Aluminum alloy sheet with excellent high-temperature property for bottle can

Abstract

An aluminum alloy sheet for bottle cans superior in high-temperature properties and capable of preventing thermal deformation thereof in coating and heat treatment and securing can strength after the heat treatment. The aluminum alloy sheet has the following composition: Mn 0.7-1.5%, Mg 0.8-1.7%, Fe 0.1-0.7%, Si 0.05-0.5%, Cu 0.1-0.6%, with the remainder being Al and inevitable impurities, and has a crystal structure elongated in a rolling direction and with an aspect ratio of crystal grains of 3 or more as determined through an examination from above of a part located at the center in the through-thickness direction. In the sheet, the amount of solute Cu is 0.05-0.3%, which means the amount of Cu in a solution separated from a precipitate exceeding 0.2 m in particle size by the extracted residue method using hot phenol, and the amount of solute Mg is 0.75-1.6%, which means the amount of solute Mg separated from a precipitate exceeding 0.2 m in particle size by the extracted residue method using hot phenol. The aluminum alloy sheet can have improved high-temperature properties without impairing its formability.

1 . An aluminum alloy sheet for bottle cans superior in high-temperature properties, the aluminum alloy sheet comprising the following composition: Mn 0.7-1.5% (mass %, also in the following), Mg 0.8-1.7%, Fe 0.1-0.7%, Si 0.05-0.5%, Cu 0.1-0.6%, with the remainder being Al and inevitable impurities, and comprising a crystal structure elongated in a rolling direction and with an average aspect ratio of crystal grains of 3 or more as determined through an examination from above of a part located at the center in the through-thickness direction, wherein the amount of solute Cu is 0.05-0.3%, which means the amount of Cu in a solution separated from a precipitate exceeding 0.2 μm in particle size by the extracted residue method using hot phenol, and the amount of solute Mg is 0.75-1.6%, which means the amount of solute Mg separated from a precipitate exceeding 0.2 μm in particle size by the extracted residue method using hot phenol. 
   
   
       2 . The aluminum alloy sheet for bottle cans superior in high-temperature properties according to  claim 1 , wherein the difference between a maximum value and a minimum value of tensile strength in 0°, 45° and 90° directions relative to the rolling direction is 25 MPa or less and the difference between a maximum value and a minimum value of n values obtained by tensile tests in 0°, 45° and 90° directions relative to the rolling direction is 0.03 or less. 
   
   
       3 . The aluminum alloy sheet for bottle cans superior in high-temperature properties according to  claim 1 , wherein an average particle size of 0.5 μm or larger dispersed particles in the aluminum alloy sheet is 5 μm or smaller, and ΔT indicative of a solid-liquid coexistence temperature range between liquid and solid phases of aluminum is 40° C. or less. 
   
   
       4 . The aluminum alloy sheet for bottle cans superior in high-temperature properties according to  claim 1 , further comprising 0.001-0.3% of Cr and/or 0.05-1.0% of Zr. 
   
   
       5 . The aluminum alloy sheet for bottle cans superior in high-temperature properties according to  claim 1 , further comprising 0.005-0.2% of Ti alone or in combination with 0.0001-0.05% of B. 
   
   
       6 . The aluminum alloy sheet for bottle cans superior in high-temperature properties according to  claim 1 , wherein the amount of solute Mn is 0.12-0.38%, which means the amount of solute M separated from a precipitate exceeding 0.2 μm in particle size by the extracted residue method using hot phenol. 
   
   
       7 . The aluminum alloy sheet for bottle cans superior in high-temperature properties according to  claim 1 , wherein when the aluminum alloy sheet is subjected to a heat treatment at 290° C. for 20 seconds, a change in hardness, ΔHv, of the aluminum alloy sheet before and after the heat treatment is 30 Hv or less, and 0.2% proof stress of the aluminum alloy sheet after the heat treatment is 215 MPa or more. 
   
   
       8 . The aluminum alloy sheet for bottle cans superior in high-temperature properties according to  claim 1 , which is a cold rolled aluminum alloy sheet obtained by subjecting a hot rolled aluminum alloy sheet to cold rolling up to a final sheet without intermediate annealing. 
   
   
       9 . The aluminum alloy sheet for bottle cans superior in high-temperature properties according to  claim 1 , wherein when the aluminum alloy sheet is subjected to a heat treatment at 290° C. for 20 seconds, a change in hardness, ΔHv, of the aluminum alloy sheet before and after the heat treatment is 30 Hv or less, and 0.2% proof stress of the aluminum alloy sheet after the heat treatment is 215 MPa or more. 
   
   
       10 . The aluminum alloy sheet for bottle cans superior in high-temperature properties according to  claim 1 , which is a cold rolled aluminum alloy sheet obtained by subjecting a hot rolled aluminum alloy sheet to cold rolling up to a final sheet without intermediate annealing. 
   
   
       11 . An aluminum alloy sheet for bottle cans superior in high-temperature properties, the aluminum alloy sheet comprising the following composition: Mn 0.7-1.5% (mass %, also in the following), Mg 0.8-1.7%, Fe 0.1-0.7%, Si 0.05-0.5%, Cu 0.1-0.6%, with the remainder being Al and inevitable impurities, and comprising a crystal structure elongated in a rolling direction and with an average aspect ratio of crystal grains of 3 or more as determined through an examination from above of a part located at the center in the through-thickness direction, wherein the difference between a maximum value and a minimum value of tensile strength in 0°, 45° and 90° directions relative to the rolling direction is 25 MPa or less, and a difference between a maximum value and a minimum value of n values obtained by tensile tests in 0°, 45° and 90° directions relative to the rolling direction is 0.03 or less. 
   
   
       12 . An aluminum alloy sheet for bottle cans superior in high-temperature properties, the aluminum alloy sheet comprising the following composition: Mn 0.7-1.5% (mass %, also in the following), Mg 0.8-1.7%, Fe 0.1-0.7%, Si 0.05-0.5%, Cu 0.1-0.6%, with the remainder being Al and inevitable impurities, and comprising a crystal structure elongated in a rolling direction and with an aspect ratio of crystal grains of 3 or more as determined through an examination from above of a part located at the center in the through-thickness direction, wherein an average particle size of 0.5 μm or larger dispersed particles in the aluminum alloy sheet is 5 μm or smaller, and ΔT indicative of a solid-liquid coexistence temperature range between liquid and solid phases of aluminum is 40° C. or less. 
   
   
       13 . The aluminum alloy sheet for bottle cans superior in high-temperature properties according to  claim 11 , further comprising 0.001-0.3% of Cr and/or 0.05-1.0% of Zn. 
   
   
       14 . The aluminum alloy sheet for bottle cans superior in high-temperature properties according to  claim 11 , further comprising 0.005-0.2% of Ti alone or in combination with 0.0001-0.05% of B.