Powder mixture

Abstract

A powder mixture of the present invention is characterized in that it comprises: an iron powder or an iron-based alloy powder, wherein a graphite powder is adhered to a surface of the iron powder or the iron-based alloy powder by a binding agent containing a polyolefin wax; and a negatively-charged powder to be mixed with the iron powder or the iron-based alloy powder, and consisting of an iron powder and/or an iron-based alloy powder treated for negatively charging. This enables keeping the good adhering property of a graphite powder in a mixed powder and high flowability as a mixture of the raw material powder.

1 . A powder mixture comprising:
 an iron powder or an iron-based alloy powder, wherein a graphite powder is adhered to a surface of the iron powder or the iron-based alloy powder by a binding agent containing a polyolefin wax; and   a negatively-charged powder to be mixed with the iron powder or the iron-based alloy powder, and consisting of an iron powder and/or an iron-based alloy powder treated for negatively charging.   
     
     
         2 . The powder mixture according to  claim 1 , wherein the polyolefin wax is at least one selected from the group consisting of polyethylene wax and polypropylene wax. 
     
     
         3 . The powder mixture according to  claim 1 , wherein the treatment for negatively charging is coating treatment with at least one selected from the group consisting of an alkylsilane, dialkylsilane, methacrylsilane, alkylhalide silane, and hexaalkyldisilazane. 
     
     
         4 . The powder mixture according to  claim 1 , wherein the maximum particle diameter of the negatively-charged powder is within the range from 1 to 15 μm. 
     
     
         5 . The powder mixture according  claim 1 , wherein an additive amount of the negatively-charged powder is from 0.02 to 0.5 parts by mass relative to 100 parts by mass of the iron powder or the iron-based alloy powder. 
     
     
         6 . The powder mixture according to  claim 1 , wherein the powder mixture further comprises an auxiliary raw material powder, and
 the auxiliary raw material powder is adhered together with the graphite powder by the binding agent to the surface of the iron powder or the iron-based alloy powder.   
     
     
         7 . The powder mixture according to  claim 1 , wherein the powder mixture further comprises an auxiliary raw material powder, and
 the auxiliary raw material powder is contained in a form as being adhered together with the graphite powder by the binding agent to the surface of the iron powder or the iron-based alloy powder as well as in a form of free powder.   
     
     
         8 . The powder mixture according to  claim 1 , wherein the powder mixture further comprises an auxiliary raw material powder, and
 the auxiliary raw material powder is contained in a form of free powder.   
     
     
         9 . The powder mixture according to  claim 6 , wherein a part of the auxiliary raw material powder is an auxiliary raw material powder treated for negatively charging, and
 the negatively-charged powder consists of the auxiliary raw material powder treated for negatively charging instead of the iron powder and/or the iron-based alloy powder treated for negatively charging.   
     
     
         10 . The powder mixture according to  claim 6 , wherein a part of the auxiliary raw material powder is an auxiliary raw material powder treated for negatively charging, and
 the negatively-charged powder further contains the auxiliary raw material powder treated for negatively charging in addition to the iron powder and/or the iron-based alloy powder treated for negatively charging.   
     
     
         11 . The powder mixture according to  claim 1 , wherein the powder mixture further comprises a lubricant powder for compacting, and
 the lubricant powder for compacting is contained in a form of free powder.   
     
     
         12 . The powder mixture according to  claim 7 , wherein a part of the auxiliary raw material powder is an auxiliary raw material powder treated for negatively charging, and
 the negatively-charged powder consists of the auxiliary raw material powder treated for negatively charging instead of the iron powder and/or the iron-based alloy powder treated for negatively charging.   
     
     
         13 . The powder mixture according to  claim 8 , wherein a part of the auxiliary raw material powder is an auxiliary raw material powder treated for negatively charging, and
 the negatively-charged powder consists of the auxiliary raw material powder treated for negatively charging instead of the iron powder and/or the iron-based alloy powder treated for negatively charging.   
     
     
         14 . The powder mixture according to  claim 7 , wherein a part of the auxiliary raw material powder is an auxiliary raw material powder treated for negatively charging, and
 the negatively-charged powder further contains the auxiliary raw material powder treated for negatively charging in addition to the iron powder and/or the iron-based alloy powder treated for negatively charging.   
     
     
         15 . The powder mixture according to  claim 8 , wherein a part of the auxiliary raw material powder is an auxiliary raw material powder treated for negatively charging, and
 the negatively-charged powder further contains the auxiliary raw material powder treated for negatively charging in addition to the iron powder and/or the iron-based alloy powder treated for negatively charging.