EFFECT OF THE PERCENTAGE CARBON EQUIVALENT ON THE NODULE CHARACTERISTICS, DENSITY AND MODULUS OF ELASTICITY OF DUCTILE CAST-IRON

Successful melting and Mg treatment were conducted using a vortex unit which produced spheroidal graphite (SG) Fe ingots having a percentage carbon equivalent (%CE) ranging from 3.782 to 5.240. Microstructure e xamination revealed graphite nodules embedded in a white matrix (unetc hed condition). The variation of %CE proved to have a pronounced effec t on the nodule characteristics. The nodule count showed a maximum val ue at %CE of 4.613. For metal-mould ingots it reached a value of 1584 nodules mm(-2), while for sand-mould ingots it reached a value of 970 nodules mm(-2). Nodule size was found to be inversely proportional to the nodule count for both sand- and metal-mould ingots. The nodularity of all ingots was, in general, higher than 95%. The density of SG Fe was found to decrease gradually (at %CE=3.782) from 7242 to 6969 kg m( -3). The modulus of elasticity(E) showed a boat-like curve having mini mum values of 189 and 192 GPa for the sa nd a nd metal moulds, respect ively.