Process for the manufacture of a free-cutting aluminum alloy

摘要

A free-cutting aluminum alloy without lead as an alloy element, containing: (a) as alloy elements: 0.5 to 1.0 wt. % Mn; 0.4 to 1.8 wt. % Mg; 3.3 to 4.6 wt. % Cu; 0.4 to 1.9 wt. % Sn; 0 to 0.1 wt. % Cr; 0 to 0.2 wt. % Ti; (b) as impurities: up to 0.8 wt. % Si; up to 0.7 wt. % Fe; up to 0.8 wt. % Zn; up to 0.1 wt. % Pb; up to 0.1 wt. % Bi; up to 0.3 wt. % total of other impurities; and (c) the balance being substantially aluminum. The process includes the steps of semicontinuously casting the above alloy composition followed by homogenization annealing, cooling, heating to a working temperature for extrusion, extruding at a maximum temperature of 380° C., followed by press-quenching and aging. The aging may be a natural aging or an artificial aging. A cold working step and/or a tension straightening step also may be conducted after the press-quenching step. The extruding step includes indirectly extruding.