Aluminum alloy sheet for can lid

Abstract

An aluminum alloy sheet for a can lid, the sheet including: 0.27 mass % or more and 0.39 mass % or less of Si; 0.35 mass % or more and 0.55 mass % or less of Fe; 0.17 mass % or more and 0.25 mass % or less of Cu; 0.75 mass % or more and 0.95 mass % or less of Mn, and 2.2 mass % or more and 2.8 mass % or less of Mg, wherein, in each of 0°, 45°, and 90° directions to a rolling direction, a minimum evaluation value Smin among evaluation values S calculated by a following formula (1) using a 0.2% yield strength σ0.2, a tensile strength OB, and an average value σfm of the 0.2% yield strength and the tensile strength is 330 MPa or more and 390 MPa or less.S=σfm/(σ0.2/σB)(1)

1 . An aluminum alloy sheet for a can lid, the sheet comprising:
 a silicon (Si) content of 0.27 mass % or more and 0.39 mass % or less;   an iron (Fe) content of 0.35 mass % or more and 0.55 mass % or less;   a copper (Cu) content of 0.17 mass % or more and 0.25 mass % or less;   a manganese (Mn) content of 0.75 mass % or more and 0.95 mass % or less,   a magnesium (Mg) content of 2.2 mass % or more and 2.8 mass % or less; and   a balance consisting of or including aluminum (Al) and inevitable impurities,   wherein, in each of 0°, 45°, and 90° directions to a rolling direction of the alloy sheet, a minimum evaluation value S min , which is a minimum value among evaluation values S calculated by a following formula (1) using a 0.2% yield strength σ 0.2 , a tensile strength σ B , and an average value σ fm  of the 0.2% yield strength and the tensile strength, is 330 MPa or more and 390 MPa or less.   
       
         
           
             
               
                 
                   
                     S 
                     = 
                     
                       
                         σ 
                         fm 
                       
                       / 
                       
                         ( 
                         
                           
                             σ 
                             0.2 
                           
                           / 
                           
                             σ 
                             B 
                           
                         
                         ) 
                       
                     
                   
                 
                 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
       
     
     
         2 . The aluminum alloy sheet for a can lid according to  claim 1 ,
 wherein, in an L-ST cross section of a central part in a width direction of the alloy sheet, a ratio of a total area in the L-ST cross section of Mg 2 Si particles each having an area of 0.3 μm 2  or more is 0.2% or less.   
     
     
         3 . The aluminum alloy sheet for a can lid according to  claim 1 ,
 wherein the minimum evaluation value S min  is 360 MPa or more and 390 MPa or less, and   a value obtained by subtracting a 0.2% yield strength σ 0.2_90°  in the 90° direction to the rolling direction from a 0.2% yield strength σ 0.2_0°  in the 0° direction to the rolling direction is-12 MPa or more and 12 MPa or less.   
     
     
         4 . The aluminum alloy sheet for a can lid according to  claim 2 ,
 wherein a bending operation is an operation of bending 90° a test piece cut into a strip with 12.5 mm in width and 200 mm in length and then returning to a 0° position, a number of cyclic bending N is a number of times of the bending operation until the test piece breaks when the bending operation is repeatedly performed in a direction of a bending ridge line parallel to the rolling direction, and a normalized number of cyclic bending N s  obtained by normalizing the number of cyclic bending N by a sheet thickness t and a following formula (2) is 17 or more.   
       
         
           
             
               
                 
                   
                     
                       N 
                       s 
                     
                     = 
                     
                       N 
                       × 
                       t 
                       / 
                       0.235 
                     
                   
                 
                 
                   
                     ( 
                     2 
                     ) 
                   
                 
               
             
           
         
       
     
     
         5 . The aluminum alloy sheet for a can lid according to  claim 3 ,
 wherein a bending operation is an operation of bending 90° a test piece cut into a strip with 12.5 mm in width and 200 mm in length and then returning to a 0° position, a number of cyclic bending N is a number of times of the bending operation until the test piece breaks when the bending operation is repeatedly performed in a direction of a bending ridge line parallel to the rolling direction, and a normalized number of cyclic bending N s  obtained by normalizing the number of cyclic bending N by a sheet thickness t and a following formula (2) is 17 or more.   
       
         
           
             
               
                 
                   
                     
                       N 
                       s 
                     
                     = 
                     
                       N 
                       × 
                       t 
                       / 
                       0.235 
                     
                   
                 
                 
                   
                     ( 
                     2 
                     )