MANUFACTURE OF ALUMINUM ALLOY SHEET EXCELLENT IN BAKING HARDENABILITY AND HAVING CONTROLLED NATURAL AGING CHARACTERISTIC

摘要

PROBLEM TO BE SOLVED: To provide a method of manufacture of an aluminum alloy sheet excellent in baking hardenability and having controlled natural aging characteristic, capable of inhibiting an increase in strength due to standing at ordinary temp. and attendant deterioration in formability while maintaining the improvement of strength due to baking finish. ;SOLUTION: An aluminum alloy stock sheet, composed essentially of Mg and Si, is heated at ≥100°C/min temp.-rise rate up to a temp. ranging from 480 to 580°C and not higher than the burning temp. to undergo solution heat treatment and then subjected to hardening treatment at ≥100°C/min temp.-fall rate down to 50-90°C to undergo solution hardening. Subsequently, the sheet is allowed to stand at 50 to 90°C for 1 to 10 hr and further allowed to stand at room temp. The sheet is heated at ≥100°C/min temp.-rise rate, held in the temp. range of 200 to 250°C for ≤30 sec, and then subjected to hardening treatment at ≥100°C/min temp.-fall rate.;COPYRIGHT: (C)1999,JPO