| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method of a spark plug in which generation of spatter can be reduced, and shortage of welding due to insufficient melting depth at the welding part and development of oxidized scale due to long time use are eliminated, and a spark plug which has durability at the ignition part that has not been realized by the conventional method. SOLUTION: The tip fixing face forming part of the center electrode 3 is constructed of a heat resistant alloy made mainly of Fe or Ni, and a whole circle laser welding part 19 that ranges from the precious metal tip 31' to the tip fixing face forming part position is formed for the overlapped assembly body 70 overlapping the tip fixing face 3s and the precious metal tip 31'. In this case, when the laser beam LB that is emitted from the laser generating part 40 is irradiated on the overlapped assembly 70 by being focused by the irradiation optical part 50, the beam transmission line 60 from the laser generating part 40 to the irradiation optical part 50 is constructed of graded index shape optical fiber cable 61.
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