The conditions were studied under which either eutectic graphite or carbide or both, Can form during freezing in low carbon silicon irons. Experimental variables included: iron composition, (C 1.32 to 2.17, Si 1.56 to 2.35%) small additions of alloying elements, (Ca, Mg, Al, S arid 0) and cooling rate (varying from quenching to slow cooling).

Thle results obtained show that without any alloying additions these irons solidify witb the formation OF eu~tectic carbide. A fully graphitic cast structure can he readily obtained, however, with inoculating additions of either Ca or Mg. The inoculating potential of these elements increases in the presence of small amounts of Al ard 0, hut decreases with the addi tion of S. Bal ancing S with Mn restores and improves graphite nucleation by other elements. Both Ca and Mg promote spherulitic, whilst Al and high C levels, promote flake graphite morphologies. Conditions and mechanisms of formation of euitectic graphite or carbides or their mixtures in low carbon and silicon cast. irons are discussed in thle light Of current theories of solidi ficati on of east irons.