Aluminum alloy sheet for forming and method for producing the same

Abstract

In an aluminum alloy sheet for forming, when hardness (Hv) is measured at intervals of 1/16 of a sheet thickness in a sheet thickness direction from a depth position at ½ the sheet thickness to a sheet surface, hardness distribution is plotted with the hardness (Hv) on a vertical axis and distance (mm) from the depth position at ½ the sheet thickness on a horizontal axis, a relation between the hardness (Hv) and the distance (mm) from the depth position at ½ the sheet thickness is approximated by a linear function based on the plotted hardness distribution, and a slope A of the linear function is determined by the least squares method, a product obtained by multiplying the slope A by the sheet thickness (mm) is 10 to 28. It is possible to provide an aluminum alloy sheet that can improve the effect of reducing the springback amount by bottoming.

1 . An aluminum alloy sheet for forming wherein, when hardness (Hv) is measured at intervals of 1/16 of a sheet thickness in a sheet thickness direction from a depth position at ½ the sheet thickness to a sheet surface, hardness distribution is plotted with the hardness (Hv) on a vertical axis and distance (mm) from the depth position at ½ the sheet thickness on a horizontal axis, a relation between the hardness (Hv) and the distance (mm) from the depth position at ½ the sheet thickness is approximated by a linear function based on the plotted hardness distribution, and a slope A of the linear function is determined by the least squares method, a product obtained by multiplying the slope A by the sheet thickness (mm) is 10 to 28. 
     
     
         2 . The aluminum alloy sheet for forming according to  claim 1 , wherein, when a relation between the hardness (Hv) and the distance (mm) from the depth position at ½ the sheet thickness is approximated by a linear function based on, among the plotted hardness distribution, the plotted hardness distribution from a depth position at ¼ the sheet thickness to the sheet surface, a slope B1 of the linear function is determined by the least squares method, a relation between the hardness (Hv) and the distance (mm) from the depth position at ½ the sheet thickness is approximated by a linear function based on, among the plotted hardness distribution, the plotted hardness distribution from the depth position at ½ the sheet thickness to the depth position at ¼ the sheet thickness, and a slope B2 of the linear function is determined by the least squares method, an absolute value of a difference (B1−B2) between the slope B1 and the slope B2 is 10 or less. 
     
     
         3 . The aluminum alloy sheet for forming according to  claim 1 , wherein the aluminum alloy sheet has a tensile strength of 140.0 MPa or more. 
     
     
         4 . The aluminum alloy sheet for forming according to  claim 1 , wherein the aluminum alloy sheet is made of a JIS 5000-series aluminum alloy. 
     
     
         5 . The aluminum alloy sheet for forming according to  claim 1 , wherein the aluminum alloy sheet is made of a JIS 6000-series aluminum alloy. 
     
     
         6 . A method for producing an aluminum alloy sheet for forming made of a JIS 5000-series aluminum alloy, the method comprising performing at least one of: (1a) setting a cold working rate at 70.0% or more; (2a) performing a skin pass at a reduction of 1.0 to 10.0% after stabilizing treatment, (3a) performing three or more passes of cold working at a reduction of 25.0% or less per pass; and (4a) performing treatment with a leveler after the stabilizing treatment. 
     
     
         7 . A method for producing an aluminum alloy sheet for forming made of a JIS 6000-series aluminum alloy, the method comprising performing at least one of: (1b) setting a cold working rate at 70.0% or more; (2b) performing a skin pass at a reduction of 1.0 to 10.0% after artificial aging treatment; (3b) performing three or more passes of cold working at a reduction of 25.0% or less per pass; and (4b) performing treatment with a leveler after solution treatment or after the artificial aging treatment.