JP2009164317A - Method for manufacturing soft magnetism composite consolidated core - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soft magnetism composite consolidated core capable of suppressing reduction in the specific resistance in a surface portion. <P>SOLUTION: An oxide coating soft magnetism particle constituted of an Mg containing oxide film is mixed with an inorganic binder to be consolidated by a die for manufacturing the soft magnetism composite consolidation core. After the soft magnetism composite consolidation core is removed from the die, its surface is cleaned with an inorganic acid, Fe oxidation scale of the surface is removed, and a soft magnetism metal particle, after consolidation, removes a continuity part which extends along the surface and is formed by plastic deformation. Thus, the inside consolidated soft magnetism metal particle and an oxide film coating it are brought into a state of being exposed to the surface so as to increase the specific resistance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a soft magnetic composite compacted core used as a material for various electromagnetic circuit components such as a motor, an actuator, a reactor, a transformer, a choke core, and a magnetic sensor core.

  Conventionally, as magnetic core materials for motors, actuators, magnetic sensors, etc., iron powder, Fe-Al iron-based soft magnetic alloy powder, Fe-Ni iron-based soft magnetic alloy powder, Fe-Cr iron-based soft magnetic alloy powder , Fe-Si-based iron-based soft magnetic alloy powders, Fe-Si-Al-based iron-based soft magnetic alloy powders (hereinafter collectively referred to as soft magnetic metal particles) and heat treatment to obtain a soft magnetic firing The binding material is known. This type of soft magnetic sintered material has a high magnetic flux density but a low specific resistance, which has a problem of poor high frequency characteristics. Therefore, in order to increase the specific resistance and improve the high frequency characteristics, a dust soft magnetic material in which soft magnetic metal particles are bonded with water glass or low-melting glass has been proposed (see Patent Document 1 or Patent Document 2).

  However, the composite soft magnetic sintered material obtained by bonding the soft magnetic metal particles with water glass or low melting glass has poor adhesion between the soft magnetic metal particles and water glass or low melting glass. In order to secure strength by bonding with water glass or low melting glass, it must be mixed with a large amount of water glass or low melting glass to such an extent that soft magnetic metal particles are dispersed in water glass or low melting glass. The powder soft magnetic material obtained by using a large amount of water glass or low-melting glass in this way has a large specific resistance, but the magnetic flux density is extremely reduced, and various electronic devices such as motors, actuators, magnetic sensor magnetic cores, etc. There was a problem that it could not be used as a material for parts.

Therefore, for the purpose of achieving both high magnetic flux density and high specific resistance, a soft magnetic metal particle phase and a grain boundary phase surrounding the soft magnetic metal particle phase, the grain boundary phase has a hexagonal crystal structure, a ZnO type phase and a cubic crystal structure. A ZnO type phase having the hexagonal crystal structure is dispersed in contact with the soft magnetic metal particle phase, and the glass phase has the cubic crystal structure. A structure in which a mixed oxide phase of Fe and Zn is dispersed in contact with the ZnO-type phase, and the glass phase is sandwiched and dispersed in contact with the mixed oxide phase of Fe and Zn having the cubic structure A composite soft magnetic sintered material having the following is provided. (See Patent Document 3)
On the other hand, Mg-containing iron oxide coated iron powder coated with Mg-containing ferrite film by chemical method such as chemical plating or coating method is mixed with low melting point glass powder, then compacted, heat treated and powdered magnetic material A method of manufacturing is also known. (See Patent Document 4)

Further, in the method of manufacturing a powder magnetic body core by bonding magnetic powder containing metal magnetic particles while ensuring insulation between the metal magnetic particles, the molded body is formed by friction between the magnetic powder and a mold. A technique for removing the surface layer portion of the dust core with an inorganic acid such as hydrochloric acid is disclosed as a countermeasure against the formation of a film-like conductive portion on the surface of the core and an increase in eddy current loss on the surface. . (See Patent Document 5)
JP-A-5-258934 JP 63-158810 A JP 2004-253787 A JP 2004-297036 A JP 2006-229203 A

According to the composite soft magnetic sintered material described in Patent Document 3, there is a problem that the mixed oxide phase of Fe and Zn is decomposed when heated at a temperature exceeding 600 ° C. However, since the glass powder described in Patent Document 3 is not melted by firing at a temperature at which this decomposition does not occur, for example, firing at 600 ° C., the binding property between the soft magnetic metal particle phases is increased. It was difficult.
In addition, when glass powder is added to zinc oxide-coated soft magnetic metal particles and molded, friction between the glass powder and zinc oxide coating (insulating layer) occurs, and the zinc oxide coating is easily damaged. It was difficult to obtain a soft magnetic composite compacted fired material.

Next, in the technique described in Patent Document 5, although it is disclosed that the powder compact of Fe or Fe alloy is treated with an inorganic acid, the metal magnetic particles used in the magnetic powder and those In the insulating material for insulating and separating the particles and the binder covering them, those that are easily dissolved in acids such as oxides, sulfides, nitrides, etc. are only described as being unsuitable as insulating materials, No specific insulating material is disclosed.
Therefore, when using hydrochloric acid to dissolve Fe, the present inventors conducted an experiment using an organic binder, using a phosphoric acid insulating film that is a prominent insulating material surrounding the magnetic substance powder. It can be seen that both the phosphoric acid insulating film and the organic binder are dissolved by the pickling, and the pickled part is dielectrically broken. Even if the compacted body is simply pickled, the one with high specific resistance is easily I found that there was a problem that could not be obtained.

  The present invention was devised in view of the above-described problems, and its purpose is to remove surface oxide scale and conductive parts due to plastic deformation without causing dielectric breakdown of the surface by pickling, thereby providing a high specific resistance. Therefore, an object of the present invention is to provide a method for producing a soft magnetic composite consolidated core with little eddy current loss.

The inventors of the present invention have studied Fe-based soft magnetic sintered materials and are able to provide a soft magnetic composite consolidated core that does not break the insulation state of the surface even after press molding using a mold. As a specific example, it is fundamental to use Mg-containing oxide-coated or Al ₂ O ₃ oxide-coated soft magnetic metal particles.
That is, by heating an Fe-based soft magnetic metal powder in an oxidizing atmosphere in advance, an oxidized soft magnetic metal particle having an iron oxide film formed on the surface of the soft magnetic metal particle is produced. Mg powder is added to the mixture, and the mixed powder obtained by mixing with a granulation rolling stirring and mixing apparatus is heated in an inert gas atmosphere or a vacuum atmosphere, and then further in an oxidizing atmosphere as necessary. An Mg-containing oxide film obtained by a technique for obtaining an Mg-containing oxide-coated soft magnetic metal particle by performing a heating oxidation treatment is used.
According to this technique, Mg—Fe—O ternary elements such as (Mg, Fe) O and (Mg, Fe) ₃ O ₄ represented by the generally known MgO—FeO—Fe ₂ O ₃ system. Among various system oxides, an oxide in which an Mg—Fe—O ternary oxide deposition film containing at least (Mg, Fe) O is formed on the surface of soft magnetic particles can be obtained.

In the Mg-containing oxide-coated soft magnetic metal particles in which the Mg—Fe—O ternary oxide deposited film containing at least (Mg, Fe) O is formed on the surface of the Fe-based soft magnetic metal particles, Fe Since the adhesion of the oxide film to the soft magnetic metal particles is far superior to that of the conventional material, the oxide film, which is an insulating film, is less likely to break during press molding, and the oxide film is Fe-based soft. Since it exists reliably between magnetic metal particles, even if high-temperature strain relief firing is performed after press molding, the insulating properties of the oxide film do not decrease and high resistivity can be maintained, so eddy current loss is reduced. In addition, since the coercive force can be reduced after the strain relief firing, the hysteresis loss can be kept low, and thus a low loss soft magnetic composite compacted fired material can be obtained.
The present inventors paid attention to this technique and studied a compacting material obtained by compacting the above-mentioned Mg-containing oxide-coated soft magnetic metal particles, and reached the present invention.

(1) In order to achieve the above object, the method for producing a soft magnetic composite compacted core according to the present invention comprises Fe-based soft magnetic metal particles and an Mg-containing oxide film or Al ₂ O coated on the surface of the soft magnetic metal particles. The oxide-coated soft magnetic particles comprising an oxide film ₃ and an inorganic binder are mixed and consolidated by a mold, and the oxide-coated soft magnetic particles are joined by the inorganic binder. After the core is manufactured and the soft magnetic composite compacted core is taken out of the mold, the surface is pickled with hydrochloric acid, and the conductive part due to plastic deformation in which the soft magnetic metal particles after compaction are stretched along the surface is removed. Thus, the specific resistance is increased by setting the inside soft magnetic metal particles and the oxide film covering the particles to the surface.

(2) In order to achieve the above object, the method for producing a soft magnetic composite consolidated core of the present invention is characterized by using concentrated hydrochloric acid as the inorganic acid.
(3) In order to achieve the above object, the soft magnetic composite consolidated core manufacturing method of the present invention is characterized in that an oxide film mainly composed of (Mg, Fe) O is used as the Mg-containing oxide film.
(4) In order to achieve the above object, the method for producing a soft magnetic composite compacted core of the present invention is characterized in that the Fe-based soft magnetic metal particles are Fe, Si, Al, Ni, Cr, Co, V It is characterized in that it is a composition system formed by adding at least one kind.
(5) In order to achieve the above object, the method for producing a soft magnetic composite consolidated core of the present invention is characterized in that any one of Si resin, low-melting glass, and metal oxide is used as the inorganic binder.

In the production method of the present invention, Fe-based soft magnetic metal particles and an Mg-containing oxide coating film coated on the surface of the soft magnetic metal particles can be formed with good adhesion, and further Mg-containing Fe-based soft magnetic metal particles with oxide coating film are joined together by a binder existing at the grain boundary, so that the adhesion between the grain boundary portion and the Mg-containing oxide coating film is high. Therefore, a high-strength soft magnetic composite consolidated core can be obtained.
Moreover, since the Mg-containing oxide coating film can be reliably present around the Fe-based soft magnetic metal particles even after the compacting, a high specific resistance can be obtained and a soft magnetic composite with low eddy current loss. A consolidated core can be obtained.
In addition, when the surface of the soft magnetic composite compacted core is pickled with an inorganic acid such as hydrochloric acid, the Mg-containing oxide-coated film is extremely strong against acids that dissolve Fe, and has excellent acid resistance. Since the conductive portion due to the oxide scale and plastic deformation can be efficiently dissolved and removed, a decrease in specific resistance at the surface portion can be prevented, and a soft magnetic composite consolidated core with little eddy current loss can be obtained.

The electromagnetic circuit component can be used as, for example, a magnetic core, a motor core, a generator core, a solenoid core, an ignition core, a reactor core, a transformer core, a choke coil core, a magnetic sensor core, etc. It is possible to provide an electromagnetic circuit component capable of exhibiting the above.
Electric devices incorporating these electromagnetic circuit components include motors, generators, solenoids, injectors, electromagnetically driven valves, inverters, converters, transformers, relays, magnetic sensor systems, etc. There is an effect that performance and size and weight can be reduced.

In the present invention, first, an Mg-containing oxide-coated soft magnetic metal particle (soft magnetic metal) in which a Mg—Fe—O ternary oxide deposited film containing (Mg, Fe) O is coated on the surface of the soft magnetic metal particle. Particles).
In order to obtain the coated soft magnetic metal particles, the following various raw material powders may be used by selecting one of the methods described in (A) to (D) described later.
Fe-based soft magnetic metal particles as a raw material powder used in the method for producing Mg-containing oxide-coated soft magnetic metal particles of the present invention are conventionally known iron powder, insulated iron powder, Fe-Al based iron. -Based soft magnetic alloy powder, Fe-Ni-based iron-based soft magnetic alloy powder, Fe-Cr-based iron-based soft magnetic alloy powder, Fe-Si-based iron-based soft magnetic alloy powder, Fe-Si-Al-based iron-based soft magnetic alloy Preferably, it is a powder, Fe-Co iron-based soft magnetic alloy powder, Fe-Co-V iron-based soft magnetic alloy powder or Fe-P iron-based soft magnetic alloy powder.
More specifically, the iron powder is a pure iron powder, and the insulation-treated iron powder is a phosphate-coated iron powder or a wet solution such as a silica sol-gel solution (silicate) or an alumina sol-gel solution. This is a silicon oxide or aluminum oxide coated iron powder that is coated on the surface of the iron powder and then dried and fired. The Fe—Al-based iron-based soft magnetic alloy powder contains A1: 0.1 to 20%, and the balance is Fe. And an Fe—Al-based iron-based soft magnetic alloy powder (for example, an alpalm powder having a composition of Fe-15% Al) made of inevitable impurities.

Further, the Fe—Ni-based iron-based soft magnetic alloy powder contains Ni: 35 to 85%, and Mo: 5% or less, Cu: 5% or less, Cr: 2% or less, Mn: 0.5 if necessary. % Nickel-based soft magnetic alloy powder (for example, Fe-49% Ni powder) containing one or two or more of Fe and inevitable impurities, and Fe-Cr-based iron-based soft magnetism The alloy powder contains Cr: 1-20%, and if necessary, contains Al: 5% or less, Nil 5% or less, one or two of them, the balance being Fe-Cr based on Fe and inevitable impurities This is an iron-based soft magnetic alloy powder, and the Fe-Si-based iron-based soft magnetic alloy powder contains Si: 0.1 to 10%, and the balance is Fe-Si-based iron-based soft magnetic alloy composed of Fe and inevitable impurities. A powder is preferred.
The Fe-Si-Al-based iron-based soft magnetic alloy powder contains Si: 0.1 to 10%, Al: 0.1 to 20%, and the balance is Fe-Si-Al composed of Fe and inevitable impurities. Iron-based soft magnetic alloy powder, Fe-CV-based iron-based soft magnetic alloy powder contains C: 0.1-52%, V: 0.1-3%, the balance is Fe and inevitable Fe-Co-V iron-based soft magnetic alloy powder made of impurities, Fe-C iron-based soft magnetic alloy powder contains C: 0.1-52%, the balance consists of Fe and inevitable impurities Fe-Co-based iron-based soft magnetic alloy powder, Fe-P-based iron-based soft magnetic alloy powder contains P: 0.5 to 1%, the balance is Fe-P-based iron consisting of Fe and inevitable impurities It is preferably a base soft magnetic alloy powder (wherein% indicates mass%).

  These Fe-based soft magnetic metal particles are preferably soft magnetic metal particles having an average particle size in the range of 5 to 500 μm. The reason is that if the average particle size is less than 5 μm, the compressibility of the powder is lowered, and the volume ratio of the soft magnetic metal particles is lowered, so the value of the magnetic flux density is lowered. If it is larger than 500 μm, the eddy current inside the soft magnetic metal particles increases and the magnetic permeability at high frequency decreases.

(A) It is obtained by using any one of these various soft magnetic metal particles as a raw material powder and subjecting it to an oxidation treatment in which it is maintained at room temperature to 500 ° C. in an oxidizing atmosphere, and then adding and mixing Mg powder to this raw material powder. The mixed powder was heated in an inert gas atmosphere or a vacuum atmosphere at a temperature of 150 to 1100 ° C. and a pressure of 1 × 10 ⁻¹² to 1 × 10 ⁻¹ MPa, and further in an oxidizing atmosphere if necessary, a temperature of 50 When heated at ˜400 ° C., Mg-containing oxide-coated soft magnetic metal particles having an oxide insulating film containing Mg on the surface of the soft magnetic metal particles are obtained.
The Mg-containing oxide-coated soft magnetic metal particles have much better adhesion than the conventional Mg-containing oxide-coated soft magnetic particles on which an Mg ferrite film is formed. Even if a green compact is produced by press molding, the insulating coating is less likely to break and peel off, and the green compact of the Mg-containing oxide-coated soft magnetic metal particles is fired at a temperature of 400 to 1300 ° C. The soft magnetic composite compacted core thus obtained has a structure in which the Mg-containing oxide film is uniformly dispersed at the grain boundaries and the Mg-containing oxide film is not concentrated and dispersed at the triple points of the grain boundaries.

In the case of the above-mentioned production method, oxidized soft magnetic metal particles are used as raw material powder, and mixed powder obtained by adding and mixing Mg powder to this raw material powder is temperature: 150 to 1100 ° C., pressure: 1 × 10 ^{− In order} to heat in an inert gas atmosphere or a vacuum atmosphere of ¹² to 1 × 10 ⁻¹ MPa, it is preferable to heat the mixed powder while rolling.

  (B) After adding and mixing the silicon monoxide powder to the oxide-coated soft magnetic powder in which an oxide is formed on the surface of the soft magnetic powder by maintaining the soft magnetic metal particles in an oxidizing atmosphere at room temperature to 500 ° C. Alternatively, heating is performed in a vacuum atmosphere with mixing at a temperature of 600 to 1200 ° C., and further, after adding and mixing Mg powder or heating in a vacuum atmosphere with mixing at a temperature of 400 to 800 ° C. An Mg-Si-containing oxide-coated soft magnetic powder in which an Mg-Si-containing oxide film is formed on the surface of the soft magnetic powder is obtained, and is produced using the Mg-Si-containing oxide-coated soft magnetic powder produced by this method. The soft magnetic composite compacted core has a higher density and bending strength than the composite soft magnetic sintered material obtained by compression molding and sintering a mixture of a compound that produces SiO and MgCO or MgO powder. , Resistivity and magnetic flux density is excellent.

(C) An oxide-coated soft magnetic metal powder in which an iron oxide film is formed on the surface of the soft magnetic metal particles by holding the soft magnetic metal particles in an oxidizing atmosphere at room temperature to 500 ° C. After the powders are added and mixed at the same time, or when mixed and heated in a vacuum atmosphere at a temperature of 400 to 1200 ° C., the Mg—Si-containing oxide film is formed on the surface of the soft magnetic metal particles. A Si-containing oxide-coated soft magnetic metal powder is obtained. The soft magnetic composite compacted core produced using the Mg-Si-containing oxide-coated soft magnetic metal powder produced by this method is a compression molding of a conventional mixture of a compound that generates SiO ₂ and MgCO ₃ or MgO powder. The density, bending strength, specific resistance, and magnetic flux density can be made superior to the composite soft magnetic sintered material obtained by sintering.

(D) Mg powder is added to and mixed with the oxide-coated soft magnetic metal powder in which an iron oxide film is formed on the surface of the soft magnetic metal particle by holding the soft magnetic metal particle at room temperature to 500 ° C. in an oxidizing atmosphere. After heating or heating in a vacuum atmosphere under mixing and at a temperature of 400 to 800 ° C., an Mg-containing oxide-coated soft magnetic metal powder in which an Mg-containing oxide film is formed on the surface of the soft magnetic metal powder is obtained.
After adding and mixing silicon monoxide powder to this Mg-containing oxide-coated soft magnetic metal powder or heating it in a vacuum atmosphere while mixing and maintaining the temperature at 600 to 1200 ° C., the surface of the soft magnetic powder is coated with Mg. An Mg-Si-containing oxide-coated soft magnetic metal powder on which an Si-containing oxide film is formed is obtained, and a soft magnetic composite compaction produced using the Mg-Si-containing oxide-coated soft magnetic metal powder produced by this method In the case of the core, the density, bending strength, specific resistance and resistance are higher than those of a composite soft magnetic sintered material obtained by compression molding and sintering a mixture of a compound that generates SiO ₂ and MgCO or MgO powder. The good magnetic flux density can be improved.
The addition amount of the silicon monoxide powder is preferably in the range of 0.01 to 1% by mass, and the addition amount of the Mg powder is preferably in the range of 0.05 to 1% by mass.
The vacuum atmosphere is preferably a vacuum atmosphere at a pressure of 1 × 10 ⁻¹² to 1 × 10 ⁻¹ MPa.

The silicon monoxide (SiO) powder used in the above production method is an oxide having the highest vapor pressure among silicon oxides. Therefore, it is easy to deposit a silicon oxide component on the surface of soft magnetic metal particles by heating. Even if silicon dioxide (SiO ₂ ) powder having a low pressure is mixed and heated, a silicon oxide film having a sufficient thickness may not be formed on the surface of the soft magnetic metal particles. After the silicon monoxide (SiO) powder is added to the oxide-coated soft magnetic powder and mixed, or in a vacuum atmosphere with mixing, the temperature is maintained at 600 to 1200 ° C., so that SiOx (however, x: 1-2) A silicon oxide film-coated soft magnetic powder having a film formed thereon was formed, and when Mg powder was further added to the silicon oxide film-coated soft magnetic powder and heated in a vacuum atmosphere while mixing, Mg-Si- An Mg—Si-containing oxide-coated soft magnetic powder in which an Mg—Si-containing oxide film made of Fe—O is coated on a soft magnetic powder is obtained.

  The aforementioned oxide-coated soft magnetic metal particles are formed by forming an iron oxide film on the surface of the soft magnetic powder by maintaining the soft magnetic metal particles in an oxidizing atmosphere (for example, in the air) at a temperature of room temperature to 500 ° C. Can be produced. This iron oxide film has the effect of improving the coverage of SiO and / or Mg. When the oxide-coated soft magnetic metal particles are produced and heated above 500 ° C. in an oxidizing atmosphere, the soft magnetic metal particles are aggregated to form an aggregate of soft magnetic metal particles, which are sintered and uniform. This is not preferable because surface oxidation cannot be performed. Therefore, the heating temperature during the production of the oxide-coated soft magnetic metal particles was set to room temperature to 500 ° C. A more preferred range is from room temperature to 300 ° C. More preferably, the oxidizing atmosphere is a dry oxidizing atmosphere.

  In the Mg-Si-containing oxide-coated soft magnetic metal particles used in the present invention, the amount of SiO powder added to the oxide-coated soft magnetic metal particles is limited to 0.01 to 1% by mass. If it is less than 0.01% by mass, the thickness of the silicon oxide film formed on the surface of the oxide-coated soft magnetic metal particles is insufficient, so that the amount of Si contained in the Mg-Si-containing oxide film is insufficient. An Mg-Si-containing oxide film with high resistance cannot be obtained, and it is not preferable. On the other hand, when it exceeds 1% by mass, the thickness of the SiOx (x; 1-2) silicon oxide film formed becomes too thick. Thus, the density of the soft magnetic composite compacted fired material obtained by compacting and firing the obtained Mg-Si-containing oxide-coated soft magnetic metal particles may be reduced.

  In the method for producing Mg-Si-containing oxide-coated soft magnetic metal particles according to the present invention, the amount of Mg powder added is set in the range of 0.05 to 1% by mass. If it is less than 05% by mass, the thickness of the Mg film formed on the surface of the oxide-coated soft magnetic metal particles is insufficient, and the amount of Mg contained in the Mg—Si-containing oxide film is insufficient. Mg-Si oxide film cannot be obtained, but it is not preferable. On the other hand, if it is added in excess of 1% by mass, the thickness of the formed Mg film becomes too thick, and the resulting Mg-Si-containing oxide coating is obtained. This is because the density of the soft magnetic composite compacted fired material obtained by compacting and firing the soft magnetic powder is not preferable.

In the method for producing Mg-Si-containing oxide-coated soft magnetic metal particles used in the present invention, the conditions for adding and mixing SiO powder, Mg powder, or a mixed powder of SiO powder and Mg powder to oxide-coated soft magnetic metal particles are set to a temperature. The reason why the vacuum atmosphere is 600 to 1200 ° C. is that even when heated at a temperature lower than 600 ° C., the vapor pressure of SiO is small, so that a sufficiently thick SiO film or Mg—Si-containing oxide film cannot be obtained. On the other hand, if the mixing temperature exceeds 1200 ° C., the soft magnetic metal particles are sintered, and the desired Mg—Si-containing oxide-coated soft magnetic metal particles cannot be obtained. Further, the heating atmosphere at that time is preferably in a vacuum atmosphere at a pressure of 1 × 10 ⁻¹² to 1 × 10 ⁻¹ MPa, and more preferably heated while rolling.

The soft magnetic metal particles used for producing the oxide-coated soft magnetic metal particles are preferably soft magnetic powders having an average particle diameter of 5 to 500 μm. The reason is that if the average particle size is less than 5 μm, the compressibility of the powder is lowered, and the volume ratio of the soft magnetic powder is lowered, so the value of the magnetic flux density is lowered. If it is larger than 500 μm, the eddy current inside the soft magnetic powder increases and the magnetic permeability at high frequency decreases.
The oxidation treatment of the soft magnetic metal particles has an effect of improving the coverage of Mg, and is performed by maintaining the temperature at 50 to 100 ° C. in an oxidizing atmosphere at a temperature of 150 to 500 ° C. or distilled water or pure water. In this case, it is not efficient when the temperature is less than 50 ° C., and on the other hand, if the temperature exceeds 500 ° C. in an oxidizing atmosphere, sintering occurs, which is not preferable. More preferably, the oxidizing atmosphere is a dry oxidizing atmosphere.

The term “deposited film” usually indicates a film in which atoms constituting a film deposited by vacuum evaporation or sputtering are deposited on a substrate, for example. The deposited film used in the present invention is an Fe-based soft magnetic film having an iron oxide film. A film in which iron oxide (Fe—O) and Mg of metal particles are deposited on the surface of the Fe-based soft magnetic metal particle with a reaction, in the present invention, shows an Mg-containing oxide film. The film thickness of the Mg-Fe-O ternary oxide film formed on the surface of the Fe-based soft magnetic metal particles is to obtain a high magnetic flux density and a high specific resistance of the soft magnetic composite compacted core after compacting. It is preferably in the range of 5 nm to 500 nm. If the film thickness is less than 5 nm, the specific resistance of the compacted soft magnetic composite compacted fired material is not sufficient, and eddy current loss increases. Since the magnetic flux density of the powder-molded soft magnetic composite compacted fired material is lowered, it is not preferable. In such a range, the more preferable thickness of the Mg-containing oxide film is in the range of 5 nm to 200 nm.
However, a preferable film thickness range of the Mg-containing oxide film is in the range of 50 nm to 200 nm in consideration of the case of the pickling treatment described later. If the film thickness range is less than 50 nm, the deposited film is too thin in the later-described pickling step, and even the deposited film of the present invention which is inherently resistant to acid resistance, the insulating coating state of the soft magnetic metal particles tends to be insufficient, There is a tendency that the effect of improving the specific resistance cannot be obtained satisfactorily.

  The Mg-containing oxide-coated soft magnetic metal particles produced by the above-described method have an Mg-containing oxide film formed on the surface, and this Mg-containing oxide film reacts with silicon oxide or aluminum oxide to form a composite oxide. Finally, a soft magnetic composite compacted fired material having a high specific resistance in which a composite oxide having a high resistance is interposed at the grain boundary of the soft magnetic metal particles is finally obtained, and sintered through silicon oxide or aluminum oxide. Therefore, a soft magnetic composite compacted fired material having excellent mechanical strength can be produced. In this case, the coercive force can be kept small from being sintered mainly with silicon oxide or aluminum oxide, and thus a soft magnetic composite compacted fired material with less hysteresis loss can be produced. In an inert gas atmosphere or a non-oxidizing gas atmosphere, the temperature is preferably 400 to 1300 ° C.

"Production of soft magnetic composite compacted core"
In order to manufacture a soft magnetic composite compacted core using soft magnetic metal particles coated with the Mg-containing oxide film prepared as described above by the method described above, first, the Mg-containing oxide film-coated soft film prepared by the above-described method is used. The magnetic metal particles are mixed with either an Si resin as an insulating binder (binder), a low-melting glass or a metal oxide and then compacted by a conventional method, in an inert gas atmosphere, or A precursor of a soft magnetic composite compacted core is produced by firing in a non-oxidizing atmosphere.

In this step, first, the Mg-containing oxide-coated soft magnetic metal particles produced by the above-described method are added to Si resin as an inorganic binder, or Bi ₂ O ₃ —B ₂ O ₃ , SnO—P _2. A specified amount of low melting point glass composed of any of O ₃ , SiO ₂ —B ₂ O ₃ —ZnO, SiO ₂ —B ₂ O ₃ —R ₂ O, and Li ₂ O—ZnO is blended.
The addition amount of Si resin can be in the range of 0.2 to 1.5 mass%.
Alternatively, instead of the above Si resin or low melting point glass, Mg-containing oxide-coated soft magnetic metal particles may be replaced with one or two of aluminum oxide, shelf oxide, vanadium oxide, bismuth oxide, antimony oxide, and molybdenum oxide. species or more metal oxides _{B 2 O 3, V 2 O} 5, Bi 2 O 3, Sb 2 O 3, MoO 3 may be blended in the range of 0.05 to 1 mass% in terms of.
After mixing the above-mentioned binder, compacting is performed using a mold, and the resulting compacted body is fired in a non-oxidizing atmosphere at a temperature of 500 to 1000 ° C. to obtain a precursor of a soft magnetic composite compacted core. To manufacture. Moreover, zinc stearate can also be used as a metal oxide.
For example, an inert gas atmosphere such as a nitrogen gas atmosphere or a non-oxidizing atmosphere such as a hydrogen gas atmosphere can be selected as the previous firing atmosphere.

In the present invention, for the purpose of increasing the bending strength of the precursor of the soft magnetic composite compacted core, heat treatment is performed in an oxidizing atmosphere within a temperature range of 400 ° C. to 600 ° C. preferable.
The coated soft magnetic metal particles formed by coating the surface of the soft magnetic metal particles with the Mg—Fe—O ternary oxide deposited film containing (Mg, Fe) O in the precursor by heat treatment in an oxidizing atmosphere The Mg—Fe—O ternary oxide deposited film containing (Mg, Fe) O present at the interface between them is transformed, and the Mg-containing oxidation coated on the surface of the soft magnetic metal particles and the soft magnetic metal particles The Mg-containing oxide-coated soft magnetic particles comprising a material mainly composed of a silicon oxide containing iron oxide, an oxide containing a low-melting glass component, or an iron oxide containing Mg A structure in which a plurality of layers are bonded via a boundary layer, and a precursor of a soft magnetic composite consolidated core can be obtained.

The precursor of the soft magnetic composite compacted core obtained by the above-described method is such that the bond through the grain boundary layer of the plurality of Mg-containing oxide-coated soft magnetic metal particles is combined with the soft magnetic metal particles and the soft magnetic metal particles. A Mg-containing oxide-coated soft magnetic metal particle comprising a Mg-containing oxide film coated on the surface of the metal and a low-melting glass or a metal oxide obtained by the above-described mixed consolidation heat treatment, The iron oxide present in the grain boundary layer between the Mg-containing oxide-coated soft magnetic metal particles is obtained by dispersing and growing the Fe component from the soft magnetic metal particles at the grain boundaries to form an oxide. The Mg-containing oxide film adjacent to the boundary layer is obtained from the Mg-containing oxide film provided in the Mg-containing oxide-coated soft magnetic metal particles before the mixed consolidation firing process.
In the grain boundary layer surrounding the Mg-containing oxide film-coated soft magnetic particles, the main component is one of silicon oxide containing iron oxide, oxide containing a component of low-melting glass, and iron oxide containing Mg. Have an organization to do.

The precursor of the soft magnetic composite compacted core obtained by the above manufacturing method has high density, high strength, high specific resistance, and high magnetic flux density. Since it has a characteristic of loss, it can be used as a material for various electromagnetic circuit components utilizing this characteristic.
In addition, in the precursor of the soft magnetic composite core obtained by the above manufacturing method, the Mg—Fe—O ternary oxide deposited film containing (Mg, Fe) O and the low melting point present at the interface thereof By firing glass or metal oxide in an oxidizing atmosphere, it has a grain boundary layer containing a component of low melting point glass containing iron oxide grown or a grain boundary layer mainly composed of metal oxide containing iron oxide Therefore, the Mg-containing oxide-coated soft magnetic metal particles are particularly well bonded to each other, the bending strength can be further increased, and a high-strength soft magnetic composite consolidated core can be obtained. In addition, the soft magnetic composite compacted fired material obtained by this production method has excellent characteristics that combine high magnetic flux density with high frequency and low iron loss.

The precursor of the soft magnetic composite compacted core having the above structure has the above-mentioned high density, high strength, high specific resistance and high magnetic flux density, and should have the characteristics of high frequency and low iron loss. In the state where the soft magnetic metal particles and the binder are inserted and compacted, and then taken out from the mold, the surface resistivity tends to be lowered.
This is because the soft magnetic metal particles constituting the precursor of the soft magnetic composite compacted core are mainly composed of Fe and are a material having a high Fe content, so that the Fe-based soft magnetic metal particles themselves have a large elongation. Therefore, in the portion that rubs against the inner surface of the mold, as a result of the soft magnetic metal particles extending in the surface direction of the mold, particulate soft magnetic metal particles having a uniform particle size as described above are mixed. Even when the compaction is performed at high temperature and high pressure, the soft magnetic metal particles stretched by plastic working are layered in the plane direction of the soft magnetic composite compacted core, resulting in a plastic deformation that magnetically short-circuits the soft magnetic metal particles. Since there is a conductive portion that accompanies, there is a problem that the specific resistance of the surface decreases and eddy current loss increases. In particular, when used as a high-frequency electrical component, eddy current loss is considered to be particularly affected at the surface portion of the core.
Therefore, in the present invention, the precursor of the soft magnetic composite compacted core is subjected to a pickling treatment described below to produce a soft magnetic composite compacted core in a state in which a decrease in specific resistance on the surface is prevented.

FIG. 1 is a schematic view of a microphotograph showing a partial cross section of a soft magnetic composite compacted core after taking out a mold before pickling. On the inner side of the surface, compacted particles 1 of a large number of amorphous soft magnetic metal powders. Has a structure bonded through a grain boundary layer, but in the surface portion, the structure is formed so that the structure extends long in the longitudinal direction (surface direction of the surface) in FIG. 1, in other words, along the consolidation direction. It is set as the structure | tissue which has the conduction | electrical_connection part 3 by a deformation | transformation.
When it expands in the grain boundary between the compaction particle | grains 1 shown in FIG. 1, the Mg-Fe-O ternary system oxide deposition film and binder layer containing (Mg, Fe) O exist, 1 is insulated and separated. However, in the conductive part 3 by plastic deformation, the compacted particles are stretched widely and thinly in the surface direction, and the Mg—Fe—O ternary oxide deposited film containing (Mg, Fe) O is in the surface direction of the surface. It is extended and arranged so that it may become parallel to.
In this state, since the specific resistance is reduced at the surface portion, the following pickling treatment is performed.

First, the soft magnetic composite compacted core is pickled at room temperature using concentrated hydrochloric acid having a concentration of about 35% to remove the oxide scale on the surface of the soft magnetic composite compacted core and the compacted deformation flow region below it.
In the soft magnetic composite compacted core having the above structure, a Mg—Fe—O ternary oxide deposited film containing (Mg, Fe) O is formed on the surface portion of the soft magnetic metal particles inside the soft magnetic composite compacted core. Therefore, as shown in the schematic diagram of the micrograph of the surface portion of the soft magnetic composite compacted core shown in FIG. 2, a structure in which a large number of compacted particles 1 are bonded after the oxide scale and the conductive portion due to plastic deformation are removed. The desired soft magnetic composite compacted core A can be obtained.
As a result, the soft magnetic metal particles having the Mg—Fe—O ternary oxide film containing (Mg, Fe) O were mixed with the binder and consolidated, and the soft magnetic metal particles were individually insulated and separated. Thus, it is possible to obtain the soft magnetic composite consolidated core A having a consistent textured state from the inner side to the surface side. If the soft magnetic composite compacted core A having the structure shown in FIG. 2 is used, the specific resistance of the surface can be increased, so that a soft magnetic composite compacted core excellent in high frequency characteristics with suppressed eddy current loss is provided. be able to.

Further, the Fe-based soft magnetic metal particles 1 and the Mg-containing oxide coating film coated on the surface of the soft magnetic metal particles 1 can be formed with good adhesion, and further the Mg-containing oxide coating Since the Fe-based soft magnetic metal particles provided with the film are joined together with a binder existing at the grain boundary, the adhesion force with the Mg-containing oxide coating film at the grain boundary part can be made high. A high-strength soft magnetic composite consolidated core can be obtained.
Moreover, since the Mg-containing oxide coating film can be reliably present around the Fe-based soft magnetic metal particles even after the compacting, a high specific resistance can be obtained and a soft magnetic composite with low eddy current loss. A consolidated core can be obtained.
In addition, on the surface of the soft magnetic composite compacted core A after pickling, a plurality of compacted particles 1 have MgO oxide layers and binder layers at their grain boundary portions, but are exposed on the surface of the compacted particles 1. In most of the portions, the surface 1a exposed by dissolving the compacted particles 1 mainly composed of Fe by acid pickling is continuous, and a boundary layer composed of an MgO oxide layer and a binder layer at the boundary part of the adjacent consolidated particles 1 1b is configured as an exposed surface. When the specific resistance is measured in the soft magnetic composite compacted core A, the compacted particles 1 exposed on the surface are insulated and separated by the boundary layer 1b composed of the MgO oxide layer and the binder layer and air, so that the specific resistance is sufficient. High value.
The obtained soft magnetic composite compacted core A is used separately enclosed in an insulating container or case, or is covered with a resin layer for actual use. There is no problem with exposure.

  A 0.1% by mass Mg powder is blended with a soft magnetic metal powder (pure iron powder) having an average particle size of 100 μm, and this blended powder is rolled by a granulation rolling agitation and mixing device in an argon gas atmosphere. Thus, Mg-containing oxide-coated soft magnetic particles were produced. In addition, in the process of the previous stage which rolls with this granulation rolling stirring and mixing apparatus, for example, heat treatment can be performed at 220 ° C. in the atmosphere for 0 to 60 minutes. The thickness of the MgO film “Mg—Fe—O ternary oxide deposition film containing (Mg, Fe) O” obtained according to the oxide film thickness to be generated can be adjusted.

The soft magnetic composite metal particles formed with each MgO film were mixed with 0.3% by mass of a silicone resin and formed into a compact with a molding pressure of 8 t / cm ² (784 MPa) using a mold. A plurality of core precursor samples (size 60 × 10 × 5 mm) were produced.
These precursor samples were subjected to a pickling test immersed in 35% concentrated hydrochloric acid at room temperature, and the pickling times were 0 minutes, 1 minute, 2 minutes, 3 minutes, 5 minutes, 10 minutes, 15 minutes, 20 Table 1 below shows the results of measuring the specific resistance of each of the precursor samples pickled and set at respective values of 25 minutes and 25 minutes as test examples of Sample 1.

Next, instead of coating the MgO layer, a soft magnetic composite metal powder prepared by coating a soft magnetic metal powder of the same material as the previous example with a phosphoric acid insulating film was prepared.
As the iron powder with a phosphoric acid insulating film, a commercially available powder for a dust core was used. The base soft magnetic metal powder is pure iron powder having an average particle diameter of 100 μm as in the previous example, and the thickness of the film is about 100 nm.
This soft magnetic composite metal powder with a phosphoric acid insulating film was mixed with 0.3% by mass of a silicone resin as an organic binder, and compacted with a molding pressure of 8 t / cm ² (784 MPa) to form a soft magnetic composite compacted core. A plurality of precursors (size 60 × 10 × 5 mm) were produced.
These precursors were pickled in 35% concentrated hydrochloric acid at room temperature, and pickling times were 0 minutes, 1 minute, 2 minutes, 3 minutes, 5 minutes, 10 minutes, 15 minutes, and 20 minutes. Table 1 below shows the results of measuring the specific resistance (μΩm) of each of the precursor samples pickled by setting each value for 25 minutes.

"Table 1"
Pickling time Sample 1 0 minutes: specific resistance 2343, 1 minute: specific resistance 3970,
2 minutes: specific resistance 5530, 3 minutes: specific resistance 7240,
5 minutes: specific resistance 10849,
10 minutes: specific resistance 13070, 15 minutes: specific resistance 12568,
20 minutes: specific resistance 14378, 25 minutes: specific resistance 12896,
Sample 2 0 minutes: specific resistance 683, 1 minute: specific resistance 889,
2 minutes: specific resistance 1341, 3 minutes: specific resistance 1946,
5 minutes: specific resistance 2549,
10 minutes: specific resistance 2837, 15 minutes: specific resistance 2089,
20 minutes: specific resistance 1893, 25 minutes: specific resistance 983,

The results shown in Table 1 are shown in FIG. As is apparent from the results shown in Table 1 and FIG. 3, each of the soft magnetic composite compacted cores in which the soft magnetic metal particles having the Mg—Fe—O ternary oxide deposited film containing (Mg, Fe) O are compacted. Sample 1 showed a much higher specific resistance than sample 2 when compared with the same pickling time.
In particular, even if the sample 2 is pickled, it has a specific resistance of the same level as that of the sample 1 before pickling, and the specific resistance starts to deteriorate as the pickling time increases to 25 minutes. This means that in the tissue structure of Sample 2, when the pickling time becomes longer, the insulating film starts to break. Further, it was found that the effect of improving the specific resistance was small even with pickling in Sample 2.
In contrast, Sample 1 shows a specific resistance more than three times that of Sample 2 in the stage before pickling, and the specific resistance is drastically improved by performing pickling for several minutes, and 10000 (μΩm in 5 minutes). In the case of treatment for 10 minutes or more, an excellent specific resistance exceeding 12000 (μΩm) was exhibited.
From the above results, it was confirmed that in Sample 1, the effect of the pickling treatment on the specific resistance value was remarkably high.

  4 shows a cross-sectional photograph of the metal structure of the sample 1 in Table 1 before pickling, FIG. 5 shows a cross-sectional photograph of the metal structure of the sample pickled for 10 minutes, and FIG. 6 shows the structure of the metal structure shown in FIG. FIG. 7 shows a partially enlarged photograph of the metallographic structure shown in FIG. 5. As shown in FIG. 4 or FIG. 6, an oxide scale was formed on the surface, and a conductive part was formed inside by plastic deformation. From the state, these structures can be removed by pickling. From the photographs shown in FIG. 4 and FIG. 6, a soft magnetic composite consolidated core in which soft magnetic metal particles are individually covered with an insulating film and are present on the surface. It is clear that

Next, a change in electrical specific resistance after pickling using a sample with a changed MgO film thickness was tested. When the previous soft magnetic composite metal powder is produced, when the heat treatment is performed at 220 ° C. in the atmosphere for 0 to 60 minutes in the previous stage of rolling by the granulation rolling stirring and mixing device described above, this heat treatment time The electrical resistivity after adjusting the thickness of the oxide film generated on the soft magnetic metal particles according to the thickness, producing a plurality of samples with the MgO thickness changed according to the thickness of the oxide film, and before pickling and pickling for 10 minutes Was measured. The results are shown in Table 2 below and FIG.
"Table 2"
MgO film thickness (nm) Specific resistance before pickling Specific resistance after pickling Sample 3 30 760 2500
Sample 4 32 890 3310
Sample 5 42 1768 6680
Sample 6 45 2076 9300
Sample 7 61 2456 14210
Sample 8 84 3843 13070
Sample 9 98 3541 14230
Sample 10 103 3182 16730
Sample 11 155 4654 14220

Moreover, in addition to the previous test, the result of having measured the compact density by the sample which changed MgO film thickness is shown in the following Table 3 and FIG.
"Table 3"
MgO film thickness (nm) Density of compact (Mg / cm ³ )
Sample 3 30 7.49
Sample 4 32 7.51
Sample 5 42 7.48
Sample 6 45 7.47
Sample 7 61 7.45
Sample 8 84 7.44
Sample 9 98 7.39
Sample 10 103 7.4
Sample 11 155 7.37
Sample 12 200 7.35
Sample 13 270 7.08
Sample 14 400 6.5

From the test results shown in Table 2 and FIG. 8 described above, it is clear that the specific resistance after pickling is improved by the pickling effect in the thickness range of 30 to 155 nm of MgO. The effect of pickling was revealed. In addition, the increase rate of the specific resistance after pickling is larger in the sample with the MgO film thickness of 42 nm and 45 nm than the increase rate of the specific resistance after the pickling in the sample with the MgO film thickness of 30 nm and 32 nm. The rate of increase in the specific resistance after pickling is even greater in the 155 nm sample.
This is presumably because the oxide film on the surface portion was removed by pickling and the inner MgO film was affected by pickling in the range where the MgO film thickness was small. From this, in order to obtain a higher specific resistance after pickling, it is preferable that the MgO film thickness is 42 nm or more, and it is more preferable that the MgO film thickness is 61 nm or more.
Next, from the results shown in Table 3 and FIG. 9, when the MgO film thickness is increased in the range of 30 nm to 200 nm, a high density in the range of 7.35 to 7.51 Mg / cm ³ can be obtained as the compact density. However, when the MgO film thickness is 270 nm, the green body density starts to decrease to 7.08 Mg / cm ^3, and when the MgO film thickness is 400 nm, the green body density is a low value of 6.5 Mg / cm ³ .
Accordingly, in order to obtain a value exceeding 7 Mg / cm ³ as the green density, it is desirable that the MgO film thickness be 270 nm or less, and in order to obtain a higher green density, the MgO film thickness is 30 nm to 200 nm. It can be seen that the range is more desirable.

The soft magnetic material according to the present invention can be used as an electromagnetic circuit component, for example, as a magnetic core, a motor core, a generator core, a solenoid core, an ignition core, a reactor core, a transformer core, a choke coil core, or a magnetic sensor core. In any case, the present invention can be applied to an electromagnetic circuit component that can exhibit excellent characteristics.
Electric devices incorporating these electromagnetic circuit components include motors, generators, solenoids, injectors, electromagnetically driven valves, inverters, converters, transformers, relays, magnetic sensor systems, etc. Performance and small size can be reduced.

FIG. 1 is a schematic cross-sectional view showing a state of a precursor of a soft magnetic composite consolidated core according to the present invention before pickling. FIG. 2 is a schematic cross-sectional view showing a soft magnetic composite consolidated core after pickling according to the present invention. FIG. 3 is a graph showing the relationship between pickling time and specific resistance ρ for the soft magnetic composite consolidated core according to the present invention. FIG. 4 is a cross-sectional photograph showing the metal structure of the soft magnetic composite consolidated core before pickling. FIG. 5 is a cross-sectional photograph showing the metal structure of the soft magnetic composite compacted core after pickling. 6 is an enlarged cross-sectional photograph showing the metal structure of the soft magnetic composite compacted core shown in FIG. 7 is an enlarged cross-sectional photograph showing the metal structure of the soft magnetic composite compacted core shown in FIG. FIG. 8 is a diagram showing the results of testing the change in electrical resistivity after pickling with a sample with a changed MgO film thickness. FIG. 9 is a diagram showing a result of testing a change in the density of a molded body using a sample with a changed MgO film thickness.

Explanation of symbols

1 soft magnetic metal particles,
2 Oxidation scale,
3 Conducting part by plastic deformation

Claims (5)

An oxide-based soft magnetic particle comprising an Fe-based soft magnetic metal particle and an Mg-containing oxide film or an Al ₂ O ₃ oxide film coated on the surface of the soft magnetic metal particle is mixed with an inorganic binder. Then, a soft magnetic composite compacted core is produced by compacting with a mold and joining oxide-coated soft magnetic particles with the inorganic binder, and after removing the soft magnetic composite compacted core from the mold, the surface is inorganic. By pickling with acid and removing the conductive part due to plastic deformation in which the soft magnetic metal particles after consolidation stretched along the surface, the compacted soft magnetic metal particles on the inside and the oxide film covering it are on the surface. A method for producing a soft magnetic composite consolidated core, characterized by increasing a specific resistance in an exposed state.   The method for producing a soft magnetic composite consolidated core according to claim 1, wherein concentrated hydrochloric acid is used as the inorganic acid.   3. The method of manufacturing a soft magnetic composite consolidated core according to claim 1, wherein an oxide film mainly composed of (Mg, Fe) O is used as the Mg-containing oxide film.   2. The Fe-based soft magnetic metal particles are made of a composition system obtained by adding at least one of Si, Al, Ni, Cr, Co, and V to Fe. The manufacturing method of the soft-magnetic composite compaction core in any one of -3.   5. The method for producing a soft magnetic composite consolidated core according to claim 1, wherein any one of Si resin, low-melting glass, and metal oxide is used as the inorganic binder.

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