| 摘要 |
PROBLEM TO BE SOLVED: To obtain an aluminum alloy extruded material having high strength and excellent in dimensional accuracy. SOLUTION: A billet, having a composition which consists of 0.6-1.0% Mg, 0.5-0.8% Si, 0.1-0.3% Fe, 0.005-0.05% Ti, 0.001-0.01% B, <=0.4% Cu, one or >=2 kinds among <0.2% Mn, <0.1% Cr, and <0.1% Zr under the condition of Mn+Cr+Zr<3%, and the balance essentially Al and in which the excess Si computed from (excess Si)=(Si%-0.58×Mg%) is regulated to 0.1-0.4%, is used. This billet is extruded so that the temp. immediately after extrusion becomes 510-570 deg.C. The resultant extruded material is cooled at a rate of <(30 to 150) deg.C/min until 420 deg.C is reached. Subsequently, the extruded material is cooled through the temp. region from 420 to 280 deg.C at a rate of >=150 deg.C/min and then cooled through the temp. region from 280 to 150 deg.C at a rate of >=30 deg.C/min. The resultant extruded material is subjected to aging treatment at 160 to 210 deg.C for 1 to 15 hr.
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