| 摘要 |
PURPOSE:To enable the use for a long period of a nonconsumable electrode without its readjustment by changing over a center gas from the previously flowed bigger flow to the ordinary one in case of igniting a main plasma arc. CONSTITUTION:A pilot arc is ignited by the DC power source 11 for pilot arc in a nonconsumable electrode 1 and constraining a nozzle electrode 2. The plasma welding is then performed without forming a key hole on the body 12 to be welded by igniting the main plasma arc via the plasma flow between the nonconsumable electrode 1 and the body 12 to be welded by the DC power source 10 for welding. In case of this main plasma arc ignition, the center gas fed from the flow path 13 is changed from the bigger flow passed in advance to the ordinary one. The ignition of the main plasma arc is thus made easy by projecting the pilot arc from the tip of the constraining nozzle electrode 2. to the external part.
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