Method for producing spheroidal graphite cast iron and vehicle component using said spheroidal graphite cast iron

A method for producing spheroidal graphite cast iron containing substantially no rare-earth element, the method comprising:

• (a) a step of subjecting, in a ladle, a molten iron to a spheroidization treatment using a spheroidizing agent of an Fe—Si—Mg-based alloy containing no rare-earth element or Fe—Si—Mg—Ca-based alloy containing no rare-earth element;
• (b) a step of conducting an inoculation treatment using a first Fe—Si-based inoculant, either simultaneously with the step (a) or after the step (a);
• and
• (c) a step of adding a second Fe—Si-based inoculant to the molten iron in an amount of 0.20 to 0.40% in terms of % by mass after the step (b) to conduct a pouring inoculation treatment, the second Fe—Si-based inoculant containing, in terms of % by mass, 45 to 75% of Si, 1 to 3% of Ca, and 15 ppm or less of Ba,
• wherein the spheroidal graphite cast iron to be obtained has a composition which contains, in terms of % by mass, 3.0 to 4.5% of C, 3.0 to 4.5% of Si, 0.2 to 0.4% of Mn, 0.006 to 0.020% of S, 0.08 to 0.30% of Cu, 0.020 to 0.040% of Sn, and 0.015 to 0.050% of Mg, with the remainder being Fe and unavoidable impurities.