Aluminum Alloy Material for Shutter of Recording Medium Cassette, Process for Producing the Same, and Aluminum Alloy Shutter Made of the Same

摘要

The invention is an aluminum alloy material for the shutter of flat recording medium cassettes. The shutter is light in weight and excellent in sliding, has good corrosion resistance and durability, and protects itself against staining with fingerprints. The aluminum alloy contains 3.0 - 6.0 percent Mg (by weight) and one or more than one optional elements of Mn <= l.5 percent, Cr <= 0.3 percent, Cu <= 0.5 percent, and Ti <= 0.1 percent, with the balance being aluminum and inevitable impurities, and has a tensile strength of 310-410Mpa, a yield strength of 250-370Mpa and surface roughness Ra of 0.2-1.5 mum. The aluminum alloy material is formed from a rolled sheet of said aluminum alloy by coating the sheet with a urethane film not thicker than 5 mum. The rolled sheet undergoes intermediate annealing, final cold rolling of 40-90 percent, and without stabilizing heat treatment.