Aluminum alloy sheet with excellent formability and paint bake hardenability and method for production thereof

Abstract

A sheet of a 6000 type aluminum alloy containing Si and Mg as main alloy components and having an excellent formability sufficient to allow flat hemming, excellent resistance to denting, and good hardenability during baking a coating, which exhibits an anisotropy of Lankford values of more than 0.4 or the strength ratio for cube orientations of the texture thereof of 20 or more, and exhibits a minimum bend radius of 0.5 mm or less at 180° bending, even when the offset yield strength thereof exceeds 140 MPa through natural aging; and a method for producing the sheet of the aluminum alloy, which includes the steps of subjecting an ingot to a homogenization treatment, cooling to a temperature lower than 350° C. at a cooling rate of 100° C./hr or more, optionally to room temperature, heating again to a temperature of 300 to 500° C. and subjecting it to hot rolling, cold rolling the hot rolled product, and subjecting the cold rolled sheet to a solution treatment at a temperature of 400° C. or higher, followed by quenching.

1 . An aluminum alloy sheet with excellent formability and paint bake hardenability, which comprises Si and Mg as major alloy components, in which an anisotropy of Lankford values is more than 0.4. 
     
     
         2 . The aluminum alloy sheet with excellent formability and paint bake hardenability according to  claim 1 , which comprises 0.5-2.0% of Si and 0.2-1.5% of Mg, with the proviso that the relationships 0.7 Si %+Mg %≦2.2% and Si−0.58 Mg %≧0.1% are satisfied, and the balance consisting of Al and impurities. 
     
     
         3 . The aluminum alloy sheet according to  claim 2 , which further comprises up to 0.5 mass % of Zn. 
     
     
         4 . The aluminum alloy sheet according to  claim 2 , which further comprises at least one of up to 1.0 mass % of Mn, up to 0.3 mass % of Cr, up to 0.2 mass % of V and up to 0.2 mass % of Zr. 
     
     
         5 . The aluminum alloy sheet according to  claim 3 , which further comprises at least one of up to 1.0 mass % of Mn, up to 0.3 mass % of Cr, up to 0.2 mass % of V and up to 0.2 mass % of Zr. 
     
     
         6 . The aluminum alloy sheet of  claim 2 , which further comprises up to 1.0 mass % of Cu. 
     
     
         7 . The aluminum alloy sheet according to  claim 2 , which further comprises at least one of up to 1.0 mass % of Mn, up to 0.3 mass % of Cr, up to 0.2 mass % of V and up to 0.2 mass % of Zr and up to 1.0 mass % of Cu. 
     
     
         8 . The aluminum alloy sheet according to  claim 2 , which further comprises at least one of up to 0.1 mass % of Ti and up to 50 ppm of B. 
     
     
         9 . The aluminum alloy sheet according to  claim 2 , which further comprises at least one of up to 1.0 mass % of Mn, up to 0.3 mass % of Cr, up to 0.2 mass % of V, and up to 0.2 mass % of Zr and at least one of up to 0.1 mass % of Ti and up to 50 ppm of B. 
     
     
         10 . The aluminum alloy sheet according to  claim 2 , which further comprises up to 1.0 mass % of Cu and at least one of up to 0.1 mass % of Ti and up to 50 ppm of B. 
     
     
         11 . The aluminum alloy sheet according to  claim 2 , which further comprises at least one of up to 1.0 mass % of Mn, up to 0.3 mass % of Cr, up to 0.2 mass % of V and up to 0.2 mass % of Zr, and up to 0.1 mass % of Cu and at least one of up to 0.1 mass % of Ti and up to 50 ppm of B. 
     
     
         12 . The aluminum alloy sheet according to  claim 3 , which further comprises up to 1.0 mass % of Cu. 
     
     
         13 . The aluminum alloy sheet according to  claim 3 , which further comprises at least one of up to 1.0 mass % of Mn, up to 0.3 mass % of Cr, up to 0.2 mass % of V and up to 0.2 mass % of Zr and up to 1.0 mass % of Cu. 
     
     
         14 . The aluminum alloy sheet according to  claim 3 , which further comprises at least one of up to 0.1 mass % of Ti and up to 50 ppm of B. 
     
     
         15 . The aluminum alloy sheet according to  claim 3 , which further comprises at least one of up to 1.0 mass % of Mn, up to 0.3 mass % of Cr, up to 0.2 mass % of V and up to 0.2 mass % of Zr and at least one of up to 0.1 mass % of Ti and up to 50 ppm of B. 
     
     
         16 . The aluminum alloy sheet according to  claim 3 , which further comprises up to 1.0 mass % of Cu and at least one of up to 0.1 mass % of Ti and up to 50 ppm of B. 
     
     
         17 . The aluminum alloy sheet according to  claim 3 , which further comprises at least one of up to 1.0 mass % of Mn, up to 0.3 mass % of Cr, up to 0.2 mass % of V and up to 0.2 mass % of Zr, and up to 1.0 mass % of Cu and at least one of up to 0.1 mass % of Ti and up to 50 ppm of B.