| 摘要 |
In a spark plug for an internal combustion engine, a noble metal chip such as an iridium alloy chip is bonded on the tip of a center electrode made of a material such as nickel by laser beam welding. The noble metal chip contains another noble metal such as rhodium having a melting point lower than that of the noble metal chip. By laser welding, a molten bond containing the noble metal melted thereinto from the noble metal chip is formed at the junction of the noble metal chip and the center electrode. Alternatively, the noble metal to be melted into the molten bond may be supplied by a separate noble metal plate. The molten bond thus made has a high bonding strength and a small thermal stress, and thereby durability of the spark plug is improved.
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