| 摘要 |
PROBLEM TO BE SOLVED: To provide an aluminum alloy casting having excellent durability so as to be free from fatigue fracture even in an environment in which thermal stress and mechanical stress are repeatedly applied. SOLUTION: This aluminum alloy casting has a composition containing 7.0 to 9.0% Si, 1.5 to 2.0% Cu, 0.3 to 0.6% Mg and <=0.15% Fe and, if required, containing one or more kinds selected from 0.01 to 0.25% Ti, 0.001 to 0.05% B and 0.003 to 0.03% Sr, and the balance substantially Al. The content of hydrogen is controlled to <=0.2 cc/100 g, and dendrite arm spacing is controlled to <=30μm. The casting is produced by casting an aluminum alloy having a prescribed composition at a cooling rate of >=5 deg.C/sec, thereafter heating the alloy to 530±10 deg.C under the setting of the temperature rising rate at >=450 deg.C to <=100 deg.C/hr, holding the alloy to the same temperature region for 2 to 10 hr, next performing cooling at a cooling rate of >=50 deg.C/sec and, within 1 hr after the cooling, subjecting the alloy to holding treatment at 160 to 200 deg.C for 4 to 12 hr.
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