(57) The present invention relates to lead free, free cutting copper alloys and methods
of their manufacture. In particular, the present invention is directed to a lead-free,
free-cutting copper alloy which comprises 62 to 78 percent, by weight, of copper;
2.5 to 4.5 percent, by weight, of silicon; 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 aluminium,
and 0.02 to 0.25 percent, by weight, of phosphorous; 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 the remaining percent, by weight, of zinc and wherein the metal
structure of the free cutting copper alloy has at least one phase selected from the
γ (gamma) phase and the κ (kappa) phase.
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