| 摘要 |
Spheroidal graphite cast iron containing 0.016-0.030 weight % of S, in which the number of spheroidal graphite particles having a diameter of 2 mu m or more is such that it is 1700/mm2 or more when an as-cast iron portion measured has a thickness of 3 mm. This cast iron is produced by: (a) preparing an Fe alloy melt consisting essentially of, by weight, 3.0-4.0% of C, 1.8-5.0% of Si, 1.0% or less of Mn, 0.20% or less of P, 0.005-0.015% of S and balance Fe and inevitable impurities; (b) adding 0.020-0.050% of a lanthanide rare earth metal to the Fe alloy melt before or simultaneously with adding a spheroidizing agent; (c) subjecting the melt to a spheroidizing treatment by using the spheroidizing agent; and (d) adding a sulfur-containing material to the melt so that the amount of S is adjusted to 0.016-0.030 weight %, and that the amount of the lanthanide rare earth metal is adjusted to 0.010-0.040 weight %.
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