| 摘要 |
PROBLEM TO BE SOLVED: To produce an Al alloy soft material for upset butt welding securely and sufficiently excellent in the joinability of the upset butt weld zone and having high proof stress of >=85 N/mm2 generally required as that of an automotive two-piece wheel rim material. SOLUTION: An aluminum alloy soft material for upset butt welding has composition containing 2.4 to 2.8% Mg, 0.50 to 0.55% Mn and 0.05 to 0.07% Cr, in which the content of Fe is also controlled to <=0.25%, and Si to <=0.20%, and the balance Al with inevitable impurities and has proof stress of >=85 N/mm2 and electrical conductivity of >=35%IACS. The alloy having the same componential composition is cast, is subjected to homogenizing treatment at 460 to 500 deg.C for 1 to 15 hr, after that, hot rolling is started at <=500 deg.C, the hot rolling is finished at <250 deg.C, and subsequently, the rolled sheet having a final sheet thickness is subjected to softening treatment at 280 to 340 deg.C for 0.5 to 10 hr.
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