Abstract
In this paper, the effect of extruding conditions, which are the billet length, the extruding velocity, the die angle and the reduction %, on the softening of pure Al extruded rods upon annealing is descibed. The results obtained are as follows: (1) When 99.995% Al rods were extruded at about 400° by the same reduction %, in short billets the softening temperature, probably the recrystallization temperature, is raised more than in long billets and the higher the extrusion rate, the faster the softening. (2) A large die angle and a low reduction % raise the temperature described above. (3) 99.85% Al rods extruded at relatively higher temperature (about 510°) are hardened by 400° annealing. This hardening is remarkable at the tail and the surrounding part of the section in rods extruded by relatively low reduction %. When the reduction rate is raised, the hardening becomes weakes and the annealing temperature is lowered.
