| 摘要 |
PROBLEM TO BE SOLVED: To obtain a sheet for spinning working free from generation of fine cracking and surface roughening, moreover short in heat treating time and good in productivity by making the sheet into the one composed of Al contg. specified amounts of Mg, Mn and Cr, in which grains are recrystallized, and the recrystallized grain size in an orthogonal cross-section parallel to a rolling direction is controlled to a value equal to or below the specified one. SOLUTION: This is an Al alloy rolled sheet contg., by weight, 2.4 to 3.0% Mg, 0.5 to 1.0% Mn and 0.05 to 0.20% Cr, and the balance Al, in which grains are recrystallized, and the recrystallized grain size in the orthogonal cross-section parallel to the rolling direction is <=100μm by the size equivalent to a circle. For producing this sheet, an Al alloy ingot having this compsn. is held at 410 to 470 deg.C, is subjected to 1st precipitating treatment, is moreover heated, is held at 500 to 550 deg.C and is subjected to 2nd precipitating treatment, after that, hot rolling is finished at >=380 deg.C, next, it is cold-rolled to control its sheet thickness to the desired one, or is subjected to the annealing treatment in the middle of the cold rolling, and after that, at the time of executing the final annealing treatment, total rolling ratio in the cold rolling before the final annealing treatment is controlled to >=25%.
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