Copper/zinc alloys having low levels of lead and good machinability

Abstract

The free-cutting copper alloy according to the present invention contains a greatly reduced amount of lead in comparison with conventional free-cutting copper alloys, but provides industrially satisfactory machinability. The free-cutting alloys comprise 69 to 79 percent, by weight, of copper, 2.0 to 4.0 percent, by weight, of silicon, 0.02 to 0.4, by weight, of lead, and the remaining percent, by weight, of zinc.

1 . A free-cutting copper alloy, consisting essentially of 69 to 79 percent, by weight, of copper, 2.0 to 4.0 percent, by weight, of silicon; 0.02 to 0.4 percent, by weight, of lead; and a remaining percentage, by weight, of zinc, wherein the percent by weight of copper and silicon in the copper alloy satisfy the relationship  
         60≦ X− 3 Y≦ 70,  wherein 
 X is the percent, by weight, of copper, and  
 Y is the percent, by weight, of silicon; and  
 the copper alloy has a metal construction comprising multiple phases integrated to form a composite phase, wherein the composite phase is an α phase matrix having a total phase area comprising not more than 5% of a β phase, and 5-70% of the total phase area is provided by at least one phase selected from the group consisting of a γ phase, a κ phase, and a μ phase.  
   
     
     
         2 - 14 . (canceled)