| 摘要 |
A billet 100 mm in diameter with structural hardening, of the A-U4SG type, which has the following composition (in percentage by weight): Fe : 0.42, Si : 0.91, Cu : 4.24, Mn : 0.82, Mg : 0.51, Al: remainder, is subjected to a heat treatment consisting of being held at 605 DEG C for 15 minutes. This treatment has the effect of bringing a proportion of the alloy of approximately 13 % by weight into the liquid state and of causing an onset of change of the solid dendritic phase towards a globular form. Immediately after this heat treatment, this billet is spun in a 800-t spinning press whose container is preheated to 420-450 DEG C and the die is water-cooled, in the form of a section of rectangular cross-section of 40 x 3 mm, leaving the press at approximately 450 DEG C. This section is quenched with air as it leaves the die. After annealing for 8 hours at 175 DEG C, the section obtained has mechanical characteristics (elastic limit and breaking load) which are improved when compared with those of a section obtained by spinning under the same conditions, after the same heat treatment prior to the spinning, but without performing air-quenching on leaving the press. |
