Abstract: Disclosed is a shadow mask plate material which consists of an Fe-Ni-based alloy containing iron and nickel as main constituents, has an unrecrystallized texture with a grain size of 10 .mu.m or less, and is excellent in etching characteristics for forming electron beam apertures.

Abstract: A method of regenerating an etching waste fluid, includes the steps of dissolving HCl gas in an etching waste fluid at a temperature falling within a range of 20.degree. C. to 50.degree. C. and crystallizing NiCl.sub.2 and FeCl.sub.2 crystals, the etching waste fluid containing NiCl.sub.2, FeCl.sub.3, and FeCl.sub.2 and being obtained by etching Ni or an Ni alloy with an etching solution consisting of an aqueous solution containing FeCl.sub.3, distilling a mother liquor at the atmospheric pressure after crystallization and separation thereof to reduce the HCl concentration in the mother liquor, and distilling, at a reduced pressure, a concentrate obtained upon distillation at the atmospheric pressure to further reduce the HCl concentration, thereby obtaining an aqueous solution containing FeCl.sub.

Abstract: A color picture tube comprises a shadow mask which is formed to, oppose at a small gap therefrom, a phosphor screen formed on the inner surface of a panel. The shadow mask comprises a sheet of a nickel-containing iron alloy which contains 0.1% by weight or less of manganese and having an austenite grain number of 7 or less both within and at surfaces of the sheet, the austenite grain number being defined by JIS G 0551 of the Japanese Industrial Standards. The iron alloy sheet is annealed in a vacuum of 10.sup.-1 Torr or less at a temperature of 1,000.degree. C. or higher prior to formation into the shadow mask.

Abstract: A shadow mask for a color picture tube, which has a plurality of regularly aligned apertures, an oxide film having good adhesion and anticorrosion characteristics which is made of a metal alloy consisting of as the major constituents, iron and nickel, wherein an iron content of at least a surface layer of a portion of the shadow mask which has the apertures is higher than that of the substrate of the metal alloy.