US20080025866A1 - Iron-Based Sintered Alloy, Iron-Based Sintered-Alloy Member and Production Process for Them - Google Patents

Iron-Based Sintered Alloy, Iron-Based Sintered-Alloy Member and Production Process for Them Download PDF

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Publication number
US20080025866A1
US20080025866A1 US11/578,591 US57859105A US2008025866A1 US 20080025866 A1 US20080025866 A1 US 20080025866A1 US 57859105 A US57859105 A US 57859105A US 2008025866 A1 US2008025866 A1 US 2008025866A1
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Prior art keywords
iron
powder
based sintered
alloy
mass
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Inventor
Mikio Kondoh
Nobuhiko Matsumoto
Toshitake Miyake
Shigehide Takemoto
Hitoshi Tanino
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Toyota Motor Corp
Toyota Central R&D Labs Inc
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Toyota Motor Corp
Toyota Central R&D Labs Inc
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Assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA, KABUSHIKI KAISHA TOYOTA CHUO KENKYUSHO reassignment TOYOTA JIDOSHA KABUSHIKI KAISHA ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KONDOH, MIKIO, MATSUMOTO, NOBUHIKO, MIYAKE, TOSHITAKE, TAKEMOTO, SHIGEHIDE, TANINO, HITOSHI
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    • 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
    • C22C33/0264—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements the maximum content of each alloying element not exceeding 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
    • C22C38/02—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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • 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
    • B22F2003/145—Both compacting and sintering simultaneously by warm compacting, below debindering temperature
    • 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

Definitions

  • the present invention relates to an iron-based sintered alloy and an iron-based sintered-alloy member, which are made by sintering a raw material powder including manganese (Mn) and (Si), and a production process for them.
  • the present invention relates to an iron-based sintered alloy, which is good in terms of the strength or dimensional stability and which makes Cu free or Ni free possible at reduced costs, and a production process for it (hereinafter, these inventions are referred to as a “first invention”)
  • the present invention relates to a high-density iron-based sintered-alloy member, which is of high strength and which is good in terms of the dimensional stability, and a production process for it (hereinafter, these inventions are referred to as a “second invention”).
  • iron-based sintered-alloy members which are sintered by heating powder compacts which are made by press forming raw material powders in which iron is adapted to be the major component.
  • iron-based sintered-alloy members it becomes possible to obtain products (sintered bodies), which are close to the final configurations, and accordingly it is possible to intend the reduction of the production costs or material costs of structural members by means of machining reduction or material-yield improvement, and the like. In order to do so, the strength and before/after-sintering dimensional stability of iron-based sintered-alloy members become important.
  • Fe—Cu—C-system iron-based sintered alloys which are made by sintering powder compacts composed of Fe—Cu—C-composition raw material powders, have been used heavily. It is because Cu is an element, which is effective for the strength improvement and before/after-sintering dimensional stableness of iron-based sintered alloys. Therefore, contrary to general iron/steel alloys, in the case of iron-based sintered alloys, Cu has been considered its essential component virtually.
  • iron-based sintered-alloy members which are sintered by heating powder compacts which are made by press forming raw material powders in which iron is adapted to be the major component.
  • iron-based sintered-alloy members it becomes possible to obtain products (sintered bodies), which are close to the final configurations, and accordingly it is possible to intend the reduction of the production costs or material costs of structural members by means of the reduction of machining or material-yield improvement, and the like.
  • the strength and before/after-sintering dimensional stability of iron-based sintered-alloy members become important. As measures therefor, the following methods have been adopted.
  • Fe—Cu—C-system-composition raw material powders it is to employ Fe—Cu—C-system-composition raw material powders. It is because Cu is an element, which is effective for the strength improvement and before/after-sintering dimensional stableness of iron-based sintered alloys. However, even when raw material powders with such compositions are employed, if the density of sintered bodies is low, no high-strength sintered bodies are desired after all. Moreover, iron-based sintered-alloy members, which include Cu, are not preferable in view of costs, in view of recycling, and the like, as well.
  • Patent Literature No. 3 Japanese Patent Publication No. 3309970
  • Patent Literature No. 4 Japanese Unexamined Patent Publication (KOKAI) No. 58-210147
  • Patent Literature No. 5 Domestic Re-publication of PCT International Publication for Patent Applications No. 10-510007
  • Non-patent Literature No. 2 “Effect of Sinter-Hardening on the Properties of High Temperature Sintered PM Steels,” Advances in Powder Metallurgy & Particulate Materials, MPIF, 2002, part 13, pp. 1-13
  • Non-patent Literature No. 3 “New focus on chromium may sidestep alloy cost increases,” MPR. September (2004), pp. 16-19
  • Cu powders are such that the unit costs are high and the employment amounts in iron-based sintered alloys, too, are great comparatively. Accordingly, they result in raising the production costs of iron-based sintered alloys naturally.
  • Cu is an element, which becomes the cause of hot brittleness of iron/steel materials, but is an element, which is difficult to remove by smelting, and the like. Consequently, iron-based sintered alloys employing Cu are such that the mingling into scraps, and so forth, is disliked, their recycling is difficult, and the employment of iron-based sintered alloys, which include Cu, are not necessarily preferable for environmental protection.
  • Ni is available as an element, which has been used heavily in iron-based sintered alloys.
  • Ni too similarly to Cu, is an element, which is effective for improving the strength, and the like, of iron-based sintered alloys.
  • Ni powders are expensive as well, and raise the production costs of iron-based sintered alloys.
  • Ni is an allergic element, and accordingly there are cases where its employment is not preferable.
  • Patent Literature Nos. 1 and 2 or Non-patent Literature No. 1 iron-based sintered alloys, in which, without employing Cu, Mn or Si is contained to intend strength improvement, and the like, are disclosed. However, they are at laboratorial levels definitely, and are different from the later-described present invention in the way of the compositions or addition methods, and the like, of Mn or Si.
  • Patent Literature No. 3 an ultra-high-density forming method for a powder compact is disclosed.
  • Patent Literature No. 4 and Patent Literature No. 5 an iron-based sintered alloy, which is made by compression forming and sintering a mixture powder of an Si—Mn—Fe-hardener pulverized powder and an iron powder, is disclosed.
  • iron-based sintered alloys disclosed in these patent publications are such that the compositions of C, Mn, Si, and the like, differ from the later-described iron-based sintered alloy of the present invention, and accordingly those, at which the both sides aim, differ.
  • Patent Literature No. 5 an iron-based sintered alloy, in which Mo is contained instead of Ni, is disclosed as well.
  • its strength is not necessarily sufficient, and it separately requires heat treatments, such as hardening and tempering, for further strengthening it highly. It is needless to say that such heat treatments require many times and man-hour requirements so that they have raised the production costs of iron-based sintered alloys.
  • Non-patent Literature No. 2 or 3 there is a disclosure to the effect that a high-strength iron-based sintered alloy (sinter-hardening steel) is can be obtained while omitting heat treatments after the sintering step, though.
  • Non-patent Literature No. 2 contrary to the present invention, does not disclose an iron-based sintered alloy in which Mn or Si is contained.
  • a sinter-hardening steel, which contains Cr, Mn, Si and Mo is disclosed.
  • its sinter-hardening steel is such that the hardenability is not sufficient, and does not necessarily demonstrate sufficiently high strength by the sintering step alone.
  • the present invention has been done in view of such circumstances, and it is an object to provide an iron-based sintered alloy, which can secure the mechanical characteristics, such as strength, or the before/after-sintering dimensional stability while suppressing the employment of Cu or Ni, though, and a production process for the same. Further, it is an object to provide an iron-based sintered alloy, which is can be produced at low costs while being good in terms of the strength and dimensional stability, though, and a production process for the same.
  • the present inventors have already established a method for obtaining an ultra-high-density powder compact by single pressing (aforementioned Patent Literature No. 3).
  • a method for obtaining an ultra-high-density powder compact by single pressing (aforementioned Patent Literature No. 3).
  • sintering this powder compact it becomes possible to obtain a high-density sintered body.
  • the present invention has been done in view of such circumstances, and it is an object to provide a high-density and high-strength iron-based sintered-alloy member, in which the occurrence of blistering during sintering is restrained, and which is good in terms of the before/after-sintering dimensional stability, and a production process for the same.
  • Patent Literature Nos. 1 and 2 or Non-patent Literature No.1 iron-based sintered alloys, in which Si is contained, are disclosed. However, they and the later-described present invention differ in many respects, such as the assignment making the assumption, the density of powder compact and the Si composition, and accordingly the both sides have no relation practically.
  • Patent Literature Nos. 4and5 iron-based sintered alloys, which are made by compression forming and sintering a mixture powder of an Si—Mn—Fe-hardener pulverized powder and an iron powder, are disclosed.
  • the assignment making the assumption, and the like differ from the later-described present invention, and accordingly there is not any practical relation between the both sides.
  • the present inventors in order to solve this assignment, studied earnestly and repeated trial and error, as a result, they newly found out that, by containing an appropriate amount of Mn and Si, an iron-based sintered alloy, which is of high strength and which is good in terms of the dimensional stability, is can be obtained, and arrived at completing the present invention.
  • an iron-based sintered alloy of the present invention is an iron-based sintered alloy, being completed by sintering a powder compact made by press forming a raw material powder composed of iron (Fe) mainly, and is characterized in that:
  • carbon (C) is 0.1-1.0% by mass
  • manganese (Mn) is 0.01-1.5% by mass
  • the sum of the Mn and silicon (Si) is 0.02-3.5% by mass
  • the major balance is Fe; and it is good in terms of the strength and dimensional stability.
  • the iron-based sintered alloy of the present invention without ever containing Cu, and the like, daringly, is of high strength and is good in terms of the dimensional stability by containing C, Mn and Si in appropriate amounts. Compared with the case of employing Cu, Mn and Si can be acquired inexpensively comparatively, besides, their employment amounts come off with being less comparatively. Therefore, in accordance with the iron-based sintered alloy of the present invention, the reduction of raw material costs becomes possible as well.
  • the mechanical characteristics (strength, ductility, and the like) of the iron-based sintered alloy of the present invention improve greatly, and it further makes one which is good in terms of the dimensional stability, too.
  • Mn is an effective element for the strength improvement of iron-based sintered alloys particularly.
  • the lower limit value of Mn can preferably be 0.01% by mass, 0.05% by mass, 0.1% by mass, 0.2% by mass, and 0.3% by mass.
  • Mn is less excessively, its effect is poor.
  • the iron-based sintered alloy which is of sufficient strength, can be obtained.
  • the upper limit value of Mn can preferably be 2% by mass, 1.5% by mass, 1.2% by mass (especially, less than 1.2% by mass), 1.15% by mass, 1.1% by mass, 1.0% by mass (especially, less than 1.0% by mass), 0.9% by mass, and 0.8% by mass.
  • Mn becomes excessive, the elongation of the iron-based sintered alloy decreases so that the toughness degrades, and the dimensional change increases as well so that the dimensional stability is hampered.
  • the compositional range of Mn can preferably be 0.2-2% by mass, and further 0.3-1.5% by mass. Note that, in the present description, it should be notified that the respective upper limit values and respective lower limit values of the component elements are combinable arbitrarily unless otherwise specified particularly.
  • Si contributes to the strength improvement of iron-based sintered alloys as well, but contributes greatly to the dimensional stability of iron-based sintered alloys especially. In particular, this tendency is great when Si coexists with Mn. Mn acts in such a tendency that increases the dimension of iron-based sintered alloys, on the contrary, Si acts in such a tendency that decreases the dimension of iron-based sintered alloys. It is believed that, by the fact that both elements coexist, these tendencies cancel with each other so that the dimensional stability of the iron-based sintered alloy can be secured.
  • the lower limit value of Si can preferably be 0.1% by mass, 0.2% by mass, and 0.3% by mass.
  • the upper limit value of Si can preferably be 3% by mass, 2.5% by mass, 2% by mass, and 1.2% by mass.
  • the compositional range of Si can preferably be 0.1-3% by mass, and further 0.2-2% by mass.
  • the iron-based sintered alloy of the present invention includes an appropriate amount of C.
  • C is an important strengthening element for iron-based sintered alloys. Not to mention that C diffuses during sintering so that iron-based sintered alloys are solution strengthened, by including C in an appropriate amount, the heat treatments, such as the hardening and tempering of iron-based sintered alloys, become possible, and thereby it is possible to improve the mechanical characteristics of iron-based sintered alloys even more greatly.
  • C is less excessively, its effect is poor; and, when C becomes excessive, the ductility degrades.
  • the lower limit value of C can preferably be 0.1% by mass, 0.2% by mass, 0.3% by mass, 0.35% by mass, and 0.4% by mass.
  • the upper limit value of C can preferably be 1.0% by mass, 0.8% by mass, 0.7% by mass, and 0.7% by mass.
  • the compositional range of C can preferably be 0.1-1.0% by mass, and further 0.2-0.8% by mass.
  • the iron-based sintered alloy can be obtained, iron-based sintered alloy which has made the strength and toughness, which are said to be in a conflicting relationship, compatible at a higher level.
  • alloying elements such as molybdenum (Mo), chromium (Cr) and nickel (Ni).
  • Mo molybdenum
  • Cr chromium
  • Ni nickel
  • Mo molybdenum
  • Cr chromium
  • Ni nickel
  • one member or more of Cr or Mo is especially preferable as an alloying element.
  • the details of the iron-based sintered alloy, which includes these alloying elements, will be described later.
  • the iron-based sintered alloy of the present invention without ever having Cu contained, is of high strength, and is good in terms of the dimensional stability.
  • the iron-based sintered alloy of the present invention is a Cu-free iron-based sintered alloy, which does not include Cu substantially, the recyclability of the iron-based sintered alloy improves so that it is preferable in view of environmental protections. Moreover, by suppressing the employment of expensive Cu, the cost reduction of the iron-based sintered alloy can be intended. Furthermore, when the iron-based sintered alloy is Cu-free, the hot brittleness of the iron-based sintered alloy, which results from Cu, can be avoided.
  • Ni is an effective element for highly intensifying iron-based sintered alloys, and it is less likely that the recyclability, and the like, become problems.
  • Ni is said to be an allergic element, and accordingly there are cases where the employment is not preferable. Therefore, it is preferable that the iron-based sintered alloy of the present invention can be an Ni-free iron-based sintered alloy. Therefore, it seems that a Cu-free or Ni-free iron-based sintered alloy like the present invention is such that, as an environmentally harmonizing-type high-strength sintered alloy, its utilization range will expand all the more from now on.
  • the iron-based sintered alloy which is set forth in the present description, according to the present invention does not exclude the containment of Cu or Ni at all.
  • the green density of powder compact or the sintered density of iron-based sintered alloy does not necessarily matter.
  • the iron-based sintered alloy is a wide concept that includes iron-based sintered-alloy members.
  • the strength can preferably be 900 MPa or more, 1,000 MPa or more, 1, 100 MPa or more, 1,200 MPa or more, 1,300 MPa or more, and further 1,400 MPa or more, by transverse rupture strength.
  • the dimensional stability can preferably be within ⁇ 1%, within ⁇ 0.5%, within ⁇ 0.3%, and further within ⁇ 0.1%, by before/after sintering dimensional change rate.
  • the “iron-based sintered alloy,” set forth in the present description is such that its form does not matter, for example, can even be materials, such as ingot-shaped, rod-shaped, tube-shaped plate-shaped ones, and can even be final configurations or structural members (iron-based sintered-alloy members), which are close to them.
  • the aforementioned iron-based sintered alloy for example, can be produced by means of the following production method of the present invention.
  • a production process of the present invention for an iron-based sintered alloy by which the above-described iron-based sintered alloy is obtainable after the following sintering step, is characterized in that is completed by being equipped with: a forming step of making a powder compact by press forming a raw material, in which an Fe-system powder, composed of at least one of pure iron and iron alloy, is mixed with a strengthening powder, containing manganese (Mn) and silicon (Si) as being a powder as a whole; and a sintering step of heating the powder compact to sinter it.
  • Mn manganese
  • Si silicon
  • Mn and Si which are important in view of securing the strength and dimensional stability of the iron-based sintered alloy of the present invention, additional remarks are made.
  • Mn and Si in addition to C, phosphorus (P) and sulfur (S), are referred to as the five elements of steels, and are general strengthening elements in melt produced iron/steel materials.
  • P phosphorus
  • S sulfur
  • Mn and Si have hardly been employed in the field of iron-based sintered alloys.
  • Mn and Si are such that the affinity to oxygen is high extremely so that they are likely to make oxides. Accordingly, it has been believed in general that they make iron-based sintered alloys, in which oxides intervene in the metallic structures, so that the mechanical characteristics deteriorate.
  • Such circumstances are remarkable when adding Mn and Si into raw material powders as another powder independently of an Fe-system powder.
  • the sintering step was carried out by heating a powder compact, which included Mn and Si, in an oxidation preventive atmosphere, which could restrain the oxidation of Mn and Si sufficiently, (heating step).
  • the heating step in this sintering step can be carried out in a reducing atmosphere in which a hydrogen (H2) gas is intermingled into an inert gas, however, when carrying it out in an ultra-low-oxygen-partial-pressure inert gas atmosphere whose oxygen partial pressure is equivalent to 10 ⁇ 19 Pa or less, it is much safer and the cost reduction of the iron-based sintered alloy can be intended.
  • H2 hydrogen
  • the present inventors carried out the sintering step within such an ultra-low-oxygen-partial-pressure inert gas atmosphere, and obtained the above-described iron-based sintered alloy of the present invention. The details of this will be described later.
  • an iron-based sintered alloy of the present invention is an iron-based sintered alloy being completed by sintering a powder compact made by press forming a raw material powder composed of iron (Fe) mainly, and is characterized in that: when the entirety is taken as 100% by mass, Cr is 0.2-5.0% by mass; Mo is 0.1-1% by mass; Mn is 0.1-1.2% by mass; Si is 0.1-1.2% by mass; C is 0.1-0.7% by mass; and the major balance is composed of Fe; and it is good in terms of the strength and dimensional stability.
  • the iron-based sintered alloy of the present invention contains alloying elements (Cr and Mo), which facilitate the hardenability, in appropriate amounts, the hardenability improves, for example, even if the iron-based sintered alloy is a big product, sufficient hardening, which depends on the C content, can be done down to its inside.
  • alloying elements Cr and Mo
  • the hardened iron-based sintered alloy is such that a martensitic structure is formed, and comes to be of high strength, but, in order to secure the toughness, such as elongation, it is advisable to carry out a heat treatment, such as tempering.
  • Such an iron-based sintered alloy for example, can be obtained by way of the following production process.
  • a production process of the present invention for an iron-based sintered alloy by which the above-described iron-based sintered alloy is obtainable after the following sintering step, is characterized in that it is equipped with: a forming step of making a powder compact by press forming a raw material powder, in which an Fe-system powder, which contains Cr and Mo and in which the major balance is composed of Fe, and a C-system powder, in which C is the major component, are mixed with a strengthening powder, which contains manganese (Mn) and silicon (Si) as being a powder a whole; and a sintering step of heating the powder compact to sinter it in an oxidation preventive atmosphere.
  • the hardening of iron-based sintered alloy can be done by performing a heat treatment to an iron-based sintered alloy, which is obtained after a sintering step, however, in accordance with the present invention, there is not necessarily any need for it. Namely, it is possible as well to carry out hardening by utilizing a heating step, which is done in the sintering step, and a cooling step, which comes next to it. It is so-called sinter-hardening.
  • the heating step of the sintering step must be one in which it is austenite treated by being heated to the Al transformation temperature (about 730° C.) or more, however, an ordinary sintering temperature is 1,050° C. or more, and further 1,100° C. or more.
  • an ordinary sintering temperature is 1,050° C. or more, and further 1,100° C. or more.
  • a much higher sintering temperature such as 1,200° C. or more, 1,250° C. or more, 1,300° C. or more, and further 1,350° C. or more, can be selected.
  • the sintering step of the present invention can preferably be equipped with a heating step in which heating is carried out in a 1,100-1,370° C. inert gas atmosphere.
  • the cooling step of the sintering step is done subsequently to the aforementioned heating step, and is a step which decreases the temperature of the iron-based sintered alloy from the sintering temperature down to around room temperature. Strictly speaking from the viewpoint of hardening, it becomes a step which decreases the temperature of the iron-based sintered alloy from the sintering temperature down to the Ms point or less.
  • the cooling rate can preferably be adapted to 5° C./second or more, and further 10° C./second or more.
  • forcible cooling becomes necessary usually, and since an apparatus therefor becomes necessary separately, it does not make sinter-hardening, which can reduce the production costs.
  • the iron-based sintered alloy of the present invention sufficient hardening can be done even when the cooling rate is small. Specifically, even when the cooling rate is 3° C./second or less, 2° C./second or less, and further 1° C./second or less, hardening is made possible.
  • the cooling rate being 1° C./second or less, it is the cooling rate of ordinary (belt-type) continuous sintering furnaces approximately. Therefore, in accordance with the present invention, without ever disposing a facility for forcible cooling separately, doing hardening to the iron-based sintered alloy is made possible.
  • the sintering step of the present invention can preferably be equipped with a cooling step, which carries out cooling whose cooling rate is 1° C./second or less, after said heating step.
  • the sintering step of the present invention is equipped with the above-described heating step and cooling step, the above-described iron-based sintered alloy, which has a martensitic structure, can be obtained after the sintering step. And, since it is possible to complete hardening simultaneously with the completion of the sintering step, the production-cost reduction of the high-strength iron-based alloy can be intended. Additionally, it is not needed to ever dispose a quenching facility, and the like, separately, the practical application at industrial level is made possible sufficiently.
  • the present invention does not hinder carrying out a heat treatment separately in order to adjust the strength, the toughness, and the like, after completing the sintering step.
  • the present inventors in order to solve the above-described assignment, studied earnestly and repeated trial and error, as a result, they newly found out that, by having Si contained in an appropriate amount, an iron-based sintered-alloy member, which is free from the occurrence of blistering, and the like, which is of high strength and which is good in terms of the dimensional stability, can be obtained, and arrived at completing the present invention.
  • an iron-based sintered-alloy member of the present invention is an iron-based sintered alloy member being completed by sintering a powder compact made by press forming a raw material powder composed of iron (Fe) mainly, and is characterized in that: it comprises, when the entirety is taken as 100% by mass, silicon (Si) in an amount of 0.01-2% by mass; carbon (C) in an amount of 0.1-0.8% by mass; and Fe being the major balance; and it is such a high density that a sintered density ratio ( ⁇ ′/ ⁇ 0 ′ ⁇ 100%), the ratio of a sintered density ( ⁇ ′) to a theoretical density ( ⁇ 0 ′), is 96% or more.
  • This iron-based sintered-alloy member for example, can be obtained by means of the following production process of the present invention.
  • a production process of the present invention for an iron-based sintered-alloy based member, by which the above-described high-density iron-based sintered-alloy member is obtainable after the following sintering step is characterized in that it is equipped with: a forming step of press forming a raw material powder, in which an Fe-system powder, which is composed of at least one of pure iron and iron alloy, and a C-system powder, which includes C mainly, are mixed with an Si-system powder, which is composed of simple substance, alloy or compound of Si, thereby obtaining such a powder compact that a green density ratio ( ⁇ / ⁇ 0 ⁇ 100%), the ratio of a green density ( ⁇ ) to a sintered-body theoretical density ( ⁇ 0 ′), is 96% or more; and a sintering step of heating the powder compact to sinter it in an oxidation prevent
  • Patent Literature No. 3 established an industrial method in which a high-density powder compact can be obtained by a single pressing step.
  • a high-density powder compact whose green density ratio is 96% or more and further 97% or more, for example, can be obtained.
  • an ultra-high-density powder compact whose green density ratio is 96% or more and further 97% or more, for example, can be obtained.
  • an ultra-high-density sintered body iron-based sintered-alloy member
  • the present inventors confirmed that, when it becomes such a high density that the green density ratio or the sintered-body density ratio is 96%-97% approximately, all the characteristics of powder compacts or sintered bodies change suddenly.
  • a density ratio is up to 95% approximately, their strength increases as the increment of their strength, but, when a density ratio exceeds 96%-97% approximately, their strength comes to increase exponentially.
  • the other mechanical properties especially, the ductility, fatigue characteristic, and the like), and the magnetic characteristics, and so forth, show the same tendency.
  • the cause for the occurrence of such blistering is believed to be the fact that moisture, oxides, and the like, which have adhered on the particulate surface of raw material powders, are reduced and decomposed during the heating of the sintering step so that various gases, such as H 2 O, CO and CO 2 , generate. It is believed that these gases are enclosed within powder compacts or within sealed holes inside sintered bodies, and expand during the heating of the sintering step so that blistering occurs in sintered bodies.
  • gases such as H 2 O, CO and CO 2
  • the contacting circumstances of the respective constituent particles differ from those of conventional ones, and turn into such a state that the respective constituent particles adhere snugly. And, it seems that micro residual air holes, which exist in the inside, turn into independent air holes, which are sealed by the surrounding particles. It seems that gases, which generate at the air-pore portions, lose their way of escape; expand abnormally during the high-temperature heating of the sintering step; destroy the bond between the metallic particles; and had macro blistering occurred.
  • the extent of the occurrence of such blistering depends on the compositions of raw material powders, the powder particle diameters, the compacting pressures of powder compacts, the sintering conditions (especially, the temperature), and the like.
  • an iron-based sintered-alloy member which does not include C, one of the important elements of steel materials, is not preferable, for it is less likely to intend the improvement of mechanical characteristics by means of heat treatment.
  • the sintering conditions especially, the sintering temperature
  • the sintering temperature the higher the sintering temperature is the higher their gaseous pressures rise.
  • the higher the sintering temperature is the larger blistering sintered bodies are likely to generate.
  • the present inventors in order to solve this assignment, thought of suppressing the occurrence of the CO gases, and the like, which become the cause of blistering, itself.
  • oxygen which exists in a raw material powder, reacts with a graphite powder, and so forth, which are present around it, to generate gases, such as CO gases, it is advisable to fix the oxygen as a stable solid (oxide) inside the sintered body.
  • the present inventors confirmed the fact that the effect is present in Mn or Si, whose affinity to o is stronger and oxide-formation free energy is lower than that of C, that is, the fact that an effect as an oxygen getter is present.
  • Mn or Si is such that the affinity to O is high extremely, and that the oxide-formation free energy is low sufficiently.
  • they are the fundamental elements of steels, are elements, which are procurable inexpensively comparatively, and additionally do not hinder the recyclability of iron-based sintered-alloy member, either.
  • a (fine) powder for example, an Fe—Mn—Si powder
  • an Fe—Mn—Si powder which is composed of alloy or intermetallic compound of Fe, the major component of the iron-based sintered-alloy member, with Mn or Si
  • the affinity to O is higher than that of Mn or Si simple substance, and that the oxide-formation free energy is low, too, besides, it is procurable more inexpensively.
  • the iron-based sintered-alloy member of the present invention is such that no blistering occurs virtually, it makes one, which inherits the dimensional accuracy and high density of a powder compact. Therefore, since the iron-based sintered-alloy member of the present invention is of high density and high strength, and additionally is good in terms of the dimensional accuracy, it is available at low costs.
  • iron-based sintered-alloy members which belong to a high-density region which has transcended the conventional concept, as well.
  • the defense range of iron-based sintered-alloy members has extended from those of low density to those of ultra-high density, and accordingly the intended use for iron-based sintered-alloy members has expanded remarkably.
  • Si is an important element in view of restraining the blistering of the iron-based sintered-alloy member.
  • the lower limit value of Si can preferably be 0.01% by mass, 0.02% by mass, and further 0.05% by mass.
  • the upper limit value of Si can preferably be 2% by mass.
  • the C amount is adapted to 0.1-0.8% by mass, while considering the occurrence status of blistering as well as the versatility of the iron-based sintered-alloy member as structural members, and the like.
  • C can preferably be 0.2-0.6% by mass, and further 0.3-0.5% by mass.
  • Mn in addition to Si, is an element which improves the mechanical characteristics (strength or ductility, and the like) of iron-based sintered-alloy members. When being too less, the effect is poor; and, when becoming excessive, it results in the strength degradation, and the before/after-sintering dimensional stability too is hindered.
  • Mn when the entire iron-based sintered-alloy member is taken as 100% by mass, is such that the sum with Si can become 3.5% by mass or less, 3% by mass or less, and further 2.5% by mass or less; moreover, it can preferably be included so that the sum becomes 0.02% by mass or more, 0.03% by mass or more, and further 0.05% by mass.
  • the lower limit value of Mn can preferably be 0% by mass, 0.01% by mass, 0.02% by mass, 0.05% by mass, 0.1% by mass, and further 0.2% by mass.
  • the upper limit value of Mn can-preferably be 1.5% by mass, 1.2% by mass (especially, less than 1.2% by mass), 1.15% by mass, 1.1% by mass, 1.05% by mass, and 1.0% by mass (especially, less than 1.0% by mass), and further it is advisable that it can fall in a range of 1-0.5% by mass as well.
  • alloying elements such as molybdenum (Mo), chromium (Cr) and nickel (Ni)
  • Mo molybdenum
  • Cr chromium
  • Ni nickel
  • Mo can be included in an amount of 0.3-2% by mass, and further 0.5-1.5% by mass
  • Cr can be included in an amount of 0.3-5% by mass, and further 0.5-3.5% by mass
  • Ni can be included in an amount of 0.5-6% by mass, and further 1-4% by mass, for example.
  • the iron-based sintered-alloy member of the present invention without ever having Cu contained, is of high strength, and is good in terms of the dimensional stability. Namely, in accordance with the present invention, it is possible to make it a Cu-free iron-based sintered-alloy member, which does not include Cu, which is removed with difficulty by means of smelting, and the like, substantially. Therefore, the present invention improves the recyclability of iron-based sintered-alloy members, and is preferable in view of environmental protections. Further, by suppressing the employment of Cu, the material-cost reduction of iron-based sintered-alloy members can be intended, and additionally the hot brittleness of iron-based sintered-alloy members, which results from Cu, can be avoided.
  • the iron-based sintered-alloy member which is set forth in the present description, according to the present invention does not exclude the case of containing Cu entirely.
  • the case of containing an appropriate amount of Cu in addition to the above-described Si and C is involved in the scope of the present invention as well.
  • the “strength” and “dimensional stability” set forth in the present description depend on the compositions of raw material powders, the formed-body densities (or forming pressures), the sintering conditions (temperature, time, atmosphere, and the like), and so forth. Therefore, it is not possible to identify those “strength” and “dimensional stability” sweepingly. If setting forth them daringly, the strength can preferably be 1,000 MPa or more, 1,500 MPa or more, 2,000 MPa or more, 2,500 MPa or more, and further 3,000 MPa or more, by transverse rupture strength.
  • the dimensional stability without causing blistering during sintering, can preferably be such that a before/after sintering dimensional change rate can be within ⁇ 1%, within ⁇ 0.5%, within ⁇ 0.3%, and further within ⁇ 0.1%. Note that, although this dimensional stability can be found from the measured results between a dimension of a powder compact and a dimension of a sintered body, which is made by sintering it, the measured location is adapted to measuring a dimension, which is likely to change dimensionally by means of blistering.
  • the dimensional stability can be evaluated by the comparison between a green density ratio and a sintered-body density ratio.
  • the iron-based sintered-alloy member of the present invention is such that said sintered-body density ratio can be within ⁇ 1%, within ⁇ 0.5%, within ⁇ 0.3%, and further within ⁇ 0.1%, with respect to said green density ratio.
  • iron-based sintered-alloy member set forth in the present description, is such that its form does not matter, for example, can even be materials, such as ingot-shaped, rod-shaped, tube-shaped plate-shaped ones, and can even be final configurations or structural members, which are close to them. Therefore, this iron-based sintered-alloy member can be paraphrased simply as an “iron-based sintered alloy.”
  • FIG. 1 is a graph for illustrating the relationships between the Mn amount and transverse rupture strength of a 1,150° C.-sintered body (iron-based sintered alloy).
  • FIG. 2 is a graph for illustrating the relationships between the Mn amount and transverse rupture strength of a 1,250° C.-sintered body.
  • FIG. 3 is a graph for illustrating the relationships between the Mn amount and deflection magnitude of a 1,150° C.-sintered body.
  • FIG. 4 is a graph for illustrating the relationships between the Mn amount and deflection magnitude of a 1,250° C.-sintered body.
  • FIG. 5 is a graph for illustrating the relationships between the Mn amount and dimensional change of a 1,150° C.-sintered body.
  • FIG. 6 is a graph for illustrating the relationships between the Mn amount and dimensional change of a 1,250° C.-sintered body.
  • FIG. 7 is a graph for illustrating the relationships between sintered density and transverse rupture strength.
  • FIG. 8 is a graph for illustrating the relationships between sintered density and deflection magnitude.
  • FIG. 9 is a graph for illustrating the results of a three-point bending fatigue test.
  • FIG. 10 is a diagram for illustrating the configuration of a tensile test piece.
  • FIG. 11 is a diagram for illustrating the relationships between tensile strength and FMS-powder composition.
  • FIG. 12 is a diagram for illustrating the relationships between elongation and FMS-powder composition.
  • FIG. 13 is a diagram for illustrating the relationships between green density and after-sintering residual carbon (C) amount.
  • FIG. 14 is a diagram for illustrating the relationships between blended carbon (C) amount and tensile strength.
  • FIG. 15 is a diagram for illustrating the relationships between blended carbon (C) amounts and elongation.
  • FIG. 16 is a graph for illustrating the relationships between compacting pressure and sintered density ratio.
  • FIG. 17A is an appearance photograph of a sintered body in which blistering was generated.
  • FIG. 17B is a cross-sectional photograph of a sintered body in which blistering was generated.
  • a raw material powder comprises an Fe-system powder, which is the major component of the iron-based sintered alloy, and a strengthening powder, which includes Mn and Si.
  • the Fe-system powder can be either a pure iron powder or an iron alloy powder, or even a mixture powder of them. Alloying elements, which are included in the iron alloy powder, do not matter. As for these alloying elements, first of all, C, Mn, Si, P, S, and the like, are available. Mn and Si are added as the strengthening powder, but can be included in small amounts even in the Fe-system powder. However, when the contents of C, Mn, Si, and so forth, increase, the Fe-system powder becomes so hard that the compactibility degrades. Hence, when the Fe-system powder is an iron alloy powder, it is advisable so that C: 0.02% by mass or less, Mn: 0.2% by mass or less, and Si: 0.1% by mass or less.
  • alloying elements other than those Mo, Cr, Ni, V, Co, Nb, W, and the like, are available. These alloying elements improve the thermal treatabilities of iron-based sintered alloys, and are effective elements for strengthening iron-based sintered alloys. These alloying elements, when the entire raw material powder is taken as 100% by mass, can suitably be included so that Mo: 0.1-3% by mass, and further 0.2-2% by mass, Cr: 0.2-5% by mass, and further 0.3-3.5% by mass, and Ni: 0.5-6% by mass, and further 1-4% by mass. Note that these alloying elements are not needed to be contained in the raw material powder as an iron alloy powder, but can be mixed in the raw material powder as powders, and so forth, of alloys or compounds other than Fe.
  • the strengthening powder is such that, as far as it includes Mn and Si as being a powder as a whole composed of one member or two members or more, its existing form does not matter.
  • the strengthening powder can be one member of Mn—Si-system powders, which are composed of alloys or compounds of Mn and Si.
  • it can be a composite powder in which an Mn-system powder, composed of Mn simple substance, alloy or compound, is combined with an Si-system powder, composed of Si simple substance, alloy or compound.
  • it can be a composite powder in which two or more members of this Mn—Si-system powder, an Mn-system powder, composed of Mn simple substance, alloy or compound, and an Si-system powder, composed of Si simple substance, alloy or compound are combined.
  • the Mn—Si-system powder can preferably be an Fe—Mn—Si powder (hereinafter this powder will be referred to as an “FMS powder” wherever appropriate), which is composed of Fe, the major component of the iron-based sintered alloy, and an alloy or intermetallic compound of Mn and Si.
  • This powder is such that it is possible to produce it inexpensively comparatively, or to procure it.
  • This FMS powder when the entire FMS powder is taken as 100% by mass, can preferably be such that Mn is 15-75% by mass, Si is 15-75% by mass, the sum of Mn and Si is 35-95% by mass, and the major balance is Fe.
  • Mn and Si are too less, it turns into an iron alloy with ductility, and it becomes difficult to pulverize it to a fine powder.
  • the addition amount of the FMS powder in the raw material powder becomes greater, and it has raised the costs of the iron-based sintered alloy.
  • Mn and Si are excessive, it is not preferable because the cost for the compositional adjustment rises. It is more preferable that Mn can be 20-65% by mass, Si can be 20-65% by mass, and the sum of Mn and Si can be 50-90% by mass.
  • composition ratio of Mn to Si in the FMS powder does not matter, but it is preferable that the composition ratio (Mn/Si) can be 1/3-3, and further 1/2-2, especially, the compositional ratio can be around 1 (0.9-1.1), that is, Mn and Si in the FMS powder can be proportions of the same extent (about 1:1). It is because, if such is the case, it is likely to obtain a well-balanced iron-based sintered alloy, which is good in terms of all of the strength, ductility, dimensional stability, and the like.
  • the FMS powder can preferably be such that the contained O amount is 0.4% by mass or less, and further 0.3% by mass or less.
  • the O amount in the raw material powder increases, the strengthening actions by means of Mn and Si cannot be demonstrated sufficiently. Further, when sintering such an ultra-high-density powder compact whose green density ratio exceeds 96%, O which exists inside it, can become a cause for having blistering (blister) occurred in the sintered body. This issue will be described later.
  • the proportion of the strengthening powder, which is blended in the raw material powder depends on the compositions of employing powders, or the desired characteristics (the compositions of Mn and Si in the iron-based sintered alloy) of the iron-based sintered alloy.
  • the desired characteristics the compositions of Mn and Si in the iron-based sintered alloy
  • its lower limit value can preferably be 0.2% by mass, 0.3% by mass, 0.4% by mass, and further 0.5% by mass.
  • powders whose particle diameters are small excessively are procured with difficulty, and the costs are high.
  • the agglomeration, and so forth, is likely to generate so that the handlability is bad.
  • the strengthening powder is such that the particle diameter is 100 ⁇ m or less, 63 ⁇ m or less, 45 ⁇ m or less, and further 25 ⁇ m or less, it is likely to disperse uniformly. It is advisable to employ those, which are procurable with ease, within the range.
  • the particle diameter set forth in the present description is one which is identified by means of sieving:
  • the iron-based sintered alloy of the present invention is strengthened by means of Mn and Si, much higher strengthening can be intended by containing C additionally.
  • heat treatments such as hardening and tempering, it becomes easy to better or adjust the mechanical characteristics of the iron-based sintered alloy.
  • Fe-system alloy powder Fe-system alloy powder
  • the C-system powder is such that a graphite powder (Gr powder) in which C is 100% substantially is representative, but; in addition to it, it is also possible to employ an Fe—C alloy powder, various carbide powders, and so forth. It is advisable that the blended amount of the C-system powder, and so on, as described above, can be adapted so that the C amount in the iron-based sintered alloy makes 0.1-1.0% approximately.
  • the production process of the present invention for an iron-based sintered alloy mainly comprises a compacting step, and a sintering step.
  • the compacting step will be explained in detail.
  • the production process of the present invention mainly comprises a compacting step, and a sintering.
  • the compacting step will be first explained in detail.
  • the compacting step is a step in which the raw material powder, in which the above-described Fe-system powder is mixed with the strengthening powder, is press compacted to make a powder compact.
  • the compacting pressure in this instance, the density of the powder compact (or the green density ratio), the configuration of the powder compact, and the like, do not matter.
  • the compacting pressure and green density can be such an extent that it does not collapse with ease at least.
  • the compacting pressure can preferably be 350 MPa or more, 400 MPa or more, and further 500 MPa or more.
  • the green density ratio it is preferable to be 80% or more, 85% or more, and further 90% or more. The higher the compacting pressure or green density ratio is the more likely it is that the high-strength iron-based sintered alloy can be obtained, but it is advisable to select an optimum compacting pressure or green density rate depending on the intended use for the iron-based sintered alloy, and the specifications.
  • the compacting step can be either cold compaction or warm compaction, and an internal lubricant can be added into the raw material powder. When adding an internal lubricant, it is considered the raw material powder while including the internal lubricant as well.
  • Patent Literature No. 3 established a compacting method for a powder compact, the compacting method which makes ultra-high-pressure compaction, which transcends general compacting pressures, possible.
  • this compacting method at such ultra-high pressures as 1,000 MPa or more, 1,200 MPa or more, 1,500 MPa or more, and further about 2,000 MPa or more, powder compacting is made possible.
  • the density of a powder compact which can be obtained by means of this, can reach 96% or more, 97% or more, 98% or more, and further even up to 99%.
  • this good compacting method hereinafter, this compacting method will be referred to as “die wall lubrication warm compaction method” wherever appropriate
  • the die wall lubrication warm compaction method comprises a filling step of filling said raw material powder in a die with a higher fatty acid-system lubricant applied on the inner surface, and a warm compacting step of generating a metallic soap film on the surface of the raw material powder, which contacts with the die inner surface, by warm pressurizing the raw material powder disposed within this die.
  • a higher fatty acid-system lubricant is applied on the inner surface of a die (applying step).
  • the higher fatty acid-system lubricant employed herein in addition to a higher fatty acid itself, can be the metallic salts of higher fatty acids as well.
  • the metallic salts of higher fatty acids lithium salts, calcium salts, or zinc salts, and the like, are available.
  • lithium stearate, calcium stearate, zinc stearate, and so forth are preferable.
  • the applying step for example, can be carried out by spraying a higher fatty acid-system lubricant, which is dispersed in water, an aqueous solution or an alcoholic solution, and the like, into a heated die.
  • a higher fatty acid-system lubricant is dispersed in water, and so forth, it is likely to spray the higher fatty acid-system lubricant onto the inner surface of a die uniformly.
  • the water content, and so on evaporate quickly, and accordingly the higher fatty acid-system lubricant adheres onto the inner surface of the die uniformly.
  • the heating temperature of a die is such that, although it is preferable to consider the temperature of the later-described warm compacting step, it is sufficient to heat it to 100° C. or more, for instance. However, in order to form a uniform film of a higher fatty acid-system lubricant, it is preferable to adapt the heating temperature to less than the melting point of the higher fatty acid-system lubricant. For example, when lithium stearate is used as a higher fatty acid-system lubricant, it is advisable to adapt the heating temperature to less than 220° C.
  • the higher fatty acid-system lubricant in dispersing a higher fatty acid-system lubricant in water, and the like, it is preferable that the higher fatty acid-system lubricant can be included in a such proportion as 0.1-5% by mass, and further 0.5-2% by mass, when the mass of its entire aqueous solution is taken as 100% by mass, because a uniform lubricant film is formed on the inner surface of a die.
  • a surfactant in dispersing a higher fatty acid-system lubricant in water, and the like, when a surfactant is added to the water, uniform dispersion of the higher fatty acid-system lubricant can be intended.
  • a surfactant it is possible to use alkyl phenol-system surfactants, polyoxyethylene nonyl phenyl ether (EO) 6, polyoxyethylene nonyl phenol ether (EO) 10, anionic nonionic-type surfactants, boric acid ester-system emulbon T-80, and so forth, for instance. It is advisable as well to combine two or more members of these to employ.
  • lithium stearate when used as a higher fatty acid-system lubricant, it is preferable to use three members of the surfactants, polyoxyethylene nonyl phenyl ether (EO) 6, polyoxyethylene nonyl phenol ether (EO) 10 and boric acid ester-system emulbon T-80, simultaneously. It is because, in this case, the dispersibility of lithium stearate in water, and so on, is activated all the more, compared with the case where only one member of them is added.
  • EO polyoxyethylene nonyl phenyl ether
  • EO polyoxyethylene nonyl phenol ether
  • aqueous solution of a higher fatty acid-system lubricant whose viscosity fits for spraying, it is preferable to adapt the proportion of a surfactant to 1.5-15% by volume when the volume of its entire aqueous solution is taken as 100% by volume.
  • an antifoaming agent for example, a silicon-system antifoaming agent, and the like. It is because, if the bubbling of an aqueous solution is vigorous, a uniform film of a higher fatty acid-system lubricant is less likely to be formed on the inner surface of a die when spraying it.
  • the addition proportion of an antifoaming agent can be 0.1-1% by volume approximately, for example, when the entire volume of its aqueous solution is taken as 100% by volume.
  • the particles of a higher fatty acid-system lubricant which is dispersed in water, and the like, can be such that the maximum particle diameter is less than 30 ⁇ m. It is because, when the maximum particle diameter becomes 30 ⁇ m or more, the particles of a higher fatty acid-system lubricant are likely to precipitate in an aqueous solution so that it becomes difficult to apply the higher fatty acid-system lubricant onto the inner surface of a die uniformly.
  • the metallic soap film for example, is an iron salt film of a higher fatty acid, which is formed by a mechanochemical reaction taken place between a higher fatty acid-system lubricant and Fe in a raw material powder under warm high pressure.
  • a representative example of this is an iron stearate film, which is generated when lithium stearate or zinc stearate, a higher fatty acid-system lubricant, reacts with Fe.
  • Warm which is referred to in the present step, can be such an extent of heating state that the reaction between a raw material powder and a higher fatty acid-system lubricant is facilitated. Roughly speaking, it is advisable to adapt the compacting temperature to 100° C. or more. However, from the viewpoint of preventing the degenerative change of a higher fatty acid-system lubricant, it is advisable to adapt the compacting temperature to 200° C. or less. It is more suitable to adapt the compacting temperature to 120-180° C.
  • Pressurizing which is referred to in the present step, can be determined appropriately within a range where a metallic soap film is formed while considering the specifications of the iron-based sintered alloy. Considering the die longevity and the productivity, it is preferable to adapt the upper limit of the forming pressure to 2,000 MPa. When the compacting pressure becomes 1,500 MPa approximately, the density of the obtained powder compact, too, approaches the true density (becomes 98-99% by green density ratio), and no further high-densification can be desired even when pressurizing it to 2,000 MPa or more.
  • the sintering step is a step in which a powder compact obtained in the compacting step is sintered by heating it in an oxidation preventive atmosphere.
  • the sintering temperature and sintering time are selected appropriately, considering the desired characteristics, productivity, and the like, of the iron-based sintered alloy.
  • the sintering temperature is too high, liquid phases arise, or dimensional contraction becomes large so that it is not preferable.
  • the sintering temperature is too low, the diffusion of alloying elements becomes insufficient so that it is not preferable.
  • the sintering time becomes long, and accordingly the productivity of the iron-based sintered alloy degrades.
  • the sintering temperature can be 900-1,400° C., and further 1,100-1,350° C.
  • the sintering temperature can be adapted to 1,150° C. or more.
  • the sintering time can be adapted too.1-3 hours, and further 0.1-2 hours, while considering the sintering temperature, the specifications, productivity and costs of the iron-based sintered alloy, and so forth.
  • the sintering atmosphere can be an oxidation preventive atmosphere.
  • Mn and Si which are included in the strengthening powder, are such that the affinity to O is strong extremely so that they are elements which are very likely to be oxidized.
  • the oxide-formation free energy is lower than those of the simple substances of Mn and Si so that there is a fear that it reacts even with scant O within a heating furnace to form the oxides of Mn and Si inside the sintered body.
  • the intervention of such oxides is not preferable, because it deteriorates the mechanical properties of the iron-based sintered alloy.
  • the sintering atmosphere can preferably be an oxidation preventive atmosphere, such as a vacuum atmosphere, an inert gas atmosphere and a nitrogen gas atmosphere.
  • a hydrogen gas high-purity hydrogen gas, which is purified to a low dew point (for example, ⁇ 30° C. or less)
  • a nitrogen gas in an amount of a few % by volume (for instance, 5-10%).
  • a continuous sintering furnace which realizes an ultra-low-oxygen-partial-pressure inert gas (N2 gas) atmosphere, is commercially available (OXYNON furnace produced by KANTO YAKIN KOGYO Co., LTD.).
  • the iron-based sintered alloy of the present invention does not question the high/low of its density. That is, like the conventional iron-based sintered alloys, it can be a low-density iron-based sintered alloy which is made by sintering a powder compact subjected to low-pressure compacting, or can be a high-density sintered alloy which is made by sintering a high-density powder compact subjected to high-pressure compacting using the above-described die wall lubrication warm compaction method. In either of the cases, the improvement of the iron-based sintered alloy's strength and dimensional stability can be intended by means of Mn and Si.
  • the powder compact or the sintered body can rather be of much higher density.
  • a green density ratio or a sintered density ratio can be 92% or more, 95% or more, 96% or more, and further 97% or more.
  • blistering which is made when air holes are formed inside iron-based sintered alloys, becomes not only the internal defects of iron-based sintered alloys, but also it is probable that such an instance occurs that, when the blister is fierce, it bursts up so that sintered bodies do not keep their original shapes. In any case, when such blistering occurs, iron-based sintered alloys have turned into defective products.
  • the contacting circumstances of the respective constituent particles differ from those of conventional ones, and it seems that they turn into such a state that the respective constituent particles adhere snugly. And, micro residual air holes, which exist in the inside, too, turn into independent air holes, which are sealed by the surrounding particles. It seems that gases, which generate at the portions, lose their way of escape; become high pressures abnormally by means of the high-temperature heating during the sintering step; and further destroy the contact or bond between the metallic particles to expand; as a result, they have emerged as macro blistering.
  • an iron-based sintered alloy which is of high strength and is good in terms of the dimensional stability, even when sintering an ultra-high-density powder compact, which is composed of a raw material powder including C such as graphite, at high temperatures, an iron-based sintered alloy, which does not generate the aforementioned blistering, and the production process for the same are required.
  • the present inventors thought of, before oxygen, which exists in a raw material powder, reacts with graphite, and the like, which are present around it, to generate gases, such as CO gases, restraining the occurrence of the CO gases, and so forth, by fixing the oxygen as a stable solid (oxide) in the sintered body. Specifically, they thought of adding a substance (namely oxygen getter), whose affinity to O is stronger and oxide-formation free energy is lower than that of C, to a raw material powder. And, they found out newly that the effect as an oxygen getter is present in Mn and Si (especially in Si).
  • the iron-based sintered alloy which is of high strength and is good in terms of the dimensional stability and furthermore which is low cost, in such a form that is provided with from a low density to an ultra-high density, and accordingly the application range (intended use) for the iron-based sintered alloy has come to expand remarkably.
  • the low-cost iron-based sintered alloy which is of much higher strength and is good in terms of the dimensional stability as well, by single-pressing and single-sintering (lPlS), without ever employing the conventional 2P2S or powder forging method.
  • Such an iron-based sintered alloy, which is of high density, and the production process for the same can be identified as follows, for instance.
  • an iron-based sintered alloy can be identified in such a manner that it is an iron-based alloy, which is completed by sintering a powder compact made by press compacting a raw material powder composed of Fe mainly; and it is characterized in that, when the entirety is taken as 100% by mass, it comprises Si in an amount of 0.01-2% by mass, C in an amount of 0.1-1.0% by mass, and Fe, the major balance; and it is of such a high density that a sintered density ratio ( ⁇ ′/ ⁇ 0′ ⁇ 100%), the ratio of an apparent density ( ⁇ ′) to a theoretical density ( ⁇ 0′), is 92% or more, and further 96% or more.
  • its production process can be identified in such a manner that it is characterized in that it is equipped with a compacting step of obtaining a powder compact, whose green density ratio ( ⁇ ′/ ⁇ 0′ ⁇ 100%), the ratio of a green density ( ⁇ ′) to a theoretical density ( ⁇ 0′), is 92% or more, and further 96% or more, by press compacting a raw material powder, in which an Fe-system powder, which is composed of at least one of pure iron and iron alloy, a C-system powder, which includes C mainly, and an Si-system powder, which is composed of Si simple substance, alloy or compound, are mixed; and a sintering step of heating the powder compact to sinter it; and the above-described iron-based sintered alloy, which is of high density, can be obtained after the sintering step.
  • a compacting step of obtaining a powder compact, whose green density ratio ( ⁇ ′/ ⁇ 0′ ⁇ 100%), the ratio of a green density ( ⁇ ′) to a theoretical density ( ⁇ 0′), is
  • the present inventors found out newly that, when having an FMS powder mixed in a raw material powder, the C-amount variation before/after sintering becomes small remarkably. And, the smaller the varied C amount is the smaller the dimensional change of the iron-based sintered alloy becomes. Further, it was also understood that the varied C amount relates to the before-sintering density of the iron-based sintered alloy. That is, of the higher density the powder compact is the smaller the before/after-sintering varied C amount becomes, and accordingly it became apparent as well that, when a powder compact approaches the true density, the C amount hardly varies before and after sintering so that it stabilizes.
  • the blended composition of a raw material powder is reflected as it is substantially to the after-sintering alloy composition, the production of the iron-based sintered alloy with desired compositions becomes possible.
  • the strengthening action for the iron-based sintered alloy by means of C is demonstrated stably, too; and accordingly, from the viewpoint of the dimensional stability as well as the mechanical characteristics, such as the strength, the quality control of the iron-based sintered alloy becomes easy.
  • the present invention can preferably be such that the green density ratio ( ⁇ / ⁇ 0′ ⁇ 100%) of the powder compact can be 92% or more, 94%, 96% or more, and further 98% or more.
  • the compacting step according to the production process of the present invention can desirably be a step in which the iron-based sintered alloy, which is of such high density, can be obtained.
  • the sintered density ratio ( ⁇ ′/ ⁇ 0′ ⁇ 100%) of the iron-based sintered alloy of the present invention can preferably be 92% or more, 94%, 96% or more, and further 98% or more.
  • the iron-based sintered alloy can be further subjected to heat treatment steps, such as annealing, normalizing, aging, refining (hardening, and tempering), carburizing and nitriding.
  • heat treatment steps such as annealing, normalizing, aging, refining (hardening, and tempering), carburizing and nitriding.
  • the iron-based sintered alloy can preferably be such a composition (C, Mo, Cr, and the like) that depends on the type of heat treatments.
  • iron-based sintered alloy of the present invention do not matter.
  • various pulleys synchronizer hubs for transmissions, connecting rods for engines, hub sleeves, sprockets, ring gears, parking gears, pinion gears, and the like.
  • sun gears driving gears, driven gears, reduction gears, and so forth.
  • a raw material powder comprises an Fe-system powder, a C-system powder, and an Si-system powder.
  • the Fe-system powder can be either a pure iron powder or an iron alloy powder, or even a mixture powder of them. Alloying elements, which are included in the iron alloy powder, do not matter. As for these alloying elements, first of all, C, Mn, Si, P, S, and the like, are available. C is blended as the C-system alloy, and Si blended as the Si-system alloy, but they can be included in small amounts even in the Fe-system powder. However, when the contents of C, Si, and so forth, increase, the Fe-system powder becomes so hard that the compactibility degrades. Hence, when the Fe-system powder is an iron alloy powder, it is advisable so that C: 0.02% by mass or less, and Si: 0.1% by mass or less.
  • alloying elements other than those Mo, Cr, Ni, V, and the like, are available. These alloying elements improve the thermal treatabilities of iron-based sintered-alloy members, and are effective elements for strengthening iron-based sintered-alloys members. These alloying elements, when the entire raw material powder is taken as 100% by mass, can suitably be included so that Mo: 0.3-2% by mass, and further 0.5-1.5% by mass, Cr: 0.3-5% by mass, and further 0.5-3.5% by mass, and Ni: 0.5-6% by mass, and further 1-4% by mass. Note that these alloying elements are not needed to be contained in the raw material powder as an iron alloy powder, but can be mixed in the raw material powder as powders, and so forth, of alloys or compounds other than Fe.
  • the C-system powder in view of the compactibility and blending easiness, and the like, of the raw material powder, is such that it is advisable to employ a graphite (Gr) powder, and so forth. Its blended amount is as described above, and it is advisable that C amount in the iron-based sintered-alloy member can be adapted to 0.1-0.8% approximately.
  • the Si-system alloy includes Si, it can be either a one-member powder or a two-or-more-member powder, and its existence form does not matter.
  • the Si-system powder is a powder of Si simple substance, alloy or compound.
  • This Si-system powder can preferably be an Fe—Mn—Si powder (hereinafter this powder will be referred to as an 'FMS powder” wherever appropriate), which is composed of Fe, the major component of the iron-based sintered-alloy member, and an alloy or intermetallic compound Mn and Si.
  • This powder is such that it is possible to produce it inexpensively comparatively, or to procure it.
  • the Fe—Mn—Si powder when the entire Fe—Mn—Si powder is taken as 100% by mass, can preferably be such that Si is 15-75% by mass, Mn is 15-75% by mass, the sum of Si and Mn is 35-95% by mass, and the major balance is Fe.
  • Si and Mn are too less, it turns into an iron alloy with ductility, and it becomes difficult to pulverize it to a fine powder.
  • the addition amount of the FMS powder in the raw material powder becomes greater, and it has raised the costs of the iron-based sintered-alloy member.
  • Si and Mn are excessive, it is not preferable because the cost for the compositional adjustment rises. It is more preferable that Si can be 20-65% by mass, Mn can be 20-65% by mass, and the sum of Mn and Si can be 50-90% by mass.
  • the composition ratio of Mn to Si in the FMS powder does not matter, but it is preferable that the composition ratio (Mn/Si) can be 1/3-3, and further 1/2-2, especially, the compositional ratio can be around 1 (0.9-1.1), that is, Mn and Si in the FMS powder can be proportions of the same extent (about 1:1). In this case, blistering is likely to be suppressed. Moreover, the iron-based sintered-alloy member, which is well balanced in terms of the strength, ductility, dimensional stability, and the like, can be obtained.
  • the FMS powder can preferably be such that the contained O amount is 0.4% by mass or less, and further 0.3% by mass or less. It is because, when the O amount in the raw material powder becomes greater, the CO gases, and the like, which make the occurrence cause of blistering in the sintered body increases. Moreover, it is because it results in the increment of oxides in the sintered body, and it is because the mechanical characteristics of the iron-based sintered-alloy member become degradable.
  • the proportion of the Si-system powder, which is blended in the raw material powder depends on the compositions of employing powders, the green density ratio, the sintering conditions, and the like. For example, when employing an FMS powder (Si is 15-75% by mass, Mn is 15-75% by mass, and the sum of Mn and Si is 35-95% by mass), it is advisable to blend it in an amount of 0.01-5% by mass, and further 0.05-3% by mass, and furthermore 0.1-2% by mass when the entire raw material powder is taken as 100% by mass.
  • powders whose particle diameters are small excessively are procured with difficulty, and the costs are high.
  • the agglomeration, and so forth, is likely to generate so that the handlability is bad.
  • the Si-system powder is such that it is advisable to employ those whose particle diameter is 63 ⁇ m or less, and further 45 ⁇ m or less, and furthermore 25 ⁇ m or less and whose procurement is easy.
  • the particle diameter of the raw material powder can be 200 ⁇ m or less, and further 180 ⁇ m or less approximately. Note that the particle diameter set forth in the present description is one which is identified by means of sieving.
  • the production process of the present invention for an iron-based sintered-alloy member mainly comprises a compacting step, and a sintering step.
  • the compacting step will be explained in detail.
  • the compacting step is a step in which the raw material powder, in which the above-described Fe-system powder, C-system powder and Si-system powder are mixed, are compacted to make a powder compact.
  • the configuration of the powder compact, or the compacting pressure itself does not matter, but it is aimed at a high-density green compact whose green density ratio is 96% or more. It is because those whose green density ratio is small are such that blistering does not occur so much during its sintering.
  • the present inventors established a compacting method by which such a high-density green compact can be obtained (see Patent Literature No. 3).
  • this compacting method it is possible to carry out ultra-high-pressure compaction, whose compacting pressure is at such industrial level as 1,000 MPa or more, 1,200 MPa or more, 1,500 MPa or more, and further about 2,000 MPa or more, compacting pressure which transcends beyond conventional level.
  • the density of a powder compact, which can be obtained by means of this, can reach 96% or more, 97% or more, 98% or more, and further even up to 99%.
  • this good compacting method hereinafter, this compacting method will be referred to as “die wall lubrication warm compaction method” wherever appropriate
  • the die wall lubrication warm compaction method comprises a filling step of filling said raw material powder in a die with a higher fatty acid-system lubricant applied on the inner surface, and a warm compacting step of generating a metallic soap film on the surface of the raw material powder, which contacts with the die inner surface, by warm pressurizing the raw material disposed within this die.
  • a higher fatty acid-system lubricant is applied on the inner surface of a die (applying step).
  • the higher fatty acid-system lubricant employed herein in addition to a higher fatty acid itself, can be the metallic salts of higher fatty acids as well.
  • the metallic salts of higher fatty acids lithium salts, calcium salts, or zinc salts, and the like, are available.
  • lithium stearate, calcium stearate, zinc stearate, and so forth are preferable.
  • the applying step for example, can be carried out by spraying a higher fatty acid-system lubricant, which is dispersed in water, an aqueous solution or an alcoholic solution, and the like, into a heated die.
  • a higher fatty acid-system lubricant is dispersed in water, and so forth, it is likely to spray the higher fatty acid-system lubricant onto the inner surface of a die uniformly.
  • the water content, and so on evaporate quickly, and accordingly the higher fatty acid-system lubricant adheres onto the inner surface of the die uniformly.
  • the heating temperature of a die is such that, although it is preferable to consider the temperature of the later-described warm compacting step, it is sufficient to heat it to 100° C. or more, for instance. However, in order to form a uniform film of a higher fatty acid-system lubricant, it is preferable to adapt the heating temperature to less than the melting point of the higher fatty acid-system lubricant. For example, when lithium stearate is used as a higher fatty acid-system lubricant, it is advisable to adapt the heating temperature to less than 220° C.
  • the higher fatty acid-system lubricant in dispersing a higher fatty acid-system lubricant in water, and the like, it is preferable that the higher fatty acid-system lubricant can be included in such a proportion as 0.1-5% by mass, and further 0.5-2% by mass, when the mass of its entire aqueous solution is taken as 100% bymass, becauseauniform lubricant film is formed on the inner surface of a die.
  • a surfactant in dispersing a higher fatty acid-system lubricant in water, and the like, when a surfactant is added to the water, uniform dispersion of the higher fatty acid-system lubricant can be intended.
  • a surfactant it is possible to use alkyl phenol-system surfactants, polyoxyethylene nonyl phenyl ether (EO) 6, polyoxyethylene nonyl phenol ether (EO) 10, anionic nonionic-type surfactants, boric acid ester-system emulbon T-80, and so forth, for instance. It is advisable as well to combine two or more members of these to employ.
  • lithium stearate when used as a higher fatty acid-system lubricant, it is preferable to use three members of the surfactants, polyoxyethylene nonyl phenyl ether (EO) 6, polyoxyethylene nonyl phenol ether (EO) 10 and boric acid ester-system emulbon T-80, simultaneously. It is because, in this case, the dispersibility of lithium stearate in water, and so on, is activated all the more, compared with the case where only one member of them is added.
  • EO polyoxyethylene nonyl phenyl ether
  • EO polyoxyethylene nonyl phenol ether
  • aqueous solution of a higher fatty acid-system lubricant whose viscosity fits for spraying, it is preferable to adapt the proportion of a surfactant to 1.5-15% by volume when the volume of its entire aqueous solution is taken as 100% by volume.
  • an antifoaming agent for example, a silicon-system antifoaming agent, and the like. It is because, if the bubbling of an aqueous solution is vigorous, a uniform film of a higher fatty acid-system lubricant is less likely to be formed on the inner surface of a die when spraying it.
  • the addition proportion of an antifoaming agent can be 0.1-1% by volume approximately, for example, when the entire volume of its aqueous solution is taken as 100% by volume.
  • the particles of a higher fatty acid-system lubricant which is dispersed in water, and the like, can be such that the maximum particle diameter is less than 30 ⁇ m. It is because, when the maximum particle diameter becomes 30 ⁇ m or more, the particles of a higher fatty acid-system lubricant are likely to precipitate in an aqueous solution so that it becomes difficult to apply the higher fatty acid-system lubricant onto the inner surface of a die uniformly.
  • the metallic soap film for example, is an iron salt film of a higher fatty acid, which is formed by a mechanochemical reaction taken place between a higher fatty acid-system lubricant and Fe in a raw material powder under warm high pressure.
  • a representative example of this is an iron stearate film, which is generated when lithium stearate or zinc stearate, a higher fatty acid-system lubricant, reacts with Fe.
  • Warm which is referred to in the present step, can be such an extent of heating state that the reaction between a raw material powder and a higher fatty acid-system lubricant is facilitated. Roughly speaking, it is advisable to adapt the compacting temperature to 100° C. or more. However, from the viewpoint of preventing the degenerative change of a higher fatty acid-system lubricant, it is advisable to adapt the compacting temperature to 200° C. or less. It is more suitable to adapt the compacting temperature to 120-180° C.
  • Pressurizing which is referred to in the present step, can be determined appropriately within a range where a metallic soap film is formed while considering the specifications of the iron-based sintered-alloy member. Considering the die longevity and the productivity, it is preferable to adapt the upper limit of the compacting pressure to 2,000 MPa. When the compacting pressure becomes 1,500 MPa approximately, the density of the obtained powder compact, too, approaches the true density (becomes 98-99% by green density ratio), and no further high-densification can be desired even when pressurizing it to 2,000 MPa or more.
  • the sintering step is a step in which a powder compact obtained in the compacting step is sintered by heating it in an oxidation preventive atmosphere.
  • the sintering temperature and sintering time are selected appropriately, considering the desired characteristics, productivity, and the like, of the iron-based sintered-alloy member.
  • the sintering temperature is too high, liquid phases arise, or dimensional contraction becomes large so that it is not preferable.
  • the sintering temperature is too low, the diffusion of alloying elements is insufficient so that it is not preferable.
  • the sintering time becomes long, and accordingly the productivity of the iron-based sintered-alloy member degrades.
  • the sintering temperature can be 900-1,400° C., and further 1,100-1,350° C.
  • the sintering temperature can be adapted to 1,200° C. or more.
  • the sintering time can be adapted to 0.1-3 hours, and further 0.1-1 hour, while considering the sintering temperature, the specifications, productivity and costs of the iron-based sintered-alloy member, and so forth.
  • Si and Mn which are effective elements for the sintering atmosphere and the blistering restraint of high-strength sintered bodies.
  • Si in addition to C, Mn, phosphorus (P) and sulfur (S), is referred to as the five elements of steels, and are general strengthening elements in melt produced iron/steel materials.
  • Si in the Si-system powder is such that the affinity to oxygen is high extremely so that it is an element, which is very likely to be oxidized.
  • an Fe—Mn—Si alloy compound
  • the oxide-formation free energy is lower than that of Si simple substance so that there is a fear that it reacts even with scant O within a heating furnace to form the oxides of Si inside the sintered body.
  • the intervention of such oxides is not preferable, because it deteriorates the mechanical properties of the iron-based sintered-alloy member.
  • an iron-based sintered alloy, which contains Si has been hardly available so far.
  • the sintering step is carried out in an oxidation preventive atmosphere.
  • an oxidation preventive atmosphere Specifically, a vacuum atmosphere, an inert gas atmosphere, a nitrogen atmosphere, and the like, are available. Even if it is such an atmosphere, when residual oxygen (oxygen partial pressure) therein matters, it is advisable to employ a reducing atmosphere in which a hydrogen gas (purified high-purity hydrogen gas whose dew point is low) is mixed with a nitrogen gas in an amount of a few %.
  • the iron-based sintered-alloy member depending on its specifications, can be further subjected to heat treatment steps, such as annealing, normalizing, aging, refining (hardening, and tempering), carburizing and nitriding.
  • heat treatment steps such as annealing, normalizing, aging, refining (hardening, and tempering), carburizing and nitriding.
  • the iron-based sintered-alloy member can preferably be such a composition (C, Mo, Cr, and the like) that depends on the type of heat treatments.
  • the form of and intended use for the iron-based sintered-alloy member of the present invention do not matter.
  • various pulleys, synchronizer hubs for transmissions, connecting rods for engines, sprockets, ring gears, pinion gears, and the like In addition to them, there are a variety of gear component parts, such as sun gears, driving gears and driven gears, and so forth.
  • Fe-system alloy a pure iron powder (ASC100.29 produced by HEGANESE Co., Ltd., and Particle Diameters: 20-180 ⁇ m) was prepared, and, as a strengthening powder, an Fe—Mn—Si powders (FMS powders) were prepared.
  • ASC100.29 produced by HEGANESE Co., Ltd., and Particle Diameters: 20-180 ⁇ m
  • FMS powders Fe—Mn—Si powders
  • the FMS powders were those which were made by pulverizing cast bulks (ingots) with various compositions set forth in Table 6, which were melt produced in an Ar gas atmosphere, and sieving them to a powder, whose particle diameters were 25 ⁇ m or less (500 mesh).
  • the compositions of the FMS powders will be identified by specifying the numbers (I-IX) in Table 6.
  • strengthening powders an Fe-75.6% Mn powder (produced by FUKUDA KINZOKU HAKUFUN Co., Ltd.), an Mn-system powder, and an Fe-76.4% Si powder (produced by FUKUDA KINZOKU HAKUFUN Co., Ltd.), an Si-system powder, were prepared as well.
  • the particle size of these powders was such that both of them were ⁇ 250 mesh (63 ⁇ m or less).
  • the units of the compositions are % by mass (being the same hereinafter unless otherwise specified) particularly.
  • a graphite (Gr) powder (JCPB produced by NIHON KOKUEN Co., Ltd.), a C-system powder, was prepared as well.
  • the particle diameters of this powder were 45 ⁇ m or less.
  • Fe-10% Cu partially-diffused alloy powder (DistaloyACu produced by HEGANESE Co., Ltd., and Particle Diameters: 20-180 ⁇ m) was prepared.
  • Powder compacts were carried out by means of the die wall lubrication warm compaction method mainly. Specifically, they are as hereinafter described. Two types of dies made of cemented carbide, which had a ⁇ 23 mm cylinder-shaped cavity and a 10 ⁇ 55 mm transverse test piece-shaped cavity, were prepared. To the inner peripheral surface of the respective dies, a TiN-coat treatment was performed in advance so that its surface roughness was adapted to 0.4 Z. The respective dies were heated to 150° C. with a band heater in advance.
  • LiSt lithium stearate
  • a spraying gun in which lithium stearate (LiSt), a higher fatty acid-system lubricant, was dispersed, was sprayed uniformly by a spraying gun in a proportion of 1 cm 3 /second approximately (applying step).
  • LiSt film was formed to such an extent as about 1 ⁇ m.
  • the aqueous solution used herein is one in which LiSt was dispersed in one in which a surfactant and an antifoaming agent were added to water.
  • a surfactant polyoxyethylene nonyl phenyl ether (EO) 6, polyoxyethylene nonyl phenyl ether (EO) 10, and boric acid ester emulbon T-80 were used, each of them was added in an amount of 1% by volume, respectively, with respect to the entire aqueous solution (100% by volume).
  • EO polyoxyethylene nonyl phenyl ether
  • EO polyoxyethylene nonyl phenyl ether
  • boric acid ester emulbon T-80 boric acid ester emulbon T-80
  • FS antifoam 80 was used, and was added in an amount of 0.2% by volume with respect to the entire aqueous solution (100% by volume).
  • LiSt one whose melting point was about 225° C.
  • the aqueous solution in which LiSt was dispersed, was further subjected to a micro-fining treatment (Teflon-coated steel balls: 100 hours) with a ball mill-type pulverizing apparatus. The thus obtained stock solution was diluted by 20 times, and an aqueous solution, whose final concentration was 1%, was used for the aforementioned applying step.
  • the above-described various raw material powders were filled naturally (filling step)
  • the raw material powders were heated to 150° C., the same temperature as that of the dies, with a drier in advance.
  • the respective raw material powders, which were filled in the dies, were formed with various forming pressures, thereby obtaining powder compacts (warm compacting step). Even in any case of all the compacting pressures, it was possible to take the powder compacts out of the dies with low ejection forces, without causing any galling, and the like, on the inner surface of the dies.
  • part of the samples employed mixture powders, which were made by adding LiSt, an internal lubricant, in an amount of 0.8%, and admixing it, as the raw material powders.
  • ordinary room-temperature forming was performed, thereby obtaining powder compacts (see Table 5).
  • the admixing of the pure iron powder, and the like, with LiSt (powdery) was carried out with a V-shaped mixer or a rotary ball mill.
  • the compacting pressure was adapted to 4 stages, 392 MPa, 490 MPa, 588 MPa and 686 MPa, in order to prevent the dies' damages.
  • transverse test piece-shaped samples (2) Using the aforementioned transverse test piece-shaped samples, a transverse test was carried out by means of three-point bending with 40 mm-distance between fulcrums. Thus, the strength (transverse rupture strength) and deflection up to rupture of the respective samples were found. Moreover, the hardness of the transverse test piece-shaped samples' side surface was measured at 30 kg load by means of a Vickers hardness meter.
  • Sample No. E00 is the case of an Fe—C-system sintered alloy without the strengthening powder; and Sample Nos. E01-03 are the case of Fe—Cu—C-system iron-based sintered alloys employing the above-described Fe-10% Cu powder instead of the strengthening powder.
  • Sample Nos. E1-E5 while keeping the Mn+Si amount constant at 2%, are those in which the proportion (compositional ratio) was changed variously.
  • Sample Nos. E2-4 in which the Mn/Si falls in 3-1/3 were confirmed that, in all of them, strengths equal to or more than can be obtained, with respect to Sample No. E02 (the C amount is 0.6% as much as that of Sample No. E2, and the like, identically; and the Cu amount is 2% as much as the Mn+Si amount of them identically).
  • the sintered bodies which were strengthened by Mn and Si, were such that the deflection amount is improved more drastically than that of the sintered body, which was strengthened by Cu, and accordingly it was understood that they exhibit very good ductility.
  • a sintered body which is of much higher strength and high ductility, can be obtained by the employment of less Mn +Sn than Cu. Note that all of the above-described tendencies were identical even when the sintering temperature was either 1,150° C. or 1,250° C.
  • Sample Nos. E18-E20 When comparing Sample Nos. E18-E20, in which the blended amount of the FMS powders was constant at 2% and the C amount differed respectively, with Sample Nos. E6-E8 or Sample Nos. E9-E11, in which the Mn+Si amount fell in ranges equal to theirs, Sample Nos. E18-E20 were better in terms of both of the strength and ductility. That is, it was understood that a sintered body, which is better in terms of the mechanical characteristics, can be obtained, by blending the strengthening powder as an Fe—Mn—Si powder rather than by blending it as an Fe—Mn powder or an Fe—Si-system powder. This tendency was identical even when the sintering temperature was either 1,150° C. or 1,250° C.
  • Sample Nos. E17-E27 were such that, in all of them, the dimensions were stabilized.
  • the dimensions of the sintered bodies tend to increase (that is, expand) as the increment of the FMS powder amount, it is understood from Sample Nos. E21-23 that, when employing the #II FMS powder, the dimensional change was hardly influenced by the FMS powder amount and was stabilized very well.
  • the FMS powders in which the Mn+Si amount was kept constant at 80% (entire powder: 100%) and the Mn/Si was 3-1, were employed, and the C amount was kept constant at 0.6%.
  • the Si amount of the #VI FMS powder became 33%, because the composition simply deviated more or less out of the targeted 30%, and the fact itself does not involve any special intention at all.
  • FIG. 1 - FIG. 6 Those, in which the above results are reorganized regarding the Mn amount for every sintering temperature, are illustrated in FIG. 1 - FIG. 6 .
  • FIG. 1 and FIG. 2 illustrate the relationships between the Mn amount and the transverse rupture strength
  • FIG. 3 and FIG. 4 illustrate the relationships between the Mn amount and the deflection amount
  • FIG. 5 and FIG. 6 illustrate the relationships between the Mn content and the before/after-sintering dimensional change.
  • FMS cast bulks Fe—Mn—Si-system cast bulks (FMS cast bulks) are brittle, it is possible to obtain FMS powders easily by mechanically pulverizing them.
  • an FMS cast bulk with the #IV composition one in which the Mn and Si amounts are less and whose ductility is high comparatively was such that it was not easy to adapt it to a fine powder of ⁇ 250mesh ( ⁇ 63 ⁇ m or less) by mechanical pulverizing alone.
  • the respective FMS powders having the aforementioned three types of particle diameters were mixed with the above-described pure iron powder and graphite powder, thereby preparing raw material powders with Fe-2FMSVI-0.6C composition.
  • the respective raw material powders were compacted into powder compacts by means of the die lubrication warm compaction method, and Sample Nos. E31, E44 and E45 were obtained by sintering the powder compacts.
  • the respective characteristics of the obtained powder compacts and sintered bodies (Fe—Mn—Si—C-system iron-based sintered alloy) are set forth in Table 4.
  • Powder compacts were compacted by means of a compacting method (general compacting method), which differed from the die wall lubrication warm compaction method which made high-density forming possible, and the powder compacts were sintered.
  • the respective characteristics of the thus obtained powder compacts and sintered bodies of Sample Nos. E41, E42 and E04 are set forth in Table 5 along with the respective blended compositions.
  • Sample Nos. E41 and E42 are those which were made by adding 0.1% and 0.8% internal lubricants (LiSt), respectively, to a raw material powder with Fe-2FMSVI-0.8C composition, which employed the #VI FMS powder ( ⁇ 250 mesh powder), and compacting and sintering them.
  • Sample No. E41 included the 0.1% internal lubricant, it is one which was formed under the same forming conditions as the above-described die wall lubricantion warm compaction method; and Sample No. E42 is one which was compacted by means of a room-temperature compaction method without die wall lubrication.
  • Sample No. E04 is one which was made by adding the 0.8% internal lubricant (LiSt) to a raw material powder with Fe-2Cu-0.8C composition, room-temperature compacting them (same as Sample No. E42), and sintering them.
  • the sintering step in conjunction with the general sintering conditions for Fe—Cu—C-system sintered bodies, was carried out in an N 2 -5% H 2 atmosphere for 1,140° C. ⁇ 20 minutes in all of them.
  • the cooling rate for the after-sintering samples was about 40° C./min.
  • FIG. 7 illustrates the relationships between the sintered density and the transverse rupture strength
  • FIG. 8 illustrates the relationships between the sintered density and the deflection amount. It was confirmed that both of the transverse rupture strength and deflection magnitude increase substantially monotonously, accompanied by the increment of the FMS powder amount, (are in proportion thereto). Further, the results of carrying out a three-point bending fatigue test with regard to the sintered bodies of Sample No. E42 and Sample No. E04 are shown in FIG. 9 . Thus, it was confirmed that the sintered body according to the present invention has fatigue resistance equal to or more than that of the conventional sintered body.
  • Iron alloy powders (AstaloyCrM, produced by HEGANESE Co., Ltd., Particle Diameters: 20-180 ⁇ m, and AstaloyMo, produced by HEGANESE Co., Ltd., Particle Diameters: 20-180 ⁇ m), Fe-system powders, the above-described pure iron powder (ASC100.29 produced by HEGANESE Co., Ltd.), the above-described FMS powders, strengthening powders, and the above-described Gr powder, a C-system powder, were prepared.
  • the composition of AstaloyCrM, an iron alloy powder is Fe-3Cr-0.5Mo (% by mass), and the composition of AstaloyMo is Fe-1.5Mo (% by mass).
  • the FMS powders employed the above-described #VI, #VII and #VIII powders in Table 6. The production method, classification, particle diameters, and the like, of the FMS powders are the same as described above.
  • Powder compacts were produced by means of the above-described die wall lubrication warm compaction method. Various conditions, and the like, were identical basically. However, the configuration of the powder compacts was adapted to a ⁇ 23 mm-cylinder shape and a tensile-test-piece-shaped configuration illustrated in FIG. 10 . Two types of dies, which had cavities corresponding to these configurations, were prepared, and the die wall lubrication warm compaction method was carried out.
  • the obtained samples are the ⁇ 23 mm cylinder-shaped samples, and the tensile-test-piece-shaped samples. And, regarding the tensile-test-piece-shaped samples, 200° C. ⁇ 60 minutes heating was carried out within an atmosphere in air (tempering step).
  • the samples (E131, E143 and E144) employing the FMS powders were such that the tensile strength improved more by 200-300 Mpa approximately than that of the sample (E137) without employing any FMS powder.
  • the samples employing the FMS powders showed a tensile strength of 1,500 MPa or more roughly.
  • the samples which were made by adapting the compacting pressure to 1,176 MPa showed much higher tensile strength that was well over 1,600 Mpa. Therefore, it was understood as well that the high-strengthening of iron-based sintered alloys by means of the FMS powders is such that the types of the FMS powders and the magnitude of their compacting pressures do not matter.
  • the ultra-high-strength iron-based sintered alloys could be obtained at an ordinary cooling rate without ever carrying out forcible cooling in the cooling step of the sintering step.
  • the dimensional changes of the present example's sintered bodies were equal to or less than those of Sample No. E137 making their base. Therefore, the respective iron-based sintered alloys according to the present examples using the FMS powders were such that all of them were of ultra-high strength and additionally the dimensional changes were small, and were those which allowed to intend the reduction of production costs.
  • the case of not including the FMS powder is such that it was understood that, when the powder compact's green density decreases, the after-sintering C amount, too, decreases sharply (that is, the before/after-sintering varied C amount enlarges sharply) . Further, in this case, it was understood as well that, even when the green density becomes 7.4 g/cm 3 or more, the reduction magnitude of the C amount does not become 6% or less. Therefore, by having an FMS powder contained in a raw material powder, it is possible to enhance the yield ratio of the C amount in the green compact's extensive area.
  • the tensile strength shows the maximum value when the Gr powder is 0.4-0.6% by mass. Moreover, the more the blended amount of the FMS powder the composition has, the higher the maximum value of the tensile strength becomes. This tendency comes into effect substantially even when the blended amounts of the FMS powder, the compacting pressures and the sintering temperatures differ. Next, it became apparent that the more the blended amount of the FMS powder increases the more likely it is that the tensile strength shows the maximum value in the region where the blended C amount is much less. This tendency, too, comes into effect substantially even when the compacting pressures and the sintering temperatures differ.
  • the FMS powder blended it is possible to obtain the iron-based sintered alloy whose tensile strength is enlarged while avoiding the decrement of the elongation. That is, even while securing the toughness, the high-strength iron-based sintered alloy can be obtained.
  • a general sintering temperature without ever performing any special heat treatment, 1,100-MPa-or-more, 1,200-MPa-or-more, and further 1,300-MPa-or-more iron-based sintered alloys have been obtained.
  • the sintering temperature is 1,250° C., 1,400-MPa-or-more, 1,500-MPa-or-more, and further 1,600-MPa-or-more iron-based sintered alloys can be obtained.
  • Fe—Mn—Si powders were prepared as an Si-system powder. These FMS powders were those which were made by pulverizing Fe—Mn—Si-system cast bulks (ingots) with various compositions set forth in Table 22, which were melt produced in an Ar gas atmosphere, and sieving them to a powder, whose particle diameters were 25 ⁇ m or less. Hereinafter, the compositions of the FMS powders will be identified by means of the numbers (I-III) in Table 22.
  • Fe—Mn—Si-system cast bulks are brittle, it is possible to obtain FMS powders easily by mechanically pulverizing them. However, since an FMS cast bulk whose Si+Mn amount is 35% or less is such that the ductilitywas high comparatively, it was difficult to adapt it to a fine powder by mechanical pulverizing alone.
  • a pure Si powder produced by FUKUDA KINZOKU HAKUFUN Co., Ltd.
  • an Fe-76.4% Si powder produced by FUKUDA KINZOKU HAKUFUN Co., Ltd.
  • an Si-system powder produced by FUKUDA KINZOKU HAKUFUN Co., Ltd.
  • an Fe-75.6% Mn powder produced by FUKUDA KINZOKU HAKUFUN Co., Ltd.
  • Mn-system powder were prepared as well.
  • the units of the compositions are % by mass (being the same hereinafter unless otherwise specified particularly). All of these powders were such that those whose particle size ⁇ 500 mesh (25 ⁇ m or less) were employed.
  • a graphite (Gr) powder (JCPB produced by NIHON KOKUEN Co., Ltd.), a C-system powder, was prepared as well. The particle diameters of this powder were 45 am or less.
  • Powder compacts were carried out by means of the die wall lubrication warm compaction method mainly. Specifically, they are as hereinafter described. Two types of dies made of cemented carbide, which had a ⁇ 23 mm cylinder-shaped cavity and a 10 ⁇ 55 mm transverse test piece-shaped cavity, were prepared. To the inner peripheral surface of the respective dies, a TiN-coat treatment was performed in advance so that its surface roughness was adapted to 0.4Z. The respective dies were heated to 150° C. with a band heater in advance.
  • LiSt lithium stearate
  • a spraying gun in which lithium stearate (LiSt), a higher fatty acid-system lubricant, was dispersed, was sprayed uniformly by a spraying gun in a proportion of 1 cm 3 /second approximately (applying step).
  • LiSt film was formed to such an extent as about 1 ⁇ m.
  • the aqueous solution used herein is one in which LiSt was dispersed in one in which a surfactant and an antifoaming agent were added to water.
  • a surfactant polyoxyethylene nonyl phenyl ether (EO) 6, polyoxyethylene nonyl phenyl ether (EO) 10, and boric acid ester emulbon T-80 were used, each of them was added in an amount of 1% by volume, respectively, with respect to the entire aqueous solution (100% by volume).
  • EO polyoxyethylene nonyl phenyl ether
  • EO polyoxyethylene nonyl phenyl ether
  • boric acid ester emulbon T-80 boric acid ester emulbon T-80
  • FS antifoam 80 was used, and was added in an amount of 0.2% by volume with respect to the entire aqueous solution (100% by volume).
  • LiSt one whose melting point was about 225° C.
  • the aqueous solution in which LiSt was dispersed, was further subjected to a micro-fining treatment (Teflon-coated steel balls: 100 hours) with a ball mill-type pulverizing apparatus. The thus obtained stock solution was diluted by 20 times, and an aqueous solution, whose final concentration was 1%, was used for the aforementioned applying step.
  • the above-described various raw material powders were filled naturally (filling step).
  • the raw material powders were heated to 150° C., the same temperature as that of the dies, with a drier in advance.
  • the respective raw material powders, which were filled in the dies, were compacted with various compacting pressures, thereby obtaining powder compacts (warm compacting step). Even in any case of all the compacting pressures, it was possible to take the powder compacts out of the dies with low ejection forces, without causing any galling, and the like, on the inner surface of the dies.
  • transverse test pieces carried out a hardening-tempering heat treatment.
  • the hardening treatment was carried out by quenching them in a 60° C. oil after heating them 850° C. ⁇ 1 hour in a nitrogen atmosphere.
  • the tempering thereafter was carried out by heating them 200° C. ⁇ 1 hour in air.
  • transverse test piece-shaped samples (2) Using the aforementioned transverse test piece-shaped samples, a transverse test was carried out by means of three-point bending with 40 mm-distance between fulcrums. Thus, the strength (transverse rupture strength) and until the respective samples ruptured were found. Moreover, the hardness of the transverse test piece-shaped samples' side surface was measured at 30 kg load by means of a Vickers hardness meter.
  • Raw material powders with various compositions were prepared, raw material powders in which the above-described Astaloy Mo powder and the graphite (Gr) powder were blended and admixed. These raw material powders are those which did not include any Si-system powder. These raw material powders were compacted with various compacting pressures by means of the die wall lubrication warm compaction method, and the obtained respective powder compacts were sintered, thereby obtaining respective sintered bodies (iron-based sintered-alloy members) of Sample No. HS8 set forth in Table 21. The characteristics of the respective powder compacts and respective sintered bodies are set forth in Table 21 along with the blended composition of each of the raw material powders.
  • the sintered bodies whose blended amount of the Gr powder was 0.3-0.6% were such that blistering was generated when the compacting pressure was 1,568 MPa or more, or 1,960 MPa or more.
  • the occurrence of blistering can be not only confirmed by the fact that the dimensional changes (especially, the height dimensions) changed greatly toward positive side, but also by the fact that the sintered density ratios degraded sharply. For example, when a powder compact whose green density was 98% or more was sintered, it is possible to judge that blistering occurred from the fact that its sintered density degraded sharply beyond ⁇ 1% of the green density ratio to 90% or less.
  • FIG. 16 the relationships between the green density ratio as well as sintered-body density ratio and the compacting pressure when using the raw material powder whose blended amount of the Gr powder was 0.5%.
  • FIG. 17A FIG. 17B , appearance photographs of the samples (blended amount of Gr powder: 0.5%, and compacting pressure: 1,960 MPa) in which blistering occurred, and their cross-sectional photographs are shown, respectively. As can be apparent from FIG. 17B , it was understood that the fact that large air holes were formed inside the sintered body is the cause of blistering.
  • Raw material powders with various compositions were prepared by blending and admixing the above-described Astaloy Mo powder, the graphite (Gr) powder and the#I FMS powder. These raw material powders were compacted with various compacting pressures by means of the die wall lubrication warm compaction method, and the obtained respective powder compacts were sintered, thereby obtaining sintered bodies of Sample Nos. HS9-HS12 set forth in Table 12. The characteristics of the respective powder compacts and respective sintered bodies are set forth in Table 12 along with the blended composition of each of the raw material powders.
  • the height change ( ⁇ T) in the table is the dimensional variation in the compression direction of the ⁇ 23 cylinder-shaped sample.
  • This ⁇ T expresses the behavior of blistering most remarkably.
  • the negative values of this ⁇ T mean that the sintered bodies contracted from the powder compacts. When being a sintered body in which the ⁇ T becomes negative, no blistering occurs, and accordingly there is not any problem as an iron-based sintered-alloy member practically. Even if the ⁇ T is positive values, however, when being a sintered body whose ⁇ T is 0.5% or less, its density hardly degrades, and accordingly there is not any problem practically.
  • the blended amount of the FMS powder can be 0.1% or more, and further 0.2% or more.
  • the Si amount can preferably be 0.02% or more, and further 0.04% or more.
  • Raw material powders with various compositions were prepared by blending and admixing the above-described Astaloy Mo powder, the graphite (Gr) powder and the #II FMS powder. These raw material powders were compacted with various compacting pressures by means of the die wall lubrication warm compaction method, and the obtained respective powder compacts were sintered, thereby obtaining sintered bodies of Sample Nos. HS13-HS16 set forth in Table 13. The characteristics of the respective powder compacts and respective sintered bodies are set forth in Table 13 along with the blended composition of each of the raw material powders.
  • the sintered bodies whose blended amount of the FMS powder was 0.1% or more are such that, regardless of the blended amounts of the Gr powder and the compacting pressures, the ⁇ T was negative values in all of them; and no blistering occurred in those samples.
  • the blended amount of the FMS powder can be 0.1% or more, and further 0.2% or more.
  • the Si amount can preferably be 0.03% or more, and further 0.06% or more.
  • Raw material powders with various compositions were prepared by blending and admixing the above-described Astaloy Mo powder, the graphite (Gr) powder and the #III FMS powder. These raw material powders were compacted with various compacting pressures by means of the die wall lubrication warm compaction method, and the obtained respective powder compacts were sintered, thereby obtaining sintered bodies of Sample Nos. HS17-HS20 set forth in Table 14. The characteristics of the respective powder compacts and respective sintered bodies are set forth in Table 14 along with the blended composition of each of the raw material powders.
  • the sintered bodies whose-blended amount of the FMS powder was 0.1% or more are such that, regardless of the blended amounts of the Gr powder and the compacting pressures, the ⁇ T was negative values in all of them; and no blistering occurred in those samples.
  • the blended amount of the FMS powder can be 0.05% or more, 0.1% or more, and further 0.2% or more.
  • the it can preferably be 0.02% or more, 0.04% or more, and further 0.08% or more.
  • Transverse test piece-shaped sintered bodies were produced respectively, transverse test piece-shaped sintered bodies which were the same as the respective samples, among above-described Sample Nos. HS11, HS15 and HS19, in which the blended amount of the Gr powder was adapted to 0.5%, the blended amount of the FMS powder was adapted to 0.1% and the compacting pressure was adapted to 1,568 MPa.
  • the above-described heat treatment were performed to these, thereby obtaining transverse test pieces (iron-based sintered-alloy members). To these test pieces, the transverse test was carried out, thereby examining the bending-strength characteristic of each of them. This result is set forth in Table 15.
  • Raw material powders with various compositions were prepared by blending and admixing the above-described various low alloy powders, the graphite (Gr) powder and the #II FMS powder. These raw material powders were compacted with various compacting pressures by means of the die wall lubrication warm compaction method, and the obtained respective powder compacts were sintered, thereby obtaining sintered bodies of Sample Nos. HS1-HS7 and Sample Nos. C1 and C2. The characteristics of the respective powder compacts and respective sintered bodies are set forth in Table 16 and Table 17 along with the blended composition of each of the raw material powders. Note that, for the blending of the raw materials, the #II FMS powder was employed while taking the result of the Fifth Example into account. In Sample Nos.
  • the blended amount of the FMS powder was varied in the range of 0.1-1% by mass. In the case of the other Fe-system alloy powders, the blended amount of the FMS powder was fixed constant at 0.5% by mass. However, Sample Nos. C1 and C2 were such that no FMS powder was blended. The blended amount of the Gr powder was fixed constant at 0.5% by mass in all of the samples.
  • raw material powders with various compositions were prepared by blending and admixing the Astaloy Mo powder, the graphite (Gr) powder and an Fe-76.4% Si powder ( ⁇ 500 mesh). These raw material powders were compacted with various compacting pressures by means of the die wall lubrication warm compaction method, and the obtained respective powder compacts were sintered, thereby obtaining sintered bodies of Sample Nos. HS29 and HS21-HS23 set forth in Table 18. The characteristics of the respective powder compacts and respective sintered bodies are set forth in Table 18 along with the blended composition of each of the raw material powders.
  • raw material powders with various compositions were prepared by blending and admixing the Astaloy Mo powder, the graphite (Gr) powder and an Fe-75.6% Mn powder ( ⁇ 500 mesh). These raw material powders were compacted with various compacting pressures by means of the die wall lubrication warm compaction method, and the obtained respective powder compacts were sintered, thereby obtaining sintered bodies of Sample No. HS24 set forth in Table 19. The characteristics of the respective powder compacts and respective sintered bodies are set forth in Table 19 along with the blended composition of each of the raw material powders.
  • raw material powders with various compositions were prepared by blending and admixing the Astaloy Mo powder, the graphite (Gr) powder and a pure Si powder ( ⁇ 500 mesh). These raw material powders were compacted with various compacting pressures by means of the die wall lubrication warm compaction method, and the obtained respective powder compacts were sintered, thereby obtaining sintered bodies of Sample Nos. HS25-28 set forth in Table 20. The characteristics of the respective powder compacts and respective sintered bodies are set forth in Table 20 along with the blended composition of each of the raw material powders.
  • the sintered-body theoretical-density value is such that the following values were used. AstaloyMo Material: 7.88 g/cm3 DistaloyAE Material: 7.88 g/cm3 KIP30CRV Material: 7.83 g/cm3 KIP103V Material: 7.85 g/cm3
  • the sintered-body theoretical-density value is such that the following values were used. AstaloyMo Material: 7.88 g/cm3 DistaloyAE Material: 7.88 g/cm3 KIP30CRV Material: 7.83 g/cm3 KIP103V Material: 7.85 g/cm3

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CN1946865A (zh) 2007-04-11
US9017601B2 (en) 2015-04-28
JP2005336609A (ja) 2005-12-08
JP4440163B2 (ja) 2010-03-24
WO2005103315A1 (ja) 2005-11-03
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