CARTRIDGE SHUTTER AND MATERIAL FOR ITS PRODUCTION

摘要

A shutter for a cartridge for containing a recording medium that has excellent scratch resistance and dustproofness. The shutter is composed of a nonmagnetic corrosion resistant steel sheet containing at least about 10% by weight of Cr, and includes a front surface having a hardness (Hv) of not less than about 250 but not more than 400 and a roughness expressed as an average surface roughness (Ra) of not less than about 0.3 mu m but not more than 1.0 mu m, and a reverse surface having a roughness (Ra) adjusted to about 0.1 to 0.25 mu m if the reverse surface is finished as a dull surface, and adjusted to about 0.15 to 0.50 mu m if the reverse surface is finished by a grinding roll. The steel sheet has first and second surfaces which are to respectively constitute the outer and inner surfaces of the shutter, and which have surface roughness values corresponding to the above surface roughness values of the front and reverse surfaces of the steel sheet. In addition, the steel sheet has a hardness (Hv) of about 220 to 350 in the central portion of the thickness dimension thereof, and a hardness (Hv) of not less than about 250 but not more than 400 in the surface layer portion on the outer surface of the shutter.