Sky Aluminium Co., Ltd.

Zhu Yan

Mamoru Matsuo

A system for heat treating a rolled strip of Al--Mg--Si alloy includes a primary heating zone for solution treating the strip at 480.degree. C. or higher, a first cooling zone for cooling the strip at a rate of at least 100.degree. C./min. to 100.degree. C. or lower, a secondary heating zone for heating the strip to 120.degree.-250.degree. C. within 10 minutes for thereby adjusting a proof stress of 70-120 N/mm.sup.2 directly or after holding for 10 minutes or less, a coiler for winding the strip into a coil at 140.degree. C. or lower, and a unit for holding the coil at 50.degree.-140.degree. C. for at least 3 hours. The process from solution treatment to winding is continuous as well as from winding to stabilizing treatment. The strip has improved formability and bake hardenability and a minimized secular change at room temperature.

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Tokyo, Japan

Zhu Yan