Formation of ferritic structure with eutectic cementite precipitations during the solidification of nodular cast iron

An account is given of certain problems in the solidification and cooling of easily machinable and abrasion-resistant nodular cast iron with a ferritic matrix and precipitations of eutectic cementite and spheroidal graphite. It is shown that the quantity of cementite forming in the eutectic range depends primarily on the graphitisation ability of the cast iron, in particular on the Si content, index of undercooling and average rate of temperature fall in the eutectic range. The quantity of ferrite forming in the eutectoidal range depends principally on the Si content (for constant C content 2.4%), on average rate of temperature fall in the eutectoidal range and also on coefficient k, expressing the ratio of cooling temperature range in the eutectoidal interval occurring below metastable equilibrium, to total range of eutectoidal transformation.