| 摘要 |
PURPOSE:To remove strained part of a metallic plate and to prevent melting loss by sprinkling conductive fine powder that lowers dielectric breakdown voltage on the surface of a metallic plate, and thereby dispersing poles of the arc. CONSTITUTION:Conductive fine powder (Al, Fe, Cu etc.) 8 that lowers dielectric breakdown voltage is sprinkled beforehand on the surface of a metallic plate W. DC voltage is impressed between an electrode bar 5 and the metallic plate W and a water-cooled copper ring 2. In initial stage of arc starting, a branch arc is generated between the electrode bar 5 and water-cooled copper ring 2, and then a stable main arc A is generated between the electrode bar 5 and metallic plate W. On the other hand, inert gas is supplied to an inside hole 1a of a torch body 1 and discharged from a groove 3a at the lower end of an insulating ring 3. In initial stage of generation of main arc A, poles of the main arc are generated dispersedly on the fine powder 8 in the insulating ring 3 and a insulating thin film 9 is broken in a moment and poles of the main arc are enlarged. By this way, the strained part of the metallic plate W can be removed. |
