JP5027390B2 - Deposited film-coated iron powder - Google Patents

Description

  The present invention relates to a deposited film-coated iron powder for producing a high-resistance composite soft magnetic material, and the composite soft magnetic material produced from this deposited film-coated iron powder is used in various electromagnetic circuit components that require low iron loss. For example, it is used as a material for various electromagnetic parts such as motors, actuators, yokes, cores, and reactors.

  Generally, soft magnetic materials used in various electromagnetic circuit components are required to have low iron loss. Therefore, electrical resistance is increased to reduce eddy current loss, and coercive force is reduced to reduce hysteresis loss. This is generally known. Furthermore, in recent years, since the miniaturization and high response of the electromagnetic circuit have been demanded, higher magnetic flux density is also regarded as important.

As an example of a raw material powder for producing a soft magnetic material having such a high specific resistance, an oxide film-coated iron powder in which an iron-containing Mg-containing ferrite film is coated on the surface of an iron powder is known (see Patent Document 1). ).
Japanese Patent Laid-Open No. 11-1702

  However, the conventional oxide-coated iron powder coated with Mg-containing ferrite film is coated with the conventional Mg-containing ferrite film in order to coat the surface of the iron powder with Mg-containing ferrite film by a chemical method. The composite soft magnetic material produced by performing high-temperature strain-relief firing on a green compact that has been press-molded from the Mg-containing ferrite film is generally unstable to heat, and changes during firing, resulting in a decrease in insulation. To do.

  Furthermore, the Mg-containing ferrite film does not have sufficient adhesion to the surface of the iron powder. For this reason, the composite soft magnetic material produced by press-molding and firing the oxide film-coated iron powder coated with the conventional Mg-containing ferrite film is pressed. The Mg-containing ferrite film is peeled off or torn during the molding, so that a sufficient insulating effect cannot be exhibited. Therefore, there is a drawback that a composite soft magnetic material having a sufficiently high specific resistance cannot be obtained.

  Therefore, the present inventors are an iron powder in which the high resistance film on the surface of the iron powder is not torn during the press molding and the high resistance film is firmly adhered to the surface even after press molding. High resistance that reduces eddy current loss with high resistance without reducing surface insulation even when firing, and lowers coercive force and lowers hysteresis loss when firing with strain relief annealing Research was conducted to produce film-coated iron powder.

As a result, (i) iron powder in which a phosphate film was formed on the surface of the iron powder (hereinafter referred to as phosphate-coated iron powder) was prepared by subjecting the iron powder to phosphoric acid treatment. When the mixed powder obtained by adding and mixing the Mg powder to the iron powder is subjected to heat treatment while rolling in an inert gas atmosphere or a vacuum atmosphere, the deposited film composed of Mg, Fe, P and O becomes an iron powder. The deposited film-coated iron powder coated on the surface of this was obtained, and the deposited film composed of Mg, Fe, P and O was composed of Mg—Fe—P—O quaternary phosphoric acid composed of Mg, Fe, P and O. Containing a salt compound and an Mg—Fe—O ternary oxide composed of Mg, Fe and O, and having iron phosphide fine particles dispersed in the substrate,
(B) The deposited film of the deposited film-coated iron powder is formed on the surface of the conventional oxide film-coated iron powder because the iron phosphide fine particles are dispersed in the substrate of the deposited film and has high toughness. Compared to the Mg-containing ferrite film, it is easier to follow the deformation of the iron powder during press molding, and this deposited film has much better adhesion to the iron powder, so the deposited film is an insulating film during press molding Can be maintained and high resistance can be maintained because the deposited film-coated iron powder is less likely to come into contact with each other, and even if high temperature strain relief firing is performed after press forming the deposited film-coated iron powder, the insulation of the deposited film is unlikely to deteriorate. The eddy current loss is reduced, and further, when the strain relief firing is performed, the coercive force can be further reduced and the hysteresis loss is reduced, so that a composite soft magnetic material having low iron loss can be obtained.
(C) The Mg—Fe—P—O quaternary phosphate compound and the Mg—Fe—O ternary oxide contained in the deposited film contain a crystalline MgO solid solution wustite phase. thing,
(D) The knowledge that the deposited film in which the iron phosphide fine particles are dispersed in the substrate preferably has a fine crystal structure with a crystal grain size of 200 nm or less has been obtained.

This invention is made based on such knowledge,
(1) A phosphate-coated iron powder having a phosphate film formed by phosphoric acid treatment is prepared, and the mixed powder obtained by adding and mixing Mg powder to the phosphate-coated iron powder is treated with an inert gas. Heat treatment is performed while rolling in an atmosphere or vacuum atmosphere, and Mg—Fe—P—O quaternary phosphate compound composed of Mg, Fe, P and O and Mg—Fe— composed of Mg, Fe and O A method for producing a deposited film-coated iron powder comprising coating a deposited film containing an O ternary oxide and in which iron phosphide fine particles are dispersed in a substrate on the surface of the iron powder ;
(2) A deposited film-coated iron powder in which a deposited film composed of Mg, Fe, P and O is coated on the surface of the iron powder, wherein the deposited film is Mg—Fe composed of Mg, Fe, P and O -P-O quaternary phosphate compounds and Mg, Fe and O consists Mg-Fe-O ternary oxide comprises and compost phosphide iron particles that are dispersed in the matrix Sekimaku coated iron powder ,
(3) The Mg—Fe—P—O quaternary phosphate compound and the Mg—Fe—O ternary oxide contained in the deposited film contain a crystalline MgO solid solution wustite phase. The deposited film-coated iron powder according to (2) ,
(4) The deposited film is characterized by the deposited film-coated iron powder according to (2) or (3), which has a fine crystal structure with a crystal grain size of 200 nm or less.

As described above, the deposited film-coated iron powder according to (1) to (4) of the present invention is obtained by adding a mixed powder obtained by adding Mg powder to phosphate-coated iron powder and mixing it with an inert gas atmosphere. Alternatively, it is prepared by performing heat treatment while rolling in a vacuum atmosphere, and then performing oxidation treatment in an oxidizing atmosphere. More specifically, Mg powder is added to and mixed with phosphate-coated iron powder. The mixed powder thus obtained was heat-treated while rolling in an inert gas atmosphere or vacuum atmosphere at a temperature of 150 to 1100 ° C. and a pressure of 1 × 10 ⁻¹² to 1 × 10 ⁻¹ MPa, and then further oxidized. It is produced by performing an oxidation treatment in an atmosphere.
The term “deposited film” usually indicates a film in which atoms constituting the film formed by vacuum evaporation or sputtering are deposited on, for example, a substrate. The deposited film formed on the surface of the iron powder of the present invention is a phosphate. The film in which iron phosphate (Fe—PO) and Mg on the surface of the coated iron powder are deposited on the iron powder surface with a reaction is shown. The deposited film in which the iron phosphide fine particles formed on the surface of the iron powder of the present invention are dispersed in the substrate has high toughness because the iron phosphide fine particles are dispersed in the substrate. For this reason, the deformation of the iron powder at the time of press molding is sufficiently followed and the adhesion of the oxide film to the iron powder is remarkably excellent.

  The film thickness of the deposited film formed on the surface of the iron powder of the present invention is within the range of 5 to 500 nm in order to obtain the high magnetic flux density and high specific resistance of the composite soft magnetic material obtained by compacting. Preferably there is. If the film thickness is less than 5 nm, the specific resistance of the powder-molded composite soft magnetic material is not sufficient and the eddy current loss increases. On the other hand, if the film thickness is thicker than 500 nm, it is not preferable. This is because the magnetic flux density is lowered, which is not preferable. A more preferable film thickness is 5 to 200 nm.

  The Mg—Fe—P—O quaternary phosphate compound and the Mg—Fe—O ternary oxide contained in the deposited film constituting the deposited film-coated iron powder of the present invention include crystalline MgO solid solution wustite It is preferable that a mold phase is included. The crystalline MgO solid solution wustite type phase may have Fe or / and Mg partially substituted with P, but most preferably has an NaCl type crystal structure.

The deposited film constituting the deposited film-coated iron powder of the present invention preferably has finer crystal grains, and preferably has a fine crystal structure with a crystal grain size of 200 nm or less. By having such a fine crystal structure, the microcrystalline deposition film can follow the deformation of the powder during compaction molding to prevent the coating from being broken, and also prevent contact bonding between iron powders during firing. In addition, even when high-temperature strain relief firing is performed, the oxide is stable and can prevent deterioration in insulation, and can maintain a high resistance. Therefore, eddy current loss is reduced. If the crystal grain size is larger than 200 nm, the thickness of the deposited film becomes thicker than 500 nm, and the magnetic flux density of the compacted soft magnetic material is reduced, which is not preferable.
The iron powder that is a raw material powder for producing the deposited film-coated iron powder of the present invention preferably has 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 powder is lowered, so the value of the magnetic flux density is lowered. On the other hand, the average particle size is less than 500 μm. If it is too large, the eddy current inside the powder increases and the magnetic permeability at high frequency decreases.

  Mg-Fe-P-O quaternary phosphate compound comprising Mg, Fe, P and O and Mg-Fe-O ternary system comprising Mg, Fe and O constituting the deposited film-coated iron powder of the present invention The oxide may be a quasi-ternary oxide deposited film in which a part of Mg is substituted with one or more of Al, Si, Ni, Mn, Zn, Cu, and Co of 10% or less with respect to Mg.

  Next, a method for producing a composite soft magnetic material using the deposited film-coated iron powder of the present invention will be described.

  The deposited film-coated iron powder of the present invention can be produced by compacting and sintering by a conventional method. Moreover, 0.05 to 1% by mass of one or two of silicon oxide and aluminum oxide having an average particle size of 0.5 μm or less is added to the deposited film-coated iron powder of the present invention to produce a mixed powder, The mixed powder can be produced by compacting and sintering by a conventional method.

  The composite soft magnetic material produced by this production method includes an Mg—Fe—P—O quaternary phosphate compound composed of Mg, Fe, P and O and an Mg—Fe—O ternary composed of Mg, Fe and O. High resistivity composite soft magnetism having a structure in which a deposited film containing iron oxide is surrounded by iron oxide and a structure in which deposited film coated iron powder is bonded with silicon oxide or aluminum oxide Since the composite soft magnetic material is sintered via silicon or aluminum oxide, the mechanical strength can be further increased.

  In this case, the coercive force can be kept small from being sintered mainly with silicon oxide or aluminum oxide, and thus a composite soft magnetic material with little hysteresis loss can be produced. It is preferably performed at a temperature of 400 to 1300 ° C. in an active gas atmosphere or an oxidizing gas atmosphere.

  Further, a wet solution such as a silica sol-gel (silicate) solution or an alumina sol-gel solution is added to the deposited film-coated iron powder of the present invention, followed by drying. After the compression mixture is compression-molded, an inert gas atmosphere or A composite soft magnetic material can be produced by firing at a temperature of 400 to 1300 ° C. in an oxidizing gas atmosphere.

Further, a composite soft magnetic material having further improved specific resistance and strength is prepared by mixing the deposited film-coated iron powder of the present invention with an organic insulating material, an inorganic insulating material, or a mixed material of an organic insulating material and an inorganic insulating material. be able to. In this case, as the organic insulating material, epoxy resin, fluorine resin, phenol resin, urethane resin, silicone resin, polyester resin, phenoxy resin, urea resin, isocyanate resin, acrylic resin, polyimide resin, or the like can be used. As the inorganic insulating material, phosphates such as iron phosphate, various glassy insulators, water glass mainly composed of sodium silicate, insulating oxides, and the like can be used.
Further, one or more of boron oxide, vanadium oxide, bismuth oxide, antimony oxide and molybdenum oxide are added to the deposited film-coated iron powder of the present invention as B ₂ O ₃ , V ₂ O ₅ , Bi ₂ O _3. , Sb ₂ O ₃ , MoO _{3 in} terms of 0.05 to 1% by mass, mixed and then compacted, and the compacted product obtained is sintered at a temperature of 500 to 1000 ° C. to form a composite soft magnetism A material can be produced. The composite soft magnetic material produced in this way is composed of one or more of boron oxide, vanadium oxide, bismuth oxide, antimony oxide and molybdenum oxide, B ₂ O ₃ , V ₂ O ₅ , Bi ₂ O _3. , Sb ₂ O ₃ , MoO _{3 in} terms of 0.05 to 1% by mass, with the balance being composed of the deposited film-coated iron powder of the present invention, the deposited film, boron oxide, vanadium oxide, bismuth oxide A film is formed by reacting one or more of antimony oxide and molybdenum oxide.

Further, this composite soft magnetic material is composed of a boron oxide sol solution or powder, a vanadium oxide sol solution or powder, a bismuth oxide sol solution or powder, an antimony oxide sol solution or powder, and a molybdenum oxide sol solution or powder. 1 to 2 or more of B ₂ O ₃ , V ₂ O ₅ , Bi ₂ O ₃ , Sb ₂ O ₃ , MoO _{3 in} terms of 0.05 to 1% by mass, the balance being the deposited film-coated iron of the present invention A mixed deposited film-coated iron powder obtained by blending, mixing and drying so as to have a composition composed of powder and coating the deposited film-coated iron powder of the present invention with an oxide dry gel or a mixed oxide composed of powder. This mixed deposited film-coated iron powder is compacted and molded, and then sintered at a temperature of 500 to 1000 ° C. to obtain.
A composite soft magnetic material having a high specific resistance produced by using these deposited film-coated iron powders of the present invention comprises an iron particle phase and a grain boundary phase surrounding the iron particle phase. It is preferable to include an oxide containing a high-quality MgO solid solution wustite type phase. The crystalline MgO solid solution wustite type phase may have Fe or / and Mg partially substituted with P, but most preferably has an NaCl type crystal structure.
The composite soft magnetic material produced using the deposited film-coated iron powder of the present invention has high density, high strength, high specific resistance and high magnetic flux density. This composite soft magnetic material has high magnetic flux density, high frequency and low iron loss. Therefore, it can be used as a material for various electromagnetic circuit components utilizing this feature. Examples of the electromagnetic circuit component include a magnetic core, a motor core, a generator core, a solenoid core, an ignition core, a reactor, a transformer, a choke coil core, and a magnetic sensor core. And in electric equipment incorporating an electromagnetic circuit component made of a composite soft magnetic material having high resistance using the deposited film-coated iron powder of the present invention, an electric motor, a generator, a solenoid, an injector, an electromagnetically driven valve, an inverter, a converter There are transformers, relays, magnetic sensor systems, etc., and it is possible to improve the efficiency, performance, size and weight of electrical equipment.

  When a composite soft magnetic material is produced by press molding the deposited film-coated iron powder of the present invention, the deposited film has a high degree of toughness because the iron phosphide fine particles are dispersed in the substrate. Even if the powder is press-molded, the film is less likely to break during molding. Therefore, the resulting composite soft magnetic material has high specific resistance, so it has low eddy current loss and low coercive force. A composite soft magnetic material having a low hysteresis loss can be produced stably at a low cost, and brings about an excellent effect in the electric and electronic industries.

Example Commercially available phosphate-coated iron powder having an average particle size of 70 μm was prepared as a raw material powder, and Mg powder having an average particle size of 50 μm was further prepared. Mg powder is added to the phosphate-coated iron powder at a ratio of phosphate-coated iron powder: Mg powder = 99.8% by mass: 0.2% by mass to prepare a mixed powder. The deposited powder coated iron of the present invention in which the deposited film is coated on the surface of the iron powder by heating the mixed powder while rolling under the conditions of temperature: 650 ° C., pressure: 1 × 10 ⁻⁴ MPa, and holding for 1 hour. A powder was prepared. The cross-sectional structure of the deposited film formed on the deposited film-coated iron powder of the present invention was observed with a transmission electron microscope, and the transmission electron microscope structure photograph thereof is shown in FIG. The thickness and maximum crystal grain size of the deposited film formed on the deposited film-coated iron powder of the present invention were determined from the photograph of FIG. 1, and the results are shown in Table 1.

  Furthermore, the graph of FIG. 2 shows the result of examining the concentration distribution of Mg, O, P and Fe in the depth direction of the deposited film using an Auger electron spectrometer. From the results shown in the graph of FIG. 2, it was found that the elements constituting the deposited film were Mg, Fe, P and O.

  Furthermore, when the deposited film formed on the surface of the deposited film-coated iron powder of the present invention was analyzed by an X-ray photoelectron spectrometer and the binding energy was analyzed, the iron phosphide fine particles were dispersed in the substrate. And Mg—Fe—P—O quaternary phosphate compound composed of Mg, Fe, P and O and Mg—Fe—O ternary oxide composed of Mg, Fe and O are present. It was. Further, from the electron diffraction pattern of the deposited film formed on the surface of the deposited film-coated iron powder of the present invention, Mg—Fe—P—O quaternary phosphate compound composed of Mg, Fe, P and O and Mg, Fe It was found that the Mg—Fe—O ternary oxide composed of and O contains a crystalline MgO solid solution wustite type phase.

The obtained deposited film-coated iron powder of the present invention was put into a mold and press-molded to form a plate-shaped green compact having dimensions of 55 mm in length, 10 mm in width, and 5 mm in thickness, outer diameter: 35 mm, and inner diameter: 25 mm. A ring-shaped green compact having a height of 5 mm is molded, and the obtained green compact is fired in a nitrogen atmosphere at a temperature of 500 ° C. and held for 30 minutes to form a plate and a ring. A composite soft magnetic material made of a body was prepared, the density and specific resistance of the composite soft magnetic material made of this plate-like fired body were measured, and the results are shown in Table 1. Further, the composite soft magnetic material made of a ring-like fired body The magnetic properties of magnetic flux density, coercive force, and magnetic loss such as iron loss at a magnetic flux density of 1.5 T and a frequency of 50 Hz, and iron loss at a magnetic flux density of 1.0 T and a frequency of 400 Hz are measured. The results are shown in Table 1.
Furthermore, when the composite soft magnetic material using the deposited film-coated iron powder of the present invention was observed with a transmission electron microscope, an iron particle phase and a grain boundary phase surrounding the iron particle phase were observed and obtained from the grain boundary phase. From the electron diffraction pattern, it was found that the grain boundary phase contains a crystalline MgO solid solution wustite type phase.
Conventional Example A conventional oxide-coated iron powder in which a Mg-containing ferrite layer is chemically formed on the surface of pure iron powder is prepared, and this conventional oxide-coated iron powder is placed in a mold and press-molded to obtain a length of 55 mm and a width. : A plate-shaped green compact having dimensions of 10 mm, thickness: 5 mm, and a ring-shaped green compact having dimensions of outer diameter: 35 mm, inner diameter: 25 mm, height: 5 mm. Sintering was performed in a nitrogen atmosphere at a temperature of 500 ° C. for 30 minutes to produce a composite soft magnetic material composed of a plate-shaped and ring-shaped sintered body. The density and specific resistance were measured and the results are shown in Table 1. Further, the composite soft magnetic material made of a ring-shaped sintered body was wound, and the magnetic flux density, coercive force, magnetic flux density 1.5T, frequency 50 Hz Iron loss and magnetic flux density 1.0T, frequency 400H Measuring the magnetic properties such as iron loss at the time of, and the results are reported in Table 1.

  From the results shown in Table 1, the composite soft magnetic material produced using the deposited film-coated iron powder of the present invention was compared with the composite soft magnetic material produced using the conventional oxide-coated iron powder and the conventional composite soft magnetic material. Although there is not much difference in density, the composite soft magnetic material produced using the deposited film-coated iron powder of the present invention has a higher magnetic flux than the conventional composite soft magnetic material produced using the oxide-coated iron powder. The deposited film-coated iron powder of the present invention has characteristics such as high density, low coercive force, and extremely high specific resistance, so that the iron loss is remarkably small, especially the iron loss decreases as the frequency increases. It can be seen that is a soft magnetic raw material powder that can provide a composite soft magnetic material having more excellent characteristics than conventional oxide-coated iron powder.

It is a transmission electron micrograph of the cross-sectional structure | tissue of the deposited film currently formed in the deposited film coating iron powder of this invention. It is the graph which investigated the density | concentration distribution of Mg, O, P, and Fe of the depth direction of the deposited film formed in the deposited film coating iron powder of this invention using the Auger electron spectrometer.

Claims (9)

A phosphate-coated iron powder having a phosphate film formed by phosphoric acid treatment is prepared, and the mixed powder obtained by adding and mixing Mg powder to the phosphate-coated iron powder is mixed with an inert gas atmosphere or vacuum. Mg-Fe-PO quaternary phosphate compound composed of Mg, Fe, P and O and Mg-Fe-O ternary composed of Mg, Fe and O A method for producing a deposited film-coated iron powder comprising coating a deposited film containing an oxide based on which iron phosphide fine particles are dispersed in a substrate on the surface of the iron powder . A deposited film coated iron powder in which a deposited film composed of Mg, Fe, P and O is coated on the surface of the iron powder,
The deposited film contains a Mg—Fe—P—O quaternary phosphate compound composed of Mg, Fe, P and O and a Mg—Fe—O ternary oxide composed of Mg, Fe and O and sedimentary Sekimaku coated iron powder phosphide iron particles you characterized by being dispersed in. The Mg—Fe—P—O quaternary phosphate compound and the Mg—Fe—O ternary oxide contained in the deposited film contain a crystalline MgO solid solution wustite phase. The deposited film-coated iron powder according to claim 2 . The deposited film-coated iron powder according to claim 2 or 3 , wherein the deposited film has a fine crystal structure with a crystal grain size of 200 nm or less. A composite soft magnetic material having a high specific resistance produced using the deposited film-coated iron powder according to claim 2 .   6. The composite softening according to claim 5, comprising an iron particle phase and a grain boundary phase surrounding the iron particle phase, wherein the grain boundary phase contains an oxide containing a crystalline MgO solid solution wustite type phase. Magnetic material.   An electromagnetic circuit component comprising the composite soft magnetic material according to claim 5.   8. The electromagnetic circuit component according to claim 7, wherein the electromagnetic circuit component is a magnetic core, a motor core, a generator core, a solenoid core, an ignition core, a reactor, a transformer, a choke coil core, or a magnetic sensor core.   9. An electric device incorporating the electromagnetic circuit component.

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