JP4716434B2 - 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.

  Conventionally, when an iron-based powder is compacted in a mold to obtain a molded body having a predetermined shape, friction occurs between the interface between the mold wall surface and the iron-based powder particles, or between the iron-based powder particles. Lubricant is applied to the mold. 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 the above-mentioned Patent Document 1, there are cases where the lubricant is softened by heating and becomes sticky. In this case, there is a problem in that the secondary particles of the metal particles are caused as in the conventional method described above. . 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 according to the present invention includes iron-based particles and a lubricant that adheres to the surface of the iron-based particles. When the iron-based powder has a surface area S [m ² ], volume V [m ³ ], BET specific surface area B [m ² / g], and true density ρ [g / m ³ ], F = (B × V The average value of F represented by × ρ) / S is 2 or more and 20 or less. In the lubricant, the average value of the ratio of the lubricant existing outside the convex hull of the iron-based particles is 20% or less.

  According to the powder for compacting according to 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 average value of the ratio of the lubricant existing outside the convex hull is 20% or less, the lubricant adheres to the recesses of the iron-based particles, and there is not much lubricant outside the convex hull. Therefore, it is possible to prevent the particles from aggregating, so that fluidity is not hindered. Therefore, it is possible to obtain a powder for compacting that has good fluidity, can be filled at a high density, and becomes a compact body when compacted.

  The above-mentioned “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.

  In the iron-based particles, the lubricant is preferably contained in an amount of 0.05% by weight to 0.4% by weight with respect to the iron-based particles.

  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 the powder for compacting, preferably, the lubricant has a viscosity of 30 [mPa · s] or less at a temperature 5 ° C. higher than the melting point. By setting the viscosity to 30 [mPa · s] or less, the lubricant has a low viscosity, so that the lubricant is more adhered to the details of the recesses of the iron-based particles.

  In the powder for compacting, preferably, the lubricant has at least one of an ester bond and an amide bond, an acid value of 1 [mg KOH / g] or less, and a sum of a hydroxyl value and an amine value of 4 [ mgKOH / g] or less.

  Thereby, since the melt temperature range of the lubricant has a sharp melt property, the lubricant is more adhered to the details of the recesses of the iron-based particles.

  The “acid value” is the number of mg of potassium hydroxide (KOH) required to neutralize the acid of 1 g of the sample, and the measurement is based on JIS K0070. The “hydroxyl value” is the number of mg of potassium hydroxide (KOH) required to neutralize acetic acid bonded to a hydroxyl group when 1 g of a sample is acetylated, and the measurement is based on JIS K0070. The “amine value” is the number of mg of potassium hydroxide (KOH) equivalent to hydrochloric acid required to neutralize 1 g of a sample, and the measurement is based on ASTM D 2074.

  Preferably, the powder for compacting is further provided with a film made of an inorganic compound containing oxygen atoms on the surface of the iron-based particles.

  Thereby, affinity with a lubricant increases and the lubricant adheres more to the details of the recesses of the iron-based particles.

The method for producing a powder for compacting of the present invention comprises an iron-based particle preparation step, a lubricant preparation step, and an adhesion step. In the iron-based particle 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 Iron base particles having an average value of F represented by × V × ρ) / S of 2 or more and 20 or less are prepared. In the lubricant preparation step, a lubricant is prepared. In the attaching step, the iron-based particles and the lubricant are attached by heating at a temperature equal to or higher than the melting point of the lubricant.

  According to the method for producing a powder for compacting of the present invention, since the average value of F of the iron base particles prepared in the iron base particle preparation step is 2 or more and 20 or less, the surface has an appropriate dent and is high. We prepare iron-based particles that can be filled to the density. Further, by carrying out the adhering step after the mixing step, the lubricant can be adhered to the iron base particles so that the average value of the ratio of the lubricant present outside the convex hull of the iron base particles is lowered. Therefore, the lubricant adheres to the recesses of the iron base particles, and there is not much lubricant outside the convex closure of the iron base particles, so the dispersibility of the lubricant in the iron base particles is good and the lubricant Can be prevented from being aggregated and the particles are aggregated. Therefore, it is possible to produce a powder for compacting which has good fluidity, can be filled at a high density, and becomes a high-density compact when compacted.

  In the above method for producing a powder for compacting, preferably, in the lubricant preparation step, 0.05 wt% or more and 0.4 wt% or less of the lubricant is prepared with respect to the iron base particles.

  By setting it as 0.05 weight% or more, the powder for compacting which can express the lubricating performance effect of a lubricant more can be manufactured. By setting the content to 0.4% by weight or less, the amount of lubricant remaining after compacting does not increase, and a powder for compacting that can realize a high density compacted compact can be produced.

  In the method for producing a powder for compacting, preferably, in the lubricant preparation step, a lubricant having an average particle size of 1 mm or less is prepared. Thereby, the dispersibility of the lubricant becomes better in the mixing step.

  Preferably, the above method for producing a powder for compacting further includes a classification step and a pulverization step. In the classification step, after the adhesion step, the average value of the ratio of the lubricant existing outside the convex hull of the iron-based particles is measured, and it is determined whether or not the average value of the measured ratio is within 20%. To do. In the pulverization step, when it is determined that the average value of the ratio exceeds 20% in the classification step, the agglomerated particles are pulverized by the lubricant present outside the convex hull.

  By carrying out the granulation step until the average value of the ratio of the lubricant existing outside the convex hull of the iron-based particles in the classification process is determined to be 20% or less, the pressure at which the average value of the ratio becomes 20% or less Powder for powder molding can be produced.

  Preferably, the method for producing a powder for compacting further includes a step of forming a film made of an inorganic compound containing oxygen atoms on the surface of the iron-based particles.

  Thereby, the powder for compacting which equips the surface of iron base particles with a film can be manufactured. Therefore, it is possible to produce a powder for compacting, in which the affinity with the lubricant is increased and the lubricant is more adhered to the details of the recesses of the iron-based particles.

  According to the powder for compacting of the present invention, the iron-base particles having irregularities formed on the surface and the lubricant that adheres to the concave portions of the iron-base particles and does not exist so much outside the convex hull are provided. Therefore, the powder for compacting which has favorable fluidity | liquidity, can be filled with high density, and becomes a high-density molded object when compacted is formed.

  Moreover, according to the manufacturing method of the powder for compacting of this invention, the iron base particle which has a suitable dent on the surface is prepared at the iron base particle preparation process. Further, in the attaching step, the lubricant is attached to the iron-based particles so that the average value of the ratio of the lubricant existing outside the convex closure of the iron-based particles is lowered. Therefore, it is possible to produce a powder for compacting which has good fluidity, can be filled at a high density, and becomes a high-density compact when compacted.

  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 (A) is an enlarged view schematically showing one particle (compact molding particle 1) constituting the compacting powder in the embodiment of the present invention. As shown in FIG. 1 and FIG. 2 (A), the powder for compacting in the present embodiment includes iron base particles 10 and a lubricant 20. When the iron-based particles 10 have 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 ], F = (B × The average value of F represented by V × ρ) / S is 2 or more and 20 or less. The lubricant 20 is attached to the surface of the iron base particles 10. In the lubricant 20, the average value of the ratio of the lubricant 20 existing outside the convex hull 30 of the iron-based particles 10 is 20% or less.

Specifically, as shown in FIG. 2, the iron-based particles 10 have irregularities on the surface. In the present invention, F is used as an index for this uneven shape. As shown in FIG. 2A, the surface area S [m ² ] is the area of the projected image of the iron-based particles 10 obtained by projecting one arbitrarily selected iron-based particle 10 (the iron group in FIG. 2). It refers to the area S) of the particles 10. 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 a molecule whose occupation area is known on the surface of the iron-based particle 10. The true density ρ [g / m ³ ] is obtained by measuring the actual volume of the iron base particles 10 and dividing the mass of the iron base particles 10 by the value. Then, the value of F in any iron-based particle 10 is obtained from the formula F = (B × V × ρ) / S. And the average value of F calculated | required by taking 500 or more of the powder molding particles 1 (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 10 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 10. On the other hand, if the average value of F exceeds 20, the irregularities on the surface of the iron-based particles 10 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 it to 16 or less, it can be filled with a higher density and a molded body with a higher density.

  The iron-based particles 10 are, for example, iron (Fe), iron (Fe) -silicon (Si) alloy, iron (Fe) -aluminum (Al) 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, etc. . The iron-based particles 10 may be a single metal or an alloy.

  The equivalent circle diameter D of the iron-based particles 10 is preferably 5 μm or more and 200 μm or less. By setting the equivalent circle diameter D of the iron-based particles 10 to 5 μm or more, the iron-based particles 10 are hardly oxidized. By setting the equivalent circle diameter D to 200 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 of the ratio G of the lubricant 20 existing outside the convex hull 30 of the iron-based particles 10 is 20% or less. Specifically, the average value G is obtained by performing image processing on the iron-based particles 10 to which the lubricant 20 is adhered. 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 mirroring the “iron-base particles 10 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 10 with the lubricant 20 attached”, the iron base particles 10 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, and the iron-based particles 10 (shape) and the lubricant 20 are distinguished and revealed. The convex hull 30 of the iron-based particle 10 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 that includes an arbitrary region in the iron-based particle 10.

  The ratio of the area of the lubricant 20 existing outside the convex hull 30 to the total area of the lubricant 20 with respect to the cross-sectional image of the iron-based particles 10 (compact molding particles 1) to which the optional lubricant 20 is attached. Is a ratio G. And the average value of the ratio G obtained by taking 500 or more samples is 20% or less. When the average value of the ratio G exceeds 20%, the fluidity deteriorates when filling the mold, and secondary particles aggregated by being combined with the lubricant of the other iron-based particles 10 are caused.

  The lubricant 20 may be a liquid or a solid at room temperature, but is preferably a solid with little change over time. 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. The lubricant 20 is a paraffin wax, microwax, polyethylene wax as a hydrocarbon lubricant, stearic acid, behenic acid, 1,2-hydroxystearic acid as a fatty acid lubricant, and stearamide as an 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, Stearyl alcohol is preferably used as the higher alcohol type, and calcium stearate, zinc stearate, magnesium stearate, lead stearate and the like can be preferably used as the metal soap.

  The lubricant 20 is preferably contained in an amount of 0.05 wt% or more and 0.4 wt% or less with respect to the iron-based particles 10. 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 0.1 [mPa · s] or more and 30 [mPa · s] or less at a temperature 5 ° C. higher than the melting point. By setting it to 0.1 [mPa · s] or more, the lubricant 20 is sufficiently adhered to the recesses of the iron-based particles 10 because it is solid at normal temperature. By setting the viscosity to 30 [mPa · s] or less, since the viscosity is low, the lubricant 20 is more adhered to the details of the recesses of the iron-based particles 10.

  In addition, the said melting | fusing point 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.

  The lubricant 20 has 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. preferable. 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 10.

  Moreover, as shown in FIG. 2 (B), it is preferable to further include a film 40 made of an inorganic compound containing oxygen atoms on the surface of the iron-based particles 10. FIG. 2B is an enlarged view schematically showing one particle of the powder for compacting provided with the coating film in the embodiment of the present invention.

  The coating 40 is formed to increase the affinity with the lubricant 20 and to make the lubricant 20 easily adhere to the recesses of the iron-based particles 10. The coating 40 covers the surface of the iron-based particles 10 and preferably has a substantially uniform thickness in order to take advantage of the uneven shape of the iron-based particles 10. The thickness of the coating 40 is preferably 20 nm or less.

  The coating 40 is not particularly limited as long as it is an inorganic compound containing oxygen atoms, but is preferably made of iron phosphate, manganese phosphate, zinc phosphate, calcium phosphate, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, or the like. . The coating 40 may be formed in one layer as shown in FIG. 2B, 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. 3 is a flowchart showing a method for producing a powder for compacting according to the embodiment of the present invention. FIG. 4 is a diagram for explaining the classification process in the embodiment of the present invention, (A) is a schematic diagram showing the relationship between the particle size and the frequency in the classification process, and (B) is a state in which secondary particles are formed. It is a schematic diagram which shows. FIG. 5 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.

As shown in FIG. 3, 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 = An iron-based particle preparation step (S10) for preparing iron-based particles 10 having an average F value of 2 to 20 represented by (B × V × ρ) / S is performed. In the iron-based particle preparation step (S10), the manufacturing method of the iron-based particles 10 is not particularly limited as long as the average value of F is 2 or more and 20 or less. For example, the iron-based particles 10 are manufactured by a gas atomization method or a water atomization method. be able to. From the viewpoint of easy production of the iron-based particles 10 having irregularities on the surface where the average value of F is 2 or more and 20 or less, the iron-based particles 10 are preferably produced by a water atomization method.

  Next, a lubricant preparation step (S20) for preparing the lubricant 20 is performed. In the lubricant preparation step (S20), it is preferable to prepare 0.05 wt% or more and 0.4 wt% or less of the lubricant 20 with respect to the iron-based particles 10. 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 10 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 the lubricant preparation step (S20), 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 10 becomes good.

  In the lubricant preparation step (S20), it is preferable to prepare the lubricant 20 having a viscosity of 0.1 [mPa · s] to 30 [mPa · s] at a temperature 5 ° C. higher than the melting point. By setting it to 0.1 [mPa · s] or more, it is possible to prevent the lubricant 20 from flowing before adhering to the iron-based particles 10. 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 10 because of low viscosity.

  In the lubricant preparation step (S20), at least one of an ester bond and an amide bond is included, the acid value is 1 [mgKOH / g] or less, and the sum of the hydroxyl value and the amine value is 4 [mgKOH / g] or less. It is preferable to prepare the lubricant 20 which is When the melt temperature range is narrow, the lubricant 20 tends to adhere to the details of the recesses of the iron-based particles 10.

  Next, an adhesion step (S30) in which the iron base particles 10 and the lubricant 20 are adhered by heating at a temperature equal to or higher than the melting point of the lubricant 20 is performed. The adhering step (S30) includes a mixing step (S31) in which the iron base particles 10 and the lubricant 20 are mixed, an impregnation step (S32) in which the iron base particles 10 are impregnated with the lubricant 20, and an impregnation in the iron base particles 10 A fixing step (S33) for fixing the lubricant 20 that has been performed. In the attaching step (S30), first, a mixing step (S31) for mixing the iron base particles 10 and the lubricant 20 is performed. In the mixing step (S31), the iron base particles 10 and the lubricant 20 are mixed using, for example, a stirring mixer that can heat the inside of the mixing container. Thereby, the lubricant 20 is dispersed and attached to the surface of the iron-based particles 10.

  In addition to the case where the temperature of the mixing container is increased after the mixing of the iron-based particles 10 and the lubricant 20 as described above, the temperature in the mixing container is increased in advance to the temperature at which the lubricant 20 melts. After that, the iron-base particles 10 and the lubricant 20 may be added to the mixing container to start mixing.

  Furthermore, there is no particular limitation on the mixing method, for example, mechanical alloying method, vibration ball mill, planetary ball mill, mechanofusion, coprecipitation method, chemical vapor deposition method (CVD method), physical vapor deposition method (PVD method), plating Any of the method, sputtering method, vapor deposition method or sol-gel method can be used.

  Next, an impregnation step (S32) in which the iron base particles 10 are impregnated with the lubricant 20 is performed. In the impregnation step (S32), the temperature in the mixing container is raised to a temperature equal to or higher than the melting point of the lubricant 20 while mixing, and the lubricant 20 is melted. Thereby, the molten lubricant 20 is impregnated in the recesses of the iron-based particles 10.

  Next, a fixing step (S33) for fixing the lubricant 20 impregnated in the iron-based particles 10 is performed. In the fixing step (S <b> 33), the temperature in the mixing container is lowered after a certain period of time, and the lubricant 20 is solidified and fixed to the iron base particles 10.

  In addition, you may mix together lubricants other than the lubricant 20 as needed. In this case, another lubricant may be mixed in the mixing step (S31), or after the lubricant 20 is impregnated in the iron-based particles 10 in the impregnation step (S32), the other lubricant is mixed. May be. 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 10 is measured, and it is determined whether or not the average value of the measured ratio G is within 20%. A classification step (S40) is performed. Specifically, the average value of the ratio G is measured by an image processing method for the powder for compacting produced in the attaching step (S30). As described above, this measurement can be performed by image processing, for example.

  In the classification step (S40), when it is determined that the average value G is 20 or less, YES is determined in the classification step (S40). In this case, the lubricant present outside the convex hull 30 is small, and the relationship between the particle size and the frequency shows the distribution shown in FIG. 5, resulting in the powder for compacting shown in FIG.

  On the other hand, if it is determined in the classification step (S40) that the average value G exceeds 20%, NO is determined in the classification step (S40). In this case, when the image processing is performed, for example, as shown in FIG. 4A, the powder molding particles 1 having a large particle diameter are present within a predetermined range. As shown in FIG. 4B, the powder molding particles 1 having a large particle size are aggregated with other powder molding particles 1 because the lubricant 20 protrudes outside the convex hull 30. In this case, secondary particles are generated.

  When it is determined NO in the classification step (S40), a pulverization step (S50) for pulverizing the aggregated particles by the lubricant 20 existing outside the convex hull 30 is performed. In the pulverization step (S50), as shown in FIG. 4B, the aggregated secondary particles are removed by pulverization or the like, and the lubricant 20 existing outside the convex hull 30 is reduced.

  Next, a classification step (S40) is performed on the powder for compacting after the granulation step (S50). If it is determined NO in the classification step (S40), the granulation step (S50) is performed. The classification step (S40) and the pulverization step (S50) are repeated until the average value G is 20 or less.

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

  In addition, when manufacturing the powder for compacting shaping | molding provided with the film 40 as shown in FIG. 2, by further providing the process of forming the film which consists of an inorganic compound containing an oxygen atom on the surface of the iron-base particle 10 Can be manufactured.

  Specifically, the step of forming the coating is performed, for example, after the iron-based particle preparation step (S10). The film 40 made of an inorganic compound containing an oxygen atom can be formed by, for example, chemical conversion treatment, solvent spraying or a sol-gel method using a precursor.

  When the powder for compacting produced in this way is molded with a mold to obtain a molded body of a predetermined shape, even if the shape of the mold is complicated, it adheres to the recesses of the iron base particles 10. 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 has filled the recessed part of the iron base particle 10 with 80% or more of the lubricant 20, 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 iron-base particles 10 and the lubricant 20 attached to the surface of the iron-base particles 10 are provided. 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 The average value of the ratio G of the lubricant 20 existing outside the convex hull 30 of the iron-based particles 10 in the lubricant 20 is 20% or less. By setting the average value of F to 2 or more, irregularities can be provided on the surface of the iron base particles 10. By setting F to 20 or less, filling becomes possible at high density. Further, since the average value of the ratio G of the lubricant 20 existing outside the convex hull 30 is set to 20% or less, the lubricant 20 adheres to the concave portion of the iron base particle 10 and lubricates outside the convex hull 30. There is not much agent 20 present. For this reason, the powder molding particles 1 can be prevented from aggregating with each other, so that fluidity is not hindered. Therefore, the powder for compacting which has favorable fluidity | liquidity, can be filled with high density, and becomes a high-density molded object when compacted is formed.

Moreover, the manufacturing method of the powder for compacting in the embodiment of the present invention includes 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 ], an iron base particle preparation step (S10) for preparing iron base particles 10 having an average value of F represented by F = (B × V × ρ) / S of 2 or more and 20 or less, A lubricant preparation step (S20) for preparing the lubricant 20 and an adhesion step (S30) for heating the iron base particles 10 and the lubricant 20 by heating at a temperature equal to or higher than the melting point of the lubricant 20 are provided. Thereby, the iron base particle 10 in which moderate unevenness | corrugation is formed in the surface can be prepared in the iron base particle preparation step (S10), and the lubricant 20 is attached to the concave portion of the iron base particle 10 in the attachment step (S30). . Therefore, it is possible to produce a powder for compacting that can be molded at a high density without impeding the fluidity during molding.

[Example]
In this example, the effect of setting F to 2 to 20 and the ratio G to 20% or less was examined. First, the powders for compacting in Examples and Comparative Examples were produced by the following method based on Table 1 below.

(Powder for compacting of Examples 1 to 17)
In Examples 1-17, the powder for compacting was manufactured using the manufacturing method of embodiment shown in FIG. Specifically, in the iron-based particle preparation step (S10), iron-based particles containing pure iron and the remainder consisting of inevitable impurities and having the equivalent circle diameter and BET values shown in Table 1 were produced by the water atomization method. . The average value of F of each iron-based particle was as shown in Table 1.

  Next, about Examples 1-15, the process of forming a film on the surface of an iron base particle was implemented. As the coating, iron phosphate was formed to a thickness of 25 nm.

  Next, in the lubricant preparation step (S20), lubricants as shown in Table 1 were prepared. Table 1 shows the melting point, acid value, sum of hydroxyl value and amine value, and the amount of each lubricant. In Table 1, the unit of the acid value, the sum of the hydroxyl value and the amine value is mgKOH / g.

  Next, in the attaching step (S30), the lubricant was attached to the iron-based particles by heating at the temperatures shown in Table 1, respectively. Table 1 shows the viscosity of the lubricant at the heated temperature. Moreover, the average value of the ratio G after the adhesion step (S30) was as shown in Table 1. In Table 1, the viscosity indicates a value at a heated temperature, and the unit is [mPa · s].

  Next, the classification process (S40) was performed for a part of Examples 1 to 17, and the granulation process (S50) was performed for Examples 1, 9 to 11, 16, and 17. About the Example which implemented the granulation process (S50), the average value of the ratio G after a granulation process (S50) is shown in Table 1. The above process (S10-S50) was implemented and the powder for compacting shaping | molding of Examples 1-17 was manufactured.

(Production of powder for compacting in Comparative Examples 1 to 5)
Comparative Examples 1 to 5 basically have the same configuration as that of Examples 1 to 15, but Comparative Example 1 has an average value of F of 1, Comparative Example 2 has an average value of F of 26, and Comparative Example 3 has The average value of the ratio G is 24%, the comparative example 4 is different in that the average value of the ratio G is 34%, and the comparative example 5 is manufactured so that the average value of the ratio G is a numerical value% exceeding 100%. In addition, the process of forming a film was implemented about Comparative Examples 1-5, and the granulation process (S50) was implemented about Comparative Example 1 and Comparative Example 4.

(Evaluation methods)
About the obtained powder for compacting, the flow time (FR value) and the apparent density (AD value) were measured. 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, the pressure of 10 [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. 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.

  As shown in Table 2, for Examples 1 to 17 within the scope of the present invention in which the average value of F is in the range of 2 to 20 and the average value of G is 20% or less, fluidity and apparent density And the compact density were excellent.

  On the other hand, about Comparative Examples 1 and 3-5, it was worse than Examples 1-17 about fluidity | liquidity, an apparent density, and a molded object density. In Comparative Example 2, the fluidity and the apparent density were good, but the compact density was bad.

  As described above, according to the examples, by setting the average value of F to 2 to 20 and the average value of the ratio G within 20%, all of fluidity, apparent density, and compact density are excellent. It was confirmed that 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. (A) is an enlarged view schematically showing one particle (powder molding particle) constituting the powder for powder molding in the embodiment of the present invention, and (B) is an embodiment of the present invention. It is an enlarged view which shows typically 1 particle | grains of the powder for compacting molding provided with the film in a form. It is a flowchart which shows the manufacturing method of the powder for compacting shaping | molding in embodiment of this invention. It is a figure explaining the classification process in embodiment of this invention, (A) is a schematic diagram which shows the relationship between the particle size and frequency in a classification process, (B) is a schematic diagram which shows the state made into secondary particle | grains It is. 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.

Explanation of symbols

  1 Particles for compaction molding, 10 Iron-based particles, 20 Lubricant, 30 Convex hull, 40 Coating.

Claims (10)

Iron-based particles,
A lubricant that adheres to the surface of the iron-based particles,
The iron-based particles have 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 ], F = (B × The average value of F represented by V × ρ) / S is 2 or more and 20 or less,
The powder for compacting | molding whose average value of the ratio of the said lubricant which exists in the said lubricant outside the convex hull of the said iron group particle | grains is 20% or less.   The powder for compacting molding according to claim 1, wherein the lubricant is contained in an amount of 0.05 wt% to 0.4 wt% with respect to the iron-based particles.   3. The powder for compacting according to claim 1, wherein the lubricant has a viscosity at a temperature of 5 ° C. higher than the melting point of 30 [mPa · s] or less. The lubricant has at least one of an ester bond and an amide bond,
The powder for compacting | molding in any one of Claims 1-3 whose acid value is 1 [mgKOH / g] or less and whose sum of a hydroxyl value and an amine value is 4 [mgKOH / g] or less.   The powder for compacting | molding in any one of Claims 1-4 further equipped with the film which consists of an inorganic compound containing an oxygen atom on the surface of the said iron-base particle. 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 An iron-based particle preparation step of preparing iron-based particles having an average value of F represented by
A lubricant preparation step for preparing a lubricant;
A method for producing a powder for compacting, comprising: an adhesion step in which the iron-based particles and the lubricant are adhered by heating at a temperature equal to or higher than the melting point of the lubricant.   The method for producing a powder for compacting according to claim 6, wherein in the lubricant preparation step, 0.05 to 0.4 wt% of the lubricant is prepared with respect to the iron-based particles.   The method for producing a powder for compacting molding according to claim 6 or 7, wherein in the lubricant preparation step, the lubricant having an average particle diameter of 1 mm or less is prepared. After the adhering step, an average value of the ratio of the lubricant present outside the convex hull of the iron-based particles is measured to determine whether the measured average value of the ratio is within 20%. A classification process;
Further comprising a pulverization step of pulverizing particles aggregated by the lubricant present outside the convex hull when it is determined that the average value of the ratio exceeds 20% in the classification step. Item 9. A method for producing a powder for compacting according to any one of Items 6 to 8.   The manufacturing method of the powder for powder compacting | molding in any one of Claims 6-9 further equipped with the process of forming the film which consists of an inorganic compound containing an oxygen atom on the surface of the said iron-base particle.

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