JPH1126221A - Rare earth bonded magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rare earth bonded magnet which is high in corrosion resistance and mechanical strength, by a method wherein a magnet main body is formed of a mixture composed of a rare earth magnet powder and resin binder mixed at the required ratio, and all the surface of the magnet main body is coated directly with a metal plating layer. SOLUTION: A magnet main body 12 of a rare earth bonded magnet 10 is formed through such a manner that resin binder is added to magnetic material powder which contains one or more elements selected out of rare earth elements such as Sm, Nd, Pr and the like, the magnetic material powder mixed with resin binder is kneaded and injection-molded or compression-molded into a required shape. The magnet main body 12 is so set as to be 100 μm or less in surface roughness and 5.0 to 6.5 g/cm<3> in density. All the surface of the magnet main body 12 is coated with a metal plating layer 14 of thickness 5 to 50 μm. The metal plating layer 14 is formed of nickel or chrome. By this setup, a metal plating layer is imposed in film-forming efficiency, corrosion resistance and mechanical strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth bonded magnet, and more particularly, to a rare earth bonded magnet in which a metal plating layer is directly coated on the entire surface of a magnet main body.

[0002]

2. Description of the Related Art Rare earth obtained by injection molding or compression molding of a mixture obtained by mixing a powder of a magnetic material containing one or more kinds of rare earth elements such as Sm, Nd, Pr and a resin binder in a required ratio. Bond magnets are suitably used, for example, for motor rotors and the like. However, since rare-earth bonded magnets contain raw materials that are easily oxidized, rust easily occurs over time if the surface is unmodified, and if used as such for motor parts, the durability and failure may be reduced. Will be invited. Therefore, a measure is generally taken to coat the surface of the rare-earth bonded magnet with a resin film by spray coating, electrodeposition coating, dip coating or the like to prevent rust.

[0003]

However, in a product using a rare-earth bonded magnet whose surface is covered with a resin film, the mechanical strength is low, and the resin film is damaged during the assembling process or erroneously occurs during transportation. Difficulties such as being easily damaged when dropped are pointed out. Therefore, a proposal has been made to improve the mechanical strength by performing a base treatment on the surface of the rare-earth bonded magnet, and further covering the surface with a metal plating layer. However, in this case, it is pointed out that the unevenness of the thickness of the underlayer becomes an unstable factor of the metal plating layer, and the film formation efficiency of the plating layer is reduced, and thereby the corrosion resistance is also reduced. In addition, the number of steps is increased due to the base treatment, and the productivity cannot be improved.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks inherent in the prior art, and has been proposed in order to suitably solve the drawback. The present invention provides high corrosion resistance and high mechanical strength. It is an object of the present invention to provide a rare earth bonded magnet that can be improved.

[0005]

In order to overcome the above-mentioned problems and achieve the intended object, a rare-earth bonded magnet according to the present invention is a magnet made of a mixture obtained by mixing a rare-earth magnet powder and a resin binder in a required ratio. A main body is formed, and the entire surface of the magnet main body is directly covered with a metal plating layer.

[0006]

Next, a rare earth bonded magnet according to the present invention will be described with reference to the accompanying drawings. FIG. 1 and FIG. 2 show a rare earth bonded magnet according to an embodiment, and a magnet main body 12 of the rare earth bonded magnet 10.
Can be obtained by adding or kneading a resin binder to a magnetic material powder containing one or two or more rare earth elements such as Sm, Nd, and Pr into a required shape or by injection molding or compression molding. The magnet body 12 has a surface roughness at 100μm or less, the density is preferably between 5.0~6.5g / cm ³ is set to 6.0 g / cm ^3. The entire surface of the magnet main body 12 is covered with a metal plating layer 14 having a thickness of 5 to 50 μm. In addition, as the metal material used for the metal plating layer 14, nickel, chromium, or the like is preferably used.

FIG. 3 is a flowchart showing the steps of manufacturing the rare earth bonded magnet according to the embodiment. In addition, the magnet main body 12 used in the examples includes, for example, Nd 27 wt%, Fe 67 wt%, B 1 wt%, C
o An alloy powder having an average particle size of 150 μm having a composition of 5 wt%, a coupling agent of 0.1 wt%, and an epoxy resin of 1.5
３3.0 wt% and a lubricant are added, kneaded, compression molded at a required pressure, and then cured by heat treatment at 170 ° C. for 30 to 60 minutes. Each manufacturing condition is set so that the surface roughness of the obtained magnet main body 12 is 100 μm or less and the density is 5.0 to 6.5 g / cm ³ . The composition of the alloy powder is Nd 30 wt.
%, 69 wt% of Fe, and 1 wt% of B.

Next, the magnet body 12 is washed with pure water to remove impurities adhering to the surface. Then, the magnet main body 12 is subjected to electrometal plating using nickel as a plating metal, and then dried through a washing step. Thereby, the rare earth bonded magnet 10 having high corrosion resistance and improved mechanical strength in which the entire surface of the magnet main body 12 is directly covered with the nickel plating layer is obtained. In addition, as the electrometal plating, a barrel method in which the magnet main body 12 is loaded into a barrel tank storing a plating solution, and the tank is rotated and plating is performed by applying a current to an electrode provided in the tank. Is preferably used.

[0009]

Test Examples of Examples: Rare earth bonded magnets directly covered with a metal plating layer and rare earth bonded magnets coated with a metal plating layer after being subjected to a conventional undercoating treatment according to the above-described embodiment. Was placed in an atmosphere of 80 ° C. × 95% and inspected for the occurrence of rust. The results are shown in Table 1 below. The test results are shown as the ratio of the number of rusts generated to 20 rare-earth bonded magnets (the number of rusts generated / 20).

[0010]

Table 2 shows the results obtained by applying a stress load to each of the 20 rare earth bonded magnets of the embodiment and the conventional rare earth bonded magnet using a load cell and measuring the breaking strength.

[0012]

That is, from the test results, the magnet body 1
The rare-earth bonded magnet 10 of the embodiment in which the metal plating layer 14 is directly coated on the entire surface of the second example 2 has a higher corrosion resistance (corrosion prevention) than the conventional rare-earth bonded magnet in which the metal plating layer is coated after the base treatment. Effect) and the breaking strength were both improved. This is thought to be because the metal plating layer 14 does not have an underlayer that becomes an unstable element, so that the efficiency of forming the plating layer 14 is improved, and thereby the corrosion resistance is improved.

[0014]

As described above, according to the rare earth bonded magnet of the present invention, the entire surface of the magnet body is directly covered with the metal plating layer, so that the efficiency of forming the metal plating layer is improved and the corrosion resistance is high. Can be secured. In addition, since the mechanical strength of the rare earth bonded magnet is improved by the metal plating layer, in a product using the rare earth bonded magnet,
Damage during the assembling process and erroneous damage during transportation can be suppressed, and there is an advantage that handling becomes easy. Further, since it is not necessary to perform a base treatment, there is an advantage that the number of manufacturing steps is reduced and productivity is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a rare-earth bonded magnet according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing an enlarged main part of the rare earth bonded magnet according to the embodiment.

FIG. 3 is a flowchart illustrating a manufacturing process of the rare-earth bonded magnet according to the embodiment.

[Explanation of symbols]

 12 Magnet body 14 Metal plating layer

Claims (5)

[Claims] 1. A rare earth element comprising a mixture of a rare earth magnet powder and a resin binder mixed at a required ratio to form a magnet body, and a metal plating layer directly covering the entire surface of the magnet body. Bond magnet. 2. The rare earth bonded magnet according to claim 1, wherein the metal plating layer is a nickel plating layer. 3. The magnet body has a surface roughness of 100 μm.
The rare earth bonded magnet according to claim 1, wherein: 4. The density of the magnet main body is 5.0 to 6.5 g.
/ Cm ³ rare-earth bonded magnet according to any one of claims 1 to 3. 5. The metal plating layer has a thickness of 5 to 50 μm.
The rare earth bonded magnet according to any one of claims 1 to 4, wherein m is m.