Method of manufacturing aluminum plate

A method of manufacturing an aluminum alloy plate for a battery case, the method comprising:

• a melting and alloying step of melting and alloying a composition for manufacture of the aluminum alloy plate;
• a cleaning step of removing foreign matter from a resultant melt, for management of a cleaning degree of the melt;
• a billet casting step of manufacturing a billet having a predetermined width, a predetermined thickness and a predetermined length from the composition;
• a scalping step of removing oxides, foreign matter and an inverse segregation layer from a surface of the billet;
• an extrusion step of extruding the billet at a temperature in a range of 500° C. to 600° C., under a pressure of 200 bar or more, and at a speed in a range of 1.0 to 5.0 mm/s for producing the aluminum alloy plate having a thickness in a range of 9 to 15 mm;
• a coiling step of coiling the aluminum alloy plate having the thickness in the range of 9 to 15 mm using a coiling device while applying tension to the aluminum alloy plate, wherein the coiling step directly follows the extrusion step;
• a cold-rolling step of rolling the aluminum alloy plate having the thickness in the range of 9 to 15 mm so that the rolled aluminum alloy plate has a thickness in a range of 20 to 30% of the thickness of the aluminum alloy plate having the thickness in the range of 9 to 15 mm;
• an annealing step of annealing the rolled aluminum alloy plate following the cold-rolling step for stress removal and texture recrystallization, wherein the annealing step is performed in a range of 300 to 400° C. for 1 to 5 hours;
• a stabilization step of increasing strength and recovering physical properties causing degradation in elongation of the aluminum alloy plate in the cold rolling step, wherein the stabilization step is performed in a range of 130 to 180° C. for 1 to 5 hours;
• a tension leveling step of subjecting the rolled aluminum alloy plate to tension leveling, to secure a desired flatness of the aluminum alloy plate;
• and
• a cutting step of cutting the aluminum alloy plate after the tension leveling, for manufacture of the battery case using the cut aluminum alloy plate.