| 摘要 |
PURPOSE: To produce an Al alloy sheet for substrate for offset printing plate, having high strength and high heat resistance and excellent in handling property and durability, by specifying a composition consisting of Mn, Si, Fe, Cu, and Al and also specifying crystalline grain size and tensile strength, respectively. CONSTITUTION: In a rolled sheet of an Al alloy having a composition consisting of, by weight, 0.5-2.0% Mn, 0.10-1.0% Si, 0.15-1.0% Fe, 0.05-0.10% Cu, and the balance Al with inevitable impurities, the average crystalline grain size in the direction orthogonal to the rolling direction is regulated to <=200μm, and also a difference in tensile strength between the rolling direction and the direction perpendicular to the rolling direction is regulated to <=10%. By this procedure, a high quality Al alloy sheet substrate for offset printing plate, suitable for surface roughening treatment, can be obtained. This Al alloy sheet can be obtained by casting an Al alloy with the composition, holding the cast Al alloy at >=580 deg.C for >=3hr to apply homogenizing treatment to it, hot-rolling it at 400-520 deg.C starting temp. and 220-320 deg.C finishing temp., and subjecting the resulting plate to cold rolling, process annealing, and final cold rolling at 30-70% rolling rate.
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