| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug which has durability against separation of the boundary face between a noble metal abrasion resistant part and a relaxation metal part, under in environment where the lead corrosion and oxidation corrosion tends to progress. SOLUTION: In a spark plug 100, a relaxation metal part 33 is connected as at least a part of a side peripheral face 33s is embedded in an electrode base metal 4m, and the noble metal abrasion resistant part 32 is connected as at least a part of a side peripheral face 32s is embedded in the relaxation metal part 33. The noble metal abrasion resistant part 32 is made of a metal, including either one or both of Ir and Rh by at least 80 mass % in total with the mass % of the included Ir being 97 or less, and including one or at least two selected among Pt, Rh and Ru by at least 3 mass %. The precious metal abrasion resistant part 32 is connected to the electrode base metal 4m via the relaxation metal part 33, made of a metal having an intermediate linear expansion coefficient between that of the electrode mother material 4m and that of the precious metal abrasion resisting part 32. The relaxation metal part 33 is constituted of a metal having at least either Ir or Rh and Ni as essential elements, the total mass % of Ir and Rh being at least 40 and the total mass % of Rh and Ni being at least 20.
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