JP2006100813A - Soft magnetic material, powder magnetic core, and method of producing powder magnetic core - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soft magnetic material, a powder magnetic core and a method of producing the powder magnetic core, which can suppress baking adhesion between a mold and a material to be molded during molding and prevent generation of black residues. <P>SOLUTION: A soft magnetic material contains an iron-base powder 30 having an insulating coating film 20 on the surface thereof and an ester wax 40. The ester wax 40 is added in an amount of not less than 0.02% by mass and not more than 0.6% by mass relative to the soft magnetic material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a soft magnetic material, a dust core, and a method for manufacturing a dust core.

  Conventionally, in order to suppress seizure between a mold and a molding object during molding, a method of reducing the frictional resistance at the interface between the mold and the molding object using a resin that is always solid has been used. I came. There are a case where the resin is added into the material to be molded and a case where the resin is directly sprayed on the mold. When the resin is added to the material, the resin in the vicinity of the surface of the molded product contributes to the reduction of the frictional resistance with the mold, so the amount of the added resin needs to be 0.6% by mass or more. Therefore, it causes a decrease in density of the molded body. Moreover, when spraying resin on a metal mold | die, there exists a subject that it is difficult to spray uniformly on a metal mold | die, especially a complicated-shaped metal mold | die, and an unevenness | variation is easy to occur.

In order to solve these problems, a method of adding a polymer oil such as wax to an iron-based material has been proposed. For example, Japanese Patent Publication No. 2003-509582 discloses a mechanism for expressing lubricity by adding a polycarboxylic acid amide wax, and Japanese Patent Publication No. 10-501270 is based on the addition of an amide type oligomer. A lubrication mechanism is shown.
Special table 2003-509582 gazette Japanese National Patent Publication No. 10-501270

  The above amide waxes and amide type oligomers show excellent lubricity, but the amide bond is strong, so when applied to soft magnetic materials that require heat treatment at a relatively low temperature, it cannot be completely decomposed and a black residue remains. There was a problem of remaining.

  Therefore, an object of the present invention is to provide a soft magnetic material, a powder magnetic core, and a method for manufacturing a powder magnetic core capable of suppressing seizure between a mold and a molding object during molding and preventing black residue from being generated. Is to provide.

  Moreover, it is conceivable that the fluidity of the powder mixture is extremely reduced only by adding and mixing the wax.

  Therefore, a further object of the present invention is to produce a soft magnetic material, a dust core and a dust core capable of improving the density, strength and properties of the dust core by improving the fluidity of the powder mixture. Is to provide a method.

  The soft magnetic material of the present invention has an iron-based powder having an insulating coating on the surface and at least one wax containing an ester wax, and the wax containing the ester wax is 0.02% by mass or more and 0.6% by mass. It is characterized by including the following.

  According to the soft magnetic material of the present invention, since the lubricity is improved by using the ester wax, it is possible to suppress seizure between the mold and the molding object during molding. In addition, it is desirable that the ester wax has a narrow melting temperature range (sharp melt type), but it can be easily decomposed by heat treatment at a relatively low temperature, so that heat treatment after molding (for example, above the decomposition temperature of the wax in the atmosphere) It is possible to prevent a residue from being generated by heat treatment at a temperature of (5).

  The addition amount of the wax containing the ester wax is set to 0.02% by mass or more and 0.6% by mass or less because if the addition amount is less than 0.02% by mass, the lubricity with the mold is insufficient and the molded product This is because when the surface has streaks and the addition amount is more than 0.6% by mass, the density is lowered and good soft magnetic properties cannot be obtained. The amount of wax added is preferably 0.2% by mass or less. A high-density molded body is obtained at 0.02 mass% or more and 0.2 mass% or less.

  As described above, the inventors of the present application can suppress seizure between the mold and the molding object at the time of molding by optimizing the wax type and the addition amount thereof, and can prevent the generation of a black residue. Realized soft magnetic material.

  In the soft magnetic material, preferably, the wax containing the ester wax has an average particle size of 0.5 μm or more and not more than the average particle size of the iron-based powder having an insulating coating.

  Usually, ester wax is used at several hundred μm to several mm. This is because the hardness of the ester wax is low and difficult to pulverize, but a wax having a preferable particle size can be obtained by freezing and pulverizing the wax with liquid nitrogen or the like.

  Further, if the average particle size of the wax is larger than 200 μm, which is the average particle size of the iron-based powder, the dispersibility of the wax is deteriorated, and there is a possibility of unevenness when the wax exudes between the mold and the molded body. is there. On the other hand, if the average particle size of the wax is smaller than 0.5 μm, the waxes are aggregated and the mixing property of the wax and the soft magnetic material is deteriorated, which may cause unevenness when the wax exudes. The average particle size of the wax is more preferably 0.5 μm or more and 50 μm or less.

  In the soft magnetic material, the melting point of the wax containing the ester wax is preferably 100 ° C. or lower.

  If the melting point of the wax is higher than 100 ° C., even if the mold temperature is set to be equal to or higher than the melting point of the wax, the temperature of the molded body during normal pressing hardly rises to 100 ° C. or more. Further, the lower the melting point of the wax, the better. However, when the wax is too low, it dissolves during powder mixing or storage, which adversely affects the fluidity of the powder. Therefore, it is preferable that the wax has a melting point that exists as a solid during storage and dissolves during pressing. Furthermore, the melting point of the wax is preferably 50 ° C. or lower. When the temperature is 50 ° C. or lower, even if the mold temperature is not forcibly increased, the temperature of the molded body at the time of pressing becomes 50 ° C. or higher due to frictional heat.

  In the above soft magnetic material, the viscosity of the wax containing the ester wax is preferably 15 mPa · s or less.

  The viscosity of the wax is very important for the time until the wax exudes to the surface and the homogeneity of the lubricant component on the surface. If the viscosity of the wax is greater than 15 mPa · s, even if it dissolves during press molding, it does not spread uniformly at the boundary between the mold and the molded body at the time of extraction, which causes seizure and streaks on the molded body surface.

  In the soft magnetic material, preferably, a solid lubricant that exhibits lubricity by peeling in layers is added in an amount of 0.0005 mass% to 0.1 mass%.

  When the addition amount of the solid lubricant is more than 0.1% by mass, the density and strength of the molded body are lowered and the fluidity is deteriorated. This is because the solid lubricant has a function of lowering the frictional resistance between the iron-based powder and the wax, but the lubricity between the solid lubricants is poor. On the other hand, if the addition amount of the solid lubricant is less than 0.0005% by mass, a measurement error with respect to a change in the addition amount becomes large, and characteristics such as magnetic characteristics are not stable. Thus, by making the addition amount of the solid lubricant 0.0005% by mass or more and 0.1% by mass or less, good lubricity can be expressed with respect to the powder in which wax is reduced and fluidity is lowered. . In order to improve density, strength, and magnetic properties, the amount of solid lubricant added is preferably smaller, and in experiments, a better result is obtained at 0.01% by mass or less.

In the soft magnetic material, the solid lubricant preferably has a particle size of 1.5 μm or less.
When the particle size of the solid lubricant is 1.5 μm or less, the fluidity is remarkably improved even if only a small amount of the solid lubricant is added. The finer the solid lubricant, the better, but the current technology can only grind to about 0.5 μm.

In the above soft magnetic material, the solid lubricant is preferably a metal soap.
In particular, when a small amount of zinc stearate powder is added, good fluidity is exhibited, and the effects of improving quality stability, density stability, strength and magnetic properties are obtained.

  The soft magnetic material preferably contains one or more resins selected from the group consisting of thermoplastic resins, non-thermoplastic resins, thermosetting resins, and non-thermosetting resins.

The dust core of the present invention is manufactured using each of the soft magnetic materials described above and has a density of 7.3 g / cm ³ or more. This is because excellent soft magnetic properties can be achieved by setting the compact density to 7.3 g / cm ³ or more.

  A method of manufacturing a dust core according to the present invention is a method of manufacturing the above-described dust core, and includes a step of compression-molding each of the above soft magnetic materials using a mold to obtain a molded body. Sets the temperature of the soft magnetic material below the melting point of the wax containing the ester wax, and sets the temperature of the mold above the temperature at which the wax containing the ester wax exists in the liquid state at the interface between the mold and the soft magnetic material. It is characterized by being performed. In particular, by lowering the melting point of the wax (50 ° C. or less), the powder and mold can exude even in cold forming where the temperature is not raised.

  According to the method for manufacturing a dust core of the present invention, the temperature of the soft magnetic material is set to be equal to or lower than the melting point of the wax, and the temperature of the mold is liquid at the interface between the mold and the compact core of the dust core. Since the temperature is set to be equal to or higher than the existing temperature, it is possible to allow the wax to exude in a liquid state at the interface during compression molding. Thereby, the seizure between the mold and the molding object during molding can be suppressed.

  Preferably, in the above method for producing a powder magnetic core, the molded body is further provided with a step of performing a heat treatment at a temperature equal to or higher than the decomposition temperature of the wax containing the ester wax in the air atmosphere.

  As a result, the wax component that has oozed out on the surface of the molded body during compression molding and then solidified is decomposed by the heat treatment, and a good surface state is obtained.

  As described above, according to the soft magnetic material, the dust core and the dust core manufacturing method of the present invention, it is possible to suppress seizure between the mold and the molding object during molding and to produce a black residue. Can be prevented.

  In addition, by adding a lubricant that exhibits lubricity by peeling off into layers, the fluidity of the powder mixture is improved, thereby further suppressing the seizure between the mold and the molding object during molding. it can.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a soft magnetic material according to an embodiment of the present invention. Referring to FIG. 1, the soft magnetic material is, for example, a mixed powder having iron-based powder 30 and ester wax 40. The iron-based powder 30 includes iron-based particles 10 and an insulating coating 20 formed on the surface thereof. The ester wax 40 is contained in an amount of 0.02% by mass to 0.6% by mass with respect to the mixed powder (soft magnetic material).

  The iron-based particles 10 include, 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 iron-based particles 10 may be a single metal or an alloy.

  The insulating coating 20 is formed, for example, by subjecting the iron-based particles 10 to phosphoric acid treatment. Preferably, the insulating coating 20 contains an oxide. As the insulating coating 20 containing this oxide, in addition to iron phosphate containing phosphorus and iron, manganese phosphate, zinc phosphate, calcium phosphate, aluminum phosphate, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, etc. The oxide insulator can be used. The insulating coating 20 may be formed in one layer as shown in the figure, or may be formed in multiple layers.

  The ester wax 40 is a wax having an ester bond. An ester bond is a bond represented by X-O-R '(X is an oxo acid minus H), which hydrolyzes in the presence of an acid or base to become an oxo acid and an alcohol. It is.

  Desirable examples of the ester wax described above include those described in JP-A No. 2002-212142 and JP-A No. 2004-059744. Specifically, a. A linear saturated monocarboxylic acid having 14 to 30 carbon atoms; b. Examples thereof include those obtained by a condensation reaction with a linear saturated monohydric alcohol having 14 to 30 carbon atoms or a 2 to 6 polyhydric alcohol having 2 to 30 carbon atoms. These ester waxes are sharp melt type waxes having a narrow melting point range.

  In ordinary ester waxes, branched fatty acids and polyvalent carboxylic acids are also used as the component a. However, since the viscosity of the ester increases, it does not spread evenly at the boundary between the mold and the molded product even when it is melted during molding. For this reason, it causes image appearance defects such as image sticking and streaks of the molded body.

  In addition, a wax using a branched fatty acid or polyvalent carboxylic acid as the component a is less likely to decompose during heat treatment than a wax using a linear saturated monocarboxylic acid having 14 to 30 carbon atoms as the component a. There is also a problem that residues are generated.

  Therefore, by using a wax using a linear saturated monocarboxylic acid having 14 to 30 carbon atoms as the component a, a lubrication effect can be stably obtained, and a good product without residue after heat treatment can be obtained. Obtainable.

  In addition to amide waxes, there are hydrocarbon waxes (paraffin wax, polyethylene wax) as waxes with low melting points and low viscosity. Ester waxes are synthesized with a narrower melting point temperature range than these waxes. be able to. Accordingly, the wax can be efficiently melted in a short time, and the boundary portion between the mold and the molded body can be effectively lubricated.

  The average particle diameter of the ester wax 40 is preferably 0.5 μm or more and not more than the average particle diameter of the iron-based powder 30. Moreover, it is preferable that melting | fusing point of the ester wax 40 is 100 degrees C or less. Moreover, it is preferable that the viscosity at the time of melt | dissolution of the ester wax 40 is 15 mPa * s or less.

  The soft magnetic material preferably contains, for example, an organic substance (not shown). These organic materials include thermoplastic resins such as thermoplastic polyimide, thermoplastic polyamide, thermoplastic polyamideimide, polyphenylene sulfide, polyamideimide, polyethersulfone, polyetherimide or polyetheretherketone, wholly aromatic polyester, wholly aromatic. Non-thermoplastic resin such as aromatic polyimide or high molecular weight polyethylene, thermosetting resin, non-thermosetting resin, zinc stearate, lithium stearate, calcium stearate, lithium palmitate, calcium palmitate, lithium oleate or Higher fatty acids such as calcium oleate can be used. Moreover, these can also be mixed and used for each other. High molecular weight polyethylene refers to polyethylene having a molecular weight of 100,000 or more.

  In addition to the iron-based powder 30, the ester wax 40, and the organic substance, the soft magnetic material preferably has a solid lubricant 50 that exhibits lubricity by peeling in layers as shown in FIG. The solid lubricant 50 is preferably added to the soft magnetic material in an amount of 0.0005 mass% to 0.1 mass%.

  The particle size of the solid lubricant 50 is preferably 1.5 μm or less. The solid lubricant 50 is preferably a metal soap.

Next, a method for manufacturing a dust core using the soft magnetic material of the present embodiment will be described.
3 and 4 are schematic cross-sectional views showing a method of manufacturing a dust core using a soft magnetic material according to an embodiment of the present invention in the order of steps. Referring to FIG. 1, by subjecting iron-based particles 10 to a phosphoric acid treatment, an insulating coating 20 is formed on the surface of iron-based particles 10 to produce iron-based powder 30. The insulating coating 20 functions as an insulating layer between the iron base particles 10. By covering the iron-based 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 iron base particles 10, and can reduce the iron loss of the powder magnetic core resulting from an eddy current.

  The average thickness of the insulating coating 20 is preferably 5 nm or more and 100 nm or less. The average thickness mentioned here is a film composition obtained by compositional analysis (TEM-EDX: transmission electron microscope energy dispersive X-ray spectroscopy) and by inductively coupled plasma-mass spectrometry (ICP-MS). Considering the amount of element to be obtained, the equivalent thickness is derived, and further, the film is directly observed by a TEM photograph, and it is determined by confirming that the order of the equivalent thickness derived earlier is an appropriate value. Means something.

  Next, the ester wax 40 is prepared. This ester wax is formed to have the average particle size, melting point and viscosity as described above.

  Also prepare organic matter. As described above, the organic material is formed of, for example, a thermoplastic resin, a non-thermoplastic resin, a thermosetting resin, a non-thermosetting resin, a higher fatty acid-based lubricant, or the like.

  In addition, when the solid lubricant 50 shown in FIG. 2 is added, a solid lubricant is also prepared. This solid lubricant is formed of a material that exhibits lubricity by peeling off in layers.

  Using a V-type mixer, the iron-based powder 30, the ester wax 40, the organic substance, and a solid lubricant added as necessary are mixed. At this time, the mixing ratio is adjusted so that the ratio of the ester wax 40 to the mixed powder is 0.02 mass% or more and 0.6 mass% or less. Further, the mixing ratio is adjusted so that the ratio of the solid lubricant 50 to the mixed powder is 0.0005 mass% or more and 0.1 mass% or less.

  The mixing method is not particularly limited. For example, mechanical alloying method, vibration ball mill, planetary ball mill, mechanofusion, coprecipitation method, chemical vapor deposition method (CVD method), physical vapor deposition method (PVD method), plating Any of the method, sputtering method, vapor deposition method or sol-gel method can be used.

  Referring to FIG. 3, a pressure forming process is performed on the obtained mixed powder. First, the band heater 77 of the mold apparatus is energized to heat the inner wall 73 of the die 72 to a temperature higher than the temperature at which the ester wax 40 exists in liquid form at the interface between the inner wall 73 of the die 72 and the mixed powder. The temperature of the mixed powder is set to a temperature not higher than the melting point of the ester wax 40.

  Next, a shoe (not shown) is positioned above the space 74 surrounded by the inner wall 73, and the mixed powder 15 obtained in the previous step is supplied from the shoe toward the space 74.

  Referring to FIG. 4, upper punch 80 is positioned above space 74. The upper punch 80 is moved downward, and the mixed powder 15 is pressure-molded at a pressure of 700 MPa to 1500 MPa, for example. At this time, the atmosphere for pressure molding is preferably an inert gas atmosphere or a reduced pressure atmosphere. In this case, the mixed powder can be prevented from being oxidized by oxygen in the atmosphere.

  During the pressure molding, the ester wax 40 oozes out as a liquid at the interface between the inner wall 73 of the die 72 and the mixed powder 15, thereby suppressing seizure between the inner wall 73 and the mixed powder 15. Further, since the solid lubricant 50 has a function of reducing the frictional resistance between the iron-based powder 30 and the wax 40, the mixed powder 15 whose fluidity has been reduced by the addition of the wax exhibits good lubricity, and the density of the molded body. Contributes to improvement, strength improvement, and magnetic property improvement. Further, the organic substance functions as a lubricant between the iron-based powders 30 and suppresses the introduction of strain into the iron-based particles 10 during pressure molding or the destruction of the insulating coatings 20 due to strong friction.

  Thereafter, the molded body 16 obtained by pressure molding is extracted from the space 74. FIG. 5 shows a schematic cross-sectional view showing the vicinity of the surface of the molded body 16 thus obtained. Referring to FIG. 5, the molded body 16 includes a plurality of insulating coated iron-based particles (iron-based powder) 30 composed of iron-based particles 10 and an insulating coating 20 that surrounds the surface of the iron-based particles 10. An ester wax 40 and an organic substance are interposed between the plurality of insulating coated iron-based particles 30. Each of the plurality of insulating coated iron-based particles 30 is bonded mainly by an organic substance, and is also bonded by meshing unevenness of the insulating coated iron-based particles 30. The ester wax 40 oozes out and solidifies on the surface of the molded body 16. In addition, when the solid lubricant 50 is added, the solid lubricant 50 is interposed between the plurality of insulating coated iron-based particles 30 in addition to the ester wax 40 and the organic matter as shown in FIG. Since the ester wax 40 oozes out during molding, the amount of the ester wax 40 existing between the insulating coated iron-based particles 30 is reduced.

  Next, the molded body 16 is heat-treated at a temperature equal to or higher than the decomposition temperature of the ester wax 40 in an air atmosphere. As a result, the component of the ester wax 40 that has oozed out on the surface of the molded body 16 during compression molding and then solidified is thermally decomposed, and a good surface state of the molded body 16 is obtained. As shown in FIG. 7, the ester wax is removed from the surface of the heat-treated molded body 17 subjected to this heat treatment by thermal decomposition. In addition, when the solid lubricant 50 is added, the solid lubricant 50 may be interposed in addition to the organic matter between the plurality of insulating coated iron-based particles 30 as shown in FIG. When the solid lubricant 50 is also thermally decomposed by the heat treatment, the solid lubricant is also removed as shown in FIG.

  Further, by performing the heat treatment, it is possible to remove distortion and dislocation generated in the molded body 16 during pressure molding.

Finally, the dust core is completed by subjecting the heat-treated molded body 17 to appropriate processing such as extrusion and cutting. The powder magnetic core thus obtained preferably has a density of 7.3 g / cm ³ or more, whereby excellent soft magnetic properties can be obtained.

  The dust core produced in this way can be used as products such as electronic components such as choke coils, switching power supply elements and magnetic heads, various motor components, solenoids, various magnetic sensors and various electromagnetic valves. .

  In the above description, the ester wax is used as the wax. However, the wax may be a wax containing an ester wax.

  Examples of the present invention will be described below.

  As a sample of iron-based powder, Somaloy 550 (average particle size 210 μm: measured by Nikkiso particle size distribution measuring device) was used. An ester wax was used as the wax. The prepared ester waxes are the waxes A to I shown in Table 1, and the characteristics of the waxes A to I are shown in Table 1 together.

  First, mixed powders 1 to 7 in which wax D was blended with Somaloy 550 in an addition amount shown in Table 2 were prepared, and each of mixed powders 1 to 7 was mixed with a V-type mixer for 1 hour.

  Next, the mold was set to each temperature shown in Table 3 and press molding with a thickness of 30 mm was performed using a φ20 mm mold, and the surface condition of the mold was evaluated. The press pressure was 1000 MPa. Table 3 shows the evaluation of the obtained surface state.

  In Table 3 above, “x” indicates that there is a streak due to seizure, “Δ” indicates that there is a streak but there is no streak, and “◯” indicates that there is no streak. In addition, regarding the samples of Δ and ◯, the dissolved wax was attached to the surface of the molded body. With this effect, it is considered that seizure at the time of molding could be prevented and a good surface condition was obtained.

  From the above results, it has been found that when the molding is performed at a melting point of the wax or higher, a molded article having a very good surface state can be obtained even if pressing is usually performed under the condition of seizure.

  When the amount of the wax added is less than 0.02% by mass as in Sample 1, it is considered that the surface of the molded body was streaked because the lubricity with the mold became insufficient due to the lack of wax.

  Next, the density was measured with respect to C (mold temperature: 90 ° C.) and D (mold temperature: 120 ° C.) of Samples 2 to 7 which were found to have excellent moldability. The results are shown in Table 4.

  From the results in Table 4, it is understood that the mold temperature is preferably as high as possible within the pressable range, and the amount of wax added is desirably 0.6% by mass or less in order to increase the density.

  In the same manner as in Example 1, mixed powders in which waxes A, B, D, G, H, and I were blended at an addition amount of 0.2 mass% with respect to Somaloy 550 were prepared, and each of the mixed powders was V-shaped. Molding evaluation was performed on a sample obtained by mixing with a mixer for 1 hour by using a φ20 mm mold and setting the mold temperature to 90 ° C. The press pressure was 1000 MPa. Table 5 shows the surface state and density of the molded body at that time.

  From the results in Table 5, it can be seen that the density of waxes A and I is lower than the other waxes. Regarding the wax A, it is considered that the average particle size of the wax is too small as 0.3 μm and is agglomerated. For this reason, if good dispersion of the wax is possible, a high-density molded body may be obtained. Regarding sample I, the wax particles are 212 μm larger than the average particle size of Somaloy 550, which is an iron-based powder, so that a sufficient amount of wax does not exist on the surface of the molded body, resulting in generation of streaks on the surface. It is considered that no wax exudes between the molded body and the mold, so that the wax remains inside the molded body, causing a decrease in density.

  This shows that the average particle size of the wax is preferably 0.5 μm or more and not more than the average particle size of the iron-based powder having an insulating coating.

  As in Example 2, mixed powders prepared by blending waxes C, D, E, and F at an addition amount of 0.2 mass% with respect to Somaloy 550 were prepared, and each of the mixed powders was subjected to a V-type mixer for 1 hour. Molding evaluation was performed on a sample obtained by mixing using a φ20 mm mold and setting the mold temperature to 90 ° C. The press pressure was 1000 MPa. Table 6 shows the surface state and density of the molded body at that time.

  From the above results, when the viscosity at the time of dissolution of the wax is higher than 15 mPa · s, such as 17 mPa · s, the viscosity is high, and it takes time to ooze out during press molding, so the amount remaining in the molded body is large. As a result, the anti-seizure property is deteriorated and the density is not increased. Viscosity can be eliminated by raising the mold temperature because it decreases by raising the temperature, but the mold temperature that can be raised is limited for use in the press, so low viscosity (15 mPa · s or less at low temperature) It is preferable to use a wax indicating In addition, for wax C, when the mold temperature is set to room temperature (cold molding) and molding is performed under the same other conditions, a density and surface state almost equal to those when the mold temperature is 90 ° C. is obtained. Thus, when the melting point of the wax was 50 ° C. or lower, it was confirmed that the exudation was confirmed even in cold forming, and it was possible to form a molded article having a high density and a good surface state.

Using amide wax, paraffin, and oleic acid having the same particle size, melting point, and viscosity behavior at the time of dissolution, a sample was prepared in the same manner as in Examples 1 to 3, and press molding at 90 ° C. As a result, it was possible to obtain a molded article having a good surface property similar to the case of using wax D and a high density of 7.58 g / cm ³ . Thereafter, the sample using amide wax, paraffin, and oleic acid and the sample using wax D were simultaneously placed in a heat treatment furnace, and heat treatment was performed in an atmosphere of 500 ° C. As a result, in the sample using wax D, the wax adhering to the surface was clearly decomposed and volatilized, whereas in the sample using amide wax, paraffin and oleic acid, the wax remained as a black residue after heat treatment. all right. The black residue can be removed by brushing or the like, but in the case of considering mass production, ester wax is desirable.

  To a soft magnetic material prepared by adding 0.2% by weight of wax D to Somaloy 550 and mixing for 1 hour with a V-type mixer, metal soap (zinc stearate) as a solid lubricant was further added. Were added in various ways and mixed for another hour with a V-type mixer. The average particle diameter of the solid lubricant was 0.8 μm, 1.3 μm, 2.0 μm, and 15 μm, respectively, and the addition amount of the solid lubricant having each average particle diameter was changed as shown in FIGS.

  The result of measuring the apparent density of each mixed powder thus obtained is shown in FIG. Further, FIG. 10 shows the result of evaluating the flowability by measuring the time required for dropping when 50 g of the above mixed powder is put in a pipe having an orifice diameter of 4 mm.

  From the results of FIG. 9 and FIG. 10, when the apparent density and flowability are evaluated, when the addition amount of metal soap as a lubricant is 0.1% by mass or less, the apparent density and flowability are when no lubricant is added. It can be seen that it may be equal to or better than. This tendency is the same even when the amount of wax is changed, and the amount of wax added within the scope of the present invention is preferably in the range of 0.0005% by mass to 0.1% by mass with metal soap.

  Further, when the addition amount of the metal soap is 0.05% by mass or less, the apparent density is better than when no lubricant is added in each average particle diameter of 0.8 μm, 1.3 μm, 2.0 μm, and 15 μm. Become. Further, when the addition amount of the metal soap is 0.075% by mass or less, in each average particle diameter of 0.8 μm, 1.3 μm, 2.0 μm, and 15 μm, the flowability is better than when no lubricant is added. Become. This improvement in apparent density and flowability is essential for product stability (inhibition of density variation), and if it is less than 0.0005% by mass, measurement errors due to changes in the amount added increase characteristics such as magnetic properties. Is not stable, 0.0005% by mass or more is preferable.

  In addition, when h-BN (hexagonal boron nitride) known as a layered lubricant was added, similar results were obtained in terms of apparent density and flowability.

These soft magnetic powder, when the density of 7.3 g / cm ³ or more, because it has a particularly excellent magnetic properties, the density of the molded body is preferably in the 7.3 g / cm ³ or more.

  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.

  The present invention provides a soft magnetic material having an iron-based powder having an insulating coating on its surface, a dust core obtained by molding the soft magnetic material, a method for forming a dust core, and heat treatment of the dust core. It can be applied particularly advantageously to the heat-treated molded body.

It is a schematic diagram which shows the soft-magnetic material in one embodiment of this invention. It is a schematic diagram which shows the other example (example which added the solid lubricant) of the soft-magnetic material in one embodiment of this invention. It is a schematic sectional drawing which shows the 1st process of the manufacturing method of the powder magnetic core using the soft-magnetic material in one embodiment of this invention. It is a schematic sectional drawing which shows the 2nd process of the manufacturing method of the powder magnetic core using the soft-magnetic material in one embodiment of this invention. It is a cross-sectional schematic diagram which shows the surface vicinity of the molded object formed using the soft-magnetic material in one embodiment of this invention. It is a cross-sectional schematic diagram which shows the surface vicinity of the other example (example which added the solid lubricant) of the molded object formed using the soft-magnetic material in one embodiment of this invention. It is a cross-sectional schematic diagram which shows the surface vicinity of the heat processing molded object formed using the soft-magnetic material in one embodiment of this invention. It is a cross-sectional schematic diagram which shows the surface vicinity of the other example (example which added the solid lubricant) of the heat processing molded object formed using the soft-magnetic material in one embodiment of this invention. It is a figure which shows the result of having measured the apparent density of the mixed powder at the time of changing the addition amount of the solid lubricant of each average particle diameter. It is a figure which shows the result of having evaluated the flowability of the mixed powder at the time of changing the addition amount of the solid lubricant of each average particle diameter.

Explanation of symbols

  10 Iron-based particles, 15 Mixed powder, 16 Molded body, 17 Heat-treated molded body, 20 Insulating coating, 30 Iron-based powder (insulating coated iron-based particles), 40 Ester wax, 50 Solid lubricant, 72 Die, 73 Inner wall, 74 Space, 77 band heater, 80 upper punch.

Claims (11)

  It has iron base powder having an insulating coating on the surface and at least one kind of wax containing ester wax, and contains 0.02% by mass or more and 0.6% by mass or less of the wax containing the ester wax. Soft magnetic material.   2. The soft magnetic material according to claim 1, wherein an average particle size of the wax containing the ester wax is 0.5 μm or more and an average particle size of the iron-based powder having the insulating coating. .   The soft magnetic material according to claim 1, wherein a melting point of the wax containing the ester wax is 100 ° C. or less.   The soft magnetic material according to claim 1, wherein a viscosity of the wax containing the ester wax when dissolved is 15 mPa · s or less.   The soft magnetic material according to claim 1, wherein 0.0005 mass% to 0.1 mass% of a solid lubricant that exhibits lubricity by peeling in layers is added.   The soft magnetic material according to claim 5, wherein a particle size of the solid lubricant is 1.5 μm or less.   The soft magnetic material according to claim 5 or 6, wherein the solid lubricant is a metal soap.   The soft resin according to any one of claims 1 to 7, comprising at least one resin selected from the group consisting of a thermoplastic resin, a non-thermoplastic resin, a thermosetting resin, and a non-thermosetting resin. Magnetic material. A dust core produced by using the soft magnetic material according to claim 1 and having a density of 7.3 g / cm ³ or more. A method for producing the dust core according to claim 9, comprising:
Comprising a step of compression-molding the soft magnetic material according to claim 1 using a mold to obtain a molded body,
In the molding, the temperature of the soft magnetic material is set to be equal to or lower than the melting point of the wax containing the ester wax, and the temperature of the mold is set between the mold and the soft magnetic material. A method for producing a dust core, wherein the method is performed at a temperature higher than the temperature existing in a liquid state at the interface.   The method of manufacturing a dust core according to claim 10, further comprising a step of heat-treating the molded body at a temperature equal to or higher than a decomposition temperature of the wax containing the ester wax in an air atmosphere.

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