Method for producing electrodes for spark plugs and spark plug electrodes

A method of producing a long-life spark plug electrode (16,18) by applying a movable punch (49) against a composite blank (77) in a hollow extrusion die (41),

• said composite blank containing
• a first, shell component (31,71) of corrosion-resistant material,
• a second component (32,72) of erosion-resistant material, and
• a third component (75) of highly erosion-resistant material, and
• a fourth, core component (33,73) of thermally conductive material,
• thereby impact-extruding said composite blank (77) to form an elongated electrode blank (79), comprising the steps of
• a) forming a blind bore or recess (34,62,74) in said shell component (31,71) and aligning said bore with an open end thereof facing upward;
• b) dimensioning said second and third components to occupy a volume equal to that of said bore in said shell component, heating said third component (75) until it melts and covers a lowest point (76) in said bore, and heating said second component (32,72) until it melts and fills a remaining portion of the volume of said bore (74);
• c) welding or soldering said fourth, core component (33,73) onto said first, second, and third components at a position covering said blind bore and components therein;
• d) inserting the thus-formed composite blank (77) into an accomodating cavity (43) of said extrusion die (41) with said fourth, core component (33,73) closest to said punch (49);
• e) applying said punch (49) axially against said composite blank (77), thereby producing said electrode blank (79) by impact-extrusion;
• and
• f) cutting, to a desired length, the impact-extruded elongated electrode blank (79) in such a way that highly erosion-resistant material of said third component (75) is exposed, thereby defining a highly erosion-resistant surface region (82) at an end face (17) of said spark plug electrode.