SPARK PLUG

摘要

An ignition part (80) in a ground electrode (30) has a melt part (85) in a base part(82). The melt part (85) is formed as a result of dissolution and mixing of a material constituting a noble metal member (81) and a material constituting the base part in each other upon laser welding the noble metal member (81) to the base part (82). In the melt part (85), the average ratio P of components derived from the noble metal member (81) at points K1, L1 and M1 is not less than 80%, the average ratio Q of the components derived from the base part at points K3, L3 and M3 is not less than 20%, and P + Q is not more than 160%. According to the above constitution, in the ignition part (80), joint strength depending on the site can be obtained, and the occurrence of cracks, separation and the like caused by thermal stress can be satisfactorily suppressed.