Patent ID: 7825571

Claim:
A spark plug comprising: a cylindrical metal shell; a cylindrical insulator provided in an inner hole of said metal shell; a center electrode provided in a leading end side inner hole of said insulator; and a ground electrode having one end bonded to a leading end side of said metal shell and having another end face forming a spark discharge gap with said center electrode, wherein said ground electrode comprises an electrode material containing from 0.5 to 1.5 wt. % of Si; from 0.5 to 1.5 wt. % of Al, from 0.02 to 1.0 wt. % of at least one of Ti, V, Zr, Nb and Hf, from 0.03 to 0.09 wt. % of C and 95.5 wt. % or more of Ni, and having a specific resistance at 20° C. of 25 μΩcm or less, wherein said electrode material has an initial average crystal grain diameter of 35 μm or less and has an average crystal grain diameter of 300 μm or less after being held at 900° C. for 100 hours, and wherein said electrode material contains 0.5 wt. % or less of Cr and Mn in total.