JP2005243769A - Dust core manufacturing method and dust core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dust core manufacturing method and a dust core having high strength and excellent magnetic characteristics.
A method of manufacturing a dust core includes a metal magnetic particle 10 and a plurality of composite magnetic particles 30 having an insulating coating 20 surrounding the surface of the metal magnetic particle 10, and a lubricating organic substance 40 having a first melting point. A step of forming a molded body by press-molding a mixture containing a high-viscosity organic substance 50 having a second melting point larger than the first melting point, and the molded body is made to have a melting point equal to or higher than the first melting point. A step of performing a first heat treatment at a temperature lower than the second melting point for 30 minutes or more, and a step of performing a second heat treatment at a temperature equal to or higher than the second melting point after the first heat treatment. .
[Selection] Figure 2

Description

  TECHNICAL FIELD The present invention generally relates to a method for manufacturing a dust core and a dust core, and more specifically, a method for manufacturing a dust core obtained by press-molding iron powder having an insulating coating on its surface. And a dust core.

In recent years, in magnetic devices such as electromagnetic valves and motors, dust cores exhibiting excellent magnetic characteristics in a wide range of frequencies are being used instead of electromagnetic steel sheets. For example, Japanese Patent Application Laid-Open No. 2002-246219 discloses such a dust core and a manufacturing method thereof (Patent Document 1). According to the method for manufacturing a powder magnetic core disclosed in Patent Document 1, first, a predetermined amount of polyphenylene sulfide (PPS resin) is mixed with phosphate-coated atomized iron powder, and this is pressure-molded. The obtained molded body is heated in air at a temperature of 320 ° C. for 1 hour, and further heated at a temperature of 240 ° C. for 1 hour. Then, a dust core is produced by cooling.
JP 2002-246219 A

  In the method for manufacturing a powder magnetic core disclosed in Patent Document 1, a PPS resin is mixed with phosphoric acid coating-treated atomized iron powder before performing pressure molding. This PPS resin has a large viscosity. Therefore, it intervenes between the atomized iron powders that have been pressure-molded, thereby improving the strength of the resulting dust core.

  However, since the lubricity of the PPS resin is not sufficient, the PPS resin does not have a function of protecting the phosphate coating on the surface of the atomized iron powder during pressure molding. In other words, the phosphoric acid coating-treated atomized iron powders come into contact with each other during pressure molding, and a part of the phosphoric acid coating is destroyed. In this case, there arises a problem that the interparticle eddy current loss of the phosphoric acid film-treated atomized iron powder increases and the effective magnetic permeability of the dust core decreases. Actually, in the dust core disclosed in Patent Document 1, the effective permeability of the dust core is 0.3 mass% or less at a high frequency of 5000 Hz where interparticle eddy current loss becomes significant. In the range of.

  Accordingly, an object of the present invention is to solve the above-mentioned problems, and to provide a dust core manufacturing method and a dust core having high strength and exhibiting excellent magnetic characteristics.

  The inventors of the present invention, when using a combination of an organic substance having a low melting point for the purpose of preventing damage to the insulating coating and an organic substance having a high melting point for improving the strength of the molded body, in the production of the dust core, It was found that the strength of the dust core decreases when the former organic substance finally remains inside the powder core. And from this knowledge, it came to complete this invention demonstrated below.

  A method of manufacturing a dust core according to the present invention includes a metal magnetic particle, a plurality of composite magnetic particles having an insulating coating surrounding the surface of the metal magnetic particle, a lubricating first organic substance having a first melting point, Forming a molded body by pressure-molding a mixture containing a high-viscosity second organic substance having a second melting point larger than the first melting point; The step of performing the first heat treatment at a temperature lower than the second melting point for 30 minutes or more, and the step of performing the second heat treatment at a temperature higher than the second melting point after the first heat treatment. Prepare.

  According to the method of manufacturing a powder magnetic core configured in this way, first, in the step of forming a molded body by pressure molding, a first organic material having lubricity is interposed between adjacent composite magnetic particles and combined. Functions as a buffer between magnetic particles. This prevents the composite magnetic particles from rubbing directly at the time of pressure molding and destroying the insulating coating surrounding the surface of the metal magnetic particles.

  Next, by performing the first heat treatment at a temperature equal to or higher than the first melting point for 30 minutes or more, the first organic material that has already played a role as a buffer material during pressure molding is fluidized, Discharge outside. At this time, by setting the heat treatment temperature below the second melting point, it is possible to prevent the high-viscosity second organic substance from fluidizing and obstructing the movement of the first organic substance to the outside of the molded body. . In addition, not only the first organic substance but also the second organic substance can be prevented from being discharged to the outside of the molded body. Furthermore, it can prevent that the viscosity characteristic of a 2nd organic substance deteriorates by the chemical reaction of a 1st organic substance and a 2nd organic substance.

  Next, the second heat treatment is performed at a temperature equal to or higher than the second melting point, thereby fluidizing the high-viscosity second organic substance and spreading it between the plurality of composite magnetic particles. Thereby, a 2nd organic substance functions as an adhesive agent which joins several composite magnetic particles, and can improve the intensity | strength of a molded object. At this time, since the first organic material is discharged to the outside of the molded body by the first heat treatment, the strength of the molded body is not reduced by the first organic material.

  For the reasons described above, according to the manufacturing method of the present invention, it is possible to realize a dust core having excellent strength and reduced inter-particle eddy current loss by an insulating coating.

  Also preferably, the first organic substance is higher fatty acid type, metal salt type of higher fatty acid, wax type, higher alcohol type, polytetrafluoroethylene, high molecular weight polyethylene, thermoplastic polyamide, 6-nylon, 6-6 nylon and It contains at least one selected from the group consisting of 6-12 nylon. High molecular weight polyethylene refers to polyethylene having a molecular weight of 100,000 or more. According to the method for manufacturing a powder magnetic core configured as described above, the first organic material containing these materials exhibits excellent lubricity, and functions sufficiently as a cushioning material during pressure molding. For this reason, it can prevent reliably that an insulating film is destroyed.

  Preferably, the second organic substance includes at least one selected from the group consisting of PPS (poly phenylene sulfide) resin, POM resin (polyplastics), polyetherimide, polyimide, polyamideimide, and non-thermoplastic resin. . According to the method for manufacturing a powder magnetic core configured as described above, the second organic material containing these materials exhibits a sufficiently high viscosity and firmly bonds the composite magnetic particles to each other. For this reason, the strength of the dust core can be dramatically improved.

  Preferably, the step of performing the first heat treatment includes a step of heat-treating the molded body at a temperature not lower than the second organic melting point and not lower than the second melting point. According to the method for manufacturing a powder magnetic core configured as described above, the first organic substance can be further changed from a liquid to a gas or a decomposed gas, and can be more reliably discharged to the outside of the molded body. . Thereby, the strength reduction of a molded object by the 1st organic substance remaining in the inside of a molded object can be suppressed effectively.

  Preferably, the step of performing the first heat treatment includes a step of heat-treating the molded body for 60 minutes or more. According to the method for manufacturing a powder magnetic core configured as described above, the first organic material can be more reliably discharged to the outside of the molded body. Thereby, the effect similar to the above-mentioned effect can be acquired.

  Further preferably, the step of performing the first heat treatment includes a step of heat-treating the molded body while maintaining a predetermined temperature in the range of the first melting point or higher and lower than the second melting point for 30 minutes or more. According to the method for manufacturing a powder magnetic core configured as described above, the first organic material can be more reliably discharged to the outside of the molded body. Thereby, the effect similar to the above-mentioned effect can be acquired.

  Preferably, the step of performing the first heat treatment includes a step of raising the temperature from the first melting point to the second melting point over a period of 90 minutes or more. According to the method for manufacturing a powder magnetic core configured as described above, the first organic material can be more reliably discharged to the outside of the molded body. Thereby, the effect similar to the above-mentioned effect can be acquired.

  A dust core according to the present invention has a metal magnetic particle and an insulating coating surrounding the surface of the metal magnetic particle, a plurality of composite magnetic particles bonded together, and an organic substance interposed between the plurality of composite magnetic particles; Is provided. The dust core has a frequency of 5.0 kHz or more when the magnetic permeability is reduced by 5% from the permeability when an AC magnetic field of 50 Hz is applied. According to the dust core configured as described above, even when a high frequency of 5.0 kHz or higher is applied to the dust core, the magnetic permeability is not significantly reduced.

  Preferably, the dust core has a three-point bending strength of 80 MPa or more. According to the dust core configured as described above, both excellent magnetic characteristics and high strength can be realized.

  As described above, according to the present invention, it is possible to provide a dust core manufacturing method and a dust core that have high strength and exhibit excellent magnetic properties.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view showing the surface of a dust core produced by the dust core manufacturing method according to the embodiment of the present invention. Referring to FIG. 1, the dust core includes a plurality of composite magnetic particles 30 composed of metal magnetic particles 10 and an insulating coating 20 that surrounds the surface of metal magnetic particles 10. An organic substance 60 is interposed between the plurality of composite magnetic particles 30. Each of the plurality of composite magnetic particles 30 is joined by an organic material 60 or joined by meshing unevenness of the composite magnetic particle 30. The organic substance 60 will be described later in detail.

  In order to produce the dust core in FIG. 1, first, metal magnetic particles 10 are prepared. The metal magnetic particles 10 are, for example, iron (Fe), iron (Fe) -silicon (Si) alloy, iron (Fe) -nitrogen (N) alloy, iron (Fe) -nickel (Ni) alloy, iron (Fe) -carbon (C) alloy, iron (Fe) -boron (B) alloy, iron (Fe) -cobalt (Co) alloy, iron (Fe) -phosphorus (P) alloy, iron (Fe ) -Nickel (Ni) -cobalt (Co) alloy and iron (Fe) -aluminum (Al) -silicon (Si) alloy. The metal magnetic particles 10 may be a single metal or an alloy.

  The average particle diameter of the metal magnetic particles 10 is preferably 5 μm or more and 300 μm or less. When the average particle diameter of the metal magnetic particles 10 is 5 μm or more, the metal is difficult to be oxidized, so that the magnetic characteristics of the dust core can be improved. Moreover, when the average particle diameter of the metal magnetic particles 10 is set to 300 μm or less, the compressibility of the mixed powder does not decrease at the time of pressure forming described later. Thereby, the density of the molded object obtained by pressure molding can be enlarged.

  The average particle size referred to here is the particle size of particles in which the sum of the mass from the smaller particle size reaches 50% of the total mass in the histogram of the particle size measured by the sieving method, that is, 50% particle size. Say D.

  FIG. 2 to FIG. 4 are schematic views showing aspects of organic substances mixed with the composite magnetic particles. Referring to FIGS. 2 to 4, next, the insulating film 20 is formed on the surface of the metal magnetic particle 10 to produce the composite magnetic particle 30, and the obtained composite magnetic particle 30 and the lubricious organic material 40 are used. And high viscosity organic material 50 is mixed. The organic materials 40 and 50 are mixed with the composite magnetic particles 30 in different modes by the mixing method employed at this time.

  When obtaining the mixed powder shown in FIG. 2, for example, the composite magnetic particles 30 and the organic substances 40 and 50 are put into a V-type mixer and mixed. As a result, a mixed powder in which the particulate organic substances 40 and 50 are dispersed between the adjacent composite magnetic particles 30 can be obtained. When obtaining the mixed powder shown in FIG. 3, for example, when the insulating coating 20 is wet-coated on the surfaces of the metal magnetic particles 10, a solution in which the particulate organic substances 40 and 50 are mixed is used. At this time, an aqueous solution may be used, or an aqueous solution to which an organic solvent is added may be used. Thereby, it is possible to obtain a mixed powder in which the particulate organic substances 40 and 50 are embedded in the insulating coating 20 or adhered to the surface of the insulating coating 20. Furthermore, when obtaining the mixed powder shown in FIG. 4, for example, an organic solvent or an aqueous solution in which the organic substances 40 and 50 are dissolved is prepared, and the composite magnetic particle 30 is put therein. Thereby, the mixed powder in a state where the film-like organic substances 40 and 50 are attached to the surface of the insulating coating 20 can be obtained.

  In addition, the mixing method demonstrated above is an example, and is not limited to these methods. Moreover, you may form the mixed powder of the composite magnetic particle 30 and the organic substances 40 and 50 in the state which combined the aspect shown in FIGS. For example, after the organic substances 40 and 50 are provided on the composite magnetic particle 30 in the embodiment shown in FIG. 3, the organic substances 40 and 50 are further added to the composite magnetic particle 30 and mixed using a V-type mixer. good.

  The insulating coating 20 is formed of a material having at least electrical insulation, and is formed of, for example, a phosphorus compound, a silicon compound, a zirconium compound, or an aluminum compound. Examples of such a material include iron phosphate containing phosphorus and iron, manganese phosphate, zinc phosphate, calcium phosphate, silicon oxide, titanium oxide, aluminum oxide, and zirconium oxide.

  The insulating coating 20 functions as an insulating layer between the metal magnetic particles 10. By covering the metal magnetic particles 10 with the insulating coating 20, the electrical resistivity ρ of the dust core can be increased. Thereby, it can suppress that an eddy current flows between the metal magnetic particles 10, and can reduce the iron loss of the powder magnetic core resulting from the interparticle eddy current loss.

  The melting point of the organic substance 50 is higher than the melting point of the organic substance 40. Examples of such an organic substance 40 include materials having excellent lubricity, such as higher fatty acid series, higher fatty acid metal salt series, wax series, higher alcohol series, polytetrafluoroethylene (Teflon (R)), high molecular weight polyethylene, Thermoplastic polyamide, 6-nylon, 6-6 nylon, 6-12 nylon and the like can be used. Higher fatty acid systems include stearic acid systems. The metal salt system of higher fatty acid includes a metal salt of stearic acid, and calcium stearate, zinc stearate, magnesium stearate, lead stearate and the like can be used. Examples of the wax system include paraffin wax (main component is n-paraffin), micro wax (main component is i-paraffin), polyethylene wax (low molecular polyethylene or partially oxidized polyethylene), and the like. Other higher alcohol behenic acid and 12 hydroxystearic acid, amide stearic acid amide, oleic acid amide, erucic acid amide, methylene bis stearic acid amide, ethylene bis stearic acid amide and ethylene bis oleic acid amide, ester The systemic stearic acid monoglyceride, bentaerythritol tetrastearate, hydrogenated castor oil and stearyl stearate can be used as the organic substance 40.

Moreover, as the organic substance 50, materials having high viscosity, such as PPS resin, POM resin, polyetherimide (Ultem), polyimide, polyamideimide, and non-thermoplastic resin can be used. Non-thermoplastic resin refers to a resin that has characteristics similar to those of thermoplastic resin, but does not exist at a melting point lower than the thermal decomposition temperature, and is a wholly aromatic polyimide resin using biphenyltetracarboxylic dianhydride ( For example, the product name “Vespel” manufactured by DuPont is available. Moreover, as a polyimide, the brand name "UIP-R" by Ube Industries, Ltd. can be used, for example. When a non-thermoplastic resin is used as the organic substance 50, the deflection temperature under load (at 1.82 MPa load) is used instead of the melting point. Note that the deflection temperature under load means the temperature measured by the load deflection temperature test method prescribed in JIS _{K 7207 -1983.}

  Next, the obtained mixed powder is put into a mold and, for example, pressure-molded at a pressure of 700 MPa to 1500 MPa. Thereby, mixed powder is compressed and a molded object is formed. The atmosphere for pressure molding is preferably an inert gas atmosphere or a reduced pressure atmosphere. In this case, it is possible to suppress the powder from being oxidized by oxygen in the atmosphere.

  During the pressure molding, the organic substance 40 functions as a buffer material between the composite magnetic particles 30. This prevents the composite magnetic particles 30 from coming into contact with each other and rubbing, and prevents the insulating coating 20 from being destroyed during pressure molding.

  Next, the first heat treatment is performed on the molded body for 30 minutes or more at a temperature not lower than the melting point of the organic substance 40 and lower than the melting point of the organic substance 50. By this first heat treatment, the organic substance 40 is fluidized and discharged to the outside of the molded body. Note that the melting point refers to a temperature at which an organic substance changes from a solid phase state to a liquid phase state, but depending on the type of the organic substance, there is a substance that is directly in a gas phase state from the solid phase state. In such a case, the temperature at which the organic substance changes from the solid phase state to the gas phase state (sublimation temperature) is referred to as the melting point.

  Further, it is more preferable that the heat treatment temperature is set to a temperature equal to or higher than the thermal decomposition temperature of the organic substance 40 and lower than the melting point of the organic substance 50 to heat-treat the molded body. The thermal decomposition temperature of the organic substance 40 refers to a temperature (boiling point) at which the liquid organic substance further changes to a gas phase. In addition, regarding the organic substance 40 that is decomposed from a liquid phase state into a decomposition gas and a decomposition residue, the temperature at which the decomposition gas and decomposition residue are decomposed is referred to as a thermal decomposition temperature of the organic substance 40. When a non-thermoplastic resin is used as the organic substance 50, the heat treatment temperature is set to be equal to or higher than the melting point or thermal decomposition temperature of the organic substance 40 and less than the deflection temperature under load of the organic substance 50 (at 1.82 MPa load). Furthermore, it is preferable that the above-mentioned heat treatment time is 60 minutes or more. By setting the heat treatment temperature and the heat treatment time in this manner, the organic matter 40 can be discharged more reliably to the outside of the molded body.

  Subsequent to the first stage heat treatment, the molded body is subjected to the second stage heat treatment at a temperature equal to or higher than the melting point of the organic substance 50 for a predetermined time. By the second stage heat treatment, the organic substance 50 is fluidized and spread between the plurality of composite magnetic particles 30.

  FIG. 5 and FIG. 6 are graphs showing specific examples of the temperature change of the heat treatment performed on the molded body. Referring to FIG. 5, the heat treatment temperature is raised to a predetermined temperature in the range from the melting point of organic substance 40 to the melting point of organic substance 50, and the temperature is maintained for 30 minutes or more (low temperature indicated by arrow 150 in the figure). portion). Thereafter, the heat treatment temperature is raised to a temperature just before the melting point of the organic substance 50, and the first heat treatment 100 is completed. Further, in order to perform the second stage heat treatment 200, the heat treatment temperature is continuously increased from the melting point of the organic substance 50 to a predetermined temperature equal to or higher than the melting point of the organic substance 50, and the temperature is maintained for a certain time (high temperature indicated by an arrow 250 in the figure). portion). Thereafter, the heat treatment temperature is gradually lowered by furnace cooling.

  Referring to FIG. 6, the heat treatment temperature is increased at a constant rate over a period of 90 minutes or more from the melting point of organic substance 40 to the melting point of organic substance 50, and the first-stage heat treatment is performed on the compact. . Further, in order to perform the second stage heat treatment 200, the heat treatment temperature is continuously increased from the melting point of the organic substance 50 to a predetermined temperature equal to or higher than the melting point of the organic substance 50, and the temperature is maintained for a certain time. Thereafter, the heat treatment temperature is gradually lowered by furnace cooling.

  By carrying out such a two-stage heat treatment on the molded body, the amount of organic matter contained in the molded body varies with the heat treatment. That is, at the time of forming a molded body by pressure molding, the organic substances 40 and 50 are both present in the molded body, and the organic substance 40 functions as a buffer material between the composite magnetic particles 30. Next, when the first stage heat treatment is performed, all or most of the organic substance 40 is discharged to the outside of the molded body, and the organic substance 50 mainly exists in the molded body. Further, by performing the second stage heat treatment, the organic substance 50 is present in the compact in a state of being distributed between the composite magnetic particles 30.

  After the heat treatment, the powder compact shown in FIG. 1 is completed by subjecting the molded body to appropriate processing such as extrusion and cutting. Since the dust core shown in FIG. 1 is formed through the heat treatment process described above, the organic material 60 provided has a proportion of the organic material 40 suppressed as much as possible, and most of the organic material 60 is composed of the organic material 50. Yes. For this reason, it can suppress that the function as an adhesive agent of the organic substance 60 which joins the adjacent composite magnetic particles 30 decreases by mixing of the organic substance 40, and can improve the intensity | strength of a powder magnetic core.

  The method of manufacturing a powder magnetic core according to the present invention includes a metal magnetic particle 10 and a plurality of composite magnetic particles 30 having an insulating coating 20 surrounding the surface of the metal magnetic particle 10, and a first lubricating property having a first melting point. A molded body is formed by pressure-molding a mixture containing the organic substance 40 as the organic substance and the organic substance 50 as the high-viscosity second organic substance having a second melting point larger than the first melting point. A step of subjecting the molded body to a first heat treatment (first-stage heat treatment 100) for 30 minutes or more at a temperature not lower than the first melting point and lower than the second melting point; And a step of subjecting the molded body to a second heat treatment (second-stage heat treatment 200) at a temperature equal to or higher than the second melting point.

  A dust core according to the present invention includes a metal magnetic particle 10 and an insulating coating 20 that surrounds the surface of the metal magnetic particle 10, and a plurality of composite magnetic particles 30 joined together and a plurality of composite magnetic particles 30. And an organic material 60 interposed. The dust core has a frequency of 5.0 kHz or more when the magnetic permeability is reduced by 5% from the permeability when an AC magnetic field of 50 Hz is applied.

  According to the dust core manufacturing method and the dust core thus configured, the molding step can be performed without damaging the insulating coating 20 due to the function of the organic substance 40 as a buffer material. For this reason, in the obtained dust core, the insulating coating 20 can sufficiently function as an insulating layer between the metal magnetic particles 10, and the interparticle eddy current loss generated between the metal magnetic particles 10 can be reduced. it can. At the same time, a two-stage heat treatment is performed in which the heat treatment temperature is set within a predetermined range, and therefore a dust core having a sufficiently high strength can be obtained by the organic material 60 containing the organic material 50 as a main component.

  The production method of the dust core according to the present invention was evaluated by the examples described below.

First, a molded body was produced according to the manufacturing method described in the embodiment. At this time, the trade name “Somalloy 500” manufactured by Höganäs was used as the composite magnetic particle 30. In this powder, the phosphoric acid compound film as the insulating film 20 is formed on the surface of the iron powder as the metal magnetic particles 10. Further, zinc stearate (melting point: 125 ° C., thermal decomposition temperature: 250 ° C.) was used as the lubricious organic substance 40, and PPS resin (melting point: 285 ° C.) was used as the high-viscosity organic substance 50. For mixing the composite magnetic particles 30 and the organic substances 40 and 50, a V-type mixer was used, and both were mixed in the embodiment shown in FIG. The pressure at the time of pressure molding was set to 900 MPa, and molded bodies (samples 2 to 16) having a density of 7.5 g / cm ³ were obtained. At the same time, for comparison, a molded body (sample 1) using only the PPS resin as the organic substance 50 without mixing the organic substance 40 was also produced. Table 1 shows the ratio of the organic substances contained in the compacts of Samples 1 to 16.

  Next, the produced molded body was subjected to two stages of heat treatment according to the temperature profile shown in FIG. At this time, the time for holding in the low temperature portion indicated by the arrow 150 in FIG. 5 in the first stage heat treatment is set to 30 minutes, and in the high temperature portion indicated by the arrow 250 in FIG. 5 in the second stage heat treatment. The time to perform was 30 minutes. By changing the temperature maintained in the first stage heat treatment, the molded body was subjected to heat treatment under different temperature conditions. The molded bodies of Samples 1 and 2 were subjected to a heat treatment in which the heat treatment temperature was increased to 350 ° C. at a rate of temperature increase of 6 ° C./min, and the temperature was maintained for 30 minutes. Only the second stage heat treatment was performed without performing the heat treatment. Table 1 shows the temperature conditions of the heat treatment performed on the compacts of Samples 1 to 16.

  Next, an AC magnetic field of 50 Hz was applied to the molded body after the heat treatment at room temperature, and the magnetic permeability at that time was first measured. Then, an alternating magnetic field with a gradually increasing frequency was applied to the compact, and the frequency at which the magnetic permeability obtained by the measurement was 5% less than the magnetic permeability when an alternating magnetic field of 50 Hz was applied was determined. The obtained 5% reduction frequency is shown in Table 1.

  Furthermore, by applying a load to a predetermined position of the molded body supported at both ends and performing a bending test in accordance with JIS standard for measuring the stress value (breaking stress value) when the molded body breaks, the molded body The three-point bending strength was determined. FIG. 7 is a graph showing the relationship between the maintenance temperature during the first stage heat treatment and the three-point bending strength in the examples. The obtained three-point bending strength is shown in Table 1, and the change in the three-point bending strength with respect to the maintenance temperature during the first stage heat treatment is shown in FIG.

  Referring to Table 1, it was found that the 5% reduction frequency was higher in other molded articles as compared with the molded article of Sample 1 in which the zinc stearate as the organic substance 40 was not provided. From this result, it was confirmed that zinc stearate sufficiently functioned as a buffer material during pressure molding, and the inter-particle eddy current loss was reduced by the insulating coating 20.

  In addition, referring to FIG. 7 as well, in the molded bodies of Samples 5 to 13 in which the maintenance temperature during the first stage heat treatment was a melting point of zinc stearate of 125 ° C. or more and less than 285 ° C. of PPS resin, three points were obtained. In the molded bodies of Samples 10 to 13 in which the bending strength is high and the maintenance temperature during the first stage heat treatment is a thermal decomposition temperature of zinc stearate of 250 ° C. or higher and lower than the melting point of PPS resin of 285 ° C., three-point bending is performed. It was found that the strength was particularly high. From these results, it was confirmed that in the molded products of these samples, the zinc oxide was reliably discharged to the outside of the molded product, and the strength of the molded product was greatly improved by the remaining PPS resin.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is the schematic diagram which showed the surface of the powder magnetic core produced by the manufacturing method of the powder magnetic core in embodiment of this invention. It is a schematic diagram which shows the aspect of the organic substance mixed with a composite magnetic particle. It is a schematic diagram which shows another aspect of the organic substance mixed with a composite magnetic particle. It is a schematic diagram which shows another aspect of the organic substance mixed with a composite magnetic particle. It is a graph which shows the specific example of the temperature change of the heat processing implemented to a molded object. It is a graph which shows another specific example of the temperature change of the heat processing implemented to a molded object. In an Example, it is a graph which shows the relationship between the maintenance temperature at the time of the heat processing of the 1st step | paragraph, and 3 point | piece bending strength.

Explanation of symbols

  10 metal magnetic particles, 20 insulating coating, 30 composite magnetic particles, 40, 50, 60 organic matter.

Claims (9)

A plurality of composite magnetic particles having metal magnetic particles and an insulating coating surrounding the surface of the metal magnetic particles, a first organic material having lubricity having a first melting point, and a second melting point larger than the first melting point Forming a molded body by pressure-molding a mixture containing a high-viscosity second organic substance having:
Subjecting the molded body to a first heat treatment at a temperature not lower than the first melting point and lower than the second melting point for not less than 30 minutes;
And a step of subjecting the compact to a second heat treatment at a temperature equal to or higher than the second melting point after the first heat treatment.   The first organic material includes higher fatty acid type, higher fatty acid metal salt type, wax type, higher alcohol type, polytetrafluoroethylene, high molecular weight polyethylene, thermoplastic polyamide, 6-nylon, 6-6 nylon and 6-12. The manufacturing method of the powder magnetic core of Claim 1 containing at least 1 type chosen from the group which consists of nylon.   3. The dust core according to claim 1, wherein the second organic material includes at least one selected from the group consisting of a PPS resin, a POM resin, a polyetherimide, a polyimide, a polyamideimide, and a non-thermoplastic resin. Production method.   4. The process according to claim 1, wherein the step of performing the first heat treatment includes a step of heat-treating the molded body at a temperature equal to or higher than a thermal decomposition temperature of the first organic substance and lower than the second melting point. The manufacturing method of the powder magnetic core as described in 1 ..   5. The method of manufacturing a dust core according to claim 1, wherein the step of performing the first heat treatment includes a step of heat-treating the compact for 60 minutes or more.   The step of performing the first heat treatment includes a step of heat-treating the molded body while maintaining a predetermined temperature in the range of the first melting point or more and less than the second melting point for 30 minutes or more. To 5. The method for producing a dust core according to any one of items 1 to 5.   6. The process according to claim 1, wherein the step of performing the first heat treatment includes a step of raising the temperature from the first melting point to the second melting point over a period of 90 minutes or more. Method for producing a powder magnetic core. A plurality of composite magnetic particles having metal magnetic particles and an insulating coating surrounding the surface of the metal magnetic particles and bonded together;
An organic matter interposed between the plurality of composite magnetic particles,
A dust core in which the frequency when the magnetic permeability is reduced by 5% from the magnetic permeability when an AC magnetic field of 50 Hz is applied is 5.0 kHz or more.   The powder magnetic core according to claim 8, wherein the three-point bending strength is 80 MPa or more.

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