| 摘要 |
PURPOSE: A bolt for an airtight welding is provided to prevent the gap generation caused by non-welding portion and enhance an arc generating rate by decreasing an initial contact area of a bolt head unit and the inner circumference of a tank. CONSTITUTION: A bolt for an airtight welding is composed of a bolt head unit(1) and a screw unit(2), thereby being fixed in a bolt installation hole(T1) of a tank. The inner circumference of the tank and the bolt head unit face-contact while the screw unit is accommodated in the bolt installation hole. A ring shaped protrusion(10) is formed around the screw unit in one side of the bolt head unit. A cross sectional shape of the ring shaped protrusion is a domed shape or a triangle shape.
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