Process for manufacturing a substrate for a lithographic printing plate

Claim 1

A process for manufacturing a substrate for a lithographic printing plate characterized by improved mechanical properties including improved ductility and relatively high tensile and fatigue strengths, a fine substantially uniform surface structure suitable for roughening, a stable Al 6 (FeMn) phase that precipitates out on casting and is not transferred into an undesirable AlFe 3 phase during heat treatment, and a ternary AlFeSi phase whih appears as a fine structure comprising providing an aluminum alloy melt consisting essentially of 1.1 to 1.8 wt. % iron, 0.1 to 0.4 wt. % silicon, 0.25 to 0.6 wt. % manganese, up to 0.3 wt. % copper, up to 0.8 wt. % magnesium, up to 2.0 wt. % zinc, 1.0 wt. % total of other elements which each individually do not exceed 0.3 wt. % in concentration, balance essentially aluminum wherein the sum of silicon and manganese is between 0.3 and 1.0 wt. % and said iron and manganese are present in a ratio of iron to manganese between 2.5 and 4.5; casting from said alloy melt a sheet having a uniform thickness of between 5 mm and 12 mm; and rolling said cast sheet to a uniform thickness of between 0.03 mm and 0.6 mm.