| 摘要 |
PURPOSE:To form a blackened film having sufficient film thickness by heating steel plate parts in a blackening atmosphere consisting of a single or mixed gas of nitrogen gas, fuel gas or steam while adding a specific amount of air into a blackening atmosphere. CONSTITUTION:Steel plate parts are heated in a blackening atmosphere consisting of a single or mixed gas of nitrogen gas, fuel gas or steam at 470-600 deg.C for 5-30min, while 0.5-5.0% of air is added to a blackening atmosphere. Thereby, thickness of a blackened film can be increased without changing construction of a blackening treatment furnace, treatment time and the gas atmosphere. Accordingly, even when blackening treatment is performed in a relatively low temperature range, not to speak or rusting on the way of a manufacturing process of a color cathode-ray tube, trouble due to reduce radiation effect can dissolved, diffusion of an electron beam can be reduced while a blackened film having equal adhesiveness to the former one can be obtained. |
