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

Abstract

Provided are an Al alloy sheet having excellent characteristics for use as a can body, and a method for manufacturing the Al alloy sheet. A sheet having an Al alloy comprising a predetermined alloy composition as the material thereof, wherein an Al alloy sheet for a can body 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 . An aluminum alloy sheet for a can body, which is formed of a cold-rolled sheet obtained by cold rolling a hot-rolled sheet comprising an aluminum alloy 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,
 wherein the hot-rolled sheet includes not less than 0.25% by mass of solid-solubilized Mn, not less than 0.02% by mass of solid-solubilized Fe and not less than 0.07% by mass of solid-solubilized Si, and has an electric conductivity of 30.0-40.0% IACS,   and wherein the cold-rolled sheet has a tensile strength (TS) of 280-320 MPa in a rolling direction and a tensile strength (ABTS) of 270-310 MPa in the rolling direction after heat treatment at 205° C. for 10 minutes, and a difference between the tensile strength (TS) in the rolling direction and a yield strength (ABYS) in the rolling direction after heat treatment at 205° C. for 10 minutes is not larger than 50 MPa.   
     
     
         2 . An aluminum alloy hot-rolled sheet for a can body, comprising an aluminum alloy 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,
 wherein the hot-rolled sheet includes not less than 0.25% by mass of solid-solubilized Mn, not less than 0.02% by mass of solid-solubilized Fe and not less than 0.07% by mass of solid-solubilized Si, and has an electric conductivity of 30.0-40.0% IACS.   
     
     
         3 . An aluminum alloy sheet for a can body, comprising an aluminum alloy 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,
 wherein the sheet has a tensile strength (TS) of 280-320 MPa in a rolling direction and a tensile strength (ABTS) of 270-310 MPa in the rolling direction after heat treatment at 205° C. for 10 minutes, and a difference between the tensile strength (TS) in the rolling direction and a yield strength (ABYS) in the rolling direction after heat treatment at 205° C. for 10 minutes is not larger than 50 MPa.   
     
     
         4 . The aluminum alloy sheet for a can body according to  claim 3 , which has an electric conductivity of 28.4% IACS-39.8% IACS. 
     
     
         5 . A process for producing an aluminum alloy sheet for a can body, comprising steps of:
 providing an ingot of an aluminum alloy 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;   performing hot rolling on the ingot of the aluminum alloy so as to obtain a hot-rolled sheet including not less than 0.25% by mass of solid-solubilized Mn, not less than 0.02% by mass of solid-solubilized Fe and not less than 0.07% by mass of solid-solubilized Si, and having an electric conductivity of 30.0-40.0% IACS; and   performing cold rolling on the hot-rolled sheet so as to form a cold-rolled sheet wherein a tensile strength (TS) in a rolling direction is 280-320 MPa and a tensile strength (ABTS) in the rolling direction after heat treatment at 205° C. for 10 minutes is 270-310 MPa, and wherein a difference between the tensile strength (TS) in the rolling direction and a yield strength (ABYS) in the rolling direction after heat treatment at 205° C. for 10 minutes is not larger than 50 MPa.   
     
     
         6 . A process for producing an aluminum alloy sheet for a can body, comprising steps of:
 surface-machining an ingot of an aluminum alloy 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;   performing homogenization by keeping the ingot at the homogenization temperature (T) for a time not shorter than (145-0.24 T) hours;   performing rough hot rolling on the ingot immediately or after cooling the ingot to a starting temperature of hot rolling not lower than 500° C. at a cooling rate of 10-90° C. per hour after finishing the homogenization, such that a temperature of the ingot upon termination of the rough hot rolling is within a range of 430-550° C., so as to form a sheet having a thickness of 20-40 mm;   performing finish hot rolling on the sheet such that a temperature of the sheet upon termination of the finish hot rolling is within a range of 300-390° C., so that the sheet has a thickness of 1.5-4.0 mm, and   performing cold rolling on the sheet such that a total working ratio of the sheet is not less than 75% and an average rolling rate in a steady part of a final pass is within a range of 700-1600 m per minute, so that the sheet has a thickness of 0.2-1.0 mm.   
     
     
         7 . The process for producing an aluminum alloy sheet for a can body according to  claim 6 , wherein the difference (S1-S2) between the electric conductivity (S1) of the sheet obtained by the finish hot rolling and the electric conductivity (S2) of the sheet obtained by the cold rolling is 0.2-1.6% IACS. 
     
     
         8 . The process for producing an aluminum alloy sheet for a can body according to  claim 6 , 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. 
     
     
         9 . A can body for beverages, which is formed of the aluminum alloy sheet according to  claim 1 . 
     
     
         10 . The can body for beverages according to  claim 9 , which is subjected to a predetermined coating and baking process. 
     
     
         11 . A can body for beverages, which is formed of the aluminum alloy sheet according to  claim 3 . 
     
     
         12 . The can body for beverages according to  claim 11 , which is subjected to a predetermined coating and baking process.