JP3075281U - High corrosion resistance Nd-Fe-B magnet - Google Patents

Abstract

(57) [Summary] [PROBLEMS] By closing pores (sealing treatment) generated in a plating film performed as a surface treatment of a neodymium magnet, the conventional plating treatment equipment can be replaced with a low-cost treatment without changing. The corrosion resistance should be significantly higher than the product. Kind Code: A1 The present invention is characterized in that fine pores formed in a plating film on the surface of a molded and sintered Nd—Fe—B magnet are sealed with an inorganic sealing agent. As the inorganic sealing agent, an impregnating agent composed mainly of an alkali metal silicate or an impregnated sealing agent composed of an anaerobic resin is used. With this configuration, the pores remaining in the coating of the plating layer are sealed by the sealing agent, and oxygen contact with the magnetic material is cut off through the pores, thereby suppressing generation of rust.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a Nd-Fe-B (neodymium-iron-boron) magnet having improved corrosion resistance.

[0002]

[Prior art]

 Instead of conventional permanent magnets such as ferrite magnets, alnico magnets, etc., today they have high magnetic properties that are superior to these, such as residual magnetic flux density (Br), coercive force, and maximum energy product (BHmax). Permanent magnets using rare earth elements as magnetic materials have become widespread. As the rare earth magnetic material, two kinds of samarium (Sm) and neodymium (Nd) are generally used. Magnet products include a samarium-cobalt (Sm-Co) magnet (abbreviated as "samakoba magnet"), There is a neodymium-iron-boron (Nd-Fe-B) magnet (abbreviated as "neodymium magnet"). There are other magnets using praseodymium (Pr), but they are not widely used.

[0003] Sintered magnets made of these rare earth magnetic materials are obtained by dissolving raw materials, pulverizing and pulverizing an ingot, press-forming it into a predetermined shape, sintering, and then plating the entire surface with a plating process. The process of forming a coating, performing rust prevention treatment, and magnetizing this is used to manufacture a magnet. Among the rare earth magnets of today, excluding temperature characteristics and rustability, they have the best magnetic properties and are relatively inexpensive. The other type of samakoba magnet is expensive, but has excellent temperature characteristics and is resistant to rust, so there is still much demand in an environment where the operating environment is high.

[0004]

[Problems to be solved by the invention]

 However, as described above, neodymium magnets are relatively inexpensive, but have the problem of being very rusty. Therefore, in the manufacturing process, a surface treatment for forming a plurality of layers of plating films on the entire surface after sintering by a plating process was required. However, it is difficult (almost impossible) to form a uniform and non-defect plating film by a general plating process performed in ordinary equipment, and as shown in FIG. At present, many fine pores of several μm to several tens μm reaching the magnetic material are generated. The presence of these pores is not so problematic in a relatively short period of time when the environment is good in temperature and humidity, but for a long period of time in a harsh environment (for example, a temperature of 40 ° C and a humidity of 80%). For example, when the magnetic material is used for 10 years, the magnetic material is oxidized from the pores to cause rust to progress inside, resulting in a serious problem. Of course, it is possible to use elaborate plating, vacuum deposition, electrodeposition coating, etc. to prevent the formation of vacancies, but the current general plating equipment cannot cope with this and requires new capital investment. And it was not practical due to high cost. This weakens the superiority of neodymium magnets, which are relatively cheaper than samakoba magnets.

Furthermore, in electrolytic plating and electroless plating, which can form a film at low cost and with good mass productivity, the plating solution that has penetrated through pores on the surface stays as it is, and corrosion of the magnet based on the plating solution, that is, magnetic properties, is caused. However, there is also a problem that the decrease in the amount of the water cannot be suppressed.

[0006]

【Purpose】

 In view of the above, the present invention has been made with a focus on the above-described problems, and the conventional plating treatment equipment has been developed by closing pores (sealing treatment) generated in a plating film performed as a surface treatment of a neodymium magnet. It is intended to provide a highly corrosion-resistant Nd-Fe-B magnet for the purpose of significantly improving the corrosion resistance over conventional products by a low-cost treatment without changing the Nd-Fe-B magnet.

[0007]

[Means for Solving the Problems]

 In order to achieve the above object, a highly corrosion-resistant Nd-Fe-B magnet according to the present invention is configured as follows. That is, the method is characterized in that the fine pores formed in the plating film on the surface of the molded and sintered Nd-Fe-B magnet are sealed with an inorganic sealing agent. Preferably, the inorganic sealing agent is mainly composed of an alkali metal silicate.

[0008]

[Action]

 With the above configuration, the pores remaining in the coating of the plating layer are sealed with the sealing agent (sealing treatment). As a result, oxygen contact with the magnetic material via the pores is cut off, and the generation of rust is suppressed. In addition, the plating solution remaining in the pores evaporates due to the reduced pressure treatment during the sealing process, eliminating corrosion caused by the remaining plating solution and suppressing deterioration of magnetic properties. Become.

As the sealing agent, for example, an impregnating agent is used, and an inorganic impregnating agent (for example, water glass) containing an alkali metal silicate as a main component or an impregnating sealing agent made of an anaerobic resin is used. By using it after the impregnation treatment, the durability such as heat resistance and chemical resistance is improved. Further, by sealing the holes, which is the main feature of the present invention, the contact between the magnetic material and the air through the holes is prevented to prevent the generation of rust.

[0010]

[Embodiment of the invention]

 Next, a specific embodiment of the above configuration will be described with reference to the drawings. FIG. 1 is an enlarged cross-sectional perspective view showing a surface of a plating layer before a sealing process, which is a characteristic portion of the present embodiment, and FIG. 2 is a plating layer after a sealing process, which is a characteristic portion of the present embodiment. FIG. 2 is a cross-sectional perspective view showing the surface of FIG.

The magnetic body 1 is formed by dissolving Nd (nejiom), Fe (iron), and B (boron), which are rare earth elements, at respective ratios to form an alloy ingot (ingot). This alloy lump is pulverized (for example, using a jet mill) to form a fine powder, and the fine powder is press-formed, sintered, and shaped into a predetermined shape. Next, the magnetic body 1 is immersed in a plating solution of an electrolytic solution to perform plating, and a surface film is formed by the plating layer 2 (for example, a thickness of 30 μm). The plating layer 2 has a three-layer structure of Ni-Cu-Ni, similarly to the conventional treatment. On the surface of the plating layer 2, there are a large number of holes 3, 3, 3,..., And the size is several μm to several tens μm. The bottom of the hole 3 reaches the magnetic material 1.

Finally, by performing a sealing treatment, the impregnating agent 4 used as one of the sealing agents is filled in the holes 3 to close the openings. The impregnating agent 4 used here is preferably an inorganic one containing an alkali metal silicate as a main component. For example, in this example, favorable results were obtained by using a cold-setting impregnating liquid for a sintered alloy (trade name “Mazda Seal Z”, a registered trademark of Mazda Corporation).

The sealing method in this embodiment employs a partial pressure impregnation method, and includes an impregnation tank and a tank for storing an impregnating agent (not shown). The impregnating agent is not stored. The plated magnetic body 1 is placed in the impregnating tank, the pressure is reduced, and the gas and moisture in the holes 3 are evaporated and removed. Then, the impregnating tank is stored in the impregnating tank. The impregnating agent is allowed to flow, and the pressure in the impregnation tank is returned to normal pressure. Then, the impregnating agent is pressurized by pressurizing with an air pressure of about 0.5 to 0.6 MPa, and then the inside of the impregnation tank is returned to normal pressure, the magnetic body 1 is taken out of the impregnation tank, and the surface is washed with water. It employs the process of curing the impregnating agent by air drying for about one day.

[0014]

【effect】

 Since the present invention is configured as described above, it is possible to obtain a Nd-Fe-B magnet that is more resistant to rust and stronger than conventional products by a less expensive process without changing the conventional plating equipment. Was. As a result, it is possible to maintain the superiority of the neodymium magnet, which is relatively inexpensive over the samakoba magnet, and to dramatically increase the service life, thereby reducing the cost. And can make a useful contribution to the industrial field.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional perspective view showing a surface of a plating layer before a sealing process, which is a characteristic part of the present embodiment.

FIG. 2 is an enlarged cross-sectional perspective view showing a surface of a plating layer after a sealing process, which is a characteristic part of the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic body 2 Plating layer 3 Void 4 Impregnating agent (sealing agent)

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[Procedure amendment]

[Submission date] July 31, 2000 (2007.3.
1)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2

Claims (2)

[Utility model registration claims] 1. A highly corrosion-resistant Nd-Fe, wherein fine pores formed in a plating film on the surface of a molded and sintered Nd-Fe-B magnet are sealed with an inorganic sealing agent. -B magnet. 2. The highly corrosion-resistant Nd—Fe—B magnet according to claim 1, wherein the inorganic sealing agent contains an alkali metal silicate as a main component.