Toshinori Kowata

Effect of Rare Earth Elements on Chill Formation and Nodule Count in Thin-section Spheroidal-Graphite Cast Iron

It was found that there was a close relationship between chill formation and nodule count in spheroidal-graphite (s-g) cast irons and, further, that there was a critical nodule count above which chill did not appear. The relationship between the critical nodule count and the cooling rate of specimens was expressed in the following quadratic equation:N=0.58R2+19.07R+1.01where N is the critical nodule count (mm−2) and R is the cooling rate (°C/sec). Nodule count was increased by adding small amounts of a rare earth in combination with small amounts of calcium. Some heterogeneous phases with diameters of 1 μ or more were observed at the centres of graphite spheroids. These phases were composed of spherical rare-earth sulphides containing MgS, CaS and MgO. It is suggested that rare-earth sulphides contribute as a substrate on which graphite spheroids are formed in thin section cast irons, containing rare earth elements.

Effect of Eight Individual Rare-earth Elements on the Graphite Nodule Count of a Thin-section of Spheroidal-graphite Cast Iron

AbstractEight rare-earth elements, Y, La, Ce, Pr, Nd, Sm, Dy, and Yb, were added individually to two irons, one containing 0.02% S and the other 0.08% S. After nodularisation, the metal was poured ...