JP5129519B2 - Powder for compacting and method for producing powder for compacting - Google Patents

Description

  The present invention relates to a powder for compacting and a method for producing a powder for compacting. For example, the compact has a good fluidity, can be filled with a high density, and can be formed into a compact with high density. The present invention relates to a powder forming powder and a method for producing a powder for compacting.

  Conventionally, when obtaining a molded body of a predetermined shape by compacting iron-based powder in a mold, friction occurs between the interface between the mold wall surface and the iron-based powder or between the iron-based particles. Lubricant is applied. However, when the mold has a complicated shape, there is a problem that a portion where the lubricant is not applied is generated on the mold wall surface, and seizure occurs between the mold wall surface and the molded body.

  Further, it is possible to mix the lubricant powder with the iron-based powder and fill the mold. In this case, it is difficult to uniformly disperse the lubricant in the iron-based powder, and there is a problem that the fluidity of the iron-based powder becomes worse when the iron-based powder is filled in the mold.

  In order to uniformly disperse the lubricant in the iron-based powder, for example, the iron-based powder and the lubricant are mixed at a temperature equal to or higher than the melting point of the lubricant, and the lubricant is adhered to the iron-based powder particles. It can also be compacted with. However, in this case, the iron-based powder particles are easily bonded (aggregated) via a lubricant to form secondary particles, and the fluidity of the iron-based powder is improved, but the packing density is poor. .

Further, JP 2001-192706 A (Patent Document 1) describes a fluidity improving powder for powder metallurgy, which has good fluidity and good workability when supplying and filling powder into a mold. A manufacturing method is disclosed. Patent Document 1 discloses a method using a powder in which metal powder and a lubricant are mixed at a temperature not lower than 50 ° C. and not higher than 5 ° C. below the melting point of the lubricant.
JP 2001-192706 A

  However, in Patent Document 1, the lubricant may be softened by heating and become sticky. In this case, as in the conventional method described above, secondary particles are formed in the metal powder. There's a problem. Moreover, if the adhesiveness does not appear, there is a problem that seizure occurs between the mold and the molded body as in the case of simple mixing without a lubricant.

  Therefore, the present invention has been made to solve the above-described problems, and the object of the present invention is to have good fluidity, can be filled with high density, and high when compacted. The object is to provide a powder for compacting that becomes a dense compact and a method for producing the powder for compacting.

The powder for compacting in one aspect of the present invention includes iron-base particles and a lubricant that adheres to the surface of the iron-base particles. When the particle size of the iron-based particles exceeds 38 μm, the surface area S [m ² ], the volume V [m ³ ], the BET specific surface area B [m ² / g], and the true density ρ [g / m ³ ] F = (B × V × ρ) / S, and the average value of F is 2 or more and 20 or less. In the lubricant, the average value of the ratio of the lubricant present outside the convex hull of the iron-based particles to which the lubricant is attached is 18% or less.

The manufacturing method of the powder for compacting in one aspect of the present invention includes a preparation process and an adhesion process. In the preparation step, when the surface area S [m ² ], the volume V [m ³ ], the BET specific surface area B [m ² / g], and the true density ρ [g / m ³ ] are set, F = (B × V × Prepare iron-based particles having an average value of F represented by ρ) / S of 2 or more and 20 or less and a particle size of more than 38 μm. In the attaching step, a lubricant is attached to the surface of the iron-based particles. In the attaching step, the lubricant is applied to the surface of the iron-based particles so that the average value of the ratio of the lubricant existing outside the convex hull of the iron-based particles to which the lubricant is attached is 18% or less. To attach.

According to the powder for compacting and the method for producing powder for compacting in one aspect of the present invention, irregularities can be provided on the surface of the iron-based particles by setting the average value of F to 2 or more. By setting F to 20 or less, filling becomes possible at high density. In addition, since the lubricant is attached to the surface of the iron-based particles having a particle diameter exceeding 38 μm, the lubricant is attached to the recesses of the iron-based particles, and the smallest convex figure surrounding the outer periphery of the iron-based particles. It can suppress that a lubricant protrudes and adheres to the exterior of a certain convex hull. Therefore, it is possible to prevent the particles from aggregating with each other, and thus does not hinder the fluidity of the powder for compacting. Therefore, it can be made into a powder for compacting which has good fluidity, can be filled with high density, and becomes a compact with high density when compacted. In addition, the lubricant present outside the convex hull of the iron-based particles can be greatly reduced. Therefore, it is possible to prevent the particles from aggregating with each other, thereby improving the fluidity. Therefore, it can be made into a powder for compacting which has good fluidity, can be filled with high density, and becomes a compact with high density when compacted.

  In the method for producing a powder for compacting according to the above aspect, preferably, in the preparation step, the powder is classified into iron-based particles having a particle size of more than 38 μm and other iron-based particles having a particle size of 38 μm or less. Prepare iron-based particles. Thereby, in a preparation process, the iron-base particle | grains exceeding 38 micrometers can be prepared easily.

  Preferably, the powder for compacting in the above aspect further includes another iron-based particle having a particle size of 38 μm or less and having no lubricant attached to the surface.

  Preferably, in the method for producing a powder for compacting in the above aspect, the method further includes a mixing step of mixing another iron-based particle having a particle size of 38 μm or less with the iron-based particle to which a lubricant is attached. Yes.

  By providing another iron-based particle having a particle size of 38 μm or less, when the prepared iron-based particle includes an iron-based particle having a particle size of 38 μm or less, more iron-based particles can be used. This is advantageous in terms of cost. In addition, since the lubricant is not adhered to the surface of the other iron-based particles even if the particle size is 38 μm or less, aggregation due to the other iron-based particles can be prevented. Furthermore, since the other iron-based particles having a particle size of 38 μm or less have a relatively smaller particle size than the iron-based particles having a lubricant attached to the surface, they can be filled at a higher density.

The powder for compacting in another aspect of the present invention includes iron-based particles and a lubricant that adheres to the surface of the iron-based particles. When the particle size of the iron-based particles exceeds 75 μm, the surface area S [m ² ], the volume V [m ³ ], the BET specific surface area B [m ² / g], and the true density ρ [g / m ³ ] F = (B × V × ρ) / S, and the average value of F is 2 or more and 20 or less. In the lubricant, the average value of the ratio of the lubricant present outside the convex hull of the iron-based particles to which the lubricant is attached is 18% or less.

The method for producing a powder for compacting according to another aspect of the present invention includes a preparation step and an adhesion step. In the preparation step, when the surface area S [m ² ], the volume V [m ³ ], the BET specific surface area B [m ² / g], and the true density ρ [g / m ³ ] are set, F = (B × V × Prepare an iron-based particle having an average value of F represented by ρ) / S of 2 or more and 20 or less and a particle size exceeding 75 μm. In the attaching step, a lubricant is attached to the surface of the iron-based particles. In the adhering step, the lubricant on the surface of the iron base particles is set so that the average value of the ratio of the lubricant existing outside the convex hull of the iron base particles to which the lubricant is attached is 18% or less. To attach.

According to the powder forming powder and the powder forming method in another aspect of the present invention, the surface of the iron base particles can be provided with irregularities by setting the average value of F to 2 or more. By setting F to 20 or less, filling becomes possible at high density. In addition, since the lubricant is attached to the surface of the iron-based particles having a particle size exceeding 75 μm, the lubricant is attached to the recesses of the iron-based particles, and the smallest convex figure surrounding the outer periphery of the iron-based particles. It can suppress more that a lubricant protrudes and adheres to the exterior of a certain convex hull. Therefore, since it can prevent that particle | grains aggregate, it does not disturb the fluidity | liquidity of the powder for compacting. Therefore, it can be made into a powder for compacting that has better fluidity, can be filled at a high density, and becomes a high density molded body when compacted. In addition, the lubricant present outside the convex hull of the iron-based particles can be greatly reduced. Therefore, it is possible to prevent the particles from aggregating with each other, thereby improving the fluidity. Therefore, it can be made into a powder for compacting which has good fluidity, can be filled with high density, and becomes a compact with high density when compacted.

  Preferably, in the method for producing a powder for compacting in the above-mentioned other aspect, in the preparation step, by classifying into iron-based particles having a particle size of more than 75 μm and other iron-based particles having a particle size of 75 μm or less, Prepare iron-based particles. Thereby, in a preparatory process, the iron-base particle | grain exceeding 75 micrometers can be prepared easily.

  Preferably, the powder for compacting in the other aspect described above further includes another iron-based particle having a particle size of 75 μm or less and having no lubricant attached to the surface.

  Preferably, the method for producing a powder for compacting in the other aspect further includes a mixing step of mixing with another iron-based particle having a particle size of 75 μm or less and an iron-based particle to which a lubricant is attached.

  By further providing other iron-based particles having a particle size of 75 μm or less, when the prepared iron-based particles include iron-based particles having a particle size of 75 μm or less, more iron-based particles to be prepared can be used. This is advantageous in terms of cost. In addition, since the lubricant is not adhered to the surface of the other iron-based particles even when the particle size is 75 μm or less, aggregation due to the other iron-based particles can be prevented. Furthermore, since another iron-based particle having a particle size of 75 μm or less has a relatively smaller particle size than the iron-based particle having a lubricant attached to the surface, it can be filled with high density.

  Preferably, in the powder for compacting in the one aspect and the other aspect, the lubricant is contained in an amount of 0.05% by mass or more and 0.40% by mass or less with respect to the iron-based particles to which the lubricant is attached.

In the method for producing a powder for compacting in one aspect and the other aspect described above, preferably, in the adhesion step, 0.05 mass% or more and 0.40 mass% or less with respect to the iron-based particles to which the lubricant is adhered. Apply lubricant to be included.

  By setting the content to 0.05% by weight or more, the lubricating performance effect of the lubricant can be further expressed. By setting the content to 0.4% by weight or less, the amount of the lubricant remaining after compacting does not increase, and the densification of the compacted compact can be realized.

  In this specification, the particle size of the iron-based powder is a particle size exceeding the nominal size of the sieve that does not pass through the sieve specified in JIS Z 8801-1, and passes through the sieve. The particle size is smaller than the nominal size of the sieve. For example, iron-based particles that do not pass through a sieve having a nominal size of 38 μm have a particle size exceeding 38 μm, and other iron-based particles that pass through a sieve having a nominal size of 38 μm have a particle size of 38 μm or less. Further, the iron base particles that do not pass through the sieve having a nominal size of 75 μm have a particle diameter exceeding 75 μm, and the other iron base particles that pass through the sieve having a nominal size of 75 μm have a particle diameter of 75 μm or less.

  Further, in this specification, “convex hull” means the smallest convex figure surrounding the outer periphery of any iron-based particle. Moreover, the average value of the F and the average value of the ratio are average values of particles of 500 or more powders for compacting that are arbitrarily selected.

  According to the compacting powder and the method for producing the compacting powder of the present invention, since the lubricant is adhered to the surface of the iron-based particles having a particle size exceeding a predetermined size, good fluidity is obtained. It has a high density and can be filled with high density.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

FIG. 1 is a diagram schematically showing a powder for compacting in an embodiment of the present invention. FIG. 2 is an enlarged view schematically showing one particle (compact molding particle) constituting the compacting powder in the embodiment of the present invention. As shown in FIG. 1 and FIG. 2, the powder for compacting in the present embodiment includes an iron-based particle 11 having a lubricant 20 attached to the surface and another powder having no lubricant 20 attached to the surface. Iron-based particles 12 and a lubricant 20 are provided. The iron-based particles 11 have a particle size exceeding 38 μm, a surface area S [m ² ], a volume V [m ³ ], a BET specific surface area B [m ² / g], and a true density ρ [g / m ³ ]. In this case, the average value of F represented by F = (B × V × ρ) / S is 2 or more and 20 or less.

Specifically, as shown in FIG. 2, the iron-based particles 11 have irregularities on the surface. In the present invention, F is used as an index for this uneven shape. As shown in FIG. 2, the surface area S [m ² ] is the area of the projected image of the iron-based particles 11 obtained by projecting one arbitrarily selected iron-based particle 11 (of the iron-based particles 11 in FIG. 2). Surface area S). The surface area S [m ² ] can be measured using a commercially available image processing apparatus. The volume V [m ³ ] is obtained as a circle equivalent diameter (projected area circle equivalent diameter) D [m], which is the diameter of a circle having an area equal to the surface area S [m ² ], and V = (1/6) π × obtained from the equation D ^3. The BET specific surface area B [m ² / g] is obtained from the amount of adsorption by adsorbing molecules having a known occupation area on the surface of the iron-based particles 11. The true density ρ [g / m ³ ] is obtained by measuring the actual volume of the iron-based particles 11 and dividing the mass of the iron-based particles 11 by the value. And the value of F in any iron-based particle 11 is obtained from the equation F = (B × V × ρ) / S. And the average value of F calculated | required by taking 500 or more powder molding particles (sample) which comprises the powder for powder molding is 2 or more and 20 or less. The average value of F is preferably 4 or more and 16 or less. If the average value of F is smaller than 2, a dent for adhering the lubricant 20 to the surface of the iron-based particles 11 cannot be secured. By setting it to 4 or more, it is possible to sufficiently secure a dent for attaching the lubricant 20 to the surface of the iron-based particles 11. On the other hand, if the average value of F exceeds 20, the irregularities on the surface of the iron-based particles 11 are too large, so that it cannot be filled with high density, and the compact obtained by compacting may be densified. Can not. By setting the average value of F to 16 or less, it can be filled with a higher density and a molded body with a higher density.

  The particle size of the iron-based particles 11 exceeds 38 μm, and preferably exceeds 75 μm. In addition, the iron-base particle 11 which does not pass the sieve whose nominal dimension set to JIS Z8801-1 is 38 micrometers, makes the particle size over 38 micrometers, and the iron-base particle which passes the sieve whose nominal dimension specified to JIS Z8801-1 is 38 micrometers 11 is a particle size of 38 μm or less. Further, the iron base particles 11 having a nominal size defined in JIS Z8801-1 that do not pass through a sieve having a nominal size of 75 μm exceed 75 μm, and the iron base particles 11 having a nominal size specified in JIS Z8801-1 through a sieve having a nominal size of 75 μm. Is set to a particle size of 75 μm or less.

  The upper limit of the particle size of the iron-based particles 11 is preferably 500 μm or less, and more preferably 350 μm or less in order to suppress an increase in eddy current loss of the dust core, for example.

  Moreover, it is preferable that the powder for compacting is further provided with another iron-based particle 12. Another iron-based particle 12 does not have a lubricant attached to its surface. The particle size of the other iron-based particles 12 is preferably 38 μm or less when the iron-based particles 11 have a particle size exceeding 38 μm, and 75 μm or less when the iron-based particles 11 exceed 75 μm. Is preferred.

  If the particle size of the iron-based particles 11 having the lubricant 20 attached to the surface exceeds 38 μm, the particle size of the other iron-based particles 12 not having the lubricant 20 attached to the surface exceeds 38 μm. And may be 75 μm or less. That is, according to the present invention, the particle size of a part of the iron-based particles 11 having the lubricant 20 attached to the surface is smaller than the particle size of another iron-based particle 12 having no lubricant 20 attached to the surface. Including cases.

  The iron-based particles 11 and the other iron-based particles 12 are, for example, iron (Fe), iron (Fe) -silicon (Si) based alloys, iron (Fe) -aluminum (Al) based alloys, iron (Fe). -Nitrogen (N) alloy, iron (Fe) -nickel (Ni) alloy, iron (Fe) -carbon (C) alloy, iron (Fe) -boron (B) alloy, iron (Fe) -cobalt (Co) -based alloy, iron (Fe) -phosphorus (P) -based alloy, iron (Fe) -nickel (Ni) -cobalt (Co) -based alloy, and iron (Fe) -aluminum (Al) -silicon (Si) -based It is formed from an alloy or the like. The iron-based particles 11 and the other iron-based particles 12 may be a single metal or an alloy.

  The equivalent circle diameter D of the iron-based particles 11 is preferably 110 μm or more and 250 μm or less. By setting the equivalent circle diameter D of the iron-based particles 11 to 110 μm or more, the iron-based particles 11 are not easily oxidized. By setting the equivalent circle diameter D to 250 μm or less, it is possible to suppress a decrease in the compressibility of the mixed powder during pressure molding. Thereby, it can prevent that the density of the molded object obtained by pressure molding does not fall, and handling becomes difficult.

  The average value G of the ratio of the lubricant 20 existing outside the convex hull 30 of the iron-based particles 11 is preferably 18% or less, more preferably 14% or less, and most preferably 10% or less. More specifically, image processing is performed on the iron-based particles 11 to which the lubricant 20 is adhered, and the average value G of the ratio is obtained. A commercially available image processing apparatus can be used for the image processing. In the image processing apparatus, the image sensor of the CCD camera receives the reflected light of the light irradiated on the cross section obtained by further mirror-finishing the “iron-based particles 11 with the lubricant 20 attached” embedded in the resin, and the light intensity is converted into an electric signal. Turn into. When this original image is subjected to noise removal processing or the like, in the cross section of the “iron-base particles 11 with the lubricant 20 attached”, the iron-base particles 11 become white because they easily reflect light, and the lubricant 20 absorbs light. It becomes black because it is easily scattered. In this way, black and white binarization is performed to distinguish and reveal the iron-based particles 11 (shape) and the lubricant 20. The convex hull 30 of the iron-based particles 11 that has been revealed is obtained by calculation. The convex area is an area where a line segment connecting any two points in the area always passes through the area. The convex hull 30 is the smallest convex region including an arbitrary region in the iron-based particle 11.

  Then, the ratio of the area of the lubricant 20 existing outside the convex hull 30 to the total area of the lubricant 20 is obtained for the cross-sectional image of the iron-based particles 11 to which the arbitrary lubricant 20 is attached. The average value G obtained by taking 500 or more samples is preferably 18% or less, more preferably 14% or less, and most preferably 10% or less. By setting the average value G of the ratio to 18% or less, the fluidity can be improved when filling the mold. Further, it is possible to prevent the secondary particles from being aggregated by being combined with the lubricant 20 of the other iron-based particles 11 having the lubricant 20 attached to the surface. By setting it to 14% or less, the fluidity can be further improved, and by setting it to 10% or less, the fluidity can be further improved.

  The lubricant 20 may be liquid or solid at room temperature, but is preferably a solid that hardly changes with time at room temperature. As the lubricant 20, for example, a hydrocarbon lubricant, a fatty acid lubricant, an amide lubricant, an ester lubricant, a higher alcohol lubricant, a metal soap, a composite lubricant, and the like can be used. Lubricant 20 is paraffin wax, microwax, polyethylene wax as hydrocarbon lubricant, stearic acid, behenic acid, 1,2-hydroxystearic acid as fatty acid lubricant, and stearamide as amide lubricant. Oleic acid amide, erucic acid amide, methylene bis stearic acid amide, ethylene bis stearic acid amide, ethylene bisolefinic acid amide, stearic acid monoglyceride, pentaerythritol tetrastearate, hydrogenated castor oil, stearyl stearate As higher alcohols, myristyl alcohol, palmityl alcohol, stearyl alcohol, behenyl alcohol, and metal soaps as calcium stearate, zinc stearate, magnesium stearate Um, it can be preferably used lead stearate.

  The lubricant 20 is preferably contained in an amount of 0.05% by weight to 0.4% by weight with respect to the iron-based particles 11 to which the lubricant is attached. By setting it as 0.05 weight% or more, the lubrication performance effect of the lubricant 20 can be expressed more. By setting the content to 0.4% by weight or less, the amount of the lubricant 20 remaining after compacting does not increase, and the densification of the compacted compact can be realized.

  The lubricant 20 preferably has a viscosity of 1 [mPa · s] to 30 [mPa · s] at a temperature 5 ° C. higher than the melting point. By setting it to 1 [mPa · s] or more, the lubricant 20 is sufficiently adhered to the recesses of the iron-based particles 11 because it is solid at normal temperature. By setting the viscosity to 30 [mPa · s] or less, the lubricant 20 adheres to the details of the recesses of the iron-based particles 11 because of low viscosity.

  In addition, the said viscosity is the value which heated and melt | dissolved the lubricant 20 put into the beaker in the oil bath, and measured with the B-type rotational viscometer.

  In addition, the lubricant 20 is preferably an ester lubricant or an amide lubricant with a low content of impure components. As the ester-based lubricant having a low content of impure components, for example, it is preferable that the acid value is 1 mgKOH / g or less and the hydroxyl value is 4 mgKOH / g or less. In addition, as the amide-based lubricant having a low content of impure components, for example, the acid value is preferably 1 mgKOH / g or less and the amine value is preferably 4 mgKOH / g or less. Ester lubricants or amide lubricants with a low content of impure components can be used alone or in combination. If the melting temperature region of the lubricant 20 has a narrow melt property, the lubricant 20 is more adhered to the details of the recesses of the iron-based particles 11. The “acid value” and “hydroxyl value” are values measured according to JIS K0070. The “amine value” is a value measured according to an indicator titration method in JIS K7237.

  Moreover, as shown in FIGS. 3 and 4, the powder for compacting is preferably further provided with an insulating coating 40 formed on the surfaces of the iron base particles 11 and the other iron base particles 12. The insulating coating 40 functions as an insulating layer between the iron-based particles 11 and the other iron-based particles 12. By covering the iron-based particles 11 and the other iron-based particles 12 with the insulating coating 40, the electrical resistivity ρ of the powder magnetic core obtained by pressure molding the powder for powder molding can be increased. Thereby, it can suppress that an eddy current flows between the iron base particle 11 and another iron base particle 12, and can reduce the eddy current loss of a powder magnetic core. Further, the insulating coating 40 attached to the surface of the iron base particles 11 is formed in order to increase the affinity with the lubricant 20 and to make the lubricant 20 easily adhere to the recesses of the iron base particles 11. FIG. 3 is an enlarged view schematically showing iron-based particles having an insulating coating in the embodiment of the present invention. FIG. 4 is an enlarged view schematically showing another iron-based particle having an insulating coating according to an embodiment of the present invention.

  The insulating coating 40 covers the surface of the iron-based particles 11 and preferably has a substantially uniform thickness in order to take advantage of the irregular shape of the iron-based particles 11. The thickness of the insulating coating 40 is preferably 20 nm or less.

  The insulating coating 40 is preferably made of an inorganic compound containing oxygen atoms, and more preferably made of iron phosphate, manganese phosphate, zinc phosphate, calcium phosphate, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, or the like. . The insulating coating 40 may be formed in one layer as shown in FIGS. 3 and 4 or may be formed in multiple layers.

  Next, the manufacturing method of the powder for compacting in the embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a flowchart showing a method for producing a powder for compacting according to the embodiment of the present invention. FIG. 6 is a schematic diagram showing the relationship between the particle size and the frequency of the powder for compacting in the embodiment of the present invention. FIG. 7 is a schematic diagram showing the relationship between the particle size and the frequency in the measurement process according to the embodiment of the present invention. FIG. 8 is a schematic diagram showing a state in which iron-based particles having a lubricant adhering to the surface thereof are turned into secondary particles.

As shown in FIG. 5, first, assuming that the surface area S [m ² ], the volume V [m ³ ], the BET specific surface area B [m ² / g], and the true density ρ [g / m ³ ], F = The preparatory step (S10) for preparing the iron-based particles 11 having an average value of F represented by (B × V × ρ) / S of 2 or more and 20 or less and a particle size exceeding 38 μm is performed. In the preparation step (S10) in the present embodiment, for example, the following steps are performed.

  Specifically, first, an iron-based particle preparation step (S11) for preparing iron-based particles is performed. An arbitrary method can be employ | adopted for an iron-base particle preparation process (S11), for example, iron-base particle is prepared by manufacturing an iron-base particle by the gas atomization method or the water atomization method. From the viewpoint of easily producing iron-based particles having irregularities on the surface where the average value of F is 2 or more and 20 or less, iron-based particles can be prepared by producing iron-based particles by a water atomization method. preferable.

  And the classification process (S12) which classifies the iron base particles prepared in the iron base particle preparation process (S11) into the iron base particles 11 having a particle diameter of more than 38 μm and the other iron base particles 12 having a particle diameter of 38 μm or less. ). In the classification step (S12), a sieve having a nominal size of 38 μm as defined in JIS Z8801-1 is prepared. Then, the prepared iron-based particles are passed through a sieve having a nominal size of 38 μm, and the iron-based particles that have not passed through are made iron-based particles 11 having a particle diameter exceeding 38 μm. Thereby, the iron-based particle | grains 11 whose average value of F is 2-20 and whose particle size exceeds 38 micrometers can be prepared. In the classification step (S12), the iron base particles that pass through a sieve having a nominal size of 38 μm are made into another iron base particle 12 having a particle size of 38 μm or less, and the other iron base particles 12 are mixed in a mixing step (described later). It may be used in S50) or may be stored or discarded.

  In the preparation step (S10), the classification step (S12) may be performed after the iron-base particle preparation step (S11) for preparing iron-base particles having an F average value of 2 or more and 20 or less. Moreover, in a preparatory process (S10), even if it implements the process of selecting the iron base particle whose average value of F is 2-20, after implementing an iron base particle preparatory process (S11) and a classification process (S12). Good.

In the preparation step (S10), when the surface area S [m ² ], the volume V [m ³ ], the BET specific surface area B [m ² / g], and the true density ρ [g / m ³ ] are set, F = It is preferable to prepare iron-based particles having an average value of F represented by (B × V × ρ) / S of 2 or more and 20 or less and a particle size exceeding 75 μm. In this case, in the classification step (S12), the only difference is that a sieve having a nominal size defined in JIS Z 8801-1 of 75 μm is prepared.

  Moreover, you may prepare the iron-base particle | grains 11 of arbitrary particle diameters exceeding 38 micrometers by changing the nominal dimension of a sieve. For example, when the nominal size of the sieve is x, iron-based particles 11 having a particle size exceeding x can be prepared.

  Next, an attaching step (S20) for attaching the lubricant 20 to the surface of the iron-based particles 11 is performed. In the adhesion step (S20) in the present embodiment, for example, the following steps are performed.

  Specifically, first, the lubricant 20 is prepared. At this time, it is preferable to prepare the lubricant 20 having an average particle diameter of 1 mm or less. By setting the average particle size to 1 mm or less, the dispersibility of the lubricant 20 in the iron-based particles 11 is improved.

  Moreover, it is preferable to prepare the lubricant 20 having a viscosity of 1 [mPa · s] to 30 [mPa · s] at a temperature 5 ° C. higher than the melting point. By setting it to 1 [mPa · s] or more, it is possible to prevent the lubricant 20 from flowing before adhering to the iron-based particles 11. By setting the viscosity to 30 [mPa · s] or less, the lubricant 20 easily adheres to the details of the recesses of the iron-based particles 11 because of low viscosity.

  Also, a lubricant 20 having at least one of an ester bond and an amide bond, an acid value of 1 [mgKOH / g] or less, and a sum of a hydroxyl value and an amine value of 4 [mgKOH / g] or less is prepared. It is preferable to do. If the melt temperature range is narrow, the lubricant 20 tends to adhere to the details of the recesses of the iron-based particles 11.

  Then, for example, the iron base particles 11 and the prepared lubricant 20 are mixed using a stirring mixer capable of heating the inside of the mixing container. For example, after mixing of the iron-based particles 11 and the lubricant 20 is started, the temperature of the mixing container is raised. Alternatively, for example, the temperature in the mixing container is raised in advance to a temperature at which the lubricant 20 melts, and then the iron-based particles 11 and the lubricant 20 are added to the mixing container and mixing is started. Thereby, the lubricant 20 is dispersed and attached to the surface of the iron-based particles 11.

  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.

  Then, while mixing, the temperature in the mixing container is raised to a temperature equal to or higher than the melting point of the lubricant 20 to melt the lubricant 20. As a result, the molten lubricant 20 is impregnated in the recesses of the iron-based particles 11. In addition, when the lubricant 20 is impregnated in the iron-based particles, the pressure condition in the mixing container is preferably normal pressure, reduced pressure, or vacuum. In particular, when the iron base particles 11 are impregnated with the lubricant 20 under reduced pressure or vacuum conditions, the air present in the gaps between the iron base particles 11 is easily removed. It can be impregnated efficiently.

  Then, after the impregnated lubricant 20 has passed for a certain time, the temperature in the mixing container is lowered to solidify the lubricant 20 and fix it to the iron-based particles 11. Thereby, the lubricant 20 impregnated in the iron-based particles 11 is fixed.

  In the attaching step (S30), it is preferable to attach the lubricant 20 so that it is contained in an amount of 0.05% by mass or more and 0.40% by mass or less with respect to the iron-based particles 11 to which the lubricant is attached. By setting it as 0.05 weight% or more, the lubricating performance effect of the lubricant 20 adhering to the recessed part of the iron base particle 11 can be expressed more. By setting the content to 0.4% by weight or less, the ratio of the lubricant 20 existing outside the convex hull 30 can be reduced.

  In addition, you may mix together lubricants other than the lubricant 20 as needed. In this case, when mixing the iron base particles 11 and the prepared lubricant 20, another lubricant may be further mixed, or after the iron base particles 11 are impregnated with the lubricant 20, other lubricants are mixed. An agent may be mixed. As other lubricants, for example, zinc stearate or h-BN can be added.

  Next, the average value G of the ratio of the lubricant 20 existing outside the convex hull 30 of the iron-based particles 11 is measured, and it is determined whether or not the average value G of the measured ratio is within 18%. A measurement process (S30) is implemented. Specifically, the average value G of the ratio is measured by the image processing method for the iron-based particles 11 after the attaching step (S20). As described above, this measurement can be performed by image processing, for example.

  In the measurement step (S30), when it is determined that the average value G is 10 or less, YES is determined in the measurement step (S30). In this case, the amount of the lubricant 20 existing outside the convex hull 30 of the iron-based particles 11 is small, and the relationship between the particle size and the frequency of the iron-based particles 11 shows the distribution shown in FIG. In the molding powder, the iron-based particles 11 with the lubricant 20 attached to the surface are formed.

  On the other hand, when it is determined in the measurement step (S30) that the average value G of the ratio exceeds 18%, NO is determined in the measurement step (S30). In this case, when image processing is performed, for example, as shown in FIG. 7, there are two peaks in which the particle size is concentrated in the relationship between the particle size and the frequency. As shown in FIG. 8, since the lubricant 20 protrudes outside the convex hull 30, the lubricant 20 on the surface of the iron-based particles 11 belonging to a relatively large range of particle diameters at the two peaks. There is a case where secondary particles are formed by agglomerating with other iron-based particles 11 attached thereto.

  When it is determined NO in the measurement step (S30), a pulverization step (S40) for pulverizing the aggregated particles by the lubricant 20 existing outside the convex hull 30 is performed. In the granulation step (S40), as shown in FIG. 8, the aggregated secondary particles are removed by pulverization or the like, and the lubricant 20 existing outside the convex hull 30 is reduced.

  In the measurement step (S30), the average value G of the ratio is preferably 18% or less, more preferably 14% or less, and most preferably 10% or less.

  Next, a measurement step (S30) is performed on the powder for compacting after the granulation step (S40). If it is determined NO in the measurement step (S30), the granulation step (S40) is performed. The measurement step (S30) and the pulverization step (S40) are repeated until the average value G becomes 10 or less.

  In the present embodiment, in the attaching step (S20), since the lubricant 20 is attached only to the surface of the iron-based particles 11 having a large particle size exceeding 38 μm, the lubricant existing outside the convex hull 30 is used. 20 can be reduced. Therefore, the measurement step (S30) and the pulverization step (S40) may be omitted. Moreover, a measurement process (S30) may be implemented and a granulation process (S40) may be abbreviate | omitted. In this case, the iron base particles 11 in which the lubricant 20 existing outside the convex hull 30 exceeds 18% or the agglomerated iron base particles 11 are discarded.

  Next, a mixing step (S50) is performed in which another iron-based particle 12 having a particle size of 38 μm or less is mixed with the iron-based particle 11 to which the lubricant 20 is attached. In the mixing step (S50), for example, in the classification step (S12) of the preparation step (S10), the iron base particles 12 that are determined to be NO because the particle size does not exceed 38 μm are adhered to the surface of the lubricant 20. The iron-based particles 11 are mixed. The mixing method is not particularly limited, and any method can be adopted.

  Further, in the preparation step (S10), even if the particle size exceeds 38 μm, another iron-based particle stored as the average value of F is not 2 or more and 20 or less is further mixed in the mixing step (S50). Also good.

  By carrying out the mixing step (S50), the iron-based particles 12 to which the lubricant 20 is not attached to the surface can be used because the particle size classified in the classification step (S12) is small. Therefore, more iron base particles prepared in the iron base particle preparation step (S11) can be used in some cases, which is advantageous in terms of cost. Moreover, since the iron-based particles 12 have a smaller particle size than the iron-based particles 11 having the lubricant 20 attached to the surface, press molding is advantageous for increasing the density of the molded body. Note that the mixing step (S50) may be omitted.

  In addition, in the mixing step (S50) when the iron-based particles 11 having a particle size exceeding 75 μm are prepared in the preparing step (S10), the particle size does not exceed 75 μm in the classification step (S12) of the preparing step (S10). The iron-based particles 12 determined as NO are mixed with the iron-based particles 11 having the lubricant 20 attached to the surface.

  In the mixing step (S50), the iron-based particles 12 to be mixed are not particularly limited to the above particle diameter. In the mixing step (S50), the iron-based particles 12 having a particle size of x or less divided when using a sieve having a nominal size x in the classification step (S12) of the preparation step (S10) Mix with iron-based particles 11.

  The powder for compacting shown in FIG. 1 can be manufactured by the above steps (S10 to S50).

  In addition, in the iron-based particle preparation step (S11), the prepared iron-based particles are divided into two or more, and in the classification step (S12), a sieve having a different nominal size of 38 μm or more is used for each and separated from the iron-based particles 11. The iron-based particles 12 may be classified. In this case, in the mixing step (S50), the iron base particles 11 having the lubricant 20 attached to the surface after the attaching step (S30) and the iron having no lubricant attached to the surface after the classification step (S12). The base particles 12 may be mixed.

  In addition, when manufacturing the powder for compacting molding provided with the insulation film 40 as shown in FIG. 3, the insulation film formation process which forms the insulation film 40 on the surface of the iron base particle 11 and another iron base particle 12 Is further provided.

  Specifically, the step of forming the insulating coating 40 is performed after the preparation step (S10), for example. In the insulating coating forming step, it is preferable to form an insulating coating 40 made of an inorganic compound containing oxygen atoms on the surfaces of the iron-based particles 11 and the other iron-based particles 12. The insulating coating 40 made of an inorganic compound containing oxygen atoms can be formed by, for example, chemical conversion treatment, solvent spraying or a sol-gel method using a precursor.

  When the powder for compacting thus produced is molded with a mold to obtain a molded body having a predetermined shape, even if the shape of the mold is complicated, it adheres to the recesses of the iron base particles 11. The lubricant 20 that flows out flows out into the mold with good dispersibility. Therefore, it is possible to obtain an excellent molded body that does not cause seizure between the mold and the molded body. Further, when the mold is filled with the powder for compacting, it can be filled with high density. Furthermore, since the powder for compacting is filled with the lubricant 20 in the recesses of the iron-based particles 11, the compact obtained by compacting has a high density.

As described above, according to the powder for compacting in the embodiment of the present invention, the surface area S [m ² ], the volume V [m ³ ], the BET specific surface area B [m ² / g], the true density ρ In the case of [g / m ³ ], the average value of F represented by F = (B × V × ρ) / S is 2 or more and 20 or less, and the surface of the iron-based particles 11 having a particle size of more than 38 μm. Lubricant 20 is attached. Thereby, since the unevenness | corrugation can be provided in the surface of the iron base particle 11, the lubricant 20 can be made to adhere to the recessed part of the iron base particle 11. FIG. In addition, since the lubricant 20 is attached to the surface of the iron base particles 11 having a particle diameter exceeding 38 μm, the lubricant 20 is attached to the recesses of the iron base particles 11, and the convex hull 30 of the iron base particles 11. It is possible to suppress the lubricant 20 from protruding and adhering to the outside. Therefore, the particles constituting the powder for compacting can be prevented from aggregating with each other, and thus the fluidity of the powder for compacting is not hindered. Therefore, it can be made into a powder for compacting which has good fluidity, can be filled with high density, and becomes a compact with high density when compacted.

  In this example, the effect of providing iron-based particles having a particle size of more than 38 μm and an F average value of 2 to 20 was examined.

(Invention Examples 1 to 10)
The compacting powders of Invention Examples 1 to 10 were produced according to the present embodiment. Specifically, in the preparation step (S10), as the iron-based particle preparation step (S11), a trade name “Somaloy 500” manufactured by Henegas Co., Ltd. was prepared. The product name “Somaloy 500” manufactured by Henegas Co., Ltd. is composed of iron-based particles containing pure iron with a purity of 99.98% or more, the balance being inevitable impurities, and iron phosphate covering the surface of the iron-based particles. And an insulating coating. And in the classification step (S12), using the sieves defined in JIS Z 8801-1 having the nominal dimensions shown in Table 1 below, the iron-based particles that did not pass through the sieves have a particle diameter exceeding the nominal dimension of the sieves. did.

  Since the thickness of the insulating coating is 100 nm or less, the particle size of the iron-based particles used in this example is sufficiently larger than that of the insulating coating. Therefore, there is no need to consider the thickness of the insulating coating, and the particle size of the Somaloy 500 can be approximated to the particle size of the iron-based particles.

In the iron-based particle preparation step (S11), when the volume V [m ³ ], the BET specific surface area B [m ² / g], and the true density ρ [g / m ³ ] are set, F = (B × V The iron-based particle | grains whose average value of F represented by * (rho)) / S is 2-20 is prepared. Specifically, the average value of F in Invention Examples 1 to 10 was as shown in Table 1 below.

  Next, in the attaching step (S20), an ester of an aliphatic monoalcohol and an aliphatic monocarboxylic acid was prepared as a lubricant. The lubricant had a melting point of 73 ° C., an acid value of 0.6 [mgKOH / g], and a hydroxyl value of 3.0 [mgKOH]. And it heated at 78 degreeC, and the addition amount lubricant shown in Table 1 was made to adhere to iron base particles. The viscosity of the lubricant at the heated temperature was 15 [mPa · s]. Moreover, the average value G of the ratio after an adhesion process (S20) became a value as shown in Table 1.

  Next, about the present invention examples 5-8, the mixing process (S50) was implemented. In the mixing step (S50), another iron-based particle that passed through the sieve in the classification step (S12) was mixed with the iron-based particle having the lubricant attached to the surface.

  By carrying out the above steps, powders for compacting in Examples 1 to 10 of the present invention were produced.

(Comparative Example 1)
The powder for compacting in Comparative Example 1 was basically produced in the same manner as in Example 1 of the present invention, but differs only in that the classification step (S12) was not performed. As a result, in Comparative Example 1, the lubricant was also adhered to the surface of the iron-based particles having a particle size of 38 μm or less.

(Comparative Example 2)
The powder for compacting in Comparative Example 2 was basically produced in the same manner as in Example 2 of the present invention, but differs only in that the classification step (S12) was not performed. As a result, in Comparative Example 2, the lubricant was adhered to the surface of the iron-based particles having a particle size of 38 μm or less.

(Comparative Example 3)
The powder for compacting in Comparative Example 3 was basically produced in the same manner as in Example 1 of the present invention, except that iron-based particles having an average F value of 1 were prepared in the iron-based particle preparation step (S11). Only different. As a result, in Comparative Example 3, a lubricant was adhered to the surface of the iron-based particles having an average value of F of 1.

(Comparative Example 4)
The powder for compacting in Comparative Example 4 was basically produced in the same manner as in Example 1 of the present invention, except that iron-based particles having an average F value of 24 were prepared in the iron-based particle preparation step (S11). Only different. As a result, in Comparative Example 4, a lubricant was adhered to the surface of the iron-based particles having an average value of F of 24.

(Measuring method)
About the obtained powder for compacting | molding of this invention Examples 1-10 and Comparative Examples 1-4, the flow time (FR value) and the apparent density (AD value) were measured, respectively. The flow time (FR value) was measured according to JIS Z 2502. The apparent density (AD value) was measured according to JIS Z 2504. These results are shown in Table 2 below. The smaller the value of the flow time (FR value), the better the fluidity, and the higher the apparent density (AD value), the higher the value.

Moreover, about the obtained powder for compacting of this invention Examples 1-10 and Comparative Examples 1-4, the pressure of 7 [ton / cm < ² >] was applied using the metal mold | die, and the molded object was produced, respectively. And the density of the produced molded object was measured by the Archimedes method. The results are shown in Table 2 below as the compact density. The compact density indicates that the larger the value, the higher the density.

(Measurement result)
As shown in Table 2, for Comparative Examples 1 and 2 in which a lubricant was adhered to iron-based particles having a small particle size, the fluidity, apparent density, and molded body density were worse than those of Inventive Examples 1 to 10. . This is presumably because the iron base particles were aggregated because the lubricant was adhered to the iron base particles having a small particle diameter.

  Moreover, about the comparative example 3 whose average value of F is 1, it was worse than the invention examples 1-10 about fluidity | liquidity, an apparent density, and a molded object density. In Comparative Example 4 in which the average value of F was 24, the flowability and the apparent density were good, but the compact density was poor.

  On the other hand, for the present invention examples 1 to 10 comprising iron-base particles having a particle diameter exceeding 38 μm and an average value of F in the range of 2 to 20, and a lubricant adhering to the surface of the iron-base particles, The fluidity, apparent density, and compact density were all excellent. In particular, Examples 5 to 8 of the present invention in which the mixing step (S50) was performed could achieve almost the same performance as Examples 1 to 4 of the present invention, which proved advantageous from the viewpoint of cost.

  As described above, according to the examples, all of fluidity, apparent density, and compact density are provided by providing iron-based particles having a particle size of more than 38 μm and an F average value of 2 or more and 20 or less. It was confirmed that the film was excellent. Therefore, according to the powder for compacting and the method for producing the powder for compacting in the present invention, it has good fluidity, can be filled with high density, and when compacted, It was confirmed that

  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 shown not by the above-described embodiment but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

It is a figure which shows typically the powder for compaction molding in embodiment of this invention. It is an enlarged view which shows typically the 1 particle | grains (particles for compacting) which comprise the powder for compacting in embodiment of this invention. It is an enlarged view which shows typically the iron-based particle | grains provided with the insulating film in embodiment of this invention. It is an enlarged view which shows typically another iron-based particle provided with the insulating film in embodiment of this invention. It is a flowchart which shows the manufacturing method of the powder for compacting shaping | molding in embodiment of this invention. It is a schematic diagram which shows the relationship between the particle size and frequency of the powder for compacting in the embodiment of the present invention. It is a schematic diagram which shows the relationship between the particle size and frequency in the measurement process of embodiment of this invention. It is a schematic diagram which shows the state which the iron base particle | grains which the lubricant has adhered to the surface turned into secondary particles.

Explanation of symbols

  11 iron-based particles, 12 other iron-based particles, 30 convex hulls, 40 insulating coatings.

Claims (12)

Iron-based particles,
A lubricant that adheres to the surface of the iron-based particles,
When the particle size of the iron-based particles exceeds 38 μm, the surface area S [m ² ], the volume V [m ³ ], the BET specific surface area B [m ² / g], and the true density ρ [g / m ³ ] a, Ri F = (B × V × ρ ) / mean value of F represented by S 2 or more 20 der less,
Wherein the lubricant, the average percentage of the lubricant the lubricant is present outside the convex hull of the iron-based particles that are adhered Ru der 18% or less, powder molding powder.   The powder for compacting according to claim 1, further comprising another iron-based particle having a particle size of 38 µm or less and having no lubricant attached to the surface. Iron-based particles,
A lubricant that adheres to the surface of the iron-based particles,
When the particle size of the iron-based particles exceeds 75 μm, the surface area S [m ² ], the volume V [m ³ ], the BET specific surface area B [m ² / g], and the true density ρ [g / m ³ ] a, Ri F = (B × V × ρ ) / mean value of F represented by S 2 or more 20 der less,
Wherein the lubricant, the average percentage of the lubricant the lubricant is present outside the convex hull of the iron-based particles that are adhered Ru der 18% or less, powder molding powder.   The powder for compacting according to claim 3, further comprising another iron-based particle having a particle diameter of 75 µm or less and having no lubricant attached to the surface. The said lubricant is 0.05 mass% or more and 0.40 mass% or less with respect to the said iron base particle to which the said lubricant is adhere | attached, For compacting shaping | molding in any one of Claims 1-4 Powder. Surface area S [m ² ], volume V [m ³ ], BET specific surface area B [m ² / g], true density ρ [g / m ³ ], F = (B × V × ρ) / S A preparation step of preparing iron-based particles having an average value of F of 2 to 20 and a particle size exceeding 38 μm;
And a deposition step of depositing the or lubricants on the surface of the iron-based particles,
In the adhesion step, the iron group is such that an average value of the ratio of the lubricant existing outside the convex hull of the iron-based particles to which the lubricant is adhered is 18% or less. Ru is deposited the lubricant to the surface of the particle, method of producing a powder for a green compact. The powder compact according to claim 6 , wherein in the preparation step, the iron-based particles are prepared by classification into iron-based particles having a particle size of more than 38 µm and other iron-based particles having a particle size of 38 µm or less. A method for producing a molding powder. The manufacturing method of the powder for powder compaction | molding of Claim 7 further equipped with the mixing process which mixes the said another iron base particle with a particle size of 38 micrometers or less with the said iron base particle to which the said lubricant is adhered. Surface area S [m ² ], volume V [m ³ ], BET specific surface area B [m ² / g], true density ρ [g / m ³ ], F = (B × V × ρ) / S A preparatory step of preparing iron-based particles having an average value of F of 2 or more and 20 or less and a particle size exceeding 75 μm;
And a deposition step of depositing the or lubricants on the surface of the iron-based particles,
In the adhesion step, the iron group is such that an average value of the ratio of the lubricant existing outside the convex hull of the iron-based particles to which the lubricant is adhered is 18% or less. Ru is deposited the lubricant to the surface of the particle, method of producing a powder for a green compact. 10. The powder compact according to claim 9 , wherein in the preparation step, the iron-based particles are prepared by classification into iron-based particles having a particle size exceeding 75 μm and other iron-based particles having a particle size of 75 μm or less. A method for producing a molding powder. Particle size below the another iron-based particles 75 [mu] m, further comprising a mixing step of mixing the iron-based particles which lubricant is deposited, a method of manufacturing a powder for a dust molding according to claim 1 0 . Wherein in the deposition step, to deposit the lubricant such that the lubricant is contained 0.40 wt% or less than 0.05 wt% with respect to the iron-based particles are attached, according to claim 6-1 1 The manufacturing method of the powder for compacting in any one.

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