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

Abstract

An iron-based sintered alloy of the present invention is an iron-based sintered alloy, which is completed by sintering a powder compact made by press forming a raw material powder composed of Fe mainly, and is such that: when the entirety is taken as 100% by mass, carbon is 0.1-1.0% by mass; Mn is 0.01-1.5% by mass; the sum of the Mn and Si is 0.02-3.5% by mass; and the major balance is Fe. It was found out that, by means of an adequate amount of Mn and Si, iron-based sintered alloys are strengthened and additionally a good dimensional stability is demonstrated. As a result, it is possible to suppress or obsolete the employment of Cu or Ni, which has been believed to be essential virtually, the recyclability of iron-based sintered alloys can be enhanced, and further their cost reduction can be intended.

1 . An iron-based sintered alloy, being completed by sintering a powder compact made by 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, is mixed with a strengthening powder, which is constituted of an Fe—Mn—Si powder composed of iron (Fe), manganese (Mn) and silicon (Si) wherein a compositional ratio (Mn/Si) of the Mn to the Si is 1/3-1, and the iron-based sintered alloy being characterized in that: 
 when the entirety is taken as 100% by mass,    carbon (C) is 0.1-1.0% by mass;    said Mn is 0.01-1.5% by mass;    the sum of the Mn and said silicon (Si) is 0.02-3.5% by mass; and    the major balance is Fe; and    it is good in terms of the strength and dimensional stability.    
   
   
       2 . The iron-based sintered alloy set forth in  claim 1 , when the entirety is taken as 100% by mass, further including chromium (Cr) in an amount of 0.2-5.0% by mass.  
   
   
       3 . The iron-based sintered alloy set forth in  claim 1 , when the entirety is taken as 100% by mass, further including molybdenum (Mo) in an amount of 0.1-3.0% by mass.  
   
   
       4 . The iron-based sintered alloy set forth in  claim 2  having a martensitic structure.  
   
   
       5 . The iron-based sintered alloy set forth in  claim 1  being a Cu-free iron-based sintered alloy, which is free from copper (Cu) substantially, or an Ni-free iron-based sintered alloy, which is free from nickel (Ni) substantially.  
   
   
       6 . A production process for an iron-based sintered alloy by which the iron-based sintered alloy set forth in  claim 1  is obtainable after the following sintering step, the production process, being characterized in that it is equipped with: 
 a compacting 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, which is constituted of an Fe—Mn—Si powder composed of Fe, Mn and Si wherein a compositional ratio (Mn/Si) of the Mn to the Si is 1/3-1; and    a sintering step of heating the powder compact to sinter it in an oxidation preventive atmosphere.    
   
   
       7 . (canceled)  
   
   
       8 . The production process for an iron-based sintered alloy set forth in  claim 6 , wherein said Mn—Si-system powder is an Fe—Mn—Si powder, which is composed of alloy or intermetallic compound of Fe, Mn and Si.  
   
   
       9 . The production process for an iron-based sintered alloy set forth in  claim 8 , wherein said Fe—Mn—Si powder is such that, when the entire Fe—Mn—Si powder is taken as 100% by mass, Mn is 15-75% by mass; Si is 15-75% by mass; the sum of Mn and Si is 35-95% by mass; the major balance is Fe; and oxygen (O) is 0.4% by mass or less.  
   
   
       10 . (canceled)  
   
   
       11 . The production process for an iron-based sintered alloy set forth in  claim 9 , wherein said Fe—Mn—Si powder, when said entire raw material powder is taken as 100% by mass, is included in an amount of 0.5-5% by mass.  
   
   
       12 . The production process for an iron-based sintered alloy set forth in  claim 6 , wherein said strengthening powder is composed of particles whose particle diameters are 100 μm or less.  
   
   
       13 . The production process for an iron-based sintered alloy set forth in  claim 6 , wherein said raw material powder further includes a graphite (Gr) powder.  
   
   
       14 . The production process for an iron-based sintered alloy set forth in  claim 6 , wherein said compacting step is: 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 compacting the raw material powder disposed within the die.    
   
   
       15 . The production process for an iron-based sintered alloy set forth in  claim 6 , wherein said sintering step is a step which is carried out within an ultra-low-oxygen-partial-pressure inert gas atmosphere whose oxygen partial pressure is equivalent to 10 −19  Pa or less.  
   
   
       16 . An iron-based sintered alloy, being completed by sintering a powder compact made by press forming a raw material powder including an Fe-system powder, which is composed of at least one of pure iron and iron alloy, and a strengthening powder, which is constituted of an Fe—Mn—Si powder composed of Fe, Mn and Si wherein a compositional ratio (Mn/Si) of the Mn to the Si is 1/3-1, at least, and the iron-based sintered alloy being 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.    
   
   
       17 . The iron-based sintered alloy set forth in  claim 16  having a martensitic structure.  
   
   
       18 . The iron-based sintered alloy set forth in  claim 1 , wherein a sintered density ratio (ρ′/ρ0′×100%), the ratio of a sintered density (ρ′) to a theoretical density (ρ0′), is 92% or more.  
   
   
       19 . A production process for an iron-based sintered alloy by which the iron-based sintered alloy set forth in  claim 16  is obtainable after the following sintering step, the production process being characterized in that it is equipped with: 
 a compacting 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 is constituted of an Fe—Mn—Si powder composed of Fe, Mn and Si wherein a compositional ratio (Mn/Si) of the Mn to the Si is 1/3-1,; and    a sintering step of heating the powder compact to sinter it in an oxidation preventive atmosphere.    
   
   
       20 . The production process for an iron-based sintered alloy set forth in  claim 19 , wherein said C-system powder is a Gr powder.  
   
   
       21 . The production process for an iron-based sintered alloy set forth in  claim 19 , wherein said strengthening powder is composed of alloy or intermetallic compound of Fe, Mn and Si.  
   
   
       22 . The production process for an iron-based sintered alloy set forth in  claim 21 , wherein said Fe—Mn—Si powder is composed of particles whose particle diameters are 63 μm or less.  
   
   
       23 . The production process for the iron-based sintered alloy set forth in  claim 13 , wherein said compacting step is a step of obtaining such a powder compact that a green density ratio (ρ/ρ0′×100%), the ratio of a green density (ρ) to a theoretical density (ρ0′), is 92% or more.  
   
   
       24 . The production process for an iron-based sintered alloy set forth in  claim 23 , wherein said 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 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 the die.  
   
   
       25 . The production process for an iron-based sintered alloy set forth in  claim 19 , wherein said sintering step comprises: a heating step of carrying out heating in an inert gas atmosphere of 1,100-1,370° C.; and 
 a cooling step of carrying out such cooling that a cooling rate is 1° C./second or less after the heating step; and    the iron-based sintered alloy set forth in  claim 17  is obtainable after the cooling step.    
   
   
       26 . The production process for an iron-based sintered alloy set forth in  claim 25 , wherein said inert gas atmosphere is an ultra-low-oxygen-partial-pressure nitrogen gas atmosphere whose oxygen partial pressure is equivalent to 10 −19  Pa or less.  
   
   
       27 . 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, the iron-based sintered-alloy member being 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.    
   
   
       28 . The iron-based sintered-alloy member set forth in  claim 27 , when the entirety is taken as 100% by mass, further including manganese (Mn) in such an amount that a summed amount together with said Si is 3.5% by mass or less.  
   
   
       29 . The iron-based sintered-alloy member set forth in  claim 27  being a Cu-free iron-based sintered-alloy member, which is free from copper (Cu) substantially.  
   
   
       30 . The iron-based sintered-alloy member set forth in  claim 27  being obtained after single press forming and single sintering.  
   
   
       31 . A production process for an iron-based sintered-alloy member by which the high-density iron-based sintered-alloy member set forth in  claim 27  is obtainable after the following sintering step, the production process being characterized in that it is equipped with: 
 a compacting 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 (ρ/ρ 0 ′×100%), the ratio of a green density (ρ) to a sintered-body theoretical density (ρ 0 ′), is 96% or more; and    a sintering step of heating the powder compact to sinter it in an oxidation preventive atmosphere.    
   
   
       32 . The production process for an iron-based sintered-alloy member set forth in  claim 31 , wherein a sintered density ratio (ρ′/ρ 0 ′×100%), the ratio of a sintered density (ρ′) to a theoretical density (ρ 0 ′) of said iron-based sintered-alloy member, falls within a range of ±1% with respect to said green density ratio.  
   
   
       33 . The production process for an iron-based sintered-alloy member set forth in  claim 31 , wherein said Si-system powder is an Mn—Si-system powder, which is composed of alloy or compound of Mn and Si.  
   
   
       34 . The production process for an iron-based sintered-alloy member set forth in  claim 33 , wherein said Mn—Si-system powder is an Fe—Mn—Si powder, which is composed of alloy or intermetallic compound of Fe, Mn and Si.  
   
   
       35 . The production process for an iron-based sintered-alloy member set forth in  claim 34 , wherein said Fe—Mn—Si powder is such that, when the entire Fe—Mn—Si powder is taken as 100% by mass, Mn is 15-75% by mass; Si is 15-75% by mass; the sum of Mn and Si is 35-95% by mass; the major balance is Fe; and oxygen (O) is 0.4% by mass or less.  
   
   
       36 . The production process for an iron-based sintered-alloy member set forth in  claim 35 , wherein said Fe—Mn—Si powder, when said entire raw material powder is taken as 100% by mass, is included in an amount of 0.01-5% by mass.  
   
   
       37 . The production process for an iron-based sintered-alloy member set forth in  claim 31 , wherein said Si-system powder is composed of particles whose particle diameters are 50 μm or less.  
   
   
       38 . The production process for an iron-based sintered-alloy member set forth in  claim 31 , wherein said compacting step is: 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 filled within the die.    
   
   
       39 . The production process for an iron-based sintered-alloy member set forth in  claim 38 , wherein a compacting pressure of said compacting step is 1,150 MPa or more.  
   
   
       40 . The production process for an iron-based sintered-alloy member set forth in  claim 31 , wherein said sintering step is a step which is carried out within an ultra-low-oxygen-partial-pressure inert gas atmosphere whose oxygen partial pressure is equivalent to 10 −19  Pa or less.  
   
   
       41 . The production process for an iron-based sintered-alloy member set forth in  claim 31 , wherein a sintering temperature of said sintering step is 1,200° C. or more.