JP4825995B2 - Lightweight magnetic material and manufacturing method thereof - Google Patents

Description

The present invention relates to a magnesium material having permanent magnetism used as an electronic material and a method for producing the same.

Permanent magnetic materials are used in a very wide range of fields such as communication equipment, rotating machines, various acoustic equipment, and medical equipment. As these permanent magnetic materials, metal magnets, ferrite magnets, alnico magnets, etc. have been used for a long time, but in recent years, they have higher magnetic strengths such as rare earth cobalt, rare earth iron, especially niobium-iron-boron. Performance magnetic materials have been invented, and electronic products have become increasingly smaller in size.

Since these high-performance magnetic materials are often produced by a powder metallurgy method, a powder firing method or the like, they are obtained in a fine powder form. For this reason, so-called bonded magnets uniformly dispersed in resin or rubber have been developed. However, these bonded magnets have low heat resistance and mechanical strength, and their application fields are limited. On the other hand, heat resistance and mechanical strength have been improved by making these magnetic materials into bulk magnets, but this requires high-temperature and advanced processing methods such as hot pressing and roll rolling. There is a situation where a simpler processing method is required.

There are several attempts to give magnetism by mixing magnetic materials with non-ferrous metals that do not have magnetism, but in the case of magnesium materials this is a very active metal, and with magnetic materials such as iron specific gravity and melting temperature It is difficult to make composites due to the large difference between the materials, and even if magnetic materials such as magnesium and iron are combined, there are defects such as the formation of local batteries due to the difference in ionization tendency and the significant promotion of corrosion. There are few examples that have been investigated. Patent Document 1 suggests that a slight amount of magnesium fine powder and iron or an alloy powder containing iron are mechanically uniformly mixed to form an alloy. This method requires mixing and stirring magnesium fine powder for 50 to 100 hours for a long time. Even if it is performed in an inert gas, there is always a risk of dust explosion, and the difference in ionization tendency has not been eliminated. It is a material with the risk of rapid corrosion.

Japanese Patent Laid-Open No. 9-302425

The present invention forms a high-performance magnetic material layer on the surface layer of magnesium or magnesium alloy, which is a lightweight non-ferrous metal, imparts magnetism to a magnesium material that does not inherently have magnetism, and is lightweight magnetism with excellent mechanical strength and heat resistance. The purpose is to provide materials.

The present invention relates to a fine powder magnetic material having an average particle diameter of 50 μm or less and / or a magnetic material precursor in an ion, colloid or sol-gel state inside the pores of a porous coating layer formed on the surface of magnesium or a magnesium alloy by anodization. the is magnetized by magnesium or magnesium alloy their preparation obtained by Hama charge.

The average pore diameter of the porous coating layer formed on the surface of magnesium or magnesium alloy is 50 nm to 80 μm, and the thickness of the layer is 1 to 100 μm, which can be formed by anodic oxidation. These pores are arranged in such a manner that large pores exist in a portion closer to the surface in the coating layer, and there are many slightly smaller pores when several to several tens of micrometers below the surface.

In the present invention, the magnetic material or precursor thereof filled in the porous coating layer portion on the surface of the substrate is a ferrite magnet, alnico magnet, rare earth cobalt magnet, rare earth iron magnet, Heusler alloy or the like, or iron, cobalt, nickel Such as a fine powder having an average particle size of 50 μm or less or a precursor thereof in the form of ions, colloids, or sol-gel, such as Fe—Co—Ni—Al, Fe—Cr— Co-based, Sm-Co-based, Nb-Fe-B-based magnets and the like are preferable. Further, a Heusler alloy known as a ferromagnetic metal crystal, for example, a fine powder of Mn—Al—Cu alloy, Mn—Al— (Ni, Co, Fe) —Cu alloy, or the like is preferably used.

The anodic oxidation treatment for forming the porous coating layer of the present invention can be performed by any of the spark discharge type and non-spark discharge type oxidation methods, but the spark discharge type anodic oxidation method capable of forming a coating layer having a larger average pore diameter is preferred. . This is a current density of 0.8 or more in an electrolytic solution containing 0.2 to 7 mol / L of an alkali or alkaline earth metal phosphate, borate, hydroxide, silicate, or silicofluoride. It is preferable to carry out spark discharge at 5 to 5 A / dec square meter and a voltage of 25 V or higher. The treatment temperature is particularly preferably a bath temperature of -5 to 25 ° C.

If necessary, a film-forming stabilizer can be added to the electrolytic solution in the range of 0.01 to 5 mol / L. As the stabilizer, an inorganic substance such as a fluoride salt, a bifluoride salt, a silicofluoride salt, or a mineral salt, or an organic compound containing an alcohol, a carboxyl group, or a sulfone group is used. These stabilizers can be used alone or in combination. In particular, it is preferable to use a combination of an inorganic compound and an organic compound because liquid management becomes easy.

The porous coating layer formed on the surface of the magnesium substrate by anodic oxidation has one or two pore layers having an average pore diameter of 1 to 80 μm on the surface layer and a pore layer having an average particle diameter of 50 nm to 5 μm below it. It has a multilayer structure composed of a combination and a barrier layer, and the thickness of the coating layer is 1 to 100 μm. This coating layer is made of a mixture of magnesium oxide with a spinel structure and magnesium hydroxide, and does not form a local battery by contact with a magnetic material, and does not promote surface corrosion.

As a method for filling magnetic fine particles into the pores of the porous coating layer on the surface of the magnesium substrate, atmospheric pressure impregnation, pressure impregnation, sol-gel method, electrophoresis, immersion ultrasonic impregnation method and the like are used. As a specific impregnation method, a magnesium alloy material in which a porous anodic oxide film is formed is placed in a vacuum vessel, and after the pressure inside is reduced, a suspension of magnetic material in a fine powder of 50 μm or less is introduced. By pressurizing, the fine pores of the material surface layer can be filled. This method may be repeated to increase the filling rate. Alternatively, a colloid solution of a magnetic material precursor that has not been magnetized may be filled in the same manner.

The magnetic material filled in the porous coating layer of the material can be used for various purposes as it is, but by demagnetizing it once and then magnetizing it, the magnetic material is aligned in the same direction, increasing the anisotropy and increasing the magnetic force. This is preferable. As a demagnetizing method, alternating current is 1 to 5 kV. As a magnetization method, 1 to 5 kv is applied for 1 mS to 60 seconds.

Since the magnetic material obtained in this way is lightweight and has high mechanical strength, it is used for electromagnetic generators such as small generators for lamps such as bicycles and motorcycles. It can also be used as a lightweight rotation sensor used for detecting the number of rotations. It is also used for small motors used in a wide variety of products such as toys, cameras, electric razors, toothbrushes, tape recorders, telephones, and micromachines. In addition, there is a possibility that it can be used when it is necessary to reduce the weight in all fields that use magnets such as electromagnets, transformers, brakes, and copying machines.

Furthermore, when the magnetic material of the present invention is formed into a thin plate shape, both surface layers are magnetized, and there is a magnesium metal layer that is not magnetized in the inner layer, so there is a magnetoresistance effect in which the resistance changes depending on the applied magnetic field. Therefore, it can be used as a magnetoresistive element such as a magnetic field sensor or a magnetic head. Furthermore, as a lightweight magnetic shielding material, it is excellent in shielding of magnetic energy especially in the low frequency region, which is difficult to shield with ordinary metal conductors. The effect to prevent can also be demonstrated.

Magnesium alloy material obtained by the method of the present invention is a lightweight material obtained by magnetizing a material that does not have magnetism, heat resistance, high mechanical strength, and nonflammability. Can be spread.

Next, the present invention will be specifically described with reference to examples. In the examples, “%” means “% by weight” unless otherwise specified.

Using magnesium alloy AZ31B rolled material having a plate thickness of 1 mm and 70 × 150 mm, after degreasing and acid treatment, NaOH: 3 ± 0.05 mol / liter, Na ₂ HPO ₄ ; 0.3 ± 0.01 mol / liter, As film additives, Na ₂ SiO ₃ ; 0.05 ± 0.005 mol / liter and sodium tartrate; 0.1 ± 0.05 mol / liter, KF; 0.2 ± 0.01 mol / liter were added. Spark discharge type anodic oxidation treatment was performed with the electrolyte at a liquid temperature of 26 ± 2 ° C., 50 Hz alternating current, a current density of 2 ± 0.5 A / square decimeter, and a spark discharge start voltage of about 50 V. When the cross section of this film is observed with an electron microscope, among the film thickness of about 20 μm, pores having an average pore diameter of 10 to 20 μm are obtained from the surface side to about 16 μm, and the film thickness on the substrate side is about 4 μm. Micropores of 3 μm or less were confirmed. This sample was subjected to a magnetic loading treatment. Nickel sulfate 40 g / L, magnesium sulfate 15 g / L, boric acid 20 g / L, ammonium sulfate 50 g / L, triammonium citrate 5 g / L, aqueous ammonia 1.5 ml / L, PH 5.5 Then, AC electrolysis was performed at a bath temperature of 23 ° C. and a voltage of 15 V for 10 minutes. The color was dark bronze. When the magnetic flux density of this work was measured with a Tessler meter, it was 7 × 10 ⁻² T.

(Comparative Example 1)
When electrolysis was performed in the same manner as in Example 1 and the magnetization supporting process was not performed, the magnetic flux density was 0 T.

(Comparative Example 2)
Electrolysis was carried out in the same manner as in Example 1 and immersed in the magnetization supporting treatment solution without performing electrolysis. When measured in the same manner as in Example 1, it was 7 × 10 ⁻⁴ T.

The material used and the anodic oxide film treatment were the same as in Example 1, and after carrying the magnetic material at 230 ° C. for 60 minutes, the magnetic flux density was measured as in Example 1. As a result, it was 9 × 10 ⁻² T.

The materials used and the anodized film treatment were the same as in Example 1, and the anodized product was placed in a SUS vacuum container as a method for supporting and fixing, reduced to 4 mmHg, held for 20 minutes, and after holding, the average particle size It was immersed in an acetone dispersion of samarium cobalt of 5 microns or less, poured until the product in the container was completely immersed, pressurized at 0.4 MPa, taken out after 20 minutes, and dried. This was demagnetized at 3 KV and further magnetized at 2 KV for 2 seconds. The magnetic pattern of the workpiece was confirmed with a magnetic sheet. Further, when the magnetic flux density was measured in the same manner as in Example 1, it was 1.5 × 10 ⁻¹ T.

After the anodic oxidation treatment of Example 1, as a magnetic supporting treatment, it was immersed in an acetone dispersion of samarium cobalt having an average particle size of 5 microns or less, subjected to ultrasonic vibration at 25 KHz for 10 minutes, dried, and then the same as in Example 3. Went to. As a result, the magnetic flux density was 1.2 × 10 ⁻¹ T.

After degreasing and acid treatment using the material of Example 1, potassium hydroxide 2 ± 0.05 mol / liter, sodium metasilicate 0.05 ± 0.005 mol / liter as a film forming stabilizer, diethylene glycol 0. Non-spark discharge type anodizing electrolysis was performed for 30 minutes at a liquid temperature of 68 ± 2 ° C., a current density of 2 ± 0.5 A / square decimeter voltage of 4 to 8 V, with an electrolyte added with 1 ± 0.05 mol / liter. . When the method of Example 1 was used as the magnetic carrying treatment, the magnetic flux density was 5 × 10 ⁻² T.

The schematic diagram when a magnetic material enters into the pores of the anodized film obtained in Example 1 is shown.

Explanation of symbols

1. Anodized film 2. porous layer Barrier layer 4. magnesium
5). Magnetic substance

Claims (4)

A combination of a magnesium oxide spinel structure and magnesium hydroxide formed on the surface by spark discharge type anodization, and a combination of a pore layer having an average pore diameter of 1 to 80 μm and a pore layer having an average pore diameter of 50 nm to 5 μm below the surface layer portion Ri average particle diameter hole inside of the porous coating layer of a multilayer structure that consists from the barrier layer is Na filled 50μm or less fine powder magnetic material and / or ions, the magnetic material precursor colloidal or sol-gel state, tesla · Magnesium or magnesium alloy material magnetized to a magnetic flux density of 0.9 × 10 ⁻¹ T or more measured with a meter . The magnetic material is selected from metal magnets, ferrite magnets, alnico magnets, rare earth cobalt magnets, rare earth iron magnets, Heusler alloys, or fine powders having an average particle size selected from iron, nickel, and cobalt based particles of 50 μm or less. The magnetized magnesium or magnesium alloy material of claim 1. The magnesium or the substrate surface by a spark discharge anodized in an aqueous electrolyte solution containing the alloy base as a main component an alkali metal or alkaline earth consists spinel structure and magnesium hydroxide magnesium oxide, the surface layer A porous film having a thickness of 1 to 100 μm having a multilayer structure composed of a barrier layer and a combination of a pore layer having an average pore diameter of 1 to 80 μm and a pore layer having an average pore diameter of 50 nm to 5 μm below and a barrier layer is formed on this portion. Fill the part with fine powder magnetic material with an average particle size of 50μm or less and / or its ion, colloid or sol-gel magnetic material precursor by atmospheric pressure impregnation, pressure impregnation, sol-gel method, electrophoresis or immersion ultrasonic impregnation method is magnetized due to, or once consists of magnetized after demagnetized after filling, the magnetic flux density measured in tesla meter .9 × preparation of the magnetized by magnesium or magnesium alloy above 10-1T. The method for producing a magnetized magnesium or magnesium alloy material according to claim 3 , wherein the magnetic material is filled until the porosity of the porous portion is 90% or less.

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