Patent ID: 7081172

Claim:
A nodular graphite cast iron consisting essentially of: from 3.0 to 4.6 weight % of carbon; from 1.6 to 2.5 weight % of silicon; from 0.2 to 0.6 weight % of manganese; from 0.02 to 0.05 weight % of magnesium; from 0.0004 to 0.090 weight % of zirconium; at least 0.010 weight % of tin; copper; and a balance of iron and inevitable impurities, wherein the sum of a weight % of the tin and 0.1 times a weight % of the copper ranges from 0.01 to 0.06 weight %; and the nodular graphite cast iron is produced by a process comprising heating a melt containing carbon, silicon, manganese, magnesium, zirconium, tin, copper and iron; and adding to the melt a treating material comprising a Zr—Si—Fe alloy, a Si alloy covering the Zr—Si—Fe alloy, and a Fe—Si alloy covering the Si alloy.