ALUMINUM ALLOY MATERIAL HAVING DARK GRAY COLOR TONE AFTER ANODIC OXIDATION TREATMENT AND ITS PRODUCTION

摘要

PURPOSE:To properly control metallic Si precipitates and to obtain a dark gray color tone hardly tinged with yellow after anodic oxidation treatment by subjecting an ingot of an Al alloy having a composition containing a crystalline grain refining agent, such as Ti, to heating and rolling under specific conditions. CONSTITUTION:An alloy having a composition consisting of, by weight, 0.5-3.0% Si, 0.3% Fe, 0.003-0.15% Ti, as a crystalline grain refining agent, independently or in combination with 1-100ppm B, and the balance Al with inevitable impurities is cast by a DC casting method. The resulting ingot is heated at 350-500 deg.C for 0.5-24hr and hot-rolled at a temp. equal to or lower than the heating temp. and ranging from 350 to 430 deg.C, or further, the resulting plate is cold-rolled while batch-annealed at 260-400 deg.C for 0.5-24hr or continuously annealed at 380-520 deg.C between the cold rolling stages. By this method, a rolled sheet in which metallic Si precipitate with a size of 0.1-3mum comprises =80%, by area ratio, of all the metallic Si precipitates can be obtained. By using this Al alloy material, a dark gray color tone free from a tinge of yellow can be obtained with certainty by means of anodic oxidation treatment.