Patent ID: 8691031
Filing Date: 2014-04-08
Classification: C22C,C22F

Abstract:
1. A method for manufacturing an aluminum alloy sheet, comprising the steps of preparing a slab having a thickness of 5 to 15 mm with a continuous casting machine by a continuous casting process using molten alloy containing following components: 0.40% to 0.65% of Mg, 0.50% to 0.75% of Si, 0.05% to 0.20% of Cr, and 0.10% to 0.40% of Fe, a remainder being Al, said components being essential elements; winding the slab into a coil; cold-rolling the slab into a sheet; subjecting the sheet to solution heat treatment in such a manner that the sheet is heated to a temperature of 530° C. to 560° C. at a heating rate of 10° C./sec or more and then maintained at the temperature for five seconds or more; quenching the sheet with water; coiling up the sheet; maintaining the sheet at a temperature of 60° C. to 110° C. for a time of three to 12 hours; and then cooling the sheet to room temperature, wherein the cold-rolling step is performed with a reduction ratio of 20% or more per pass in order to obtain an aluminum alloy sheet having an average grain size of 10 to 20 μm, and having a yield strength of 102 MPa or less.