| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing an Al alloy for extrusion and an Al alloy extruded material in which, at the time of extruding an Al-Zn-Mg series aluminum alloy, even in the case that the extruding rate is speeded up, the seizure of the aluminum alloy is prevented, and good surface properties can be secured. SOLUTION: As for the structure of an Al-Zn-Mg series aluminum alloy before extrusion, among precipitates in the aluminum alloy matrix, MgZn2 precipitates are allowed to enter into solid solution in the aluminum alloy, or the average size of the MgZn2 precipitates is regulated to <0.01μm, and furthermore, the average size of Al-transition metal series precipitates is regulated to <0.2μm. Moreover, for obtaining this structure, at the time of subjecting the Al-Zn-Mg series aluminum alloy to homogenizing heat treatment after casting, the heat treating temp. is regulated to the range of 430 to 480 deg.C, and cooling after the heat treatment is executed by water cooling.
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