Mixed powder for powder metallurgy and method of manufacturing sintered part

Abstract

A mixed powder for powder metallurgy of the present disclosure includes a metal powder and a graphite powder. The graphite powder includes a spherical graphite powder. Particles of the spherical graphite powder each have an aspect ratio of 4 or less, where the aspect ratio is a ratio of a major axis length to a minor axis length. A content ratio of the spherical graphite powder to the graphite powder is 70% or greater. The graphite powder has an apparent density of 0.2 g/cm3 or greater. The graphite powder has a tap density of 0.5 g/cm3 or greater.

What is claimed is: 
     
         1 . A mixed powder for powder metallurgy comprising:
 a metal powder; and   a graphite powder, wherein   the graphite powder comprises a spherical graphite powder,   particles of the spherical graphite powder each have an aspect ratio of 4 or less, where the aspect ratio is a ratio of a major axis length to a minor axis length,   a content ratio of the spherical graphite powder to the graphite powder is 70% or greater,   the graphite powder has an apparent density of 0.2 g/cm 3  or greater, and   the graphite powder has a tap density of 0.5 g/cm 3  or greater.   
     
     
         2 . The mixed powder for powder metallurgy according to  claim 1 , wherein
 the metal powder comprises an iron-based powder, and   particles of the iron-based powder each comprise iron in an amount greater than 50 mass %.   
     
     
         3 . The mixed powder for powder metallurgy according to  claim 2 , wherein the content ratio of the iron-based powder to the mixed powder for powder metallurgy is 90 mass % or greater. 
     
     
         4 . The mixed powder for powder metallurgy according to  claim 3 , wherein
 the metal powder further comprises a copper powder,   the content ratio of the copper powder to the mixed powder for powder metallurgy is greater than 0 mass % and 8.0 mass % or less, and   the content ratio of the graphite powder to the mixed powder for powder metallurgy is 0.1 mass % to 2.0 mass %.   
     
     
         5 . The mixed powder for powder metallurgy according to  claim 1 , wherein the graphite powder has an average particle size of 3 μm to 40 μm. 
     
     
         6 . A method of manufacturing a sintered part, the method comprising:
 providing the mixed powder for powder metallurgy according to  claim 1 ;   preparing a compact by pressing a raw material powder comprising the mixed powder for powder metallurgy; and   sintering the compact.