| 摘要 |
PROBLEM TO BE SOLVED: To prevent the fatigue failure of a weld section by combining a mask main body and a mask frame, and welding them with a damped wave-form current gradually damped with a current after a nearly fixed current practically required for welding is fed for a fixed time to assemble a shadow mask. SOLUTION: The portion of a flat plate-like raw material made of a cold rolled steel sheet where many electron beam passing holes are bored by photo- etching is stretched into a prescribed curved face, a skirt section is formed by drawing, and a black oxide film is formed on the surface by blackening to form a mask main body. When a mask frame and a skirt section molded and blackened separately are welded at multiple weld points, a black oxide film is broken via the feed of a fixed front-stage current. After a fixed time elapses, a nearly fixed current required for welding is fed for a fixed time, then a rear-stage damped wave-form current is fed. A quick temperature drop at a weld section and near it is suppressed to mitigate hardening unlike the instantaneous cutoff of a current, and a shadow mask is not released by a shock or deformation stress.
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