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 percent, by weight, of lead, and the remaining percent, by weight, of zinc.

1 - 14 . (canceled) 
     
     
         15 . A free-cutting copper alloy, comprising: 62 to 78 percent, by weight, of copper; 2.5 to 4.5 percent, by weight, of silicon; 0.02 to 0.4 percent, by weight, of lead; at least one element selected from among 0.3 to 3.0 percent, by weight, of tin, 0.2 to 2.5 percent, by weight, of aluminum, and 0.02 to 0.25 percent, by weight, of phosphorus; and at least one element selected from among 0.7 to 3.5 percent, by weight, of manganese and 0.7 to 3.5 percent, by weight, of nickel; and a remaining percentage, by weight, of zinc;
 wherein the copper alloy includes
 (a) a matrix comprising an alpha phase, and 
 (b) one or more phases selected from the group consisting of a gamma phase and a kappa phase; and 
   wherein the one or more phases are formed in the matrix.   
     
     
         16 . A free-cutting copper alloy as recited in  claim 15 , wherein the alloy includes one or more elements selected from the group consisting of tin and phosphorous, and the one or more phases are formed and uniformly dispersed in the matrix. 
     
     
         17 . A free-cutting copper alloy as recited in  claim 15 , made by a process comprising the step of subjecting the alloy to a heat treatment for 30 minutes to 5 hours at 400 to 600° C. so the one or more phases are finely dispersed in the matrix. 
     
     
         18 - 32 . (canceled)