| 摘要 |
PROBLEM TO BE SOLVED: To provide an aluminum alloy cast material for a weld structural member having excellent weld crack properties and stress corrosion crack resistance while maintaining tensile strength, and a manufacturing method thereof.SOLUTION: An aluminum alloy cast material for a weld structural member includes: 0.4-4.0 mass% of Mg; 3.5-7.0 mass% of Zn; 0.1-0.5 mass% of Cu; over 0.3 mass% and at most 0.8 mass% of Mn; and 0.001-0.15 mass% of Ti, further includes at least one kind of 0.1-0.5 mass% of Cr or 0.05-0.25 mass% of Zr, and regulates Si to 0.5 mass% or less; and Fe to 0.5 mass%, with the balance of Al and inevitable impurity. If crystal grain length in ST direction is G(ST) μm and crystal grain length in LT direction is G(LT) μm, the following equations (1) and (2) are satisfied: 50≤G(LT)≤500..(1), (0.35×G(LT)+5)<G(ST)≤(0.35×G(LT)+85)..(2). |
