Metal member and manufacturing method thereof

Abstract

A metal member related to the present invention is provided with crystal grains of a metal and a granular reinforcing substance formed at boundaries of the crystal grains. The reinforcing substance includes grains of a shape with a grain area equivalent grain size larger than 1/100 of a grain area equivalent grain size of the crystal grains. The granular reinforcing substance preferably includes grains with a grain area equivalent grain size smaller than ⅕ of the grain area equivalent grain size of the crystal grains. Additionally, the granular reinforcing substance preferably includes grains of a shape wherein a value of a length, in a first direction in which a length thereof is longest, divided by a length of a longest part in a direction orthogonal to the first direction is smaller than 5. A metal member with a high strength at high temperatures is manufactured by metal powder injection molding.

1 . A metal member comprising:
 crystal grains of a metal; and   a granular reinforcing substance formed at boundaries of the crystal grains,   wherein the reinforcing substance includes grains of a shape with a grain area equivalent grain size larger than 1/100 of a grain area equivalent grain size of the crystal grains.   
     
     
         2 . The metal member according to  claim 1 ,
 wherein the reinforcing substance includes grains of a shape with a grain area equivalent grain size smaller than ⅕ of the grain area equivalent grain size of the crystal grains.   
     
     
         3 . The metal member according to  claim 1 ,
 wherein the reinforcing substance includes grains of a shape so that a value of a length, in a first direction in which a length thereof is longest, divided by a length of a longest part in a direction orthogonal to the first direction is smaller than 5.   
     
     
         4 . The metal member according to  claim 3 ,
 wherein 95% or more of the reinforcing substance is formed so that a value of a length, in a first direction in which a length thereof is longest, divided by a length of a longest part in a direction orthogonal to the first direction, is smaller than 5.   
     
     
         5 . The metal member according to  claim 1 ,
 wherein the reinforcing substance includes a plurality of types of substances and is formed to surround the crystal grains.   
     
     
         6 . The metal member according to  claim 1 ,
 wherein the reinforcing substance includes any of carbon, nitrogen or oxygen.   
     
     
         7 . A manufacturing method of metal member by injection molding, comprising:
 a mixing step of mixing metal powder, reinforcing powder and binder;   an injection molding step of forming an injection molded body by injection molding of mixed powers;   a degreasing step of removing the binder from the injection molded body and forming an intermediate molded body; and   an incinerating step of incinerating the intermediate molded body,   wherein the reinforcing powder includes a reinforcing substance,   wherein a maximal grain size of the reinforcing powder is larger than 1/100 of a maximal grain size of the metal powder, and   wherein the metal powder and the reinforcing powder both are mixed in a powder state in the mixing step.   
     
     
         8 . The manufacturing method of metal member by injection molding according to  claim 7 ,
 wherein the maximal grain size of the reinforcing powder is smaller than ⅕ of a maximal grain size of the metal powder.   
     
     
         9 . The manufacturing method of metal member by injection molding according to  claim 7 , further comprising:
 a step of determining a carbon concentration of the metal powder on a basis of a mass of the reinforcing powder to be mixed.