EP1118404A1 - Legierungspulver, gesinterte legierungspellets und verfahren zu deren herstellung - Google Patents

Legierungspulver, gesinterte legierungspellets und verfahren zu deren herstellung Download PDF

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Publication number
EP1118404A1
EP1118404A1 EP99943375A EP99943375A EP1118404A1 EP 1118404 A1 EP1118404 A1 EP 1118404A1 EP 99943375 A EP99943375 A EP 99943375A EP 99943375 A EP99943375 A EP 99943375A EP 1118404 A1 EP1118404 A1 EP 1118404A1
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Prior art keywords
powder particles
powder
alloy powder
particles
iron
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EP99943375A
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English (en)
French (fr)
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EP1118404A4 (de
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Katsuyoshi Kondoh
Ai Ito
Takatoshi Takikawa
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Sumitomo Electric Industries Ltd
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Sumitomo Electric Industries Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/06—Metallic powder characterised by the shape of the particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/14—Treatment of metallic powder
    • B22F1/148—Agglomerating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

  • the present inventors have invented an aluminum alloy powder having excellent fluidity and fillability and the method of producing such an aluminum alloy powder as a result of various experiments and consideration. First, the configuration will be illustrated below.
  • the aluminum alloy powder according to the first aspect of the present invention is an aluminum alloy powder formed of secondary powder particles produced by binding together using a binder primary powder particles whose main component is aluminum.
  • the aluminum alloy powder according to the second aspect of the present invention is an aluminum alloy powder formed of secondary powder particles produced by binding together primary powder particles whose main component is aluminum, where the secondary powder particles are aluminum alloy powder particles whose average value of the acicular ratio derived from the following equation is 2.0 or below, where a projected image is obtained by projecting upon a secondary powder particle:
  • Acicular ratio maximum diameter in a projected image of one particle / a diameter of projected image in a direction orthogonal to maximum diameter.
  • primary powder particles are rapidly solidified powder particles obtained by an atomization method.
  • the particle diameter of a secondary powder particle is between 10 ⁇ m and 500 ⁇ m.
  • the particle diameter of a primary powder particle is between 5 ⁇ m and 300 ⁇ m.
  • the secondary powder particles having a particle diameter of at least 50 ⁇ m are preferably 25 percent by weight or below of the entire secondary powder particles.
  • the fluidity of secondary powder particles measured using a funnel-like orifice tube having a bore diameter of 2.6 mm ⁇ based on the Test of Determination of Flow Rate of a Metal Powder according to the Japanese Industrial Standards (JIS Z 2502) is preferably 4.0 seconds/cm 3 or below.
  • the fluidity of secondary powder particles measured using a funnel-like orifice tube having a bore diameter of 4.0 mm ⁇ based on the Test of Determination of Flow Rate of a Metal Powder according to the Japanese Industrial Standards (JIS Z 2502) is preferably 2.5 seconds/cm 3 or below.
  • the apparent density of secondary powder particles measured based on the Method of Determination of Apparent Density of a Metal Powder according to the Japanese Industrial Standards (JIS Z 2504) is preferably between 80% and 100% of the tap density of the secondary powder particles measured based on the Method for determination of tap density of metal powders according to Japan Powder Metallurgy Association (JPMA P 08).
  • the average value of circularity derived from the following equation is 0.6 or greater, where the projected image is obtained by projecting upon a secondary powder particle:
  • Acicular ratio maximum diameter in projected image of one particle / diameter of projected image in a direction orthogonal to maximum diameter.
  • the binder is preferably an organic binder.
  • the amount of the organic binder in the secondary powder particles is preferably between 0.05 and 0.5 percent by weight.
  • the decomposition temperature of the organic binder preferably is at most 400°C.
  • the method of producing an aluminum alloy powder according to the third aspect of the present invention includes a granulation step and a drying step.
  • a granulation step primary powder particles having a particle diameter of 5 ⁇ m to 300 ⁇ m whose main component is aluminum are bound together using an aqueous organic binder solution to form secondary powder particles.
  • the drying step the moisture contained in the secondary powder particles is removed.
  • the secondary powder particles are formed, first, by allowing primary powder particles to be suspended within a fluidized bed, and by spraying an aqueous organic binder solution onto the primary powder particles to bind them together, and thereafter removing the moisture by drying.
  • the specific surface area of a secondary particle powder becomes large so that oxidation during sintering progresses significantly, inhibiting the sinterability between the secondary powder particles.
  • a specific surface area refers to the sum of the surface areas of all powder particles contained within the powder of a unit quantity (volume).
  • the particle diameter of a primary powder particle exceeds 300 ⁇ m
  • the particle diameter of the secondary powder particle exceeds 500 ⁇ m or 1 mm so that coarse secondary powder particles are formed, which also degrades the fluidity and fillability of secondary powder particles.
  • the particle diameter of the primary powder particles of aluminum alloy which are the starting raw material powder particles is desirably between 5 ⁇ m and 300 ⁇ m, and the particle diameter of 40 ⁇ m to 200 ⁇ m is more preferable from the viewpoint of the ease of handling, efficient economy, and so on, of the primary powder particles.
  • the particle diameter of a secondary powder particle is desirably between 10 ⁇ m and 500 ⁇ m. More preferably, the particle diameter of the secondary powder particle is between 60 ⁇ m and 250 ⁇ m in order to suppress the wedging of the particles into a gap of the die cavity and to stabilize the fluidity and the fillability of the secondary powder particles.
  • the content of secondary powder particles having a particle diameter of 50 ⁇ m or below in the entire secondary powder particles is 25 percent by weight or below.
  • the fluidity of the secondary powder particles which is measured using a funnel-like orifice tube having a bore diameter of 2.6 mm ⁇ based on the method of measuring the fluidity defined by the Test of Determination of Flow Rate of a Metal Powder according to the Japanese Industrial Standards (JIS Z 2502 (established in 1958, revised in 1979)), exceeds 4.0 seconds/cm 3 so that sufficient fluidity cannot be obtained.
  • the secondary powder particles cannot be filled uniformly with high speed so that it becomes difficult to produce a green compact having uniform density distribution.
  • the fluidity of the secondary powder particles is 2.5 seconds/cm 3 , which satisfies the appropriate range defined by the present invention.
  • the present inventors have discovered for the first time that the secondary powder particles that satisfy such fluidity requirement prove effective in economically producing a green compact for a complex-shaped part that requires high dimensional accuracy.
  • the fluidity of the secondary powder particles measured using a funnel-like orifice tube having a bore diameter of 2.6 mm ⁇ exceeds 4.0 seconds/cm 3
  • the time required for the secondary powder particles to be filled uniformly into a die cavity becomes long so that the productivity is significantly degraded.
  • the fluidity of the secondary powder particles measured using a funnel-like orifice tube having a bore diameter of 4.0 mm ⁇ is desirably 2.0 seconds/cm 3 or below.
  • the apparent density (AD) of the secondary powder particles measured based on the Method of Determination of Apparent Density of a Metal Powder according to the Japanese Industrial Standards (JIS Z 2504 (established in 1960, revised in 1979)) is from 80% to 100% of the tap density (TD) of the secondary powder particles measured based on the Method for determination of tap density of metal powders according to Japan Powder Metallurgy Association (JPMA P 08-1992).
  • the average value of circularity derived from equation (1) below is 0.6 or greater, where S represents the area per particle, and GL represents the length of the outer periphery of the projected image of one particle.
  • the circularity and the acicular ratio defined by equations (1) and (2) both become indices representing the sphericity of the secondary powder particles.
  • the greater the circularity and the smaller the acicular ratio it must be at least 1.0, however, the shape of a secondary powder particle becomes closer to a sphere so that the fluidity of the secondary powder particles improves as a result.
  • the secondary powder particles When the secondary powder particles have a circularity that is less than 0.6 or an acicular ratio that exceeds 2.0, the secondary powder particles no longer satisfy the fluidity defined by the present invention. Further, as described above, for the fluidity of the secondary powder particles measured using a funnel-like orifice tube having a bore diameter of 4.0 mm ⁇ to be 2.0 seconds/cm 3 or below, it is preferred that the average value of the circularity is at least 0.8 and that the average value of the acicular ratio is at most 1.5. In addition, for the purpose of comparison, conventional secondary powder particles shown in Fig. 11 have an acicular ratio of approximately 5 to 10.
  • secondary powder particles 1 is formed by allowing primary powder particles 2 to be suspended within a fluidized bed 4 using a gas 5 such as nitrogen, and at the same time, by spraying an aqueous organic binder solution 7 from a nozzle 6 onto the suspended primary powder particles, thereby binding together primary powder particles 2.
  • a gas 5 such as nitrogen
  • the amount of the organic binder contained in the secondary powder particles is between 0.05 and 0.5 percent by weight of the weight of the secondary powder particles.
  • the present inventors have discovered that the use, as a binder, of an organic binder was effective that has a strong binding force, that allows the produced secondary powder particles to have a spherical shape, and that has such a characteristic as becoming decomposed in a heating process so that it does not remain in the sintered body when a green compact is sintered.
  • an aqueous binder solution is used in which water and not an alcohol-based organic solvent is used as a solvent for the binder.
  • the amount of the organic binder within the produced secondary powder particles is desirably between 0.05 and 0.5 percent by weight of the entire secondary powder particles.
  • the amount of the organic binder is less than 0.05 percent by weight, the primary powder particles are not sufficiently bound together, leaving behind fine-grained primary powder particles so that the fluidity of the secondary powder particles cannot be improved sufficiently.
  • the amount of the organic binder exceeding 0.5 percent by weight does not further improve the fluidity of the secondary powder particles, but instead, the secondary powder particles are further bound together to form coarser-grained powder whose particle diameter exceeds 500 ⁇ m such that the fluidity of the secondary powder particles is degraded.
  • the longer time required to remove the organic binder within the secondary powder particles by thermal decomposition leads to inefficient economy.
  • the amount of the organic binder within the secondary powder particles according to the present invention is desirably between 0.05 and 0.5 percent by weight of the entire secondary powder particles, and more preferably, is between 0.15 and 0.4 percent by weight if the balance between the improvement in the fluidity of the secondary powder particles and the reduction of time required for organic binder removal is to be considered.
  • a preliminary heating step (binder removal step) in a temperature zone that is lower than the sintering temperatures is required before sintering a green compact.
  • the reduction in the processing time of this step significantly contributes to the improvement of economy.
  • the decomposition temperature of the organic binder contained in the secondary powder particles according to the present invention is desirably 400°C or below.
  • Organic binders that satisfy the above-described characteristics and dissolve in water include polyvinyl alcohol (PVA), polyvinyl methyl ether (PVME), carboxymethylcellulose (CMC), hydroxyethyl cellulose (HEC) and the like.
  • PVA polyvinyl alcohol
  • PVME polyvinyl methyl ether
  • CMC carboxymethylcellulose
  • HEC hydroxyethyl cellulose
  • PVIE polyvinyl butyral
  • PVIE polyvinyl isobutyl ether
  • These resins either dissolve only in an alcohol-based organic solvent and not in water or do not readily dissolve in water so that they are not desirable for application to the production method according to the present invention.
  • the method of producing an aluminum alloy powder according to the present invention allows the production of the desirable secondary powder particles described above by repeating a granulation step and a drying step, where the granulation step involves, as shown in Fig. 4, first allowing primary powder particles 2 whose main component is aluminum and whose particle diameter is from 5 ⁇ m to 300 ⁇ m already described as starting raw material powder particles to be suspended within fluidized bed 4, and then spraying the previously described aqueous organic binder solution 7 onto the suspended primary powder particles 2 to bind primary powder particles 2 together to produce secondary powder particles 1, and the drying step involves removing the moisture of aqueous binder solution 7 contained within secondary powder particles 1.
  • the present inventors have discovered that it was effective to allow primary powder particles 2 to be suspended within fluidized bed 4 by allowing air or nitrogen gas 5 to flow in from the lower portion of fluidized bed 4, and spraying aqueous organic binder solution 7 onto the suspended primary powder particles 2 from an upper portion of fluidized bed 4 as shown in Fig. 4 when an organic binder is sprayed in the form of a mist.
  • aqueous organic binder solution 7 onto the suspended primary powder particles 2 from an upper portion of fluidized bed 4 as shown in Fig. 4 when an organic binder is sprayed in the form of a mist.
  • the temperature within the fluidized bed is between 60°C and 120°C, and more preferably, is between 70°C and 90°C. It is necessary to control the temperatures of the air or the nitrogen gas that flows within the fluidized bed in order to remove the moisture within the aqueous organic binder solution contained in the secondary particle powder.
  • the drying step to remove the moisture within the secondary powder particles and the secondary powder particles themselves would take a long time, resulting in inefficient economy.
  • the moisture would remain in the secondary particle powder for a long time in a high temperature so that the secondary powder particles would be oxidized.
  • the secondary powder particles would be oxidized if the secondary powder particles are stored with some moisture remaining in the secondary particle powder.
  • the temperature within the fluidized bed exceeds 120°C
  • no significant drying effect is observed, while a problem arises relating to the ease of handling when the secondary powder particles are taken out after drying.
  • the temperature of an inflow gas exceeds 120°C
  • the moisture would evaporate from the aqueous organic binder solution when the solution is being sprayed from a spray, and the organic binder would solidify and be fixed at the tip of the spray nozzle, clogging the nozzle so that the organic binder can no longer be sprayed evenly.
  • the temperature within the fluidized bed is more preferably between 70°C and 90°C in order to achieve a good drying efficiency and to facilitate taking out of the secondary powder particles after drying.
  • the concentration of the aqueous organic binder solution is desirably between 1% and 8%.
  • concentration of the aqueous organic binder solution is less than 1%, sufficient binding force cannot be obtained so that it becomes difficult to produce the prescribed secondary powder particles defined by the present invention.
  • the present inventors have invented an iron alloy powder having excellent fluidity and a method of producing a sintered iron alloy compact having high dimensional accuracy as a result of various experiments and considerations.
  • the configuration will be illustrated below.
  • the iron alloy powder according to the fourth aspect of the present invention is an iron alloy powder formed of secondary powder particles produced by binding together using a binder iron-based primary powder particles whose main component is iron or, by binding together using a binder iron-based primary powder particles whose main component is iron along with primary powder particles of a non-ferrous component.
  • the mean particle diameter of iron-based primary powder particles is between 20 ⁇ m and 100 ⁇ m, while the mean particle diameter of secondary powder particles is between 50 ⁇ m and 200 ⁇ m.
  • the secondary powder particles having a particle diameter that is 45 ⁇ m or below are at most 10 percent by weight of the entire secondary powder particles.
  • the value of the surface area of a secondary particle powder derived from the BET (Brunauer-Emmett-Teller) isothermal adsorption formula is 0.08 m 2 /g or below.
  • a surface of a secondary powder particle is covered with a binder.
  • the organic binder includes as the main component any one organic compound selected from the group consisting of polyvinyl alcohol, polyvinyl ether, polyethylene oxide, methyl cellulose and carboxymethylcellulose.
  • an iron alloy powder is inserted between the fixed plate and the movable plate, a pressure is applied from above the iron alloy powder to form an iron alloy powder bed having a porosity that is between 0.5 and 0.7, and the movable plate is pulled parallel to the fixed plate under a prescribed load to cause the iron alloy powder to be sheared, at which point the shear stress is derived, and the unconfined yield stress derived from the powder yield locus indicating the relation between the load and the shear stress is at most 300 Pa.
  • a step of adding a lubricant to the secondary powder particles is included between a granulation step for forming the secondary powder particles and a step of compaction.
  • iron alloy powder normally, particles of nickel (Ni), copper (Cu), carbon (C) or the like are added besides the iron powder which is the main component, and a solid lubricant such as zinc stearate or wax or the like is added in order to prevent the alloy powder from galling to a die cavity during compaction.
  • a solid lubricant such as zinc stearate or wax or the like is added in order to prevent the alloy powder from galling to a die cavity during compaction.
  • the tensile strength (breaking force) of a powder bed was measured using a horizontal splitting cell for tensile strength measurement 21 (a powder bed tester produced by Sankyo Piotech Co. Ltd.) formed by a movable cell 22 and a fixed cell 23.
  • the powder bed whose porosity was adjusted to 0.5 to 0.7 by a pre-compression load was inserted between the fixed plate and the movable plate. While a load a was exerted from above onto the movable plate, a shearing force was applied to the movable plate parallel to the fixed plate. Then, the shearing force ⁇ was derived at the time at which sliding occurred in the powder bed and the powder bed collapsed. The respective shearing forces ⁇ were derived using three different loads.
  • a value ⁇ 1 of the stress at the point of intersection of the ⁇ axis and a Mohr's stress circle B being in contact with a point E in the powder yield locus was derived.
  • This stress ⁇ 1 is specifically referred to as a major consolidating stress or a major compression stress.
  • the point E in the powder yield locus was the point at which the shear fracture occurred to the powder bed with no change in the porosity of the powder bed.
  • a value was derived by dividing the value of major consolidating stress ⁇ 1 by the value of unconfined yield stress F c .
  • This value is in general referred to as a flow function. It is known that the fluidity of a powder is high when the value of the flow function is greater than 10.
  • the amount of organic binder within the secondary powder particles is desirably in the range of 0.05 to 5 percent by weight.
  • the amount of organic binder is less than 0.05 percent by weight, sufficient granulation of the secondary powder particles does not take place so that many fine primary powder particles remain. Consequently, the fluidity of the secondary powder particles does not improve as much as the primary powder particles. Moreover, due to the weak binding force of the secondary powder particles, the secondary powder particles might break up when conveyed.
  • the amount of the organic binder exceeds 5 percent by weight, the component of the organic binder might remain even when heat treatment is performed to remove the organic binder after the green compact is formed.
  • carbon (C) existing in the organic binder, may cause voids to be generated in the sintered body, which reduces the mechanical strength of the sintered body.
  • the secondary powder particles may further be bound together to form coarse powder particles.
  • a coating film of organic binder is formed on a surface of a secondary powder particle.
  • a desirable organic binder is one the contains as a main component at least one or more kinds of organic compounds from polyvinyl alcohol, polyvinyl ether, polyethylene oxide, methyl cellulose, and carboxymethylcellulose. These organic binders are water-soluble, have strong adhesion, and easily decompose at 500°C or below so that they are suitable for the granulation of the iron alloy powder formed of the present secondary powder particles.
  • secondary powder particles are produced by binding together using a binder iron-based primary powder particles whose main component is iron, or binding together using a binder iron-based primary powder particles whose main component is iron along with primary powder particles of a non-ferrous component.
  • a pressure is applied to the secondary powder particles to form a green compact, and the dimension of one green compact particularly in a direction of compression is measured in four locations.
  • the green compact is sintered to form a sintered body. The dimension of the produced sintered body is measured in the corresponding four locations.
  • the value is 1.3 or below obtained by dividing the value that is six times the standard deviation value of the dimension of the sintered body by the value that is six times the standard deviation value of the dimension of the green compact.
  • the present secondary powder particles having high fluidity are uniformly filled into a die cavity such that the density dispersion within the green compact and the density variation among the green compacts are significantly reduced.
  • the shrinkage behavior becomes substantially the same due to the small density dispersion, and thus the density dispersion within a sintered body and the density variation among the sintered bodies are reduced.
  • the value becomes 1.3 or below which is derived by dividing the value that is six times the standard deviation value of a prescribed dimension of a sintered body by the value that is six times the standard derivation value of a prescribed dimension of a green compact.
  • solid lubricants such as zinc stearate and wax added to prevent the galling to the die cavity are known normally to degrade the fluidity of a powder.
  • the present inventors have invented a metal powder having high fluidity and a sintered metal compact having a high dimensional accuracy.
  • the configuration will be illustrated below.
  • a metal powder according to the fifth aspect of the present invention is formed of secondary powder particles produced by binding together using a binder primary powder particles whose main component is metal.
  • the binder is an organic binder.
  • a sintered metal compact according to the sixth aspect of the present invention is obtained by sintering a green compact formed of secondary powder particles produced by binding together using a binder primary powder particles whose main component is metal.
  • Fig. 1 is a schematic diagram of a cross sectional structure of a secondary powder particle according to an embodiment of the present invention.
  • Fig. 2 is a diagram illustrating the circularity of a secondary powder particle according to an embodiment of the present invention.
  • Fig. 4 is a diagram showing a process of producing secondary powder particles according to an embodiment of the present invention.
  • Fig. 5 is a cross sectional view showing how secondary powder particles according to an embodiment of the present invention are filled into a die cavity.
  • Fig. 6 is a scanning electron micrograph showing the appearance of secondary powder particles according to the eighth embodiment of the present invention.
  • Fig. 7 is a scanning electron micrograph showing the appearance of one secondary powder particle for comparison in the same embodiment.
  • Fig. 8 is a scanning electron micrograph showing the appearance of another secondary powder particle for comparison in the same embodiment.
  • Fig. 12 is a scanning electron micrograph showing the appearance of secondary powder particles according to the thirteenth embodiment of the present invention.
  • Fig. 13 is a scanning electron micrograph showing the appearance of secondary powder particles for comparison in the same embodiment.
  • Fig. 14 is a scanning electron micrograph showing the appearance of other secondary powder particles for comparison in the same embodiment.
  • Fig. 16 is a diagram illustrating the steps of producing conventional secondary powder particles of aluminum.
  • Fig. 17 is a schematic diagram showing a cross sectional structure of a conventional secondary powder particle.
  • the temperature within the fluidized bed was set at 75°C.
  • the spraying time for the PVA solution as a binder was set to 15 minutes, and the drying time was set to 10 minutes.
  • Other conditions also satisfied the appropriate range defined by the present invention in forming the secondary powder particles.
  • the fluidity and the oxygen content of the secondary powder particles obtained were measured and analyzed.
  • the fluidity of the secondary powder particles was determined by employing, as an evaluation index of fluidity, the value derived by first measuring the time required for 25 grams of secondary powder particles to complete their flow using one of a funnel-like orifice tube having a bore diameter of 2.6 mm ⁇ and a funnel-like orifice tube having a bore diameter of 4.0 mm ⁇ based on the method for measuring fluidity defined by Test of Determination of Flow Rate of a Metal Powder according to the Japanese Industrial Standards (JIS Z 2502), then taking this value and dividing this value by the volume of secondary powder particles corresponding to 25 grams of secondary powder particles, the volume being converted by an apparent density (AD) of secondary powder particles measured based on Method of Determination of Apparent Density of a Metal Powder according to the Japanese Industrial Standards (JIS Z 2504).
  • AD apparent density
  • a particle diameter of primary powder particles was less than 5 ⁇ m so that significant oxidation occurred during the granulation and drying steps, and the secondary powder particles obtained failed to show fluidity in the fluidity measurement using a funnel-like orifice tube having a bore diameter of 2.6 mm ⁇ . Moreover, in the fluidity measurement using a funnel-like orifice tube having a bore diameter of 4.0 mm ⁇ , it was found that the secondary powder particles obtained failed to satisfy the appropriate range defined by the present invention.
  • a content (based on weight) of secondary powder particles whose particle diameter is 50 ⁇ m or below is also shown in Table 2.
  • the fluidity of secondary powder particles the time required for 25 grams of secondary powder particles to complete their flowing was measured using each of a funnel-like orifice tube having a bore. diameter of 2.6 mm ⁇ and a funnel-like orifice tube having a bore diameter of 4.0 mm ⁇ based on Japanese Industrial Standards mentioned earlier, and at the same time, this value was divided by the volume of secondary powder particles corresponding to 25 grams of secondary powder particles, the volume being converted by an apparent density (AD) of secondary powder particles measured based on the above-mentioned Japanese Industrial Standards, to produce a value employed as an evaluation index of fluidity.
  • AD apparent density
  • the comparative examples nos. 7 to 9 not satisfying the appropriate range defined by the present invention involved the following problems.
  • the content of powder whose secondary powder particle diameter was 50 ⁇ m or below exceeded 25 percent by weight such that the secondary powder particles lacked good fluidity.
  • a primary particle powder having a minimum particle diameter of 8 ⁇ m, a maximum particle diameter of 150 ⁇ m, and a mean particle diameter of 46 ⁇ m obtained by the atomization method was employed as the starting raw material powder.
  • secondary powder particles having a shape (circularity, acicular ratio) shown in Table 3 were formed using a tumble-type fluidized bed granulator by variously changing the added amount of an aqueous PVA solution binder (2% concentration) which was sprayed onto the primary powder particles.
  • fluidity of the secondary powder particles With regard to fluidity of the secondary powder particles, the time required for 25 grams of secondary powder particles to complete their flowing was measured using each of a funnel-like orifice tube having a bore diameter of 2.6 mm ⁇ and a funnel-like orifice tube having a bore diameter of 4.0 mm ⁇ based on the above-mentioned Japanese Industrial Standards, and at the same time, this value was divided by the volume of secondary powder particles corresponding to 25 grams of secondary powder particles, the volume being converted by an apparent density (AD) of secondary powder particles measured based on the above-mentioned Japanese Industrial Standards, to produce a value employed as an evaluation index of fluidity.
  • AD apparent density
  • Circularity 4 ⁇ ⁇ (area of projected image of one particle) / (length of outer periphery of projected image of one particle) 2
  • Acicular ratio maximum diameter in projected image of one particle / diameter of projected image in a direction crossing maximum diameter
  • Fluidity sec./cm 3 ) . ⁇ 2.6mm ⁇ 4.0mm 1 0.68 1.87 3.8 2.3 2 0.77 1.62 3.6 2.2 3 0.92 1.44 3.1 1.8 4 0.96 1.18 2.7 1.4 5 0.52 1.94 No flow 2.8 6 0.63 2.24 No flow 2.9 7 0.44 2.48 No flow No flow 8 0.41 2.70 No flow No flow Present inventive examples; 1 ⁇ 4 Comparative examples; 5 ⁇ 8
  • present inventive examples nos. 1 to 4 secondary powder particles having an appropriate shape (circularity, acicular ratio) defined by the present invention were found to have good fluidity.
  • the circularity was 0.8 or above and the acicular ratio was 1.5 or below so that the secondary powder particles were found to have even better fluidity when compared with other examples.
  • the comparative examples nos. 5 to 8 not satisfying the appropriate range defined by the present invention involved the following problems.
  • the circularity of secondary powder particles was less than 0.6 so that the secondary powder particles lacked good fluidity.
  • the acicular ratio of secondary powder particles exceeded 2.0 such that the secondary powder particles lacked good fluidity.
  • a primary particle powder of aluminum alloy having an appropriate particle diameter defined by the present invention (a minimum particle diameter of 6 ⁇ m, a maximum particle diameter of 215 ⁇ m, and a mean particle diameter of 65 ⁇ m) obtained by the atomization method was employed as the starting raw material powder.
  • an aqueous organic binder solution (binder concentration of 2%) was sprayed onto the primary powder particles to bind together the primary powder particles and secondary powder particles having a particle diameter shown in Fig. 4 were formed.
  • the amount of binder to be sprayed onto the primary powder particles was variously changed in forming the secondary powder particles.
  • the evaluated results of the content of the binder within the secondary powder particles obtained, of the particle diameter, and of fluidity are shown in Table 4.
  • the fluidity of the secondary powder particles the time required for 25 grams of secondary powder particles to complete their flowing was measured using each of a funnel-like orifice tube having a bore diameter of 2.6 mm ⁇ and a funnel-like orifice tube having a bore diameter of 4.0 mm ⁇ based on the above-mentioned Japanese Industrial Standards, and at the same time, this value was divided by the volume of secondary powder particles corresponding to 25 grams of secondary powder particles, the volume being converted by an apparent density (AD) of secondary powder particles measured based on the above-mentioned Japanese Industrial Standards, to produce a value employed as an evaluation index of fluidity.
  • AD apparent density
  • secondary powder particles that were formed using an aqueous solution binder defined by the present invention contained appropriate amount of binder so that the secondary powder particles were found to have good fluidity.
  • comparative examples nos. 9 to 13 not satisfying the appropriate range defined by the present invention involved the following problems.
  • the content of the binder was as low as 0.015 percent by weight so that the content of powder whose particle diameter was 50 ⁇ m or below exceeded 25%, resulting in poor fluidity of the secondary powder particles.
  • the content of the binder was as low as 0.030 percent by weight so that the particle diameter became less than 10 ⁇ m, resulting in poor fluidity of the secondary powder particles.
  • a primary particle powder of aluminum alloy having an appropriate particle diameter defined by the present invention (a minimum particle diameter of 7 ⁇ m, a maximum particle diameter of 148 ⁇ m, and a mean particle diameter of 37 ⁇ m) obtained by the atomization method was employed as the starting raw material powder.
  • an organic binder having a decomposition temperature as shown in Table 5 was diluted with distilled water to prepare an aqueous organic binder solution having a concentration of 3%.
  • the starting raw material powder particles were suspended within a tumble-type fluidized bed granulator (held at a temperature between 70°C and 80°C), and the binder was sprayed from above so as to bind together a plurality of primary powder particles to form secondary powder particles.
  • the secondary powder particles obtained were compacted and solidified at surface pressure area of 7t/cm 2 , and thereafter, was heated for one hour in an nitrogen gas atmosphere controlled to be at 400°C in an attempt to remove the binder within the green compact. Then, from this sample, a transverse test piece was formed and its flexural strength was measured. Table 5 also shows the content of a binder within secondary powder particles, the amount of the binder within a green compact after heating, and the results of flexural strength measurement. No.
  • a primary particle powder of aluminum alloy having an appropriate particle diameter defined by the present invention (a minimum particle diameter of 7 ⁇ m, a maximum particle diameter of 146 ⁇ m, and a mean particle diameter of 41 ⁇ m) obtained by the atomization method was employed as the starting raw material powder.
  • a nitrogen gas was allowed to flow in at a flow rate of 50 liter/hour from the bottom of the granulator to keep the primary powder particles suspended within the granulator, and an aqueous PVA binder solution was sprayed from above with a spray to bind together the primary powder particles, thereby forming secondary powder particles.
  • comparative examples nos. 5 to 8 formed under manufacturing conditions not satisfying the appropriate range defined by the present invention involved the following problems.
  • the binder concentration was as low as 0.5 percent by weight so that the binding between primary powder particles did not progress sufficiently, and as a result, secondary powder particles having an appropriate particle diameter could not be produced.
  • the temperature within the fluidized bed was as low as 50°C so that the drying of the powder was insufficient, and the secondary powder particles were oxidized during the granulation and drying processes.
  • a primary particle powder of aluminum alloy having an appropriate particle diameter defined by the present invention (a minimum particle diameter of 6 ⁇ m, a maximum particle diameter of 98 ⁇ m, and a mean particle diameter of 34 ⁇ m) obtained by the atomization method was employed as the starting raw material powder.
  • air was allowed to flow in at a flow rate of 50 liter/hour from the bottom of the granulator to keep the primary powder particles suspended within the granulator, and an aqueous PVA binder solution was sprayed from an upper portion of the granulator with a spray to bind together the primary powder particles, thereby forming secondary powder particles.
  • secondary powder particles having apparent densities (AD) and tapped densities (TD) as those shown in Table 7 were formed by changing the concentration of an aqueous binder solution and the sprayed amounts thereof.
  • the AD value and the TD value were respectively measured based on a method described in the Method of Determination of Apparent Density of a Metal Powder (JIS Z 2504) according to the Japanese Industrial Standards and on a method described in the Method for determination of tap density of metal powders according to Japan Powder Metallurgy Association (JPMA P 08).
  • comparative example no. 7 in Table 7 is the starting raw material powder (primary powder particles).
  • the AD/TD value was as small as 75.0% so that it was found that the filling of secondary powder particles close to the tap density with five reciprocating passes or so of powder feed box was difficult, and that it required more time to feed the powder into the die cavity than in present inventive examples nos. 1 to 4. In addition, in this case, ten reciprocating passes of powder feed box could finally ensure the prescribed amount of powder filled.
  • the powder to be filled into the die cavity was a raw material powder having poor fluidity, and the AD/TD value was as small as 70.1% such that it was found that the filling of the powder close to the tap density with five reciprocating passes or so of powder feed box was difficult, and that it required ten reciprocating passes of powder feed box to ensure the prescribed amount of filled powder.
  • the secondary powder particles shown in Fig. 6 are those produced by spraying 150 grams of aqueous PVA solution having a concentration of 2% onto 1 kilogram of primary powder particles (amount of binder being 0.3 percent by weight). These secondary powder particles had a mean particle diameter of 221 ⁇ m, a maximum particle diameter of 340 ⁇ m, and a minimum particle diameter of 52 ⁇ m so that it was confirmed that the fluidity defined by the present invention was satisfied. Moreover, the secondary powder particles were all found to have a quasi-spherical shape.
  • An iron alloy powder (iron-based primary particle powder and primary particle powder of a non-ferrous component) having a mean particle diameter shown in Table 8 and obtained by the atomization method was prepared.
  • the iron alloy powder was filled into a tumble-type fluidized bed granulator. Air of a prescribed temperature was allowed to flow in from the bottom of the tumble-type fluidized bed granulator, and while the iron alloy powder particles were suspended within the fluidized bed, an aqueous polyvinyl alcohol (hereinafter referred to as PVA) solution having a concentration of 5% was sprayed from a nozzle attached to the upper portion.
  • PVA aqueous polyvinyl alcohol
  • the solid content of PVA was controlled to be 2 percent by weight of the iron alloy powder, and the temperature within the fluidized bed was held at about 60°C. After the spraying of PVA, drying was effected within the same fluidized bed for about 15 minutes or so to produce secondary powder particles.
  • the secondary powder particles obtained were filled into a powder feed box (shoe box) having a dimension of about 150 mm ⁇ 100 mm ⁇ 75 mm (height).
  • the powder feed box was moved back and forth or reciprocated in order to feed the secondary powder particles into a die cavity fill having an outside diameter of 45 mm ⁇ and an inside diameter of 35 mm ⁇ .
  • the number of reciprocating passes of the powder feed box was three.
  • the secondary powder particles, after being fed into the die cavity fill, were compacted to produce a green compact. Twenty green compacts were successively produced.
  • the thickness of a green compact in the direction of compression was measured in four locations per green compact.
  • the standard deviation was calculated from these measured values, and the value (6 ⁇ ) that was six times this standard deviation value ( ⁇ ) was taken as a dimensional accuracy.
  • the green compacts were treated by sintering to produce sintered bodies. Like the green compacts, each sintered body obtained was measured in four locations, and a dimensional accuracy 6 ⁇ was similarly calculated.
  • the fluidity of the secondary powder particles was evaluated using a powder bed tester produced by Sankyo Piotech Co. Ltd., as described above.
  • a flow function of the secondary powder particles was evaluated using a parallel plates cell for shear strength measurement. The procedure will be briefly described. A pre-compression load was applied in advance to a powder bed such that a prescribed porosity of 0.5 to 0.7 was achieved. Then, three levels of vertical loads were applied to the powder bed to perform a shear test.
  • the powder yield locus was derived by plotting on a graph a vertical load ( ⁇ ) and a shear stress ( ⁇ ) of the shear test (see Fig. 11).
  • a critical Mohr's stress circle A was derived that passes through the origin of the ⁇ - ⁇ coordinates and in contact with the powder yield locus.
  • the stress at the point of intersection of the critical Mohr's stress circle A and ⁇ axis, i. e. an unconfined yield stress F c was derived.
  • the stress at the point of intersection of the ⁇ axis and a Mohr's stress circle B in contact with a point E in the powder yield locus, i. e. a major compaction stress ⁇ 1 was derived.
  • Major compaction stress ⁇ 1 was divided by uniaxial fracture stress F c , producing a value that was the flow function (F.F) of the powder. The powder was determined to have high fluidity when this value was 10 or greater.
  • the weight proportion of particles having a particle diameter of 45 ⁇ m or smaller contained in the secondary powder particles was evaluated by a sieving method.
  • the mean particle diameter of secondary powder particles exceeding 200 ⁇ m is not desirable since the compactibility would be degraded.
  • the mean particle diameter of the secondary powder particles is preferably in the range of 50 ⁇ m to 200 ⁇ m.
  • iron-based primary powder particles include a high ratio of fine particles whose particle diameter is 45 ⁇ m or smaller, and also have a large specific surface area value so that the fluidity is seen to be low.
  • the cases of secondary powder particles having a mean particle diameter not in the appropriate range are shown in the comparative examples (nos. 11 and 12).
  • the secondary powder particles were produced using the same techniques as an inventive example (no. 1) except for the mean particle diameter of the iron-based primary powder particles.
  • the mean particle diameter of the iron-based primary powder particles was 18 ⁇ m
  • the mean particle diameter of the secondary powder particles obtained was 30 ⁇ m
  • the ratio of particles having a mean particle diameter of 45 ⁇ m or below was 70 percent by weight.
  • the flow function (F.F) was 3.4, indicating low fluidity.
  • Secondary powder particles were produced from iron-based primary powder particles by the procedure according to the ninth embodiment.
  • carbon (C) copper (Cu) powder, or as a solid lubricant, paraffin wax or zinc stearate powder, was added at a composition ratio shown in Table 9.
  • the secondary powder particles were mixed for about thirty minutes by a V-type mixer to form a mixed powder.
  • the mixed powder obtained was compacted to produce a green compact, which was then sintered to form a sintered body.
  • the prescribed dimensional accuracy of the green compact and of the sintered body, respectively, was evaluated using the procedure according to the ninth embodiment. Moreover, a flow function (F.F), a tensile strength, and an unconfined yield stress of the secondary powder particles were measured. The results are shown in Table 9.
  • the amount of PVA was varied in the range of 0.05 to 5 percent by weight on the weight of the secondary powder particles. It was discovered that the flow function (F.F) of the secondary powder particles exceeded 10 and the fluidity was good when the amount of PVA was within this range.
  • the variation in weight of the green compacts was found to be relatively smaller when employing a secondary particle powder and a mixed secondary particle powder.
  • the dimensional accuracy of the sintered body was found to increase when a secondary particle powder or a mixed secondary particle powder was used as opposed to the use of an iron-based primary particle powder or of a mixed iron-based primary particle powder.
  • the high fluidity of the secondary particle powder that allowed even filling of the secondary powder particles into a die cavity improved the dimensional accuracy of the sintered body.
  • the weight variation of the green compacts could be kept low in the case where a secondary particle powder was employed as the powder in comparison with the case where an iron-based primary particle powder was employed. It can be concluded that this is due to the fluidity of the secondary powder particles being higher than that of the iron-based primary powder particles.
  • the secondary powder particles shown in Fig. 12 are secondary powder particles with a PVA content of 1.0 percent by weight. It was found that these secondary powder particles satisfied the fluidity and the range of appropriate particle diameter defined by the present invention and that the desired dimensional accuracy improved of the sintered body obtained by compacting and sintering these secondary powder particles.
  • the secondary alloy powder particles of aluminum By employing the secondary alloy powder particles of aluminum according to the present invention, fluidity of and fillability into a die cavity of secondary powder particles are improved such that, for instance, an internal rotor set having an inner periphery portion or an outer periphery portion shaped like a tooth profile based on one of a trochoid curve, an involute curve, and a hypo-cycloid curve can be produced with high dimensional accuracy.
  • an internal rotor set having an inner periphery portion or an outer periphery portion shaped like a tooth profile based on one of a trochoid curve, an involute curve, and a hypo-cycloid curve can be produced with high dimensional accuracy.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Nanotechnology (AREA)
  • Powder Metallurgy (AREA)
  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
EP99943375A 1998-09-24 1999-09-16 Legierungspulver, gesinterte legierungspellets und verfahren zu deren herstellung Withdrawn EP1118404A4 (de)

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JP28889998 1998-09-24
JP28889998 1998-09-24
JP24360399 1999-08-30
JP11243603A JP2000160203A (ja) 1998-09-24 1999-08-30 合金粉末、合金焼結体およびそれらの製造方法
PCT/JP1999/005060 WO2000016937A1 (fr) 1998-09-24 1999-09-16 Alliage en poudre, alliage en pastilles frittees et procede de production

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US20100310199A1 (en) * 2008-02-21 2010-12-09 Ntn Corporation Sintered bearing
CN102189253A (zh) * 2010-03-11 2011-09-21 精工爱普生株式会社 造粒粉末以及造粒粉末的制造方法
WO2014176045A1 (en) 2013-04-24 2014-10-30 United Technologies Corporation Fluidized bed for degassing and heat treating powders
CN111033215A (zh) * 2017-08-25 2020-04-17 福田金属箔粉工业株式会社 层压成形用粉末评价方法以及层压成形用粉末
EP3674683A4 (de) * 2017-08-25 2021-02-17 Fukuda Metal Foil & Powder Co., Ltd. Verfahren zur evaluierung von pulver für laminatformung und pulver für laminatformung

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EP3016135A4 (de) * 2013-06-28 2017-09-20 Furukawa Electric Co., Ltd. Verbindungsstruktur und halbleiterbauelement
CN114226714B (zh) * 2021-12-17 2023-07-21 武汉苏泊尔炊具有限公司 粉末冶金材料及其制备方法和其应用

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US9316253B2 (en) * 2008-02-21 2016-04-19 Ntn Corporation Sintered bearing
US20100310199A1 (en) * 2008-02-21 2010-12-09 Ntn Corporation Sintered bearing
CN102189253A (zh) * 2010-03-11 2011-09-21 精工爱普生株式会社 造粒粉末以及造粒粉末的制造方法
EP2366475A1 (de) * 2010-03-11 2011-09-21 Seiko Epson Corporation Granulatpulver und Verfahren zur Herstellung des Granulatpulvers
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CN105142830A (zh) * 2013-04-24 2015-12-09 联合工艺公司 用于脱气和热处理粉末的流化床
WO2014176045A1 (en) 2013-04-24 2014-10-30 United Technologies Corporation Fluidized bed for degassing and heat treating powders
US9993872B2 (en) 2013-04-24 2018-06-12 United Technologies Corporation Fluidized bed for degassing and heat treating powders
CN111033215A (zh) * 2017-08-25 2020-04-17 福田金属箔粉工业株式会社 层压成形用粉末评价方法以及层压成形用粉末
EP3674683A4 (de) * 2017-08-25 2021-02-17 Fukuda Metal Foil & Powder Co., Ltd. Verfahren zur evaluierung von pulver für laminatformung und pulver für laminatformung
EP3674682A4 (de) * 2017-08-25 2021-02-17 Fukuda Metal Foil & Powder Co., Ltd. Verfahren zur evaluierung von pulver für laminatformen und pulver für laminatformen
US11448578B2 (en) 2017-08-25 2022-09-20 Fukuda Metal Foil & Powder Co., Ltd. Lamination shaping powder evaluation method and lamination shaping powder therefor
US11644397B2 (en) 2017-08-25 2023-05-09 Fukuda Metal Foil & Powder Co., Ltd. Lamination shaping powder evaluation method and lamination shaping powder therefor

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