| 摘要 |
A process for producing a center electrode for a spark plug comprises the following steps: providing a cylindrical electrode body of a less noble metal which is predominantly made of a nickel alloy or a composite thereof with a copper core, the electrode body having a concentric, smaller-diameter projection from the tip of the body; placing on the tip of the electrode body a disk which has a center hole into which the projection fits and which is made of a noble metal such as platinum or an alloy thereof; electrically welding the noble metal disk to the tip of the electrode body; and drawing and extruding the assembly to reduce its outside diameter so that the layer of the noble metal or alloy thereof covers at least the side wall of the part close to the tip of the electrode body.
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