| 摘要 |
PROBLEM TO BE SOLVED: To carry out a good spot welding by an alternating current plasma arc to an object to be welded such as an aluminum, an aluminum alloy, a magnesium alloy and the like for which an oxide film of a high melting point is formed on its surface. SOLUTION: This plasma arc welding method is provided with an electrode 2 and a plasma arc torch 1 composed of nozzles which surround the electrode 2 and form the flow routes to flow an inert gas between the electrodes 2. A plasma arc A is generated by applying an electric voltage between the electrode 2 and an object to be welded with the electrode 2 being minus and the object being plus. Also, a plasma arc B for cleaning purpose is generated by applying an electric voltage between the above mentioned nozzles and the object to be welded with the nozzles being plus and the object being minus. The welding is thus carried out while cleaning the object being welded 6. In this case, a periphery of a welding point of the object being welded 6 mechanically covered and electrically insulated so that the plasma arc A for cleaning purpose is focused at substantially the same welding point as that of the plasma arc B for welding. |
