Abstract: CE (=%C+(1/3)×(%Si)) does not suit experiment results in many cases. In this work, the effect of alloy elements on primary crystal temperature was measured and the relationship between primary crystal temperature (Tc) and carbon equivalent (CEL) was investigated. The results show that Tc (Celsius degree) =1650-110×(%C)-25×(%Si)+3×(%Mn)-35× (%P)-71×(%S)-2×(%Ni)-7×(%Cr); CEL=%C +0.23×(%Si)-0.03× (%Mn)+0.32×(%P)+0.64×(%S) +0.02×(%Ni)+0.06×(%Cr). That is, in hypo eutectic composition, carbon equivalent should be calculated with CEL=%C+ 0.23×(%Si), not with CE=%C+(1/3) ×(%Si).

Key words: Carbon equivalent, Cast iron, Primary crystal temperature, Hypo eutectic composition