Cold-Rolled Aluminum Alloy Sheet for Bottle Can with Excellent Neck Part Formability and Process for Producing the Cold-Rolled Aluminum Alloy Sheet

Abstract

A cold-rolled aluminum alloy sheet has a composition containing 0.7 to 1.5% by mass Mn, 0.8 to 1.7% by mass Mg, 0.1 to 0.7% by mass Fe, 0.05 to 0.5% by mass Si, 0.1 to 0.6% by mass Cu, and Al and inevitable impurities as other elements. In the structure of the cold-rolled aluminum alloy sheet, 50 to 400 particles of particle sizes in the range of 0.05 to 1 μm are dispersed in an area of 300 μm 2 when observed under a TEM at a magnification in the range of 5,000× to 15,000× magnification, and the ratio of the number of the dispersed particles of sizes of 0.3 μm or above to the number of all the dispersed particles is in the range of 15 to 70%.

1 : A cold-rolled aluminum alloy sheet comprising: 0.7 to 1.5% by mass Mn, 0.8 to 1.7% by mass Mg, 0.1 to 0.7% by mass Fe, 0.05 to 0.5% by mass Si, 0.1 to 0.6% by mass Cu, and Al and inevitable impurities as other elements;
 wherein 50 to 400 particles of particle sizes in the range of 0.05 to 1 μm are dispersed in an area of 300 μm 2  when observed under a TEM at a magnification in the range of 5,000× to 15,000× magnification, and the ratio of the number of the dispersed particles of sizes of 0.3 μm or above to the number of all the dispersed particles is in the range of 15 to 70%.   
   
   
       2 : The cold-rolled aluminum alloy sheet according to  claim 1 , wherein the mean aspect ratio of crystal grains in the structure of the cold-rolled aluminum alloy sheet as viewed from above with respect to the thickness of the cold-rolled aluminum alloy sheet in a middle part of the cold-rolled aluminum alloy sheet is 3 or above. 
   
   
       3 : The cold-rolled aluminum alloy sheet according to  claim 1 , wherein the composition further comprises either of or both Cr in a Cr content in the range of 0.001 to 0.3% by mass and Zn in a Zn content in the range of 0.05 to 1.0% by mass. 
   
   
       4 : The cold-rolled aluminum alloy sheet according to  claim 1 , wherein the composition further comprises 0.005 to 0.2% by mass Ti or both 0.005 to 0.2% by mass Ti and 0.0001 to 0.05% by mass B. 
   
   
       5 : A method of manufacturing a cold-rolled aluminum alloy sheet, according to  claim 1 , comprising:
 soaking an ingot at 550° C. or above;   slowly cooling the ingot at a cooling rate of 25° C./hr or below to a temperature in the range of 450° C. to 550° C.; and   hot rolling and cold rolling the ingot such that 50 to 400 particles of particle sizes in the range of 0.05 to 1 μm are dispersed in an area of 300 μm 2  when observed under a TEM at a magnification in the range of 5,000× to 15,000× magnification, and the ratio of the number of the dispersed particles of sizes of 0.3 μm or above to the number of all the dispersed particles is in the range of 15 to 70%.   
   
   
       6 : The method according to  claim 5 , wherein the cold rolling cold-rolls a hot-rolled sheet into a cold-rolled sheet of a final thickness without annealing the hot-rolled sheet during the cold rolling.