| 摘要 |
A spark plug (1) includes a metallic shell (3) and a ground electrode (27) resistance-welded to the metallic shell (3). The ground electrode (27) is formed from a metal material in which precipitates PR containing at least one of an oxide, an intermetallic compound, etc., are precipitated in grain boundaries. The diameter of an equivalent circle of a precipitate PR having the greatest area is 50 μm or less, and the shortest distance between the precipitates PR is 2 μm or greater. The area occupied by the precipitates PR on the section of the heat-affected zone 27A is equal to 65% or more the area occupied by the precipitates PR (the diameter of an equivalent circle of a precipitate PR having the greatest area) on a section of the normal zone 27B.
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