| 摘要 |
PROBLEM TO BE SOLVED: To improve stopper openability and seaming property by using an aluminum alloy sheet containing specific amounts of Mg, Mn, Fe, Si, and Al for a ring-pull-type cap. SOLUTION: This alloy is an aluminum alloy having a composition consisting of, by weight, 2-4% Mg, 0.2-0.7% Mn, 0.1-0.5% Fe, 0.05-0.3% Si, and the balance essentially Al. Among the crystallized substances appearing to the surface, Al-Fe-Mn type crystallized substances have 2-3.5μm average grain size and 0.5-1.5% area occupancy, and Mg-Si type crystallized substances have 1-2.5μm average grain size and 0.001-0.04% area occupancy. An ingot of this alloy is homogenized at 500-550 deg.C, hot-rolled, cold-rolled, and subjected to continuous annealing, as process annealing, under the conditions of >=100 deg.C/min heating and cooling rate and holding at 400-500 deg.C sheet temp. for >=10min. Then, cold rolling is performed at >=60% rolling rate, followed by finish annealing at <=250 deg.C. By this method, the aluminum alloy sheet for ring-pull-type cap can be obtained.
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