| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug of a structure in which chips, consisting of Ir alloy containing no less than 50 wt.% Ir through relieve layers, are resistance welded to a center electrode and/or grounding electrode and exfoliation of the chips from the relieve layers is suppressed by enhancing the joining performance of the chips. SOLUTION: A spark plug is configured so that the forefront 3a of a center electrode 3 held insulatedly on a fitting metal 1 and the confronting part 4a of a grounding electrode 4 fixed to the fitting metal are opposed with a discharge gap 6 interposed in between. The parts 3a and 4a are made at least either of Ni-based alloy and Fe-based alloy, and to their confronting parts, chips 51 and 52 consisting of Ir alloy containing no less than 50 wt.% Ir are jointed by means of resistance welding via relief layers 61 and 62, and the joining interfaces between the chips 51 and 52 and relief layers 61 and 62 are formed into curved surfaces.
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