ALUMINUM ALLOY SHEET FOR COLD PRESS FORMING, METHOD FOR MANUFACTURING THE SAME, AND COLD PRESS FORMING METHOD FOR ALUMINUM ALLOY SHEET

摘要

PROBLEM TO BE SOLVED: To make the securing of high formability of an Al-Mg-Si based aluminum alloy sheet mainly used for automobile body sheets compatible with the maintaining of high productivity in forming. SOLUTION: An Al-Mg-Si based aluminum alloy sheet, having undergone natural aging (or being in an under-aged state) after solution treatment, is subjected, before press forming, to partial heating treatment (partial reversion heating treatment) at 150 to 350°C for ≤5 min so as to set the difference in strength (difference in 0.2% proof stress) between the heated part and the non-heated part after cooling at normal temperature to ≥10 MPa. The alloy sheet is subjected to cold press forming in the condition where the heated part with low strength is put in contact with a blank holder part and the non-heated part with high strength is put in contact with a punch shoulder part. The temperature rise rate and the cooling rate in cooling down to ≤100°C are set to be ≥30°C/min, respectively. Further, the period for which the material is allowed to stand at normal temperature after the partial reversion heating treatment until the cold press forming is set to be within 30 days. COPYRIGHT: (C)2009,JPO&INPIT