Improvement of product strength and formability in stamping of Al–Mg–Si alloy sheets having bake hardenability by resistance heat and artificial aging treatments

Abstract

Resistance heat and artificial aging treatments were introduced into a stamping operation to improve the product strength and formability of Al–Mg–Si alloy sheets having bake hardenability used for automobile body panels. In this treatment, the sheets undergo re-solution by resistance heat treatment, composed of resistance heating and water quenching just before the stamping. Stamped sheets are artificially aged just after the stamping to increase product strength. In the experiment, Al–0.60% Si–0.74% Mg alloy sheets were chosen as an example of Al–Mg–Si alloy sheets having bake hardenability. The re-solution solution treatment of the sheets was sufficiently accomplished by rapid resistance heat treatment, and formability of the sheets was improved. Hardness of the formed products was increased by artificial aging. It was found that the present process is effective in improving the product strength and formability of Al–Mg–Si alloy sheets having bake hardenability due to the compactness and rapidness.