Abstract: Heat-resistant, austenitic cast steel comprising by mass 0.3-0.6% of C, 1.1-2% of Si, 1.5% or less of Mn, 17.5-22.5% of Cr, 8-13% of Ni, 1.5-4% as (W+2Mo) of at least one of W and Mo, 1-4% of Nb, 0.01-0.3% of N, 0.01-0.5% of S, the balance being Fe and inevitable impurities, and meeting the following formulae (1), (2), (3) and (4): 0.05?(C—Nb/8)?0.6 ??(1), 17.5?17.5Si—(W+2Mo) ??(2), 5.6Si+(W+2Mo)?13.7 ??(3), and 0.08Si+(C—Nb/8)+0.015Cr+0.011Ni+0.03W+0.02Mo<0.96 ??(4), wherein the symbol of each element corresponds to the amount (% by mass) of each element in the cast steel.

Abstract: Precipitation-hardened, martensitic, cast stainless steel having a composition comprising, by mass, 0.08-0.18% of C, 1.5% or less of Si, 2.0% or less of Mn, 0.005-0.4% of S, 13.5-16.5% of Cr, 3.0-5.5% of Ni, 0.5-2.8% of Cu, 1.0-2.0% of Nb, and 0.12% or less of N, the amounts of C, N and Nb meeting the condition of ?0.2?9(C %+0.86N %)?Nb %?1.0, the rest being Fe and inevitable impurities, and having a structure in which Cu precipitates having an average particle size of 0.1-0.4 ?m are dispersed in a tempered-martensite-based matrix.

Abstract: A low-thermal expansion cast steel having an average linear thermal expansion coefficient of less than 4.0×10−6/° C. in a range of room temperature to 100° C. and excellent machinability has a chemical composition (by mass) comprising 0.4-0.8% of C, 0.5% or less of Si, 1.0% or less of Mn, 0.01-0.3% of S, 30-40% of Ni, and 0.005-0.1% of Mg, the balance being substantially Fe and inevitable impurities, the contents of S and Mn satisfying S≦(1/4) Mn or (1/4) Mn<S≦(1/4) Mn+0.05.

Abstract: An additive for use in producing spheroidal graphite cast iron of the present invention contains a fine particle of magnesium oxide having a purity of 90 weight % or more and at least one selected from the group consisting of a graphite-spheroidizing material, an inoculant and a graphite-spheroidizing inoculant. The fine particle of highly pure magnesium oxide increases the number of nuclei in a melt, and as a result thereof, increases the graphite spheroid count of a spheroidal graphite cast iron being produced. Another additive for use in producing spheroidal graphite cast iron of the present invention contains at least one selected from the group consisting of a graphite-spheroidizing material, an inoculant and a graphite-spheroidizing inoculant, and an oxide of a metal which has, at a temperature of a melt at a time when subjected to a graphite-spheroidizing treatment, an affinity for oxygen smaller than that of a graphite-spheroidizing element being used in the graphite-spheroidizing treatment.