| 摘要 |
PROBLEM TO BE SOLVED: To impart excellent blowup resistance to an alloy sheet by casting a sheet material from the molten metal of an Al alloy having a specified compsn. and successively subjecting the sheet to cold rolling, primary process annealing, cold rolling, secondary process annealing and final cold rolling at specified temps. and speeds. SOLUTION: The molten metal of an Al alloy composed of, by weight, 0.6 to 1.5% Mn, 1.2 to 3.0% Mg, 0.2 to 0.5% Si, 0.1 to 0.4% Cu, 0.1 to 0.5% Fe and 0.001 to 0.2% Ti, and the balance Al is continuously cast into a sheet material of 3 to 8 mm thickness at a solidifying rate of >=100 deg.C/sec. Directly, or after cold rolling, it is subjected to primary process annealing of executing heating at 500 to 590 deg.C for >=1 hr, is cold-rolled, is subjected to secondary process annealing of executing heating at 480 to 590 deg.C at a temp. rising rate of >=10 deg.C/sec and, without holding or holding within 30 sec, executing cooling to <=100 deg.C at a cooling rate of >=10 deg.C/sec and is subjected to final cold rolling of 40 to 75%. In this operation, the primary process annealing is executed by a batch type annealing furnace, and the secondary process annealing is executed by a continuos annealing furnace.
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