| 摘要 |
PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for forming, which has adequate strength and formability for a skin plate of automobiles, can employ collected scrap of aluminum alloys as a raw material, and can reduce cost, and provide a manufacturing method therefor. SOLUTION: This aluminum alloy sheet includes 2.1-4.0% Si, 0.7-1.5% Mn, 0.2-1.0% Mg and 0.01-0.1% Bi, limits Fe to 0.7% or less, Cu to 0.50% or less, Cr to 0.10% or less, Zn to 1.0% or less and Ti to 0.20% or less as impurity elements, includes the balance Al with unavoidable impurities, has T4 temper, and is characterized by having an average crystal grain size of 50μm or less, and offset yield strength of 70 MPa or higher. The method for manufacturing the aluminum alloy sheet, comprises working the above aluminum alloy into a sheet having a predetermined thickness, then heating it to 451 deg.C or higher at an average heating rate of 5 deg.C/second or higher, performing solution heat treatment which keeps it at the temperature for a period of 5 seconds or more but 300 seconds or less, and then cooling it to the ordinary temperature at the average cooling rate of 5 deg.C/second or higher.
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