Production method of high density iron based forged part

Abstract

A high density iron based forged part such as a mechanical part is produced by a method comprising the following steps in the sequence set forth: (a) preparing iron based powder mixture containing iron based metal powder and graphite powder; (b) preliminarily compacting the iron based powder mixture to form a preliminary compact; (c) sintering the preliminary compact in a non-oxidizing atmosphere whose nitrogen partial pressure is 30 kPa or less, at a temperature of 950° C. or more and of 1300° C. or less to form a forming material; and (d) forging the forming material by closed die forging or enclosed die forging to produce a high density forged part.

What is claimed is:  
     
         1 . A method of producing a high density iron based forged part, comprising the following steps in the sequence set forth: 
 preparing iron based powder mixture containing iron based metal powder and graphite powder;    preliminarily compacting the iron based powder mixture to form a preliminary compact;    sintering the preliminary compact in a non-oxidizing atmosphere whose nitrogen partial pressure is 30 kPa or less, at a temperature of 950° C. or more and of 1300° C. or less to form a forming material; and    forging the forming material by closed die forging or enclosed die forging to produce a high density forged part.    
     
     
         2 . A method as claimed in  claim 1 , wherein the step of preparing the iron based powder mixture includes partially diffusing at least one metal selected from the group consisting of Mn, Mo, Cr, Ni, Cu and V to be adhered to the iron based metal powder.  
     
     
         3 . A method as claimed in  claim 1 , further comprising annealing the forming material after the step of sintering the preliminary compact.  
     
     
         4 . A method as claimed in  claim 3 , wherein the annealing is carried out at a temperature within a range of between 400° C. and 800° C.  
     
     
         5 . A method as claimed in  claim 1 , wherein the preliminary compact has a density of 7.3 Mg/m 3  or less.