Aluminum alloy sheet and aluminum alloy sheet manufacturing method

Abstract

In a differential scanning calorimetric curve of an Al—Mg—Si aluminum alloy sheet with a specific composition in which the total content of Mg and Si is greater than 1.2%, a ratio (B/A) of an endothermic peak within the temperature range of 150-230° C. with a height A of 3-10 μW/mg to an exothermic peak within the temperature range of 230° C. or above and below 330° C. with a height B of 20-50 μW/mg is to be within a specified range.

1 . An aluminum alloy sheet, containing: in terms of mass %,
 Mg: 0.3-1.5%,   Si: 0.6-1.5% respectively,   a total of the Mg content and the Si content being greater than 1.2%, and   Al,   wherein, in a differential scanning calorimetric curve of the aluminum alloy sheet,   endothermic peaks whose height A is 3-10 μW/mg exist within a temperature range of 150-230° C.,   exothermic peaks whose height B is 20-50 μW/mg exist within a temperature range of 230° C. or above and below 330° C., and   a ratio B/A of a maximum peak height B out of the exothermic peaks to a maximum peak height A out of the endothermic peaks is greater than 3.5 and less than 15.0.   
     
     
         2 . The aluminum alloy sheet according to  claim 1 , wherein
 the height A of the endothermic peak is 3-8 μW/mg, and   the height B of the exothermic peak is 20-40 μW/mg.   
     
     
         3 . The aluminum alloy sheet according to  claim 1 , further containing:
 in terms of mass %, at least one selected from the group consisting of Cu: 0.02-0.8%, Fe: 0.05-0.5%, Mn: 0.05-0.3%, Zr: 0.04-0.1%, Cr: 0.04-0.3%, V: 0.02-0.1%, Ag: 0.01-0.1%, and Zn: 0.01-0.3%.   
     
     
         4 . A manufacturing method of an aluminum alloy sheet, the method comprising:
 subjecting an aluminum alloy cold rolled sheet to a preliminary temper aging treatment, the aluminum alloy cold rolled sheet containing, in terms of mass %, Mg: 0.3-1.5%, Si: 0.6-1.5%, a total of the Mg content and the Si content being greater than 1.2%, and Al, the preliminary temper aging treatment being for holding the aluminum alloy cold rolled sheet for 5 hours or more and 500 hours or less at a temperature of 30° C.-60° C. within one hour after a solution heat treatment and quenching treatment, thereby, in a differential scanning calorimetric curve before the aluminum alloy cold rolled sheet is subjected to an artificial temper aging treatment, endothermic peaks whose height A is 3-10 μW/mg are made to exist within a temperature range of 150-230° C., exothermic peaks whose height B is 20-50 μW/mg are made to exist within a temperature range of 230° C. or above and below 330° C., and a ratio B/A of the exothermic peak height B to the endothermic peak height A is made to be greater than 3.5 and less than 15.0.   
     
     
         5 . The manufacturing method according to  claim 4 , wherein
 the aluminum alloy sheet further contains, in terms of mass %, at least one selected from the group consisting of Cu: 0.02-0.8% , Fe: 0.05-0.5%, Mn: 0.05-0.3%, Zr: 0.04-0.1%, Cr: 0.04-0.3%, V: 0.02-0.1%, Ag: 0.01-0.1%, and Zn: 0.01-0.3%.   
     
     
         6 . The manufacturing method according to  claim 4 , further comprising:
 performing a preliminary temper aging treatment by holding the aluminum alloy sheet for 5 seconds or more and 300 seconds or less at a temperature of 100° C.-300° C. within one hour after the solution heat treatment and quenching treatment; and   thereafter performing the preliminary temper aging treatment.   
     
     
         7 . The manufacturing method according to  claim 4 , wherein
 the aluminum alloy sheet is painted after being formed, and is subjected to a paint-bake hardening treatment at a heating temperature of 180-230° C. for a heating holding time of 10-30 minutes.   
     
     
         8 . The manufacturing method according to  claim 5 , wherein
 the aluminum alloy sheet is painted after being formed, and is subjected to a paint-bake hardening treatment at a heating temperature of 180-230° C. for a heating holding time of 10-30 minutes.   
     
     
         9 . The manufacturing method according to  claim 6 , wherein
 the aluminum alloy sheet is painted after being formed, and is subjected to a paint-bake hardening treatment at a heating temperature of 180-230° C. for a heating holding time of 10-30 minutes.