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

Abstract

A process for producing ferrous sintered alloy according to the present invention is characterized in that it is equipped with: a compaction step of pressure compacting a 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; and a sintering step of heating this powder compact in an oxidation preventive atmosphere, thereby sintering the powder compact; and said reinforcement powder is an Fe—Mn—Si—C powder comprising an Fe alloy or an Fe compound that includes: Mn in an amount of from 58 to 70%; Si in an amount making a compositional ratio of the Mn with respect to the Si (i.e., Mn/Si) that is from 3.3 to 4.6; and C in an amount of from 1.5 to 3%; when the entirety is taken as 100% by mass. This Fe—Mn—Si—C powder is procurable inexpensively relatively; besides, ferrous sintered alloys, which are obtained using that, are better in terms of various characteristics than are conventional ferrous sintered alloys. Therefore, it is possible to intend to turn Cu-free ferrous sintered alloys, which are good in terms of their own characteristics, into low-cost ones.

1 . A process for producing ferrous sintered alloy, the process being characterized in that it is a process for producing ferrous sintered alloy being equipped with:
 a compaction step of pressure compacting a raw-material powder in which an Fe-system powder comprising at least either one of pure iron or an iron (Fe) alloy is mixed with a reinforcement powder containing an alloying element other than Fe, thereby turning the raw-material powder into a powder compact; and   a sintering step of heating the powder compact in an oxidation preventive atmosphere, thereby sintering the powder compact; and   said reinforcement powder is an Fe—Mn—Si—C powder comprising an Fe alloy or an Fe compound that includes:   manganese (Mn) in an amount of from 58 to 70% by mass (hereinafter being simply referred to as “%”);   silicon (Si) in an amount making a compositional ratio of the Mn with respect to the Si (i.e., Mn/Si) that is from 3.3 to 4.6; and   carbon (C) in an amount of from 1.5 to 3%;   when the entirety is taken as 100%.   
     
     
         2 . The process for producing ferrous sintered alloy as set forth in  claim 1 , wherein a particle diameter of said Fe—Mn—Si—C powder is 45 μm or less. 
     
     
         3 . The process for producing ferrous sintered alloy as set forth in  claim 1 , wherein a blended amount of the Fe—Mn—Si—C powder in said raw-material powder is from 0.05 to 3% when the entirety of said raw-material powder is taken as 100%. 
     
     
         4 . The process for producing ferrous sintered alloy as set forth in  claim 1 , wherein said raw-material powder further includes a graphite (or “Gr”) powder. 
     
     
         5 . The process for producing ferrous sintered alloy as set forth  claim 1 , wherein said Fe—Mn—Si—C powder has oxygen (O) in an amount of 1.5% or less when the entirety is taken as 100% by mass. 
     
     
         6 . The process for producing ferrous sintered alloy as set forth in claim wherein said raw-material powder is prepared in order that:
 Mn makes from 0.1 to 2.1%;   Si makes from 0.05 to 0.6%; and   C makes from 0.1 to 0.9%;   when the entirety of said ferrous sintered alloy is taken as 100%.   
     
     
         7 . The process for producing ferrous sintered alloy as set forth in  claim 1 , wherein the oxidation preventive atmosphere of said sintering step is a reducing atmosphere in which a hydrogen gas is mixed in a nitrogen gas in an amount of from 2 to 10% by volume when the entirety is taken as 100% by volume. 
     
     
         8 . The process for producing ferrous sintered alloy as set forth in  claim 1 , wherein the oxidation preventive atmosphere is an inert gas atmosphere with such an extremely-low oxygen partial pressure that the oxygen partial pressure corresponds to 10 −19  Pa or less. 
     
     
         9 . The process for producing ferrous sintered alloy as set forth in  claim 1 , wherein the sintering step comprises:
 a heating step of heating said powder compact to a temperature of from 900 to 1,400° C., thereby turning the powder compact into a sintered body; and   a cooling step of cooling the sintered body as heated at a cooling rate of from 0.1 to 3° C./second.   
     
     
         10 . The process for producing ferrous sintered alloy as set forth in  claim 1 , wherein said raw-material powder includes chromium (Cr) in an amount of from 0.3 to 5% and/or molybdenum (Mo) in an amount of from 0.1 to 2% when the entirety is taken as 100%. 
     
     
         11 . The process for producing ferrous sintered alloy as set forth in  claim 10 , wherein said Cr and/or Mo is included in said Fe-system powder. 
     
     
         12 .- 15 . (canceled)