JP4305222B2 - Method for producing a green compact - Google Patents

Description

  The present invention generally relates to a method for manufacturing a soft magnetic material and a powder compact, and more specifically to a soft magnetic material including a plurality of iron particles and a method for manufacturing a powder compact.

In recent years, in products 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. In addition to such magnetic parts, a compacted body obtained by pressure-forming iron powder may be used as a structural material for manufacturing machine parts and the like.
JP 2002-246219 A

  For the production of these green compacts, iron particles purified by various atomization methods or reduction methods are usually used. In the atomization method, dissolved iron is sprayed using high-pressure gas or water, and iron particles are obtained by carrying out processes such as pulverization and classification on the obtained powdered iron. In the reduction method, iron ore and mill scale are reduced with coke, and then heat treatment is performed in a hydrogen atmosphere to obtain iron particles. Therefore, iron particles purified by these methods go through a process of being rapidly cooled in the production process. In this case, extremely large strain and stress are applied to the inside of the iron particles, and the hardness of the iron particles to be refined increases. For this reason, at present, iron particles having a Vickers hardness HV in the range of about 800 to 1100 are used in the production of a green compact.

  On the other hand, a compacting body expresses intensity | strength when an iron particle carries out plastic deformation in the process of a pressure molding, and iron particles mutually intertwined. In the case of a sintered body, the strength is relatively greatly improved by metal bonding and diffusion between particles during sintering. However, in the case of a compacted body (particularly a dust core), the heat treatment can be performed even if heat treatment is performed. Since the temperature is low enough that sintering does not occur between the particles, the bonding force between the particles is not sufficient. For this reason, in order to produce a compacting body with a high strength, it is necessary to entangle iron particles in a more complicated manner in the pressure forming step.

  However, as described above, the hardness of the iron particles used for producing the green compact is high. When the hardness is high, the plastic deformation of the iron particles is difficult to proceed during pressure molding, and the iron particles are less likely to be entangled with each other. For this reason, sufficient strength cannot be obtained, and there arises a problem that when the iron particles fall off from the surface of the green compact or when processing such as cutting is performed, the compact is damaged.

Accordingly, an object of the present invention is to solve the above problems, it is to provide a method for producing a pressure powder compact you realize green compact having a high strength.

  When it is desired to improve the strength of a green compact in which iron particles are pressure-molded, there is a concept of improving the hardness and strength of the iron particles themselves constituting the green compact. However, as a result of intensive studies by the inventors, it has been found that it is more effective to reduce the hardness of the iron particles in order to improve the strength of the green compact. As a result, the present invention described below has been completed.

The manufacturing method of the compacting body according to this invention is a manufacturing method of the compacting body using iron powder. The iron powder is an aggregate of a plurality of iron particles having a Vickers hardness HV of less than 800. The specific surface area of the iron particles measured by the gas adsorption method (BET method) is α and measured by a laser scattering diffraction method. When the apparent specific surface area of the iron particles calculated from the average particle diameter is β, the iron particles satisfy the relationship α / β ≧ 2.5. The manufacturing method of a compacting body includes a step of putting a plurality of iron particles into a mold and a step of forming a compact by pressing the plurality of iron particles. The step of adding a plurality of iron particles to the mold includes the step of adding the first organic material composed of at least one of a thermoplastic resin and a non-thermoplastic resin to a ratio of the first organic material to the molded body of 0.001% by mass or more. A step of adding to a plurality of iron particles so as to be 0.01% by mass or less is included. The iron particles referred to here are particles containing iron with a purity of 95% to 100%.

According to the method for producing a compacted body thus configured, since the Vickers hardness HV of the iron particles is less than 800, the iron particles are easily plasticized at the time of pressure molding when producing the compacted body. Can be deformed. Thereby, since a plurality of iron particles are intertwined in a complicated manner and joined in a state of being engaged with each other, a compacted body having high strength can be realized.
Further, since the ratio of the actual specific surface area α to the apparent specific surface area β of the iron particles is specified to be 2.5 or more, the surface of the iron particles is formed in a large uneven shape. Thereby, since the several iron particle can be entangled more complicatedly at the time of the press molding at the time of producing a compacting body, the intensity | strength of a compacting body can further be improved.
Further, the first organic material is provided on the green compact in a state of being interposed between the plurality of iron particles, and firmly bonds the plurality of iron particles. Thereby, the intensity | strength of a compacting body can further be improved. At this time, when the ratio of the first organic substance is 0.001% by mass or more, the above-described effects can be sufficiently obtained.

The surface of the iron particles is surrounded by an insulating coating . In the manufacturing method of the compacting body comprised in this way, since an insulating film exists between adjacent iron particles, when it is set as a compacting body, the metal bond between iron particles is inhibited significantly. Further, the iron particles cannot be meshed intricately due to the lubricity of the insulating coating during pressure molding when producing the green compact. For these reasons, it is difficult to obtain a green compact having high strength. Therefore, the present invention can be effectively used for a soft magnetic material having such an insulating coating.

Preferably, the insulating coating has an average thickness of 5 nm to 100 nm. According to the method for manufacturing a green compact formed as described above, since the average thickness of the insulating coating is 5 nm or more, the tunnel current flowing through the coating is suppressed, and the eddy current loss due to the tunnel current is increased. Can be suppressed. Moreover, since the average thickness of an insulating film is 100 nm or less, when a compacting body is produced using a soft magnetic material, the distance between iron particles does not become too large. Thereby, it can prevent that a demagnetizing field generate | occur | produces between iron particles, and can suppress the increase in the hysteresis loss resulting from generation | occurrence | production of a demagnetizing field. Further, the volume ratio of the nonmagnetic layer in the soft magnetic material can be suppressed, and the saturation magnetic flux density can be prevented from decreasing.

Preferably, in the step of adding a plurality of iron particles to the mold, the second organic material composed of the higher fatty acid-based lubricant is used, and the ratio of the second organic material to the molded body is 0.001% by mass or more and 0.2% by mass. The process of adding to a some iron particle so that it may become% or less is included. According to the method for manufacturing a compacted body thus configured, the second organic material is interposed between adjacent iron particles in the step of pressure-molding a plurality of iron particles, and the iron particles rub against each other violently. To prevent that. Thereby, it can suppress that distortion is introduce | transduced inside an iron particle and the hysteresis loss of a compacting body increases. In addition, when an insulating film is formed on the surface of the iron particles, the insulating film is prevented from being destroyed during pressure molding. Thereby, reduction of the eddy current loss of a compacting body can be aimed at.

  At this time, when the ratio of the second organic material is 0.001% by mass or more, the above-described effects can be sufficiently obtained. Moreover, the ratio of the 2nd organic substance is 0.2 mass% or less, the volume ratio of the nonmagnetic layer which occupies for a compacting body can be suppressed, and it can suppress that a saturation magnetic flux density falls. In addition, it is possible to prevent the strength of the green compact from being reduced due to the second organic material having a high lubricity.

  Preferably, the step of introducing the plurality of iron particles into the mold includes a step of applying a lubricant to the inner wall of the mold. According to the manufacturing method of the compacting body comprised in this way, favorable lubricity can be obtained between an iron particle and a metal mold | die at the time of pressure molding. Thereby, while increasing the density of a compacting body, intensity | strength can further be improved.

  Preferably, the step of introducing the plurality of iron particles into the mold includes a step of heating at least one of the inner wall of the mold and the plurality of iron particles to a temperature of 40 ° C. or higher. According to the manufacturing method of the compacting body comprised in this way, the distortion which exists in an iron particle can be reduced and the hysteresis loss of a compacting body can be reduced. Further, the first organic substance added to the plurality of iron particles is softened, and the first organic substance can be sufficiently spread between the plurality of iron particles. Thereby, while increasing the density of a compacting body, intensity | strength can further be improved.

As described above, according to the present invention, it is possible to provide a manufacturing method of the pressure powder compact you realize green compact having a high strength.

  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 includes a plurality of iron particles 10 having a Vickers hardness HV of less than 800. The Vickers hardness HV of the iron particles 10 is more preferably 700 or less. The Vickers hardness HV of the iron particles 10 is measured by a micro Vickers hardness test method defined in JIS standard Z2244, and is obtained, for example, by the method described below. In addition, in this specification, the aggregate | assembly of the some iron particle 10 is called iron powder.

  FIG. 2 is an explanatory diagram for explaining a method of measuring the Vickers hardness HV of the iron particles shown in FIG. Referring to FIG. 2, iron powder is mixed with liquid or powdery resin, and the temperature is increased (or by chemical reaction) to dissolve the resin. Thereafter, the resin is hardened and a resin 61 in which iron powder is enclosed is produced. Next, the surface 61a of the resin 61 is lapped to form the flat portion 10a used for the hardness test on the iron particles 10. A test square square indenter 63 is applied to the flat surface portion 10a, and an indentation 64 is formed on the iron particle 10 with a test load of 0.5N. The length of the diagonal line of the indentation 64 is measured, and the Vickers hardness HV is calculated.

  Further, when the specific surface area of the iron particles 10 is α and the apparent specific surface area of the iron particles 10 is β, the iron particles 10 satisfy the relationship of α / β ≧ 2.5. It is preferable that the iron particles 10 further satisfy the relationship of α / β ≧ 3.0. The specific surface area α and the apparent specific surface area β of the iron particles 10 can be determined by the method described below.

The specific surface area α of the iron particles 10 is measured by a gas adsorption method (BET method: a specific surface area measurement method using the BET formula derived by Brunauer, Emmett and Teller). That is, a gas having a known molecular size (for example, nitrogen gas or krypton gas) is adsorbed on the surface of the iron particle 10, and the specific surface area α (m ² / g) of the iron particle 10 is determined from the amount of the adsorbed gas. Ask for. According to this method, since the specific surface area is obtained based on the amount of gas adsorbed along the surface of the iron particles 10, the actual specific surface area α of the iron particles 10 can be measured.

  The apparent specific surface area β of the iron particles 10 is calculated using the average particle diameter D of the iron particles 10 measured by a laser scattering diffraction method. First, a sample of several tens of grams is taken out from an iron powder composed of a plurality of iron particles 10. The particle size distribution of the sample is measured using a laser scattering diffraction method, and the average particle diameter D (m) is obtained from the histogram of the obtained particle size distribution. The average particle diameter D referred to here is the particle diameter of particles in which the sum of masses from the smaller particle diameter reaches 50% of the total mass in the histogram, that is, 50% particle diameter D.

When the true density of the iron particles 10 is k (g),
Surface area per iron particle 10: 4 × π × (D / 2) ²
Volume per iron particle 10: 4/3 × π × (D / 2) ³
Apparent surface area β per gram of iron particles 10:
(4 × π × (D / 2) ² ) / (4/3 × π × (D / 2) ³ × k)
Thus, the apparent specific surface area β (m ² / g) of the iron particles 10 is calculated from the above equation.

  The specific surface area α thus measured is the actual specific surface area value of the iron particles 10 including the distortion of the contour and the irregular shape of the surface, and the apparent specific surface area β is the average particle diameter D of the iron particles 10. It is a specific surface area value when assuming a true sphere. For this reason, in this Embodiment, the iron particle 10 which satisfy | fills the relationship of (alpha) / (beta)> = 2.5, in other words, the iron particle 10 with larger distortion of a contour and uneven | corrugated shape of a surface is used.

  FIG. 3 is an enlarged schematic view showing a range surrounded by a two-dot chain line III in FIG. Referring to FIGS. 1 and 3, iron particles 10 satisfying the relationship of α / β ≧ 2.5 are formed in an irregular shape having a distorted outline. Furthermore, fine irregularities exist on the surface of the iron particles 10 and are formed with a large surface roughness.

  FIG. 4 is a schematic view showing the surface of a dust core produced using the soft magnetic material shown in FIG. Referring to FIG. 4, the dust core includes a plurality of composite magnetic particles 30 that are composed of iron particles 10 and an insulating coating 20 that surrounds the surface of iron particles 10. An organic substance 40 is interposed between the plurality of composite magnetic particles 30. Each of the plurality of composite magnetic particles 30 is joined by engagement of unevenness of the composite magnetic particle 30 or joined by an organic substance 40.

  Since the shape of the iron particle 10 having an irregular shape and a large surface roughness is transferred on the surface of the insulating coating 20, the composite magnetic particle 30 has an irregular shape and a large surface roughness, similar to the iron particle 10. Formed. For this reason, each of the plurality of composite magnetic particles 30 is intertwined in a complicated manner and joined in a state of meshing with each other, thereby improving the strength of the dust core.

  Next, a method for manufacturing the dust core shown in FIG. 4 using the soft magnetic material in the embodiment of the present invention will be described.

  FIG. 5 is a sectional view showing an atomizing apparatus for producing the soft magnetic material shown in FIG. Referring to FIG. 5, first, an iron ingot as a raw material for iron particles is put into a vacuum induction furnace 51, and a high frequency power source is introduced into the vacuum induction furnace 51. Thereby, the iron ingot in the vacuum induction furnace 51 is melted to form a molten metal 56. While blowing high pressure water 57 toward the injection nozzle 54, the molten metal 56 is supplied to the molten metal introducing pipe 53. When the high-pressure water 57 is sprayed, the molten metal 56 is sprayed and then rapidly cooled in the spray tower 52, thereby forming iron powder composed of a plurality of iron particles 10.

  At this time, the cooling rate in the spray tower 52 is set to be slow, or the ratio of elements (particularly nitrogen, carbon, phosphorus and manganese) that cause the hardness contained in the iron particles 10 to be improved is reduced. As a result, iron particles 10 having a Vickers hardness HV of less than 800 can be obtained. In addition, after the above-described atomizing step, heat treatment may be performed on the iron powder at a temperature condition of 500 ° C. or higher in hydrogen or an inert gas atmosphere. In this case, strain and stress existing in the iron particles 10 can be released, and the hardness of the iron particles 10 can be reduced.

  Moreover, the iron particle 10 can be formed in the shape with a rough surface and large surface roughness by setting conditions, such as a water ejection pressure and water temperature, appropriately at the time of the above-mentioned atomization process. Moreover, the uneven | corrugated shape formed in the surface of the iron particle 10 can be enlarged, so that the particle size of the iron particle 10 is enlarged. Further, compared with the gas atomization method, the water atomization method can increase the uneven shape formed on the surface of the iron particles 10.

  Next, the obtained iron powder is subjected to a phosphoric acid treatment to form an insulating coating 20 on the surface of the iron particles 10 to produce composite magnetic particles 30. The insulating coating 20 functions as an insulating layer between the iron particles 10. By covering the iron 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 particles 10, and can reduce the iron loss of the powder magnetic core resulting from an eddy current.

  Note that the insulating coating 20 may contain 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 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, as the organic material 40, a first organic material for strength development composed of a thermoplastic resin and a non-thermoplastic resin and a second organic material for lubrication composed of a higher fatty acid-based lubricant are prepared. Examples of the first organic substance include thermoplastic resins such as thermoplastic polyimide, thermoplastic polyamide, thermoplastic polyamideimide, polyphenylene sulfide, polyamideimide, polyethersulfone, polyetherimide or polyetheretherketone, and high molecular weight polyethylene. A non-thermoplastic resin such as wholly aromatic polyester or wholly aromatic polyimide can be used. High molecular weight polyethylene refers to polyethylene having a molecular weight of 100,000 or more. As the second organic substance, higher fatty acid systems such as zinc stearate, lithium stearate, calcium stearate, magnesium stearate, lithium palmitate, calcium palmitate, lithium oleate and calcium oleate can be used.

  The composite magnetic particle 30 and the organic substance 40 are mixed using a V-type mixer. At this time, the mixing ratio is adjusted so that the ratio of the first and second organic substances to the molded body produced in the subsequent step is 0.001% by mass or more and 0.2% by mass or less. In addition, as the organic substance 40, both the 1st and 2nd organic substance may be used, and either one may be used. There is no particular limitation on the mixing method, 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.

  Next, a pressure forming process is performed on the obtained mixed powder. 6 to 8 are cross-sectional views showing the steps of pressure forming when the dust core shown in FIG. 4 is manufactured. Referring to FIG. 6, first, the band heater 77 of the mold apparatus 71 is energized to heat the inner wall 73 of the die 72 to a temperature of 40 ° C. or higher. Further, instead of heating the inner wall 73, the mixed powder obtained in the previous step may be heated, or both may be heated. Furthermore, it is preferable to heat these to a temperature of 80 ° C. or higher and 200 ° C. or lower.

  Next, the lubricant supply part 78 is positioned above the space 74 surrounded by the inner wall 73. The mold lubricant 91 is sprayed from the spray nozzle of the lubricant supply unit 78 toward the space 74 using air. Thereby, the mold lubricant 91 is attached to the inner wall 73 and the bottom surface 76 of the mold apparatus 71. In the figure, the powder mold lubricant 91 is schematically shown. However, a liquid mold lubricant 91 may be used, and the method of adhering may be either wet or dry. . As the mold lubricant 91, for example, metal soap, polyethylene, amide wax, polyamide, polypropylene, acrylic ester polymer, methacrylic ester polymer, fluororesin, and layered lubricant can be used. Further, a material obtained by appropriately selecting and mixing two or more materials from these materials may be used.

  Referring to FIG. 7, shoe 79 is positioned above space 74, and mixed powder 15 obtained in the previous step is supplied from shoe 79 toward space 74. Referring to FIG. 8, 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.

  At the time of this pressure molding, the organic substance 40 functions as a lubricant between the adjacent composite magnetic particles 30 mainly by the action of the second organic substance contained therein. Thereby, distortion is introduced into the iron particles 10 during pressure molding, and the insulating coatings 20 are strongly rubbed against each other to be destroyed.

  Thereafter, the molded body 16 obtained by pressure molding is extracted from the space 74. Next, the molded body 16 is heat-treated at a temperature that exceeds the glass transition temperature of the organic substance 40 and is equal to or lower than the thermal decomposition temperature of the organic substance 40. Thereby, the organic matter 40 can be allowed to enter between the composite magnetic particles 30 while suppressing the organic matter 40 from being thermally decomposed. Thereby, the composite magnetic particles 30 are strongly bonded to each other mainly by the action of the first organic substance contained in the organic substance 40, and the strength of the molded body 16 can be improved. In addition, 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 shown in FIG. 1 is completed by subjecting the molded body 16 to appropriate processing such as extrusion and cutting.

  According to the manufacturing method of the soft magnetic material and the powder magnetic core configured as described above, since the iron particles 10 having a small Vickers hardness HV of less than 800 are used, the iron particles 10 are formed during pressure molding. Is easily plastically deformed. For this reason, the composite magnetic particles 30 are joined in a complicatedly entangled state, and the mutual binding force is increased. Thereby, the intensity | strength of the molded object 16 produced by pressure molding can be improved, for example, even when it cuts into the molded object 16, it can process without producing a defect | deletion etc.

  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, automotive solenoids, various magnetic sensors and various electromagnetic valves. Can do. In the present embodiment, the dust core is manufactured. However, the present invention is not limited to such a magnetic component, and it is possible to manufacture a general dust compact including a mechanical component.

  The production method of the soft magnetic material and the green compact according to the present invention was evaluated by the examples described below.

Example 1
A plurality of types of iron powders whose Vickers hardness HV was measured were prepared, and the specific surface area α and the apparent specific surface area β of the iron particles 10 constituting each iron powder were measured according to the method described in the embodiment. . At this time, for the measurement of Vickers hardness, a micro Vickers hardness tester was used and the test load was set to 0.5N. Moreover, krypton gas was used for the measurement of the specific surface area α by the gas adsorption method.

  Next, a composite magnetic particle 30 in which an iron phosphate coating as an insulating coating 20 is formed on the surface of the iron particles 10 by performing a wet coating method called bondage treatment on a part of the iron powder using an iron phosphate solution. Was made. At this time, the thickness of the insulating coating 20 was adjusted by changing the concentration of the solution.

Next, the obtained composite magnetic particles 30 and the iron powder not provided with the insulating coating 20 were pressure-molded at a pressure of 1275 MPa (= 13 ton / cm ² ), respectively, to form molded bodies of samples A to V. . At this time, the density of the compact was set to 7.5 g / cm ³ . The shape of the molded body was the same as that of a 20 mm span JIS test piece according to the JIS standard bending test. The molded body obtained by the above steps was subjected to a bending test in accordance with JIS standards, and the bending strength was measured. The measured bending strength values are shown in Table 1 together with the data of the iron particles 10 and the insulating coating 20 constituting the molded body of each sample.

  As can be seen with reference to Table 1, regardless of the presence or absence of the insulating coating 20, high bending strength could be obtained in the samples in which the Vickers hardness HV of the iron particles 10 was less than 800. Further, even when the value of the Vickers hardness HV was the same, a higher bending strength could be obtained with a sample in which the α / β value was 2.5 or more.

(Example 2)
A plurality of types of insulating coatings 20 were formed on the iron powder used in the molded body of Sample F of Example 1 while changing the thickness thereof, and composite magnetic particles 30 were produced. Next, JIS test piece-shaped compacts of Samples 1 to 20 were produced from the composite magnetic particles 30 by the same method as in Example 1. Separately, using the same composite magnetic particle 30, ring-shaped compacts of Samples 1 to 20 were also produced.

  For the JIS test piece shaped molded body, the bending test was carried out in the same manner as in Example 1 to determine the bending strength of each molded body. Further, a magnetic field having a maximum value of 1 T (Tesla) was applied to the ring-shaped molded body, and the eddy current loss coefficient at that time was measured. The values of the bending strength and eddy current loss coefficient obtained by the measurement are shown in Table 2 together with the data of the iron particles 10 and the insulating coating 20 constituting the molded body of each sample. The first, second, and third layers of the insulating coating shown in the table mean that the insulating coating 20 was formed with a one-layer structure, a two-layer structure, and a three-layer structure, respectively.

  Referring to Table 2, when the thickness of the insulating coating 20 was smaller than 5 nm, the effect of reducing the eddy current loss coefficient by providing the insulating coating 20 could not be sufficiently obtained. Moreover, when the thickness of the insulating coating 20 exceeded 100 nm, although the eddy current loss coefficient was reduced, the bending strength was slightly lowered. This is presumably because the thickness of the insulating coating 20 was too large and the uneven shape of the iron particles 10 was not transferred to the surface of the insulating coating 20 and the composite magnetic particles 30 were not sufficiently engaged with each other. In contrast, in the sample provided with the insulating coating 20 having a thickness of 5 nm to 100 nm, both excellent strength and a small eddy current loss coefficient could be achieved.

(Example 3)
A plurality of types of organic substances were mixed with the composite magnetic particles 30 used in the molded body of the sample Q of Example 1 while changing the addition amount. By the same method as in Example 1, JIS test piece-shaped molded bodies and ring-shaped molded bodies of Samples 1 to 26 were produced from the obtained mixed powder. Thereafter, the obtained molded body was subjected to heat treatment under a temperature condition equal to or higher than the glass transition temperature of the added organic matter.

  In the same manner as in Example 2, the bending strength was measured from the JIS test piece-shaped molded body, and the eddy current loss coefficient was measured from the ring-shaped molded body. The values of the bending strength and eddy current loss coefficient obtained by the measurement are shown in Table 3 together with the data of organic substances added to the molded body of each sample. The additive resin shown in the table corresponds to the first organic material for strength development described in the embodiment, and the lubricant shown in the table corresponds to the second organic material for lubrication described in the embodiment. Equivalent to.

  As can be seen with reference to Table 3, the bending strength was improved by mixing an appropriate amount of additive resin, and the eddy current loss coefficient was decreased by mixing an appropriate amount of lubricant. From this, it was confirmed that both high strength and excellent magnetic properties can be achieved by mixing the additive resin and the lubricant appropriately in combination.

  In addition, at the time of pressure molding, it is possible to further improve the strength of the molded body within a range of 10% or less by applying a lubricant to the inner wall of the mold. In addition, when the powder supplied to the inner wall of the mold or the mold is heated to a temperature of 80 ° C. or higher and 200 ° C. or lower, the strength of the molded body can be further improved within a range of 10% or less. Moreover, the intensity | strength of a molded object can further be improved by implementing combining these both.

  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 a schematic diagram which shows the soft-magnetic material in embodiment of this invention. It is explanatory drawing for demonstrating the measuring method of the Vickers hardness HV of the iron particle shown in FIG. It is a schematic diagram which expands and shows the range enclosed by the dashed-two dotted line III in FIG. It is a schematic diagram which shows the surface of the powder magnetic core produced using the soft-magnetic material shown in FIG. It is sectional drawing which shows the atomizing apparatus for manufacturing the soft-magnetic material shown in FIG. It is sectional drawing which shows the 1st process of the pressure molding at the time of manufacturing the powder magnetic core shown in FIG. It is sectional drawing which shows the 2nd process of the pressure molding at the time of manufacturing the powder magnetic core shown in FIG. It is sectional drawing which shows the 3rd process of the press molding at the time of manufacturing the powder magnetic core shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Iron particle, 16 Molded body, 20 Insulating film, 30 Composite magnetic particle, 40 Organic substance, 71 Mold apparatus, 73 Inner wall, 91 Mold lubricant.

Claims (6)

A method for producing a green compact using iron powder,
The iron powder is an aggregate of a plurality of iron particles having a Vickers hardness HV of less than 800. The specific surface area of the iron particles measured by the gas adsorption method (BET method) is α, and the laser powder diffraction method is used. When the apparent specific surface area of the iron particles calculated from the measured average particle diameter is β, the iron particles satisfy the relationship of α / β ≧ 2.5,
Introducing the plurality of iron particles into a mold;
A step of pressure forming the plurality of iron particles to form a molded body,
The step of introducing the plurality of iron particles into the mold includes a first organic material composed of at least one of a thermoplastic resin and a non-thermoplastic resin, and a ratio of the first organic material to the molded body is 0.001. The manufacturing method of a compacting body including the process added to these iron particles so that it may become mass% or more and 0.01 mass% or less.   The manufacturing method of the compacting body of Claim 1 with which the surface of the said iron particle is surrounded by the insulating film.   The manufacturing method of the compacting body of Claim 2 whose average thickness of the said insulating film is 5 nm or more and 100 nm or less. The step of introducing the plurality of iron particles into the mold includes a second organic material composed of a higher fatty acid-based lubricant, wherein the ratio of the second organic material to the molded body is 0.001% by mass or more and 0.2% by mass. The manufacturing method of the compacting body of any one of Claim 1 to 3 including the process added to these iron particles so that it may become the following.   The method for producing a green compact according to any one of claims 1 to 4, wherein the step of introducing the plurality of iron particles into a mold includes a step of applying a lubricant to an inner wall of the mold. The step of putting the plurality of iron particles into the mold includes a step of heating at least one of the inner wall of the mold and the plurality of iron particles to a temperature of 40 ° C or higher. The manufacturing method of the compacting body of Claim 1.

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