| 摘要 |
<p>This invention provides a spark plug comprising a ground electrode with a firing part, to which a noble metal chip is joined, having high durability, and a process for producing the spark plug. The spark plug comprises a center electrode, an insulator, a main metal fitting, and a ground electrode. The ground electrode comprises an electrode base material one end of which is joined to the end of the main metal fitting. A noble metal chip is joined to the other end of the main metal fitting. Due to work hardening, the noble metal chip has an average hardness of not less than (Hv) 200 and not more than (Hv) 650. The electrode base material is formed of an Ni alloy comprising not less than 15% by mass and not more than 30% by mass of Cr and not less than 1.5% by mass and not more than 4% by mass of Al. In the weld between the noble metal chip and the electrode base material, the total mass of Ni, Cr, Al, Si, and Fe is not less than 45% by mass and not more than 95% by mass of the total mass of the weld. The average hardness of each of the noble metal chip, the weld, and the electrode base material increases in this order. The average hardness of the weld is not less than (Hv) 140 and not more than (Hv) 245.</p> |
