| 摘要 |
PROBLEM TO BE SOLVED: To develop a mask material for a flat tube which has a small amount of thermal drift when assembled into a cathode-ray tube. SOLUTION: The Fe-Ni-Co based alloy for a press forming type flat mask having excellent low thermal expansibility after blackening treatment has a composition containing 4.0 to 6.0% Co, 36.0 to 38.0% Ni+Co and 0.01 to 0.40% Mn, and further containing 0.20 to 0.40% Nb, and the balance Fe with inevitable impurities. Its thermal expansion coefficient after blackening treatment can be reduced while maintaining its high strength by the control of the ratios of Ni, Co and Mn, the selection of Nb as a strength increasing element, and the precise control of the amount of the Nb to be added.
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