| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug comprising an ignition part having a first main component of Pt and a second component of Ni, which hardly causes trouble such as cracking, peeling or dropping-out of the ignition part. SOLUTION: In this spark plug, an ignition part 31 is provided at a tip of a central electrode 3, an ignition part 32 opposed to the ignition part 31 is provided at a tip of a grounding electrode 4, and the gap between both the ignition part 31 and 32 corresponds to a spark discharge gap 33. Each of the ignition parts 31 and 32 comprises Pt as the main first component and Ni as the second component. The chip-like ignition parts 31 and 32 have an average value of crystal grain orientation ratio of 0.5 or less and a Vickers hardness of 350 Hv or less by performing a predetermined heat treatment thereto after plastic working. Consequently, enlargement of grain size of the crystal grains is suppressed, whereby deterioration of the mechanical strength is suppressed, and internal cracking resulted from working distortion can be consequently solved. COPYRIGHT: (C)2007,JPO&INPIT
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