SPHEROIDAL GRAPHITE CAST IRON MEMBER AND PROCESS FOR PRODUCING THE SAME

PROBLEM TO BE SOLVED: To provide spheroidal graphite cast iron in which a spheroidizing agent not containing rare-earth elements is used, and chilling at the thin thickness part can be restrained, and which has no internal defects.SOLUTION: In a ladle, the spheroidizing treatment is performed by controlling the charging amount of the spheroidizing agent of an Fe-S-Mg-Ca based alloy which contains, by mass ratio, 3.0-6.0% Mg, 1.0-2.0% Ca, 0.5-3.5% Ba and ≤0.3% Al and which does not contain the rare-earth elements to 0.8-2.0%, by mass ratio, to molten iron, and also, an inoculation treatment is performed using an Fe-Si based inoculating agent, and thereafter, a melt-stream inoculation treatment is performed using an Fe-Si-Ca based inoculating agent to obtain the spheroidal graphite cast iron member composed of, by mass ratio, 3.0-4.5% C, 3.0-4.0% Si, 0.2-0.4% Mn, 0.006-0.020% S, 0.08-0.30% Cu, 0.020-0.040% Sn, 0.015-0.050% Mg, ≤0.03% Al, ≤0.01% Zn and the balance Fe with inevitable impurities, as the finish composition.