Aluminum-alloy rolled sheet and production method thereof

Abstract

An aluminum-alloy rolled sheet has a chemical composition containing Si: 0.80 mass % or more and 2.5 mass % or less, Mn: 0.40 mass % or more and 1.2 mass % or less, Mg: 0.25 mass % or more and 0.65 mass % or less, and Fe: 0.050 mass % or more and 0.45 mass % or less, the remainder being composed of Al and unavoidable impurities. The uniform elongation of the aluminum-alloy rolled sheet in the direction perpendicular to rolling is 19.5% or greater, and the value of the anisotropy of Lankford values Δr is −0.50 or greater and 0 or less. The aluminum-alloy rolled sheet has properties such that, after introducing a pre-strain of 2%, and thereafter performing aging treatment under conditions of a hold temperature of 170° C. and a hold time of 20 minutes, the 0.2% yield strength is 175 MPa or greater.

1 . An aluminum-alloy rolled sheet: having a chemical composition containing Si: 0.80 mass % or more and 2.5 mass % or less, Mn: 0.40 mass % or more and 1.2 mass % or less, Mg: 0.25 mass % or more and 0.65 mass % or less, and Fe: 0.050 mass % or more and 0.45 mass % or less, the remainder being composed of Al and unavoidable impurities;
 the uniform elongation value in a direction perpendicular to rolling being 19.5% or greater;   having properties such that, after introducing a pre-strain of 2%, and thereafter performing aging treatment under conditions of a hold temperature of 170° C. and a hold time of 20 minutes, the 0.2% yield strength in the direction perpendicular to rolling is 175 MPa or greater; and   the value Δr of the anisotropy of the Lankford values expressed by the following Equation (1) being −0.50 or greater and 0 or less.   
       
         
           
             
               
                 
                   
                     
                       Δ 
                       ⁢ 
                       r 
                     
                     = 
                     
                       
                         ( 
                         
                           
                             r 
                             0 
                           
                           - 
                           
                             2 
                             × 
                             
                               r 
                               45 
                             
                           
                           + 
                           
                             r 
                             90 
                           
                         
                         ) 
                       
                       / 
                       2 
                     
                   
                 
                 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
         (It is provided that, in Equation (1) above, r 0  represents the Lankford value in the rolling direction, r 45  represents the Lankford value in the 45° direction relative to the rolling direction, and r 90  represents the Lankford value in the direction perpendicular to rolling.) 
       
     
     
         2 . The aluminum-alloy rolled sheet according to  claim 1 , wherein the aluminum-alloy rolled sheet further contains one or two or more elements selected from the group consisting of Cu: 0.0010 mass % or more and 1.0 mass % or less, Cr: 0.0010 mass % or more and 0.10 mass % or less, Zn: 0.0010 mass % or more and 1.0 mass % or less, and Ti: 0.0050 mass % or more and 0.20 mass % or less. 
     
     
         3 . The aluminum-alloy rolled sheet according to  claim 1 or 2 , wherein the Cu content in the aluminum-alloy rolled sheet is less than 0.40 mass %. 
     
     
         4 . The aluminum-alloy rolled sheet according to any one of  claims 1 to 3 , wherein the aluminum-alloy rolled sheet contains Ti: 0.0050 mass % or more and 0.20 mass % or less and B: more than 0 ppm by mass and 500 ppm by mass or less. 
     
     
         5 . The aluminum-alloy rolled sheet according to any one of  claims 1 to 4 , wherein the aluminum-alloy rolled sheet further contains one or two elements selected from the group consisting of Zr: more than 0 mass % and less than 0.10 mass % and Bi: more than 0 mass % and less than 0.20 mass %. 
     
     
         6 . The aluminum-alloy rolled sheet according to any one of  claims 1 to 5 , wherein the Lankford value r 45  in the 45° direction relative to the rolling direction of the aluminum-alloy rolled sheet is 0.45 or greater, and the average value r ave  of the Lankford values of the aluminum-alloy rolled sheet expressed by the following Equation (2) is 0.65 or greater. 
       
         
           
             
               
                 
                   
                     
                       r 
                       ave 
                     
                     = 
                     
                       
                         ( 
                         
                           
                             r 
                             0 
                           
                           + 
                           
                             2 
                             × 
                             
                               r 
                               45 
                             
                           
                           + 
                           
                             r 
                             90 
                           
                         
                         ) 
                       
                       / 
                       4 
                     
                   
                 
                 
                   
                     ( 
                     2 
                     ) 
                   
                 
               
             
           
         
       
     
     
         7 . The aluminum-alloy rolled sheet according to any one of  claims 1 to 6 , wherein the tensile strength TS in the direction perpendicular to rolling of the aluminum-alloy rolled sheet is 230 MPa or greater, and the difference TS−YS between the tensile strength TS and the 0.2% yield strength YS of the aluminum-alloy rolled sheet is 110 MPa or greater. 
     
     
         8 . A production method of the aluminum-alloy rolled sheet according to any one of  claims 1 to 7 , wherein:
 an ingot having the aforementioned chemical composition is prepared;   subsequently, a hot-rolled sheet is prepared by performing hot rolling on the ingot;   after the hot rolling, one or more cold rolling passes are performed on the hot-rolled sheet, without performing intermediate annealing, to prepare an aluminum-alloy rolled sheet; and   after the cold rolling, the aluminum-alloy rolled sheet is subjected to solution heat treatment by heating the aluminum-alloy rolled sheet and thereafter performing quenching on the aluminum-alloy rolled sheet.   
     
     
         9 . The production method of the aluminum-alloy rolled sheet according to  claim 8 , wherein aluminum scrap material is used as at least a portion of the casting materials, when preparing the ingot.