PROCESS FOR PRODUCING ALUMINIUM ALLOY SHEET

摘要

A process of producing an aluminum alloy sheet product suitable for forming into automotive parts and exhibiting reduced roping effects. The process involves producing an aluminum alloy sheet product by direct chill casting a n aluminum alloy to form a cast ingot, homogenizing the ingot, hot rolling the ingot to form an intermediate gauge product, cold rolling the intermediate gauge product to form a product of final gauge, and subjecting the final gau ge product to a solutionizing treatment by heating the product to a solutionizi ng temperature, followed by a pre-aging step involving cooling the product to a coiling temperature above 50 ~C, coiling the cooled product at the coiling temperature, and cooling the coiled final gauge product from the coiling temperature above 50 ~C to ambient temperature at a rate less than about 10 ~C per hour to improve T8X temper characteristics of the product. Additionally, a batch anneal step is carried out on the intermediate gauge product or at an intermediate stage of the cold rolling to reduce or eliminate roping tendencies of the alloy sheet product. To maintain a high T8X response, the alloy used in the process has the following composition: 0.4 to 1.1 % by weight magnesium; 0.3 to 1.4 % by weight silicon; 0 to 1.0 % by weight coppe r; 0 to 0.4 % by weight iron; 0 to 0.15 % by weight manganese; 0 to 0.15 % weig ht naturally-occurring impurities (collective total); and the balance aluminum. The invention also relates to a sheet alloy product exhibiting reduced ropin g effects produced by the indicated process.