by immersing a cylindrical molded body formed by adding an organic binder into a liquid of an organic substance to form an organic film having a thickness of 2 to 100 μm on at least an inner peripheral surface and an outer peripheral surface of the cylindrical molded body. A method of manufacturing a resin-bonded magnet, wherein the ratio of the inner diameter to the outer diameter of the cylindrical molded body is in the range of 1/6 to 24/25, the inner peripheral surface of the cylindrical molded body and the An organic film having a composition different from the composition of the organic binder is formed substantially uniformly on the outer peripheral surface.

[0008] In the present invention, the inner diameter of the cylindrical molded body is preferably 1 mm or more.

The composition of the magnet powder may be such that a part of the iron is replaced by a transition metal other than iron such as cobalt.

The organic coating material used in the present invention is a fluororesin containing ethylene tetrafluoride or the like, an epoxy resin, a nylon resin, a melamine resin, an acrylic resin, a phenol resin, or a silicone resin.

If the coating film thickness is less than 2 μm, the fine pores of the resin-bonded magnet cannot be filled, so there is no oxidation resistance. If the coating film thickness exceeds 100 μm, the working time becomes longer and the cost becomes higher. . The rare earth magnet powder whose basic composition is made of a rare earth metal, iron, and boron by a rapid quenching method is 8 to 18%, 73 to 88%,
-9% and rare earth metals are Y, La, Ce, Pr, Sm, Nd, Eu, Gd, T
b, Dy alone or a mixture of two or more, and part of iron is Al, C
It shall be substituted with at least one transition metal of o, Nd, Ga and the like. Such a magnet powder is added with an organic binder and formed into a cylindrical molded body by pressure molding. In order to make the coating film (organic coating) formed on the inner peripheral surface and the outer peripheral surface of this cylindrical molded body almost uniform, the ratio of the inner diameter to the outer diameter of the cylindrical molded body is 1/6 to 24. / 25.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

[0013]

EXAMPLES Example 1 A powder obtained by a super-quenching method having an atomic ratio of Nd ₁₄ Fe ₈₀ B ₈ and pulverized to 177 μm were added with an epoxy resin and compression-molded. The molded article was heat-cured at 150 ° C. for 1 hour to produce a magnet, followed by resin coating. Table 1 shows the magnet dimensions (outer diameter x inner diameter x height [unit: mm]), type of organic coating, film thickness, method,
The results of investigating the state of rust generation after 500 hours under the conditions of 60 ° C. and 95% (humidity) are shown.

As shown in the comparative examples of Nos. 11 and 12, the block shape is well coated by both spraying and dipping coating methods.

When the organic coating is applied to a thickness of 2 μm or more by the dipping method as in the case of the cylindrical magnets of Nos. 1, 3, 6, and 9, good rust prevention is exhibited.

However, when a cylindrical magnet is coated by spraying spray as in Nos. 2, 4, 7, and 8, even if the average value of the coating film thickness is 2 μm or more, the inner film thickness is small. Rust has occurred.

Further, as shown in No. 5, the coating film thickness is 2
If it is less than μm, no rust-preventing force is obtained.

[0018]

[Table 1]

Example 2 Magnet powder having an atomic ratio of Nd ₁₄ Fe ₇₇ Co ₄ B ₅ and obtained by a super-quenching method was pulverized to 177 μm, and then an epoxy resin was added thereto, followed by compression molding of a magnet, nylon 12 and Was added and mixed to obtain an injection-molded or extruded magnet.

The magnetic performances of these magnets were as shown in Table 2. Measurement magnetic field is 25kOe and 25 ℃
It was measured by V, S, M at the air temperature.

[0021]

[Table 2]

Table 3 shows the results after applying a fluororesin coating to these magnets having a performance of about 20 μm and conducting a corrosion test at 60 ° C. × 95% × 500H.

According to Table 3, for a cylindrical magnet,
The difference in corrosion resistance between the coating methods is apparent, and the one coated with the magnet immersed in an organic liquid by the dipping method shows higher corrosion resistance.

[0024]

[Table 3]

[0025]

As described above, according to the present invention, since the rare-earth resin-bonded magnet having a cylindrical shape is difficult to be coated by spraying, an organic coating is applied to a thickness of 2 to 100 μm by a dipping method. The ratio of the inner diameter to the outer diameter of the cylindrical molded body is in the range of 1/6 to 24/25, and a composition different from the composition of the organic binder on the inner peripheral surface and the outer peripheral surface of the cylindrical molded body. Since the organic coating of was formed substantially uniformly, a magnet having extremely excellent corrosion resistance could be manufactured. This has the effect that the shape of the rare-earth resin-bonded magnet used in motors, speakers, sensors, and the like is not limited, and a wide range of applications can be achieved.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22C 38/00 303 B22F 5/00 B H01F 1/08 H01F 1/08 A

Claims (1)

[Claims] 1. A cylindrical molded body containing a rare earth metal, iron and boron as main components and an organic binder added to a magnet powder produced by a super-quenching method, and immersed in an organic liquid.
A method for producing a rare-earth resin-bonded magnet in which an organic coating having a thickness of 2 to 100 μm is formed on at least an inner peripheral surface and an outer peripheral surface of the cylindrical molded body, wherein an inner diameter of the cylindrical molded body with respect to an outer diameter of the magnet is determined. Ratio is 1/6 to 2
Within a range of 4/25, wherein an organic coating having a composition different from the composition of the organic binder is substantially uniformly formed on the inner peripheral surface and the outer peripheral surface of the cylindrical molded body. Manufacturing method of mold magnet.