| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug for an internal combustion engine which can prevent a flashover due to abrasive particles which is generated as a result of wearing out of a terminal electrode through vibration generated by the combustion engine. SOLUTION: A terminal electrode (4) heat sealed with glass seal together with a center electrode (3) inside an axial opening of an insulator is subjected to the quench hardening treatment. For improvement of quenching efficiency in the case of a steel stock used for the terminal electrode (4), C, Cr, Mn and Mo is to be added. With this, the terminal electrode (4) comprising a spark plug (1) for internal combustion engine is quenched and hardened by glass seal, by dint of which, even if friction occurs between the terminal electrode (4) and a connection fitting (15) of a plug cap (11), the abrasion of the terminal electrode (4) can be restrained to a minimum, and a flashover at the insulator (2) can be prevented.
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