JPH05258934A - Magnetic material and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To provide a magnetic material which has a high saturated magnetic flux density and whose effective permeability hardly deteriorates by a method wherein a thin layer of high proper resistance material is formed on the surface of Fe particles and then the particles thus processed are pressure-molded to be sintered. CONSTITUTION:A thin layer 3 of high proper resistance colloidal material is formed on the surface of Fe particles 1 by infiltrating method, etc., of a liquid such as colloidal silica sol, etc. Next, the particles thus processed are pressure- molded to be sintered. At this time, pressurized particles are contained in a furnace at the temperature exceeding at least 1/2 of the melting temperature of Fe so that a high proper resistance material may be mutually diffused into one another and mutually adhere to one another by heating step. Thus, magnetic core suffering a small eddy current loss can be manufactured. Furthermore, high saturated magnetic flux density in small counter magnetic field action, having a high effective permeability and an Fe density can be assured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soft magnetic material containing metallic iron as a component and a method for producing the same.

[0002]

2. Description of the Related Art Conventional soft magnetic materials containing iron have low specific resistance and belong to the category of so-called "metals". Therefore, when they are used as magnetic cores for transformers and inductors, eddy current loss occurs. As a result, the effective magnetic permeability is reduced, so that it was rolled into a thin plate and used as a laminated magnetic core.

[0003]

Therefore, in the laminated magnetic core, there is a limit to the thinness in maintaining the mechanical strength no matter how thinly rolled, so no matter how the laminated magnetic core is considered, the eddy current loss is still caused. Inevitably, the frequency that can be used is as low as 10 kHz or less, which limits its use.

The present invention is intended to solve the above-mentioned problems, and the effective magnetic permeability is not significantly reduced even at a frequency of 10 kHz or higher, and since iron is a component, the saturation magnetic flux density is large, in other words, it is also effective at high frequencies. It is an object of the present invention to provide a magnetic material which can be used at a commercial frequency or at a frequency of 10 kHz or higher without being laminated with an inductor.

[0005]

In order to achieve the above object, in the magnetic material of the present invention, a thin layer of a high specific resistance material is formed on the surface of powder particles containing iron as a component, and the above treatment is performed. A large number of the obtained particles are compacted, placed in a furnace and sintered at a temperature of at least ½ or more of the melting point of iron, and the thin layers are fused to each other by thermal diffusion to form an integral sintered magnetic material. And

In order to form the high resistivity material on the surface of powder particles containing iron, it is effective to oxidize the surface of the powder particles. As another method, it is effective to infiltrate the powder with a colloid or a solution such as a metal oxide produced separately from the powder, and then press the powder and put it in a furnace for sintering. Alternatively, a so-called known spark sintering method can be used instead of placing in a furnace.
A spark sintering device is also considered to be a furnace in a broad sense.

In addition to the above metal oxides, nitrides, fluorides, chlorides, bromides, and iodides are also high-resistance substances,
It is also possible to separately produce at least one colloid or solution and infiltrate the powder. Further, even if the surface of the powder is nitrided, fluorinated, chlorinated, brominated, or the like, a thin layer of a high resistance substance can be formed.

In addition to the above metal oxides, at least one of magnetic colloids such as iron oxide colloids, ferrite colloids, iron colloids, nickel colloids, and cobalt colloids known as so-called magnetic colloidal fluids is used as the oxide. If at least one of the colloids from the colloid to the iodide colloid is mixed, or if the iron oxide colloid and the ferrite colloid are used alone,
Not only a substance with a high specific resistance, but also a substance with a high specific resistance and a high magnetic permeability that also has a high magnetic permeability. Such a colloid is adhered to the surface of powder particles containing iron by a method such as infiltration. If pressed and sintered, the polycrystalline powder particles will be sintered and bonded to each other through high resistivity and high magnetic permeability materials to form an integral magnetic core, which will greatly reduce the eddy current and increase the magnetic permeability. Is prevented to some extent, and since iron is used as a component, a magnetic material having a high saturation magnetic flux density can be obtained.

When the powder is compacted and then placed in a furnace for sintering, its temperature is ideally 1150, which is slightly below the melting point of iron.
Although it is desirable that the temperature is in the order of ° C, thermal diffusion occurs even at 600 ° C or higher and they are fused to each other.

Although the atmosphere in the furnace varies depending on the sintering conditions, either an inert gas such as hydrogen, air, nitrogen, carbon dioxide, or argon, or a gas containing a small amount of water vapor in any of the above gases or a vacuum. It is desirable that

The sintering temperature is 910, which is the transformation point of iron.
When the temperature is not lower than 0 ° C, it is effective to improve the magnetism of iron by slowly cooling around 910 ° C after sintering and passing the temperature down.

It is obvious that the magnetic material having the above-described structure has a higher intrinsic resistance than iron, even if it is not rolled into a laminated magnetic core. That is, since the polycrystalline particles of iron are sinter-bonded to each other through the high-resistance substance, the so-called magnetic core has few voids, but the effective magnetic permeability is relatively high and the sintered toroidal core, EI By using a die core, an L-type core, an EE-type core, a uu-type cut core, or the like, a magnetic core of an inductor or a transformer can be easily obtained.

[0013]

EXAMPLES Examples will be described with reference to the drawings. In FIG. 1, reference numeral 1 indicates one particle of an iron polycrystal, and line 2 described therein indicates a grain boundary. Reference numeral 3 indicates a thin layer of high resistivity material formed on the surface of the material. 2 is shown in FIG.
2 shows a sintered body obtained by compacting and sintering the surface-treated polycrystals shown in FIG. 1, where 1 is a polycrystal, 2 is a grain boundary inside the polycrystal, and 3 is formed at the interface. A thin layer of high resistance material is shown. For comparison, a powder magnetic material called a so-called dust core is shown in FIG. 1 is one of polycrystalline powders, 2 is a grain boundary inside thereof, 4 is water glass as a binder,
Alternatively, an insulating material such as plastic is characterized in that the polycrystals shown in 1 are dispersed in the sea of 3 insulating materials like islands. Therefore, in the dust core,
It is difficult to increase the magnetic permeability because the demagnetizing field that acts on each particle is large and the voids when forming a so-called toroidal core are large. In comparison with this, the magnetic material of the present invention shown in FIG.
Even though they are via high-resistance substances, the particles are sintered and the demagnetizing field that acts on each particle is small, and its permeability and saturation magnetic flux density are higher than those of the dust core. It is also clear from the viewpoint of the density of the substance and confirmed by experiments.

An example of a method of forming a high resistivity material on the surface of particles is as follows. For example, when a liquid such as colloidal silica sol is formed on the surface of powder containing iron by a method such as infiltration of a thin layer of colloid, and the powder is pressed and sintered, the iron powder is deformed and the space between the particles is reduced. Not only the number decreases, but the high resistivity materials on the surface fuse with each other by thermal diffusion to obtain the target material.

As the high resistivity material, colloidal sols other than the above colloidal silica sols, that is, colloidal sols such as alumina, titanium oxide, boron oxide, iron oxide and phosphorus oxide can be used instead of the colloidal silica sols. Furthermore, not only colloids of metal oxides but also colloids of metal nitrides, fluorides, oxides, bromides, and iodides are used instead of the colloid syncasol, a thin layer of a high specific resistance substance is similarly obtained. It is clear that they can be formed on the surface of the particles. Further, by pre-treating the above-mentioned polycrystalline powder containing iron as a component in an appropriate atmosphere or in a solution, the surface of the powder particles is oxidized, nitriding, fluorinating, chlorinating, bromiding, iodinated, etc. Then, a thin layer with high resistivity can be formed on the surface.

Further, the high resistivity material 3 shown in FIG. 4 is added to at least one of the many colloids described in the claims of the present invention and the like, in addition to iron oxide colloid, ferrite colloid, iron colloid, nickel colloid. In addition to magnetic colloids such as cobalt colloid, a mixture of molybdenum colloid, chromium colloid, phosphorus colloid, aluminum colloid, colloid of at least one element that can be one component of ferromagnetic substance such as silicon colloid, Infiltrate iron-based powder to form a thin layer of mixed colloid on the surface of powder particles,
When pressed and sintered, the high specific resistance material 3 shown in FIG. 4 is not only a high specific resistance material, but also a high magnetic permeability material 5 in the thin film of high specific resistance and high magnetic permeability material. Therefore, the effective magnetic permeability of the sintered body increases.

In FIG. 4, 1 is polycrystalline particles containing iron as a component, 2 is a grain boundary, 3 is a thin layer in which high resistivity materials are thermally diffused and sintered, and 5 is a thin layer of high resistivity material. A high-permeability substance formed inside the layer, which is iron oxide, ferrite,
Iron, nickel, cobalt, molybdenum, chromium, phosphorus,
It is a high magnetic permeability material containing at least one of aluminum and silicon.

As the polycrystalline particles 1 containing metallic iron as a component shown in FIGS. 1, 2 and 4, at least one of pure iron, silicon-containing iron, sendust, chromium-containing iron, permalloy and molybdenum permalloy is used. Can be used.

The method for producing the colloid is known,
An example of the document will be given. "Basics of Colloid Chemistry" Masayuki Nakagaki et al./Dainippon Book "Magnetic Fluid" Ara Taketomi et al./Nikkan Kogyo Shimbun

[0020]

EFFECTS OF THE INVENTION It is not necessary to form a thin plate and stack it like a conventional metal magnetic material, and it is possible to produce a magnetic core with a small eddy current loss only by compression molding and sintering. Further, unlike a magnetic core such as a dust core, which is simply powder-molded through a binder, the function of the demagnetizing field is small, a high effective magnetic permeability is obtained, and a high saturation magnetic flux density is obtained due to the high iron density. Further, since the polycrystals are separated from each other by a material having a high specific resistance, it is difficult for an eddy current to flow, so that a magnetic core usable up to a high frequency can be obtained. This means that it is possible to obtain an inductor for a normal mode noise filter and a transformer core of commercial frequency.

[Brief description of drawings]

FIG. 1 shows one particle of a polycrystalline body containing iron.

2 shows an example in which six particles of the polycrystalline body shown in FIG. 1 are sintered together.

FIG. 3 shows a conventional dust core called a dust core.

FIG. 4 shows an example in which a high magnetic permeability material is formed inside a high resistivity material thin layer separating two polycrystalline particles.

[Explanation of symbols]

 1 One of polycrystalline particles of iron 2 1 Grain boundary inside 1 3 Thin layer of high resistivity material formed on the surface of 1 4 Insulating material as binder of dust core 5 3 Generated in thin layer of 3 High permeability material

Claims (11)

[Claims] 1. Polycrystalline particles containing at least metallic iron as a component, a thin layer of a high resistivity material formed so as to cover the surfaces of the polycrystalline particles, and a thin layer which is depressed by the thin layer and mutually baked. A sintered magnetic material characterized by being composed of many polycrystalline particles bonded together. 2. A thin layer of a high resistivity material is formed on the surface of particles of a polycrystalline body containing at least metallic iron as a component, and a large number of the particles subjected to the surface treatment as described above are put into a mold and compression molded. And a method of manufacturing a sintered magnetic material, characterized by sintering the green compact. 3. The "sintering" according to claim 1, wherein the "sintering" is performed by heating the high resistivity material by placing a green compact in a furnace having a temperature of at least ½ of the melting point of iron. A method of manufacturing magnetic materials, characterized in that they are diffused and fused to each other by. 4. The magnetic material according to claim 1, wherein the high resistivity material according to claim 1 or 2 is an oxide obtained by oxidizing the surface of the polycrystalline particles. 5. The high resistivity material according to claim 1 or 2 is a mixture containing at least one of a metal oxide, a nitride, a fluoride, a chloride, a bromide and an iodide. The magnetic material according to claim 1, characterized in that 6. The high resistivity material according to claim 1 or 2, wherein at least one of oxides of silicon, iron, aluminum, boron, manganese, zinc, nickel, chromium, phosphorus and titanium is used. The magnetic material according to claim 1, wherein the magnetic material comprises: 7. The high resistivity material according to claim 1 or 2, wherein the high-resistivity substance is at least one colloidal sol selected from metal oxides, nitrides, fluorides, chlorides, bromides, iodides, and metal elements. The magnetic material according to claim 1, wherein the solution is adhered to the surface of powder particles containing metallic iron by a method such as infiltration, and then a large number of particles are pressed and sintered. 8. The colloidal sol according to claim 7, which is colloidal silica sol, colloidal titanium oxide sol, colloidal phosphorus sol, colloidal alumina sol, colloidal boron oxide sol, colloidal iron oxide sol, colloidal ferrite sol, colloidal iron sol, colloidal nickel. Surface of powder particles by infiltrating a colloidal sol containing at least one of sol, colloidal cobalt sol, colloidal molybdenum sol, colloidal chrome sol, colloidal aluminum sol, and colloidal silicon sol into powder containing at least metallic iron as a component. The magnetic material according to claim 1, wherein a powder obtained by compacting a powder in which a thin layer of colloid is formed is sintered at a temperature of at least ½ of the melting point of iron. 9. The polycrystalline body containing at least metallic iron as a component according to claim 1, is at least one of pure iron, silicon-containing iron, sendust, chromium-containing iron, permalloy, and molybdenum permalloy. The magnetic material according to claim 1, which is characterized. 10. The magnetic material according to claim 1, wherein the sintering according to claim 1 is performed by placing it in a furnace for sintering or by known discharge sintering. 11. The high specific resistance material according to claim 1,
Similarly, the surface of the polycrystalline particles described above is oxidized, nitrided, fluorinated,
2. The magnetic material according to claim 1, wherein the magnetic material is treated so as to form at least one of chloride, bromide and iodide so as to form a thin layer of a high resistivity material.