WO2023033059A1 - Fe基ナノ結晶合金磁心の製造方法及びFe基ナノ結晶合金磁心 - Google Patents
Fe基ナノ結晶合金磁心の製造方法及びFe基ナノ結晶合金磁心 Download PDFInfo
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- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
- H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
- H01F1/147—Alloys characterised by their composition
- H01F1/153—Amorphous metallic alloys, e.g. glassy metals
- H01F1/15333—Amorphous metallic alloys, e.g. glassy metals containing nanocrystallites, e.g. obtained by annealing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
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- C—CHEMISTRY; METALLURGY
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
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- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
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- H—ELECTRICITY
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- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0206—Manufacturing of magnetic cores by mechanical means
- H01F41/0213—Manufacturing of magnetic circuits made from strip(s) or ribbon(s)
- H01F41/0226—Manufacturing of magnetic circuits made from strip(s) or ribbon(s) from amorphous ribbons
Definitions
- the present disclosure relates to a method for manufacturing an Fe-based nanocrystalline alloy magnetic core and an Fe-based nanocrystalline alloy magnetic core.
- Fe-based nanocrystalline alloys are used in magnetic cores of common mode chokes, high-frequency transformers, etc., because they have excellent soft magnetic properties capable of achieving high magnetic permeability.
- a Fe--Si--B--Cu--Nb system nanocrystalline magnetic material containing Fe as a main component is known (Patent Document 1).
- a coil or magnetic core using such a magnetic material is generally obtained by winding a ribbon of a nano-crystallizable Fe-based amorphous alloy to form a cylindrical wound magnetic core and heat-treating the wound core.
- Patent Literatures 2 and 3 disclose techniques for improving magnetic permeability in a high-frequency region by forming an oxide film on the surface of a magnetic ribbon in a magnetic core formed by winding or laminating amorphous magnetic alloy ribbons. is disclosed. This technology suppresses the occurrence of eddy currents flowing between the ribbon layers by insulating the ribbon layers of a magnetic core formed by winding or stacking magnetic ribbons with an oxide film, thereby reducing eddy current loss. It is said that the magnetic permeability is improved. Further, Patent Document 4 discloses a technique for adjusting magnetocrystalline anisotropy and improving magnetic permeability by applying a magnetic field while heat-treating a magnetic core using a nanocrystalline alloy material.
- the present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing an Fe-based nanocrystalline alloy magnetic core that exhibits high magnetic permeability in the low frequency range.
- the present inventors formed an oxide film on the surface of the Fe-based alloy ribbon of the magnetic core material in which the Fe-based alloy ribbon was wound, and then formed the oxide film.
- the inventors have found that an Fe-based nanocrystalline alloy magnetic core exhibiting high magnetic permeability even in a low-frequency range can be obtained by nano-crystallizing an Fe-based alloy in an environment in which the magnetic flux is not generated, resulting in the present invention. That is, the gist of the present invention is as follows.
- a nanocrystallization step of performing nanocrystallization of the nanocrystallizable Fe-based alloy including a nanocrystallization step of performing nanocrystallization of the nanocrystallizable Fe-based alloy;
- the maximum temperature of the heat treatment in the oxide film forming step is a temperature lower than the crystallization start temperature of the nanocrystallizable Fe-based alloy,
- a magnetic field applying step of applying a magnetic field in the height direction of the magnetic core material while heat-treating the magnetic core material after the nano-crystallization step The method for producing an Fe-based nanocrystalline alloy magnetic core according to [1], wherein the maximum temperature of the heat treatment in the magnetic field application step is lower than the crystallization start temperature of the nanocrystallizable Fe-based alloy.
- a magnetic core in which a ribbon is wound The ribbon has, in this order, a base material formed of an Fe-based nanocrystalline alloy containing a first oxide film layer, a second oxide film layer, and an amorphous phase and crystal grains,
- the Fe-based nanocrystalline alloy has a composition represented by the following general formula (I), An Fe-based nanocrystalline alloy magnetic core that satisfies the following (A) and (B) in the depth profile of the following sample X obtained by X-ray photoelectron spectroscopy.
- FexSiaBbCuCNbd ( I ) _ (In general formula (I), a to d (atomic %) are 3.0 ⁇ a ⁇ 12.0, 1.0 ⁇ b ⁇ 7.0, 1.0 ⁇ c ⁇ 5.0 and 1 .0 ⁇ d ⁇ 9.0; x (atomic %) is the remainder other than Si, B, Cu, and Nb and satisfies 73.0 ⁇ x ⁇ 92.0.)
- a Cu 2p peak appears in the depth range corresponding to the first oxide film layer.
- Example X Between the inner peripheral surface and the outer peripheral surface of the Fe-based nanocrystalline alloy magnetic core, there are three regions of a first region, a second region, and a third region from the inner peripheral surface to the outer peripheral surface. , the ribbon located in the second region is cut out and used as a sample. The first region, the second region, and the third region are regions that divide the radial length between the inner peripheral surface and the outer peripheral surface into 40/20/40.
- the X-ray photoelectron spectroscopy analysis is performed on the surface of the sample that faced the outer peripheral surface when the Fe-based nanocrystalline alloy magnetic core was formed by winding.
- the method of manufacturing the Fe-based nanocrystalline alloy magnetic core which shows high magnetic permeability in a low frequency area can be provided. Further, according to a preferred aspect of the present invention, it is possible to provide a method of manufacturing an Fe-based nanocrystalline alloy magnetic core that exhibits high magnetic permeability both in the low frequency region and the high frequency region. Furthermore, according to the present invention, it is possible to provide an Fe-based nanocrystalline alloy magnetic core exhibiting high magnetic permeability in a low frequency region by the above manufacturing method.
- FIG. 4 is a graph showing relative magnetic permeability at a frequency of 10 kHz of Fe-based nanocrystalline alloy magnetic cores obtained in Experimental Examples and Comparative Examples. 4 is a graph showing relative magnetic permeability at a frequency of 100 kHz of Fe-based nanocrystalline alloy magnetic cores obtained in Experimental Examples and Comparative Examples.
- 1 is a schematic diagram for explaining a sample X for X-ray photoelectron spectroscopic analysis
- FIG. Fig. 10 is a TEM image of the cross section of the ribbon forming the Fe-based nanocrystalline alloy magnetic cores obtained in Example 2, Comparative Example 2, and Comparative Example 4 (photograph substituting for drawing). 4 is a depth profile of the Fe-based nanocrystalline alloy magnetic core obtained in Example 2 by X-ray photoelectron spectroscopy.
- 4 is a depth profile of the Fe-based nanocrystalline alloy magnetic core obtained in Comparative Example 2 by X-ray photoelectron spectroscopic analysis. 4 is a depth profile obtained by X-ray photoelectron spectroscopic analysis of the Fe-based nanocrystalline alloy magnetic core obtained in Comparative Example 4.
- FIG. 4 is a depth profile of the Fe-based nanocrystalline alloy magnetic core obtained in Comparative Example 2 by X-ray photoelectron spectroscopic analysis. 4 is a depth profile obtained by X-ray photoelectron spectroscopic analysis of the Fe-based nanocrystalline alloy magnetic core obtained in Comparative Example 4.
- a method for manufacturing an Fe-based nanocrystalline alloy magnetic core according to the first embodiment of the present invention includes an oxide film forming step of heat-treating a magnetic core material in which a nanocrystallizable Fe-based alloy ribbon is wound in an oxidizing atmosphere. , and a nano-crystallization step of performing nano-crystallization of a nano-crystallizable Fe-based alloy by heat-treating the magnetic core material after the oxide film formation step in a non-oxidizing atmosphere.
- the maximum temperature of the heat treatment in the oxide film forming step is a temperature lower than the crystallization start temperature of the nano-crystallizable Fe-based alloy
- the maximum temperature of the heat treatment in the nano-crystallization step is the temperature of the nano-crystallizable Fe.
- the temperature is equal to or higher than the crystallization start temperature of the base alloy.
- the heat treatment temperature referred to in this specification refers to the set temperature of the heat treatment furnace used for heat treatment of the magnetic core material.
- the temperature of the magnetic core material itself is about 5° C. to 10° C. higher than the set temperature of the heat treatment furnace, and can be measured by attaching a thermocouple to the magnetic core material.
- the Fe-based nanocrystalline alloy magnetic core obtained by the manufacturing method according to this embodiment exhibits high magnetic permeability in the low frequency region.
- "relative magnetic permeability” may be used as an index for evaluating "magnetic permeability”.
- the magnetic permeability in the low frequency region is evaluated based on the magnetic permeability at a frequency of 10 kHz.
- the magnetic permeability in the high frequency region is evaluated based on the magnetic permeability at a frequency of 100 kHz.
- the relative magnetic permeability of the Fe-based nanocrystalline alloy core can be calculated by measuring the inductance of a coil wound around the Fe-based nanocrystalline alloy core and using the following formula (1).
- ⁇ r ⁇ / ⁇ 0
- ⁇ : Permeability [H/m] Ll/A/N 2
- L inductance
- H] l magnetic path length [m]
- N number of turns
- the manufacturing method according to the present embodiment is a method for manufacturing an Fe-based nanocrystalline alloy magnetic core having an oxide film capable of suppressing eddy currents, which is a conventional manufacturing method (see, for example, Patent Documents 2 and 3).
- a conventional manufacturing method see, for example, Patent Documents 2 and 3.
- the manufacturing method according to the present embodiment forms an oxide film without causing nanocrystallization in the oxide film forming step, and forms an oxide film to the extent that it affects the magnetic permeability in the nanocrystallization step. This is a method for nano-crystallization of Fe-based alloys.
- the present inventors performed the formation of the oxide film and the nanocrystallization separately in this order to prevent the formation of the oxide film and the nanocrystallization from proceeding simultaneously. Therefore, it is assumed that the magnetic permeability in the low frequency region can be improved.
- Oxide film forming process> a magnetic core material wound with a ribbon of an Fe-based alloy that can be nanocrystallized (hereinafter sometimes simply referred to as "Fe-based alloy") is heat-treated in an oxidizing atmosphere. This is the step of forming an oxide film on the surface of the Fe-based alloy ribbon.
- the maximum temperature of the heat treatment in the oxide film forming step is a temperature below the crystallization start temperature of the Fe-based alloy.
- the Fe-based alloy constituting the Fe-based alloy ribbon is not particularly limited as long as it is an Fe-based alloy that can be nanocrystallized by heat treatment, and examples thereof include Fe-Si-B-Cu-Nb alloys.
- the composition represented by the following general formula (I) is preferably exemplified.
- a to d (atomic %) are 3.0 ⁇ a ⁇ 12.0, 1.0 ⁇ b ⁇ 7.0, 1.0 ⁇ c ⁇ 5.0 and 1.0 ⁇ a ⁇ 12.0, respectively. 0 ⁇ d ⁇ 9.0;
- x (atomic %) is the remainder other than Si, B, Cu, and Nb and satisfies 73.0 ⁇ x ⁇ 92.0. In addition, this remainder may contain unavoidable impurities.
- the crystallization initiation temperature of the nano-crystallizable Fe-based alloy is usually 350° C. or higher and 520° C. or lower, and the Fe—Si—B—Cu—Nb alloy having the composition represented by the above general formula (I). In this case, the crystallization initiation temperature is usually 480° C. or higher and 520° C. or lower.
- the crystallization initiation temperature is the temperature at which an exothermic reaction due to the initiation of nanocrystallization is detected when the temperature is increased at a rate of 10° C./min using a differential scanning calorimeter (DSC). defined as
- the thickness and width of the Fe-based alloy ribbon are not particularly limited as long as they can be wound to form a magnetic core with a practical shape. Specifically, the thickness of the ribbon is usually 8 ⁇ m or more and 25 ⁇ m or less, and the width of the ribbon is usually 5 mm or more and 25 mm or less.
- the magnetic core material a commercially available magnetic core material may be used as it is, or a magnetic core material produced by winding a commercially available Fe-based alloy ribbon may be used.
- a magnetic core material may be used which is produced by rapidly solidifying a molten Fe-based alloy by a super-rapid cooling method to produce an Fe-based alloy ribbon and winding the ribbon.
- the temperature of the molten metal during rapid cooling is desirably 50° C. to 300° C. higher than the melting point of the alloy.
- the ultraquenching method is not particularly limited, and known methods such as a single roll method, a twin roll method, a rotating liquid prevention method, a gas atomization method, and a water atomization method can be employed.
- the production of the Fe-based alloy ribbon by the ultraquenching method may be carried out in an oxidizing atmosphere such as air, in an atmosphere of an inert gas such as argon, helium, or nitrogen, or under vacuum conditions. .
- the Fe-based alloy ribbon usually consists of an amorphous phase.
- the Fe-based alloy ribbon preferably does not contain a crystalline phase, but may partially contain a crystalline phase as long as the effects of the present invention are not impaired.
- an oxygen-containing atmosphere such as oxygen gas or air
- the lower limit of the oxygen concentration in the oxygen-containing atmosphere is not particularly limited as long as an oxide film can be formed on the surface of the Fe-based alloy ribbon. 0 vol % or more, 10.0 vol % or more, or 20.0 vol % or more.
- the upper limit of the oxygen concentration in the oxygen-containing atmosphere is usually 100% or less, and may be 80.0 vol% or less, 60.0 vol% or less, or 40.0 vol% or less. That is, the preferred range of oxygen concentration in the oxygen-containing atmosphere is 0.1 vol% or more and 80.0 vol% or less, 0.2 vol% or more and 100% or less, 0.3 vol% or more and 60.0 vol% or less, 1.0 vol%.
- Moisture may be added to the oxidizing atmosphere by humidified gas, superheated steam, or the like.
- the boiling treatment may be performed on the magnetic core material before the heat treatment in the oxidizing atmosphere.
- the maximum temperature of the heat treatment in the oxide film forming step depends on the type of oxidizing atmosphere, heat treatment time, etc., but is usually 300° C. or higher, preferably 400° C. or higher.
- the temperature is preferably 50°C lower than the crystallization start temperature of the Fe-based alloy, more preferably 60°C lower than the crystallization start temperature of the Fe-based alloy, and even more preferably 70°C lower than the crystallization start temperature of the Fe-based alloy. below temperature. That is, the preferred range of the maximum temperature of the heat treatment is 400° C. or higher and 50° C. lower than the crystallization start temperature of the Fe-based alloy, 300° C. or higher and lower than the crystallization start temperature of the Fe-based alloy, 400° C.
- Examples include a temperature not higher than 60° C. lower than the crystallization start temperature of the Fe-based alloy and a temperature not lower than 400° C. and not higher than a temperature 70° C. lower than the crystallization start temperature of the Fe-based alloy.
- the temperature increase rate up to the maximum temperature and the temperature decrease rate after holding at the maximum temperature are not particularly limited as long as they do not impair the effects of the present invention, and are generally used in heat treatment in the technical field of the present invention. can be applied.
- the holding time at the maximum temperature is usually 1 hour or more, preferably 2 hours or more, more preferably 3 hours or more, and usually 30 hours or less, preferably, depending on the type of oxidizing atmosphere, heat treatment temperature, etc. is 20 hours or less, more preferably 10 hours or less. That is, the preferable range of the holding time at the highest temperature is 1 hour or more and 20 hours or less, 2 hours or more and 30 hours or less, and 3 hours or more and 10 hours or less.
- the nano-crystallization step is a step of performing nano-crystallization of a nano-crystallizable Fe-based alloy by heat-treating the magnetic core material after the oxide film forming step in a non-oxidizing atmosphere.
- the maximum temperature of the heat treatment in the nanocrystallization step is a temperature equal to or higher than the crystallization initiation temperature of the nanocrystallizable Fe-based alloy.
- a non-oxidizing atmosphere means an atmosphere that can suppress the formation of an oxide film to such an extent that the magnetic permeability is not affected.
- a non-oxidizing atmosphere include inert gas atmospheres such as argon, helium, and nitrogen.
- the non-oxidizing atmosphere may contain trace amounts of oxygen.
- the oxygen concentration is usually less than 0.1 vol%, preferably 0.01 vol% or less, more preferably 0.001 vol% or less.
- the lower limit of the maximum temperature of the heat treatment in the nano-crystallization step is not particularly limited as long as it is equal to or higher than the crystallization start temperature of the Fe-based alloy, and is preferably 14°C higher than the crystallization start temperature of the Fe-based alloy.
- the upper limit of the maximum temperature of the heat treatment in the nano-crystallization step is usually 59° C. or lower than the crystallization start temperature of the Fe-based alloy, preferably 44° C. or lower than the crystallization start temperature of the Fe-based alloy. More specifically, when the crystallization start temperature of the Fe-based alloy is about 516° C., the heat treatment temperature in the nano-crystallization step is usually 516° C. or higher, preferably 530° C.
- the preferred range for the maximum temperature of the heat treatment is a temperature that is 14°C higher than the crystallization start temperature of the Fe-based alloy and a temperature that is 59°C higher than the crystallization start temperature of the Fe-based alloy, and crystallization of the Fe-based alloy.
- the temperature range is 14°C higher than the initiation temperature and 44°C higher than the crystallization initiation temperature of the Fe-based alloy. range.
- the temperature increase rate up to the maximum temperature and the temperature decrease rate after holding at the maximum temperature are not particularly limited as long as they do not impair the effects of the present invention, and are generally used in heat treatment in the technical field of the present invention. can be applied.
- the holding time at the above maximum temperature depends on the composition of the Fe-based alloy, the size of the magnetic core, etc., but from the viewpoint of uniformly heating the entire alloy and the viewpoint of productivity, it is usually 30 minutes or more, preferably 50 minutes or more. It is more preferably 90 minutes or more, and usually 10 hours or less, preferably 2 hours or less. That is, the preferable range of the retention time at the maximum temperature is 30 minutes or more and 2 hours or less, 50 minutes or more and 10 hours or less, and 90 minutes or more and 10 hours or less.
- the nanocrystallization step further includes a heat retention step of temporarily stopping the temperature rise when the heat treatment temperature reaches below the maximum temperature in the process of raising the temperature to the maximum temperature described above, and maintaining the heat treatment temperature.
- an overshoot may occur in which the temperature of the magnetic core material becomes higher than the set temperature of the heat treatment furnace due to self-heating at the time of precipitation of the crystal phase.
- overshoot can be suppressed by
- the overshoot causes variations in magnetic permeability of the Fe-based nanocrystalline alloy magnetic core. Therefore, by suppressing the overshoot, the temperature inside the magnetic core material is made uniform, and as a result, variations in magnetic permeability of the Fe-based nanocrystalline alloy magnetic core can be suppressed.
- the suppression of overshoot means that the difference between the set temperature of the heat treatment furnace during nanocrystallization and the actual temperature of the magnetic core material when the heat insulation process is performed is lower than that when the heat insulation process is not performed. also becomes smaller.
- the present inventors speculate as follows as the reason why the thermal insulation process suppresses the overshoot in nanocrystallization and thus suppresses the variation in magnetic permeability of the Fe-based nanocrystalline alloy magnetic core. .
- the temperature above the set temperature of the heat treatment furnace is applied to the magnetic core, which causes excessive precipitation of the crystalline phase, and the magnetic permeability of the Fe-based nanocrystalline alloy magnetic core varies. may occur.
- the heat insulation step is performed before nano-crystallization, the amount of heat energy applied to the magnetic core material around which the Fe-based alloy ribbon is wound is suppressed, so the precipitation rate of the crystal phase slows down, and the crystal phase is formed. Self-heating associated with precipitation is suppressed.
- the overshoot is suppressed and, in turn, the variation in magnetic permeability of the Fe-based nanocrystalline alloy magnetic core is suppressed.
- the heat treatment temperature in the heat retaining step is not particularly limited as long as it is lower than the maximum temperature in the nano-crystallization step, and is usually 65°C lower than the crystallization start temperature of the Fe-based alloy, preferably at the start of crystallization of the Fe-based alloy. It is at least 60° C. lower than the temperature, and usually at most 45° C. lower than the crystallization start temperature of the Fe-based alloy, preferably at least 40° C. lower than the crystallization start temperature of the Fe-based alloy.
- the preferable range of the heat treatment temperature is 65°C lower than the crystallization start temperature of the Fe-based alloy and 40°C lower than the crystallization start temperature of the Fe-based alloy, and the crystallization start temperature of the Fe-based alloy. 60° C. lower than the temperature and 45° C. lower than the crystallization start temperature of the Fe-based alloy.
- the heat treatment time in the heat retention step depends on the heat treatment temperature in the heat retention step, the size of the magnetic core material, etc., but from the viewpoint of uniforming the temperature in the heat treatment furnace, it is usually 30 minutes or more, preferably 60 minutes or more, more preferably 100 minutes. minutes or more, and usually 5 hours or less, preferably 4 hours or less, more preferably 3 hours or less.
- the preferable range of the heat treatment time is 30 minutes or more and 4 hours or less, 60 minutes or more and 5 hours or less, and 100 minutes or more and 3 hours or less.
- the manufacturing method according to the present embodiment may further include a magnetic field applying step of applying a magnetic field in the height direction of the magnetic core material while heat-treating the magnetic core material after the nano-crystallization step. From the viewpoint of improving the magnetic permeability of the Fe-based nanocrystalline alloy magnetic core in a high frequency region, it is preferable to perform the magnetic field application step.
- the maximum temperature of the heat treatment in the magnetic field application step is not particularly limited, and is usually 300° C. or higher, preferably 400° C. or higher, and usually lower than the crystallization start temperature of the Fe-based alloy, preferably the crystallization start of the Fe-based alloy.
- the temperature is 50° C. lower than the temperature, more preferably 60° C. lower than the crystallization start temperature of the Fe-based alloy. That is, the preferred maximum temperature range for the heat treatment is 400°C or higher and lower than the crystallization start temperature of the Fe-based alloy, 300°C or higher and lower than the crystallization start temperature of the Fe-based alloy by 50°C or lower, and 400°C or higher. Also, the temperature range is 60° C.
- the temperature increase rate up to the maximum temperature and the temperature decrease rate after holding at the maximum temperature are not particularly limited as long as they do not impair the effects of the present invention, and are generally used in heat treatment in the technical field of the present invention. can be applied.
- the holding time at the maximum temperature depends on the maximum temperature, the size of the magnetic core material, etc., but from the viewpoint of uniforming the temperature in the heat treatment furnace, it is usually 20 minutes or more, preferably 30 minutes or more. It is usually 5 hours or less, preferably 2 hours or less, more preferably 1 hour or less. That is, the preferable range of the holding time at the highest temperature is 20 minutes or more and 2 hours or less, 30 minutes or more and 5 hours or less, and 30 minutes or more and 1 hour or less.
- the magnetic field is applied to the magnetic core material in the height direction of the magnetic core material, that is, in the width direction of the Fe-based alloy ribbon that constitutes the magnetic core material.
- the strength of the magnetic field applied to the magnetic core material is not particularly limited as long as it is high enough to magnetically saturate the magnetic core, and is usually 50 mT or more, preferably 80 mT or more, more preferably 100 mT or more. 150 mT or less. That is, suitable ranges of magnetic field intensity include ranges of 50 mT to 150 mT, 80 mT to 150 mT, and 100 mT to 150 mT.
- the magnetic field application step may be performed in an oxidizing atmosphere such as air, may be performed in an inert gas atmosphere such as argon, helium, nitrogen, or may be performed under vacuum conditions, but may be performed in an inert gas atmosphere. It is preferable to use
- the heat treatment in the oxide film formation step, the nanocrystallization step, and the magnetic field application step is referred to as including temperature increase, holding at the maximum temperature, and temperature decrease, but it does not necessarily require temperature increase or temperature decrease. do not.
- the atmosphere in the heat treatment furnace may be replaced from an oxidizing atmosphere to a non-oxidizing atmosphere, and the temperature may be raised to perform the nanocrystallization step.
- the heat treatment in each process requires a series of operations of raising the temperature, maintaining at the maximum temperature, and lowering the temperature. preferably included.
- An Fe-based nanocrystalline alloy magnetic core according to a second embodiment of the present invention is a magnetic core formed by winding a ribbon, wherein the ribbon comprises a first oxide film layer, a second oxide film layer, and an amorphous It has a base material formed of an Fe-based nanocrystalline alloy containing phases and crystal grains in this order, and the Fe-based nanocrystalline alloy has a composition represented by the following general formula (I).
- a specific sample sampled from the Fe-based nanocrystalline alloy magnetic core according to this embodiment is subjected to X-ray photoelectron spectroscopy (XPS) analysis to obtain a characteristic depth profile described later.
- XPS X-ray photoelectron spectroscopy
- General formula (I) is defined in ⁇ 1-1. Oxide Film Forming Step>. Therefore, the definitions and preferred embodiments of a to d (atomic %) and x (atomic %) are as follows: ⁇ 1-1. oxide film forming step>.
- the Fe-based nanocrystalline alloy magnetic core according to this embodiment has a composition represented by general formula (I) as a nanocrystallizable Fe- A magnetic core obtained by using a Si--B--Cu--Nb alloy, and exhibits high magnetic permeability in a low frequency region.
- the above ⁇ 1-3. Magnetic Field Application Process> does not need to be performed. This is because the application of a magnetic field does not affect, or only slightly affects, the structure and composition of the oxide film described above.
- the Fe-based nanocrystalline alloy magnetic core is manufactured through the magnetic field application process, it exhibits high magnetic permeability in both the low frequency region and the high frequency region. It is preferably manufactured.
- the ribbon constituting the magnetic core includes the first oxide layer, the second oxide layer, and the second oxide layer. It has a coating layer and a base material formed of an Fe-based nanocrystalline alloy containing an amorphous phase and crystal grains in this order.
- the first oxide film layer is the outermost surface layer of the ribbon.
- the first oxide film layer and the second oxide film layer are formed by the oxide film forming step in the manufacturing method described above.
- the base material is a nanocrystallizable Fe—Si—B—Cu—Nb alloy having a composition represented by the general formula (I) in the nanocrystallization step in the above manufacturing method. It is formed by The base material may contain components other than the Fe-based nanocrystalline alloy, such as components mixed in the process of forming the ribbon and the process of forming the oxide film.
- the first oxide film layer and the second oxide film layer may be formed on at least one surface of the ribbon, but are usually formed on both surfaces of the ribbon.
- the first oxide film layer and the second oxide film layer may be formed on at least part of the surface of the ribbon, but are usually formed over the entire surface of the ribbon.
- the total thickness of the first oxide film layer and the second oxide film layer is not particularly limited. It is 0 nm or more, more preferably 10 nm or more, still more preferably 12 nm or more, and usually 25 nm or less, preferably 20 nm or less. That is, the preferable range of the total thickness of the first oxide film layer and the second oxide film layer is 5.0 nm or more and 20 nm or less, 8.0 nm or more and 20 nm or less, 10 nm or more and 25 nm or less, and 12 nm or more and 25 nm or less. is mentioned.
- the presence or absence of the first oxide film layer and the second oxide film layer can be confirmed by observing the cross section of the ribbon with a transmission electron microscope (TEM). Also, the thicknesses of the first oxide film layer and the second oxide film layer can be measured from TEM images. In order to compare the TEM observation results of the first oxide film layer and the second oxide film layer with the XPS analysis results, TEM imaging is performed so as to obtain a TEM image of the vicinity of the ribbon surface that is the target of the XPS analysis. . During TEM observation, a protective layer may be formed on the first oxide film layer in order to improve the visibility of the first oxide film layer and the second oxide film layer in the TEM image. The protective layer can be formed by a known method such as a deposition method.
- Carbon, platinum, tungsten, or the like can be used as the material of the protective layer.
- a sample for observing the ribbon cross section can be prepared by cutting the ribbon by, for example, the focused ion beam method (FIB method).
- FIB method focused ion beam method
- An example of TEM measurement conditions is shown below.
- XPS analysis of the surface structure of the ribbon including the first oxide film layer, the second oxide film layer, and the base material shows the following (A) and (B). A filling characteristic depth profile is obtained.
- a Cu 2p peak appears in the depth range corresponding to the first oxide film layer.
- B In the depth range corresponding to the first oxide film layer, the intensity of Cu 2p peak is stronger than the intensity of O 1S derived from SiO 2 .
- the Cu 2p peak (maximum value) is at a depth corresponding to the first oxide film layer (that is, the outermost surface layer). It is observed in the depth range corresponding to between the second oxide film layer and the base material, not the range. Therefore, conventional Fe-based nanocrystalline alloy magnetic cores do not satisfy (A) and (B). Therefore, the depth profile that satisfies (A) and (B) is unique to the Fe-based nanocrystalline alloy magnetic core according to this embodiment.
- the Fe-based nanocrystalline alloy magnetic core according to the present embodiment preferably further satisfies the following (C) and (D) in the depth profile by XPS analysis.
- C Peaks of O 1S and Si 2p derived from SiO 2 appear in the depth range corresponding to the second oxide film layer.
- D In the depth range corresponding to the second oxide film layer, the intensity of the peak of O 1S derived from SiO 2 is higher than that of Cu 2p .
- the depth profile when an oxide film is formed on the ribbon surface by natural oxidation the peaks of O 1S and Si 2p derived from SiO 2 correspond to the first oxide film layer. Observed in the depth range. Therefore, in addition to (A) and (B), the depth profile satisfying (C) is also unique to the Fe-based nanocrystalline alloy magnetic core according to this embodiment.
- the Fe-based nanocrystalline alloy magnetic core according to the present embodiment preferably further satisfies the following (E) in the depth profile obtained by XPS analysis.
- E The intensity of the Cu 2p peak in the depth range corresponding to the first oxide film layer is higher than the intensity of the Cu 2p peak in the depth range corresponding to the base material.
- the depth profile of the conventional Fe-based nanocrystalline alloy magnetic core As shown in the examples described later, in the depth profile of the conventional Fe-based nanocrystalline alloy magnetic core, the peak (maximum value) of Cu 2p does not appear in the depth range corresponding to the first oxide film layer, A weak Cu 2p signal is observed. In addition, in the depth range corresponding to the base material, Cu 2p signals with stronger intensity than those in the depth range corresponding to the first oxide film layer are observed. Therefore, the depth profile that satisfies (E) is also unique to the Fe-based nanocrystalline alloy magnetic core according to this embodiment.
- the depth ranges corresponding to the first oxide film layer and the second oxide film layer are based on the thicknesses of the first oxide film layer and the second oxide film layer, respectively, measured from TEM images. Range.
- the strength of Cu 2p in the depth range corresponding to the base material the strength of Cu 2p at a depth where the influence of the oxide film is not observed is adopted. More specifically, the ratio of the minimum intensity of Cu 2p to the maximum intensity of Cu 2p within a depth range of 5 nm is usually 0.80 or more, preferably 0.85 or more, more preferably 0.90 or more.
- a depth range with a small variation in signal intensity is selected, and the intensity of Cu 2p in this depth range is assumed to be the intensity of Cu 2p in the depth range corresponding to the base material.
- Examples of the depth range in which such signal intensity fluctuations are small include, for example, a depth of 15 nm or more in Example 2, a depth of 28 nm or more in Comparative Example 2, and a depth of 21 nm or more in Comparative Example 4. (ranges indicated by arrows in FIGS. 5 to 7).
- sample X the specific sample to be subjected to XPS analysis is sample X below.
- sample X The space between the inner peripheral surface and the outer peripheral surface of the Fe-based nanocrystalline alloy magnetic core is virtually divided into three regions, a first region, a second region, and a third region, from the inner peripheral surface to the outer peripheral surface. A ribbon located in the second region is cut out and used as a sample. The first region, the second region, and the third region are regions that divide the radial length between the inner peripheral surface and the outer peripheral surface into 40/20/40.
- the X-ray photoelectron spectroscopic analysis is performed on the surface of the sample that faces the outer peripheral surface when the Fe-based nanocrystalline alloy magnetic core is formed by winding.
- the reason for using the ribbon positioned within the second region as the sample is as follows.
- the magnetic permeability is located in the vicinity of the intermediate portion between the inner peripheral surface and the outer peripheral surface with respect to the radial direction of the magnetic core, or slightly closer to the inner peripheral surface than the vicinity of the intermediate portion. It is affected by the oxide film layer formed on the surface of the ribbon.
- the oxide film layer formed on the surface of the ribbon located on the outer peripheral surface side with respect to the radial direction of the magnetic core may be affected by the ambient environment during the manufacturing process of the magnetic core.
- the specific oxide film layer is stably formed regardless of the surrounding environment on the surface of the ribbon located near the radially intermediate portion of the magnetic core or on the ribbon located slightly toward the inner peripheral surface of the intermediate portion. is. Therefore, in order to evaluate the structure of the oxide film that contributes to the improvement of the magnetic permeability, the ribbon located near the intermediate portion between the inner peripheral surface and the outer peripheral surface or the ribbon located slightly closer to the inner peripheral surface than the vicinity of the intermediate portion It is necessary to analyze the oxide film layer formed on the surface of
- FIG. 3(a) is a perspective view of an Fe-based nanocrystalline alloy magnetic core
- FIG. 3(b) is a cross-sectional perspective view of the Fe-based nanocrystalline alloy magnetic core.
- the Fe-based nanocrystalline alloy magnetic core 10 according to this embodiment is a magnetic core formed by winding a ribbon in a toroidal shape. The ribbon is laminated between the inner peripheral surface 11 and the outer peripheral surface 12 of the Fe-based nanocrystalline alloy magnetic core 10 by being wound.
- FIG. 3B the radial length between the inner peripheral surface 11 and the outer peripheral surface 12 of the Fe-based nanocrystalline alloy magnetic core 10 is virtually divided into three regions.
- the first region 21, the second region 22, and the third region 23 are regions that divide the radial length between the inner peripheral surface 11 and the outer peripheral surface 12 into l1 / l2 / l3 .
- l 1 /l 2 /l 3 are typically 40/20/40, may be 40/15/45, or may be 45/10/45.
- XPS analysis cuts out this second region 22, that is, the ribbon located in the central portion between the inner peripheral surface 11 and the outer peripheral surface 12 of the Fe-based nanocrystalline alloy magnetic core 10, and , the surface facing the outer peripheral surface 12 when wound is the analysis surface. In the XPS analysis, photoelectron intensity is measured for each depth from the ribbon surface while sputtering the analysis surface. An example of XPS analysis conditions is shown below.
- the Fe-based nanocrystalline alloy magnetic core manufactured by the manufacturing method according to the first embodiment of the present invention and the Fe-based nanocrystalline alloy magnetic core according to the second embodiment of the present invention include a reactor, a common mode choke coil, a transformer, It can be suitably used as a pulse transformer for communication, a magnetic core for a motor or a generator.
- An Fe-based alloy ribbon having a width of 12.5 mm and a thickness of 14 ⁇ m made of an Fe—Si—B—Cu—Nb alloy having a composition represented by the general formula (I) is wound, and has an outer diameter of 25 mm and an inner diameter of 15 mm. and a Fe-based alloy magnetic core material with a height of 12.5 mm.
- the crystallization initiation temperature of the Fe-based alloy forming the Fe-based alloy ribbon was 516° C. as determined by measurement with a differential scanning calorimeter (DSC).
- the Fe-based alloy magnetic core material was placed in a heat treatment furnace and heated at a maximum temperature of 440° C. for 180 minutes in an oxidizing atmosphere with an oxygen concentration of 0.4 vol % to form an oxide film.
- the Fe-based alloy magnetic core material after the oxide film formation step is placed in a heat treatment furnace, heated at 470° C. for 120 minutes in a nitrogen atmosphere (oxygen concentration 0 vol%), and further heated at 550° C. for 100 minutes to convert the Fe-based alloy. nanocrystallization was performed.
- An Fe-based nanocrystalline alloy magnetic core of Example 1 was obtained by cooling the magnetic core material after nanocrystallization to room temperature (20° C.).
- Example 2 Magnetic field application step
- the Fe-based nanocrystalline alloy magnetic core obtained in Example 1 is placed in a heat treatment furnace, and a magnetic field with a magnetic field strength of 100 mT is applied to the magnetic core in the height direction of the magnetic core while heat treating in a nitrogen atmosphere (oxygen concentration 0 vol%). applied.
- An Fe-based nanocrystalline alloy magnetic core was obtained by cooling the magnetic core to room temperature (20° C.) after applying the magnetic field. Note that the heat treatment was performed under the condition that the maximum temperature was 450° C. and the holding time was 30 minutes.
- the Fe-based nanocrystalline alloy magnetic core (Comparative Example 1) obtained by simultaneously advancing the formation of an oxide film and nanocrystallization was obtained only by performing nanocrystallization without forming an oxide film. It was confirmed that the relative magnetic permeability at a frequency of 10 kHz is lower than that of the Fe-based nanocrystalline alloy core (Comparative Example 3), and that the formation of the oxide film reduces the magnetic permeability of the Fe-based nanocrystalline alloy core in the low frequency region.
- the Fe-based nanocrystalline alloy magnetic core obtained by forming an oxide film under conditions in which nanocrystallization does not occur, and then performing nanocrystallization in a non-oxidizing atmosphere in which an oxide film is not formed, Similar to the Fe-based nanocrystalline alloy magnetic core obtained in Comparative Example 1, although it has an oxide film, the relative magnetic permeability at a frequency of 10 kHz is significantly improved, and the Fe-based nanocrystalline alloy obtained in Comparative Example 3. The value was higher than that of the alloy magnetic core. From these results, contrary to the common technical knowledge that if the oxide film formation and nanocrystallization are performed separately in this order, the magnetic permeability of the nanocrystalline alloy magnetic core in the low frequency region decreases due to the formation of the oxide film.
- the relative magnetic permeability at a frequency of 100 kHz of the Fe-based nanocrystalline alloy magnetic core (Example 2) obtained by sequentially performing oxide film formation, nanocrystallization, and magnetic field application It was as high as the Fe-based nanocrystalline alloy magnetic core (Comparative Example 2) obtained by applying a magnetic field to the magnetic core material produced by simultaneously performing crystallization. From this result, it can be seen that an Fe-based nanocrystalline alloy magnetic core exhibiting high magnetic permeability even in a high frequency region can be manufactured by performing the magnetic field application step.
- Example 2 in which an oxide film was formed prior to nanocrystallization and then nanocrystallization was performed in a non-oxidizing atmosphere, the first oxide film layer and the second oxide film layer were the same. It can be seen that it has a thickness of about.
- Comparative Example 2 in which an oxide film was formed while performing nanocrystallization, and in Comparative Example 4 in which the oxide film forming step was not performed and nanocrystallization was also performed in a non-oxidizing atmosphere, the first oxide film layer was It can be seen that the thickness is more than double that of the second oxide film layer.
- Comparative Example 4 since no oxide film was intentionally formed, the oxide film layer formed on the ribbon surface was due to natural oxidation. Therefore, the total thickness of the two oxide film layers of Comparative Example 4 is less than 5 nm, which is greater than the total thickness of the first oxide film layer and the second oxide film layer of Example 2 in which the oxide film was intentionally formed. It was significantly thinner.
- a Cu 2p peak (maximum value) was observed near a depth of 2.27 nm, which corresponds to the first oxide film layer, corresponding to the first oxide film layer. It was found that the intensity of the Cu 2p peak is stronger than that of the SiO2 -derived O 1S in the depth range where In addition, in the depth profile of Example 2, peaks of O 1S and Si 2p derived from SiO 2 were observed near a depth of 11.35 nm corresponding to the second oxide film layer, and the depth corresponding to the second oxide film layer was observed. It was found that the intensity of the O 1S peak derived from SiO 2 is stronger than that of Cu 2p in the low range. Furthermore, the intensity of the Cu 2p peak in the depth range corresponding to the first oxide film layer was stronger than the intensity of the Cu 2p peak in the depth range corresponding to the base material.
- Fe-based nanocrystalline alloy magnetic core 11 inner peripheral surface 12 outer peripheral surface 21 first region 22 second region 23 third region
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Abstract
Description
Fe基ナノ結晶合金の代表的な組成として、Feを主成分とするFe-Si-B-Cu-Nb系のナノ結晶の磁性材料が知られている(特許文献1)。このような磁性材を用いたコイルや磁心は、一般的に、ナノ結晶化可能なFe基非晶質合金のリボンを巻回して円柱状の巻磁心を形成し、熱処理することにより得られる。
例えば、特許文献2、3には、非晶質磁性合金のリボンを巻回又は積層してなる磁心において、磁性リボンの表面に酸化皮膜を形成することで、高周波領域における透磁率を向上する技術が開示されている。この技術は、磁性リボンを巻回又は積層してなる磁心のリボン層間を酸化皮膜により絶縁することにより、リボン層間を流れる渦電流の発生を抑制して渦電流損失を低減せしめ、その結果、透磁率が向上するというものである。
また、特許文献4には、ナノ結晶合金材料を用いた磁心に熱処理を施しながら磁場を印加することにより結晶磁気異方性を調整し、透磁率を向上する技術が開示されている。
ナノ結晶合金磁性リボンを巻回又は積層してなる磁心においても、磁性リボンの表面に酸化皮膜を形成することによりリボン層間に流れる渦電流の発生が抑制され、高周波領域における透磁率を向上させることができる。しかしながら、ナノ結晶合金磁心においては、特許文献2、3に記載されているような非晶質合金磁心と異なり、酸化皮膜の形成により低周波領域における透磁率が低下する傾向がある。ナノ結晶合金磁心においても、磁場印加により低周波領域における透磁率を向上させることは可能であるものの、その向上の程度は十分でないという問題が残されている。
ナノ結晶化可能なFe基合金のリボンが巻回されてなる磁心材を酸化雰囲気下で熱処理する酸化皮膜形成工程、及び
前記酸化皮膜形成工程後の磁心材を非酸化雰囲気下で熱処理することにより前記ナノ結晶化可能なFe基合金のナノ結晶化を行うナノ結晶化工程を含み、
前記酸化皮膜形成工程における前記熱処理の最高温度が、前記ナノ結晶化可能なFe基合金の結晶化開始温度未満の温度であり、
前記ナノ結晶化工程における前記熱処理の最高温度が、前記ナノ結晶化可能なFe基合金の結晶化開始温度以上の温度である、Fe基ナノ結晶合金磁心の製造方法。
[2]
前記ナノ結晶化工程後の磁心材に熱処理を施しながら前記磁心材の高さ方向の磁場を印加する磁場印加工程を含み、
前記磁場印加工程における前記熱処理の最高温度が、前記ナノ結晶化可能なFe基合金の結晶化開始温度未満の温度である、[1]に記載のFe基ナノ結晶合金磁心の製造方法。
[3]
前記ナノ結晶化可能なFe基合金が、下記一般式(I)で表される組成を有する、[1]又は[2]に記載のFe基ナノ結晶合金磁心の製造方法。
FexSiaBbCucNbd (I)
(一般式(I)中、a~d(原子%)は、それぞれ、3.0≦a≦12.0、1.0≦b≦7.0、1.0≦c≦5.0及び1.0≦d≦9.0を表し;x(原子%)は、Si,B,Cu,Nb以外の残部であって、73.0≦x≦92.0を満たす。)
[4]
リボンが巻回されてなる磁心であって、
前記リボンは、第1酸化皮膜層、第2酸化皮膜層、及び非晶質相と結晶粒とを含むFe基ナノ結晶合金で形成された母材をこの順に有し、
前記Fe基ナノ結晶合金が、下記一般式(I)で表される組成を有し、
下記試料XのX線光電子分光法による深さプロファイルにおいて、下記(A)及び(B)を満たす、Fe基ナノ結晶合金磁心。
FexSiaBbCucNbd (I)
(一般式(I)中、a~d(原子%)は、それぞれ、3.0≦a≦12.0、1.0≦b≦7.0、1.0≦c≦5.0及び1.0≦d≦9.0を表し;x(原子%)は、Si,B,Cu,Nb以外の残部であって、73.0≦x≦92.0を満たす。)
(A)前記第1酸化皮膜層に相当する深さ範囲にCu2pのピークが現れる。
(B)前記第1酸化皮膜層に相当する深さ範囲において、Cu2pピークの強度が、SiO2由来のO1Sの強度よりも強い。
(試料X)前記Fe基ナノ結晶合金磁心の内周面と外周面との間を、前記内周面から前記外周面に向かって第1領域、第2領域、及び第3領域の3つの領域に仮想的に分割したときに、前記第2領域内に位置するリボンを切り出して試料とする。前記第1領域、前記第2領域、及び前記第3領域は、前記内周面と前記外周面との間の径方向長さを40/20/40に分割する領域である。X線光電子分光分析は、試料の表面のうち、巻回され前記Fe基ナノ結晶合金磁心を形成していた際に前記外周面に対向していた方の表面に対して行われる。
[5]
前記深さプロファイルにおいて、さらに下記(C)及び(D)を満たす、[4]に記載のFe基ナノ結晶合金磁心。
(C)前記第2酸化皮膜層に相当する深さ範囲にSiO2由来のO1S及びSi2pのピークが現れる。
(D)前記第2酸化皮膜層に相当する深さ範囲において、SiO2由来のO1Sのピークの強度が、Cu2pの強度よりも強い。
[6]
前記深さプロファイルにおいて、さらに下記(E)を満たす、[4]又は[5]に記載のFe基ナノ結晶合金磁心。
(E)前記第1酸化皮膜層に相当する深さ範囲におけるCu2pピークの強度が、前記母材に相当する深さ範囲におけるCu2pの強度よりも強い。
また、本発明の好適な態様によれば、低周波領域及び高周波領域のいずれにおいても高い透磁率を示すFe基ナノ結晶合金磁心を製造する方法を提供することができる。
さらには、本発明によれば、上記製造方法により、低周波領域において高い透磁率を示すFe基ナノ結晶合金磁心を提供することができる。
なお、本明細書において、「~」を用いてその前後に数値又は物性値を挟んで表現する場合、その前後の値を含むものとして用いることとする。
本発明の第1の実施形態に係るFe基ナノ結晶合金磁心の製造方法は、ナノ結晶化可能なFe基合金のリボンが巻回されてなる磁心材を酸化雰囲気下で熱処理する酸化皮膜形成工程、及び酸化皮膜形成工程後の磁心材を非酸化雰囲気下で熱処理することによりナノ結晶化可能なFe基合金のナノ結晶化を行うナノ結晶化工程を含む。ここで、酸化皮膜形成工程における熱処理の最高温度は、ナノ結晶化可能なFe基合金の結晶化開始温度未満の温度であり、ナノ結晶化工程における熱処理の最高温度は、ナノ結晶化可能なFe基合金の結晶化開始温度以上の温度である。
本明細書において、低周波領域の透磁率は、周波数10kHzにおける透磁率に基づいて評価する。また、高周波領域の透磁率は、周波数100kHzにおける透磁率に基づいて評価する。
μr=μ/μ0 (1)
μr:比透磁率
μ0:真空の透磁率=4π×10-7[H/m]
μ:透磁率[H/m]=Ll/A/N2
L:インダクタンス[H]
l:磁路長[m]
A:コア有効断面積[m2]
N:巻き数
従来の製造方法では、酸化雰囲気下で熱処理を行うことにより、酸化皮膜の形成とナノ結晶化とが同時に進行する。これに対し、本実施形態に係る製造方法は、酸化皮膜形成工程においてナノ結晶化を生じさせることなく酸化皮膜を形成し、ナノ結晶化工程において透磁率に影響を与える程度の酸化皮膜を形成することなくFe基合金のナノ結晶化を行う方法である。本発明者らは、本実施形態に係る製造方法では、このように酸化皮膜の形成とナノ結晶化とをこの順に別々に行い、酸化皮膜の形成とナノ結晶化とが同時に進行しないようにすることで、低周波領域における透磁率を向上できるものと推測している。
酸化皮膜形成工程は、ナノ結晶化可能なFe基合金(以下、単に「Fe基合金」と称することがある。)のリボンが巻回されてなる磁心材を酸化雰囲気下で熱処理することにより、Fe基合金リボンの表面に酸化皮膜を形成する工程である。酸化皮膜形成工程における熱処理の最高温度は、Fe基合金の結晶化開始温度未満の温度である。
一般式(I)中、a~d(原子%)は、それぞれ、3.0≦a≦12.0、1.0≦b≦7.0、1.0≦c≦5.0及び1.0≦d≦9.0を表し;x(原子%)は、Si,B,Cu,Nb以外の残部であって、73.0≦x≦92.0を満たす。なお、この残部は不可避的不純物が含まれていてもよい。
上記超急冷法においては、急冷時の溶湯の温度は、合金の融点よりも50℃~300℃高い程度の温度とすることが望ましい。超急冷法としては、特に制限されず、単ロール法、双ロール法、回転液中防止法、ガスアトマイズ法、水アトマイズ法等の公知の方法を採用することができる。超急冷法によるFe基合金リボンの作製は、大気等の酸化雰囲気下で行ってもよく、アルゴン、ヘリウム、窒素等の不活性ガス雰囲気下で行ってもよく、真空条件下で行ってもよい。
上記最高温度に至るまでの昇温速度、及び当該最高温度での保持を終えた後の降温速度は、本発明の効果を阻害しない限り特に限定されず、本発明の技術分野における熱処理に一般的に採用される速度を適用することができる。
上記最高温度での保持時間は、酸化雰囲気の種類、熱処理温度等にもよるが、通常1時間以上、好ましくは2時間以上、より好ましくは3時間以上であり、また、通常30時間以下、好ましくは20時間以下、より好ましくは10時間以下である。すなわち、上記最高温度での保持時間の好適な範囲としては、1時間以上20時間以下、2時間以上30時間以下、及び3時間以上10時間以下の範囲が挙げられる。
ナノ結晶化工程は、酸化皮膜形成工程後の磁心材を非酸化雰囲気下で熱処理することによりナノ結晶化可能なFe基合金のナノ結晶化を行う工程である。ナノ結晶化工程における熱処理の最高温度は、ナノ結晶化可能なFe基合金の結晶化開始温度以上の温度である。ナノ結晶化工程により、結晶相(bcc相)からなる結晶粒と非晶質相とを含むFe基ナノ結晶合金が形成される。
上記最高温度に至るまでの昇温速度、及び当該最高温度での保持を終えた後の降温速度は、本発明の効果を阻害しない限り特に限定されず、本発明の技術分野における熱処理に一般的に採用される速度を適用することができる。
上記最高温度での保持時間は、Fe基合金の組成、磁心のサイズ等にもよるが、合金全体を均一に加熱する観点及び生産性の観点から、通常30分以上、好ましくは50分以上、より好ましくは90分以上であり、また、通常10時間以下、好ましくは2時間以下である。すなわち、上記最高温度での保持時間の好適な範囲としては、30分以上2時間以下、50分以上10時間以下、及び90分以上10時間以下の範囲が挙げられる。
Fe基合金のナノ結晶化おいてオーバーシュートが生じると、熱処理炉の設定温度以上の温度が磁心に加わることで結晶相の析出が過剰に進行し、Fe基ナノ結晶合金磁心の透磁率にばらつきが生じる虞がある。ここで、ナノ結晶化の前に保温工程を行うと、Fe基合金リボンが巻回された磁心材に加わる熱エネルギー量が抑制されるため、結晶相の析出速度が緩やかになり、結晶相の析出に伴う自己発熱が抑制される。その結果、オーバーシュートが抑制され、ひいてはFe基ナノ結晶合金磁心の透磁率のばらつきが抑制されると推測される。
保温工程における熱処理時間は、保温工程における熱処理温度、磁心材のサイズ等にもよるが、熱処理炉内の温度を均一化する観点から、通常30分以上、好ましくは60分以上、より好ましくは100分以上であり、また、通常5時間以下、好ましくは4時間以下、より好ましくは3時間以下である。すなわち、熱処理時間の好適な範囲としては、30分以上4時間以下、60分以上5時間以下、及び100分以上3時間以下の範囲が挙げられる。上記熱処理時間経過後、すなわち保温工程終了後は、ナノ結晶化工程における熱処理の最高温度まで昇温し、Fe基合金のナノ結晶化を十分に進行させる。
本実施形態に係る製造方法は、ナノ結晶化工程後の磁心材に熱処理を施しながら磁心材の高さ方向の磁場を印加する磁場印加工程をさらに含んでいてもよい。高周波領域におけるFe基ナノ結晶合金磁心の透磁率を向上させる観点からは、磁場印加工程を行うことが好ましい。
上記最高温度に至るまでの昇温速度、及び当該最高温度での保持を終えた後の降温速度は、本発明の効果を阻害しない限り特に限定されず、本発明の技術分野における熱処理に一般的に採用される速度を適用することができる。
上記最高温度での保持時間は、上記最高温度、磁心材のサイズ等にもよるが、熱処理炉内の温度を均一化する観点から、通常20分以上、好ましくは30分以上であり、また、通常5時間以下、好ましくは2時間以下、より好ましくは1時間以下である。すなわち、上記最高温度での保持時間の好適な範囲としては、20分以上2時間以下、30分以上5時間以下、及び30分以上1時間以下の範囲が挙げられる。
本発明の第2の実施形態に係るFe基ナノ結晶合金磁心は、リボンが巻回されてなる磁心であって、前記リボンは、第1酸化皮膜層、第2酸化皮膜層、及び非晶質相と結晶粒とを含むFe基ナノ結晶合金で形成された母材をこの順に有し、前記Fe基ナノ結晶合金が、下記一般式(I)で表される組成を有する。本実施形態に係るFe基ナノ結晶合金磁心からサンプリングした特定試料について、X線光電子分光法(XPS)分析を行うと、後述する特徴的な深さプロファイルが得られる。
一般式(I)は、上記<1-1.酸化皮膜形成工程>で述べた一般式(I)と同一である。したがって、a~d(原子%)及びx(原子%)の定義及び好ましい態様は、<1-1.酸化皮膜形成工程>で説明した通りである。
本実施形態に係るFe基ナノ結晶合金磁心は、本発明の第1の実施形態に係る製造方法で製造されるものであるため、磁心を構成するリボンは、第1酸化皮膜層、第2酸化皮膜層、及び非晶質相と結晶粒とを含むFe基ナノ結晶合金で形成された母材をこの順に有する。第1酸化皮膜層は、リボンの最表面層である。
第1酸化皮膜層及び第2酸化皮膜層は、上記製造方法における酸化皮膜形成工程により形成されるものである。また、母材は、上記製造方法におけるナノ結晶化工程で、一般式(I)で表される組成を有するナノ結晶化可能なFe-Si-B-Cu-Nb系合金がナノ結晶化されることにより形成されるものである。母材は、Fe基ナノ結晶合金以外の成分、例えば、リボンを作成する工程及び酸化皮膜形成工程等で混入した成分を含んでいてもよい。
・装置:JEM-2100(日本電子株式会社製)
・加速電圧:200kV
・倍率:10万倍又は20万倍
本実施形態に係るFe基ナノ結晶合金磁心は、第1酸化皮膜層、第2酸化皮膜層、及び母材を含むリボンの表面構造のXPS分析を行うと、下記(A)及び(B)を満たす特徴的な深さプロファイルが得られる。
(B)第1酸化皮膜層に相当する深さ範囲において、Cu2pピークの強度が、SiO2由来のO1Sの強度よりも強い。
(C)第2酸化皮膜層に相当する深さ範囲にSiO2由来のO1S及びSi2pのピークが現れる。
(D)第2酸化皮膜層に相当する深さ範囲において、SiO2由来のO1Sのピークの強度が、Cu2pの強度よりも強い。
(E)第1酸化皮膜層に相当する深さ範囲におけるCu2pピークの強度が、母材に相当する深さ範囲におけるCu2pの強度よりも強い。
(試料X)Fe基ナノ結晶合金磁心の内周面と外周面との間を、内周面から外周面に向かって第1領域、第2領域、及び第3領域の3つの領域に仮想的に分割したときに、第2領域内に位置するリボンを切り出して試料とする。第1領域、第2領域、及び第3領域は、内周面と外周面との間の径方向長さを40/20/40に分割する領域である。X線光電子分光分析は、試料の表面のうち、巻回されFe基ナノ結晶合金磁心を形成していた際に外周面に対向していた方の表面に対して行われる。
リボンを巻回してなる磁心においては、透磁率は、磁心の径方向に対して内周面と外周面との中間部近傍に位置するリボン又は該中間部近傍より若干内周面側に位置するリボンの表面に形成された酸化皮膜層の影響を受ける。さらに、磁心の径方向に対して外周面側に位置するリボンの表面に形成される酸化皮膜層は、磁心の製造工程における周囲環境下の影響を受ける場合がある。そのため、周囲環境に関係なく特定の酸化皮膜層が安定的に形成されるのは、磁心の径方向中間部近傍に位置するリボン又は該中間近傍より若干内周面側に位置するリボンの表面上である。したがって、透磁率の向上に寄与する酸化皮膜の構成を評価するためには、内周面と外周面との中間部近傍に位置するリボン又は該中間部近傍より若干内周面側に位置するリボンの表面に形成された酸化皮膜層を分析する必要がある。
・装置:PHI5000VersaProbe(アルバック・ファイ株式会社製)
・到達真空度:6.7×10-8Pa以下
・励起源:モノクロAl-Kα X線
・出力:25W
・検出面積:100μmφ
・入射角:45°
・取り出し角:45°
(スパッタ条件)
・イオン種:アルゴン
・加速電圧:1kV
・掃引面積:2mm×2mm
・スパッタリングレート:2.27nm/min
本発明の第1の実施形態に係る製造方法により製造されるFe基ナノ結晶合金磁心及び本発明の第2の実施形態に係るFe基ナノ結晶合金磁心は、リアクトル、コモンモードチョークコイル、トランス、通信用パルストランス、モータ又は発電機用の磁心として好適に使用できる。
上記一般式(I)で表される組成を有するFe-Si-B-Cu-Nb系合金からなる、幅12.5mm及び厚さ14μmのFe基合金リボンを巻回し、外径25mm、内径15mm及び高さ12.5mmのFe基合金磁心材を作製した。なお、Fe基合金リボンを構成するFe基合金の結晶化開始温度を示差走査熱量計(DSC)での測定により求めたところ、516℃であった。
Fe基合金磁心材を熱処理炉に配置し、酸素濃度0.4vol%の酸化雰囲気下、最高温度440℃で180分加熱することにより酸化皮膜の形成を行った。
酸化皮膜形成工程後のFe基合金磁心材を熱処理炉に配置し、窒素雰囲気下(酸素濃度0vol%)、470℃で120分加熱し、さらに550℃で100分加熱することによりFe基合金のナノ結晶化を行った。ナノ結晶化後の磁心材を室温(20℃)まで降温することで、実施例1のFe基ナノ結晶合金磁心を得た。
(磁場印加工程)
実施例1で得られたFe基ナノ結晶合金磁心を熱処理炉に配置し、窒素雰囲気下(酸素濃度0vol%)で熱処理しながら、磁心に対して磁心の高さ方向に磁場強度100mTの磁場を印加した。磁場印加後の磁心を室温(20℃)まで降温することで、Fe基ナノ結晶合金磁心を得た。なお、熱処理は、最高温度450℃での保持時間が30分となる条件で行った。
酸化皮膜形成工程を行わなかったこと、及びナノ結晶化工程を酸素濃度0.4vol%の酸化雰囲気下で行ったこと以外は実施例1と同様にしてFe基ナノ結晶合金磁心を得た。
酸化皮膜形成工程を行わなかったこと、及びナノ結晶化工程を酸素濃度0.4vol%の酸化雰囲気下で行ったこと以外は実施例2と同様にしてFe基ナノ結晶合金磁心を得た。
酸化皮膜形成工程を行わなかったこと以外は実施例1と同様にしてFe基ナノ結晶合金磁心を得た。
酸化皮膜形成工程を行わなかったこと以外は実施例2と同様にしてFe基ナノ結晶合金磁心を得た。
実施例及び比較例で得たFe基ナノ結晶合金磁心を樹脂ケースに装填し、中空状のコアを作製した。作成したコアの中空部分に線径0.5mmの被膜銅線を貫通させて1ターンのコアを作製した。インピーダンス・アナライザ(Agilent Technologies社製,4294A)を用い、周波数10kHz及び100kHzにおいて、得られたコアのインダクタンスを測定し、下記式(1)に基づいてFe基ナノ結晶合金磁心の比透磁率を算出した。なお、磁路長lは6.3×10-2m、有効断面積Aは4.8×10-5m2、及び巻き数Nは1とした。結果を表1、図1、及び図2に示す。
μr:比透磁率
μ0:真空の透磁率=4π×10-7[H/m]
μ:透磁率[H/m]=Ll/A/N2
L:インダクタンス[H]
l:磁路長[m]=6.3×10-2[m]
A:コア有効断面積[m2]=4.8×10-5[m2]
N:巻き数=1
一方、ナノ結晶化が生じない条件で酸化皮膜の形成を行い、その後、酸化皮膜が形成されない非酸化雰囲気下でナノ結晶化を行って得たFe基ナノ結晶合金磁心(実施例1)は、比較例1で得たFe基ナノ結晶合金磁心と同様、酸化皮膜を有するものであるにも拘わらず、周波数10kHzにおける比透磁率は著しく向上しており、比較例3で得たFe基ナノ結晶合金磁心よりも高い値であった。
これらの結果から、酸化皮膜形成及びナノ結晶化をこの順に別々に行うと、酸化皮膜の形成により低周波領域におけるナノ結晶合金磁心の透磁率が低下するという技術常識に反し、低周波領域におけるFe基ナノ結晶合金磁心の透磁率が向上することが示された。
また、表1及び図1より、磁場印加を行うことによっても、低周波領域におけるFe基ナノ結晶合金磁心の透磁率が向上することが確認された。
この結果から、磁場印加工程を行うことにより、高周波領域においても高い透磁率を示すFe基ナノ結晶合金磁心を製造できることがわかる。
実施例2、比較例2、及び比較例4で得たFe基ナノ結晶合金磁心から、XPS分析用の試料Xと同条件のリボンを切り出した(ただし、l1/l2/l3=45/10/45)。次いで、リボンの両表面のうち、XPS分析の分析面と同条件の表面の上に、デポジション方式で保護層を形成した。この保護層で被覆されたリボンを、表面に垂直に切断することで、TEM観察用の試料を得た。得られたTEM観察用の試料について、下記測定条件でTEMの測定を行った。得られたTEM像を図4に示す。
・装置:JEM-2100(日本電子株式会社製)
・加速電圧:200kV
・倍率:10万倍(実施例2、比較例4)又は20万倍(比較例2)
実施例2、比較例2、及び比較例4で得たFe基ナノ結晶合金磁心から、第2領域内(l1/l2/l3=45/10/45)に位置するリボンを切り出し、試料Xとした。この試料Xの両表面のうち、巻回され磁心を形成していた際に外周面に対向していた方の表面を分析面とし、この分析面をスパッタリングしながらXPS分析を行うことで、深さプロファイルを取得した。XPS分析条件は、下記の通りである。結果を図5~図7に示す。図5~図7においては、XPS分析のチャートにおける横軸を、スパッタ時間からSiO2標準試料のスパッタエッチングレートを用いて算出したSiO2換算の深さ(nm)とした。
・装置:PHI5000VersaProbe(アルバック・ファイ株式会社製)
・到達真空度:6.7×10-8Pa以下
・励起源:モノクロAl-Kα X線
・出力:25W
・検出面積:100μmφ
・入射角:45°
・取り出し角:45°
(スパッタ条件)
・イオン種:アルゴン
・加速電圧:1kV
・掃引面積:2mm×2mm
・スパッタリングレート:2.27nm/min
11 内周面
12 外周面
21 第1領域
22 第2領域
23 第3領域
Claims (6)
- ナノ結晶化可能なFe基合金のリボンが巻回されてなる磁心材を酸化雰囲気下で熱処理する酸化皮膜形成工程、及び
前記酸化皮膜形成工程後の磁心材を非酸化雰囲気下で熱処理することにより前記ナノ結晶化可能なFe基合金のナノ結晶化を行うナノ結晶化工程を含み、
前記酸化皮膜形成工程における前記熱処理の最高温度が、前記ナノ結晶化可能なFe基合金の結晶化開始温度未満の温度であり、
前記ナノ結晶化工程における前記熱処理の最高温度が、前記ナノ結晶化可能なFe基合金の結晶化開始温度以上の温度である、Fe基ナノ結晶合金磁心の製造方法。 - 前記ナノ結晶化工程後の磁心材に熱処理を施しながら前記磁心材の高さ方向の磁場を印加する磁場印加工程を含み、
前記磁場印加工程における前記熱処理の最高温度が、前記ナノ結晶化可能なFe基合金の結晶化開始温度未満の温度である、請求項1に記載のFe基ナノ結晶合金磁心の製造方法。 - 前記ナノ結晶化可能なFe基合金が、下記一般式(I)で表される組成を有する、請求項1又は2に記載のFe基ナノ結晶合金磁心の製造方法。
FexSiaBbCucNbd (I)
(一般式(I)中、a~d(原子%)は、それぞれ、3.0≦a≦12.0、1.0≦b≦7.0、1.0≦c≦5.0及び1.0≦d≦9.0を表し;x(原子%)は、Si,B,Cu,Nb以外の残部であって、73.0≦x≦92.0を満たす。) - リボンが巻回されてなる磁心であって、
前記リボンは、第1酸化皮膜層、第2酸化皮膜層、及び非晶質相と結晶粒とを含むFe基ナノ結晶合金で形成された母材をこの順に有し、
前記Fe基ナノ結晶合金が、下記一般式(I)で表される組成を有し、
下記試料XのX線光電子分光法による深さプロファイルにおいて、下記(A)及び(B)を満たす、Fe基ナノ結晶合金磁心。
FexSiaBbCucNbd (I)
(一般式(I)中、a~d(原子%)は、それぞれ、3.0≦a≦12.0、1.0≦b≦7.0、1.0≦c≦5.0及び1.0≦d≦9.0を表し;x(原子%)は、Si,B,Cu,Nb以外の残部であって、73.0≦x≦92.0を満たす。)
(A)前記第1酸化皮膜層に相当する深さ範囲にCu2pのピークが現れる。
(B)前記第1酸化皮膜層に相当する深さ範囲において、Cu2pピークの強度が、SiO2由来のO1Sの強度よりも強い。
(試料X)前記Fe基ナノ結晶合金磁心の内周面と外周面との間を、前記内周面から前記外周面に向かって第1領域、第2領域、及び第3領域の3つの領域に仮想的に分割したときに、前記第2領域内に位置するリボンを切り出して試料とする。前記第1領域、前記第2領域、及び前記第3領域は、前記内周面と前記外周面との間の径方向長さを40/20/40に分割する領域である。X線光電子分光分析は、試料の表面のうち、巻回され前記Fe基ナノ結晶合金磁心を形成していた際に前記外周面に対向していた方の表面に対して行われる。 - 前記深さプロファイルにおいて、さらに下記(C)及び(D)を満たす、請求項4に記載のFe基ナノ結晶合金磁心。
(C)前記第2酸化皮膜層に相当する深さ範囲にSiO2由来のO1S及びSi2pのピークが現れる。
(D)前記第2酸化皮膜層に相当する深さ範囲において、SiO2由来のO1Sのピークの強度が、Cu2pの強度よりも強い。 - 前記深さプロファイルにおいて、さらに下記(E)を満たす、請求項4又は5に記載のFe基ナノ結晶合金磁心。
(E)前記第1酸化皮膜層に相当する深さ範囲におけるCu2pピークの強度が、前記母材に相当する深さ範囲におけるCu2pの強度よりも強い。
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JPH02236259A (ja) * | 1989-03-09 | 1990-09-19 | Hitachi Metals Ltd | 恒透磁率性に優れた合金およびその製造方法 |
JP2010189761A (ja) * | 2009-01-20 | 2010-09-02 | Hitachi Metals Ltd | 軟磁性合金薄帯及びその製造方法、並びに軟磁性合金薄帯を有する磁性部品 |
JP2011149045A (ja) * | 2010-01-20 | 2011-08-04 | Hitachi Metals Ltd | 軟磁性合金薄帯及びその製造方法、並びに軟磁性合金薄帯を有する磁性部品 |
JP2016197720A (ja) * | 2015-04-02 | 2016-11-24 | 日立金属株式会社 | 磁心およびその製造方法、並びに車載用部品 |
WO2019181107A1 (ja) * | 2018-03-23 | 2019-09-26 | 株式会社村田製作所 | 鉄合金粒子、及び、鉄合金粒子の製造方法 |
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JPH02236259A (ja) * | 1989-03-09 | 1990-09-19 | Hitachi Metals Ltd | 恒透磁率性に優れた合金およびその製造方法 |
JP2010189761A (ja) * | 2009-01-20 | 2010-09-02 | Hitachi Metals Ltd | 軟磁性合金薄帯及びその製造方法、並びに軟磁性合金薄帯を有する磁性部品 |
JP2011149045A (ja) * | 2010-01-20 | 2011-08-04 | Hitachi Metals Ltd | 軟磁性合金薄帯及びその製造方法、並びに軟磁性合金薄帯を有する磁性部品 |
JP2016197720A (ja) * | 2015-04-02 | 2016-11-24 | 日立金属株式会社 | 磁心およびその製造方法、並びに車載用部品 |
WO2019181107A1 (ja) * | 2018-03-23 | 2019-09-26 | 株式会社村田製作所 | 鉄合金粒子、及び、鉄合金粒子の製造方法 |
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