| 摘要 |
PURPOSE:To produce the titled Al substrate having excellent flatness, by subjecting an Al alloy contg. specific ratios of Mg and Mn to hot rolling and cold rolling at the specific working ratio, blanking the disk blank of the alloy and subjecting the same to stress relief annealing at a specific temp. CONSTITUTION:The Al alloy contg., by weight, 3-6% Mg, 0.05-1% Mn and the balance consisting of Al with impurities is melted to cast and subjected to a soaking treatment and hot rolling to form to a hot coil. Said alloy is then applied to an intermediate annealing or cold rolling and intermediate annealing at need, and after that, is subjected to the cold rolling in such a manner that the cold working rate of the final coil is regulated to the range of 10-50% to form to the prescribed plate thickness. The disk blank of the alloy is then blanked and is subjected to the stress relief annealing at the temp. below the recrystallization temp. (about 260-320 deg.C). By this method, the Al substrate for a magnetic disk having high strength and having the excellent flatness, particularly the flatness without a change in the lapse of time is stably obtd.
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