WO2015046282A1 - 圧粉磁心、磁心用圧粉体の製造方法、圧粉磁心製造用の押型及び金型装置、並びに、圧粉磁心製造用押型の潤滑組成物 - Google Patents
圧粉磁心、磁心用圧粉体の製造方法、圧粉磁心製造用の押型及び金型装置、並びに、圧粉磁心製造用押型の潤滑組成物 Download PDFInfo
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- WO2015046282A1 WO2015046282A1 PCT/JP2014/075345 JP2014075345W WO2015046282A1 WO 2015046282 A1 WO2015046282 A1 WO 2015046282A1 JP 2014075345 W JP2014075345 W JP 2014075345W WO 2015046282 A1 WO2015046282 A1 WO 2015046282A1
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- green compact
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- molybdenum disulfide
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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
- 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
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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
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/02—Compacting only
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- 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
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- 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
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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
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/02—Compacting only
- B22F2003/026—Mold wall lubrication or article surface lubrication
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- 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
Definitions
- the present invention relates to a powder magnetic core used for soft magnetic parts, a method for producing a powder compact for a magnetic core, a mold and mold apparatus for producing a powder magnetic core, and a lubricating liquid for a mold for producing a powder magnetic core, and in particular, high frequency.
- the present invention relates to a dust core suitable for use in a region, a method for manufacturing a powder for a magnetic core, a pressing core and a mold apparatus for manufacturing a dust core, and a lubricating liquid for a pressing core for manufacturing a dust core.
- the powder magnetic core made of soft magnetic powder bound with a binder such as resin has the advantage of better material yield and reduced material costs. have.
- the degree of freedom in shape is high and the magnetic characteristics can be improved by optimal design of the magnetic core shape.
- an insulating material such as an organic binder or an inorganic powder and a soft magnetic powder are mixed, or an electric insulating film is coated on the surface of the soft magnetic powder to electrically insulate the metal powder.
- the dust core is used for transformers, reactors, thyristor valves, noise filters, choke coils, etc., and also for motor cores, rotors and yokes for motors for general household appliances and industrial equipment, It is also used in solenoid cores (fixed iron cores) for solenoid valves incorporated in electronically controlled fuel injection devices of diesel engines and gasoline engines, and is being applied to various soft magnetic parts.
- the dust core can reduce the eddy current loss in a high frequency region as compared with the silicon steel plate, and the use of the dust core in a high frequency application such as a reactor is increasing.
- the molding method of the powder magnetic core includes an injection molding method (such as Patent Document 1) in which a soft magnetic powder is injected together with a plastic raw material into a mold that defines a product shape, and a soft magnetic powder and a mold cavity. It is roughly classified into compression molding methods (Patent Documents 2, 3, etc.) in which raw material powder containing a binder is filled and compression molding is performed with upper and lower punches. The product shape of the powder magnetic core is imparted in the molding process, and the molding method employed depending on the application of the product is properly used.
- Patent Document 1 an injection molding method
- Patent Documents 2, 3, etc. compression molding methods
- the product shape of the powder magnetic core is imparted in the molding process, and the molding method employed depending on the application of the product is properly used.
- a raw material powder containing a binder resin and a soft magnetic powder or a raw material powder made of a soft magnetic powder having an insulating film on the surface is filled in a die hole of a mold device, Compress with upper and lower punches.
- FIG. 1 A specific example of a process for forming a cylindrical magnetic core green compact by such a compression molding method is shown in FIG.
- the mold apparatus shown in FIG. 1 defines a pressing die 1 having a mold hole 1a that defines an outer peripheral side surface of a green compact with an inner diameter surface, a lower punch 2 that defines a lower surface of the green compact, and an upper surface of the green compact.
- the upper punch 3 is provided.
- a cavity is formed by the mold hole 1a of the stamp 1 and the lower punch 2, and the raw material powder M is prepared by using a powder supply means such as a feeder 4. Fill the cavity.
- the upper punch 3 is lowered and the lower punch 2 is raised relative to the pressing die 1 (in this case, the pressing die 1 is lowered) to enter the cavity.
- the filled raw material powder M is compression molded by the upper punch 3 and the lower punch 2 to obtain a green compact C.
- FIG. 1 (c) the upper punch 3 is moved upward to return to the standby position, and the lower punch 2 is raised relative to the pressing die 1 (in this case, the pressing die 1). Is further lowered), and the green compact C is extracted from the mold hole 1a of the pressing mold 1.
- Iron loss W of the dust core is the sum of eddy current loss W e and hysteresis loss W h, eddy current loss W e and hysteresis loss W h are each, because of the following formula 1 and formula 2,
- the iron loss W is expressed by the following formula 3.
- f is a frequency
- B m is an exciting magnetic flux density
- ⁇ is a specific resistance value
- t is a material thickness
- k 1 and k 2 are coefficients.
- eddy current loss W e since it increases in proportion to the square of the frequency f, to apply the powder core in the reactor or the like used in a high frequency region, eddy current suppression of loss W e is essential.
- eddy current loss W e it is necessary to confine the eddy currents to the small area. Therefore, in the dust core, by individual soft magnetic powder particles is configured to be insulated, achieving suppression of eddy current loss W e. Therefore, when the soft magnetic powder particles communicate with each other, they are conducted through the connected portions, and a large eddy current is generated. Therefore, it is important to ensure insulation of the individual soft magnetic powder particles.
- the side surface of the green compact that has been extracted from the mold cavity is subjected to plastic flow in the surface layer portion, and the insulating coating formed on the surface of the soft magnetic powder particles is destroyed.
- the soft magnetic powder particles become conductive, and the eddy current increases.
- the eddy current circulates around the magnetic flux in an annular shape perpendicular to the direction of the magnetic flux.
- the increase in eddy current can be suppressed by the insulation applied to each soft magnetic powder single particle, but when the insulation is broken at the sliding surface and the outer peripheral surface of the green compact becomes conductive, the eddy current is remarkably increased. To increase.
- a magnetic path is formed by combining magnetic cores, so that a considerable amount of magnetic flux leakage (fringe) occurs from the combined surface.
- the leaked magnetic flux enters again in a direction perpendicular to the conductive sliding contact surface, the eddy current further increases. Therefore, maintaining the insulating property of the sliding surface is one of the very important technical requirements for a magnetic core for high frequency applications.
- powder magnetic core materials low-alloy materials such as pure iron are particularly prone to plastic flow because the base is soft, and because the material system has a low specific resistance at the base, conduction by plastic flow is ensured. Must be suppressed.
- the induced current generated in the dust core flows more concentrated on the surface as the frequency becomes higher. For this reason, if a powder magnetic core in which the plastic flow is generated in the surface layer as described above and the insulating coating of the soft magnetic powder particles is broken is used for high frequency applications such as a reactor, the insulating coating is broken and the soft magnetic powder particles are There induced current flows concentrated in the surface layer portion which conducts and iron loss W are increased eddy current loss W e becomes increasingly larger.
- the present invention is to solve the above problems, an insulating film of soft magnetic powder particle surfaces without breaking in the surface layer, showed a healthy insulated state, an eddy current loss W e and iron loss even when used in high frequency applications
- An object is to provide a dust core in which an increase in W is suppressed.
- the die and die apparatus for producing the dust core capable of suppressing conduction formation due to plastic flow in the surface layer portion of the green compact, and It is an object of the present invention to provide a lubricating liquid for a pressing mold for producing a dust core.
- the dust core is formed of a green compact in which a soft magnetic powder is compression-molded to a density ratio of 91% or more.
- the gist of the contact surface is that it has a surface layer portion in which molybdenum disulfide particles are interposed between the particles of the soft magnetic powder. More preferably, the surface layer portion has a structure in which insulating ceramic particles are also interposed between the particles of the soft magnetic powder.
- the insulating ceramic particles and the molybdenum disulfide particles are interposed between the soft magnetic powder particles to support the soft magnetic powder particles and suppress deformation and plastic flow, and the surface of the soft magnetic powder particles Prevents dielectric breakdown.
- the specific resistance of the surface layer portion on the side surface of the green compact increases due to the insulating properties of the insulating ceramic particles themselves. Therefore, when the induced on the surface of the powder magnetic core current is used as a dust core for high frequency flowing concentrated, and is excellent in reducing the eddy current loss W e.
- adjacent soft magnetic powder particles are preferably in a discontinuous state due to the intervention of the molybdenum disulfide particles and / or insulating ceramic particles.
- the area ratio of the molybdenum disulfide particles present in the portion (gap) where the soft magnetic powder particles do not exist is preferably 30% or more, and when the insulating ceramic particles are used, the insulating ceramics
- the total area ratio of the particles and the molybdenum disulfide particles is preferably 30% or more.
- the particle diameter of the molybdenum disulfide particles is 100 to 1000 nm, and the particle diameter of the insulating ceramic particles is 50 to 1000 nm.
- the surface of the insulating ceramic particles is organic of a Si-containing compound and / or an Al-containing compound. More preferably, a conductive film is formed.
- a method for producing a green compact for a magnetic core wherein a soft magnetic powder is filled in a mold hole of a green mold, and the density ratio of the soft magnetic powder is 91%.
- a method for producing a green compact for compacting a green compact by compressing the soft magnetic powder as described above, and extruding the green compact from the mold cavity, before filling the soft magnetic powder is to form a lubricating coating containing lubricating oil and molybdenum disulfide particles on the inner surface of the mold hole in sliding contact with the green compact during extrusion. It is preferable that the lubricating coating further contains insulating ceramic particles.
- the composition ratio of molybdenum disulfide particles in the lubricating coating is preferably 30 to 80% by mass.
- the lubricating coating contains 1 to 10% by mass of insulating ceramic particles. It is preferable that the molybdenum sulfide particles are contained at a composition ratio of 30 to 80% by mass, and the balance is lubricating oil.
- a lubricating composition in which molybdenum disulfide particles (and insulating ceramic particles) are dispersed in lubricating oil is applied to the inner surface of the mold hole to provide a lubricating coating, and the mold hole contains soft magnetic powder. Fill with raw material powder. As a result, the raw material powder comes into contact with the surface of the mold cavity via the liquid lubricating oil and molybdenum disulfide particles (and insulating ceramic particles).
- part of the lubricating oil penetrates into the gaps between the filled raw material powder particles by capillary force, and along with this, part of the molybdenum disulfide particles (and insulating ceramic particles) are also molded It is introduced into the gap between the raw material powder particles from the inner surface and is sandwiched between the raw material powder particles.
- the side surface of the magnetic core compact after completion of compression is a surface state in which molybdenum disulfide particles (and insulating ceramic particles) are dispersed, and the particles of the soft magnetic powder on the side surface layer portion Molybdenum disulfide particles (and insulating ceramic particles) are interposed between them.
- Lubricating oil and molybdenum disulfide exist between the inner surface of the mold cavity and the green compact.
- the molybdenum disulfide particles dispersed between the soft magnetic powder particles support the soft magnetic powder against the frictional resistance of the extrusion and suppress its deformation and plastic flow.
- the stress caused by the frictional resistance applied to the soft magnetic powder particles is relieved by the cleavage and lubricity of molybdenum disulfide.
- insulating ceramic particles harder than molybdenum disulfide particles support the soft magnetic powder particles and resist stress, and insulate against excessive stress The stress on the soft magnetic powder particles is relieved by the brittle fracture of the conductive ceramic particles.
- the lubricating effect of the lubricating oil and molybdenum disulfide between the mold hole surface and the green compact reduces the frictional resistance between the inner surface of the mold hole and the side of the green compact that is in sliding contact with it. It is possible to easily extract the powder compact, and to obtain a powder magnetic core having a sound side surface where the insulating coating is not destroyed.
- the thickness of the lubricant film formed on the inner surface of the mold cavity is 0.1 to 20 ⁇ m.
- the particle size of the insulating ceramic particles is more preferably 50 to 1000 nm, and the particle size of the molybdenum disulfide particles is preferably 100 to 1000 nm.
- the insulating ceramic particles are those in which an organic coating of a Si-containing compound and / or an Al-containing compound is formed on the surface of the titanium oxide particles.
- the kinematic viscosity of the lubricating oil is preferably from 1,000 to 100,000 mm 2 / s.
- a pressing core for manufacturing a powder magnetic core includes a mold hole for compressing a raw material powder to form a green compact, and a green compact during extrusion of the green compact to be formed.
- the gist of the present invention is to have a lubricating coating containing lubricating oil and molybdenum disulfide particles provided on the inner surface of the mold hole in sliding contact.
- the lubricating coating preferably further contains insulating ceramic particles.
- a mold apparatus for producing a dust core includes the above-described mold for producing a dust core and an upper and lower punch for compressing the raw material powder in the mold hole. The gist.
- the lubricating composition of the die for producing a dust core is characterized in that it contains lubricating oil and molybdenum disulfide particles, and further preferably contains insulating ceramic particles.
- molybdenum disulfide particles are dispersed between the soft magnetic powder particles in the surface layer portion of the side surface of the dust core formed by the inner surface of the mold cavity of the mold. and thereby is suppressed plastic flow of the soft magnetic powder caused by extraction after compression molding, since the insulating film of the soft magnetic powder particle surfaces can be prevented from being destroyed, the eddy current loss W e is suppressed to a low level
- the powder magnetic core can be manufactured, and an excellent product is provided for high frequency applications.
- the specific resistance in the surface layer portion of the dust core side surface increases due to the insulating properties of the insulating ceramic particles dispersed between the soft magnetic powder particles in the surface layer portion on the side surface of the dust core. even flow concentrates induced current on the surface of the powder magnetic core when used as a can suppress the increase in the eddy current loss W e, provides for a dust core which exhibits excellent performance in high-frequency applications Is possible.
- the plastic flow on the side surface of the green compact extracted from the mold hole is effectively reduced. It is possible to obtain a green compact that maintains good insulation without destroying the insulating coating on the surface of the soft magnetic powder particles in the surface layer portion, so that a high-quality green compact can be obtained by a simple method.
- a method for producing a green compact for a magnetic core that is excellent in economic efficiency is provided.
- the green compact for a magnetic core obtained by the production method of the present invention has a surface structure in which molybdenum disulfide particles (and insulating ceramic particles) are dispersed between soft magnetic powder particles, and the surface layer portion with improved insulation. Therefore, a magnetic core green compact that exhibits excellent characteristics even in high frequency applications can be obtained, and a method of manufacturing a magnetic core green compact with high applicability can be provided.
- the side surface of the green compact formed by the inner surface of the mold hole is the inner surface of the mold hole when the green compact is extruded from the mold hole. It becomes an extruded sliding contact surface that makes sliding contact with.
- the higher the density of the green compact the greater the springback that presses the green compact against the inner surface of the mold cavity, so when pressing the green compact out of the mold cavity, The frictional resistance acting between them increases, and plastic flow occurs in the surface layer portion on the side surface of the green compact.
- a lubricating film containing lubricating oil and molybdenum disulfide particles is formed on the inner surface of the mold cavity of the pressing mold, and compression molding of soft magnetic powder is performed using the mold hole having this lubricating film.
- Such a green compact that is compactly molded in the mold cavity is soft on the side of the green compact, even though the inner surface of the mold cavity and the side of the green compact are in sliding contact with each other when extruded from the mold cavity.
- the plastic flow of the magnetic powder particles is suppressed.
- the lubricating coating contains insulating ceramic particles, the effectiveness is even more remarkable. The reason for this can be considered as follows.
- Molybdenum disulfide particles and ceramic particles contained in the lubricating coating are pressed between the soft magnetic powder particles that are pressed against the inner surface of the mold cavity when the soft magnetic powder is compression-molded. It is sandwiched between powder particles. For this reason, the side surface of the green compact molded in the mold cavity has a surface layer portion having a structure in which molybdenum disulfide particles and / or ceramic particles are interposed between soft magnetic powder particles.
- the lubricating oil contained in the lubricating coating reduces the static frictional force and dynamic frictional force to some extent to facilitate extrusion, and molybdenum disulfide particles interposed between the soft magnetic powder particles.
- the ceramic particles support the soft magnetic powder particles and suppress their deformation and plastic flow. Meanwhile, if the stress applied to the soft magnetic powder particles by frictional resistance exceeds a certain level, the molybdenum disulfide particles themselves cleave and break, and if the insulating ceramic particles are included, the hardness of molybdenum disulfide is exceeded. Resist the stress and further break the insulating ceramic particles themselves. Through such breakage of the particles, the stress applied to the soft magnetic powder particles is reduced. The molybdenum disulfide particles and ceramic particles are gradually broken according to the frictional resistance during extrusion, but the broken molybdenum disulfide particles and / or ceramic particles are interposed between the soft magnetic powder particles.
- molybdenum disulfide particles and ceramic particles have appropriate hardness to support the soft magnetic powder particles by entering between the soft magnetic powder particles in the surface layer portion on the side of the green compact.
- the plastic flow of the soft magnetic powder particles is suppressed against the stress caused by the frictional resistance, and the contact and bonding between the soft magnetic powder particles are prevented.
- the molybdenum disulfide particles and the ceramic particles exhibit moderate brittleness or cleavage properties to disperse and relieve the stress caused by the frictional resistance during extrusion. Deformation and plastic flow are suppressed.
- the molybdenum disulfide particles and the ceramic particles are insulative, which ensures the insulation between the soft magnetic powder particles in the surface layer portion on the side of the green compact, and the ceramic particles are rather strengthened. It is valid.
- the lubricating coating contains liquid lubricating oil and molybdenum disulfide particles, which are solid lubricants.
- the lubricating oil is particularly effective for reducing dynamic friction
- the solid lubricant is particularly effective for reducing static friction. Therefore, the friction generated between the inner surface of the mold cavity and the side surface of the green compact during extrusion can be reduced comprehensively by both components.
- molybdenum disulfide particles are interposed between soft magnetic powder particles on the surface layer of the side surface (that is, the extruded sliding contact surface).
- Structure, preferably insulating ceramic particles are also interposed between the soft magnetic powder particles. Therefore, when the surface of such a green compact is observed by, for example, electron probe microanalysis (EPMA), in the SEM image or component map, molybdenum disulfide particles and / Alternatively, the state in which the insulating ceramic particles are dispersed can be confirmed.
- EPMA electron probe microanalysis
- molybdenum disulfide (and insulating ceramic particles) are interposed between soft magnetic powder particles on the side of the green compact to be molded.
- a surface layer portion in which molybdenum disulfide (and / or insulating ceramic particles) is dispersed is formed in the gaps between the soft magnetic powder particles.
- the amount of molybdenum disulfide particles (and / or insulating ceramic particles) contained in the lubricating coating formed on the inner surface of the mold cavity increases, it cannot be pushed in between the soft magnetic powder particles on the side of the formed green compact.
- molybdenum disulfide particles (and / or insulating ceramic particles) are located on the side of the green compact, and the surface layer of the green compact is covered with molybdenum disulfide particles (and / or insulating ceramic particles).
- the side surface of the green compact may thus be coated with at least one of molybdenum disulfide particles and insulating ceramic particles.
- molybdenum disulfide particles (and / or insulating ceramic particles) covering the side surface of the green compact do not become an obstacle in use as a powder magnetic core, and can be removed as necessary.
- Molybdenum disulfide particles (and ceramic particles) are suitable between soft magnetic powder particles as long as the blending balance of molybdenum disulfide particles (and insulating ceramic particles) and lubricating oil in the lubricating coating and the thickness of the coating are good. Since it enters and suppresses plastic flow, excess molybdenum disulfide particles (and / or insulating ceramic particles) are allowed as long as they do not adversely affect the dimensional accuracy of the green compact.
- the presence of insulating ceramic particles dispersed in the gaps between the soft magnetic powder particles improves the insulation between the soft magnetic powder particles, and the insulating ceramic particles introduced from the lubricating coating can reach the inside of the green compact. Therefore, the specific resistance value of the surface layer portion of the side surface of the dust core is higher than that of the inside. The height of the specific resistance of the surface layer portion, an induced current under a high frequency environment in a state that flows to concentrate on the surface of the powder magnetic core, particularly effectively suppressing the eddy current loss W e.
- the plastic flow of soft magnetic powder particles due to the frictional resistance during extrusion from the mold cavity occurs most strongly on the outermost surface of the green compact side, and the influence of the frictional resistance is generally the depth from the outermost surface. Covers an area up to about 20 ⁇ m.
- molybdenum disulfide particles (and insulating ceramic particles) are formed on the surface of the green compact side surface.
- the depth of the surface layer portion where the molybdenum disulfide particles (and insulating ceramic particles) are dispersed on the side surface of the powder magnetic core is about 1 to 100 ⁇ m from the surface, the effect of suppressing the plastic flow of the soft magnetic powder particles Is satisfactory, and a depth of up to about 1 mm is sufficient. Further, if compression molding is performed using a mold hole in which a lubricating coating as described above is formed on the inner surface, a surface layer portion in which such molybdenum disulfide particles (and insulating ceramic particles) are dispersed is formed on the side of the green compact.
- the depth of the surface region where the induced current is concentrated in the dust core in a high frequency environment depends on the frequency, but at least at a frequency of about 1 kHz to 50 kHz, the insulating layer is insulative at the surface layer depth as described above.
- the specific resistance value is increased by the ceramic particles, which can be sufficiently handled.
- the above-mentioned lubricating coating may be formed at least on the inner surface of the mold cavity.
- a surface layer portion in which molybdenum disulfide particles (and insulating ceramic particles) are dispersed may be formed between the magnetic powder particles. Therefore, it is not necessary to form a lubricating film having the above composition on the upper and lower punches that form the upper and lower surfaces of the green compact.
- the green compact may be compression-molded by forming a lubricating film containing molybdenum disulfide and / or insulating ceramic particles on the upper and lower punches. In this case, molybdenum disulfide and A surface layer portion in which the insulating ceramic particles are dispersed is formed, and the soft magnetic powder particles are prevented from being crushed and contacting each other on the uppermost and lowermost surfaces.
- the molybdenum disulfide particles and the insulating ceramic particles surround and restrain the periphery of the soft magnetic powder particles, and the adjacent soft magnetic powder particles become discontinuous.
- the conduction between adjacent soft magnetic powder particles is completely prevented. That is, the higher the discontinuity, the more the specific resistance in this region is improved, which is preferable as a dust core. Further, the restraint of the soft magnetic powder particles becomes strong, and the effect of preventing composition deformation is enhanced.
- a surface layer portion in which molybdenum disulfide particles (and insulating ceramic particles) are interposed between soft magnetic powder particles can be confirmed in surface observation of a side surface based on a component map by EPMA.
- insulating ceramic particles it is important to consider the affinity of molybdenum disulfide particles and insulating ceramic particles for soft magnetic powder. If there is no difference in the affinity of the molybdenum disulfide particles and the insulating ceramic particles to the soft magnetic powder, they will penetrate equally between the soft magnetic powder particles during compacting and the component map Therefore, the state of the surface layer can be evaluated by the area ratio of either molybdenum disulfide particles or insulating ceramic particles.
- the affinity for the soft magnetic powder is different between the insulating ceramic particles and the molybdenum disulfide particles, the high affinity particles cover the soft magnetic powder particles, and the low affinity particles around them.
- particles having low affinity are unevenly distributed in the region corresponding to the gap between the soft magnetic powder particles, and particles having high affinity are present in the soft magnetic powder region and the surrounding region surrounding it. It is unevenly distributed. Therefore, in order to evaluate the intervening particles between the soft magnetic powder particles in the surface layer portion on the side of the green compact, it is considered more appropriate to evaluate based on the area ratio of particles having low affinity for the soft magnetic powder.
- Such a difference in affinity is largely caused by the type of insulating coating formed on the particle surface of the soft magnetic powder and the presence / absence and type of surface modification applied to the insulating ceramic particles.
- the area ratio of molybdenum disulfide particles and / or insulating ceramic particles present in a portion where no soft magnetic powder particles are present (that is, disulfide detected in a region where the soft magnetic powder component is not detected)
- the area of the component of the molybdenum particles and / or the insulating ceramic particles with respect to the imaged image area) is preferably about 30% or more.
- the space factor of the soft magnetic powder on the surface of the green compact decreases.
- the space factor of the soft magnetic powder can be increased to a desired space factor according to the degree of compression. Accordingly, there is no particular upper limit on the area ratio of molybdenum disulfide particles and / or insulating ceramic particles on the outermost surface of the green compact side surface, and as described above, the green powder side surface is completely composed of molybdenum disulfide particles and / or It may be covered with insulating ceramic particles.
- the side of the green compact When the side of the green compact is covered with a thin layer of molybdenum disulfide particles and / or insulating ceramic particles, if this thin layer is removed and the surface of the surface layer is observed, it is interposed between the soft magnetic powder particles.
- the area ratio of the insulating ceramic particles and the molybdenum disulfide particles is generally in the range of about 65% or less.
- the molybdenum disulfide particles and the insulating ceramic particles are introduced from the lubricating coating formed on the inner surface of the mold hole, the surface layer portion on the side surface of the green compact formed by the inner surface of the mold hole (that is, It exists only on the surface and near the surface).
- Such a structure cannot be obtained by compression molding of a raw material powder in which molybdenum disulfide particles and / or insulating ceramic particles are blended with soft magnetic powder.
- compression molding is performed by adding molybdenum disulfide particles and / or insulating ceramic particles to the soft magnetic powder, the fluidity of the raw material powder is reduced, and the filling property of the raw material powder into the cavity of the mold apparatus is reduced.
- the compressibility of the raw material powder itself will be lowered, and it will be difficult to mold the dust core to a high density. Even if it is forcibly formed into a high density, the space factor of the soft magnetic powder in the powder magnetic core decreases due to the presence of molybdenum disulfide particles and / or insulating ceramic particles dispersed throughout the powder compact. Decreases. Therefore, the structure of the present invention in which the molybdenum disulfide particles (and insulating ceramic particles) are dispersed only in the surface layer portion of the green compact by forming a lubricating film on the inner surface of the mold cavity is an insulating material inside the green compact. This is very advantageous in high-density compression molding because the ceramic ceramic particles can be configured not to be dispersed.
- the particle diameter of the powder means the average particle diameter by laser diffraction method for the powder in ⁇ m unit, and the average particle diameter by TEM observation for the powder in nm unit.
- the soft magnetic powder any of soft powder and hard powder may be used. Pure iron, Fe-Si alloy, Fe-Al alloy, permalloy, sendust, permendur, soft ferrite, amorphous magnetic alloy, nano
- An iron-based metal powder containing an iron alloy such as a crystal magnetic alloy can be used, and pure iron powder is superior in terms of high magnetic flux density and formability.
- a soft magnetic powder having a particle size of about 1 to 300 ⁇ m is preferable.
- INDUSTRIAL APPLICABILITY The present invention is particularly effective when a soft soft magnetic powder that easily undergoes plastic deformation during compression molding is used, and an iron-based low alloy in which the amount of addition of iron powder and alloy elements such as Si and Al is 3% or less Most effective for powders. However, it is also effective when using hard soft magnetic powder that hardly undergoes plastic deformation in extrusion after molding, and when soft magnetic powder particles are crushed in compression molding, molybdenum disulfide particles between the crushed pieces of soft magnetic powder particles Or there exists an effect which insulation ceramic particle infiltrates and forms insulation between crushing pieces.
- molybdenum disulfide particles or insulating ceramic particles are dispersed between the soft magnetic powder particles on the side of the green compact so that the side of the green compact can be obtained.
- the effect of improving the specific resistance can be obtained.
- Molybdenum disulfide particles intervening between the soft magnetic powder particles have an effect of facilitating the extrusion of the green compact by exhibiting lubricity for reducing static friction on the inner surface of the mold cavity.
- an insulating film such as a phosphoric acid-based chemical film, a silicone resin film, and the like are preferable.
- Such an insulating film on the particle surface may be formed by chemical conversion treatment or contact coating according to a conventional method.
- descriptions in Japanese Patent No. 4044591 and Japanese Patent No. 4927983 can be referred to.
- you may use it, selecting suitably from commercially available powder products, for example, Somaloy110i (5P) by Höganäs AB company, MH20D by Kobe Steel, etc. are mentioned.
- each soft magnetic powder particle when insulation of each soft magnetic powder particle is ensured by blending a binder such as resin in the soft magnetic powder, it is not necessary to form an insulating film on the particle surface of the soft magnetic powder.
- a binder such as resin
- the proportion of the soft magnetic powder decreases accordingly.
- the space factor of the soft magnetic powder in the powder compact decreases, and the magnetic flux density of the powder magnetic core decreases. For this reason, the amount of the binder should be adjusted to 2% by mass or less of the green compact.
- the particles introduced into the lubricating coating are dispersed between the soft magnetic powder particles to prevent plastic flow of the soft magnetic powder and to electrically insulate the soft magnetic powder. And that it does not show conductivity (insulation).
- molybdenum disulfide and insulating ceramic particles are preferred.
- Molybdenum disulfide fulfills the requirements of hardness and conductivity as particles introduced into the lubricating coating, plays a role in preventing soft flow of the soft magnetic powder and maintaining electrical insulation of the soft magnetic powder. Furthermore, molybdenum disulfide particles function as a solid lubricant and are a lubricious material with high stress relaxation capability. Molybdenum disulfide has a hardness (Vickers hardness: about 500 to 900 HV) that is comparable to ceramics with relatively low hardness, and supports soft magnetic powder particles against the stress caused by frictional resistance to suppress plastic flow. Can do. Since the breaking strain is zero, for excessive stress, it cleaves itself to relieve the stress on the soft magnetic powder particles.
- molybdenum disulfide particles When used with insulating ceramic particles, it generally cleaves prior to insulating ceramic particles when subjected to stress. If the molybdenum disulfide particles are coarse, the amount of particles necessary to ensure insulation of the soft magnetic powder becomes large and the mass of each molybdenum disulfide particle increases. It becomes easy to drop off from the film. For this reason, it is preferable to use a molybdenum disulfide particle having a maximum particle size of 1000 nm or less. On the other hand, excessively fine molybdenum disulfide particles are difficult to manufacture and handle, and therefore it is preferable to use a powder having a maximum particle size of 10 nm or more.
- oxide-based, nitride-based, carbide-based ceramic particles can be used.
- oxide-based ceramic particles aluminum oxide (Al 2 O 3 ), titanium dioxide (TiO 2 ). , Silicon dioxide (SiO 2 ), magnesium oxide (MgO), zirconium dioxide (ZrO 2 ), steatite (MgO ⁇ SiO 2 ), zircon (ZrSiO 4 ), ferrite (M 2+ O ⁇ Fe 2 O 3 ), mullite ( 3Al 2 O 3 .2SiO 2 ), forsterite (2MgO.SiO 2 ), yttria (Y 2 O 3 ) and the like.
- nitride ceramic particles examples include powders of aluminum nitride (AlN), titanium nitride (TiN), silicon nitride (Si 3 N 4 ), and the like.
- carbide-based ceramic particles include powders such as titanium carbide (TiC) and tungsten carbide (WC).
- oxynitride ceramic particles such as sialon (Si-Al-ON-based compounds), carbonitride ceramic particles such as titanium carbonitride (TiCN), cordierite particles, machinable ceramics (SiO 2 ⁇ Al 2 O 3 , AlN ⁇ BN) particles and the like can also be used.
- Such ceramics have a yield stress of about 2000 to 10000 MPa, and are larger than low alloy steels of about 200 to 2000 MPa, so that the soft magnetic powder particles are supported against the stress caused by frictional resistance, and the plastic flow is reduced. Can be suppressed. Furthermore, it has an appropriate hardness (Vickers hardness) of about 200 to 1800 and has zero strain at break. Therefore, for excessive stress, it breaks itself by brittle fracture and stress on the soft magnetic powder particles is reduced. Disperse and relax. As will be described later, fine particles are suitable for the insulating ceramic particles. However, since fine powder increases the risk of dust explosion, in this regard, it is in a sufficiently oxidized state and dust. It is preferable to use an oxide-based insulating ceramic that is less likely to explode. Alternatively, a plurality of different types of ceramic particles as described above may be selected and mixed to be used as insulating ceramic particles.
- the insulating ceramic particles are coarse, the amount of insulating ceramic particles necessary to ensure insulation of the soft magnetic powder increases and the mass of the individual insulating ceramic particles increases. It becomes easy to drop off from the formed film.
- the coarse insulating ceramic particles are The inner surface of the mold cavity is worn away to cause wear, and the stress relaxation due to self-breaking is hardly effective, so the deformation of the soft magnetic powder particles cannot be sufficiently suppressed. Further, when the surface of the soft magnetic powder is coated with an insulating coating, the insulating coating may be broken.
- the insulating ceramic particles having a maximum particle size of 1000 nm or less it is preferable to use the insulating ceramic particles having a maximum particle size of 50 nm or more.
- a green compact of a soft magnetic powder having a surface layer on which the above-mentioned molybdenum disulfide particles (and insulating ceramic particles) are dispersed can be manufactured as follows. First, in the method for producing a green compact for a magnetic core according to the present invention, molybdenum disulfide particles (and insulating ceramic particles) and lubricating oil are contained on the surface defining the cavity of the mold device, particularly on the inner surface of the mold hole. After forming the lubricating coating by applying the lubricating composition, the raw material powder containing the soft magnetic powder is filled in the cavity of the mold apparatus. At this time, the raw material powder filled in the cavity comes into contact with the mold cavity through the lubricating oil in which molybdenum disulfide particles (and insulating ceramic particles) are dispersed.
- the lubricating oil and molybdenum disulfide particles (and insulating ceramic particles) infiltrate between the soft magnetic powder particles as the soft magnetic powder is compressed. Molybdenum disulfide particles (and insulating ceramic particles) are interposed between the particles.
- the distance between the soft magnetic powder particles decreases, and most of the lubricating oil that has entered between the soft magnetic powder particles is extruded together with some of the molybdenum disulfide particles (and insulating ceramic particles). However, the remaining molybdenum disulfide particles (and insulating ceramic particles) remain between the soft magnetic powder particles together with a small amount of lubricating oil.
- the particles with high affinity are near the surface of the soft magnetic powder particles during compression molding. Tend to concentrate in the gaps between the soft magnetic powder particles.
- the side surface of the green compact after completion of compression molding that is, the surface of the green compact in contact with the mold cavity is in a state in which molybdenum disulfide particles and / or insulating ceramic particles are dispersed between the soft magnetic powder particles. Become.
- the soft magnetic powder in contact with the inner surface of the mold hole tends to be plastically deformed by frictional resistance, but the appropriate hardness of molybdenum disulfide particles (and insulating ceramic particles) interposed between the soft magnetic powder particles. Since the soft magnetic powder particles are supported by the resin and the plastic deformation of the soft magnetic powder is prevented, and the frictional resistance is increased, the stress is relieved by the breaking and cleavage of the intervening particles. It is possible to prevent plastic flow of the soft magnetic powder in contact with the magnetic field.
- the die having the lubricating coating as described above provided on the inner surface of the mold cavity and the mold apparatus having the die can suppress the plastic flow of particles on the sliding contact surface when the green compact is extruded, and can be used for manufacturing a dust core. It is suitable as a pressing mold and a mold apparatus.
- the lubricating composition used when forming a lubricating coating on the inner surface of the mold cavity will be described.
- the lubricating composition is a mixture of molybdenum disulfide particles (and insulating ceramic particles) and lubricating oil, and contains molybdenum disulfide particles (and insulating ceramic particles) and lubricating oil as they are.
- a lubricating coating can be formed.
- the lubricating oil functions as a dispersion medium for the solid substance, and is prepared in a semisolid or highly viscous liquid that can form a film by loosely bonding molybdenum disulfide particles (and insulating ceramic particles). .
- lubricating oil that is, a lubricating composition
- molybdenum disulfide particles and insulating ceramic particles
- disulfide is formed on the mold cavity surface.
- Molybdenum particles (and insulating ceramic particles) are arranged.
- the lubricating oil in the lubricating coating reduces friction between the inner surface of the mold hole and the side surface of the green compact when the green compact after compression molding is extracted from the mold hole due to its own lubricity.
- lubricating oil is a liquid lubricant with a low viscosity from the viewpoint of specializing that it is effective in reducing dynamic friction.
- Lubricating oil is selected, and such a combination increases the effectiveness of the lubricating composition in reducing friction during extrusion of the green compact.
- the liquid lubricating oil is easily absorbed by the capillary force in the gaps between the soft magnetic powders, and functions as a carrier that supplies molybdenum disulfide particles (and insulating ceramic particles) to the gaps in the soft magnetic powders.
- Lubricating oils are roughly classified into two types: mineral oils that are refined crude oils and synthetic oils that are produced by chemical processes. Either of these may be used, but mineral oils that are inexpensive and widely used are Easy to use.
- the viscosity of lubricating oil is 100000 mm ⁇ 2 > / s or less.
- the viscosity of liquid lubricating oil shall be 1000 mm ⁇ 2 > / s or more.
- the viscosity of the lubricating oil can be adjusted by blending a viscosity modifier such as a thickener, a thickener can be appropriately added and used so as to exhibit the above kinematic viscosity.
- a dispersant can be added to uniformly disperse the molybdenum disulfide particles in the lubricating oil.
- an additive such as a polymer may be used. Such additives may be appropriately selected from those generally used.
- the proportion of the molybdenum disulfide particles is based on the total amount of lubricating oil and molybdenum disulfide particles when the insulating ceramic particles are not used.
- the proportion of molybdenum disulfide particles is less than 30% by mass, the lubricity provided by the molybdenum disulfide particles between the mold hole inner surface and the green compact side surface is insufficient, and the extrusion resistance of the green compact is sufficiently reduced. It becomes impossible to suppress the plastic flow of the soft magnetic powder particles.
- the ratio of molybdenum disulfide particles exceeds 80% by mass, the amount of lubricating oil becomes relatively small, so that the film forming ability is insufficient and it becomes difficult to uniformly fix the particle components on the mold hole inner surface.
- the function as a carrier for introducing a particle component between soft magnetic powder particles is reduced.
- the lubricating composition used when forming the lubricating coating on the inner surface of the mold cavity has a ratio of molybdenum disulfide particles of 30 to 80 to the total amount of lubricating oil and molybdenum disulfide particles (and insulating ceramic particles). It is preferable to prepare so that it may become a mass%.
- the lubricating coating formed on the inner surface of the mold cavity has a ratio of the insulating ceramic particles of 1 to 10% by mass with respect to the total amount of the lubricating oil, the insulating ceramic particles, and the molybdenum disulfide particles. It is preferable that the composition has a ratio of molybdenum disulfide particles of 30 to 80% by mass.
- the ratio of the insulating ceramic particles is less than 1% by mass, it becomes difficult to effectively interpose the insulating ceramic particles between the soft magnetic powder particles, and it is difficult to improve the specific resistance on the side surface of the dust core. Become.
- the ratio of the insulating ceramic particles to the total amount of the lubricating oil, the insulating ceramic particles, and the molybdenum disulfide particles is 1 to 10% by mass.
- the blending ratio is determined based on the mass of the lubricating oil with the thickener added.
- the amount used is preferably 1 to 10% by mass with respect to the molybdenum disulfide particles.
- the other additive is preferably used in an amount of 1 to 10% by mass with respect to the molybdenum disulfide particles.
- the additive used as needed is added to the lubricating oil and mixed uniformly, and then molybdenum disulfide particles (and insulating ceramic particles) are added and mixed and dispersed uniformly. Can be prepared well.
- the thickness of the lubricating coating formed on the inner surface of the mold hole of the mold apparatus is preferably about 1 to 20 ⁇ m. If the thickness is less than 1 ⁇ m, the amount of lubricating oil is insufficient, and the friction between the formed green compact and the inner surface of the mold hole cannot be sufficiently reduced, and plastic flow of the soft magnetic powder is likely to occur. At the same time, the amount of molybdenum disulfide particles is insufficient, and plastic flow of the soft magnetic powder is likely to occur. Further, when the axial length of the green compact to be manufactured is long, the movement distance at the time of extrusion becomes long, so that adhesion to galling or a mold is likely to occur.
- the thickness of the lubricating coating is preferably about 1 to 20 ⁇ m.
- insulating ceramic particles whose surface has been modified with a coupling agent are used as insulating ceramic particles, organicity (lipophilicity) is imparted to the surface. It is easy to uniformly disperse the ceramic particles in the liquid medium, which is effective in forming a uniform lubricating film in which the insulating ceramic particles are uniformly dispersed on the inner surface of the mold cavity.
- a silane coupling agent, an aluminate coupling agent, a titanate coupling agent, or the like can be used, and these coupling agents may be used in combination.
- the silane coupling agent is used, the surface treatment layer is formed of a compound containing Si on the surface of the insulating ceramic particles.
- a surface treatment layer is formed of a compound containing Al on the surface of the insulating ceramic particles.
- a titanate coupling agent or the like is used, a surface treatment layer is formed of a compound containing Ti on the surface of the insulating ceramic particles.
- Surface modification with a coupling agent can be appropriately performed according to a known treatment method.
- surface treatment with a silane coupling agent includes direct treatment (dry, wet), integral blend method, primer type. There is a processing method.
- insulating ceramic particles whose surface is modified from commercially available powder products may be appropriately selected and used. Such an organic surface treatment layer is also an insulating film.
- the powder for the powder magnetic core used as the dust raw material is generally coated with an inorganic phosphoric acid coating or an organic silicone coating.
- the insulating ceramic particles subjected to surface modification are used, the insulating ceramic particles and the soft magnetic powder particles can be easily contacted during compression molding. That is, the surface modification of the insulating ceramic particles is not only effective for improving the dispersibility in the lubricating oil, but also useful for improving the affinity and adhesion to the soft magnetic powder particles.
- the soft magnetic powder has a silicone resin-based insulating coating on the particle surface, the use of insulating ceramic particles whose surface is modified with a silane coupling agent has a high affinity for each other.
- the insulating property of the soft magnetic powder particle is increased, and the direct contact between the inner surface of the mold hole and the soft magnetic powder particle is also reduced.
- the molybdenum disulfide particles having a lower affinity for the soft magnetic powder than the insulating ceramic particles tend to be concentrated in the gap between the soft magnetic powder particles, and are lubricated while cleaving in the gap.
- the insulating ceramic particles are adsorbed on the soft magnetic powder particles, so that the insulating state of the powder contact surface with the mold can be maintained and improved. An increase in eddy current loss of the magnetic core can be suppressed.
- the effectiveness of the present invention is remarkably enhanced when the insulating ceramic particles subjected to suitable surface modification according to the surface properties of the soft magnetic powder particles are used.
- This point is advantageous in increasing the space factor of the soft magnetic powder in the green compact after molding, and lowers the fluidity of the raw material powder caused by adding a molding lubricant to the raw material powder, It is possible to avoid a decrease in the filling factor and a decrease in the space factor of the soft magnetic powder due to the volume occupied by the molding lubricant itself.
- the inclusion of insulating ceramic particles in the raw material powder is not excluded in the present invention.
- the insulating ceramic particles are dispersed in the pores of the powder compact, so that when used as a powder magnetic core, the magnetic gap is dispersed to form a powder core having a constant permeability.
- excessive insulating ceramic particles do not impair the fluidity and formability of the raw material powder and make high density compression difficult, and the insulating film is insulated from the compressed soft magnetic powder particles. It is desirable to adjust the amount of insulating ceramic particles added to the raw material powder so as not to lose room for receiving the ceramic particles.
- the amount of the insulating ceramic particles added is limited to 1.5% by volume or less with respect to the raw material powder, and the soft magnet is formed. It is preferable that a sufficient amount of insulating ceramic particles be allowed to enter from the lubricating coating on the inner surface of the mold cavity between the powder particles.
- the magnetic core compact formed as described above may be further heat-treated depending on the purpose.
- a heat treatment for heating to the curing temperature of the thermosetting resin can be performed.
- a heat treatment can be performed by heating to the softening temperature of the thermoplastic resin.
- annealing heat treatment may be performed to release the compressive strain accumulated in the soft magnetic powder of the core compact.
- Such heat treatment may be performed according to a conventional method.
- the lubricating oil decomposes and disappears in the temperature rising process of the heat treatment.
- lubricating oil and molybdenum disulfide do not diffuse into the iron substrate in the temperature range of heat treatment generally applied to the dust core, there is no effect on the magnetic properties of the resulting dust core. Few.
- the compacted magnetic core powder is also possible to directly use as a dust core without heat treatment.
- the lubricant does not disappear, it remains attached to the side surface of the dust core.
- the lubricating oil is dissolved in the solvent by washing the surface of the green compact with a solvent or immersing the green compact in the solvent. Easy to remove.
- the molybdenum disulfide particles (and insulating ceramic particles) are dispersed on the surface by being pushed between the soft magnetic powder particles.
- the plastic flow of the soft magnetic powder due to the frictional resistance when extruding the green compact is suppressed, and conduction between the soft magnetic powder particles can be prevented. Accordingly, steps such as pickling and cutting performed to remove the surface layer portion in which the soft magnetic powder particles are plastically flowed and conducted in the green compact obtained by the conventional manufacturing method are unnecessary in the present invention.
- molybdenum disulfide and insulating ceramic particles are arranged around the soft magnetic powder particles in the surface layer portion, so that the insulation on the side surface is enhanced, This is suitable for suppressing an increase in iron loss.
- Example 1> Preparation of lubricating composition
- a mineral oil (Nutou H32 manufactured by ExxonMobil Co., Ltd.) having a kinematic viscosity adjusted to each value shown in Table 1 using a thickener (SOLGAM SH 210 manufactured by Seiwa Kasei Co., Ltd.) was prepared.
- SOLGAM SH 210 manufactured by Seiwa Kasei Co., Ltd.
- Sample numbers A1 to A19 A lubricating composition was prepared.
- an iron-based soft magnetic powder (Somaloy 110i (5P) manufactured by Höganäs AB), whose surface is insulated and coated, the main particle content in the particle size distribution: 45 to 75 ⁇ m) was prepared, and the mold hole in which the lubricating film was formed as described above
- the raw material powder was compression-molded at a molding pressure of 1200 MPa using an upper punch and extruded to obtain cylindrical compacts of sample numbers A1 to A19.
- the density of the green compact was measured by the Archimedes method, and the density ratio of the green compact was calculated. The results are shown in Table 1.
- the presence or absence of bonding is determined by the presence or absence of sliding traces in the SEM image, and in the component map by EPMA, the presence or absence of Fe element flow, that is, whether or not Fe element is detected between soft magnetic powder particles. Judged. That is, when a sliding mark is confirmed, a clear soft magnetic powder joining occurs. In addition, even when no clear sliding trace is confirmed, if Fe element is detected between soft magnetic powder particles, plastic flow of the soft magnetic powder occurs, so it is considered that bonding has occurred. It is done. Table 1 shows the results of the determination of whether or not the soft magnetic powder was joined.
- FIG. 3 shows an SEM image and component map of the side surface of the green compact
- FIG. 4 shows an SEM image and component map of the green compact of sample number A5.
- molybdenum disulfide is formed between the soft magnetic powder particles by forming a lubricating coating composed of mineral oil and 30 to 80% by mass of molybdenum disulfide particles on the inner surface of the mold cavity. It can be seen that the plastic flow of the soft magnetic powder can be suppressed during the extrusion of the green compact by interposing the particles. From the results of sample numbers A11 to A18, it can be seen that it is preferable to use a lubricating oil having a kinematic viscosity of about 1000 to 100,000 mm 2 / s.
- sample number A10 it was considered that the amount of molybdenum disulfide particles introduced into the green compact decreased due to the dripping of the lubricating coating on the inner surface of the mold cavity.
- sample number A19 the viscosity of the lubricating oil was high. For this reason, it is considered that molybdenum disulfide particles do not easily enter between the soft magnetic powder particles.
- Fe derived from soft magnetic powder is detected in the particle shape, and Mo and S derived from molybdenum disulfide particles are detected in a portion where Fe is not detected. That is, the molybdenum disulfide particles are filled in the gaps between the soft magnetic powder particles, the plastic flow of the soft magnetic powder particles is suppressed, and the insulation between the particles is maintained.
- each of the green compacts of sample numbers A2, A3, A8, and A9 is used as a core, and the coil is wound with the same number of turns.
- the frequency is 50 kHz and the magnetic flux density is 0.1 T under the same conditions.
- insulating ceramic particles titanium oxide powder (particle size: 100 nm), alumina powder (particle size: 200 nm), silica powder (particle size: 100 nm), aluminum nitride powder (particle size: 100 nm), titanium nitride powder (particle size) : 800 nm) and titanium carbide powder (particle size: 1000 nm).
- insulating ceramic particles had an organic coating by surface modification with a silane coupling agent (n-butyltrimethoxysilane).
- a mineral oil (Nutou H32 manufactured by ExxonMobil Co., Ltd.) having a kinematic viscosity adjusted to each value shown in Table 2 using a thickener (SOLGAM SH 210 manufactured by Seiwa Kasei Co., Ltd.) was prepared.
- the ratio of the insulating ceramic particles and the molybdenum disulfide particles to the total amount of the lubricating oil, the insulating ceramic particles and the molybdenum disulfide particles (particle size: 0.5 ⁇ m) is the ratio shown in Table 2, respectively.
- an iron-based soft magnetic powder (Somaloy 110i (5P) manufactured by Höganäs AB), whose surface is insulated and coated, the main particle content in the particle size distribution: 45 to 75 ⁇ m) was prepared, and the mold hole in which the lubricating film was formed as described above
- the raw material powder was compression-molded using an upper punch at a molding pressure of 1200 MPa and extruded to obtain cylindrical compacts of sample numbers B1 to B28.
- the density of the green compact was measured by the Archimedes method, and the density ratio of the green compact was calculated. The results are shown in Table 2.
- the detection region is different between the titanium oxide particles and the molybdenum disulfide particles, and the detection region of the titanium oxide particles corresponds to the detection region of the soft magnetic powder particles (Fe),
- the detection area of the molybdenum disulfide particles almost coincides with the area corresponding to the gap between the soft magnetic powder particles (the part where Fe is not detected). This is thought to be due to the fact that the insulating coating on the surface of the soft magnetic powder particles is an organic coating, and the titanium oxide particles used have been subjected to organic surface modification with a coupling agent.
- the titanium oxide particles tend to localize on the surface of the soft magnetic powder particles, and the molybdenum disulfide particles tend to concentrate in the gaps between the soft magnetic powder particles. Seem. Therefore, in the surface layer portion of the green compact, both the titanium oxide particles and the molybdenum disulfide particles are interposed between the soft magnetic powder particles. On the outermost surface of the green compact, the surface area of the soft magnetic powder particles is the dioxide dioxide. Titanium particles are detected in the detection region of the soft magnetic powder particles, and molybdenum disulfide is detected in a concentrated manner in a region corresponding to the gap between the soft magnetic powder particles. Therefore, in evaluating the surface layer portion of the green compact in the component map, the area ratio of molybdenum disulfide particles (that is, Mo and S) is used as an index.
- molybdenum disulfide particles that is, Mo and S
- alumina powder, silica powder, aluminum nitride powder, titanium nitride powder and titanium carbide powder can be used as insulating ceramic particles in the same manner, and the plastic flow of soft magnetic powder particles can be suppressed. Recognize.
- sample numbers B19 to B28 it can be seen that it is preferable to use a lubricating oil having a kinematic viscosity of about 1000 to 100,000 mm 2 / s.
- sample number B19 it was considered that the amount of molybdenum disulfide particles introduced into the green compact decreased due to the dripping of the lubricating coating on the inner surface of the mold cavity.
- sample number B28 the viscosity of the lubricating oil was high. For this reason, it is considered that molybdenum disulfide particles do not easily enter between the soft magnetic powder particles.
- each of the green compacts of sample numbers B1 and B28 is used as a core, the coil is wound with the same number of turns, and the eddy current under the same conditions of frequency: 50 kHz and magnetic flux density: 0.1 T.
- the loss was measured and compared, the eddy current loss in the green compact of sample number B1 was clearly less than that of the green compact of sample number B28.
- Example 3> Preparation of lubricating composition
- titanium oxide powder particle size: 100 nm
- silica powder particle size: 100 nm
- a lubricating oil a mineral oil (Nuto H32 manufactured by ExxonMobil Co., Ltd.) having a kinematic viscosity adjusted to 10,000 mm 2 / s using a thickener (SOLGAM SH 210 manufactured by Seiwa Kasei Co., Ltd.) was prepared.
- the ratio of insulating ceramic particles and molybdenum disulfide particles to the total amount of lubricating oil, insulating ceramic particles and molybdenum disulfide particles is 5 mass% and 50 mass%, respectively. These were blended and dispersed uniformly to prepare lubricating compositions of sample number B29 (titanium oxide powder) and sample number B30 (silica powder).
- an iron-based soft magnetic powder (Somaloy 110i (5P) manufactured by Höganäs AB), whose surface is insulated and coated, the main particle content in the particle size distribution: 45 to 75 ⁇ m) was prepared, and the mold hole in which the lubricating film was formed as described above
- the raw material powder was compression-molded at a molding pressure of 1200 MPa using an upper punch and extruded to obtain cylindrical compacts of sample numbers B29 to B30.
- the density of the green compact was measured by the Archimedes method, and the density ratio of the green compact was calculated. The density ratios were 93.3% (sample number B29) and 93.4% (sample number B30), respectively.
- sample number B29 differs in that the constituent component (Ti) of the insulating ceramic particles does not show a distribution surrounding the soft magnetic powder particles. That is, the insulating ceramic particles are intensively distributed in the gaps between the soft magnetic powder particles, like the molybdenum disulfide particles. Therefore, since there is no organic coating by surface modification, the affinity of the insulating ceramic particles to the soft magnetic powder is similar to that of the molybdenum disulfide particles, and the soft magnetic powder particles are mixed with the molybdenum disulfide during compaction. Understood to be embedded in between. This point has been confirmed to be the same for the green compact of sample number B30 using silica powder as the insulating ceramic particles.
- each of the green compacts of sample number A5 of example 1, sample number B4 of example 2 and sample number B29 of example 3 is used as a core, and a coil is wound with the same number of turns.
- the dust core of the present invention can be applied to a transformer, a reactor, a thyristor valve, a noise filter, a choke coil, and the like.
- a motor iron core, a motor rotor and yoke for general household appliances and industrial equipment, and a diesel engine It can also be applied to a solenoid core (fixed iron core) for a solenoid valve incorporated in an electronically controlled fuel injection device of a gasoline engine. In particular, it is highly effective in application to a reactor or the like used in a high frequency region.
Abstract
Description
We=(k1Bm 2t2 /ρ)f2
Wh=k2Bm 1.6f
W=We+Wh=(k1Bm 2t2 /ρ)f2+k2Bm 1.6f
軟磁性粉末としては、軟質な粉末及び硬質な粉末の何れを用いても良く、純鉄、Fe-Si合金、Fe-Al合金、パーマロイ、センダスト、パーメンジュール、ソフトフェライト、アモルファス磁性合金、ナノクリスタル磁性合金等の鉄合金を含む鉄系金属の粉末が使用でき、磁束密度の高さや成形性等の点では純鉄粉が優れている。高周波用に適した高密度圧粉磁心を得る上で、粒径が1~300μm程度の軟磁性粉末が好ましい。本発明は、圧縮成形に際して塑性変形し易い軟質な軟磁性粉末を使用する場合に特に有効であり、鉄粉末、及び、Si、Al等の合金元素の添加量が3%以下の鉄系低合金粉末に対して最も効果がある。しかし、成形後の押し出しにおいてほとんど塑性変形しない硬質な軟磁性粉末を用いる場合にも有効であり、圧縮成形において軟磁性粉末粒子が破砕した時に、軟磁性粉末粒子の破砕片間に二硫化モリブデン粒子又は絶縁性セラミックス粒子が浸入して破砕片間に絶縁形成する効果がある。又、塑性変形し難いが破砕するほど硬くもない軟磁性粉末の場合でも、圧粉体側面の軟磁性粉末粒子間に二硫化モリブデン粒子又は絶縁性セラミックス粒子が分散することで、圧粉体側面の比抵抗が向上する効果を得ることができる。軟磁性粉末粒子間に介在する二硫化モリブデン粒子は、特に静止摩擦を低減する潤滑性を型孔内面に対して発揮して、圧粉体の押し出しを容易にする効果がある。
潤滑被膜に導入される粒子は、軟磁性粉末粒子間に分散して軟磁性粉末の塑性流動を防止すると共に、軟磁性粉末の電気的絶縁を行うものであるので、適度な硬さを有する粒子であること、及び、導電性を示さないもの(絶縁性)であること、が必要である。このためには、二硫化モリブデン及び絶縁性セラミックス粒子が好適である。
二硫化モリブデン粒子は、粗大であると、軟磁性粉末の絶縁を確保するために必要な粒子量が多量になると共に、個々の二硫化モリブデン粒子の質量が増加するため、型孔内面に形成した被膜から脱落し易くなる。このため、二硫化モリブデン粒子の大きさは、最大粒径が1000nm以下のものを用いることが好ましい。その一方で、過度に微細な二硫化モリブデン粒子は、その製造及び取扱いが難しくなることから、最大粒径が10nm以上である粉末を用いることが好ましい。
先ず、本発明の磁心用圧粉体の製造方法においては、金型装置のキャビティを規定する面、特に型孔の内面に、二硫化モリブデン粒子(及び絶縁性セラミックス粒子)と潤滑油とを含有する潤滑組成物を塗布して潤滑被膜を形成した後、軟磁性粉末を含む原料粉末を金型装置のキャビティに充填する。このとき、キャビティに充填された原料粉末は、二硫化モリブデン粒子(及び絶縁性セラミックス粒子)が分散する潤滑油を介して型孔と接触する。
潤滑組成物は、二硫化モリブデン粒子(及び絶縁性セラミックス粒子)と潤滑油とを混合した混合物であり、そのままの状態で、二硫化モリブデン粒子(及び絶縁性セラミックス粒子)と潤滑油とを含有する潤滑被膜を形成することができる。潤滑組成物において、潤滑油は、固体物質の分散媒体として機能し、二硫化モリブデン粒子(及び絶縁性セラミックス粒子)を緩やかに結合して被膜を形成可能な半固体状又は高粘性液状に調製する。従って、二硫化モリブデン粒子(及び絶縁性セラミックス粒子)を分散した潤滑油(つまり、潤滑組成物)を型孔表面に塗布することによって、流動可能な潤滑被膜が形成され、型孔表面に二硫化モリブデン粒子(及び絶縁性セラミックス粒子)が配置される。更に、潤滑被膜における潤滑油は、それ自身の潤滑性によって、圧縮成形後の圧粉体を型孔から抜き出す際に、型孔内面と圧粉体側面との摩擦を軽減する。固体潤滑剤である二硫化モリブデン粒子は静止摩擦の低減に特に有効であるので、潤滑油の採用は、動摩擦の低減に有効であるように特化する観点から、粘度が低い液状の潤滑剤として潤滑油を選択するものであり、このような組み合わせによって、潤滑組成物は、圧粉体の押し出し時の摩擦低減に対する有効性が高まる。又、液状の潤滑油は、軟磁性粉末の隙間に毛細管力によって吸収され易く、二硫化モリブデン粒子(及び絶縁性セラミックス粒子)を軟磁性粉末の隙間に供給するキャリアとして機能する。このようなことから、粘度が高いグリースやワックスのような半固体状のものは好ましくなく、液状の潤滑油が使用される。潤滑油は、原油を精製した鉱油系と、化学プロセスにより製造される合成油系の二種類に大別され、何れであってもかまわないが、安価で広く使用される鉱油系の潤滑油は利用し易い。
潤滑油は、増粘剤等の粘度調整剤を配合することによって粘度を調節できるので、上記のような動粘度を示すように適宜増粘剤を添加して使用することができる。又、潤滑油中に二硫化モリブデン粒子を均一に分散するために、分散剤を添加することができる。更に、高分子ポリマー等のような添加剤も使用しても良い。このような添加剤は、一般的に利用されるものから適宜選択して使用すれば良い。
(潤滑組成物の調製)
潤滑油として、増粘剤(成和化成社製SOLGAM SH 210)を用いて動粘度を表1の各値に調整した鉱油(エクソンモービル社製ヌトーH32)を用意した。
潤滑油及び二硫化モリブデン粒子(粒径:0.5μm)の合計量に対する二硫化モリブデン粒子の割合が表1に記載される割合になるように配合して均一に分散させ、試料番号A1~A19の潤滑組成物を調製した。
内径が20mmの円筒形型孔を有する押型に下パンチを嵌合して成形用キャビティを構成し、型孔の内径面に、上述で調製した試料番号A1~A19の潤滑組成物の1つを塗布して(塗布量:0.1cc)乾燥することによって、型孔の内径面に、厚さが20μm程度の潤滑被膜を形成した。
原料粉末として、表面を絶縁被覆された鉄基軟磁性粉末(ヘガネスAB社製Somaloy110i(5P))、粒度分布における主たる粒分:45~75μm)を用意し、上述で潤滑被膜を形成した型孔に60gを投入して、上パンチを用いて1200MPaの成形圧で原料粉末を圧縮成形し、押し出すことによって、試料番号A1~A19の円柱状の圧粉体を得た。アルキメデス法にて圧粉体の密度を測定して、圧粉体の密度比を計算した。結果を表1に示す。
得られた圧粉体の側面をEPMA装置を用いて観察し、側面の成分マップにおける二硫化モリブデン粒子の面積率(%)を調べた。面積率は、倍率が100倍の撮影画像を画像解析ソフト(Quick grain standard)を用いて解析(閾値:RGB:160)することによって測定した。更に、圧粉体側面における軟磁性粉末粒子の状態を評価するために、側面のSEM像において軟磁性粉末粒子の接合の有無を調べた。接合の有無は、SEM像における摺動痕の有無により判定すると共に、EPMAによる成分マップにおいて、Fe元素の流動の有無、つまり、軟磁性粉末の粒子間にFe元素が検出されるか否かにより判定した。すなわち、摺動痕が確認される場合、明らかな軟磁性粉末の接合が生じる。また、明確な摺動痕が確認されない場合であっても、軟磁性粉末の粒子間においてFe元素が検出される場合は、軟磁性粉末の塑性流動が生じるので、接合が生じているものと考えられる。このようして調べた軟磁性粉末の接合の有無の判断結果を表1に示す。
(潤滑組成物の調製)
絶縁性セラミックス粒子として、酸化チタン粉末(粒径:100nm)、アルミナ粉末(粒径:200nm)、シリカ粉末(粒径:100nm)、窒化アルミニウム粉末(粒径:100nm)、窒化チタン粉末(粒径:800nm)及び炭化チタン粉末(粒径:1000nm)を用意した。これらの絶縁性セラミックス粒子は、シランカップリング剤(n-ブチルトリメトキシシラン)での表面改質による有機質被覆を有するものであった。又、潤滑油として、増粘剤(成和化成社製SOLGAM SH 210)を用いて動粘度を表2の各値に調整した鉱油(エクソンモービル社製ヌトーH32)を用意した。
潤滑油、絶縁性セラミックス粒子及び二硫化モリブデン粒子(粒径:0.5μm)の合計量に対する絶縁性セラミックス粒子及び二硫化モリブデン粒子の割合が、各々、表2に記載される割合になるようにこれらを配合して均一に分散させ、試料番号B1~B28の潤滑組成物を調製した。
内径が20mmの円筒形型孔を有する押型に下パンチを嵌合して成形用キャビティを構成し、型孔の内径面に、上述で調製した試料番号B1~B28の潤滑組成物の1つを塗布して(塗布量:0.1cc)乾燥することによって、型孔の内径面に、厚さが20μm程度の潤滑被膜を形成した。
原料粉末として、表面を絶縁被覆された鉄基軟磁性粉末(ヘガネスAB社製Somaloy110i(5P))、粒度分布における主たる粒分:45~75μm)を用意し、上述で潤滑被膜を形成した型孔に60gを投入して、上パンチを用いて1200MPaの成形圧で原料粉末を圧縮成形し、押し出すことによって、試料番号B1~B28の円柱状の圧粉体を得た。アルキメデス法にて圧粉体の密度を測定して、圧粉体の密度比を計算した。結果を表2に示す。
得られた圧粉体の側面を、EPMA装置を用いて観察し、側面の成分マップにおける二硫化モリブデン粒子の面積率(%)を調べた。面積率は、実施例1と同様に、倍率が100倍の撮影画像を画像解析ソフトを用いて解析することによって測定した。更に、圧粉体側面における軟磁性粉末粒子の状態を評価するために、側面のSEM像において軟磁性粉末粒子の接合の有無を調べた。接合の有無は、実施例1と同様に、SEM像における摺動痕の有無により判定すると共に、EPMAによる成分マップにおいて、Fe元素の流動の有無、つまり、軟磁性粉末の粒子間にFe元素が検出されるか否かにより判定した。このようして調べた軟磁性粉末の接合の有無の判断結果を表2に示す。
又、試料番号B4の圧粉体のSEM像及び成分マップを図5に示す。
(潤滑組成物の調製)
絶縁性セラミックス粒子として、表面改質を施していない酸化チタン粉末(粒径:100nm)及びシリカ粉末(粒径:100nm)を用意した。又、潤滑油として、増粘剤(成和化成社製SOLGAM SH 210)を用いて動粘度を10000mm2/sに調整した鉱油(エクソンモービル社製ヌトーH32)を用意した。
潤滑油、絶縁性セラミックス粒子及び二硫化モリブデン粒子(粒径:0.5μm)の合計量に対する絶縁性セラミックス粒子及び二硫化モリブデン粒子の割合が、各々、5質量%及び50質量%になるようにこれらを配合して均一に分散させ、試料番号B29(酸化チタン粉末)及び試料番号B30(シリカ粉末)の潤滑組成物を調製した。
内径が20mmの円筒形型孔を有する押型に下パンチを嵌合して成形用キャビティを構成し、型孔の内径面に、上述で調製した試料番号B29~B30の潤滑組成物の1つを塗布して(塗布量:0.1cc)乾燥することによって、型孔の内径面に、厚さが20μm程度の潤滑被膜を形成した。
原料粉末として、表面を絶縁被覆された鉄基軟磁性粉末(ヘガネスAB社製Somaloy110i(5P))、粒度分布における主たる粒分:45~75μm)を用意し、上述で潤滑被膜を形成した型孔に60gを投入して、上パンチを用いて1200MPaの成形圧で原料粉末を圧縮成形し、押し出すことによって、試料番号B29~B30の円柱状の圧粉体を得た。アルキメデス法にて圧粉体の密度を測定して、圧粉体の密度比を計算した。密度比は、各々、93.3%(試料番号B29)及び93.4%(試料番号B30)であった。
得られた圧粉体の側面をEPMA装置を用いて観察し、側面の成分マップにおける二硫化モリブデン粒子の面積率(%)を調べた。面積率は、実施例1と同様に、倍率が100倍の撮影画像を画像解析ソフトを用いて解析することによって測定した。更に、圧粉体側面における軟磁性粉末粒子の状態を評価するために、側面のSEM像において軟磁性粉末粒子の接合の有無を調べた。接合の有無は、実施例1と同様に、SEM像における摺動痕の有無により判定すると共に、EPMAによる成分マップにおいて、Fe元素の流動の有無、つまり、軟磁性粉末の粒子間にFe元素が検出されるか否かにより判定した。この結果、試料番号B29及び試料番号B30の圧粉体の何れにおいても、軟磁性粉末粒子の接合は無かった。
Claims (24)
- 軟磁性粉末が密度比91%以上に圧縮成形された圧粉体によって構成され、前記圧粉体の押し出し摺接面に、前記軟磁性粉末の粒子間に二硫化モリブデン粒子が介在する構造の表層部を有する圧粉磁心。
- 前記圧粉体の押し出し摺接面に有する前記表層部の構造において、前記軟磁性粉末の粒子間に、更に、絶縁性セラミックス粒子が介在する請求項1に記載の圧粉磁心。
- 前記圧粉体の押し出し摺接面は、更に、絶縁性セラミックス粒子及び二硫化モリブデン粒子の少なくとも一方によって被覆される請求項1又は2に記載の圧粉磁心。
- 前記絶縁性セラミックス粒子は、粒径が50~1000nmであり、前記二硫化モリブデン粒子は、粒径が100~1000nmである請求項2又は3に記載の圧粉磁心。
- 前記絶縁性セラミックス粒子は、酸化物セラミックス、窒化物セラミックス、炭化物セラミックス、炭窒化セラミックス及び酸窒化セラミックスからなる群より選択される少なくとも1種のセラミックスによって構成される粒子であり、前記酸化物セラミックスは、酸化アルミニウム、二酸化チタン、二酸化珪素、酸化マグネシウム、二酸化ジルコニウム、ステアタイト、ジルコン、フェライト、ムライト、フォルステライト及びイットリアからなる群より選択され、前記窒化物セラミックスは、窒化アルミニウム、窒化チタン及び窒化珪素からなる群より選択され、前記炭化物セラミックスは、炭化チタン及び炭化タングステンからなる群より選択される請求項2~4の何れか1項に記載の圧粉磁心。
- 前記絶縁性セラミックス粒子は、Si、Al及びTiのうちの少なくとも1種の元素を含有する化合物で構成される被膜が表面に形成されている請求項2~5の何れか1項に記載の圧粉磁心。
- 前記押し出し摺接面の電子プローブ微小分析による成分マップにおいて、前記二硫化モリブデン粒子の面積率が30%以上である請求項1~6の何れか1項に記載の圧粉磁心。
- 前記軟磁性粉末の粒子は、表面を被覆する絶縁被膜を有し、前記絶縁被膜は、シランカップリング剤及びシリコーン樹脂の少なくとも1種を含む請求項1~7の何れか1項に記載の圧粉磁心。
- 圧粉体成形用金型の型孔に軟磁性粉末を充填して、前記軟磁性粉末の密度比が91%以上になるように前記軟磁性粉末を圧縮して圧粉体を成形し、前記圧粉体を前記型孔から押し出す磁心用圧粉体の製造方法であって、
前記軟磁性粉末を充填する前に、押し出し時の圧粉体と摺接する前記型孔の内面に、潤滑油と二硫化モリブデン粒子とを含有する潤滑被膜を形成する磁心用圧粉体の製造方法。 - 前記潤滑被膜は、前記二硫化モリブデン粒子と前記潤滑油との合計量に対して30~80質量%の割合で前記二硫化モリブデン粒子を含有する請求項9に記載の磁心用圧粉体の製造方法。
- 前記潤滑被膜は、前記潤滑油及び前記二硫化モリブデン粒子を含有する潤滑組成物を前記型孔の内面に塗布することによって形成される請求項9又は10に記載の磁心用圧粉体の製造方法。
- 前記潤滑被膜は、更に、絶縁性セラミックス粒子を含有する請求項9に記載の磁心用圧粉体の製造方法。
- 前記潤滑被膜は、前記絶縁性セラミックス粒子と前記二硫化モリブデン粒子と前記潤滑油との合計量に対して、1~10質量%の割合で前記絶縁性セラミックス粒子を含有し、30~80質量%の割合で前記二硫化モリブデン粒子を含有する請求項12に記載の磁心用圧粉体の製造方法。
- 前記潤滑被膜は、前記潤滑油、前記絶縁性セラミックス粒子及び前記二硫化モリブデン粒子を含有する潤滑組成物を前記型孔の内面に塗布することによって形成される請求項12又は13に記載の磁心用圧粉体の製造方法。
- 前記絶縁性セラミックス粒子の粒径は、50~1000nmであり、前記二硫化モリブデン粒子の粒径は、100~1000nmである請求項12~14の何れか1項に記載の磁心用圧粉体の製造方法。
- 前記絶縁性セラミックス粒子は、酸化物セラミックス、窒化物セラミックス、炭化物セラミックス、炭窒化セラミックス及び酸窒化セラミックスからなる群より選択される少なくとも1種のセラミックスによって構成される粒子である請求項12~15の何れか1項に記載の磁心用圧粉体の製造方法。
- 前記絶縁性セラミックス粒子は、シランカップリング剤、アルミネートカップリング剤及びチタネートカップリング剤からなる群より選択される少なくとも1種のカップリング剤によって表面が改質されている請求項12~16の何れか1項に記載の磁心用圧粉体の製造方法。
- 前記潤滑被膜の厚さは、1~20μmである請求項9~17の何れか1項に記載の磁心用圧粉体の製造方法。
- 前記潤滑油の動粘度は、1000~100000mm2/sである請求項9~18の何れか1項に記載の磁心用圧粉体の製造方法。
- 原料粉末を圧縮して圧粉体を成形するための型孔と、
成形される圧粉体の押し出し時に圧粉体と摺接する前記型孔の内面に設けられる、潤滑油と二硫化モリブデン粒子とを含有する潤滑被膜と
を有する圧粉磁心製造用押型。 - 前記潤滑被膜は、更に、絶縁性セラミックス粒子を含有する請求項20に記載の圧粉磁心製造用押型。
- 請求項20又は21に記載の圧粉磁心製造用押型と、前記型孔内で原料粉末を圧縮するための上下パンチとを有する圧粉磁心製造用金型装置。
- 潤滑油と、二硫化モリブデン粒子とを含有する、圧粉磁心製造用押型の潤滑組成物。
- 更に、絶縁性セラミックス粒子を含有する請求項23に記載の圧粉磁心製造用押型の潤滑組成物。
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