High strength aluminum alloy sheet

Abstract

A 6000-series aluminum alloy sheet used for structural materials such as structural materials and reinforcing materials increased in the strength without deteriorating bendability is provided. The strength of the Al—Mg—Si alloy sheet after BH is increased without deteriorating the bendability also after natural aging by defining the microstructure such that the content of Mg and Si are balanced so as to satisfy (Mg content)+(Si content)≧1.5% and 0.6≦(Mg content)/(Si content)≦2.0, and an exothermic peak of a predetermined height is present only by one in a temperature range of 230 to 330° C. of a differential scanning calorimeter measurement curve of the sheet shown in FIG. 1.

What is claimed is: 
     
         1 . A high strength Al—Mg—Si alloy sheet comprising, based on mass %, 0.6 to 2.0% of Mg, 0.6 to 2.0% of Si, and 0.5% or less (not including 0%) of Fe respectively, and satisfying (Mg content)+(Si content)≧1.5% and 0.6≦(Mg content)/(Si content)≦2.0, with the remainder consisting of Al and inevitable impurities, wherein an exothermic peak is present only by one in a temperature range of 230 to 330° C. and the height of the exothermic peak is in a range of 30 to 70 μW/mg in a differential scanning calorimeter measurement curve of the sheet, providing
 that the differential scanning calorimeter measurement is conducted by using DSC 220G manufactured by Seiko Instruments Co. as a test apparatus, a standard specimen of aluminum, and a specimen container made of aluminum, and under identical conditions including a temperature elevation rate of 15° C./min, in an atmosphere of argon (50 ml/min), and at a specimen weight of 24.5 to 26.5 mg, the obtained profile (μW) of the differential scanning calorimeter measurement is divided by a sample weight and normalized (μW/mg), subsequently a region where the profile of the different scanning calorimeter measurement is horizontal in a section of 0 to 100° C. is defined as a reference level of 0, and the height of the exothermic peak from the reference level is measured. 
 
     
     
         2 . The high strength aluminum alloy sheet according to  claim 1 , wherein the aluminum alloy sheet further comprises one or more of 0.5% or less (not including 0%) of Mn, 0.3% or less (not including 0%) of Cr, 0.1% or less (not including 0%) of Zr, 0.1% or less (not including 0%) of V, 0.1% or less (not including 0%) of Ti, 1.0% or less (not including 0%) of Cu, 0.1% or less (not including 0%) of Ag, 0.30% or less (not including 0%) of Zn, and 0.005 to 0.15% of Sn.