| 摘要 |
PROBLEM TO BE SOLVED: To obtain an Al alloy sheet for a PP (pilfer proof) cap having satisfactory cap openability in spite of its extremely high strength, having a satisfactory earing ratio, free from curving of a printing characteristic and further having excellent surface quality. SOLUTION: The Al alloy comprises >2.1 to 3.0% Mg, 0.1 to 0.3% Fe, >0.3 to 0.5% Mn and 0.05 to 0.25% Si, and the balance Al with inevitable impurities. In the Al alloy, the area ratio of all crystallized products is 1.5 to 3.0%, further, tensile strength is 250 to 300 MPa, and the earing rates of the ears formed in the direction of 45°are≤2%. When hot rolling is performed by a hot rough rolling mill and a hot finish rolling mill, finish rolling starting temperature is controlled to≤450°C, finishing temperature is controlled to≤310°C, and the recrystallization ratio in the hot-rolled sheet is controlled to≤30%. Next, the hot-rolled sheet is subjected to cold rolling, is thereafter subjected to process annealing at 400 to 550°C under the condition where it is not held or is held within 2 min, is next subjected to finish cold rolling at the total rolling ratio of 30 to 65%, and is then subjected to stabilization treatment. COPYRIGHT: (C)2007,JPO&INPIT
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