JPH06236808A - Composite magnetic material and its manufacture - Google Patents

Abstract

PURPOSE:To develop a composite magnetic material wherein its resistivity is large and its saturation magnetic flux density and its high-frequency characteristic are both excellent. CONSTITUTION:An oxide magnetic material is featured by bonding, via a binder, a mixture of 65 to 98wt.% of an iron alloy powder of one kind or two kinds selected from Sendust whose particle size is at 200mum or smaller and which is provided with an oxide film in a thickness of 0.003 to 0.04mum on the surface and an Fe-Si-based alloy and 2 to 35wt.% of a highly compressive soft-magnetic metal powder at a particle size of 200mum or smaller or a mixture of 65 to 98wt.% of an iron alloy powder, 1 to 30wt.% of a highly compressive soft- magnetic metal powder and 1 to 15wt.% of a soft ferrite powder at an average particle size of 5mum or smaller. In its manufacturing method, an organic binder at 0.3 to 1.0wt.% and/or an inorganic binder at 0.2 to 1.5wt.% are added to, and mixed with, the above-mentioned mixture, this mixture is pressurized and molded under a pressure of 5 to 20t/cm<2>, and the mixture is heat-treated at a temperature of 120 to 200 deg.C in the case of only the organic binder and at a temperature of 600 to 800oC in a case where the inorganic binder is contained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite magnetic material suitable for use in electronic parts such as magnetic heads, transformer cores for switching power supplies and smooth chokes, and a method for producing the same, and more particularly to iron alloy powder, soft magnetic powder and This is a proposal for a composite dust core material obtained by binding a mixture with soft ferrite powder via a binder and a method for producing the same.

[0002]

2. Description of the Related Art Electronic components such as magnetic heads, transformer cores for switching power supplies, smooth chokes, etc.
There is a trend toward higher performance, and as a result, higher performance of the materials used for these parts has also been required. As such a material, either an iron alloy-based metal magnetic material such as sendust or silicon steel (Si-4 to 7% Fe) or an oxide magnetic material such as soft ferrite has been conventionally used. . Among such materials, the above metal magnetic material has poor compressibility at the time of molding due to the high hardness of its powder, and as a result, the density of the obtained molded body is low and the magnetic properties are poor. there were.

On the other hand, conventionally, there has been proposed a technique for forming a high density composite magnetic material by compounding this metal magnetic material with a highly compressible powder (see Japanese Patent Laid-Open No. 176446/1988). This conventional high-density composite magnetic material has good adhesion between the iron alloy powder such as Sendust and silicon steel and the highly compressible powder, and it can be expected that the compact density is improved.

However, in this metallic magnetic material, the specific resistance of the composite material is small due to the good adhesion between the iron alloy powder and the highly compressible powder, and as a result, the eddy current loss increases and the magnetic characteristics deteriorate. I had a problem.

Generally, the above-mentioned metallic magnetic material has a drawback that the saturation magnetic flux density is high, but the high frequency characteristics are poor.
The oxide magnetic material exhibits excellent magnetic characteristics in a high frequency region as compared with the metal magnetic material, but has a drawback that the saturation magnetic flux density is low.

Therefore, by compounding the metal magnetic material and the oxide magnetic material, it is possible to develop a material satisfying the respective properties without sacrificing the other properties. It can greatly contribute to miniaturization and high performance of such parts, and its application range is extremely wide, and it is promising.

On the other hand, conventionally, various proposals have been made for such a combination. For example, in Japanese Unexamined Patent Publication No. 56-38402, a wet ferrite manufacturing method is used to coat a metal magnetic powder (such as permalloy) with an oxide magnetic material (such as ferrite), and then heat treatment,
Methods for forming, sintering, and HIP processing have been proposed. Japanese Patent Laid-Open No. 58-164753 proposes a composite magnetic material in which an oxide magnetic material (such as ferrite) and Fe-Ni powder are composited. According to Japanese Patent Publication No. 62-38411, 1 to 10% of B ₂ O ₃ is added to a mixture of a magnetic metal powder (such as iron alloy powder) and an oxide magnetic material (such as ferrite powder), and 600 to 800 ° C. A method for producing a cermet-type ferrite that is fired at a temperature has been proposed.

However, the above-mentioned respective prior arts still have the following problems. That is, in the technique disclosed in Japanese Patent Laid-Open No. 56-38402, even if the surface of the metal magnetic powder is coated with ferrite, the density after molding is not sufficient, so sintering at 1100 to 1280 ° C is essential. Was said. Therefore, even if the surface of the metal magnetic powder is coated with ferrite, there is a problem that the metal reacts with the ferrite at the interface to deteriorate the magnetic characteristics. Moreover, in this method, since the surface of the metal magnetic powder is coated with ferrite by the wet ferrite method and the HIP treatment is further performed, there is a problem in terms of high manufacturing cost and economical efficiency.

In the technique disclosed in Japanese Patent Application Laid-Open No. 58-164753, the metal and the ferrite react with each other in the heat treatment step (950 ° C.) because the surface state of the metal magnetic powder is in an active state without any improvement. However, there are problems that the magnetic properties are deteriorated and that the density after molding is low because a highly compressible powder is not used.

In the technique disclosed in Japanese Examined Patent Publication No. 62-38411, the metal and the ferrite react with each other in the heat treatment step (600 to 800 ° C.) because the surface state of the magnetic metal powder is not improved and is in the active state. The magnetic properties are deteriorated, the binder (B ₂ O ₃ ) is not sufficiently bonded, the deterioration of the magnetic properties due to the eddy current in the metal part cannot be prevented, and the high compressibility powder is not used. Therefore, there is a problem that the density after molding is low.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned problems of the prior art and to develop a composite magnetic material having a large specific resistance and excellent saturation magnetic flux density and high frequency characteristics. Thus, a material having excellent magnetic properties, which is preferably used as a magnetic head, a transformer core for a switching power supply, or a smooth choke, is to be provided.

[0012]

As a result of earnest research to achieve the above object, the inventor has shown that a metal magnetic material can be obtained by combining a surface-oxidized metal magnetic material with highly compressible powder and soft ferrite. We have established a composite technology of magnetic materials that has a high saturation magnetic flux density as it is, but on the other hand, can effectively prevent the deterioration of magnetic characteristics due to eddy currents that occur in the metal part, which is a defect. The present invention having a configuration has been conceived.

That is, according to the present invention, one or two kinds selected from sendust and Fe--Si alloys having a grain size of 200 μm or less and having an oxide film with a thickness of 0.003 μm to 0.04 μm on the surface thereof. Iron alloy powder 65-98wt%, particle size 200μm
A mixture with the following highly compressible soft magnetic metal powder 2-35 wt%,
The composite magnetic material is characterized by being bonded via a binder (first invention), and the present invention also has a particle size of 20
65 to 98 wt% of one or two iron alloy powders selected from Sendust and Fe-Si alloys having an oxide film with a thickness of 0 to 0 μm and a thickness of 0.003 to 0.04 μm, and a particle size Highly compressible soft magnetic metal powder with a particle size of 200 μm or less 1-30 wt% and soft ferrite powder with an average particle size of 5 μm or less 1-15 wt%
It is a composite magnetic material characterized by being formed by binding a mixture of and with a binder (the second invention). Then, the production method of the present invention, a mixture of the iron alloy powder and the highly compressible soft magnetic metal powder and the soft ferrite powder, 0.3 ~ 1.0 wt% of an organic binder or 0.2 ~
At least one binder of 1.5 wt% inorganic binder is added and mixed, and then 5 to 20 t / cm
Pressure molding at a pressure of ² and then at a temperature of 120 to 200 ℃ in the case of organic binder only, and 600 to 800 ℃ in the case of inorganic binder alone or a mixture of this and organic binder. It is characterized in that it is heat-treated at the temperature of (3rd invention).

[0014]

The composite magnetic material of the present invention is characterized in that the surface-oxidized iron alloy powder is used, and the iron alloy powder and the highly compressible soft magnetic metal powder and soft ferrite powder are used with an organic and / or inorganic binder. The point is that they are fixedly bonded. With such a structure, it is possible to easily and surely obtain a composite magnetic material having a large specific resistance and excellent saturation magnetic flux density and high frequency characteristics.

As the iron alloy powder used for producing the composite magnetic material according to the present invention, a powder having a particle diameter of 200 μm or less, which is produced by crushing an ingot or atomizing method is used. Here, the reason why the grain size of the iron alloy powder is limited to 200 μm or less is that the eddy current loss in the metal powder portion becomes too large when the particle size exceeds 200 μm. Especially, it is desirable to use the powder obtained by the gas atomizing method or the water atomizing method. The reason for this is that the powder obtained by the atomization method has a shape close to a sphere, and it tends to be a high-density body when it is combined with a highly compressible soft magnetic metal powder, and there is no mechanical strain due to crushing, so at high temperature. This is because the heat treatment of is not required.

As such iron alloy powder, sendust (Fe-Si-Al alloy, Si: 4 to 13 wt%, excellent in soft magnetic properties,
Al: 4 to 7 wt%, balance Fe) or Fe-Si alloy (Si: 3 to
7 wt%, balance Fe) is preferably used. The reason is that magnetic properties such as magnetic permeability are excellent in this composition range.

As the iron alloy powder, powder whose surface is oxidized is used in order to maintain the insulating property between particles. The thickness of the oxide film (insulating film) on the surface of this atomized iron alloy powder is 0.003 μm.
~ 0.04 μm. The reason for limiting the thickness is that if the thickness of the oxide film exceeds 0.04 μm, the non-magnetic portion increases and the magnetic properties of the iron alloy powder deteriorate. On the other hand, if the thickness of the oxide film is less than 0.003 μm, there is no insulating effect, the specific resistance of the iron alloy powder surface decreases, and the magnetic characteristics of the iron-based alloy powder deteriorate due to eddy current loss.

The blending amount of the iron alloy powder having such an oxide film is 65 to 98 wt% in the inner frame amount with respect to the composite magnetic material. The reason for this is that if the iron alloy powder exceeds 98 wt%, the ratio of the iron alloy powder is too large, so the voids caused by the iron alloy powder with relatively large particles are filled with the highly compressible soft magnetic metal powder or soft ferrite powder. This is because, as a result, it is difficult to obtain a good insulating effect, and the improvement in density cannot be expected so much. On the other hand, if the iron alloy powder is less than 65 wt%, the ratio of the iron alloy powder in the composite magnetic material decreases and the magnetic properties deteriorate.

Next, as the highly compressible soft magnetic metal powder used for producing the composite magnetic material according to the present invention, it is preferable to use a metal that is as soft as possible in consideration of the compressibility at the time of molding. Use iron powder or Fe-3% Si powder.

This highly compressible soft magnetic metal powder has an average particle size of
Use those with a thickness of 200 μm or less. The reason for this is that if the average particle size of the highly compressible soft magnetic metal powder exceeds 200 μm, the eddy current loss becomes too large and the magnetic properties deteriorate.

The compounding amount of this highly compressible soft magnetic metal powder is 1 or 2 to 35 wt% in the inner frame amount with respect to the composite magnetic material. The reason is that highly compressible soft magnetic metal powder is 1 or 2 wt.
%, The effect of improving the compressibility is poor. On the other hand, when the highly compressible soft magnetic metal powder exceeds 35 wt%, the ratio of the iron alloy powder in the composite magnetic material decreases and the magnetic properties deteriorate. is there.

Next, in order to further reduce the eddy current loss of the above-mentioned iron alloy powder according to the first aspect of the invention-highly compressible soft magnetic powder, the eddy current loss is further compounded with soft ferrite. It is necessary to make it.

Here, as the soft ferrite powder used in the production of the composite magnetic material composed of the iron alloy powder according to the present invention, the highly compressible soft magnetic powder, and the soft ferrite powder, which are three kinds of green compacts, An average particle size of 5 μm or less is used. The reason is that the average particle size of the soft ferrite powder is 5
If it exceeds μm, the effect of dispersing the metal powder is not sufficient, so that the insulating effect is deteriorated and the density cannot be expected to be improved so much. That is, such soft ferrite powder has relatively large particles (200 μm or less)
By penetrating into the void due to the iron alloy powder, the density is improved, a continuous magnetic path is formed, and the magnetic characteristics are improved. On the other hand, in the case of the conventional magnetic material consisting only of iron alloy powder, the density is not increased due to the generation of voids due to the large particle size (200 μm or less), and it is difficult to form a continuous magnetic path. The magnetic properties are not improved.

The content of the soft ferrite powder is 1 to 15 wt% in the inner frame amount with respect to the composite magnetic material. The reason for this is that if the soft ferrite powder is less than 1 wt%, the proportion of the soft ferrite powder is too small to fill the voids in the iron alloy powder, and as a result, it is difficult to obtain a good insulating effect and the density is improved. Because I can not expect much. On the other hand, if the soft ferrite powder exceeds 15 wt%, the ratio of the fine powder in the composite magnetic powder increases, and as a result, cracking tends to occur during molding and improvement in density cannot be expected.

Next, a method for manufacturing the composite magnetic material of the present invention will be described. First, one or two kinds of iron alloy powder 65-98 wt% selected from Sendust and Fe-Si alloys having a particle size of 200 μm or less and an oxide film having a thickness of 0.003 μm to 0.04 μm on the surface. And 2 to 35 wt% of highly compressible soft magnetic metal powder having a particle size of 200 μm or less and soft ferrite powder having an average particle size of 5 μm or less are mixed. Then add to this mixture an organic binder such as an epoxy resin 0.3-1.
0 wt% and / or inorganic binder such as water glass
0.2-1.5 wt% and lubricant such as zinc stearate 0.2
˜0.7 wt%, and then pressure-molded at a pressure of 5-20 t / cm ² to obtain a predetermined molded body.

Here, the reason for limiting the addition amounts of the organic binder, the inorganic binder and the lubricant is that the shape retaining force and mechanical strength of the molded product, the insulating effect between particles in the product after heat treatment, and the effect of the lubricating force. However, it does not appear if the value is less than each of the lower limit values. On the other hand, the upper limit of the amount of the organic binder, the inorganic binder and the lubricant added indicates a critical point at which the magnetic properties are deteriorated when the upper limit is exceeded. In addition, the pressure range of pressure molding is 5 to 20
The reason for limiting to t / cm ² is that if it is less than 5 t / cm ² , the density of the molded body becomes too low, and if it exceeds 20 t / cm ² , deterioration of the mold becomes severe.

Next, the molded body obtained as described above is used at a temperature of 120 to 200 ° C. in the case of only the organic binder, and in the range of 600 to 800 in the case of containing the inorganic binder.
By heat-treating at a temperature of ° C, the iron alloy powder and the soft ferrite powder are firmly bonded to each other to obtain a composite magnetic material. When using an organic binder, the heat treatment temperature should be 120-
The reason for 200 ° C is that in this temperature range, the reaction between alloy particles or between alloy and ferrite can be made negligibly small, and as a result, mechanical strength and insulation between particles should be sufficiently maintained. Because you can

On the other hand, only the inorganic binder, or
In the case of a mixed binder of this and an organic binder, if the temperature is lower than 600 ° C, the reaction at the interface does not sufficiently occur, and
If the temperature exceeds ℃, unnecessary reactions will occur and the magnetic properties will deteriorate, so the heat treatment temperature should be set to 600-800 ℃. By setting the temperature within this temperature range, the coupling between the alloy particles or between the alloy and the ferrite can be more firmly performed, and the excess reaction can be minimized, and the magnetic properties such as magnetic permeability can be further improved. Can be made.

As described above, according to the present invention, the high saturation magnetic flux density exhibited by the metallic magnetic material is provided as it is. On the other hand, it is possible to effectively prevent the deterioration of the magnetic characteristics due to the eddy current generated in the metallic portion, which is a defect. Can be prevented.

[0030]

EXAMPLES Examples of the present invention will be shown below in comparison with comparative examples. (1) Under the conditions shown in Tables 1 and 2, Si: 9.5 wt%, Al:
"Sendust powder" consisting of 5.5 wt% and the balance Fe, or S
Fe-Si alloy powder containing i: 6.5 wt% was prepared by a water atomizing method and a gas atomizing method. Obtained by the water atomizing method and the gas atomizing method, a part of the powder having various particle diameters is sieved with a mesh, 200
Separated into powders of less than μm and powders of more than 200 μm. (2) Part of the various powders obtained in (1) above was oxidized at various temperatures, times, and atmospheres as shown in Tables 1 and 2 to obtain surface-oxidized alloy powder. The thickness of each oxide film was calculated from the increase in weight assuming that alumina or silica was present in the surface layer. (3) As the highly compressible soft magnetic powder, pure iron powder or Fe-3% Si powder obtained by the water atomizing method and the gas atomizing method was sieved to have a predetermined particle size. (4) On the other hand, MnZn ferrite sintered body (ZnO 13.5 mol%, Fe
₂ O ₃ 53.0 mol%, Mn 33.5 mol%, CaO 0.15 wt%, SiO ₂
0.015 wt%) or NiZn ferrite was crushed to produce ferrite powders having different average particle sizes. (5) The alloy powder or surface-oxidized alloy powder thus obtained was mixed with the highly compressible soft magnetic powder and the ferrite powder at various ratios to prepare a mixed powder. (6) Next, add a specified amount of epoxy resin and 0.3 wt% zinc stearate, which is a lubricant, to these mixed powders, and then press-mold at various pressures and then at 10 A composite magnetic material was produced by heat treatment for minutes. On the other hand, for some types of mixed powder, inorganic binder (water glass) is added in addition to organic binder (epoxy resin), and pressure molding is performed at 600-800 ° C.
A composite magnetic material was produced by heat treatment at the temperature of.

Table 3 shows the measurement results of the magnetic properties and the like of each of the examples and comparative examples. As is clear from the results shown in Table 3, it was confirmed that the effect of improving the magnetic characteristics shown in the conformity example of the present invention was clear and the target characteristics were satisfied. In addition, in general, the target characteristic value of the required magnetic characteristics is: permeability: 80 or more, quality factor: 60 or more,
Saturation magnetic flux density: 0.65 T or more, and all the examples of the present invention exceeded such target values.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

As described above, according to the present invention, a composite magnetic material having a large specific resistance and excellent saturation magnetic flux density and high frequency characteristics can be easily and reliably obtained. As a result, the characteristics of the parts obtained when the composite magnetic material of the present invention is used for a magnetic head, a transformer core for a switching power supply, a smooth choke, etc. are remarkably improved.

Claims (3)

[Claims] 1. A particle size of 200 μm or less and a thickness of 0.
65 to 98 wt% of one or two iron alloy powders selected from Sendust and Fe-Si alloys having an oxide film of 003 μm to 0.04 μm and highly compressible soft magnetic metal powder with a particle size of 200 μm or less A composite magnetic material, which is obtained by binding a mixture of 2 to 35 wt% with a binder. 2. A particle size of 200 μm or less and a thickness of 0.
65 to 98 wt% of one or two iron alloy powders selected from Sendust and Fe-Si alloys having an oxide film of 003 μm to 0.04 μm and highly compressible soft magnetic metal powder with a particle size of 200 μm or less A composite magnetic material comprising a mixture of 1 to 30 wt% and 1 to 15 wt% of soft ferrite powder having an average particle size of 5 μm or less, which is bound via a binder. 3. The mixture according to claim 1 or 2, wherein:
3 to 1.0 wt% organic binder or 0.2 to 1.5 wt%
At least one or more of the inorganic binders described above are added and mixed, and then pressure-molded at a pressure of 5 to ²⁰ t / cm ² , and thereafter, in the case of only the organic binder, at a temperature of 120 to 200 ° C., Also, only inorganic binder,
Alternatively, in the case of a mixed binder of this and an organic binder, a heat treatment is performed at a temperature of 600 to 800 ° C., which is a method for producing a composite magnetic material.