| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a thick plate of≥50 mm by hot rolling for an Al-Zn-Mg-Cu-based heat treatment type alloy containing≥1.0% Cu, wherein, by controlling production conditions, the reduction of coarse intermetallic compounds is achieved, thus the remarkable improvement of its ductility (toughness) is achieved while securing its high strength. SOLUTION: Regarding an Al-Zn-Mg-Cu-based alloy containing 1.0 to 3.0% Cu, in a cooling stage after performing a homogenizing treatment at 450 to 520°C for≥1 hr to an ingot, the average cooling rate at least to 400°C is regulated to≥100°C/hr, thereafter, hot rolling is performed to a plate thickness of≥50 mm at a temperature within the range of 300 to 440°C, and, subsequently, solution treatment, quenching and artificial aging treatment are performed so as to obtain a thick plate in which the total area ratio of intermetallic compounds having an equivalent circle diameter of >5μm is controlled to≤2%. Further, electric conductivity of the ingot when measured in a state of being cooled to room temperature after the homogenizing treatment is controlled to be≤40 IACS%. COPYRIGHT: (C)2011,JPO&INPIT
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