Lubricant System For Use In Powder Metallurgy

Abstract

The present invention is directed to metallurgical powder compositions having improved lubricant properties. These compositions of the invention include at least 90 wt. % of an iron-based metallurgical powder; a Group 1 or Group 2 metal stearate; a first wax having a melting range of between about 80 and 100° C.; a second wax having a melting range of between about 80 and 90° C.; zinc phosphate; boric acid; acetic acid; phosphoric acid; and polyvinylpyrrolidone. Methods of compacting the compositions, as well as compacted articles prepared using those methods, are also described.

What is claimed: 
     
         1 . A metallurgical powder composition comprising:
 at least 90 wt. % of an iron-based metallurgical powder;   about 0.05 wt. % to about 1.5 wt. % of a Group 1 metal stearate, a Group 2 metal stearate, or ethylene bissteramide; and   about 0.03 wt. % to about 0.1 wt. % of boric acid.   
     
     
         2 . The metallurgical powder composition of  claim 1 , comprising about 0.08 wt. % to about 1.2 wt. % of the Group 1 metal stearate, Group 2 metal stearate, or ethylene bisstearamide. 
     
     
         3 . The metallurgical powder composition of  claim 2 , comprising about 0.09 wt. % to about 1.1 wt. % of the Group 1 metal stearate, Group 2 metal stearate, or ethylene bisstearamide. 
     
     
         4 . The metallurgical powder composition of  claim 1 , comprising ethylene bisstearamide. 
     
     
         5 . The metallurgical powder composition of  claim 1 , wherein the Group 1 metal stearate or Group 2 metal stearate is lithium stearate. 
     
     
         6 . The metallurgical powder composition of  claim 1 , comprising about 0.03 wt. % to about 0.07 wt. % of boric acid. 
     
     
         7 . The metallurgical powder composition of  claim 6 , comprising about 0.05 wt. % of boric acid. 
     
     
         8 . The metallurgical powder composition of  claim 1 , further comprising a first wax having a melting range of between about 80 and 100° C. 
     
     
         9 . The metallurgical powder composition of  claim 8 , wherein the first wax is Montan wax. 
     
     
         10 . The metallurgical powder composition of  claim 8 , comprising about 0.03 wt. % to about 0.07 wt. % of the first wax. 
     
     
         11 . The metallurgical powder composition of  claim 10 , comprising about 0.05 wt. % of the first wax. 
     
     
         12 . The metallurgical powder composition of  claim 1 , further comprising a second wax having a melting range of between about 80 and 90° C. 
     
     
         13 . The metallurgical powder composition of  claim 12 , wherein the second wax is carnauba wax. 
     
     
         14 . The metallurgical powder composition of  claim 12 , comprising about 0.03 wt. % to about 0.07 wt. % of the second wax. 
     
     
         15 . The metallurgical powder composition of  claim 14 , comprising about 0.05 wt. % of the second wax. 
     
     
         16 . A method of making a metal part comprising compacting the metallurgical powder composition of  claim 1 .