JP2005297046A - Powder molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a powder molding method where satisfactory lubricity can be obtained at the time of pressure molding, and further, a molding can be formed into a desired shape. <P>SOLUTION: The powder molding method is provided with a stage where a die lubricant is jetted, and is stuck to the inner wall of a die apparatus. The particle size distribution of the die lubricant has two or more peaks. The powder molding method is further provided with a stage where powder for molding is filled into the die apparatus with the die lubricant stuck thereto, and the powder for molding is subjected to pressure molding to form a molding. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates generally to a powder molding method, and more particularly to a powder molding method that utilizes a dry spray method when a lubricant is applied to the inner wall of a mold.

  Conventionally, when metal powder filled in a mold is pressed, the friction generated between the inner wall of the mold and the metal powder is reduced by using a lubricant to form a molded article with excellent quality. Various methods have been considered.

For example, Japanese Patent Laid-Open No. 2001-342478 discloses the production of a high-density iron-based powder molded body in which a mixed powder of two or more kinds of lubricants having a melting point higher than a predetermined pressure molding temperature is charged and adhered to the mold surface. A method is disclosed (Patent Document 1). Japanese Patent Application Laid-Open No. 11-140505 discloses a mold lubrication method in which a lubricant is applied to the surface of a mold (mold) and a mixed lubrication in which a powdery lubricant is added to and mixed with a raw material powder in a predetermined addition amount. Patent Document 2 discloses a powder molding method using a combination of the above and other methods.
JP 2001-342478 A JP-A-11-140505

  However, in the case of using a dry spray method in which the dried lubricant is ejected and adhered to the inner wall of the mold, it is difficult to uniformly adhere the lubricant to the inner wall of the mold. If there is a portion where the lubricant is not sufficiently adhered to the inner wall of the mold, there is a risk that seizure will occur at that portion. Conversely, if too much lubricant adheres to a part of the inner wall of the mold, the surface of the molded body formed in contact with that part may cause a poor appearance or the density of the molded body may decrease. is there.

  Therefore, even if the melting point and addition amount of the lubricant are appropriately controlled as disclosed in Patent Documents 1 and 2, if the lubricant is not uniformly attached to the inner wall of the mold, the desired state is obtained. A molded body cannot be obtained.

  Accordingly, an object of the present invention is to solve the above-mentioned problems, and to provide a powder molding method capable of obtaining good lubricity during pressure molding and forming a molded body in a desired state.

  Since the mold is formed with a certain depth, there is a difference in the adhesion state of the lubricant between a location near and a location where the powdery lubricant is ejected. Therefore, as a result of repeated investigations on the particle size of the lubricant by the inventors, the difference in the difference is obtained by carrying out the preparation and mixing of the lubricant so that the particle size distribution of the lubricant has two or more peaks. Has been found to be resolved.

  The powder molding method according to the present invention includes the steps of ejecting a powdery lubricant and attaching the powdery lubricant to the inner wall of the mold. The particle size distribution of the powdered lubricant has two or more peaks. The powder molding method further includes a step of forming a molded body by filling powder in a metal mold to which a powdery lubricant is attached and press-molding the powder.

  Here, the peak of the particle size distribution of the powdered lubricant is the particle size distribution when the particle size distribution of the powdered lubricant is represented on a graph with the horizontal axis representing the particle size and the vertical axis representing the frequency. This is a portion where the slope of the distribution function is located in a section where the slope changes from positive to negative, and the slope becomes zero in that section.

  According to the powder molding method configured as described above, since the particle size distribution of the powdery lubricant has a peak of 2 or more, the powdery lubricant is at least a group having a relatively small particle size, And a group having a large particle size. A group of powdered lubricants having a relatively small particle size adheres to a position relatively close to a point where the powdered lubricant is ejected, and a group of powdered lubricants having a relatively large particle size is , It adheres to a position relatively far from the point where the powdery lubricant is ejected.

  For this reason, according to this invention, a powdery lubricant can be made to adhere uniformly to the whole inner wall of a metal mold | die. Thereby, when the powder is pressure-molded, good lubricity can be obtained at any position on the inner wall of the mold. In addition, a part of the molded body is not formed containing a large amount of powdered lubricant. For this reason, the molded object which has a desired external appearance can be formed uniformly and with a large density.

  Further preferably, the particle size distribution of the powdery lubricant has one or more peaks on both sides of the average particle size of the powdery lubricant. According to the powder molding method thus configured, the powdery lubricant is at least a group having a particle size smaller than the average particle size of the powdery lubricant and larger than the average particle size of the powdery lubricant. And a group having a particle size. For this reason, the powdery lubricant can be uniformly adhered to the entire inner wall of the mold.

  Preferably, the average particle size of the powdery lubricant is 15 μm or more and 200 μm or less. According to the powder molding method thus configured, by setting the average particle size of the powder lubricant to 15 μm or more, a part of the powder lubricant is placed inside the mold when the powder lubricant is ejected. It can be prevented from splashing outside without entering. In addition, by setting the average particle size of the powder lubricant to 200 μm or less, the powder lubricant does not settle on the inner wall of the mold due to its own weight, and accumulates on the bottom surface of the mold positioned vertically downward. Can be prevented. For these reasons, the powdery lubricant can be uniformly attached to the entire inner wall of the mold.

  Preferably, the powdered lubricant is at least selected from the group consisting of metal soap, polyethylene, amide wax, polyamide, polypropylene, acrylate polymer, methacrylate polymer, fluorine resin, and layered lubricant. Including one kind. According to the powder molding method configured as described above, the powdery lubricant formed from these materials adheres to the inner wall of the mold, so that excellent lubricity can be obtained at the time of powder pressure molding. . For example, when a powdered lubricant is formed from an amide wax or polyamide, the amide group contained in the material improves the hardness of the powdered lubricant, and the fatty acid group functions as a lubricant. Examples of the metal soap include zinc stearate, lithium stearate, calcium stearate, aluminum stearate, lithium palmitate, calcium palmitate, lithium oleate or calcium oleate.

  Further preferably, the step of attaching the powdered lubricant includes the step of attaching the powdered lubricant to the inner wall of the mold so that the ratio of the powdered lubricant to the molded body is 0.001% by mass or more and 0.5% by mass or less. A step of attaching to the substrate.

  According to the powder molding method configured as described above, the desired lubricity by the powder lubricant can be obtained by setting the ratio of the powder lubricant to 0.001% by mass or more. Thereby, it can prevent that a molded object becomes the external appearance defect by image sticking, the scratch formed on the surface, etc. In addition, when the ratio of the powdery lubricant is 0.5% by mass or less, the compact is formed by entraining a large amount of the powdery lubricant, or the powdery lubricant is collected on the bottom surface of the mold. Can be prevented. Thereby, while finishing a molded object with a favorable external appearance, it can avoid that the density of a molded object falls.

  Preferably, the powder molding method further includes a step of adding a lubricant to the powder before the step of forming the molded body. According to the powder molding method thus configured, in addition to lubricity to the mold, excellent lubricity between powders can be obtained during pressure molding, and the flowability of the powder can be improved. Thereby, the density of the obtained molded body can be increased and the density can be made uniform.

  Preferably, the lubricant is at least one selected from the group consisting of metal soap, polyethylene, amide wax, polyamide, polypropylene, acrylate polymer, methacrylate polymer, fluororesin, and layered lubricant. Including. According to the powder molding method configured as described above, the lubricant formed from these materials exhibits particularly excellent lubricity, and thus the above-described effects can be effectively obtained.

  Preferably, the powder is a plurality of composite magnetic particles including metal magnetic particles and an insulating coating surrounding the surface of the metal magnetic particles. According to the powder molding method thus configured, a powder magnetic core is produced by pressure molding a plurality of composite magnetic particles. At this time, since good lubricity is obtained with the mold during pressure molding, the insulating coating can be prevented from being broken. Further, the insulating coating itself has a large slip property. For this reason, while improving the lubricity at the time of pressure molding, it can prevent that a big distortion is introduce | transduced into the inside of a metal magnetic particle at the time of pressure molding. Thereby, excellent magnetic characteristics with reduced eddy current loss and hysteresis loss can be obtained.

  Preferably, the average thickness of the insulating coating is 5 nm or more and 100 nm or less. According to the powder molding method configured as described above, the average thickness of the insulating coating is set to 5 nm or more, thereby suppressing the tunnel current flowing in the coating and suppressing the increase in eddy current loss due to the tunnel current. Can do. Moreover, when the average thickness of the insulating coating is 100 nm or less, the distance between the metal magnetic particles does not become too large. Thereby, it can prevent that a demagnetizing field generate | occur | produces between metal magnetic particles, and can suppress the increase in the hysteresis loss resulting from generation | occurrence | production of a demagnetizing field. Moreover, it can suppress that the magnetic flux density of a dust core falls by suppressing the volume ratio of the nonmagnetic layer which occupies for the whole.

  As described above, according to the present invention, it is possible to provide a powder molding method capable of obtaining good lubricity during pressure molding and forming a molded body in a desired state.

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

  FIG. 1 is a schematic view showing a cross section of a dust core produced by using the powder molding method according to the embodiment of the present invention. Referring to FIG. 1, the powder magnetic core includes a plurality of composite magnetic particles 33 composed of metal magnetic particles 31 and an insulating coating 32 surrounding the surface of metal magnetic particles 31. Each of the plurality of composite magnetic particles 33 is joined by meshing the unevenness of the composite magnetic particles 33.

  FIG. 2 is a cross-sectional view showing a mold apparatus used in the powder molding method in the present embodiment. Referring to FIG. 2, a mold apparatus 1 is opened in a cylindrical shape, and is disposed so as to close a die 2 having an inner wall 3 and a lower portion of an opening portion of the die 2, and has a bottom surface 6 continuous with the inner wall 3. The punch 5 includes a lubricant supply unit 8, a shoe 9 and an upper punch 10 disposed above the die 2. The die 2 incorporates a band heater 7 for heating the die 2 to a predetermined temperature. The inner wall 3 of the die 2 defines a space 4 filled with molding powder together with the bottom surface 6 of the lower punch 5. The inner wall 3 extends vertically upward from the periphery of the bottom surface 6, and the open end of the die 2 is located at the extending tip.

  The lubricant supply unit 8 and the shoe 9 are provided so as to be slidable above the opening end of the die 2, and each device is positioned at an appropriate position in accordance with the pressure molding process. Note that a core rod extending vertically upward from the center of the bottom surface 6 may be provided in the space 4.

  Next, a process for producing the dust core in FIG. 1 by the powder molding method in the present embodiment will be described.

  Referring to FIG. 2, the band heater 7 is energized to heat the die 2 to a predetermined temperature. At this time, the heating temperature of the die 2 is appropriately set depending on the type of the mold lubricant used in the subsequent process, and is preferably set to a temperature slightly lower than the melting point of the mold lubricant. Note that the heating temperature by the band heater 7 is a temperature at which operation is possible depending on the shape of the die 2. Next, the lubricant supply unit 8 is positioned above the space 4. The charged mold lubricant 21 is sprayed from the spray nozzle of the lubricant supply unit 8 toward the inner wall 3 using air. At this time, the mold lubricant 21 adheres to the inner wall 3 due to a charging adhesion effect. In addition, the metal mold | die lubricant 21 in a figure is represented typically.

  When the die 2 is heated to a temperature slightly lower than the melting point of the mold lubricant 21, the mold lubricant 21 is slightly softened and tends to adhere to the inner wall 3. For this reason, a good adhesion state is obtained by a synergistic effect with the charging adhesion effect. Further, since the mold lubricant 21 does not change to a liquid state, the mold lubricant 21 can be prevented from collecting on the bottom surface 6.

FIG. 3 is a graph showing the particle size distribution of the mold lubricant used in the powder molding method in the present embodiment. In the figure, the particle size distribution of the mold lubricant measured by the laser scattering diffraction method is the particle size on the horizontal axis and the frequency (%) on the vertical axis (the mold lubricant having the particle size occupies the whole. The abundance ratio) is shown on the graph. Referring to FIG. 3, the particle size distribution of the mold lubricant 21 is such that the peak portion 41 has a peak value at the particle size D _P1 and the peak value at the particle size D _P2 larger than the particle size D _P1. And a peak portion 42. A bottom 43 exists between the peak 41 and the peak 42. In addition, the particle size (D _P1 , D _P2 ) corresponding to the above-described peak portion is hereinafter also referred to as a peak particle size.

At the peak portions 41 and 42 and the bottom portion 43, the gradient of the particle size distribution function is zero. More particularly, the particle size of the mold lubricant 21 is, when increasing toward the particle size D _P1, the slope of the function of the particle size distribution is positive, it becomes zero at the peak portion 41. The slope of the function representing the particle size distribution is negative between the peak portion 41 and the bottom portion 43 and becomes zero at the bottom portion 43 and then becomes positive between the bottom portion 43 and the peak portion 42. At the peak portion 42, the gradient of the function of the particle size distribution is 0, and the gradient is negative while the particle size of the mold lubricant 21 is further increased from the particle size _DP2 .

The average particle diameter α of the mold lubricant 21 is preferably larger than the particle diameter D _{P1 and} smaller than the particle diameter D _P2 . In other words, it is preferable that the peak portions 41 and 42 are respectively located on both sides of the average particle diameter α of the mold lubricant 21. In addition, the average particle diameter here means the particle diameter of a particle in which the sum of masses from the smaller particle diameter reaches 50% of the total mass in the particle diameter histogram, that is, 50% particle diameter D.

  When the mold lubricant 21 having such a particle size distribution is used, the mold lubricant 21 constituting the peak portion 41 has a relatively small particle size, and therefore, from the injection nozzle of the lubricant supply unit 8. Is attached to the inner wall 3 around a position where the distance is relatively small, that is, a position near the opening end of the die 2. On the other hand, since the mold lubricant 21 constituting the peak part 42 has a relatively large particle size, the position where the distance from the injection nozzle of the lubricant supply part 8 is relatively large, that is, the position close to the bottom surface 6. It adheres to the inner wall 3 around the center. For this reason, the mold lubricant 21 can be uniformly attached over the entire inner wall 3.

FIG. 4 is a graph showing another particle size distribution of the mold lubricant used in the powder molding method in the present embodiment. Referring to FIG. 4, the particle size distribution of the mold lubricant 21, in addition to the peak portion 41 and 42, further, the peak portion 45 the frequency with a large particle diameter D _P3 than the particle size D _P2 reaches a peak value You may have. In this case, a bottom portion 44 exists between the peak portion 42 and the peak portion 45. That is, the particle size distribution of the mold lubricant 21 only needs to have two or more peaks.

  As the mold lubricant 21, 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.

  The average particle diameter of the mold lubricant 21 is preferably 15 μm or more and 200 μm or less. By making the average particle size 15 μm or more, it is possible to prevent the mold lubricant 21 from being scattered outside the space 4. By setting the average particle size to 200 μm or less, the mold lubricant 21 adhering to the inner wall 3 does not accumulate on the bottom surface 6 due to its own weight. The average particle size referred to here also refers to the 50% particle size D described above.

  5 and 6 are cross-sectional views showing the steps of the powder molding method in the present embodiment. Referring to FIGS. 1 and 5, first, an insulating coating 32 is formed so as to cover the metal magnetic particles 31, and a molding powder 22 composed of a plurality of composite magnetic particles 33 is prepared.

  At this time, examples of the metal magnetic particles 31 include 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, iron (Fe) -aluminum (Al) -silicon (Si) alloy, and the like can be used. The metal magnetic particles 31 may be a single metal or an alloy.

  The insulating coating 32 is formed by subjecting the metal magnetic particles 31 to phosphoric acid treatment. Preferably, the insulating coating 32 contains an oxide. As the insulating coating 32 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 32 may be formed in one layer as shown in FIG. 1, or may be formed in multiple layers.

  The insulating coating 32 functions as an insulating layer between the metal magnetic particles 31. By covering the metal magnetic particles 31 with the insulating coating 32, 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 31, and can reduce the iron loss resulting from an eddy current.

  The average thickness of the insulating coating 32 is preferably 5 nm or more and 100 nm or less. The average thickness referred to 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.

  The molding powder 22 is mixed with a powder molding lubricant made of metal soap, polyethylene, amide wax, polyamide, polypropylene, acrylic acid ester polymer, methacrylic acid ester polymer, fluororesin or layered lubricant. May be. The powder molding lubricant functions as a lubricant between the composite magnetic particles 33 during pressure molding, and also plays a certain role as a lubricant for the inner wall 3. Due to the action of such a powder molding lubricant, it is possible to prevent the insulating coating 32 from being destroyed during pressure molding, and to suppress the introduction of large strains into the metal magnetic particles 31.

  Next, the devices arranged side by side above the die 2 are slid in the direction indicated by the arrow 11 to position the shoe 9 loaded with the molding powder 22 above the space 4. The molding powder 22 is supplied from the shoe 9 to the space 4. At this time, the molding powder 22 may be supplied to the mold apparatus 1 as it is at room temperature, or may be supplied to the mold apparatus 1 after being heated according to the processing by the mold apparatus 1. .

  Referring to FIG. 6, the devices arranged side by side above die 2 are slid in the direction indicated by arrow 12 and retracted from above space 4. Next, the molding powder 22 filled in the space 4 is pressure-molded by moving the upper punch 10 downward. Thereby, the molded object 23 is formed. Thereafter, the molded body 23 is extracted from the space 4.

  In the present embodiment, since the mold lubricant 21 is uniformly attached to the entire inner wall 3, seizure is performed in both the step of pressure-forming the molding powder 22 and the step of extracting the molded body 23. Will not occur.

  The proportion of the lubricant contained in the molded body 23 extracted from the space 4 is preferably 0.001% by mass or more and 0.5% by mass or less. More preferably, the ratio of the lubricant is 0.01% by mass or more and 0.4% by mass or less. The lubricant here refers to a mold lubricant 21 mixed in the molding powder 22 from the inner wall 3 and the bottom surface 6, and does not include the powder molding lubricant originally mixed in the molding powder 22.

  Thereafter, the obtained molded body 23 is subjected to appropriate processing such as extrusion and cutting to complete the dust core shown in FIG.

  The powder molding method according to the present invention includes a step of ejecting a mold lubricant 21 as a powdery lubricant and attaching the mold lubricant 21 to the inner wall 3 of the mold apparatus 1 as a mold. The particle size distribution of the mold lubricant 21 has two or more peaks. The powder molding method further includes the step of filling the mold apparatus 1 to which the mold lubricant 21 is attached with the molding powder 22 as a powder and forming the molded body 23 by press molding the molding powder 22. Prepare.

  According to the powder molding method configured in this way, no seizure occurs through the pressure molding process, so that the molded body 23 can be formed without scratching the surface. Further, since the mold lubricant 21 does not collect on the bottom surface 6 or the amount of the mold lubricant 21 adhering to the inner wall 3 does not partially increase, the mold lubricant 21 is formed on the surface of the molded body 23. A large amount is not taken in. For this reason, it can prevent that the surface roughness of the molded object 23 falls. Moreover, it can prevent that the density of the molded object 23 falls partially or the density of the molded object 23 becomes non-uniform | heterogenous. Moreover, since the dust core produced from such a molded body 23 contains the metal magnetic particles 31 uniformly and densely, the magnetic flux density is large and desired magnetic characteristics without variations can be obtained.

  In the present embodiment, the case of manufacturing a dust core has been described. However, the present invention is not limited to the manufacture of such a magnetic component. For example, pure iron powder, mixed powder in which an appropriate metal powder is mixed with iron powder, or an alloy powder such as an aluminum alloy is used as the molding powder 22, and the molding powder 22 is press-molded to obtain a machine structural component. In the case of manufacturing, the present invention can be applied.

  The effects of the powder molding method of the present invention were confirmed by the examples described below.

(Example 1)
First, according to the powder molding method described in the embodiment, a predetermined amount of the mold lubricant 21 was sprayed into the mold apparatus 1 and the space 4 was filled with the molding powder 22.

  At this time, as the mold lubricant 21, three types of zinc stearate powder having a single particle size distribution (sample A: peak particle size 25 μm (average particle size 30 μm), sample B: peak particle size 138 μm ( (Average particle size 150 μm), sample C: peak particle size 415 μm (average particle size 400 μm)), and these zinc stearate powders are mixed in an appropriate ratio and combination. A zinc stearate powder having a peak (samples 1 to 9) was used. Further, when the mold lubricant of Sample 5 was used, the spray amount was changed and adhered to the inner wall 3 of the mold apparatus 1. The heating temperature of the die 2 was set to 135 ° C.

  As a molding powder 22, zinc stearate as a powder molding lubricant is added in a proportion of 0.2% by mass to iron powder (trade name “ASC100.30”) manufactured by Höganäs, and a V-type mixer is used. And mixed for 2 hours.

Next, the pressurizing pressure was set to 588 MPa (6 ton / cm ² ) to produce a molded body having a cylindrical shape (diameter 40 mm × height 60 mm). After pressure molding, the extraction force when the molded body was extracted from the space 4 of the mold apparatus 1 was measured, and the extraction pressure was obtained from the measurement result. Moreover, the external appearance of the obtained molded object and the bottom face 6 of the metal mold apparatus 1 were observed, and the density of the obtained molded object was determined by the Archimedes method. Further, the ratio of the mold lubricant 21 contained in the molded body was determined from the mass of the molding powder 22 supplied to the space 4 and the mass of the obtained molded body. The results of the above observation and measurement are shown in Table 1 together with the type of mold lubricant 21 used.

  In Tables 1 to 3 that follow, the case where there is a burn-in trace on the appearance of the molded body is “x”, the case where no burn-in trace is observed is “◯”, and the state in between is “Δ”, This is shown in the column of “Appearance of molded product” in the table. In addition, the case where the mold lubricant 21 is accumulated on the bottom surface 6 of the mold apparatus 1 is “X”, the case where the mold lubricant 21 is not recognized at all is “◯”, and the state therebetween is “△”. "In the column of" Presence / absence of mold lubricant on the bottom surface "in the table.

  As can be seen with reference to Table 1, by using the mold lubricant 21 having a particle size distribution having a peak of 2 or more, it was possible to reduce the extraction pressure and obtain a good appearance with no burn-in marks. . Such an effect could be effectively obtained when the ratio of the mold lubricant 21 was 0.0001% by mass or more. Further, by using the mold lubricant 21 having a peak with a particle size distribution of 2 or more, it was possible to obtain a higher density than when the mold lubricants of Samples A to C were used. Further, when the ratio of the mold lubricant 21 was 0.5% by mass or less, the mold lubricant 21 was not recognized on the bottom surface 6 of the mold apparatus 1.

(Example 2)
In the same manner as in Example 1, the mold lubricant 21 was sprayed into the mold apparatus 1 and the space 4 was filled with the molding powder 22. In this embodiment, as the molding powder 22, zinc stearate as a powder molding lubricant is added in a proportion of 0.2% by mass to the phosphate-coated iron powder (trade name “Somaloy 500”) manufactured by Höganäs. And what was mixed for 2 hours using the V-type mixer was used. As the mold lubricant 21, the zinc stearate powders of samples A to C used in Example 1 and the zinc stearate powders of samples 1 to 9 were used.

Next, a molded body having a cylindrical shape (outer diameter 40 mm × inner diameter 20 mm × height 60 mm) was produced at a pressure of 883 MPa (9 ton / cm ² ). After the pressure molding, the same observation and measurement as in Example 1 were performed on the obtained molded body. The results are shown in Table 2 together with the type of mold lubricant 21 used.

  As can be seen with reference to Table 2, the same results as in Example 1 could be obtained even when phosphate-coated iron powder was used as the molding powder 22. Since the present invention is basically a technique for reducing the friction between the molding powder 22 and the inner wall 3 of the mold apparatus 1, the effects of the present invention can be obtained regardless of the type of the molding powder 22. it can. Therefore, the same effect can be obtained when metal powder such as iron, nickel or copper, mixed powder thereof, or metal powder composed of these intermetallic compounds is used as the molding powder 22.

(Example 3)
In the same manner as in Example 1, the mold lubricant 21 was sprayed into the mold apparatus 1 and the space 4 was filled with the molding powder 22. In this example, the zinc stearate powder of Sample 5 used in Example 1 was used as the mold lubricant 21. The heating temperature of the die 2 was set to 135 ° C.

  In order to produce the molding powder 22 used in this example, first, iron powder (trade name “ASC100.30”) manufactured by Höganäs was subjected to coating treatment with an iron phosphate solution, and then dried. The process was carried out. At this time, by changing the concentration of the iron phosphate solution, a plurality of types of iron powders having insulating coatings with different thicknesses were prepared. To the iron powder provided with the insulating coating, zinc stearate as a powder molding lubricant is added at a ratio of 0.05% by mass and mixed for 2 hours using a V-type mixer, thereby forming powder 22 for molding. Was made.

Next, a pressure molding process was performed to produce a molded body having a cylindrical shape (outer diameter 40 mm × inner diameter 20 mm × height 60 mm). The density of the molded body was 7.5 g / cm ³ . After pressure molding, the appearance of the obtained molded body and the bottom surface 6 of the mold apparatus 1 were observed in the same manner as in Example 1. Further, in this example, a magnetic field of 100 (Oe: Oersted) was applied to the compact, and the magnetic flux density B100 at that time was measured. Further, a magnetic field having a maximum value of 1T (Tesla) was applied to the compact, and the eddy current loss coefficient at that time was measured. The results of the above observation and measurement are shown in Table 3 together with the type of mold lubricant 21 used.

  As can be seen with reference to Table 3, when the average thickness of the insulating coating was 5 nm or more, a relatively small eddy current loss coefficient could be obtained. Moreover, when the average thickness of the insulating coating was 100 nm or less, a relatively large magnetic flux density could be obtained. From this, it has been confirmed that by appropriately controlling the average thickness of the insulating coating, it is possible to further improve the magnetic characteristics in combination with the effect of the high density of the present invention.

  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 cross section of the powder magnetic core produced using the powder shaping | molding method in embodiment of this invention. It is sectional drawing which shows the metal mold | die apparatus used for the powder shaping | molding method in this Embodiment. It is a graph which shows the particle size distribution of the metal mold | die lubricant used with the powder molding method in this Embodiment. It is a graph which shows another particle size distribution of the metal mold | die lubricant used with the powder shaping | molding method in this Embodiment. It is sectional drawing which shows the process of the powder shaping | molding method in this Embodiment. It is sectional drawing which shows another process of the powder shaping | molding method in this Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Mold apparatus, 3 Inner wall, 21 Mold lubricant, 22 Molding powder, 23 Molded object, 31 Metal magnetic particle, 32 Insulating film.

Claims (9)

A step of ejecting a powdered lubricant and attaching the powdered lubricant to an inner wall of a mold,
The particle size distribution of the powdered lubricant has two or more peaks, and
A powder molding method comprising a step of forming a molded body by filling a powder to which the powdery lubricant is attached and filling the powder and press-molding the powder.   The powder molding method according to claim 1, wherein the particle size distribution of the powdered lubricant has one or more peaks on both sides of the average particle size of the powdered lubricant.   The powder molding method according to claim 1 or 2, wherein an average particle diameter of the powdery lubricant is 15 µm or more and 200 µm or less.   The powdery lubricant includes at least one selected from the group consisting of metal soap, polyethylene, amide wax, polyamide, polypropylene, acrylate polymer, methacrylate polymer, fluorine resin, and layered lubricant. The powder molding method according to any one of claims 1 to 3.   The step of adhering the powdery lubricant includes the step of attaching the powdery lubricant to the inner wall of the mold so that the ratio of the powdery lubricant to the molded body is 0.001% by mass or more and 0.5% by mass or less. The powder shaping | molding method of any one of Claim 1 to 4 including the process made to adhere to.   The powder molding method according to claim 1, further comprising a step of adding a lubricant to the powder before the step of forming the molded body.   The lubricant includes at least one selected from the group consisting of metal soap, polyethylene, amide wax, polyamide, polypropylene, acrylic ester polymer, methacrylic ester polymer, fluororesin, and layered lubricant. Item 7. The powder molding method according to Item 6.   The powder molding method according to any one of claims 1 to 7, wherein the powder is a plurality of composite magnetic particles including metal magnetic particles and an insulating coating surrounding a surface of the metal magnetic particles.   The powder molding method according to claim 8, wherein an average thickness of the insulating coating is 5 nm or more and 100 nm or less.

Images