Abstract: A spark plug includes a metallic shell. The metallic shell includes a tubular metallic shell body, a zinc plating layer provided on a surface of the metallic shell body and containing zinc as a main component, a chromium layer provided to cover the zinc plating layer and containing chromium as a main component, and a silicon layer provided to cover the chromium layer and containing silicon as a main component.

Abstract: A metallic shell for a spark plug which metallic shell achieves suppressed elution of hexavalent chromium, and a spark plug including the metallic shell. The spark plug has a metallic shell. The metallic shell includes a tubular metallic shell body; a metal plating layer provided on a surface of the metallic shell body; and a chromium-containing chemical conversion coating layer provided to cover the metal plating layer. The chemical conversion coating layer has a zirconium component content of 0.1 mass % or more.

Abstract: A metallic shell for a spark plug which metallic shell achieves suppressed elution of hexavalent chromium, and a spark plug including the metallic shell. The spark plug has a metallic shell. The metallic shell includes a tubular metallic shell body; a metal plating layer provided on a surface of the metallic shell body; and a chromium-containing chemical conversion coating layer provided to cover the metal plating layer. The chemical conversion coating layer has a zirconium component content of 0.1 mass % or more.

Abstract: An ignition plug includes a metallic shell containing iron as a main component, carbon in an amount of 0.20 wt. % to 0.30 wt. %, manganese in an amount of 0.30 wt. % to 0.45 wt. %, and sulfur in an amount of 0.005 wt. % to 0.009 wt. %. The ratio of the manganese content (wt. %) to the sulfur content (wt. %); i.e., Mn/S is 40 to 65.

Abstract: An ignition plug includes a metallic shell containing iron as a main component, carbon in an amount of 0.20 wt. % to 0.30 wt. %, manganese in an amount of 0.30 wt. % to 0.45 wt. %, and sulfur in an amount of 0.005 wt. % to 0.009 wt. %. The ratio of the manganese content (wt. %) to the sulfur content (wt. %); i.e., Mn/S is 40 to 65.

Abstract: A spark plug includes an insulator having an axial hole formed therethrough in the direction of an axis of the spark plug, a center electrode disposed in a front side of the axial hole and a metal shell disposed around an outer circumference of the insulator and having a collar-shaped tool engagement portion and a crimp portion located on a rear side of the tool engagement portion and reduced in diameter toward the rear, wherein the crimp portion of the metal shell is made of a carbon steel material having a grain size number equal to or greater than No. 11 as measured according to JIS G 0551.

Abstract: A spark plug includes an insulator having an axial hole formed therethrough in the direction of an axis of the spark plug, a center electrode disposed in a front side of the axial hole and a metal shell disposed around an outer circumference of the insulator and having a collar-shaped tool engagement portion and a crimp portion located on a rear side of the tool engagement portion and reduced in diameter toward the rear, wherein the crimp portion of the metal shell is made of a carbon steel material having a grain size number equal to or greater than No. 11 as measured according to JIS G 0551.