| 摘要 |
PROBLEM TO BE SOLVED: To produce an Al material having excellent brightness characteristic at low cost without particularly reducing Fe content by providing a composition containing specific amounts of Mg, Cu, Cr, Fe, and Si and having the balance Al with inevitable impurities and also regulating the amount of precipitation of Cu-type precipitates to a specific value or below. SOLUTION: This Al material has a composition consisting of, by weight, 2.5-3.5% Mg, 0.05-0.50% Cu, 0-0.25% Cr, <=0.06% Fe, <=0.06% Si, and the balance Al with inevitable impurities. Further, the formation of Cu-type precipitates in the course of manufacture is controlled, by which a matrix-potential- increasing action by incorporation of Cu can be obtained with certainty. As to the Cu-type precipitates, it is desirable to regulate the number of precipitates of >=1μm grain size to <=6×10<5> pieces/cm<2> on the average. By applying chemical polishing to such an Al material, a crystallized substance of Fe and a matrix are nearly uniformly dissolved and the formation of pits can be practically prevented, and surface characteristic excellent in smoothness can be obtained.
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