| 摘要 |
PURPOSE: To produce an aluminum alloy sheet for automobile outer sheet, which has excellent formability and high baking finish hardenability and in which high proof stress is secured after baking finish and product quality after forming and also corrosion resistance are improved. CONSTITUTION: An ingot of an aluminum alloy, having a composition which consists of 0.9-1.3% Si, 0.4-0.6% Mg, 0.05-0.15% Mn, 0.01-0.1% Ti, and the balance Al and in which the contents of Fe and Cu being impurities are limited to <=0.2% and <=0.1%, respectively, is used. After homogenizing treatment, temp. is lowered to <=450 deg.C and hot rolling is started. Hot rolling is finished at 250-350 deg.C. The resulting aluminum alloy plate is subjected, with or without process annealing, to cold rolling at >=70%, to solution heat treatment at >=530 deg.C for <=60sec, and to hardening. The resulting sheet is allowed to stand for >=24hr at room temp. and then heat-treated at 200-250 deg.C for <=60sec. By this method, a proof stress of >=20OMPa can be secured when baking finish treatment is done at 180 deg.C for 1hr after press working.
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