| 摘要 |
PROBLEM TO BE SOLVED: To improve heat resistance and oxidation resistance of the earth electrode and secure welding strength of the main fittings and the earth electrode. SOLUTION: By using a Ni group alloy containing 10 wt.% or more of Cr and 1.5 wt.% or more of Al as a material of the earth electrode 4, the oxides of Cr and Al precipitate on the surface of the earth electrode and a storing oxidation film is formed, and by this oxidation film the progress of oxidation into the earth electrode is suppressed, thereby, wearing by spark of the earth electrode is suppressed. When the above Ni group alloy is used, in case welding of the earth electrode 4 and the main fitting is carried out in the atmosphere, oxidation film is formed at the welding interface during welding, thereby, the welding strength is decreased than before. Therefore, by welding in the substantially non-oxygen atmosphere, formation of oxidation film in the welding interface during welding can be prevented, and the welding strength is secured.
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