Patent ID: 8922103

Claim:
A spark plug comprising: a tubular metallic shell and a ground electrode resistance-welded at a proximal end portion to the metallic shell; the ground electrode being formed from a metal material in which precipitates containing at least one of an oxide, a carbide, a nitride, and an intermetallic compound are precipitated in grain boundaries; the spark plug being characterized in that when a portion of the ground electrode ranging within 100 μm from a weld boundary between the metallic shell and the ground electrode is defined as a heat-affected zone, and a distal end portion of the ground electrode is defined as a normal zone, an area occupied by the precipitates on a section of the heat-affected zone is equal to 65% or more an area occupied by the precipitates on a section of the normal zone, and as viewed on the section of the heat-affected zone, a diameter of an equivalent circle of a precipitate having a greatest area among the precipitates is 50 μm or less, and a shortest distance between the precipitates is 2 μm or greater.