ALUMINUM ALLOY SHEET FOR PRESS FORMING EXCELLENT IN HARDENABILITY BY HIGH-TEMPERATURE SHORT-TIME BAKING AND ITS PRODUCTION

摘要

PURPOSE: To obtain the Al alloy sheet by adding Si to Al-Mg-Cu and allowing streaks to appear in an electron beam diffraction grating image after baking treatment under specific conditions. ;CONSTITUTION: An ingot of an Al alloy having a composition which consists of, by weight, 1.5-3.5% Mg, 0.3-1.0% Cu, 0.05-0.6% Si, and the balance Al and in which Mg/Cu is regulated to 2-7 is subjected to homogenizing treatment at 400-580°C, hot-rolled, and cold-rolled to the desired sheet thickness. This sheet material is heated up to 500-580°C at a rate of ≥3°C/sec, held at this temp. for 0-60sec, and cooled down to 100°C at a rate of ≥2°C/sec. By this method, the Al alloy sheet where, in the electron beam diffraction grating image after baking treatment at 120-180°C baking temp. for 5-40min baking time, a streaky modulation structure is allowed to appear in the position of the diffraction grating point of an Al-Mg-Cu compound can be obtained. Because this alloy sheet is reduced in strength before forming and excellent in delayed aging characteristic at ordinary temp., changes with the lapse of time before press forming can be prevented.;COPYRIGHT: (C)1994,JPO&Japio