The dies were preheated in an oven at 300 C for at least
1 h in order to reach homogenous temperature throughout
their mass. Just before they were placed in the extrusion
press, the front area of the dies was lubricated with a suspension of graphite in oil. The extruded material was a
CuZn44Pb2 alloy with typical composition presented in
Table 1. A billet of 160 mm diameter and 38 cm long was
used, the piece was heated at 600 C and extrusion was performed under a pressure of approximately 170 atm. After
five continuous strokes the die was replaced in the extrusion press. The used die was cleaned with fine emery paper,
inspected for surface defects and cracks, as well as for
dimensional accuracy and then it was placed again in the
preheating oven for the next use.