Aluminum alloy sheet for can body, and process for producing the same

Abstract

An Al alloy sheet for a can body and a method for manufacturing the Al alloy sheet are provided. The Al sheet has a predetermined Al alloy composition, and is configured so that the solid solution Mn content thereof after hot rolling is 0.25 mass % or greater, the solid solution Fe content is 0.02 mass % or greater, and the solid solution Si content is 0.07 mass % or greater. The electrical conductivity thereof is 30.0-40.0% IACS, the tensile strength in the rolling direction of a cold-rolled sheet thereof is 280-320 MPa, the tensile strength in the rolling direction after heat treatment at 205° C. for 10 minutes is 270-310 MPa, and the difference between the tensile strength in the rolling direction and the yield stress in the rolling direction after heat treatment at 205° C. for 10 minutes is 50 MPa or less.

1 . A process for producing an aluminum alloy sheet for a can body, the process comprising the steps of:
 surface-machining an aluminum alloy ingot consisting of 0.7-1.3% by mass of Mn, 0.8-1.5% by mass of Mg, 0.25-0.6% by mass of Fe, 0.25-0.50% by mass of Si, 0.10-0.30% by mass of Cu, not more than 0.25% by mass of Zn, not more than 0.10% by mass of Ti and not more than 0.05% by mass of B, and the balance being Al and inevitable impurities;   heating the ingot to a homogenization temperature (T) within a range of 550-620° C. at a heating rate of 30-120° C. per hour;   homogenizing the ingot by holding the ingot at the homogenization temperature (T) for a time not shorter than (145-0.24T) hours;   rough hot rolling the ingot immediately, or after cooling the ingot to a hot rolling starting temperature at least at 500° C. at a cooling rate of 10-90° C. per hour, after finishing the homogenization, so that upon termination of the rough hot rolling, the ingot has a temperature within a range of 430-550° C., and defines a sheet having a thickness of 20-40 mm;   performing finish hot rolling on the sheet so that, upon termination of the finish hot rolling, the sheet has a temperature within a range of 300-390° C., and the sheet has a thickness of 1.5-4.0 mm; and   performing cold rolling on the sheet so that a total working ratio of the sheet is not less than 75%, an average rolling rate in a steady part of a final pass is within a range of 700-1600 m per minute, and the sheet has a thickness of 0.2-1.0 mm.   
     
     
         2 . The process for producing an aluminum alloy sheet for a can body according to  claim 1 , wherein a difference (S1-S2) between an electric conductivity (S1) of the sheet obtained by the finish hot rolling and an electric conductivity (S2) of the sheet obtained by the cold rolling is 0.2-1.6% IACS. 
     
     
         3 . The process for producing an aluminum alloy sheet for a can body according to  claim 1 , wherein an area of particles having a diameter of 0.1 μm-1 μm in the ingot of the aluminum alloy subjected to the homogenization is not less than 3.5% in terms of a microphotograph taken by scanning electron microscope.