| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug having a welded part where a noble metal chip and an electrode are welded uniformly. SOLUTION: A superposed assemble body 70 is constructed by superposing noble metal chips 31 on a chip fixing surface of a center electrode 3 made of a heat-resistant alloy containing Ni or Fe as a main component. The noble metal chip 31' is fixed to the chip fixing surface and turned into a noble metal ignition part 31 by forming a whole periphery laser welding part 10 extending over the noble metal chips 31' and a chip fixing surface forming part, along the outer periphery surface of the chip. In order to from the w hole periphery laser welding part 10, with maximum outer periphery length dmax of 2.0 mm or less, and not reaching to the discharge surface in the direction of the thickness of the noble metal chips 31' a laser light source 50 with energy per pulse of 2-6 J, a pulse length of 1-10 millisecond, and a pulse generation frequency of 2-20 pulses/second, is used as a light source of the laser welding.
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