| 摘要 |
PROBLEM TO BE SOLVED: To produce an Al alloy sheet excellent in press-formability, ductility, strength and baking hardenability by casting an Al alloy having a specified compsn. composed of Mg, Si, Cu, Fe and Al at a specified cooling rate or above, executing cold rolling, thereafter heating it at a specified temp. in a solution treating stage and executing rapid-cooling within specified time. SOLUTION: An alloy contg., by weight, 0.30 to 0.70% Mg, 0.80 to 2.00% Si, 0 to 0.50% Cu and <=0.30% Fe, contg. 0.10 to 0.50% Mn according to desire, and the balance Al with inevitable impurities is solidified at a cooling rate of >=150 deg.C/sec, and while hot rolling is executed, it is cast. Then, this Al alloy is subjected to cold rolling to regulate its sheet thickness into prescribed one. At the time of subjecting the obtd. Al alloy sheet to solution treatment, this is heated at 520 to 560 deg.C preferably at a temp. rising rate of about >=10 deg.C/sec, and within 30 sec after it reaches this temp., cooling is executed at the cooling rate of that in forced air cooling or above. The maximum dimensions of insoluble intermetallic compounds in the Al alloy are regulated to <=1.0μm, and the quantity of the elements to enter into solid solutions is also increased.
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