ALUMINUM ALLOY SHEET FOR AUTOMOBILE BODY SHEET AND ITS PRODUCTION AND METHOD FOR FORMING THE SAME

摘要

PURPOSE: To obtain an Al alloy sheet for automobile body sheet, excellent in formability under low viscosity lubrication, by specifying a composition consisting of Mg, Fe, Mn, Cr, Zr, and Al and regulating crystalline grain size and surface roughness to specific values, respectively. ;CONSTITUTION: An Al alloy sheet, which consists of, by weight, 2.0-8.0% Mg, one or more kinds among ≤1.5% Fe, ≤1.0% Mn, ≤0.3% Cr, and ≤0.3% Zr, and the balance Al with ordinary impurities and has 50-150μm final crystalline grain size and in which surface roughness is regulated so that it satisfies Ra≤0.5μm and also Ra≥0.87μm in the case of 5% stretch addition, is obtained. Further, this Al alloy sheet can be suitably used for forming by using low viscosity oil of ≤20cSt viscosity of lubricating oil. At the time of producing this alloy sheet, an Al alloy ingot of the above composition is hot-rolled and cold-rolled. At this time, final cold rolling is done at ≤30% rolling rate and ≤0.5μm roll roughness Ra. Then, the resulting cold rolled sheet is subjected to final annealing at ≥3.0°C/sec temp. rise rate at a holding temp. between 450 and 550°C or between 520 and (melting point -10)°C for ≤120sec holding time.;COPYRIGHT: (C)1995,JPO