METHOD OF DRAPE DRAWING A SHADOW MASK FOR A COLOUR DISPLAY TUBE AND DEVICE FOR SUCH A METHOD

摘要

A shadow mask sheet for a colour display tube consisting of a nickel-iron alloy is drape drawn by means of a drawing process. Prior to the drawing process the shadow mask sheet is subjected to an annealing treatment between 700 and 820.degree.C so as to produce complete recrystallisation without grain growth of any significance. During the drawing process the shadow mask sheet is maintained at a temperature between 150.degree.C and 250.degree.C, a 0.2 % proof stress of the shadow mask material between 150 and 250.degree.C being reached below a tensile stress of 150 N/mm2.