EP3050985B1 - Poudre de métal pour métallurgie des poudres, composé, poudre granulée et corps fritté - Google Patents

Poudre de métal pour métallurgie des poudres, composé, poudre granulée et corps fritté Download PDF

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EP3050985B1
EP3050985B1 EP16152921.9A EP16152921A EP3050985B1 EP 3050985 B1 EP3050985 B1 EP 3050985B1 EP 16152921 A EP16152921 A EP 16152921A EP 3050985 B1 EP3050985 B1 EP 3050985B1
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mass
less
sintered body
powder
content
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EP3050985A1 (fr
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Hidefumi Nakamura
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Seiko Epson Corp
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Seiko Epson Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • 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
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/24—After-treatment of workpieces or articles
    • 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
    • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
    • 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
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/02—Making ferrous alloys by powder metallurgy
    • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
    • C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
    • C22C33/0285—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5% with Cr, Co, or Ni having a minimum content higher than 5%
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • B22F1/09—Mixtures of metallic powders
    • 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
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/24—After-treatment of workpieces or articles
    • B22F2003/248—Thermal after-treatment
    • 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
    • B22F2301/00—Metallic composition of the powder or its coating
    • B22F2301/35—Iron
    • 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
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps
    • 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
    • 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
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/12—Both compacting and sintering
    • B22F3/14—Both compacting and sintering simultaneously
    • B22F3/15—Hot isostatic pressing

Definitions

  • the present invention relates to a metal powder for powder metallurgy, a compound, a granulated powder, and a sintered body.
  • a composition containing a metal powder and a binder is molded into a desired shape to obtain a molded body, and the obtained molded body is degreased and sintered, whereby a sintered body is produced.
  • an atomic diffusion phenomenon occurs among particles of the metal powder, whereby the molded body is gradually densified, resulting in sintering.
  • JP-A-2012-87416 proposes a metal powder for powder metallurgy which contains Zr and Si, with the remainder including at least one element selected from the group consisting of Fe, Co, and Ni, and inevitable elements.
  • the sinterability is enhanced by the action of Zr, and a sintered body having a high density can be easily produced.
  • the thus obtained sintered body has recently become widely used for a variety of machine parts, structural parts, and the like.
  • a sintered body is further subjected to an additional treatment such as a hot isostatic pressing treatment (HIP treatment) to increase the density, however, the workload is significantly increased, and also an increase in the cost is inevitable.
  • HIP treatment hot isostatic pressing treatment
  • EP 1 768 803 A1 US 2007/023107 A1 ; US 2010/258217 A1 ; US 2003/089198 A1 and EP 1 295 958 A1 .
  • An advantage of some aspects of the invention is to provide a metal powder for powder metallurgy, a compound, and a granulated powder, each of which is capable of producing a sintered body having a high density, and a sintered body having a high density.
  • a metal powder for powder metallurgy according to an aspect of the invention includes particles as defined in claim 1.
  • the crystal contains Fe as a principal component
  • the particle further includes a region, which has a smaller volume than the crystal, and in which the ratio of the content of Si to the content of Fe is higher than in the crystal.
  • the circle equivalent diameter of the crystal is 1% or more and 100% or less the circle equivalent diameter of the particle.
  • the crystal can dominantly behave with respect to the sinterability of the particles when they are fired. That is, the particles behave as if they were single crystal grains, and therefore, the sintering rate is increased, and thus, this configuration greatly contributes to an increase in the sintered density.
  • the crystal has a martensite crystal structure.
  • the martensite crystal structure includes a body-centered cubic lattice in the form of a solid solution supersaturated with, for example, C.
  • This body-centered cubic lattice is formed by transformation from a face-centered cubic lattice accompanying firing or a heat treatment after firing, and the volume thereof is expanded at that time. Therefore, a metal powder for powder metallurgy having a martensite crystal structure is capable of producing a sintered body having a high hardness.
  • a compound according to an aspect of the invention includes the metal powder for powder metallurgy according to the aspect of the invention and a binder which binds the particles of the metal powder for powder metallurgy to one another.
  • a granulated powder according to an aspect of the invention is obtained by granulating the metal powder for powder metallurgy according to the aspect of the invention.
  • a sintered body according to an aspect of the invention is produced by sintering the metal powder for powder metallurgy according to the aspect of the invention.
  • a sintered body having a desired shape can be obtained by molding a composition containing a metal powder for powder metallurgy and a binder into a desired shape, followed by degreasing and firing.
  • a sintered body with a complicated and fine shape can be produced in a near-net shape (a shape close to a final shape) as compared with the other metallurgy techniques.
  • the obtained sintered body was further subjected to an additional treatment such as a hot isostatic pressing treatment (HIP treatment) to increase the density.
  • an additional treatment such as a hot isostatic pressing treatment (HIP treatment) to increase the density.
  • HIP treatment hot isostatic pressing treatment
  • the present inventors have made intensive studies to find conditions for obtaining a sintered body having a high density without performing an additional treatment. As a result, they found that the density of a sintered body can be increased by optimizing the chemical composition and the crystal structure of each particle contained in a metal powder, and thus completed the invention.
  • the metal powder for powder metallurgy according to this embodiment includes particles as defined in claim 1. According to the metal powder for powder metallurgy containing such particles, when the particles are sintered in a firing step, the sintering is promoted and densification proceeds. As a result, a sintered body having a sufficiently high density can be produced without performing an additional treatment.
  • Such a sintered body has excellent mechanical properties. Due to this, the sintered body can be widely applied also to, for example, machine parts, structural parts, and the like, to which an external force is applied.
  • the first element is one element selected from the group consisting of the following seven elements: Ti, V, Y, Zr, Nb, Hf, and Ta
  • the second element is one element selected from the group consisting of the above-mentioned seven elements and having a higher group number in the periodic table than that of the first element or one element selected from the group consisting of the above-mentioned seven elements and having the same group number in the periodic table as that of the element selected as the first element and a higher period number in the periodic table than that of the first element.
  • metal powder for powder metallurgy is sometimes simply referred to as “metal powder”
  • particle each of the multiple particles constituting the metal powder for powder metallurgy
  • FIG. 1 is a view schematically showing the cross sections of particles contained in an embodiment of the metal powder for powder metallurgy according to the invention
  • FIG. 2 is a view schematically showing the crystal structure of the particle shown in FIG. 1 .
  • a particle 1 shown in FIG. 1 is constituted by an Fe-based alloy. As shown in FIG. 2 , the particle 1 includes one or more and 5 or less crystals on average in the cross section.
  • the crystal is preferably a crystal containing Fe as a principal component. Then, these crystals occupy most (90% or more in terms of area ratio) of the cross section of the particle 1. Therefore, these crystals have an influence on the properties of the particle 1 (metal powder for powder metallurgy) and the properties of a sintered body to be produced from the particle 1.
  • the particle 1 is a particle having a very small number of Fe-based alloy crystals contained therein.
  • Such a particle 1 can be said to be single-crystalline or polycrystalline close to single-crystalline, and behaves in the same manner as a single crystal when it is fired. Therefore, when the metal powder for powder metallurgy is fired, sintering proceeds at an excellent sintering rate derived from the single crystal. As a result, a sintered body having few internal gaps and a high relative density can be produced.
  • Fe is contained as a principal component in the crystal refers to a state in which Fe is an element contained at the highest concentration in a local chemical composition of the crystal.
  • the chemical composition of the crystal can be determined by, for example, a qualitative and quantitative analysis by energy dispersive X-ray spectrometry.
  • the cross-sectional view of the particle 1 shown in FIG. 2 is an example showing the presence of typical crystals among many particles contained in the metal powder for powder metallurgy.
  • the particle 1 shown in FIG. 2 includes four Fe-based alloy crystals 2.
  • the adjacent Fe-based alloy crystals 2 are separated by a linear grain boundary 3.
  • the particle 1 includes 1 or more and 5 or less Fe-based alloy crystals 2 on average in the cross section of the particle.
  • the average number of the Fe-based alloy crystals 2 in the cross section of the particle 1 is a value obtained by observing the cross sections of 10 or more particles 1 contained in the metal powder as observation targets with an electron microscope, counting the number of the Fe-based alloy crystals 2 contained in each particle 1 by visual observation of an observation image, and averaging the counts in all the observation targets.
  • the electron microscope for example, a transmission electron microscope (TEM) is used, and the observation can be performed in a bright field image.
  • TEM transmission electron microscope
  • the grain boundary 3 may be easily specified by changing the bright field image into a dark field image in some cases.
  • the circle equivalent diameter of the Fe-based alloy crystal 2 (the diameter of a circle having the same area as that of the cross section of the Fe-based alloy crystal 2) is preferably 1% or more and 100% or less, more preferably 3% or more and less than 100% of the circle equivalent diameter of the particle 1 (the diameter of a circle having the same area as that of the cross section of the particle 1).
  • the Fe-based alloy crystal 2 can dominantly behave with respect to the sinterability of the particles 1 when they are fired. That is, the particle 1 behaves as if it was a single crystal grain, and therefore, the sintering rate is increased, and thus, this configuration greatly contributes to an increase in the sintered density.
  • FIG. 3 is an enlarged view of an area A surrounded by the dashed line in FIG. 2 .
  • a high Si concentration region 4 which has a smaller volume than the Fe-based alloy crystal 2, and in which the ratio of the content of Si to the content of Fe is higher than in the Fe-based alloy crystal 2, is present.
  • a sintered body produced by using the metal powder containing the particle 1 has a high relative density and excellent mechanical properties.
  • the high Si concentration region 4 is a region, which is present in the inside of the Fe-based alloy crystal 2 or at the grain boundary 3, and in which the ratio of the content of Si to the content of Fe is higher than in the Fe-based alloy crystal 2.
  • the contents of these elements can be determined by, for example, the qualitative and quantitative analysis of each of the Fe-based alloy crystal 2 and the high Si concentration region 4 by energy dispersive X-ray spectrometry (EDX) .
  • the height of a peak of Fe located at near 6.4 keV and the height of a peak of Si located at near 1.8 keV in the EDX spectrum are determined, and the ratio of the height of the peak of Si to the height of the peak of Fe is calculated, whereby the ratio of the content of Si to the content of Fe can be obtained.
  • the particle 1 satisfies the following formula (1). Si 2 / Fe 2 ⁇ Si 4 / Fe 4
  • the position of the high Si concentration region 4 in the cross section of the particle 1 is not particularly limited, but is preferably at the grain boundary 3. According to this, the sintering rate of the Fe-based alloy crystal 2 is particularly increased, and thus, a sintered body having a particularly high relative density can be produced.
  • the shape of the high Si concentration region 4 in the cross section of the particle 1 is not particularly limited and may be any shape, but is preferably a circle, a polygon, or a shape equivalent thereto.
  • the sinterability of the particle 1 is further enhanced, and the relative density of a sintered body produced by using the metal powder containing such particles 1 is further increased.
  • the shape of the high Si concentration region 4 is preferably a shape having a low aspect ratio.
  • the average of the aspect ratio defined by the major axis/minor axis of the high Si concentration region 4 is preferably 1 or more and 3 or less, more preferably 1 or more and 2 or less.
  • the "major axis" of the high Si concentration region 4 is the maximum length of the high Si concentration region 4, and the “minor axis” is the maximum length in the direction perpendicular to the major axis.
  • the particle 1 preferably satisfies the following formula (2), more preferably satisfies the following formula (3).
  • 1.2 ⁇ Si 2 / Fe 2 ⁇ Si 4 / Fe 4 ⁇ 1 1.3 ⁇ Si 2 / Fe 2 ⁇ Si 4 / Fe 4 ⁇ 0.8
  • FIG. 4A shows one example of a TEM image (bright field image) of the cross section of the particle 1
  • FIG. 4B shows one example of a TEM image (dark field image) of the cross section of the particle 1 shown in FIG. 4A .
  • FIG. 4A In the TEM image (bright field image) shown in FIG. 4A , two Fe-based alloy crystals 2 contained in the particle 1 are shown. Further, a line based on a difference in shading indicated by the arrows in FIG. 4A is the grain boundary 3 located on a boundary between the two Fe-based alloy crystals 2.
  • one Fe-based alloy crystal 2 located on the upper right side appears in a light color and the other Fe-based alloy crystal 2 located on the lower left side appears in a dark color.
  • the contrast between the two Fe-based alloy crystals 2 can be enhanced based on the difference in the type of crystal.
  • FIG. 5 is a partial enlarged view of an area B surrounded by the dashed line shown in FIG. 4A and is an observation image when the area B was observed with a high-angle annular dark field scanning transmission electron microscope.
  • a dark color portion indicated by the arrow in FIG. 5 is the high Si concentration region 4.
  • FIG. 6 shows one example of the EDX spectrum of the high Si concentration region 4 shown in FIG. 5 and shows a spectrum obtained by a point analysis at a position (Position 1 in FIG. 6 ) corresponding to the high Si concentration region 4 shown in FIG. 5 .
  • FIG. 7 shows one example of the EDX spectrum of the Fe-based alloy crystal 2 shown in FIG. 5 and shows a spectrum obtained by a point analysis at a position (Position 2 in FIG. 7 ) corresponding to the Fe-based alloy crystal 2 shown in FIG. 5 .
  • FIG. 8A shows one example of a TEM image (bright field image) of the cross section of a particle containing 6 or more Fe-based alloy crystals
  • FIG. 8B shows one example of a TEM image (dark field image) of the cross section of the particle shown in FIG. 8A
  • the particle shown in FIGS. 8A and 8B has a chemical composition containing no first element or second element described above and corresponds to Comparative Example with respect to the invention.
  • the Fe-based alloy crystal 2 preferably has a martensite crystal structure.
  • the martensite crystal structure includes a body-centered cubic lattice in the form of a solid solution supersaturated with, for example, C. This body-centered cubic lattice is formed by transformation from a face-centered cubic lattice accompanying firing or a heat treatment after firing, and the volume thereof is expanded at that time. Therefore, the Fe-based alloy crystal 2 having a martensite crystal structure enables the production of a sintered body having a high hardness.
  • the metal powder for powder metallurgy has a martensite crystal structure by, for example, X-ray diffractometry.
  • Fe is an element (principal component) whose content is the highest and has an influence on the properties of the sintered body.
  • the content of Fe in the whole particle 1 is 50% by mass or more.
  • Cr chromium
  • the content of Cr in the particle 1 is set to 10% by mass or more and 30% by mass or less, but is set to preferably 10.5% by mass or more and 20% by mass or less, more preferably 11% by mass or more and 18% by mass or less. If the content of Cr is less than the above lower limit, the corrosion resistance of a sintered body to be produced may be insufficient depending on the overall composition. On the other hand, if the content of Cr exceeds the above upper limit, the sinterability is deteriorated depending on the overall composition so that it may become difficult to increase the density of the sintered body.
  • C carbon
  • the first element and the second element each form a carbide by binding to C.
  • the dispersed deposit serves as an obstacle to inhibit the significant growth of crystal grains, and therefore, a variation in the size of crystal grains is suppressed. Accordingly, it becomes difficult to generate pores in a sintered body, and also the increase in the size of crystal grains is prevented, and thus, a sintered body having a high density and excellent mechanical properties is obtained.
  • the content of C in the particle 1 is set to 0.1% by mass or more and 2% by mass or less, but is set to preferably 0.35% by mass or more and 1.15% by mass or less, more preferably 0.4% by mass or more and 1.1% by mass or less. If the content of C is less than the above lower limit, crystal grains are liable to grow depending on the overall composition so that the mechanical properties of the sintered body are insufficient. On the other hand, if the content of C exceeds the above upper limit, the amount of C is too large depending on the overall composition so that the sinterability is deteriorated instead.
  • Si silicon is an element which provides corrosion resistance and high mechanical properties to a sintered body to be produced, and by using the metal powder containing Si, a sintered body capable of maintaining high mechanical properties over a long period of time can be obtained.
  • the content of Si in the particle 1 is set to 0.2% by mass or more and 1.5% by mass or less, but is set to preferably 0.3% by mass or more and 1% by mass or less, more preferably 0.5% by mass or more and 0.8% by mass or less. If the content of Si is less than the above lower limit, the effect of the addition of Si is weakened depending on the overall composition so that the corrosion resistance and the mechanical properties of a sintered body to be produced may be deteriorated. On the other hand, if the content of Si exceeds the above upper limit, the amount of Si is too large depending on the overall composition so that the corrosion resistance and the mechanical properties may be deteriorated instead.
  • Mn is an element which is added as needed and provides corrosion resistance and high mechanical properties to a sintered body to be produced in the same manner as Si.
  • the content of Mn in the particle 1 is 0.01% by mass or more and 1.25% by mass or less, more preferably 0.03% by mass or more and 0.3% by mass or less, further more preferably 0.05% by mass or more and 0.2% by mass or less.
  • the corrosion resistance and the mechanical properties of a sintered body to be produced may not be sufficiently enhanced depending on the overall composition.
  • the content of Mn exceeds the above upper limit, the corrosion resistance and the mechanical properties may be deteriorated instead.
  • Ni is an element which is added as needed and provides corrosion resistance and heat resistance to a sintered body to be produced.
  • the content of Ni in the particle 1 is 0.05% by mass or more and 0.6% by mass or less, more preferably 0.06% by mass or more and 0.4% by mass or less, further more preferably 0.07% by mass or more and 0.25% by mass or less.
  • the corrosion resistance and the heat resistance of a sintered body to be produced may not be sufficiently enhanced depending on the overall composition.
  • the content of Ni exceeds the above upper limit, the corrosion resistance and the heat resistance may be deteriorated instead.
  • Mn and Ni are contained in a total proportion of preferably 0.05% by mass or more and 1.6% by mass or less, more preferably 0.08% by mass or more and 1.3% by mass or less, further more preferably 0.1% by mass or more and 1% by mass or less. According to this, the mechanical properties of the sintered body can be particularly enhanced.
  • the first element and the second element each deposit a carbide or an oxide (hereinafter also collectively referred to as "carbide or the like”) . It is considered that this deposited carbide or the like inhibits the significant growth of crystal grains when the metal powder is sintered. As a result, as described above, it becomes difficult to generate pores in a sintered body, and also the increase in the size of crystal grains is prevented, and thus, a sintered body having a high density and excellent mechanical properties is obtained.
  • carbide or an oxide hereinafter also collectively referred to as "carbide or the like
  • the deposited carbide or the like promotes the accumulation of silicon oxide at a crystal grain boundary, and as a result, the sintering is promoted and the density is increased while preventing the increase in the size of crystal grains.
  • the first element and the second element are two elements selected from the group consisting of the following seven elements: Ti, V, Y, Zr, Nb, Hf, and Ta, but preferably include an element belonging to group III A or group IV A in the long periodic table (Ti, Y, Zr, or Hf).
  • an element belonging to group III A or group IV A as at least one of the first element and the second element, oxygen contained as an oxide in the metal powder is removed and the sinterability of the metal powder can be particularly enhanced.
  • the first element is only required to be one element selected from the group consisting of the following seven elements: Ti, V, Y, Zr, Nb, Hf, and Ta as described above, but is preferably an element belonging to group III A or group IV A in the long periodic table in the group consisting of the above-mentioned seven elements.
  • An element belonging to group III A or group IV A removes oxygen contained as an oxide in the metal powder and therefore can particularly enhance the sinterability of the metal powder. According to this, the concentration of oxygen remaining in the crystal grains after sintering can be decreased. As a result, the content of oxygen in the sintered body can be decreased, and the density can be increased. Further, these elements are elements having high activity, and therefore are considered to cause rapid atomic diffusion.
  • this atomic diffusion acts as a driving force, and thereby a distance between particles of the metal powder is efficiently decreased and a neck is formed between the particles, so that the densification of a molded body is promoted. As a result, the density of the sintered body can be further increased.
  • the second element is only required to be one element selected from the group consisting of the following seven elements: Ti, V, Y, Zr, Nb, Hf, and Ta and different from the first element as described above, but is preferably an element belonging to group V A in the long periodic table in the group consisting of the above-mentioned seven elements.
  • An element belonging to group V A particularly efficiently deposits the above-mentioned carbide or the like, and therefore, can efficiently inhibit the significant growth of crystal grains during sintering. As a result, the formation of fine crystal grains is promoted, and thus, the density of the sintered body can be increased and also the mechanical properties of the sintered body can be enhanced.
  • the metal powder containing such a first element and a second element enables the production of a sintered body having a particularly high density.
  • Zr is a ferrite forming element, and therefore deposits a body-centered cubic lattice phase.
  • This body-centered cubic lattice phase has more excellent sinterability than the other crystal lattice phases, and therefore contributes to the densification of a sintered body.
  • the atomic radius of Zr is slightly larger than that of Fe. Specifically, the atomic radius of Fe is about 0.117 nm, and the atomic radius of Zr is about 0.145 nm. Therefore, Zr is solid-dissolved in Fe, but is not completely solid-dissolved therein, and part of Zr is deposited as a carbide or the like. According to this, an appropriate amount of a carbide or the like is deposited, and therefore, the increase in the size of crystal grains can be effectively prevented while promoting the sintering and increasing the density.
  • the atomic radius of Nb is slightly larger than that of Fe, but slightly smaller than that of Zr. Specifically, the atomic radius of Fe is about 0.117 nm, and the atomic radius of Nb is about 0.134 nm. Therefore, Nb is solid-dissolved in Fe, but is not completely solid-dissolved therein, and part of Nb is deposited as a carbide or the like. According to this, an appropriate amount of a carbide or the like is deposited, and therefore, the increase in the size of crystal grains can be effectively prevented while promoting the sintering and increasing the density.
  • the content of the first element in the particle 1 is set to 0.01% by mass or more and 0.5% by mass or less, but is set to preferably 0.03% by mass or more and 0.3% by mass or less, more preferably 0.05% by mass or more and 0.2% by mass or less. If the content of the first element is less than the above lower limit, the effect of the addition of the first element is weakened depending on the overall composition so that the density of a sintered body to be produced may not be sufficiently increased. On the other hand, if the content of the first element exceeds the above upper limit, the amount of the first element is too large depending on the overall composition so that the ratio of the above-mentioned carbide or the like is too high, and therefore, the densification may be deteriorated instead.
  • the content of the second element in the particle 1 is set to 0.01% by mass or more and 0.5% by mass or less, but is set to preferably 0.03% by mass or more and 0.3% by mass or less, more preferably 0.05% by mass or more and 0.2% by mass or less. If the content of the second element is less than the above lower limit, the effect of the addition of the second element is weakened depending on the overall composition so that the density of a sintered body to be produced may not be sufficiently increased. On the other hand, if the content of the second element exceeds the above upper limit, the amount of the second element is too large depending on the overall composition so that the ratio of the above-mentioned carbide or the like is too high, and therefore, the densification may be deteriorated instead.
  • each of the first element and the second element deposits a carbide or the like, however, in the case where an element belonging to group III A or group IV A is selected as the first element as described above and an element belonging to group V A is selected as the second element as described above, it is presumed that when the metal powder is sintered, the timing when a carbide or the like of the first element is deposited and the timing when a carbide or the like of the second element is deposited differ from each other. It is considered that due to the difference in timing when a carbide or the like is deposited in this manner, sintering gradually proceeds so that the generation of pores is prevented, and thus, a dense sintered body is obtained. That is, it is considered that by the presence of both of the carbide or the like of the first element and the carbide or the like of the second element, the increase in the size of crystal grains can be suppressed while increasing the density of the sintered body.
  • the carbide or the like of the first element and the carbide or the like of the second element act as "nuclei", and the accumulation of silicon oxide occurs.
  • the concentration of oxides inside the crystal is decreased, and therefore, sintering is promoted.
  • the densification of the sintered body is further promoted when the particles 1 are sintered.
  • the particle 1 is only required to contain two elements selected from the group consisting of the above-mentioned seven elements, but may further contain an element which is selected from this group and is different from these two elements. That is, the particle 1 may contain three or more elements selected from the group consisting of the above-mentioned seven elements. According to this, the above-mentioned effect can be further enhanced, which slightly varies depending on the combination of the elements to be contained.
  • the ratio of the content of the first element to the content of the second element in consideration of the mass number of the first element and the mass number of the second element.
  • X1/X2 is preferably 0.3 or more and 3 or less, more preferably 0.5 or more and 2 or less, further more preferably 0.75 or more and 1.3 or less.
  • pores remaining in a molded body can be eliminated as if they were swept out sequentially from the inside, and therefore, pores generated in a sintered body can be minimized. Accordingly, a metal powder capable of producing a sintered body having a high density and excellent mechanical properties can be obtained by setting the ratio X1/X2 within the above range.
  • the ratio (E1/E2) of the content E1 of the first element to the content E2 of the second element is calculated.
  • E1/E2 is preferably 0.29 or more and 2.95 or less, more preferably 0.49 or more and 1.96 or less.
  • E1/E2 is preferably 0.58 or more and 5.76 or less, more preferably 0.96 or more and 3.84 or less.
  • E1/E2 is preferably 0.15 or more and 1.55 or less, more preferably 0.26 or more and 1.03 or less.
  • E1/E2 is preferably 0.15 or more and 1.54 or less, more preferably 0.26 or more and 1.03 or less.
  • E1/E2 is preferably 0.29 or more and 2.87 or less, more preferably 0.48 or more and 1.91 or less.
  • E1/E2 is preferably 0.16 or more and 1.64 or less, more preferably 0.27 or more and 1.10 or less.
  • E1/E2 is preferably 0.16 or more and 1.58 or less, more preferably 0.26 or more and 1.05 or less.
  • E1/E2 is preferably 0.15 or more and 1.51 or less, more preferably 0.25 or more and 1.01 or less.
  • E1/E2 is preferably 0.54 or more and 5.38 or less, more preferably 0.90 or more and 3.58 or less.
  • E1/E2 can be calculated in the same manner as described above.
  • the presence of the high Si concentration region 4 can also be determined by, for example, a mapping analysis by energy dispersive X-ray spectrometry (EDX).
  • EDX energy dispersive X-ray spectrometry
  • the content E1 of the first element and the content E2 of the second element are as described above, respectively, however, the sum of the contents of these elements is preferably 0.05% by mass or more and 0.6% by mass or less, more preferably 0.10% by mass or more and 0.48% by mass or less, further more preferably 0.12% by mass or more and 0.24% by mass or less.
  • (E1+E2) /Si is preferably 0.1 or more and 0.7 or less, more preferably 0.15 or more and 0.6 or less, further more preferably 0.2 or more and 0.5 or less in terms of mass ratio.
  • the particle 1 in the particle 1, necessary and sufficient accumulation of silicon oxide occurs by using the carbide or the like of the first element and the carbide or the like of the second element as nuclei, and in the case where an element such as Cr or Ni is contained in the particle 1 other than Fe, an oxidation reaction of such an element is easily suppressed. Therefore, also from this viewpoint, the sinterability of the particle 1 is enhanced, and thus, a sintered body having a higher density, excellent mechanical properties, and excellent corrosion resistance can be obtained.
  • the carbide or the like of the first element or the carbide or the like of the second element and silicon oxide it is not always necessary for the carbide or the like to be located at the center of silicon oxide, and for example, these components may have a positional relationship such that silicon oxide is accumulated inside the carbide or the like.
  • (E1+E2)/C is preferably 1 or more and 16 or less, more preferably 2 or more and 13 or less, further more preferably 3 or more and 10 or less.
  • the particle 1 may contain, other than the above-mentioned elements, at least one element of Mo, Pb, S, and Al as needed. These elements may be inevitably contained in some cases.
  • Mo is an element which enhances the corrosion resistance of a sintered body to be produced.
  • the content of Mo in the particle 1 is 0.2% by mass or more and 0.8% by mass or less, more preferably 0.3% by mass or more and 0.6% by mass or less.
  • Pb is an element which enhances the machinability of a sintered body to be produced.
  • the content of Pb in the particle 1 is 0.03% by mass or more and 0.5% by mass or less, more preferably 0.05% by mass or more and 0.3% by mass or less.
  • S is an element which enhances the machinability of a sintered body to be produced.
  • the content of S in the particle 1 is 0.5% by mass or less, more preferably 0.01% by mass or more and 0.3% by mass or less.
  • Al is an element which enhances the oxidation resistance of a sintered body to be produced.
  • the content of Al in the particle 1 is 0.5% by mass or less, more preferably 0.05% by mass or more and 0.3% by mass or less.
  • B, Se, Te, Pd, W, Co, N, Cu may be added other than the above-mentioned elements.
  • the contents of these elements are not particularly limited, but the content of each of these elements is preferably less than 0.1% by mass, and also the total content of these elements is preferably less than 0.2% by mass. These elements may be inevitably contained in some cases.
  • the particle 1 may contain impurities.
  • the impurities include all elements other than the above-mentioned elements, and specific examples thereof include Li, Be, Na, Mg, P, K, Ca, Sc, Zn, Ga, Ge, Ag, In, Sn, Sb, Os, Ir, Pt, Au, and Bi.
  • the incorporation amounts of these impurity elements are preferably set such that the content of each of the impurity elements is less than the content of each of Fe, Cr, Si, the first element, and the second element. Further, the incorporation amounts of these impurity elements are preferably set such that the content of each of the impurity elements is less than 0.03% by mass, more preferably less than 0.02% by mass.
  • the total content of these impurity elements is set to preferably less than 0.3% by mass, more preferably less than 0.2% by mass. These elements do not inhibit the effect as described above as long as the contents thereof are within the above range, and therefore may be intentionally added to the metal powder.
  • O oxygen
  • the amount thereof is preferably 0.8% by mass or less, more preferably 0.5% by mass or less.
  • the sinterability is enhanced, and thus, a sintered body having a high density and excellent mechanical properties is obtained.
  • the lower limit thereof is not particularly set, but is preferably 0.03% by mass or more from the viewpoint of ease of mass production or the like.
  • Fe is a component (principal component) whose content is the highest in the alloy constituting the metal powder for powder metallurgy according to the invention and has a great influence on the properties of the sintered body.
  • the compositional ratio of the particle 1 can be determined by, for example, Iron and steel - Atomic absorption spectrometric method specified in JIS G 1257 (2000), Iron and steel - ICP atomic emission spectrometric method specified in JIS G 1258 (2007), Iron and steel - Method for spark discharge atomic emission spectrometric analysis specified in JIS G 1253 (2002), Iron and steel - Method for X-ray fluorescence spectrometric analysis specified in JIS G 1256 (1997), gravimetric, titrimetric, and absorption spectrometric methods specified in JIS G 1211 to G 1237, or the like.
  • an optical emission spectrometer for solids (spark optical emission spectrometer, model: SPECTROLAB, type: LAVMB08A) manufactured by SPECTRO Analytical Instruments GmbH or an ICP device (model: CIROS-120) manufactured by Rigaku Corporation can be used.
  • JIS G 1211 to G 1237 are as follows.
  • C (carbon) and S (sulfur) are determined, particularly, an infrared absorption method after combustion in a current of oxygen (after combustion in a high-frequency induction heating furnace) specified in JIS G 1211 (2011) is also used.
  • a carbon-sulfur analyzer, CS-200 manufactured by LECO Corporation can be used.
  • N (nitrogen) and O (oxygen) are determined, particularly, a method for determination of nitrogen content in iron and steel specified in JIS G 1228 (2006) and a method for determination of oxygen content in metallic materials specified in JIS Z 2613 (2006) are also used.
  • an oxygen-nitrogen analyzer TC-300/EF-300 manufactured by LECO Corporation can be used.
  • the particle 1 as described above is preferably contained in the metal powder for powder metallurgy as much as possible, and specifically, the particle 1 is contained in the metal powder for powder metallurgy in an amount of preferably 50% by number or more, more preferably 60% by number or more. According to such a metal powder for powder metallurgy, the effect as described above is more reliably exhibited, and a sintered body having a high density and excellent mechanical properties can be more reliably produced.
  • the average particle diameter of the metal powder for powder metallurgy according to the invention is preferably 0.5 ⁇ m or more and 30 ⁇ m or less, more preferably 1 ⁇ m or more and 20 ⁇ m or less, further more preferably 2 ⁇ m or more and 10 ⁇ m or less.
  • the average particle diameter can be obtained as a particle diameter when the cumulative amount obtained by cumulating the percentages of the particles from the smaller diameter side reaches 50% in a cumulative particle size distribution on a mass basis obtained by laser diffractometry.
  • the average particle diameter of the metal powder for powder metallurgy is less than the above lower limit, the moldability is deteriorated in the case where the shape is difficult to mold, and therefore, the sintered density may be decreased.
  • the average particle diameter of the metal powder exceeds the above upper limit, spaces between the particles become larger during molding, and therefore, the sintered density may be decreased also in this case.
  • the particle size distribution of the metal powder for powder metallurgy is preferably as narrow as possible. Specifically, when the average particle diameter of the metal powder for powder metallurgy is within the above range, the maximum particle diameter of the metal powder is preferably 200 ⁇ m or less, more preferably 150 ⁇ m or less. By controlling the maximum particle diameter of the metal powder for powder metallurgy within the above range, the particle size distribution of the metal powder for powder metallurgy can be made narrower, and thus, the density of the sintered body can be further increased.
  • the "maximum particle diameter” refers to a particle diameter when the cumulative amount obtained by cumulating the percentages of the particles from the smaller diameter side reaches 99.9% in a cumulative particle size distribution on a mass basis obtained by laser diffractometry.
  • the average of the aspect ratio defined by S/L is preferably about 0.4 or more and 1 or less, more preferably about 0.7 or more and 1 or less.
  • the metal powder for powder metallurgy having an aspect ratio within this range has a shape relatively close to a spherical shape, and therefore, the packing factor when the metal powder is molded is increased. As a result, the density of the sintered body can be further increased.
  • the “major axis” is the maximum length in the projected image of the particle
  • the “minor axis” is the maximum length in the direction perpendicular to the major axis.
  • the average of the aspect ratio can be obtained as the average of the measured aspect ratios of 100 or more particles.
  • the tap density of the metal powder for powder metallurgy according to the invention is preferably 3.5 g/cm 3 or more, more preferably 4 g/cm 3 or more. According to the metal powder for powder metallurgy having such a high tap density, when a molded body is obtained, the interparticle packing efficiency is particularly increased. Therefore, a particularly dense sintered body can be obtained in the end.
  • the specific surface area of the metal powder for powder metallurgy according to the invention is not particularly limited, but is preferably 0.1 m 2 /g or more, more preferably 0.2 m 2 /g or more. According to the metal powder for powder metallurgy having such a large specific surface area, a surface activity (surface energy) is increased so that it is possible to easily sinter the metal powder even if less energy is applied. Therefore, when a molded body is sintered, a difference in sintering rate hardly occurs between the inner side and the outer side of the molded body, and thus, the decrease in the sintered density due to the pores remaining inside the molded body can be suppressed.
  • the method for producing a sintered body includes (A) a composition preparation step in which a composition for producing a sintered body is prepared, (B) a molding step in which a molded body is produced, (C) a degreasing step in which a degreasing treatment is performed, and (D) a firing step in which firing is performed.
  • A a composition preparation step in which a composition for producing a sintered body is prepared
  • B a molding step in which a molded body is produced
  • C a degreasing step in which a degreasing treatment is performed
  • D a firing step in which firing is performed.
  • the metal powder for powder metallurgy according to the invention and a binder are prepared, and these materials are kneaded using a kneader, whereby a kneaded material (composition) is obtained.
  • the metal powder for powder metallurgy is uniformly dispersed.
  • the metal powder for powder metallurgy according to the invention is produced by, for example, any of a variety of powdering methods such as an atomization method (such as a water atomization method, a gas atomization method, or a spinning water atomization method), a reducing method, a carbonyl method, and a pulverization method.
  • an atomization method such as a water atomization method, a gas atomization method, or a spinning water atomization method
  • a reducing method such as a carbonyl method, and a pulverization method.
  • the metal powder for powder metallurgy according to the invention is preferably a metal powder produced by an atomization method, more preferably a metal powder produced by a water atomization method or a spinning water atomization method.
  • the atomization method is a method in which a molten metal (metal melt) is caused to collide with a fluid (liquid or gas) sprayed at a high speed to atomize the metal melt into a fine powder and also to cool the fine powder, whereby a metal powder is produced.
  • a molten metal metal melt
  • a fluid liquid or gas
  • the metal powder when the metal powder is molded, a molded body having a high packing factor is obtained. That is, a powder capable of producing a sintered body having a high density can be obtained.
  • the cooling rate of the metal melt is very high, and therefore, the particle 1 in which the sizes of the Fe-based alloy crystals 2 are uniform can be obtained.
  • the pressure of water (hereinafter referred to as "atomization water") to be sprayed to the molten metal is not particularly limited, but is set to preferably about 75 MPa or more and 120 MPa or less (750 kgf/cm 2 or more and 1200 kgf/cm 2 or less), more preferably about 90 MPa or more and 120 MPa or less (900 kgf/cm 2 or more and 1200 kgf/cm 2 or less).
  • the temperature of the atomization water is also not particularly limited, but is preferably set to about 1°C or higher and 20°C or lower.
  • the atomization water is often sprayed in a cone shape such that it has a vertex on the falling path of the metal melt and the outer diameter gradually decreases downward.
  • the vertex angle ⁇ of the cone formed by the atomization water is preferably about 10° or more and 40° or less, more preferably about 15° or more and 35° or less. According to this, a metal powder for powder metallurgy having a composition as described above can be reliably produced.
  • the metal melt can be cooled particularly quickly. Due to this, a powder having high quality can be obtained in a wide alloy composition range.
  • the cooling rate when cooling the metal melt in the atomization method is preferably 1 x 10 4 °C/s or more, more preferably 1 x 10 5 °C/s or more.
  • the thus obtained metal powder for powder metallurgy may be classified as needed.
  • classification method include dry classification such as sieving classification, inertial classification, and centrifugal classification, and wet classification such as sedimentation classification.
  • binder examples include polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymers, acrylic resins such as polymethyl methacrylate and polybutyl methacrylate, styrenic resins such as polystyrene, polyesters such as polyvinyl chloride, polyvinylidene chloride, polyamide, polyethylene terephthalate, and polybutylene terephthalate, various resins such as polyether, polyvinyl alcohol, polyvinylpyrrolidone, and copolymers thereof, and various organic binders such as various waxes, paraffins, higher fatty acids (such as stearic acid), higher alcohols, higher fatty acid esters, and higher fatty acid amides. These can be used alone or by mixing two or more types thereof.
  • polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymers
  • acrylic resins such as polymethyl methacryl
  • the content of the binder is preferably about 2% by mass or more and 20% by mass or less, more preferably about 5% by mass or more and 10% by mass or less with respect to the total amount of the kneaded material.
  • a plasticizer may be added as needed.
  • the plasticizer include phthalate esters (such as DOP, DEP, and DBP), adipate esters, trimellitate esters, and sebacate esters. These can be used alone or by mixing two or more types thereof.
  • any of a variety of additives such as a lubricant, an antioxidant, a degreasing accelerator, and a surfactant can be added as needed.
  • the kneading conditions vary depending on the respective conditions such as the metal composition or the particle diameter of the metal powder for powder metallurgy to be used, the composition of the binder, and the blending amount thereof.
  • the kneading temperature can be set to about 50°C or higher and 200°C or lower
  • the kneading time can be set to about 15 minutes or more and 210 minutes or less.
  • the kneaded material is formed into a pellet (small particle) as needed.
  • the particle diameter of the pellet is set to, for example, about 1 mm or more and 15 mm or less.
  • a granulated powder may be produced.
  • the kneaded material, the granulated powder, and the like are examples of the composition to be subjected to the molding step described below.
  • the embodiment of the granulated powder according to the invention is directed to a granulated powder obtained by binding a plurality of metal particles to one another with a binder by subjecting the metal powder for powder metallurgy according to the invention to a granulation treatment.
  • binder to be used for producing the granulated powder examples include polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymers, acrylic resins such as polymethyl methacrylate and polybutyl methacrylate, styrenic resins such as polystyrene, polyesters such as polyvinyl chloride, polyvinylidene chloride, polyamide, polyethylene terephthalate, and polybutylene terephthalate, various resins such as polyether, polyvinyl alcohol, polyvinylpyrrolidone, and copolymers thereof, and various organic binders such as various waxes, paraffins, higher fatty acids (such as stearic acid), higher alcohols, higher fatty acid esters, and higher fatty acid amides. These can be used alone or by mixing two or more types thereof.
  • a binder containing a polyvinyl alcohol or polyvinylpyrrolidone is preferred.
  • These binder components have a high binding ability, and therefore can efficiently form the granulated powder even in a relatively small amount. Further, the thermal decomposability thereof is also high, and therefore, the binder can be reliably decomposed and removed in a short time during degreasing and firing.
  • the content of the binder is preferably about 0.2% by mass or more and 10% by mass or less, more preferably about 0.3% by mass or more and 5% by mass or less, further more preferably about 0.3% by mass or more and 2% by mass or less with respect to the total amount of the granulated powder.
  • a difference in size between the molded body and the degreased body, that is, so-called a shrinkage ratio is optimized, whereby a decrease in the dimensional accuracy of the finally obtained sintered body can be prevented.
  • any of a variety of additives such as a plasticizer, a lubricant, an antioxidant, a degreasing accelerator, and a surfactant may be added as needed.
  • Examples of the granulation treatment include a spray drying method, a tumbling granulation method, a fluidized bed granulation method, and a tumbling fluidized bed granulation method.
  • a solvent which dissolves the binder is used as needed.
  • the solvent include inorganic solvents such as water and carbon tetrachloride, and organic solvents such as ketone-based solvents, alcohol-based solvents, ether-based solvents, cellosolve-based solvents, aliphatic hydrocarbon-based solvents, aromatic hydrocarbon-based solvents, aromatic heterocyclic compound-based solvents, amide-based solvents, halogen compound-based solvents, ester-based solvents, amine-based solvents, nitrile-based solvents, nitro-based solvents, and aldehyde-based solvents, and one type or a mixture of two or more types selected from these solvents is used.
  • the average particle diameter of the granulated powder is not particularly limited, but is preferably about 10 ⁇ m or more and 200 ⁇ m or less, more preferably about 20 ⁇ m or more and 100 ⁇ m or less, further more preferably about 25 ⁇ m or more and 60 ⁇ m or less.
  • the granulated powder having such a particle diameter has favorable fluidity, and can more faithfully reflect the shape of a molding die.
  • the average particle diameter can be obtained as a particle diameter when the cumulative amount obtained by cumulating the percentages of the particles from the smaller diameter side reaches 50% in a cumulative particle size distribution on a mass basis obtained by laser diffractometry.
  • the kneaded material or the granulated powder is molded, whereby a molded body having the same shape as that of a target sintered body is produced.
  • the method for producing a molded body is not particularly limited, and for example, any of a variety of molding methods such as a powder compacting (compression molding) method, a metal injection molding (MIM) method, and an extrusion molding method can be used.
  • the molding conditions in the case of a powder compacting method among these methods are preferably such that the molding pressure is about 200 MPa or more and 1000 MPa or less (2 t/cm 2 or more and 10 t/cm 2 or less), which vary depending on the respective conditions such as the composition and the particle diameter of the metal powder for powder metallurgy to be used, the composition of the binder, and the blending amount thereof.
  • the molding conditions in the case of a metal injection molding method are preferably such that the material temperature is about 80°C or higher and 210°C or lower, and the injection pressure is about 50 MPa or more and 500 MPa or less (0.5 t/cm 2 or more and 5 t/cm 2 or less), which vary depending on the respective conditions.
  • the molding conditions in the case of an extrusion molding method are preferably such that the material temperature is about 80°C or higher and 210°C or lower, and the extrusion pressure is about 50 MPa or more and 500 MPa or less (0.5 t/cm 2 or more and 5 t/cm 2 or less), which vary depending on the respective conditions.
  • the thus obtained molded body is in a state where the binder is uniformly distributed in spaces between the particles of the metal powder.
  • the shape and size of the molded body to be produced are determined in anticipation of shrinkage of the molded body in the subsequent degreasing step and firing step.
  • the thus obtained molded body is subjected to a degreasing treatment (binder removal treatment), whereby a degreased body is obtained.
  • the binder is decomposed by heating the molded body, whereby the binder is removed from the molded body. In this manner, the degreasing treatment is performed.
  • Examples of the degreasing treatment include a method of heating the molded body and a method of exposing the molded body to a gas capable of decomposing the binder.
  • the conditions for heating the molded body are preferably such that the temperature is about 100°C or higher and 750°C or lower and the time is about 0.1 hours or more and 20 hours or less, and more preferably such that the temperature is about 150°C or higher and 600°C or lower and the time is about 0.5 hours or more and 15 hours or less, which slightly vary depending on the composition and the blending amount of the binder.
  • the degreasing of the molded body can be necessarily and sufficiently performed without sintering the molded body. As a result, it is possible to reliably prevent the binder component from remaining inside the degreased body in a large amount.
  • the atmosphere when the molded body is heated is not particularly limited, and an atmosphere of a reducing gas such as hydrogen, an atmosphere of an inert gas such as nitrogen or argon, an atmosphere of an oxidative gas such as air, a reduced pressure atmosphere obtained by reducing the pressure of such an atmosphere, or the like can be used.
  • a reducing gas such as hydrogen
  • an atmosphere of an inert gas such as nitrogen or argon
  • an atmosphere of an oxidative gas such as air
  • a reduced pressure atmosphere obtained by reducing the pressure of such an atmosphere, or the like can be used.
  • Examples of the gas capable of decomposing the binder include ozone gas.
  • this degreasing step into a plurality of steps in which the degreasing conditions are different, and performing the plurality of steps, the binder in the molded body can be more rapidly decomposed and removed so that the binder does not remain in the molded body.
  • the degreased body may be subjected to a machining process such as grinding, polishing, or cutting.
  • the degreased body has a relatively low hardness and relatively high plasticity, and therefore, the machining process can be easily performed while preventing the degreased body from losing its shape. According to such a machining process, a sintered body having high dimensional accuracy can be easily obtained in the end.
  • the degreased body obtained in the above step (C) is fired in a firing furnace, whereby a sintered body is obtained.
  • the firing temperature varies depending on the composition, the particle diameter, and the like of the metal powder for powder metallurgy used in the production of the molded body and the degreased body, but is set to, for example, about 980°C or higher and 1330°C or lower, and preferably set to about 1050°C or higher and 1260°C or lower.
  • the firing time is set to 0.2 hours or more and 7 hours or less, but is preferably set to about 1 hour or more and 6 hours or less.
  • the firing temperature or the below-described firing atmosphere may be changed in the middle of the step.
  • the firing temperature is a relatively low temperature, it is easy to control the heating temperature in the firing furnace to be a fixed temperature, and therefore, it is also easy to maintain the temperature of the degreased body at a fixed temperature. As a result, a more homogeneous sintered body can be produced.
  • the firing temperature as described above is a temperature which can be sufficiently realized using a common firing furnace, and therefore, an inexpensive firing furnace can be used, and also the running cost can be kept low. In other words, in the case where the temperature exceeds the above-mentioned firing temperature, it is necessary to employ an expensive firing furnace using a special heat resistant material, and also the running cost may be increased.
  • the atmosphere when performing firing is not particularly limited, however, in consideration of prevention of significant oxidation of the metal powder, an atmosphere of a reducing gas such as hydrogen, an atmosphere of an inert gas such as argon, a reduced pressure atmosphere obtained by reducing the pressure of such an atmosphere, or the like is preferably used.
  • the thus obtained sintered body has a high density and excellent mechanical properties. That is, a sintered body produced by molding a composition containing the metal powder for powder metallurgy according to the invention and a binder, followed by degreasing and sintering has a higher relative density than a sintered body obtained by sintering a metal powder in the related art. Therefore, according to the invention, a sintered body having a high density which could not be obtained unless an additional treatment such as an HIP treatment is performed can be realized without performing an additional treatment.
  • the relative density can be expected to be increased by 2% or more as compared with the related art, which slightly varies depending on the composition of the metal powder for powder metallurgy.
  • the relative density of the obtained sintered body can be expected to be, for example, 97% or more (preferably 98% or more, more preferably 98.5% or more).
  • the sintered body having a relative density within such a range has excellent mechanical properties comparable to those of ingot materials although it has a shape as close as possible to a desired shape by using a powder metallurgy technique, and therefore, the sintered body can be applied to a variety of machine parts, structural parts, and the like with virtually no post-processing.
  • the tensile strength and the 0.2% proof stress of a sintered body produced by molding a composition containing the metal powder for powder metallurgy according to the invention and a binder, followed by degreasing and sintering are higher than those of a sintered body obtained by performing sintering in the same manner using a metal powder in the related art. This is considered to be because by optimizing the alloy composition and the crystal structure of the particle, the sinterability of the metal powder is enhanced, and thus, the mechanical properties of a sintered body to be produced using the metal powder are enhanced.
  • the sintered body produced as described above has a high surface hardness.
  • the Vickers hardness of the surface of the sintered body is expected to be 570 or more and 1200 or less, which slightly varies depending on the composition of the metal powder for powder metallurgy, and further is expected to be preferably 600 or more and 1000 or less.
  • the sintered body having such a hardness has particularly high durability.
  • the sintered body has a sufficiently high density and excellent mechanical properties even without performing an additional treatment, however, in order to further increase the density and enhance the mechanical properties, a variety of additional treatments may be performed.
  • an additional treatment of increasing the density such as the HIP treatment described above may be performed, and also a variety of quenching treatments, a variety of sub-zero treatments, a variety of tempering treatments, and the like may be performed. These additional treatments may be performed alone or two or more treatments thereof may be performed in combination.
  • this treatment is preferably used, for example, when a sintered body containing a martensite crystal structure is produced.
  • the sub-zero treatment is a treatment in which an austenite crystal structure which is not transformed into a martensite crystal structure by the quenching treatment and is retained is transformed into martensite by cooling.
  • the retained austenite crystal structure is often transformed into martensite over time, however, at this time, the volume of the sintered body changes. Therefore, a problem occurs that the size of the sintered body changes over time. Therefore, by performing the sub-zero treatment after the quenching treatment, the retained austenite crystal structure can be transformed into martensite partly forcibly, and thus, the occurrence of the problem that the size changes over time can be prevented.
  • the temperature is about 0°C or lower and the time is about 0.2 hours or more and 3 hours or less.
  • the tempering treatment is a treatment in which the sintered body having undergone the quenching treatment is heated again at a lower temperature than in the quenching treatment.
  • the temperature is about 100°C or higher and 200°C or lower and the time is about 0.3 hours or more and 5 hours or less.
  • the content of C in the final sintered body may change within the range of 5% or more and 100% or less (preferably within the range of 30% or more and 100% or less) of the content of C in the metal powder for powder metallurgy, which varies depending on the conditions for the step or the conditions for the treatment.
  • the content of O in the final sintered body may change within the range of 1% or more and 50% or less (preferably within the range of 3% or more and 50% or less) of the content of O in the metal powder for powder metallurgy, which varies depending on the conditions for the step or the conditions for the treatment.
  • the produced sintered body may be subjected to an HIP treatment as part of the additional treatments to be performed as needed, however, even if the HIP treatment is performed, a sufficient effect is not exhibited in many cases.
  • the density of the sintered body can be further increased, however, in the first place, the density of the sintered body obtained according to the invention has already been sufficiently increased at the end of the firing step. Therefore, even if the HIP treatment is further performed, densification hardly proceeds any further.
  • the material to be treated may be contaminated, the composition or the physical properties of the material to be treated may unintentionally change accompanying the contamination, or the color of the material to be treated may change accompanying the contamination.
  • residual stress is generated or increased in the material to be treated, and a problem such as a change in the shape or a decrease in the dimensional accuracy may occur as the residual stress is released over time.
  • a sintered body having a sufficiently high density can be produced without performing such an HIP treatment, and therefore, a sintered body having an increased density and also an increased strength can be obtained in the same manner as in the case of performing an HIP treatment.
  • Such a sintered body is less contaminated and discolored, and also an unintended change in the composition or physical properties, or the like occurs less, and also a problem such as a change in the shape or a decrease in the dimensional accuracy occurs less. Therefore, according to the invention, a sintered body having high mechanical strength and dimensional accuracy, and excellent durability can be efficiently produced.
  • the sintered body produced according to the invention requires almost no additional treatments for enhancing the mechanical properties, and therefore, the composition and the crystal structure tend to become uniform in the entire sintered body. Due to this, the sintered body has high structural anisotropy and therefore has excellent durability against a load from every direction regardless of its shape.
  • the porosity near the surface thereof is often relatively lower than inside the sintered body.
  • the reason therefor is not clear, however, one of the reasons is that by the addition of the first element and the second element, the sintering reaction more easily proceeds near the surface of the molded body than inside the molded body.
  • A2-A1 is preferably 0.1% or more and 3% or less, more preferably 0.2% or more and 2% or less.
  • the sintered body showing the value of A2-A1 within the above range not only has necessary and sufficient mechanical strength, but also can easily flatten the surface. That is, by polishing the surface of such a sintered body, a surface having high specularity can be obtained.
  • Such a sintered body having high specularity not only has high mechanical strength, but also has excellent aesthetic properties. Therefore, such a sintered body is favorably used also for application requiring excellent aesthetic appearance.
  • the porosity A1 near the surface of the sintered body refers to a porosity in a 25- ⁇ m radius region centered on the position at a depth of 50 ⁇ m from the surface of the cross section of the sintered body.
  • the porosity A2 inside the sintered body refers to a porosity in a 25- ⁇ m radius region centered on the position at a depth of 300 ⁇ m from the surface of the cross section of the sintered body.
  • the metal powder for powder metallurgy, the compound, the granulated powder, and the sintered body according to the invention have been described with reference to preferred embodiments, however, the invention is not limited thereto.
  • the sintered body according to the invention is used for, for example, parts for transport machinery such as parts for automobiles, parts for bicycles, parts for railroad cars, parts for ships, parts for airplanes, and parts for space transport machinery (such as rockets); parts for electronic devices such as parts for personal computers and parts for mobile phone terminals; parts for electrical devices such as refrigerators, washing machines, and cooling and heating machines; parts for machines such as machine tools and semiconductor production devices; parts for plants such as atomic power plants, thermal power plants, hydroelectric power plants, oil refinery plants, and chemical complexes; parts for timepieces, metallic tableware, jewels, ornaments such as frames for glasses, and all other sorts of structural parts.
  • parts for transport machinery such as parts for automobiles, parts for bicycles, parts for railroad cars, parts for ships, parts for airplanes, and parts for space transport machinery (such as rockets); parts for electronic devices such as parts for personal computers and parts for mobile phone terminals; parts for electrical devices such as refrigerators, washing machines, and cooling and heating machines; parts for machines such as machine tools and semiconductor production
  • the obtained degreased body was fired under the following firing conditions, whereby a sintered body was obtained.
  • the shape of the sintered body was determined to be a cylinder with a diameter of 10 mm and a thickness of 5 mm.
  • the obtained sintered body was subjected to a quenching treatment under the following conditions.
  • the sintered body having undergone the quenching treatment was subjected to a sub-zero treatment under the following conditions.
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 1 or 2, respectively.
  • the sintered bodies of sample Nos. 36 and 67 were obtained by performing an HIP treatment under the following conditions after firing. Further, the sintered bodies of sample Nos. 28 to 30 and 57 to 59 were obtained by using the metal powder produced by a gas atomization method, respectively, and indicated by "gas" in the column of Remarks in Tables 1 and 2.
  • Each sintered body contained very small amounts of impurities, but the description thereof in Tables 1 and 2 is omitted.
  • the sintered body having undergone the quenching treatment was subjected to a sub-zero treatment under the following conditions.
  • the sintered body having undergone the sub-zero treatment was subjected to a tempering treatment under the following conditions.
  • Sintered bodies were obtained in the same manner as in the case of sample No. 68 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 3, respectively.
  • the sintered body of sample No. 84 was obtained by performing an HIP treatment under the following conditions after firing.
  • Each sintered body contained very small amounts of impurities, but the description thereof in Table 3 is omitted.
  • the average number of the Fe-based alloy crystals was 1 or more and 5 or less. Specifically, the lowest average number was 1.2 and the highest average number was 4.6.
  • the circle equivalent diameter of the Fe-based alloy crystal was 1% or more and 100% or less the circle equivalent diameter of the particle. Specifically, the lowest ratio of the circle equivalent diameter of the Fe-based alloy crystal to the circle equivalent diameter of the particle was 2%, and the highest ratio thereof was 84%.
  • the average number of the Fe-based alloy crystals was 6 or more. Specifically, the lowest average number was 8.4 and the highest average number was 256.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the Vickers hardness was measured in accordance with the Vickers hardness test method specified in JIS Z 2244 (2009).
  • the measured hardness was evaluated according to the following evaluation criteria.
  • the fatigue strength was measured in accordance with the test method specified in JIS Z 2273 (1978).
  • the waveform of an applied load corresponding to a repeated stress was set to an alternating sine wave, and the minimum/maximum stress ratio (minimum stress/maximum stress) was set to 0.1. Further, the repeated frequency was set to 30 Hz, and the repeat count was set to 1 x 10 7 .
  • the measured fatigue strength was evaluated according to the following evaluation criteria.
  • Table 4 Metal powder Evaluation results of sintered body Sample No. - Average particle diameter Relative density Vickers hardness Tensile strength 0.2% proof stress Elongation Fatigue strength ⁇ m % - - - - - No. 1 Example 3.86 99.5 A A A A A A No. 2 Example 3.79 98.2 A B B B B No. 3 Example 3.84 98.4 A B B B B No. 4 Example 3.92 99.3 A A A A A No. 5 Example 4.02 99.4 A A A A A No. 6 Example 3.68 97.8 A B B B B No. 7 Example 3.77 98.2 A B B B B No. 8 Example 3.81 98.8 A A A B B No.
  • Example 3.85 98.9 A A A B B No. 10 Example 4.05 98.5 A B B B B No. 11
  • Example 3.92 98.6 A B B B B No. 13 Example 3.74 97.5 A B B C C No. 14
  • Example 3.86 97.4 A B B B B No. 16 Example 3.88 97.1 A B B B B No. 17
  • Example 3.84 97.0 A C C B B No. 19 Example 3.84 97.2 A B B C C No. 20
  • Example 3.76 97.3 A B B B B No. 21 Example 3.76 97.3 A B B B B No.
  • Example 4.05 97.6 A B B B B No. 45 Example 4.14 99.3 A A A B B No. 46
  • Example 10.8 98.9 A C C C No. 50 Example 4.78 95.9 A D D B B No. 51
  • Example 4.36 95.7 A D D D D No. 53 Example 4.12 95.6 A D D D D No. 54
  • Example 4.23 99.1 A B B B B No. 56 Example 3.87 99.3 A A A A A A A No.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example (excluding the sintered bodies having undergone the HIP treatment). Further, it was also confirmed that there is a significant difference in properties such as tensile strength, 0.2% proof stress, elongation, and fatigue strength between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example (excluding the sintered bodies having undergone the HIP treatment).
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 7, respectively.
  • the sintered body of sample No. 105 was obtained by performing an HIP treatment under the following conditions after firing.
  • Each sintered body contained very small amounts of impurities, but the description thereof in Table 7 is omitted.
  • the average number of the Fe-based alloy crystals was 1 or more and 5 or less.
  • the circle equivalent diameter of the Fe-based alloy crystal was 1% or more and 100% or less the circle equivalent diameter of the particle.
  • the average number of the Fe-based alloy crystals was 6 or more.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the Vickers hardness was measured in accordance with the Vickers hardness test method specified in JIS Z 2244 (2009).
  • the measured hardness was evaluated according to the evaluation criteria described in 3.2.
  • the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example (excluding the sintered body having undergone the HIP treatment). Further, it was also confirmed that there is a significant difference in properties such as tensile strength, 0. 2% proof stress, elongation, and fatigue strength between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example (excluding the sintered body having undergone the HIP treatment).
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 9, respectively.
  • a metal powder, a Ti powder having an average particle diameter of 40 ⁇ m, and a Nb powder having an average particle diameter of 25 ⁇ m were mixed, whereby a mixed powder was prepared.
  • each of the mixing amounts of the metal powder, the Ti powder, and the Nb powder was adjusted so that the composition of the mixed powder was as shown in Table 9.
  • Each sintered body contained very small amounts of impurities, but the description thereof in Table 9 is omitted.
  • the average number of the Fe-based alloy crystals was 1 or more and 5 or less.
  • the circle equivalent diameter of the Fe-based alloy crystal was 1% or more and 100% or less the circle equivalent diameter of the particle.
  • the average number of the Fe-based alloy crystals was 6 or more.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the Vickers hardness was measured in accordance with the Vickers hardness test method specified in JIS Z 2244 (2009).
  • the measured hardness was evaluated according to the evaluation criteria described in 3.2.
  • the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example. It was also confirmed that there is a significant difference in properties such as tensile strength, 0.2% proof stress, elongation, and fatigue strength between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example.
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 11, respectively.
  • Table 11 Metal powder for powder metallurgy Alloy composition E1/E2 E1+E2 (E1+E2) /Si (E1+E2) /C Mn+Ni Remarks Sample No. - Cr C Si E1 (Nb) E2 (Ta) Mn Ni Cu O Fe mass% - mass% - - mass% - No. 120
  • Each sintered body contained very small amounts of impurities, but the description thereof in Table 11 is omitted.
  • the average number of the Fe-based alloy crystals was 1 or more and 5 or less.
  • the circle equivalent diameter of the Fe-based alloy crystal was 1% or more and 100% or less the circle equivalent diameter of the particle.
  • the average number of the Fe-based alloy crystals was 6 or more.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the Vickers hardness was measured in accordance with the Vickers hardness test method specified in JIS Z 2244 (2009).
  • the measured hardness was evaluated according to the evaluation criteria described in 3.2.
  • the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example. It was also confirmed that there is a significant difference in properties such as tensile strength, 0.2% proof stress, elongation, and fatigue strength between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example.
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 13, respectively.
  • Table 13 Metal powder for powder metallurgy Alloy composition E1/E2 E1+E2 (E1+E2)/Si (E1+E2)/C Mn+Ni Remarks Sample No. - Cr C Si E1 (Y) E2 (Nb) Mn Ni Cu O Fe mass% - mass% - - mass% - No. 133
  • Each sintered body contained very small amounts of impurities, but the description thereof in Table 13 is omitted.
  • the average number of the Fe-based alloy crystals was 1 or more and 5 or less.
  • the circle equivalent diameter of the Fe-based alloy crystal was 1% or more and 100% or less the circle equivalent diameter of the particle.
  • the average number of the Fe-based alloy crystals was 6 or more.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the Vickers hardness was measured in accordance with the Vickers hardness test method specified in JIS Z 2244 (2009).
  • the measured hardness was evaluated according to the evaluation criteria described in 3.2.
  • the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
  • Table 14 Metal powder Evaluation results of sintered body Sample No. - Average particle diameter Relative density Vickers hardness Tensile strength 0.2% proof stress Elongation Fatigue strength ⁇ m % - - - - - No. 133 Example 4.37 99.0 A A A A A No. 134 Example 5.81 98.3 A B B B B No. 135 Example 3.31 98.4 A B B B B No. 136 Example 9.68 98.1 A B B B C No. 137 Example 4.65 98.6 A B B B B No. 138 Example 13.78 97.8 A B B B B No. 139 Example 3.64 98.9 A A A A B No. 140 Example 2.05 97.9 A B B C C No.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example. It was also confirmed that there is a significant difference in properties such as tensile strength, 0.2% proof stress, elongation, and fatigue strength between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example.
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 15, respectively.
  • Table 15 Metal powder for powder metallurgy Alloy composition E1/E2 E1+E2 (E1+E2)/Si (E1+E2)/C Mn+Ni Remarks Sample No. - Cr C Si E1 (V) E2 (Nb) Mn Ni Cu O Fe mass% - mass% - - mass% - No. 146
  • Example 13.09 1.03 0.81 0.03 0.03 0.58 0.17 ⁇ 0.01 0.28 remainder 1.00 0.06 0.07 0.06 0.75 No.
  • Each sintered body contained very small amounts of impurities, but the description thereof in Table 15 is omitted.
  • the average number of the Fe-based alloy crystals was 1 or more and 5 or less.
  • the circle equivalent diameter of the Fe-based alloy crystal was 1% or more and 100% or less the circle equivalent diameter of the particle.
  • the average number of the Fe-based alloy crystals was 6 or more.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the Vickers hardness was measured in accordance with the Vickers hardness test method specified in JIS Z 2244 (2009).
  • the measured hardness was evaluated according to the evaluation criteria described in 3.2.
  • the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example. It was also confirmed that there is a significant difference in properties such as tensile strength, 0.2% proof stress, elongation, and fatigue strength between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example.
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 17, respectively.
  • Table 17 Metal powder for powder metallurgy Alloy composition E1/E2 E1+E2 (E1+E2)/Si (E1+E2)/C Mn+Ni Remarks Sample No. - Cr C Si E1 (Ti) E2 (Zr) Mn Ni Cu O Fe mass% - mass% - - mass% - No. 159
  • Each sintered body contained very small amounts of impurities, but the description thereof in Table 17 is omitted.
  • the average number of the Fe-based alloy crystals was 1 or more and 5 or less.
  • the circle equivalent diameter of the Fe-based alloy crystal was 1% or more and 100% or less the circle equivalent diameter of the particle.
  • the average number of the Fe-based alloy crystals was 6 or more.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the measured hardness was evaluated according to the evaluation criteria described in 3.2.
  • the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example. It was also confirmed that there is a significant difference in properties such as tensile strength, 0.2% proof stress, elongation, and fatigue strength between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example.
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 19, respectively.
  • Table 19 Metal powder for powder metallurgy Alloy composition E1/E2 E1+E2 (E1+E2)/Si (E1+E2)/C Mn+Ni Remarks Sample No. - Cr C Si E1 (Zr) E2 (Ta) Mn Ni Cu O Fe mass% - mass% - - mass% - No. 172
  • Example 12.83 0.87 0.73 0.07 0.12 0.11 0.17 ⁇ 0.01 0.29 remainder 0.58 0.19 0.26 0.22 0.28 No.
  • Each sintered body contained very small amounts of impurities, but the description thereof in Table 19 is omitted.
  • the average number of the Fe-based alloy crystals was 1 or more and 5 or less.
  • the circle equivalent diameter of the Fe-based alloy crystal was 1% or more and 100% or less the circle equivalent diameter of the particle.
  • the average number of the Fe-based alloy crystals was 6 or more.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the Vickers hardness was measured in accordance with the Vickers hardness test method specified in JIS Z 2244 (2009).
  • the measured hardness was evaluated according to the evaluation criteria described in 3.2.
  • the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example. It was also confirmed that there is a significant difference in properties such as tensile strength, 0.2% proof stress, elongation, and fatigue strength between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example.
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 21, respectively.
  • Table 21 Metal powder for powder metallurgy Alloy composition E1/E2 E1+E2 (E1+E2)/Si (E1+E2)/C Mn+Ni Remarks Sample No. - Cr C Si E1 (Zr) E2 (V) Mn Ni Cu O Fe mass% - mass% - - mass% - No. 185
  • Each sintered body contained very small amounts of impurities, but the description thereof in Table 21 is omitted.
  • the average number of the Fe-based alloy crystals was 1 or more and 5 or less.
  • the circle equivalent diameter of the Fe-based alloy crystal was 1% or more and 100% or less the circle equivalent diameter of the particle.
  • the average number of the Fe-based alloy crystals was 6 or more.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the Vickers hardness was measured in accordance with the Vickers hardness test method specified in JIS Z 2244 (2009).
  • the measured hardness was evaluated according to the evaluation criteria described in 3.2.
  • the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example. It was also confirmed that there is a significant difference in properties such as tensile strength, 0.2% proof stress, elongation, and fatigue strength between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example.
  • each of the sintered bodies of the respective sample Nos. shown in Table 23 was cut and the cross section was polished.
  • each of the sintered bodies of the respective sample Nos. shown in Table 23 was subjected to a barrel polishing treatment.
  • the specular gloss of the sintered body was measured in accordance with the method for measuring the specular gloss specified in JIS Z 8741 (1997).
  • the incident angle of light with respect to the surface of the sintered body was set to 60°, and as a reference plane for calculating the specular gloss, a glass having a specular gloss of 90 and a refractive index of 1.500 was used.
  • the measured specular gloss was evaluated according to the following evaluation criteria.
  • the sintered bodies corresponding to Example each have a higher specular gloss than the sintered bodies corresponding to Comparative Example. This is considered to be because the porosity near the surface of the sintered body is low, and therefore, light scattering is suppressed, however, the ratio of regular reflection is increased.

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  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Powder Metallurgy (AREA)

Claims (10)

  1. Poudre métallique pour métallurgie des poudres, comprenant des particules qui sont constituées des éléments suivants :
    Fe comme composant principal,
    Cr en proportion de 10 % en masse ou plus et de 30 % en masse ou moins,
    C en proportion de 0,1 % en masse ou plus et de 2 % en masse ou moins et
    Si en proportion de 0,2 % en masse ou plus et de 1,5 % en masse ou moins,
    éventuellement une teneur en Mn de 0,01 à 1,25 % en masse,
    éventuellement une teneur en Ni de 0,05 à 0,6 % en masse et
    éventuellement au moins l'un des éléments Mo, Pb, S et Al, dans laquelle :
    une teneur en Mo dans la particule est de 0,2 % en masse ou plus et de 0,8 % en masse ou moins, et/ou
    une teneur en Pb dans la particule est de 0,03 % en masse ou plus et de 0,5 % en masse ou moins, et/ou
    une teneur en S dans la particule est de 0,5 % en masse ou moins, et/ou
    une teneur en Al dans la particule est de 0,5 % en masse ou moins, et/ou
    une teneur en oxygène dans la poudre métallique est de 0,8 % en masse ou moins, et
    en outre éventuellement B, Se, Te, Pd, W, Co, N, Cu avec une teneur individuelle de chacun desdits éléments qui est inférieure à 0,1 % en masse et la teneur totale desdits éléments étant inférieure à 0,2 % en masse,
    des éléments d'impuretés tels que la teneur de chacun des éléments d'impuretés soit inférieure à la teneur de chacun de Fe, Cr, Si, du premier élément et du second élément et que la teneur de chacun des éléments d'impuretés soit inférieure à 0,03 % en masse et la teneur totale des éléments d'impuretés inférieure à 0,3 % en masse et dans laquelle,
    lorsqu'un élément choisi dans le groupe constitué de Ti, V, Y, Zr, Nb, Hf et Ta est défini comme premier élément et qu'un élément choisi dans le groupe constitué de Ti, V, Y, Zr, Nb, Hf et Ta et ayant un numéro de groupe dans le tableau périodique supérieur à celui du premier élément ou ayant le même numéro de groupe dans le tableau périodique que celui du premier élément et un numéro de période dans le tableau périodique supérieur à celui du premier élément est défini comme second élément,
    le premier élément est contenu en proportion de 0,01 % en masse ou plus et de 0,5 % en masse ou moins, et
    le second élément est contenu en proportion de 0,01 % en masse ou plus et de 0,5 % en masse ou moins, dans laquelle
    le nombre de cristaux dans la section transversale de la particule est de 1 ou plus et de 5 ou moins en moyenne.
  2. Poudre métallique pour métallurgie des poudres selon la revendication 1, dans laquelle :
    le cristal contient du Fe comme composant principal, et
    la particule comprend en outre une région (4) qui a un volume plus petit que celui du cristal et dans laquelle le rapport de la teneur en Si à la teneur en Fe est supérieur à celui du cristal.
  3. Poudre métallique pour métallurgie des poudres selon la revendication 1 ou la revendication 2, dans laquelle, dans la section transversale de la particule, le diamètre circulaire équivalent du cristal est de 1 % ou plus et de 100 % ou moins du diamètre circulaire équivalent de la particule.
  4. Poudre métallique pour métallurgie des poudres selon l'une quelconque des revendications 1 à 3, dans laquelle le cristal a une structure de cristal de type martensite.
  5. Poudre métallique pour métallurgie des poudres selon l'une quelconque des revendications 1 à 4, les particules contenant en outre au moins l'un des éléments Mo, Pb, S et Al, dans laquelle :
    une teneur en Mo dans la particule est de 0,2 % en masse ou plus et de 0,8 % en masse ou moins, et/ou
    une teneur en Pb dans la particule est de 0,03 % en masse ou plus et de 0,5 % en masse ou moins, et/ou
    une teneur en S dans la particule est de 0,5 % en masse ou moins, et/ou
    une teneur en Al dans la particule est de 0,5 % en masse ou moins, et/ou
    une teneur en oxygène dans la poudre métallique est de 0,8 % en masse ou moins.
  6. Composé comprenant la poudre métallique pour métallurgie des poudres selon l'une quelconque des revendications 1 à 5 et un liant qui lie les particules de la poudre métallique pour métallurgie des poudres les unes aux autres.
  7. Poudre granulée, dans laquelle la poudre granulée est obtenue par granulation de la poudre métallique pour métallurgie des poudres selon l'une quelconque des revendications 1 à 5.
  8. Procédé de production d'un corps fritté comprenant les étapes consistant à :
    préparer une composition de matériau comprenant la poudre métallique pour métallurgie des poudres selon l'une quelconque des revendications 1 à 5 et un liant ou la poudre granulée selon la revendication 7 ;
    mouler la composition de matériau en un corps moulé ;
    dégraisser le corps moulé obtenu pour éliminer le liant ;
    chauffer le corps dégraissé pour obtenir le corps fritté.
  9. Procédé de production d'un corps fritté selon la revendication 8, comprenant en outre au moins l'une des étapes consistant à :
    tremper le corps fritté pour transformer une structure de cristal de type austénite en une structure de cristal de type martensite ;
    traiter à une température en dessous de zéro à la suite de l'étape de trempe pour transformer la structure de cristal de type austénite résiduelle et, de préférence,
    traiter au revenu à la suite du traitement en dessous de zéro ;
    soumettre le corps fritté à un traitement de compression isostatique à chaud pour augmenter sa densité ; et
    polir la surface du corps fritté.
  10. Corps fritté qui peut être obtenu par le procédé selon la revendication 8 ou 9.
EP16152921.9A 2015-01-29 2016-01-27 Poudre de métal pour métallurgie des poudres, composé, poudre granulée et corps fritté Active EP3050985B1 (fr)

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CN105834413A (zh) 2016-08-10
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CN105834413B (zh) 2020-03-17
EP3050985A1 (fr) 2016-08-03

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