WO2016043295A1 - 磁性コアおよびその製造方法 - Google Patents

磁性コアおよびその製造方法 Download PDF

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Publication number
WO2016043295A1
WO2016043295A1 PCT/JP2015/076582 JP2015076582W WO2016043295A1 WO 2016043295 A1 WO2016043295 A1 WO 2016043295A1 JP 2015076582 W JP2015076582 W JP 2015076582W WO 2016043295 A1 WO2016043295 A1 WO 2016043295A1
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Prior art keywords
magnetic core
iron
temperature
thermosetting
epoxy resin
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Ceased
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PCT/JP2015/076582
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English (en)
French (fr)
Inventor
拓治 原野
浩行 野田
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NTN Corp
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NTN Corp
NTN Toyo Bearing Co Ltd
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Filing date
Publication date
Application filed by NTN Corp, NTN Toyo Bearing Co Ltd filed Critical NTN Corp
Priority to US15/512,823 priority Critical patent/US10537938B2/en
Priority to KR1020177009232A priority patent/KR102322977B1/ko
Priority to EP15842742.7A priority patent/EP3196897B1/en
Priority to CN201580050143.6A priority patent/CN106716562A/zh
Priority to CN202110369915.XA priority patent/CN113113221B/zh
Publication of WO2016043295A1 publication Critical patent/WO2016043295A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
    • B22F5/10—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of articles with cavities or holes, not otherwise provided for in the preceding subgroups
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B22F1/102—Metallic powder coated with organic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B22F1/103—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material containing an organic binding agent comprising a mixture of, or obtained by reaction of, two or more components other than a solvent or a lubricating agent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B22F1/105—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material containing inorganic lubricating or binding agents, e.g. metal salts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • B32B27/26—Layered products comprising a layer of synthetic resin characterised by the use of special additives using curing agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/38—Layered products comprising a layer of synthetic resin comprising epoxy resins
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K9/00—Use of pretreated ingredients
    • C08K9/02—Ingredients treated with inorganic substances
    • 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
    • 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
    • H01F1/20—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 in the form of particles, e.g. powder
    • H01F1/22—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 in the form of particles, e.g. powder pressed, sintered, or bound together
    • H01F1/24—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 in the form of particles, e.g. powder pressed, sintered, or bound together the particles being insulated
    • 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
    • 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
    • H01F1/20—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 in the form of particles, e.g. powder
    • H01F1/22—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 in the form of particles, e.g. powder pressed, sintered, or bound together
    • H01F1/24—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 in the form of particles, e.g. powder pressed, sintered, or bound together the particles being insulated
    • H01F1/26—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 in the form of particles, e.g. powder pressed, sintered, or bound together the particles being insulated by macromolecular organic substances
    • 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
    • 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
    • H01F1/33—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 mixtures of metallic and non-metallic particles; metallic particles having oxide skin
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/24—Magnetic cores
    • H01F27/255—Magnetic cores made from particles
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—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
    • 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
    • H01F41/0246—Manufacturing of magnetic circuits by moulding or by pressing powder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C2202/00—Physical properties
    • C22C2202/02—Magnetic
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F3/00—Cores, Yokes, or armatures
    • H01F3/08—Cores, Yokes, or armatures made from powder

Definitions

  • the present invention relates to a magnetic core and a manufacturing method thereof, and more particularly to an iron-based soft magnetic core attached to a heating coil portion of an induction hardening apparatus and a manufacturing method thereof.
  • the magnetic core can be attached to the back of the coil to concentrate magnetic lines of force on the workpiece to increase power and promote induction heating, and conversely, it can be attached to the front of the coil to shield the magnetic lines and prevent heating of parts that do not require quenching. It has an effect and is an indispensable part for the heating coil of the induction hardening apparatus. For example, when the shape of the workpiece to be induction hardened is complex and it is necessary to adjust the quenching depth, the state of induction heating is changed by changing the shape, size, quantity, direction, position, etc. of the core to be attached. It is possible to control the quenching depth of the workpiece.
  • This core material has (1) good frequency characteristics, that is, little change in inductance due to change in frequency, (2) high saturation magnetic flux density, (3) high relative permeability, ( 4) Magnetic properties such as low iron loss are required. Moreover, in order to cope with various workpiece shapes, core parts are often produced in a variety of small quantities, and are often produced by cutting one by one. For this reason, a material having high strength and excellent machinability is demanded.
  • a magnetic core produced by powder metallurgy is used frequently as a magnetic core used in a heating coil of an induction hardening apparatus because it has low material loss and excellent mass productivity.
  • magnetic cores for induction-hardened coils products in which magnetic powder is fixed with fluororesin or products in which sendust powder is fixed with phenolic resin are used. There were problems such as cracking at the time and damage at the time of coil installation.
  • Patent Document 1 a magnetic core in which an iron-based soft magnetic powder having a resin film formed on the particle surface is thermally cured after compression molding.
  • This magnetic core is a highly versatile magnetic core that is excellent in economic efficiency, magnetic characteristics, and material strength and is attached to the heating coil portion of the induction hardening apparatus.
  • the magnetic core attached to the heating coil portion of the induction hardening apparatus may be required to have an electrical insulating property of about 10 5 ⁇ ⁇ cm as a volume specific resistance value depending on the shape of the heating coil and the mounting form of the magnetic core.
  • the magnetic core described in Patent Document 1 is excellent in versatility but is insufficient in terms of electrical insulation. Therefore, depending on the usage, an electrical short circuit or heat generation occurs through the magnetic core. Durability may be significantly reduced. For this reason, there has been a problem that it is difficult to deploy in applications where insulation is required.
  • the present invention has been made to cope with such problems, and the advantages of the magnetic core described in Patent Document 1 are proposed as a magnetic core, particularly as a soft magnetic core attached to a heating coil portion of an induction hardening apparatus.
  • An object is to provide a magnetic core imparted with insulating properties while utilizing it and a method for producing the same.
  • the magnetic core of the present invention is a magnetic core produced by thermosetting an iron-based soft magnetic powder having a resin coating formed on the particle surface after compression molding.
  • the iron-based soft magnetic powder is an iron-based soft magnetic powder whose surface is treated with an inorganic insulating coating, and the resin coating is at a temperature not lower than the softening temperature of the thermosetting resin and lower than the thermosetting start temperature. It is an uncured resin film formed by dry mixing, and the compression molding is a production of a compression molded body using a mold, and the thermosetting is heated at a temperature equal to or higher than the thermosetting start temperature of the thermosetting resin. It is characterized by being cured.
  • the iron-based soft magnetic powder treated with the inorganic insulating coating is characterized by particles that pass through a sieve having a sieve opening of 106 ⁇ m and do not pass through the sieve of 25 ⁇ m.
  • the resin film formed on the particle surface of the iron-based soft magnetic powder is an epoxy resin containing a latent curing agent.
  • the latent curing agent is dicyandiamide
  • the epoxy resin containing the latent curing agent has a softening temperature of 100 to 120 ° C.
  • the total amount of the iron-based soft magnetic powder and the epoxy resin containing the latent hardener is 95 to 99% by mass of the iron-based soft magnetic powder, and 1 epoxy resin containing the latent hardener. It is characterized by blending up to 5% by mass.
  • the magnetic core of the present invention is a magnetic core used for an induction-hardened coil.
  • the method for producing a magnetic core according to the present invention includes an iron-based soft magnetic powder whose surface is treated with an inorganic insulating coating and an epoxy resin containing the latent curing agent at a temperature equal to or higher than the softening temperature of the epoxy resin.
  • a mixing step in which dry mixing is performed at a temperature lower than the thermosetting start temperature, a pulverizing step in which the agglomerated cake produced in the mixing step is pulverized at room temperature to obtain a composite magnetic powder, and the composite magnetic powder is compression molded using a mold.
  • the compression molding step is characterized by being molded at a molding pressure of 98 to 294 MPa.
  • the curing step is characterized in that the curing is performed at a curing temperature of 170 to 190 ° C. in an inert gas atmosphere.
  • the magnetic core according to the present invention has an electrical insulation property expressed by volume resistivity improved to 10 5 ⁇ ⁇ cm.
  • FIG. 1 It is a figure which shows the arrangement
  • the outer joint member of the constant velocity universal joint is manufactured from a cylindrical material through a forging process such as cold forging, and then induction-quenched.
  • This induction hardening may be performed by arranging a magnetic core on the front surface or the back surface of the high frequency coil in order to adjust the hardening degree of the induction hardening on the inner and outer surfaces and the shaft portion of the cup portion of the outer joint member. Many.
  • FIG. 1A is a view showing a case of using a magnetic core fitted in a frame of an annular or rectangular coil
  • FIG. 1B is a form of using a magnetic core attached to one end of the coil.
  • the coil 2 is composed of a copper pipe or plate having a low electrical resistance, and controls the magnetic flux in order to improve heating efficiency or adjust the heating part.
  • a magnetic core 1 is disposed. The magnetic core 1 can change the state of induction heating by concentrating the magnetic flux generated by the flow of the coil current 3a on the work or shielding it from the work.
  • FIG. 1A is a view showing a case of using a magnetic core fitted in a frame of an annular or rectangular coil
  • FIG. 1B is a form of using a magnetic core attached to one end of the coil.
  • the coil 2 is composed of a copper pipe or plate having a low electrical resistance, and controls the magnetic flux in order to improve heating efficiency or adjust the heating part.
  • a magnetic core 1 is disposed.
  • the magnetic core 1 can change the
  • a magnetic core having a large volume resistivity was formed by coating the surface of the magnetic powder, which is a raw material of the magnetic core, with an insulating material.
  • the organic insulating material or the inorganic material was individually coated, the volume resistivity was not greatly improved.
  • the organic insulating material and the inorganic material are formed into a plurality of layers, the volume resistivity is improved by 100,000 times or more as compared with the case of each single layer. The present invention is based on such knowledge.
  • FIG. 2 An example of a perspective view of a magnetic core is shown in FIG. 2, and a sectional view of composite magnetic powder particles as a raw material is shown in FIG.
  • the magnetic core 1 is obtained by compression-molding and heat-curing the composite magnetic powder particles 4.
  • the surface of the iron-based soft magnetic powder particle 4a is coated with an inorganic insulating coating 4b, and the surface of the inorganic insulating coating 4b is coated with an uncured resin coating 4c.
  • the magnetic core 1 is manufactured by compression-molding the composite magnetic powder particles 4 and then thermosetting the resin coating 4c. Thereafter, post-processing such as cutting, barrel processing and rust prevention is performed as necessary.
  • post-processing such as cutting, barrel processing and rust prevention is performed as necessary.
  • the shape of the magnetic core to be arranged can be changed as appropriate.
  • a magnetic core 1 shown in FIG. 2 is an example of a magnetic core that is used by being fitted into a frame of an annular or rectangular coil.
  • iron-based soft magnetic powder examples include pure iron, iron-silicon alloy, iron-nitrogen alloy, iron-nickel alloy, iron-carbon alloy, iron-boron alloy, iron-cobalt. Powders such as iron alloys, iron-phosphorus alloys, iron-nickel-cobalt alloys and iron-aluminum-silicon alloys (Sendust alloys) can be used.
  • the reduced iron powder is excellent in mechanical properties of the magnetic core obtained.
  • Reduced iron powder is iron powder produced by reducing iron oxide or the like generated in an iron factory with coke and then heat-treating in a hydrogen atmosphere, and has pores in the particles.
  • Atomized iron powder is iron powder produced by pulverizing and cooling molten steel with high-pressure water and then heat-treating in a hydrogen atmosphere, and there are no pores in the particles. In the cross-sectional photograph of the reduced iron powder, there are many irregularities on the surface, and these irregularities are thought to reduce the crushing strength.
  • the surface of the iron-based soft magnetic powder particles is coated with an inorganic insulator.
  • an inorganic insulator There is no limitation in particular in the kind of inorganic insulating material, The thing conventionally used in the dust core can be used.
  • preferable insulating materials include metal phosphates such as iron phosphate, manganese phosphate, zinc phosphate, calcium phosphate, and aluminum phosphate, metal oxides such as silicon oxide, magnesium oxide, aluminum oxide, titanium oxide, and zirconium oxide. Things. Other minerals can also be used.
  • the inorganic insulating material one kind of material may be used, or two or more kinds of materials may be used in combination.
  • a commercial product of iron-based soft magnetic powder coated with an inorganic insulator there is a trade name manufactured by Höganäs; Somaloy.
  • the iron-based soft magnetic powder whose surface has been treated with an inorganic insulating coating is preferably a particle whose sieve opening passes through a 106 ⁇ m sieve and does not pass through the 25 ⁇ m sieve.
  • a preferred range is particles that pass through 90 ⁇ m and do not pass through 38 ⁇ m. Fine powder that passes 25 ⁇ m makes it difficult to form a resin film on the surface of the iron particles, and iron powder that does not pass 106 ⁇ m increases iron loss.
  • the epoxy resin that can be used in the present invention is a resin that can be used as an adhesive epoxy resin and preferably has a softening temperature of 100 to 120 ° C.
  • an epoxy resin that is solid at room temperature becomes a paste at 50 to 60 ° C., becomes fluid at 130 to 140 ° C., and starts a curing reaction when further heated can be used.
  • This curing reaction starts even at around 120 ° C., but the temperature at which the curing reaction is completed within a practical curing time, for example within 2 hours, is preferably 170 to 190 ° C. In this temperature range, the curing time is 45 to 80 minutes.
  • Examples of the resin component of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, stilbene type epoxy resin, and triazine skeleton.
  • epoxy resin fluorene skeleton-containing epoxy resin, alicyclic epoxy resin, novolac-type epoxy resin, acrylic epoxy resin, glycidylamine-type epoxy resin, triphenolphenolmethane-type epoxy resin, alkyl-modified triphenolmethane-type epoxy resin, biphenyl-type
  • examples thereof include an epoxy resin, a dicyclopentadiene skeleton-containing epoxy resin, a naphthalene skeleton-containing epoxy resin, and an arylalkylene type epoxy resin.
  • the curing agent component of the epoxy resin is a latent epoxy curing agent.
  • the softening temperature can be set to 100 to 120 ° C. and the curing temperature can be set to 170 to 190 ° C., and the organic insulating coating on the iron powder powder treated with the inorganic insulating coating And subsequent compression molding and thermosetting.
  • the latent epoxy curing agent include dicyandiamide, boron trifluoride-amine complex, and organic acid hydrazide. Of these, dicyandiamide that meets the above-mentioned curing conditions is preferred.
  • hardening accelerators such as tertiary amine, an imidazole, and an aromatic amine, can be included with a latent epoxy hardening
  • the epoxy resin containing the latent curing agent that can be used in the present invention has curing conditions of 160 ° C. for 2 hours, 170 ° C. for 80 minutes, 180 ° C. for 55 minutes, 190 ° C. for 45 minutes, and 200 ° C. for 30 minutes. Thus, a latent curing agent is blended.
  • the compounding ratio of the iron-based soft magnetic powder whose surface is treated with the inorganic insulating coating and the epoxy resin is 95 to 99% by mass of the iron-based soft magnetic powder and the latent hardener based on the total amount of these.
  • the resin is 1 to 5% by mass. This is because if the epoxy resin is less than 1% by mass, it is difficult to form an insulating coating, and if it exceeds 5% by mass, the magnetic properties are degraded and a resin-rich coarse aggregate is generated.
  • the magnetic core of the present invention is obtained by dry-mixing the iron-based soft magnetic powder whose surface is treated with an inorganic insulating coating and the epoxy resin at a temperature of 100 to 120 ° C.
  • An uncured resin film is formed on the formed inorganic insulating film.
  • This uncured resin film is also an insulating film, and becomes a composite insulating film of an inorganic insulating film and a resin film after thermosetting. Since the insulation of the coating is remarkably improved, it can be used as a magnetic core in a field requiring electrical insulation.
  • An iron-based soft magnetic powder with an insulating coating formed on its surface is formed into a compact by compression molding using a mold, and then heat-cured at a temperature equal to or higher than the thermal curing start temperature of the epoxy resin. A core is obtained.
  • the magnetic core of the present invention is excellent in electrical insulation and mechanical properties such as magnetic properties and crushing strength. In addition, it is excellent in cutting workability after being molded. For this reason, a thin magnetic core and a special-shaped magnetic core can be manufactured easily. Therefore, it can utilize for the outer joint member of a constant velocity universal joint, etc.
  • FIG. 4 is a manufacturing process diagram.
  • the above-described iron-based soft magnetic powder having the inorganic insulating coating formed on the surface and an epoxy resin in which the above-described latent curing agent is already blended are prepared.
  • the iron-based soft magnetic powder is previously adjusted by a classifier to particles that pass through a sieve having a sieve opening of 106 ⁇ m and do not pass through a sieve of 25 ⁇ m.
  • the inorganic insulating iron-based soft magnetic powder and the epoxy resin are dry-mixed at a temperature not lower than the softening temperature of the epoxy resin and lower than the thermosetting start temperature.
  • the inorganic insulating iron-based soft magnetic powder and the epoxy resin are sufficiently mixed at room temperature using a blender or the like.
  • the mixed mixture is put into a mixer such as a kneader and heated and mixed at the softening temperature (100 to 120 ° C.) of the epoxy resin.
  • a mixer such as a kneader
  • the softening temperature 100 to 120 ° C.
  • an insulating coating of epoxy resin is formed on the surface of the inorganic insulating iron-based soft magnetic powder.
  • the epoxy resin is uncured.
  • the contents heated and mixed using a mixer such as a kneader are agglomerated cakes.
  • the pulverization step is a step of obtaining a composite magnetic powder having an epoxy resin insulating film formed on the surface thereof by pulverizing and sieving the agglomerated cake at room temperature.
  • the pulverization is preferably performed using a Henschel mixer, and the sieving is preferably performed using particles that pass through a 60 mesh (250 ⁇ m) sieve.
  • the mold used in the compression molding process may be a mold capable of applying a molding pressure of 98 to 294 MPa. This is because when the molding pressure is less than 98 MPa, the magnetic properties and strength are low, and when it exceeds 294 MPa, the epoxy resin adheres to the inner wall of the mold or the insulation is lowered due to the destruction of the resin film.
  • the molded product taken out from the mold is heated and cured at a temperature of 170 to 190 ° C. for 45 to 80 minutes. This is because if it is less than 170 ° C., it takes a long time to cure, and if it exceeds 190 ° C., deterioration starts.
  • Heat curing is preferably performed in a nitrogen atmosphere. After heat-curing, a magnetic core is obtained by performing cutting, barrel processing, rust prevention treatment, and the like as necessary.
  • Example 1 97.0 g of iron powder particles whose particle surfaces were covered with an inorganic insulating coating and 3.0 g of epoxy resin powder containing dicyandiamide as a curing agent were mixed at room temperature for 10 minutes.
  • the iron powder particles used were particles that passed through a sieve having a sieve opening of 106 ⁇ m and did not pass through a 25 ⁇ m sieve.
  • the mixture was put into a kneader and heated and kneaded at 110 ° C. for 15 minutes.
  • the cake agglomerated from the kneader was taken out and cooled, and then pulverized with a pulverizer.
  • compression molding was performed using a mold at a molding pressure of 200 MPa.
  • the compression molded product was taken out from the mold and cured in a nitrogen atmosphere at a temperature of 180 ° C. for 1 hour.
  • the magnetic core was manufactured by cutting.
  • a toroidal test piece for measuring magnetic properties was produced under the above conditions, and the magnetic properties were measured.
  • the test piece is a flat cylindrical magnetic core with an inner diameter of 7.6 mm ⁇ , an outer diameter of 12.6 mm ⁇ , and a thickness of 5.7 mm.
  • a primary side winding and a secondary side winding are wound around the magnetic core to form a toroidal shape.
  • a test specimen was obtained.
  • the saturation magnetic flux density was measured by measuring the magnetic flux density of the secondary winding when the magnetizing force (A / m) was changed by passing a direct current through the primary winding.
  • the number of winding turns was adjusted so that the inductance of each of the magnetic cores was 10 ⁇ H, and the inductance and relative permeability when the frequency was changed with the inductance at 1 kHz being 100% were measured.
  • the iron loss and temperature characteristics were measured under the conditions shown in Table 1. Further, the crushing strength of the magnetic core was measured. In the measurement, a load in the diameter direction was continuously applied to the magnetic core until breakage occurred, and the load at the time of breakage was measured. The measurement results are shown in Table 1.
  • test piece having a thickness of 10 mm ⁇ 25 mm ⁇ 3 mm was prepared for measuring surface hardness, volume resistance, surface resistance, and density.
  • the surface hardness was measured by the Rockwell hardness test method, the volume resistance and the surface resistance were measured by the four-probe method, and the density was measured by the underwater method. The measurement results are shown in Table 1.
  • Comparative Example 1 A magnetic core was produced in the same manner as in Example 1 using the same iron powder particles as in Example 1 except that the particle surface was not covered with an inorganic insulating coating as iron powder particles. Table 1 shows the results of evaluation performed in the same manner as in Example 1.
  • Comparative Example 2 The iron powder particles whose particle surfaces were covered with an inorganic insulating coating used in Example 1 were compression molded at a molding pressure of 900 MPa using a mold. The compression molded product was taken out of the mold and heat-treated in an air atmosphere at a temperature of 530 ° C. for 20 minutes. Furthermore, the magnetic core was manufactured by cutting. Table 1 shows the results of evaluation performed in the same manner as in Example 1.
  • Comparative Example 3 and Comparative Example 4 A magnetic core (Comparative Example 3) in which iron powder is fixed with polytetrafluoroethylene and a magnetic core (Comparative Example 4) in which Sendust powder is fixed with a phenol resin are formed in the same shape as the above test piece, and the same evaluation as in Example 1 was done.
  • the magnetic cores of Comparative Example 3 and Comparative Example 4 had low mechanical strength, and cracks and cracks occurred when the thin part was cuttable. The results are shown in Table 1.
  • the magnetic core of Example 1 improved in electrical insulation by 10 5 times or more.
  • the magnetic core of the present invention is not only excellent in economic efficiency, magnetic characteristics and material strength, but also excellent in electrical characteristics such as volume resistivity and surface resistance, and can be used as a general-purpose magnetic core.
  • the present invention can be used particularly effectively for a magnetic core that is used by fitting a magnetic core in a frame of an annular or rectangular coil. Further, it can be used as a soft magnetic core that requires a complicated shape, for example, is attached to a heating coil portion of an induction hardening apparatus.

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Abstract

　絶縁性を付与させた磁性コアおよびその製造方法を提供する。樹脂被膜が粒子表面に形成された鉄系軟磁性体粉末を圧縮成形後に熱硬化させて製造される磁性コアであり、上記鉄系軟磁性体粉末は、粉末粒子の表面が無機絶縁被膜処理された鉄系軟磁性体粉末であり、上記樹脂被膜が熱硬化性樹脂の軟化温度以上、熱硬化開始温度未満の温度で乾式混合することにより形成される未硬化樹脂被膜であり、上記圧縮成形が金型を用いる圧縮成形体の製造であり、上記熱硬化が上記熱硬化性樹脂の熱硬化開始温度以上の温度で熱硬化させる。

Description

磁性コアおよびその製造方法
　本発明は磁性コアおよびその製造方法に関し、特に高周波焼入装置の加熱コイル部に取り付けられる鉄系軟質磁性コアおよびその製造方法に関する。
　磁性コアは、コイルの背面に取り付けてワークに磁力線を集中させパワーを増強し誘導加熱を促進させる効果や、反対にコイルの前面に取り付けて磁力線を遮蔽（シールド）し焼入れ不要部位の加熱を防ぐ効果があり、高周波焼入装置の加熱コイルには欠かせない部品となっている。
　例えば、高周波焼入するワークの形状が複雑で焼入深さを調整する必要がある場合は、取り付けるコアの形状、サイズ、数量、方向、位置などを変更することにより誘導加熱の状態を変化させることができ、ワークの焼入深さを制御することが可能となる。このコア材料には、（１）周波数特性が良好なこと、すなわち周波数の変化に伴うインダクタンスの変化が少ないこと、（２）飽和磁束密度が高いこと、（３）比透磁率が高いこと、（４）鉄損が小さいこと、などの磁気特性が必要となる。
　また、多様なワークの形状に対応するため、コア部品も多品種少量生産となることが多く、１つ１つ切削対応にて生産されることが多い。このため、強度が高く切削性に富んだ材料が求められている。
　粉末冶金法により製造される磁性コアは、原料ロスが少なく量産性に優れるため、高周波焼入装置の加熱コイルに用いられる磁性コアとして多用されている。例えば、高周波焼入コイル用磁性コアとして、磁性粉をフッ素樹脂で固着した製品や、センダスト粉をフェノール樹脂で固着した製品などが使用されているが、それらの材料強度は比較的低く、薄肉切削時の割れ発生や、コイル取付け時の破損等の問題があった。
　上記問題を解決するために、樹脂被膜を粒子表面に形成させた鉄系軟磁性体粉末を圧縮成形後に熱硬化させる磁性コアを本出願人は提案している（特許文献１）。この磁性コアは、経済性、磁気特性、および材料強度に優れた、高周波焼入装置の加熱コイル部に取り付けられる汎用性の高い磁性コアである。
特開２０１４－７２４８２号公報
　高周波焼入装置の加熱コイル部に取り付けられる磁性コアには、加熱コイルの形状や磁性コアの取付け形態から、体積固有抵抗値として１０5Ω・ｃｍ程度の電気絶縁性が求められる場合がある。
　しかしながら、特許文献１に記載の磁性コアは、汎用性に優れているが電気絶縁性に関しては不十分であるため、使用用途によっては磁性コアを介して電気的短絡、発熱を生じ、磁性コアの耐久性を著しく低下させる場合がある。このため、絶縁性を求められる用途には、展開が困難であるという問題があった。
　本発明はこのような問題に対処するためになされたものであり、磁性コア、特に高周波焼入装置の加熱コイル部等に取り付けられる軟質磁性コアとして、特許文献１に記載の磁性コアの長所を活かしつつ、絶縁性を付与させた磁性コアおよびその製造方法の提供を目的とする。
　本発明の磁性コアは、樹脂被膜が粒子表面に形成された鉄系軟磁性体粉末を圧縮成形後に熱硬化させて製造される磁性コアである。上記鉄系軟磁性体粉末は、粉末粒子の表面が無機絶縁被膜処理された鉄系軟磁性体粉末であり、上記樹脂被膜が熱硬化性樹脂の軟化温度以上、熱硬化開始温度未満の温度で乾式混合することにより形成される未硬化樹脂被膜であり、上記圧縮成形が金型を用いる圧縮成形体の製造であり、上記熱硬化が上記熱硬化性樹脂の熱硬化開始温度以上の温度で熱硬化させることを特徴とする。
　無機絶縁被膜処理された鉄系軟磁性体粉末は、篩目開き１０６μｍの篩を通過し、同２５μｍの篩を通過しない粒子であることを特徴とする。また、この鉄系軟磁性体粉末の粒子表面に形成される樹脂被膜が潜在性硬化剤を含むエポキシ樹脂であることを特徴とする。特に該潜在性硬化剤がジシアンジアミドであり、この潜在性硬化剤を含むエポキシ樹脂の軟化温度が１００～１２０℃であることを特徴とする。上記鉄系軟磁性体粉末と上記潜在性硬化剤を含むエポキシ樹脂との合計量に対して、上記鉄系軟磁性体粉末が９５～９９質量％、上記潜在性硬化剤を含むエポキシ樹脂が１～５質量％配合されていることを特徴とする。
　本発明の磁性コアは、高周波焼入コイルに使用される磁性コアであることを特徴とする。
上記本発明に係る磁性コアの製造方法は、上記粉末粒子の表面が無機絶縁被膜処理された鉄系軟磁性体粉末と上記潜在性硬化剤を含むエポキシ樹脂とを該エポキシ樹脂の軟化温度以上、熱硬化開始温度未満の温度で乾式混合する混合工程と、上記混合工程により生成した凝集ケーキを室温で粉砕して複合磁性粉末を得る粉砕工程と、上記複合磁性粉末を金型を用いて圧縮成形体とする圧縮成形工程と、上記エポキシ樹脂の熱硬化開始温度以上の温度で上記圧縮成形体を熱硬化させる硬化工程を含むことを特徴とする。特に上記圧縮成形工程が９８～２９４ＭＰａの成形圧力で成形されることを特徴とする。また、上記硬化工程が硬化温度１７０～１９０℃で、不活性ガス雰囲気中で硬化されることを特徴とする。
　本発明の磁性コアは、特許文献１に記載の磁性コアに比較して、体積固有抵抗で表した電気絶縁性が１０5Ω・ｃｍに向上した。
磁性コアおよび高周波コイルの配置関係を示す図である。 磁性コアの斜視図である。 複合磁性粉末粒子の断面図である。 製造工程図である。
　等速自在継手の外側継手部材は、円柱状の素材から冷間鍛造などの鍛造過程を経て製造され、その後、高周波焼き入れされる。この高周波焼き入れは、外側継手部材のカップ部分の内外面および軸部において高周波焼き入れの焼き入れ度を調整するために、高周波コイルの前面もしくは背面に磁性コアを配置して実施されることが多い。
　磁性コアおよび高周波コイルの配置関係を図１に示す。図１（ａ）は環状または矩形状コイルの枠内に磁性コアを嵌め込んで使用する形態の場合を示す図であり、図１（ｂ）はコイルの一端に磁性コアを取付けて使用する形態の場合を示す図である。
　図１（ａ）および図１（ｂ）に示すように、コイル２は電気抵抗の低い銅のパイプや板などで構成され、加熱効率の向上や加熱部位の調整のために、磁束を制御する磁性コア１が配置されている。この磁性コア１はコイル電流３ａが流れることで発生する磁束をワークへ集中させたり、反対に遮蔽させたりすることで誘導加熱の状態を変化させることができる。図１（ａ）の場合、絶縁耐力の低い磁性コア１を使用すると、磁性コア１内を介して漏洩電流３ｂが流れ、磁性コア１が絶縁破壊を起して溶損・短絡するなど、磁性コア１の耐久性が著しく低下することがある。これに対して、図１（ｂ）の場合、磁性コア１を介しての電気の短絡は起こらないため、高い絶縁耐力は必ずしも必要とされない。
　絶縁耐力を向上させるために、磁性コアの原料となる磁性粉表面を絶縁材料で被覆することにより、体積固有抵抗の大きい磁性コアとすることが考えられた。有機絶縁材料または無機材料をそれぞれ単独で被覆したが体積固有抵抗は大きく向上しなかった。しかしながら、有機絶縁材料と無機材料とを複層にすることで、それぞれ単独層の場合に比較して、１０万倍以上の体積固有抵抗の向上がみられた。本発明はこのような知見に基づくものである。
　磁性コアの斜視図の一例を図２に、原料となる複合磁性粉末粒子の断面図を図３に示す。磁性コア１は、複合磁性粉末粒子４を圧縮成形・加熱硬化させて得られる。複合磁性粉末粒子４は、鉄系軟磁性体粉末粒子４ａの表面に無機絶縁被膜４ｂが被覆され、さらにこの無機絶縁被膜４ｂ表面に未硬化の樹脂被膜４ｃが被覆されている。磁性コア１は、複合磁性粉末粒子４を圧縮成形し、その後に樹脂被膜４ｃを熱硬化させて製造される。その後に必要に応じて、切削加工、バレル加工および防錆処理などの後処理を行なう。高周波コイルの形状、大きさ、場所等により、配置される磁性コアの形状等も適宜変更できる。図２に示す磁性コア１は、環状または矩形状コイルの枠内に嵌め込んで使用される磁性コアの例である。
　本発明に使用できる鉄系軟磁性体粉末としては、純鉄、鉄－シリコン系合金、鉄－窒素系合金、鉄－ニッケル系合金、鉄－炭素系合金、鉄－ホウ素系合金、鉄－コバルト系合金、鉄－リン系合金、鉄－ニッケル－コバルト系合金および鉄－アルミニウム－シリコン系合金（センダスト合金）などの粉末を用いることができる。
　上記鉄系軟磁性体粉末の中でも、純鉄が好ましく、特に粉末冶金に用いられている還元鉄粉またはアトマイズ鉄粉が好ましい。より好ましくは得られる磁性コアの機械的特性が優れる還元鉄粉である。還元鉄粉は、製鉄工場で発生する酸化鉄などをコークス等で還元し、次に水素雰囲気で熱処理して製造される鉄粉であり、粒子内に空孔を有している。また、アトマイズ鉄粉は、溶けた鋼を高圧水で粉化・冷却し、その後水素雰囲気で熱処理して製造される鉄粉であり、粒子内に空孔がない。還元鉄粉の断面写真は、表面に凹凸が多く見られ、この凹凸が圧環強度を低下させていると考えられる。
　鉄系軟磁性体粉末粒子の表面は無機絶縁体で被覆されている。無機絶縁材料の種類に特に限定はなく、従来から圧粉磁心において用いられているものを使用することができる。好ましい絶縁材料の例としては、リン酸鉄、リン酸マンガン、リン酸亜鉛、リン酸カルシウム、リン酸アルミニウム等のリン酸金属塩、酸化ケイ素、酸化マグネシウム、酸化アルミニウム、酸化チタン、酸化ジルコニウム等の金属酸化物が挙げられる。また、その他の鉱物を用いることもできる。無機絶縁材料としては１種類の材料を用いてもよいし、２種類以上の材料を併用してもよい。無機絶縁体で被覆されている鉄系軟磁性体粉末の市販品としては、ヘガネス社製商品名；Ｓｏｍａｌｏｙが挙げられる。
　上記表面が無機絶縁被膜処理された鉄系軟磁性体粉末は、篩目開きが１０６μｍの篩を通過し、同２５μｍの篩を通過しない粒子であることが好ましい。好ましい範囲は、９０μｍを通過し、３８μｍを通過しない粒子である。２５μｍを通過する微粉は、鉄粒子表面への樹脂被膜の形成が困難になり、１０６μｍ不通過の鉄粉は鉄損が大きくなる。
　本発明に使用できるエポキシ樹脂は、接着用エポキシ樹脂として使用できる樹脂であって軟化温度が１００～１２０℃の樹脂が好ましい。例えば、室温では固体であるが、５０～６０℃でペースト状になり、１３０～１４０℃で流動性になり、さらに加熱を続けると硬化反応が始まるエポキシ樹脂であれば使用できる。この硬化反応は１２０℃付近でも始まるが、実用的な硬化時間、例えば２時間以内で硬化反応が終了する温度としては１７０～１９０℃であることが好ましい。この温度範囲であると、硬化時間は４５～８０分である。
　エポキシ樹脂の樹脂成分としては、例えばビスフェノールＡ型エポキシ樹脂、ビスフェノールＦ型エポキシ樹脂、ビスフェノールＳ型エポキシ樹脂、水添ビスフェノールＡ型エポキシ樹脂、水添ビスフェノールＦ型エポキシ樹脂、スチルベン型エポキシ樹脂、トリアジン骨格含有エポキシ樹脂、フルオレン骨格含有エポキシ樹脂、脂環式エポキシ樹脂、ノボラック型エポキシ樹脂、アクリルエポキシ樹脂、グリシジルアミン型エポキシ樹脂、トリフェノールフェノールメタン型エポキシ樹脂、アルキル変性トリフェノールメタン型エポキシ樹脂、ビフェニル型エポキシ樹脂、ジシクロペンタジエン骨格含有エポキシ樹脂、ナフタレン骨格含有エポキシ樹脂、アリールアルキレン型エポキシ樹脂等が挙げられる。
　エポキシ樹脂の硬化剤成分は潜在性エポキシ硬化剤である。潜在性エポキシ硬化剤を用いることにより、軟化温度を１００～１２０℃に、また硬化温度を１７０～１９０℃に設定することができ、無機絶縁被膜処理された鉄粉粉末への有機絶縁性塗膜の形成と、その後の圧縮成形および熱硬化を行なうことができる。
　潜在性エポキシ硬化剤としては、ジシアンジアミド、三フッ化ホウ素－アミン錯体、有機酸ヒドラジド等が挙げられる。これらの中で、上記硬化条件に適合するジシアンジアミドが好ましい。
　また、潜在性エポキシ硬化剤と共に、三級アミン、イミダゾール、芳香族アミンなどの硬化促進剤を含むことができる。
　本発明で使用できる上記潜在性硬化剤を含むエポキシ樹脂は、１６０℃で２時間、１７０℃で８０分、１８０℃で５５分、１９０℃で４５分、２００℃で３０分の硬化条件となるように潜在性硬化剤を配合する。
　表面が無機絶縁被膜処理された鉄系軟磁性体粉末とエポキシ樹脂の配合割合は、これらの合計量に対して、鉄系軟磁性体粉末が９５～９９質量％、潜在性硬化剤を含むエポキシ樹脂が１～５質量％である。エポキシ樹脂が１質量％未満であると、絶縁被膜の形成が困難であり、５質量％を超えると磁気特性の低下と樹脂リッチな粗大な凝集体が発生するからである。
　本発明の磁性コアは、上記表面が無機絶縁被膜処理された鉄系軟磁性体粉末と、上記エポキシ樹脂とを１００～１２０℃の温度で乾式混合することで、鉄系軟磁性体粉末表面に形成された無機絶縁被膜上に未硬化樹脂被膜を形成する。この未硬化樹脂被膜も絶縁被膜であり、熱硬化後は無機絶縁被膜と樹脂被膜との複合絶縁被膜となる。被膜の絶縁性が著しく向上するので、電気絶縁性を要求される分野での磁気コアとして利用できる。
　絶縁被膜が表面に形成された鉄系軟磁性体粉末は、金型を用いる圧縮成形により成形体となし、その後エポキシ樹脂の熱硬化開始温度以上の温度で熱硬化させることで一体化された磁性コアが得られる。
　本発明の磁性コアは、電気絶縁性に優れているとともに、磁気特性および圧環強度などの機械的特性に優れている。また、成形したのち切削加工性に優れている。このため、薄型の磁性コア、特殊形状の磁性コアを容易に製造できる。そのため、等速自在継手の外側継手部材等に利用できる。
　上記磁性コアの製造方法を図４により説明する。図４は製造工程図である。
　上述した無機絶縁被膜が表面に形成された鉄系軟磁性体粉末と、上述した潜在性硬化剤が既に配合されているエポキシ樹脂とをそれぞれ準備する。鉄系軟磁性体粉末は予め分級機により篩目開き１０６μｍの篩を通過し、２５μｍの篩を通過しない粒子に調整されている。
　混合工程により、無機絶縁鉄系軟磁性体粉末とエポキシ樹脂とを該エポキシ樹脂の軟化温度以上、熱硬化開始温度未満の温度で乾式混合する。この混合工程においては、最初に無機絶縁鉄系軟磁性体粉末とエポキシ樹脂とを室温で十分にブレンダー等を用いて混合する。次に、混合された混合物をニーダー等の混合機に投入してエポキシ樹脂の軟化温度（１００～１２０℃）にて加熱混合する。この加熱混合の工程により、無機絶縁鉄系軟磁性体粉末の表面にエポキシ樹脂の絶縁被膜が形成される。この段階ではエポキシ樹脂は未硬化である。
　ニーダー等の混合機を用いて加熱混合された内容物は、凝集したケーキ状となっている。粉砕工程は、この凝集ケーキを室温で粉砕して篩分けすることにより、表面にエポキシ樹脂の絶縁膜が形成された複合磁性粉末を得る工程である。粉砕はヘンシェルミキサーが好ましく、篩分けは６０メッシュ（２５０μｍ）の篩を通過する粒子とすることが好ましい。
　圧縮成形工程において使用される金型は９８～２９４ＭＰａの成形圧力を印加できる金型であればよい。成形圧力が９８ＭＰａ未満では磁気特性や強度が低く、２９４ＭＰａを超えるとエポキシ樹脂が金型内壁に固着したり、樹脂被膜の破壊により絶縁性が低下するからである。
　金型より取り出された成形品は、１７０～１９０℃の温度で、４５～８０分加熱硬化される。１７０℃未満では硬化に長時間かかり、１９０℃を超えると劣化が始まるからである。加熱硬化は、窒素雰囲気で行なうことが好ましい。
　加熱硬化後、必要に応じて、切削加工、バレル加工、防錆処理などを行ない磁性コアが得られる。
実施例１
　粒子表面が無機絶縁被膜で覆われた鉄粉粒子９７．０ｇと、硬化剤としてジシアンジアミドを含むエポキシ樹脂粉末３．０ｇとをブレンダーにて室温で１０分間混合した。使用した鉄粉粒子は篩目開き１０６μｍの篩を通過し、２５μｍの篩を通過しない粒子を使用した。混合物をニーダーに投入して１１０℃で１５分間加熱混練した。ニーダーより凝集したケーキを取り出して冷却した後、粉砕機で粉砕した。次いで金型を用いて２００ＭＰａの成形圧力で圧縮成形した。圧縮成形品を金型より取り出し、１８０℃の温度で１時間窒素雰囲気で硬化させた。さらに切削加工を施し磁性コアを製造した。
　また、磁気特性測定用トロイダル状の試験片を上記条件で作製し磁気特性を測定した。試験片は、内径７．６ｍｍφ、外径１２．６ｍｍφ、厚さ５．７ｍｍの平円筒状の磁性コアとし、この磁性コアに一次側巻線および二次側巻線を巻回してトロイダル状の供試試験片を得た。一次側巻線に直流を通電して磁化力（Ａ／ｍ）を変化させたときの二次側巻線の磁束密度を測定して飽和磁束密度を測定した。また、上記磁性コアにそれぞれインダクタンスが１０μＨとなるように巻線の巻回数を調製し、１ｋＨｚにおけるインダクタンスを１００％として、周波数を変化させたときのインダクタンスおよび比透磁率を測定した。上記磁性コアを用いて表１に示す条件で鉄損および温度特性（インダクタンス変化率）を測定した。さらに、上記磁性コアの圧環強度を測定した。測定は、磁性コアに、その直径方向の荷重を破壊が生じるまで連続して加え、破壊したときの荷重を測定した。測定結果を表１に示す。
　また、表面硬さ、体積抵抗、表面抵抗、密度測定用として１０ｍｍ×２５ｍｍ×３ｍｍ厚さの試験片を作製した。表面硬さはロックウェル硬さ試験法により、体積抵抗および表面抵抗は四探針法により、密度は水中法により、それぞれ測定した。測定結果を表１に示す。
比較例１
　鉄粉粒子として粒子表面が無機絶縁被膜で覆われていない以外は、実施例１と同様の鉄粉粒子を用いて、実施例１と同様の方法で磁性コアを製造した。実施例１と同様の方法で評価した結果を表１に示す。
比較例２
　実施例１で用いた、粒子表面が無機絶縁被膜で覆われた鉄粉粒子を金型を用いて９００ＭＰａの成形圧力で圧縮成形した。圧縮成形品を金型より取り出し、５３０℃の温度で２０分間空気雰囲気で熱処理した。さらに切削加工を施し磁性コアを製造した。実施例１と同様の方法で評価した結果を表１に示す。
比較例３および比較例４
　鉄粉をポリテトラフルオロエチレンで固着した磁性コア（比較例３）、センダスト粉をフェノール樹脂で固着した磁性コア（比較例４）を上記試験片と同一の形状として、実施例１と同一の評価を行なった。切削加工の工程で、比較例３および比較例４の磁性コアは機械的強度が弱く、薄肉部の切削可能では割れ、クラックが発生した。結果を表１に示す。
Figure JPOXMLDOC01-appb-T000001
　実施例１の磁性コアは、比較例１および比較例２の磁性コアに比較して、電気絶縁性が１０5倍以上向上した。
　本発明の磁性コアは、経済性、磁気特性および材料強度に優れているとともに、体積固有抵抗、表面抵抗などの電気特性に優れているので、汎用の磁性コアとして利用できる。特に、環状または矩形状コイルの枠内に磁性コアを嵌め込んで使用する磁性コアに特に有効に利用できる。また、複雑な形状を必要とされる、例えば高周波焼入装置の加熱コイル部に取り付けられる軟質磁性コアとして利用できる。
　　１　磁性コア
　　２　コイル
　　３　電流
　　４　複合磁性粉末粒子

Claims (9)

  1. 　樹脂被膜が粒子表面に形成された鉄系軟磁性体粉末を圧縮成形後に熱硬化させて製造される磁性コアであって、
    　前記鉄系軟磁性体粉末は、粉末粒子の表面が無機絶縁被膜処理された鉄系軟磁性体粉末であり、
    　前記樹脂被膜が熱硬化性樹脂の軟化温度以上、熱硬化開始温度未満の温度で乾式混合することにより形成される未硬化樹脂被膜であり、
    　前記圧縮成形が金型を用いる圧縮成形体の製造であり、
    　前記熱硬化が前記熱硬化性樹脂の熱硬化開始温度以上の温度で熱硬化させることを特徴とする磁性コア。
  2. 　前記粉末粒子の表面が無機絶縁被膜処理された鉄系軟磁性体粉末は、篩目開き１０６μｍの篩を通過し、同２５μｍの篩を通過しない粒子であることを特徴とする請求項１記載の磁性コア。
  3. 　前記熱硬化性樹脂が潜在性硬化剤を含むエポキシ樹脂であることを特徴とする請求項１記載の磁性コア。 
  4. 　前記潜在性硬化剤がジシアンジアミドであり、この潜在性硬化剤を含むエポキシ樹脂の軟化温度が１００～１２０℃であることを特徴とする請求項３記載の磁性コア。
  5. 　前記鉄系軟磁性体粉末と前記潜在性硬化剤を含むエポキシ樹脂との合計量に対して、前記鉄系軟磁性体粉末が９５～９９質量％、前記潜在性硬化剤を含むエポキシ樹脂が１～５質量％配合されていることを特徴とする請求項３記載の磁性コア。
  6. 　前記磁性コアが高周波焼入コイルに使用される磁性コアであることを特徴とする請求項１記載の磁性コア。
  7. 　請求項１記載の磁性コアの製造方法であって、
    　前記粉末粒子の表面が無機絶縁被膜処理された鉄系軟磁性体粉末と前記潜在性硬化剤を含むエポキシ樹脂とを該エポキシ樹脂の軟化温度以上、熱硬化開始温度未満の温度で乾式混合する混合工程と、
    　前記混合工程により生成した凝集ケーキを室温で粉砕して複合磁性粉末を得る粉砕工程と、
    　前記複合磁性粉末を金型を用いて圧縮成形体とする圧縮成形工程と、
    　前記エポキシ樹脂の熱硬化開始温度以上の温度で前記圧縮成形体を熱硬化させる硬化工程を含むことを特徴とする磁性コアの製造方法。
  8. 　前記圧縮成形工程が９８～２９４ＭＰａの成形圧力で成形されることを特徴とする請求項７記載の磁性コアの製造方法。
  9. 　前記硬化工程が硬化温度１７０～１９０℃で、不活性ガス雰囲気中で硬化されることを特徴とする請求項７記載の磁性コアの製造方法。
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CN106716562A (zh) 2017-05-24
EP3196897A1 (en) 2017-07-26
US10537938B2 (en) 2020-01-21
EP3196897A4 (en) 2018-05-23
JP6580817B2 (ja) 2019-09-25
CN113113221B (zh) 2024-04-26
US20170297096A1 (en) 2017-10-19
JP2016063070A (ja) 2016-04-25
KR102322977B1 (ko) 2021-11-08
CN113113221A (zh) 2021-07-13

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