US20110206551A1 - Ferrous sintered alloy and process for producing the same as well as ferrous-sintered-alloy member - Google Patents

Ferrous sintered alloy and process for producing the same as well as ferrous-sintered-alloy member Download PDF

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US20110206551A1
US20110206551A1 US13/125,948 US200913125948A US2011206551A1 US 20110206551 A1 US20110206551 A1 US 20110206551A1 US 200913125948 A US200913125948 A US 200913125948A US 2011206551 A1 US2011206551 A1 US 2011206551A1
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powder
ferrous sintered
sintered alloy
raw
alloy
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Mikio Kondoh
Toshitake Miyake
Shigehide Takemoto
Kimihiko Ando
Nobuhiko Matsumoto
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Toyota Motor Corp
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Toyota Motor Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C22/00—Alloys based on manganese
    • 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
    • B22F3/10—Sintering only
    • B22F3/1003—Use of special medium during sintering, e.g. sintering aid
    • B22F3/1007—Atmosphere
    • 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
    • C22C33/0207—Using a mixture of prealloyed powders or a master alloy
    • 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%
    • C22C33/0271—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements the maximum content of each alloying element not exceeding 5% with only C, Mn, Si, P, S, As as alloying elements, e.g. carbon steel
    • 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
    • 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 is one which relates to a ferrous sintered alloy that is good in terms of strength and dimensional stability, and that makes it feasible to be free from Cu, or to be free from Ni, at low cost; and to a process for producing the same; as well as to a ferrous-sintered-alloy member that comprises that ferrous sintered alloy.
  • ferrous-sintered-alloy member In order to cut the manufacturing costs of structural members such as mechanical parts, it is possible to think of utilizing a ferrous-sintered-alloy member in which a powder compact, which is made by pressure compacting a raw-material powder whose major component is iron, is heated to sinter it.
  • a ferrous-sintered-alloy member When using a ferrous-sintered-alloy member, it becomes feasible as well to obtain products (or sintered bodies) that approximate the final configurations, and so it is possible to intend to reduce the manufacturing costs and material costs of structural members, due to cutting the machining processes, upgrading the materials' yields, and the like.
  • the strength of ferrous-sintered-alloy member, and the dimensional stability thereof before and after the sintering come to be important.
  • Fe—Cu—C-system ferrous sintered alloys in which powder compacts that comprise raw-material powders with Fe—Cu—C compositions are sintered, have been used heavily in applications for structural members.
  • Cu is an effective element in upgrading the strength of ferrous sintered alloy, and in stabilizing the dimensional accuracy before and after the sintering. Therefore, in the case of ferrous sintered alloy, Cu has been believed to be its essential element virtually, contrary to common iron and steel materials.
  • Ni is available as an element that has been utilized heavily in ferrous sintered alloys. Similarly to Cu, Ni is also an element that is effective in upgrading the strength of ferrous sintered alloy, and so on. However, Ni powders are also expensive, and hence raise the production costs of ferrous sintered alloys. Moreover, since Ni is an allergic element as well, there may also arise cases where the employment of the same is not preferable.
  • Patent Literature Nos. 1 and 2 and Non-patent Literature Nos. 1 there are disclosed ferrous sintered alloys for which upgrading the strength, and the like, has been intended by containing Mn or Si therein without employing any Cu.
  • ferrous sintered alloys for which upgrading the strength, and the like, has been intended by containing Mn or Si therein without employing any Cu.
  • they are those which are absolutely no more than on laboratory level, and differ from the present invention that will be described later, even in terms of the compositions of Mn and Si, and in terms of the addition methods, and so forth.
  • Patent Literature No. 3 there is disclosed an ultra-high-density compaction method for powder compact.
  • Patent Literature Nos. 4 through 7 there is disclosed a ferrous sintered alloy in which a mixed powder of a pulverized powder of Si—Mn—Fe parent alloy and an iron powder is compression compacted and sintered.
  • the ferrous sintered alloy being disclosed in these patent literatures is compared with a ferrous sintered alloy according to the present invention that will be described later, the former differs from the latter in terms of the following: the compositional ratio of Mn to Si (i.e., Mn/Si); whether or not C is contained substantially regarding the composition of a reinforcement powder itself to be employed, and the like.
  • Patent Literature No. 5 even discloses a ferrous sintered alloy in which Mo is contained in substitute for Ni.
  • its strength is not necessarily sufficient, and hence it requires a heat treatment, such as hardening or tempering, for making it be of high strength furthermore. It is needless to say that such a heat treatment raises the production cost of the ferrous sintered alloy, because it requires a great deal of time and man-hour.
  • Non-patent Literature No. 2 or 3 there is disclosed such a description that a high-strength ferrous alloy (or sinter hardening steel) is obtainable even while heat treatments after the sintering step is being omitted.
  • Non-patent Literature No. 2 differs from the present invention, and so does not disclose any ferrous sintered alloy in which Mn and Si are contained.
  • Non-patent Literature No. 3 there is disclosed a sinter hardening steel that contains Cr, Mn, Si, and Mo.
  • a reinforcement powder such as Fe—Mn—Si—C powders.
  • the present invention is one which has been done in view of such circumstances; and it is an object to provide a production process that makes it possible to obtain ferrous sintered alloys at lower cost, ferrous sintered alloys which make it possible to secure mechanical characteristics, such as strength, and a dimensional stability before and after the sintering, even while inhibiting the employment of Cu or Ni, and to provide ferrous sintered alloys like those, as well as to provide ferrous-sintered-alloy members comprising those ferrous sintered alloys.
  • the present inventors studied earnestly to solve this assignment; as a result of their repeated trial and error, they found out anew that it is possible to obtain ferrous sintered alloys, which are good in terms of the mechanical characteristics, such as strength, and the dimensional stability, at lower cost by means of using reinforcement powders (e.g., Fe—Mn—Si—C powders) whose compositions differ from those of the conventional ones, and then arrived at completing the present invention.
  • reinforcement powders e.g., Fe—Mn—Si—C powders
  • a ferrous sintered alloy according to the present invention is a process for producing ferrous sintered alloy being characterized in that it is equipped with:
  • said reinforcement powder is an Fe—Mn—Si—C powder comprising an Fe alloy or an Fe compound that includes:
  • a reinforcement powder that constitutes a raw-material powder comprises an Fe alloy or Fe compound that includes not only Mn and Si but also C.
  • a ferrous sintered alloy that is obtained using a reinforcement powder e.g., an Fe—Mn—Si—C powder
  • a reinforcement powder e.g., an Fe—Mn—Si—C powder
  • the compositional ranges of Mn, Si and C fall in the specific ranges as aforementioned exhibits good characteristics, such as mechanical characteristics (strength, elongation, hardness, and the like) and dimensional stability, even without employing any Cu powder or Ni powder, and so forth.
  • raw materials for that Fe—Mn—Si—C powder are far much better in terms of pulverlizability (or collapsibility) than that of conventional Fe—Mn—Si powders, and the like. Accordingly, an Fe—Mn—Si—C powder that is homogenous and fine can be obtained with ease relatively.
  • an Fe—Mn—Si—C powder whose granularity is fine and uniform like this it becomes feasible to enhance the dimensional stability and mechanical characteristics of ferrous sintered alloy much more.
  • an Fe—Mn—Si—C powder with the aforementioned compositional ranges, or its raw materials are procurable inexpensively, because they are used heavily as deoxidizing agents (silicomanganese, for instance) that have been employed at the time of steel making.
  • an Fe—Mn—Si—C powder that is good in terms of procurability and being low price, or its raw materials, without ever employing any Cu powder that is expensive relatively.
  • the resulting ferrous sintered alloy is good not only in terms of mechanical characteristics, and so forth, but also in terms of dimensional stability. Therefore, it is possible to intend not only to reduce the heat-treating costs for members that comprise the ferrous sintered alloy, but also to reduce the costs for processing them, and the like.
  • the ferrous sintered alloy being obtained by means of the present invention is one which surpasses conventional ferrous sintered alloys regarding the mechanical characteristics, and the like. Accordingly, when the required specifications for ferrous-sintered-alloy member are at comparable levels with conventional levels, the following become feasible as well: reducing a reinforcement powder in the employed amount per se; substituting an Fe-system powder for a much more inexpensive powder in which the amounts of alloying elements are less; and so forth. If such is the case, it becomes feasible to furthermore advance the reduction of production costs for ferrous sintered alloy or member comprising the same.
  • the aforementioned reinforcement powder e.g., an Fe—Mn—Si—C powder
  • the following reasons or mechanisms, and the like are not necessarily clear: why that powder is, or the raw materials are good in terms of pulverizability; or why the respective characteristics of ferrous sintered alloys that are obtained using that powder are able to upgrade more than those of conventional ones. According to studies done by the present inventors earnestly, they are believed as described below.
  • an Fe—Mn—Si—C powder that is directed to the present invention contains C in a greater amount relatively is believed to be a reason why it is more likely to be pulverized than conventional Fe—Mn—Si powders are.
  • the carbides of manganese e.g., Mn 23 C 6 , Mn 7 C 3 , and the like.
  • Mn, Si, and C that are included in an Fe—Mn—Si—C powder are called the five elements of steel, and are common reinforcement elements in iron and steel materials to be die cast or melt produced.
  • Mn and Si have been hardly employed substantially so far in the field of ferrous sintered alloy. Since Mn and Si are likely to make oxides whose affinity to oxygen is extremely high, it has been believed generally that they make ferrous sintered alloys in which the oxides have intervened inside the metallic structure. Such a circumstance is prominent in a case where Mn and Si are added in a form of powders, which are distinct from an Fe-system powder, into a raw-material powder. Although it is possible to think of using an Fe-system powder in which Mn and Si have been alloyed in advance, the resulting Fe-system powder has become very hard in that case so that the compaction of powder compact per se becomes difficult.
  • Mn and Si are mixed in a raw-material powder to be present as reinforcement powders that are distinct from an Fe-system powder.
  • the sintering of a powder compact that includes Mn and Si is carried out in such an oxidation preventive atmosphere that can sufficiently restrain Mn and Si from being oxidized (i.e., a sintering step).
  • the present inventors succeeded in obtaining a ferrous sintered alloy that exceeds conventional Fe—Cu (—C)-system ferrous sintered alloys, and which demonstrates mechanical characteristics that are at an equivalent level to those of carbon steel for machine structure, with use of an Fe—Mn—Si—C powder as a reinforcement powder, but without ever employing Cu or Ni.
  • a compositional ratio of Mn to Si is limited as described above because of the following: intending to upgrade strengths with additions as less as possible; and making dimensional changes (or expansion magnitude) smaller.
  • the present invention can be grasped not only as the above-described production process, but also as a ferrous sintered alloy being obtained by means of that production process and a variety of members comprising that ferrous sintered alloy (or ferrous-sintered-alloy members).
  • this ferrous sintered alloy (hereinafter, the “ferrous-sintered-alloy members” being involved) can comprise:
  • Mn in an amount of from 0.1 to 2.1%
  • Si in an amount of from 0.05 to 0.6%
  • the balance being made of Fe, and inevitable impurities and/or a modifying element
  • the ferrous sintered alloy can include an alloying element that upgrades its mechanical characteristics, and the like.
  • an alloying element toughness, ductility, and so on, in higher dimension.
  • the ferrous sintered alloy can comprise:
  • Mn in an amount of from 0.1 to 1.4%
  • Si in an amount of from 0.05 to 0.4%
  • the balance being made of Fe, and inevitable impurities and/or a modifying element
  • Mn is an effective element in upgrading the strength of ferrous sintered alloy especially.
  • Mn is too less, its advantage is effected poorly.
  • a ferrous sintered alloy with sufficient strength is obtainable even if Mn is a trace amount depending on the types of alloying elements being included in the raw-material powder.
  • Mn becomes excessive, the elongation of the resulting ferrous sintered alloy decreases so that the ductility declines, and then dimensional changes increase as well so that the dimensional stability is harmed.
  • Si contributes to upgrading the strength of ferrous sintered alloy, it greatly contributes to the dimensional stability of ferrous sintered alloy especially. In particular, this tendency appears greatly in a case where Si and Mn coexist with each other. Whereas Mn has such an action that tends to increase the dimensions of ferrous sintered alloy, Si has such an action that tends to decrease the dimensions of ferrous sintered alloy. It is believed that both of the elements that coexist with each other result in canceling those tendencies one another and then in securing the dimensional stability of ferrous sintered alloy. Si being too less is not preferable because the dimensional stability is effected poorly; Si being excessive is not preferable because the magnitude of dimensional shrinkage has enlarged.
  • C is one of the important reinforcement elements in ferrous sintered alloy. It is needless to say that C diffuses during sintering so that ferrous sintered alloy undergoes solid solution strengthening; and additionally including C in a proper amount makes such heat treatments as the hardening and tempering for ferrous sintered alloy feasible; thereby making it possible to upgrade the mechanical characteristics of ferrous sintered alloy much more. When C is too little, its advantage is effected poorly; when C becomes excessive, the resultant ductility declines.
  • the “modifying element” being referred to in the present description is an element other than Fe, Mn, Si and C (in addition those, Cr and/or Mo), and is an element that is effective in improving the characteristics of ferrous sintered alloy.
  • the types of characteristics to be improved do not matter at all, the following are available: strength, toughness, ductility, dimensional stability, machinability, and the like.
  • the modifying element from 0.1 to 0.3% by mass of V, and so forth, are available.
  • a modifying compound, such as MnS for the introduction of modifying element. In this case, it is preferable to set an amount of MnS from 0.1 to 0.5% by mass, for instance.
  • the respective elements can be combined with each other arbitrarily.
  • the contents of these modifying elements are not limited to the exemplified ranges. Moreover, their contents are usually a trace amount, respectively.
  • the “inevitable impurities” are impurities that are included in a raw-material powder, and are impurities, and the like, which are mixed accidentally during the respective steps; and are elements that are difficult to remove in view of costs, or due to technical reasons, and so forth.
  • P, S, Al, Mg, Ca, and so on are available therefor, for instance.
  • the compositions of modifying element and inevitable impurities are not limited in particular.
  • ferrous sintered alloy or “ferrous-sintered-alloy member” being referred to in the present description, its form does not matter at all.
  • the ferrous sintered alloy can be a workpiece that has a bulk shape, a rod shape, a tube shape or a plate shape, and the like, for instance, or it is also permissible that it can have a final configuration or can even be a structural member per se that can approximate it.
  • the configuration of ferrous sintered alloy (or member) can be approximated to a final-product configuration by means of (near) net shaping.
  • the present invention is not one which excludes cases where Cu and Ni are contained in the ferrous sintered alloy.
  • the cases of containing Cu or Ni in adequate amounts along with the above-described Mn and Si are also involved in the range of the present invention.
  • the “mechanical characteristics” and “dimensional stability” being referred to in the present description depend on the composition of a raw material, the compacting pressure, the sintering conditions (e.g., temperature, time, atmosphere, and the like), and so forth. Therefore, it is not always possible to specify those “mechanical characteristics” and “dimensional stability” unconditionally.
  • a tensile strength one of the mechanical characteristics, can be 550 MPa or more, 600 MPa or more, and further 650 MPa or more, for ferrous-sintered-alloy members for general-purpose applications; and can be 850 MPa or more, 900 MPa or more, 950 MPa or more, and further 1,000 MPa or more, for ferrous-sintered-alloy members that are of high strength.
  • the dimensional stability can fall within ⁇ :0.5%, within ⁇ 0.3%, within ⁇ 0.1%, and further within ⁇ 0.05%, by a rate of dimensional change before and after sintering.
  • the elongation can be 0.5% or more, 1% or more, 1.5% or more, 2% or more, and further 3% or more.
  • FIG. 1 is a diagram that illustrates a configuration of a later-described tensile test specimen
  • FIG. 2 is a graph that shows relationships between reinforcement-powder amounts and dimensional changes regarding ferrous sintered alloys that are directed to later-described Testing Example No. 1;
  • FIG. 3 is a graph that shows relationships between reinforcement-powder amounts and hardnesses regarding ferrous sintered alloys that are directed to Testing Example No. 1;
  • FIG. 4 is a graph that shows relationships between reinforcement-powder amounts and tensile strengths regarding ferrous sintered alloys that are directed to Testing Example No. 1;
  • FIG. 5 is a graph that shows relationships between reinforcement-powder amounts and elongations regarding ferrous sintered alloys that are directed to Testing Example No. 1;
  • FIG. 6 is a graph that shows relationships between FeMSIV-powder amounts and dimensional changes regarding ferrous sintered alloys that are directed to later-described Testing Example No. 2;
  • FIG. 7 is a graph that shows relationships between FeMSIV-powder amounts and hardnesses regarding ferrous sintered alloys that are directed to Testing Example No. 2;
  • FIG. 8 is a graph that shows relationships between FeMSIV-powder amounts and tensile strengths regarding ferrous sintered alloys that are directed to Testing Example No. 2;
  • FIG. 9 is a graph that shows relationships between FeMSIV-powder amounts and elongations regarding ferrous sintered alloys that are directed to Testing Example No. 2;
  • FIG. 10 is a graph that shows relationships between FeMSIV-powder amounts and dimensional changes regarding ferrous sintered alloys that are directed to later-described Testing Example No. 3;
  • FIG. 11 is a graph that shows relationships between FeMSIV-powder amounts and hardnesses regarding ferrous sintered alloys that are directed to Testing Example No. 3;
  • FIG. 12 is a graph that shows relationships between FeMSIV-powder amounts and tensile strengths regarding ferrous sintered alloys that are directed to Testing Example No. 3;
  • FIG. 13 is a graph that shows relationships between FeMSIV-powder amounts and elongations regarding ferrous sintered alloys that are directed to Testing Example No. 3;
  • FIG. 14 is a graph that shows relationships between sintering temperatures and tensile strengths regarding ferrous sintered alloys that are directed to later-described Testing Example No. 4;
  • FIG. 15 is a graph that shows relationships between sintering temperatures and elongations regarding ferrous sintered alloys that are directed to Testing Example No. 4.
  • the constitutions which are selected from those set forth below, are addable to either one of the inventions, and are further addable thereto beyond the categories in a superimposed manner or arbitrarily.
  • a raw-material powder comprises an Fe-system powder, one of the major components of the ferrous sintered alloy, and a reinforcement powder (e.g., an Fe—Mn—Si—C powder) that includes Mn, Si and C.
  • a reinforcement powder e.g., an Fe—Mn—Si—C powder
  • Mn, Si and C e.g., Mn, Si, Si and C.
  • the Fe-system powder can be either a pure iron powder or an iron alloy powder, or can even be a mixture powder of them. It does not matter at all what alloying elements are included in the iron alloy powder. As these alloying elements, first of all, C, Mn, Si, P, S, and the like, are available. Although Mn, Si and C are added as the reinforcement element as well, it is permissible that they can be included in the Fe-system powder in a small amount, respectively. However, when the contents of C, Mn, Si and so forth increase, the resulting Fe-system powder becomes so hard that the compactibility declines.
  • the Fe-system powder is an iron alloy powder
  • Mo, Cr, Ni, V, Co, Nb, W, and the like are available. Since these alloying elements upgrade the heat treatabilities of ferrous sintered alloy, they are effective elements that strengthen the ferrous sintered alloy.
  • the raw-material powder can be prepared so that Mo makes from 0.1 to 2% by mass and/or Cr makes from 0.1 to 5% when the entire raw-material powder is taken as 100% by mass (hereinafter, being simply represented as “%” whenever appropriate).
  • the upper and lower limits of Cr are selectable arbitrarily within its numerical range, it is preferable especially that numerical values, which are selected arbitrarily from the group consisting of 0.1%, 0.3%, 0.5%, 3%, 3.2% and 3.5%, can make the upper and lower limits.
  • the upper and lower limits of Mo are selectable arbitrarily within its numerical range, it is preferable especially that numerical values, which are selected arbitrarily from the group consisting of 0.1%, 0.5%, 0.6%, 0.8%, 1%, 1.5% and 2%, can make the upper and lower limits.
  • these alloying elements can even be supplied as reinforcement powders that are distinct from the Fe-system powder, though it is preferable that the Fe-system powder can be good in terms of the handlability and homogeneity when they are included therein.
  • An FeMS powder that is directed to the present invention comprises an Fe alloy or an Fe compound that includes Mn in an amount of from 58 to 70%, Si in an amount that makes an Mn/Si ratio being from 3.3 to 4.6, C in an amount of from 1.5 to 3%, and the balance being Fe principally, when the entire FeMS powder is taken as 100%.
  • the resulting raw material for the FeMS powder (or FeMS raw material) has turned into an alloy with ductility, and so it becomes difficult to pulverize it into a fine powder. Moreover, an addition amount of the FeMS powder becomes much in the raw-material powder, and hence the cost of the ferrous sintered alloy has risen. On the other hand, an FeMS powder, or a raw material, with too much Mn, Si or C is not preferable, because the procurement cost has risen. For reference, when making a remark regarding the pulverizability of that FeMS powder, the presence of C is important especially.
  • the upper and lower limits of Mn in the FeMS powder are selectable arbitrarily within the aforementioned numerical range, it is preferable especially that numerical values, which are selected arbitrarily from the group consisting of 58%, 60%, 65%, 68% and 70%, can make the upper and lower limits when the entire FeMS powder is taken as 100%.
  • the upper and lower limits of C in the FeMS powder are selectable arbitrarily within the aforementioned numerical range, it is preferable especially that numerical values, which are selected arbitrarily from the group consisting of 1.5%, 2%, 2.5% and 3%, can make the upper and lower limits.
  • an amount of 0 being contained can be 1.5% or less, 1.2% or less, 1% or less, and further 0.8% or less.
  • the amount of 0 in the raw-material powder increases, the reinforcement action resulting from Mn and Si cannot be demonstrated sufficiently.
  • a powder compact with such an ultra high density that a green-compact density ratio (or ⁇ / ⁇ 0 ), namely, a ratio of an apparent density ( ⁇ ) of the powder compact with respect to a theoretical density ( ⁇ 0 ) thereof exceeds 96% O that exists in its interior is not preferable, because it becomes a cause of giving rise to swells (or blisters) in the resulting sintered body.
  • a proportion of the FeMS powder to be blended in the raw material powder differs in compliance with a composition of the FeMS powder or a desirable characteristic of the ferrous sintered alloy (or a composition of the ferrous sintered alloy), it is allowable to be blended in an amount of from 0.05 to 3% when the entire raw-material powder is taken as 100% by mass.
  • the smaller a particle diameter of the FeMS powder is, not only the more the green-compact density ratio and a sintered-body density ratio (or ⁇ ′/ ⁇ 0 ′), namely, a ratio of an apparent density ( ⁇ ′) of a sintered body with respect to a theoretical density ( ⁇ 0 ′) thereof, upgrades, but also the more the dimensional stability and various mechanical characteristics, and the like, tend to upgrade as well.
  • ⁇ ′ apparent density
  • the FeMS powder that is directed to the present invention can be produced at lower cost, because it is likely to turn into a fine powder with ease relatively. Even when FeMS raw materials are used as being pulverized, this FeMS powder can turn into a powder whose particle diameter is 45 ⁇ m or less (or ⁇ 45 ⁇ m) approximately, for instance. This is a sufficiently small particle diameter, even compared with those of conventional reinforcement powders.
  • an FeMS powder that has been classified by means of sieving, and the like. Concretely speaking, it is suitable to use an FeMS powder that is classified to 30 ⁇ m or less, 20 ⁇ m or less, 10 ⁇ m or less, 8 ⁇ m or less, and further to 6 ⁇ m or less, and so forth, in addition to being classified to 45 ⁇ m or less, for instance.
  • the size of particles in an FeMS powder is specified by means of an upper-limit value of the particles. For example, “a particle diameter being 45 ⁇ m or less” specifies that a maximum particle diameter is 45 ⁇ m or less, which will be represented as “ ⁇ 45 ⁇ m” whenever appropriate.
  • the raw-material powder can contain a C-system powder as another reinforcement powder, in addition to an FeMS powder.
  • C in the ferrous sintered alloy can be supplied from an Fe-system powder or an FeMS powder as well, it is preferable to let a C-system powder be present mixedly in the raw-material powder separately or independently to suppress the hardening of Fe-system powders, or to make the compositional adjustment of the C amount easier.
  • a graphite powder or “Gr” powder in which C accounts for 100% virtually is suitable, although it is possible to employ Fe—C alloy powders (or cementite powders), various carbide powders, and the like.
  • the raw-material powder can be prepared eventually so that Mn makes from 0.5 to 1.5%, Si makes from 0.15 to 0.6%, and C makes from 0.2 to 0.9%, when the entire ferrous sintered alloy is taken as 100%.
  • the process for producing ferrous sintered alloy according to the present invention comprises a compacting step and a sintering step mainly, explanations will be made on these steps in this order.
  • the compacting step is a step of pressure compacting the above-described raw-material powder in which an Fe-system powder is mixed with a reinforcement powder, thereby turning the raw-material powder into a powder compact.
  • a compacting pressure on this occasion, a density of the resulting powder compact (or a green-compact density ratio), a configuration of the resultant powder compact, and the like, do not matter at all.
  • the compacting pressure and green-compact density can be set to such an extent at least that the resulting powder compact does not collapse readily.
  • the compacting pressure can be 350 MPa or more, 400 MPa or more, 500 MPa or more, and further 550 MPa or more.
  • the green-compact density ratio it can preferably be 80% or more, 85% or more, and further 90% or more. The higher the compacting pressure and green-compact density ratio become, the more likely it is that the ferrous sintered alloy with higher strength can be obtained; however, it is permissible to select an optimum compacting pressure, or an optimum green-compact density ratio in compliance with applications and specifications of the ferrous sintered alloy.
  • the compacting step can be performed by either cold compacting or warm compacting, and it is even permissible to add an internal lubricant agent in the raw-material powder.
  • an internal lubricant agent one which includes the internal lubricant agent is considered the raw-material powder.
  • Patent Literature No. 3 The present inventors, as there is a disclosure in above-mentioned Patent Literature No. 3, established a compacting method for powder compact, the compacting method which makes ultra-high-pressure compaction, which transcends general compacting pressures, feasible.
  • powder compacting is made feasible at such ultra-high pressures as 750 MPa or more, 800 MPa or more, 900 MPa or more, 1,000 MPa or more, 1,200 MPa or more, 1,500 MPa or more, and further about 2,000 MPa.
  • 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 compacting method (hereinafter, being referred to as “die-wall lubrication warm pressure compaction method” wherever appropriate) can be summarized as follows.
  • the die wall lubrication warm pressure compaction method (i.e., a compacting step) comprises a filling step of filling said raw-material powder in a die with a higher fatty acid-system lubricant applied on the inner face, and a warm pressure compacting step of generating a metallic soap film on the surface of the raw-material powder, which contacts with the die inner face, by warm pressurizing the raw material powder that is disposed within this die.
  • a higher fatty acid-system lubricant agent is applied on the inner face of a die (i.e., an applying step).
  • the higher fatty acid-system lubricant employed herein in addition to a higher fatty acid itself, can even 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 agent, 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 agent is dispersed in water, and so forth, it is likely to spray the higher fatty acid-system lubricant agent onto the inner face of a die uniformly.
  • the water content, and so on evaporate quickly, and accordingly the higher fatty acid-system lubricant agent adheres onto the inner face of the die uniformly.
  • heating temperature of a die although it is preferable to set it in view of the temperature at the warm pressure compacting step being described later, heating it in advance to 100° C. or more, will suffice, for instance. In reality, however, in order to form a uniform film of a higher fatty acid-system lubricant agent, it is preferable to set that heating temperature to less than the melting point of the higher fatty acid-system lubricant agent. For example, in a case of using lithium stearate as a higher fatty acid-system lubricant agent, it is allowable to set that heating temperature to less than 220° C.
  • the higher fatty acid-system lubricant agent in dispersing a higher fatty acid-system lubricant agent in water, and the like, it is preferable to include the higher fatty acid-system lubricant agent in a such proportion as from 0.1 to 5% by mass, and further from 0.5 to 2% by mass, when the entire mass of that aqueous solution is taken as 100% by mass, because a uniform lubricant film is formed on the inner face of a die.
  • a surfactant agent in dispersing a higher fatty acid-system lubricant agent in water, and the like, when a surfactant agent is added to that water in advance, it is possible to intend to disperse the higher fatty acid-system lubricant agent uniformly.
  • a surfactant agent it is possible to use alkyl phenol-system surfactant agents, polyoxyethylene nonyl phenyl ether (EO) 6, polyoxyethylene nonyl phenol ether (EO) 10, anionic nonionic-type surfactant agents, boric acid ester-system emulbon T-80, and so forth, for instance. It is even allowable to combine two or more members of these to employ.
  • lithium stearate when used as a higher fatty acid-system lubricant agent, it is preferable to use three members of the surfactant agents, 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
  • a surfactant agent In order to obtain an aqueous solution of a higher fatty acid-system lubricant agent whose viscosity fits for spraying, it is preferable to set the proportion of a surfactant agent to from 1.5 to 15% by volume when the entirety of that aqueous solution is taken as 100% by volume.
  • an antifoaming agent a silicon-system antifoaming agent, and the like, for instance. It is because, if the bubbling of an aqueous solution is vigorous, a uniform film of a higher fatty acid-system lubricant agent is less likely to be formed on the inner face of a die when spraying it. It is advisable that an addition proportion of an antifoaming agent can be from 0.1 to 1% by volume approximately, for instance, when the entire volume of that aqueous solution is taken as 100% by volume.
  • the particles of a higher fatty acid-system lubricant agent which is dispersed in water, and the like, can have a maximum particle diameter that 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 agent are likely to precipitate in an aqueous solution so that it becomes difficult to apply the higher fatty acid-system lubricant agent onto the inner face of a die uniformly.
  • the metallic soap film is an iron salt film of a higher fatty acid, which is formed by a mechanochemical reaction that has taken place between a higher fatty acid-system lubricant agent and Fe in a raw-material powder under warm high pressure, for instance.
  • a representative example of this is an iron stearate film, which has been generated when lithium stearate or zinc stearate, namely, a higher fatty acid-system lubricant agent, reacts with Fe.
  • “warm,” which is referred to in the present step, can be such an extent of heated state that the reaction between a raw-material powder and a higher fatty acid-system lubricant agent can be facilitated.
  • 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 set the upper limit of that 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 from 98 to 99% by green-compact 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 being 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 ferrous sintered alloy. The higher the sintering temperature is in a shorter period of time the high-strength ferrous sintered alloy is obtainable. In reality, however, when the sintering temperature is too high, liquid phases arise, or dimensional contraction becomes large so that it is not preferable. When the sintering temperature is too low, the diffusion of alloying elements becomes insufficient so that it is not preferable.
  • the sintering temperature can be 900° C. or more, and further 950° C. or more; and it is preferable to be 1,400° C. or less, and further 1,350° C. or less.
  • the ferrous sintered alloy with higher strength when obtaining the ferrous sintered alloy with higher strength, it is allowable to set the sintering temperature to 1,000° C. or more, 1,100° C. or more, and further 1,150° C. or more.
  • the ferrous sintered alloy with higher strength when using an FeMS powder with smaller granularity (concretely speaking, a fine power that has been classified to 8 ⁇ m or less, and further to 5 ⁇ m or less), the ferrous sintered alloy with higher strength is obtainable at a sintering temperature of 1,025° C. or more, and further 1,075° C. or more.
  • the ferrous sintered alloy with higher strength is obtainable at a sintering temperature of 950° C. or more, and further 1,050° C. or more.
  • the sintering time it is allowable to set the sintering time to from 0.1 to 3 hours, and further from 0.1 to 2 hours, while considering the sintering temperature, the specifications, productivity and costs of the ferrous sintered alloy, and the like.
  • the sintering atmosphere can be an oxidation preventive atmosphere.
  • Mn and Si the alloying elements, have extremely strong affinity to O, and so they are elements that are very likely to be oxidized.
  • an FeMS powder like the present invention has a lower oxide-formation free energy than those of the simple substances of Mn and Si, there is such 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 ferrous sintered alloy.
  • the sintering atmosphere can 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 ( ⁇ 30° C. or less, for instance)
  • a nitrogen gas in an amount of a few % by volume (from 2 to 10% by volume when the entirety is taken as 100% by volume, for instance).
  • a continuous sintering furnace which materializes an inert-gas atmosphere with an ultra-low oxygen partial pressure (or N 2 gas), is commercially available (OXYNON furnace produced by KANTO YAKIN KOGYO Co., LTD.).
  • sinter hardening for carrying out hardening by means of cooling that follows heating at the sintering step.
  • a powder compact is usually heated to such a high sintering temperature (from 1,050 to 1,350° C., and further from 1,100 to 1,300° C., for instance) that is higher than the Al transformation temperature (about 730° C. or more) (i.e., a heating step).
  • sinter hardening is done by quenching a sintered body being heated herein from the sintering temperature to the vicinity of room temperature (or down to the Ms point or less) (i.e., a cooling step).
  • a cooling rate on that occasion can be from 0.5 to 3° C./second.
  • the upper and lower limits of this rate are selectable arbitrarily within that numerical range, it is preferable especially that numerical values, which are selected arbitrarily from the group consisting of 0.5° C./second, 0.7° C./second, 2° C./second and 2.5° C./second, can make the upper and lower limits.
  • a faster cooling rate is preferable, because the faster it is the more securely hardening is done; however, in accordance with the production process according to the present invention, hardening can be done sufficiently even when the cooling rate is slower.
  • a forcible cooling apparatus for carrying out quenching is not necessarily needed, and so it is possible to intend to lower costs in terms of facilities as well. Note that such a tendency is prominent when the ferrous sintered alloy further includes Cr and Mo in addition to C, Mn and Si.
  • the highness/lowness of its density does not matter. That is, like the conventional ferrous sintered alloys, it is even allowable to be a low-density ferrous sintered alloy that is made by sintering a powder compact being compacted with a general-purpose compacting pressure, or it is also permissible to be a high-density ferrous sintered alloy that is made by sintering a high-density powder compact being subjected to high-pressure compacting using the above-described die-wall lubrication warm pressure compaction method. In either of the cases, upgrading the ferrous sintered alloy's mechanical characteristics and dimensional stability can be intended by using an FeMS powder.
  • a green-compact density ratio, or a sintered-body density ratio that becomes 92% or more, 95% or more, 96% or more and further 97% or more is preferable, because the resulting strength becomes high strength that is equal to those of sintered bodies, which can be obtained by means of double-pressing and double-sintering (or 2 P 2 S), to those of forge sintered bodies, and further to those of die-cast materials.
  • Such blistering is caused by means of various gases, such as H 2 O, CO and CO 2 , which generate when moisture or oxides, and the like, which have adhered on the particulate surface of a raw-material powder, are reduced or decomposed during the heating of the sintering step. That is, it is believed that these gases are enclosed within sealed holes inside the resulting sintered body in which the respective constituent particles are put in a state of being adhered closely, and then the gases expand during the heating of the sintering step so that blistering occurs in the resultant sintered body.
  • gases such as H 2 O, CO and CO 2
  • Mn and Si (Si especially) in the FeMS powder function as an oxygen getter, respectively, and hence prevents the resulting sintered body from blistering. This is because Mn and Si exhibit stronger affinities to O than to C so that their oxide-generation free energies are lower.
  • a metallic structure of the ferrous sintered alloy that is directed to the present invention does not matter. It is advisable to turn it into structures, such as martensite structures, bainite structures, pearlite structures, ferrite structures and composite structures of these, which are in compliance with required specifications for the ferrous sintered alloy, by adjusting a cooling rate after the sintering step, or by carrying out heat treatments independently of the sintering step. Depending on specifications and compositions of the ferrous sintered alloy, it is even allowable that heat treatment steps, such as annealing, normalizing, aging, refining (e.g., hardening, and tempering), carburizing and nitriding, can be further performed onto the ferrous sintered alloy.
  • heat treatment steps such as annealing, normalizing, aging, refining (e.g., hardening, and tempering), carburizing and nitriding, can be further performed onto the ferrous sintered alloy.
  • ferrous sintered alloy according to the present invention A form of the ferrous sintered alloy according to the present invention, and an intended use therefor do not matter.
  • various pulleys 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.
  • an FeMSII powder (or Fe—Mn—Si powder), one of the FeMS powders, was made by pulverizing an ingot (or solid metal casting) in air, ingot which was die cast in an Ar gas atmosphere and whose blended composition was Fe-50 Mn-30 Si (units: % by mass).
  • an FeMSIV powder (or Fe—Mn—Si—C powder), the other one of the FeMS powders, was made by pulverizing silicomanganese (e.g., JIS #3) in air, silicomanganese which was produced by NIHON DENKO Corp.
  • any one of the powders was processed by pulverization for 30 minutes using a vibration milling machine that was manufactured by CHUO KAKOKI Co., Ltd. Those in such a state that they were as being processed by pulverization will be referred to as “as pulverized” in the present description, and in tables and diagrams that are attached to the present description. These pulverized powders were further sieved, thereby classifying them properly to FeMS powders that had such different granularities as particle diameters being less than 5 ⁇ m (or ⁇ 5 ⁇ m), and the like. For reference, as can be understood from later-described Table 2, particle diameters “as pulverized” were less than 45 ⁇ m (or ⁇ 45 ⁇ m).
  • results of measuring the distributions of granularity for the “as pulverized” FeMSII powder and FeMSIV powder, which had undergone the same pulverizing treatment are shown in Table 2.
  • these distributions of granularity were measured by means of a laser diffraction scattering method using “MT3000II,” a micro-track granularity-distribution measuring apparatus that was produced by NIKKI-SO Co., Ltd.
  • the numeric values that correspond to D10, D50 and D90 are maximum values of particle diameters in which 10%, 50% and 90% of the measured powdery particles are involved, respectively.
  • the FeMSIV powder when taking a look at the FeMSIV powder, since the granularity was 11.5 ( ⁇ m) at D90, it specifies that 90% of the entire particles had particles diameters of 11.5 ⁇ m or less. As can be apparent from comparing the D90 value of the FeMSII powder with that of the FeMSIV powder, the FeMSIV powder was considerably smaller in the entire granularity than was the FeMSII powder, though the same pulverizing treatment was performed onto them, and hence it is understood that the FeMS IV powder was better in terms of the pulverizability (or collapsibility) than was the FeMSII powder.
  • a pure iron powder e.g., a pure Fe powder/“ASC100.29” with diameters of from 20 to 180 ⁇ m, a product of HOEGANAES Corp.
  • a graphite (or “Gr”) powder e.g., “JCPB” produced by NIHON KOKUEN Co., Ltd., and particle diameters being 45 ⁇ m or less
  • JCPB graphite powder
  • test specimens or fundamental test specimens: ⁇ 23 mm ⁇ 10 mm in thickness
  • test specimens or tensile-test specimens with a configuration illustrated in FIG. 1 for being subjected to a tensile test.
  • various types of the mixture powders were first pressure compacted at 588 MPa by use of dies for compaction, thereby obtaining powder compacts that possessed two sorts of said test-specimen configurations (i.e., a compaction step).
  • These powder compacts were sintered in a 1,150-° C. nitrogen-gas atmosphere, respectively, using a continuous sintering furnace (“OXYNON FURNACE” produced by KANTO YAKIN KOGYOU Co., Ltd.) (i.e., a sintering step).
  • a soaking holding time was set at 30 minutes, and an after-sintering cooling rate was set at 30° C./min. (or 0.5° C./sec.).
  • a CO concentration inside the sintering furnace was adapted into being an ultra-low-oxygen-partial-pressure atmosphere of from 50 to 100 ppm (equivalent to from 10 ⁇ 19 to 10 ⁇ 21 Pa by conversion into oxygen partial pressure).
  • an iron-alloy powder e.g., a “CrL” powder/“AstaloyCrL” with particle diameters of from 20 to 180 ⁇ m, a product of HOEGANAES Corp.
  • a pure iron powder in Testing Example No. 1
  • raw-material powders were prepared.
  • the respective powders were blended variously, as shown in Table 4, and were then rotary mixed with a ball mill to prepare a variety of mixture powders (or raw-material powders).
  • powder compacts and sintered bodies were manufactured, powder compacts and sintered bodies which had the same configurations as those of the two sorts of the test specimens being specified in Testing Example No. 1.
  • the powder compacts were compacted by means of the following die-wall lubrication warm compaction method (i.e., a compaction step).
  • a TiN coating treatment had been performed onto the inner peripheral face in each of dies in advance, and then its surface roughness was adapted into being 0.4 Z.
  • the respective dies had been heated to 150° C. with a band heater in advance.
  • an aqueous solution in which lithium stearate (or “LiSt.”), one of the higher fatty acid-system lubricant agents, was dispersed, was applied uniformly onto the inner peripheral face of the heated dies with a spraying gun (i.e., a coating step).
  • a spraying gun i.e., a coating step
  • the aqueous solution used herein is one in which LiSt. was dispersed in one in which a surfactant agent and an antifoaming agent were added to water.
  • a surfactant agent polyoxyethylene nonyl phenyl ethers (EO) 6 and (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 (i.e., 100% by volume).
  • EO polyoxyethylene nonyl phenyl ethers
  • EO 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 (i.e., 100% by volume).
  • LiSt. For LiSt., one whose melting point was about 225° C. and average particle diameter was 20 ⁇ m was used. Its dispersion amount was set at 25 g with respect to 100 cm 3 of the aforementioned aqueous solution.
  • the thus obtained stock solution was diluted by 20 times, and an aqueous solution with 1% final concentration was served for the aforementioned coating step.
  • the respective raw material powders, which were filled in the dies, were compacted with 784 MPa, thereby obtaining powder compacts (i.e., a warm pressure compacting step). It was possible to take any one of the powder compacts out of the dies with a lower ejection force, without causing any galling, and the like, on the inner face of the dies.
  • an iron-alloy powder e.g., a “CrM” powder/“AstaloyCrM” with particle diameters of from 20 to 180 ⁇ m, a product of by HOEGANAES Corp.
  • a componential composition was Fe-3% Cr-0.5% Mo (units: % by mass)
  • the iron-alloy powder i.e., the CrL powder
  • raw-material powders were prepared. Also in this instance, without using any internal lubricant agent, the respective powders were compacted by means of the same die-wall lubrication warm pressure compaction method as that of Testing Example No.
  • the FeMS powder As can be understood from Table 3 and FIG. 4 , the more the FeMS powder increased and moreover the smaller its granularity was, the greater the tensile strength became. Moreover, provided that the blended amount was identical with each other, the FeMS powder made the tensile strength greater than the Cu powder did. In particular, in a case where the FeMSIV powder (e.g., ⁇ 5 ⁇ m) was used, the tensile strength was upgraded by about 20% more than that in a case where the Cu powder was used.
  • the FeMSIV powder e.g., ⁇ 5 ⁇ m
  • the tensile strength became greater suddenly when the amount of the FeMS powder ranged from 1.5 to 2% by mass.
  • the increase in the tensile strength slowed down when the amount of the FeMS powder was 2.5% by mass or more.
  • the FeMSIV powder is indeed more inexpensive in the raw-material cost than are the Cu powder and the FeMSII powder. Besides, since good characteristics are obtainable, good characteristics which are equal to or better than those of conventional ferrous sintered alloys, it is possible to remarkably reduce the production costs of the present ferrous sintered alloy.
  • the dimensional change depended neither on the particle diameter of the FeMS powder nor on the amount of “Gr,” and was stabilized between ⁇ 0.1 approximately.
  • the fine FeMSIV powder e.g., ⁇ 5 ⁇ m
  • the dimensional change was stabilized very much between ⁇ 0.05 approximately, regardless of the amounts of “Gr.”
  • the ferrous sintered alloys which used the fine powder (e.g., ⁇ 5 ⁇ m) of the FeMSIV powder that is directed to the present testing example, hardly caused any dimensional change before and after sintering; they possessed a sufficient hardness; and concurrently they exhibited a very large tensile strength and elongation.
  • ferrous sintered alloys that were thus better in terms of the respective characteristics were obtained by blending the FeMSIV powder in an amount of from 1 to 1.5% by mass approximately, it was understood that it is possible for ferrous sintered alloys being made by doing ultra-high-pressure compaction as well to remarkably reduce the production costs, in the same manner as in the case of Testing Example No. 1.
  • the dimensional change depended neither on the blended amount of the FeMS powder nor on the particle diameter, and was stabilized very much between ⁇ 0.1 approximately.
  • the tensile strength showed a tendency that was similar to that of the hardness. That is, although the more the amount of the FeMS powder increased the larger the tensile strength became, the tensile strength came to hardly increase when the amount of the FeMSIV powder exceeded 1% by mass.
  • the ferrous sintered alloys which used the FeMSIV powder that is directed to the present testing example, hardly caused any dimensional change before and after sintering; they possessed a sufficient hardness; and concurrently they exhibited a very large tensile strength.
  • the ferrous sintered alloys that used the fine powder of the FeMSIV powder e.g., ⁇ 5 ⁇ m
  • any one of the characteristics also turned into a good result. Therefore, in the present testing example as well, it is possible for ferrous sintered alloys being made by doing ultra-high-pressure compaction to remarkably reduce the production costs, in the same manner as in the case of Testing Example No. 2.
  • an FeMS powder e.g., FeMSCII powder
  • a Cu powder distaloyACu (or Fe-10% Cu) with particles diameters of from 20 to 180 ⁇ m, a product of HOEGANAES AB Corp.
  • the FeMSCII powder (or Fe—Mn—Si—C powder) was one which was made by pulverizing silicomanganese (e.g., JIS #1) in air, silicomanganese which was produced by NIHON DENKO Corp. Compared with the FeMSIV powder shown in Table 1, the contents of Mn, Si and O was great but the content of C was less in this FeMSC powder. Moreover, the Mn/Si composition became to be 4.
  • any one of the powders was processed by pulverization for 30 minutes using a vibration milling machine that was manufactured by CHUO KAKOKI Co., Ltd. Those in such a state that they were as being processed by pulverization will be referred to as “as pulverized” or “as R” in the present description, and in tables that are attached to the present description.
  • These pulverized powders were further sieved, thereby classifying them properly to FeMS powders that had such different granularities as particle diameters being less than 5 ⁇ m (or ⁇ 5 ⁇ m), and the like.
  • particle diameters “as pulverized” were less than 45 ⁇ m (or ⁇ 45 ⁇ m).
  • a pure iron powder e.g., a pure Fe powder/“ASC100.29” with particle diameters of from 20 to 180 ⁇ m, a product of HOEGANAES Corp.
  • a graphite (or “Gr”) powder e.g., “JCPB” produced by NIHON KOKUEN Co., Ltd., and particle diameters being 45 ⁇ m or less
  • JCPB graphite powder
  • test specimens or fundamental test specimens: ⁇ 23 mm ⁇ 10 mm in thickness
  • test specimens or tensile-test specimens with a configuration illustrated in FIG. 1 for being subjected to a tensile test.
  • various types of the mixture powders were first pressure compacted at 150° C. with a pressure of 588 MPa by means of the die-wall lubrication warm compaction method explained in the ⁇ Testing Example No. 2> section, thereby obtaining powder compacts that possessed two sorts of said test-specimen configurations (i.e., a warm pressure compaction step).
  • These powder compacts were sintered at a predetermined temperature, which is selected from a range of from 900 to 1,150° C., in a nitrogen-gas atmosphere, respectively, using a continuous sintering furnace (“OXYNON FURNACE” produced by KANTO YAKIN KOGYOU Co., Ltd.) (i.e., a sintering step).
  • a soaking holding time was set at 30 minutes, and an after-sintering cooling rate was set at 30° C./min. (0.5° C./sec.).
  • a CO concentration inside the sintering furnace was adapted into being an ultra-low-oxygen-partial-pressure atmosphere of from 50 to 100 ppm (equivalent to from 10 ⁇ 19 to 10 ⁇ 21 Pa by conversion into oxygen partial pressure).
  • raw-material powders were prepared.
  • the respective powders were blended variously, as shown in Table 9, and were then rotary mixed with a ball mill to prepare a variety of mixture powders (or raw-material powders).
  • the componential compositions (units: % by mass) of the employed Fe-system powders will be shown below one by one.
  • distaloyAE Fe-4 Ni-1.5% Cu-0.5% Mo (with particle diameters of from 20 to 180 ⁇ m);
  • distaloyHP-1 Fe-4 Ni-2% Cu-1.5% Mo (with particle diameters of from 20 to 180 ⁇ m);
  • AstaloyCrL Fe-1.5% Cu-0.2% Mo (with particle diameters of from 20 to 180 ⁇ m);
  • AstaloyCrM Fe-3% Cu-0.5% Mo (with particle diameters of from 20 to 180 ⁇ m);
  • ASC100.29 pure iron (with particle diameters of from 20 to 180 ⁇ m, alternatively, the same being classified to ⁇ 63 ⁇ m). Any one of them was produced by HOEGANAES Corp.
  • test specimens or fundamental test specimens: ⁇ 23 mm ⁇ 10 mm in thickness
  • test specimens or tensile-test specimens with a configuration illustrated in FIG. 1 for being subjected to a tensile test.
  • various types of the mixture powders were first pressure compacted by means of the die-wall lubrication warm compaction method explained in the ⁇ Testing Example No. 2> section, thereby obtaining powder compacts that possessed two sorts of said test-specimen configurations (i.e., a warm pressure compaction step).
  • the pressure compaction was carried out at 150° C. with a pressure of 392 MPa, 588 MPa, 784 MPa or 1,176 MPa.
  • an annealing treatment was further performed at 200° C. for 1 hour in air (i.e., an annealing step).
  • a pure iron powder e.g., a pure Fe powder/“ASC100.29” with particle diameters of from 20 to 180 ⁇ m, a product of HOEGANAES Corp.
  • a graphite (or “Gr”) powder e.g., “JCPB” produced by NIHON KOKUEN Co., Ltd., and particle diameters being 45 ⁇ m or less
  • the FeMSCII powder was classified to ⁇ 5 ⁇ m to use.
  • test specimens or fundamental test specimens: ⁇ 23 mm ⁇ 10 mm in thickness
  • test specimens or tensile-test specimens with a configuration illustrated in FIG. 1 for being subjected to a tensile test.
  • various types of the mixture powders were first of all pressure compacted with predetermined compaction pressures by use of dies for compaction, thereby obtaining powder compacts that possessed two sorts of said test-specimen configurations (i.e., a compaction step).
  • a compaction step onto the raw-material powders in which the amount of the internal lubricant agent was 0.4% by mass, the dies for compaction was heated to 80° C. and then warm compaction was carried out; whereas, onto the raw-material powders in which the same was 0.8% by mass, room-temperature compaction was carried out.
  • These powder compacts were sintered at 1,150° C., respectively (i.e., a sintering step).
  • a soaking holding time was set at 15 minutes, and an after-sintering cooling rate was set at 30° C./min. (or 0.5° C./sec.)
  • an after-sintering cooling rate was set at 30° C./min. (or 0.5° C./sec.)
  • the interior of a sintering furnace was adapted into being a reducing atmosphere in which a hydrogen gas was mixed with a nitrogen gas (e.g., a mixing proportion: N 2 -3% by volume of H 2 , and a dew point: ⁇ 30° C. or less).
  • Table 8A and Table 8B both of them will be simply referred to as “Table 8” combinedly
  • FIG. 14 and FIG. 15 with regard to Testing Example No. 8; they are given in Table 9 with regard to Testing Example No. 5; and they are given in Table 10 with regard to Testing Example No. 6.
  • Sample No. E657 which was made using the FeMSCII powder that had been classified to ⁇ 45 ⁇ m, was turned into a sintered body, which exhibited a tensile strength that exceeded 500 MPa, by doing sintering at 1,050° C. or more.
  • Sample No. E607 which was made using the FeMSCII powder that had been classified to ⁇ 5 ⁇ m, it was possible to predict that a sintered body, which exhibited a tensile strength that exceeded 500 MPa, was obtainable by doing sintering at a temperature that exceeded 1,000° C.
  • E609 which was made using the FeMSCII powder that had been classified to ⁇ 5 ⁇ m along with the iron-system powder that had been classified to ⁇ 63 ⁇ m, was turned into a sintered body, which exhibited a tensile strength that exceeded 500 MPa, by doing sintering at 950° C. or more.
  • any one of the test specimens exhibited an elongation of 2% or more.
  • the elongations became the smallest at around 1,050° C., and were from 2 to 2.5% approximately in any one of the test specimens.
  • the higher or lower temperature than that temperature sintering was done the more the elongation upgraded.
  • Test Sample No. E634 exhibited a hardness and tensile strength that surpassed those of the samples that included Cu and Ni.
  • ferrous sintered alloys i.e., “E877” and “E879”
  • E877 ferrous sintered alloys
  • E879 ferrous sintered alloys according to the present invention were produced while setting up the composition of the raw-material powders, the compacting conditions, the sintering temperature, the sintering atmosphere, and the like, to more practical production conditions that aimed at making efficiency higher, making costs lower, and so forth.
  • the dimensional change was stabilized between ⁇ 0.2% approximately.
  • the samples, which were obtained by doing the compaction with a compacting pressure of 588 MPa were compared with each other, “E877” and “E879” that did not include any Cu showed a better value in any one of the hardness, tensile strength and elongation than did “E881” that included Cu.
  • the samples according to “E877” and “E879” were highly strengthened by further enhancing their compacting pressures.
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US20100074790A1 (en) * 2004-04-23 2010-03-25 Kabushiki Kaisha Toyota Chuo Kenkyusho Iron-based sintered alloy, iron-based sintered-alloy member and production process for them
US20100310405A1 (en) * 2009-06-05 2010-12-09 Toyota Jidosha Kabushiki Kaisha Ferrous sintered alloy, process for producing ferrous sintered alloy and connecting rod
US20150246393A1 (en) * 2014-03-03 2015-09-03 Hyundai Motor Company Method of manufacturing connecting rod by using semi-closed sinter forging
US20180326490A1 (en) * 2017-05-15 2018-11-15 Toyota Jidosha Kabushiki Kaisha Method of producing sintered and forged member
CN111893395A (zh) * 2020-06-09 2020-11-06 黄石市鑫楚精密模具股份有限公司 一种高强度模具钢及其热处理方法
CN112041104A (zh) * 2018-05-23 2020-12-04 住友电工烧结合金株式会社 烧结部件的制造方法及烧结部件
CN113913600A (zh) * 2021-04-12 2022-01-11 河南北方红阳机电有限公司 一种D50Re材料侵彻类壳体热处理工艺方法
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JP5636605B2 (ja) * 2012-10-15 2014-12-10 住友電工焼結合金株式会社 焼結部品の製造方法

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US20100074790A1 (en) * 2004-04-23 2010-03-25 Kabushiki Kaisha Toyota Chuo Kenkyusho Iron-based sintered alloy, iron-based sintered-alloy member and production process for them
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US20150246393A1 (en) * 2014-03-03 2015-09-03 Hyundai Motor Company Method of manufacturing connecting rod by using semi-closed sinter forging
US20180326490A1 (en) * 2017-05-15 2018-11-15 Toyota Jidosha Kabushiki Kaisha Method of producing sintered and forged member
CN108866452A (zh) * 2017-05-15 2018-11-23 丰田自动车株式会社 烧结锻造构件的制造方法
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CN112041104A (zh) * 2018-05-23 2020-12-04 住友电工烧结合金株式会社 烧结部件的制造方法及烧结部件
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CN113913600A (zh) * 2021-04-12 2022-01-11 河南北方红阳机电有限公司 一种D50Re材料侵彻类壳体热处理工艺方法
CN114772729A (zh) * 2022-04-15 2022-07-22 同济大学 一种污水强化脱氮的方法

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