Patent ID: 7883589

Claim:
A free-cutting copper alloy, consisting essentially of 71.5 to 78.5 percent, by weight, of copper; 2.0 to 4.5 percent, by weight, of silicon; 0.005 percent and up to but less than 0.02 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 61−50Pb≦ X− 4 Y≦ 66+50Pb, wherein Pb is the percent, by weight, of lead, X is the percent, by weight, of copper, and Y is the percent, by weight, of silicon, wherein each of the following additional relationships are satisfied: α phase of about 30% or more of the total phase area of the alloy; 0%≦β phase≦5% of the total phase area of the alloy; 0%≦μ phase≦20% of the total phase area of the alloy; and 18-500(Pb) %≦κ phase+γ phase+0.3(μ phase)−β phase≦56+500(Pb) % of the total phase area of the alloy.