| 摘要 |
PROBLEM TO BE SOLVED: To provide an aluminum alloy substrate for a lithographic plate, capable of giving uniform rough surface by means of surface roughing treatment and excellent in annealing softening resistance and thermal fatigue resisting strength. SOLUTION: This substrate is an aluminum alloy sheet produced by subjecting an aluminum alloy ingot, having a composition consisting of, by weight, 0.2-0.5% Fe, 0.02-0.15% Si, <=0.05% Cu, and the balance Al with inevitable impurities, to soaking treatment at 500-620 deg.C for >=1hr, to hot rolling at 380-480 deg.C starting temp. and 280-380 deg.C finishing temp., and to cooling down to <=250 deg.C at <=5 deg.C/min average cooling rate and then applying cold rolling to the resultant hot rolled plate to final sheet thickness at >=60% total rolling rate without applying heat treatment, such as annealing, after hot rolling. Moreover, the ratio of recrystallization at the surface of the plate cooled down to ordinary temp. after hot rolling is regulated to >=80%, and also the average width of crystalline grains, in a direction orthogonal to rolling direction, at the surface of the sheet at final sheet thickness is regulated to <50μm. |
