Iron powder composition

Abstract

The invention concerns a method of preparing an iron-based powder comprising the steps of mixing and heating an iron-based powder, at least one oligomer amide type lubricant, at least one fatty acid and optionally one or more additives to a temperature above the melting point of the lubricant and subsequently cooling the obtained mixture. The invention also comprises the mixture of the iron-based powder, the oligomer amide type lubricant and the fatty acid.

1 . A powder composition comprising an iron-based powder, at least one oligomer amide type lubricant, a fatty acid and optionally one or more additives.  
     
     
         2 . Composition according to  claim 1 , characterised in that the melting point of the fatty acid is lower than that of the amide lubricant.  
     
     
         3 . Composition according to any one of the claims  1 - 2 , characterised in that the fatty acid has 10-22 C atoms,  
     
     
         4 . Composition according to  claim 3 , characterised in that the fatty acid is selected from the group consisting of oleic acid, stearic acid, palmitic acid or combinations thereof.  
     
     
         5 . Composition according to any one of the claims  1 - 4  wherein the oligomer amide type lubricant may be represented by the following formula 
 D—C m —B—A—B—C m —D  
 wherein D is —H, COR, CNHR, wherein R is a straight or branched aliphatic or aromatic group including 2-21 C atoms  
 C is the group —NH (CH) n  CO— 
 B is amino or carbonyl  
 A is alklylen having 4-16 C atoms optionally including up to 4 O atoms  
 m is an integer 1-10  
 n is an integer 5-11  
 
     
     
         6 . Composition according to  claim 5 , characterised in that the lubricant has the chemical structure wherein D is COR, wherein R is an aliphatic group 16-20 C atoms, C is —NH (CH) n CO— wherein n is 5 or 11; B is amino; A is alkylene having 6-14 C atoms optionally including up to 3O atoms, and m is an integer 2-5.  
     
     
         7 . Composition according to any one of the claims  1 - 6 , characterised in that the amount of the fatty acid is 0.015-0.15, preferably 0.02-0.08 and most preferably 0.03-0.07% calculated on the total weight of the powder composition.  
     
     
         8 . Composition according to any one of the claims  1 - 7 , characterised in that the composition includes one or more additives selected form the group consisting of binders, flow agents, processing aids and hard phases.  
     
     
         9 . Composition according to any one of the claims  1 - 8 , characterised in that the flow agent is used in an amount from about 0.005 to about 2 percent by weight, preferably from about 0.01 to about 1 percent by weight, and more preferably from about 0.025 to about 0.5 percent by weight, based on the total weight of the metallurgical composition and has an average particle size below about 40 nanometers.  
     
     
         10 . Composition according to  claim 9 , characterised in that the flow agent is a silicon dioxide.  
     
     
         11 . Method of preparing an iron-based powder comprising the steps of: 
 a) mixing and heating an iron-based powder, at least one oligomer amide type lubricant, at least one fatty acid and optionally one or more additives to a temperature above the melting point of the lubricant; and    b) cooling the obtained mixture.    
     
     
         12 . Method according to  claim 10 , characterised in that the mixture obtained in step a) is cooled to a temperature below the melting point of the lubricant and above the melting point of the fatty acid and that a pulverulent flow agent is added to the mixture.