Abstract
The nuclei of spheroidal graphite (here after referred to as SG) was studied using FE-SEM and EDS. Many kinds of SG iron were prepared for the observation, namely, commercial grade Mg- and RE-treated SG iron, pure Fe-C SG iron, pure Fe-C-Ce SG iron and pure Fe-C-Si SG iron. The nuclei of graphite were mainly MgS, RES, FeCl, CaS and SiO2, respectively. The shape of these nuclei was mainly spherical except for the nucleus of the pure Fe-C SG iron. Their diameter ranged from 0.1 to 1.0μm.
These observations suggest no common factors in the chemical compositions of these nuclei. This means that the formation mechanism of SG is not based on the nuclei. One common factor was however the low sulfur activity in these irons. The interfacial energy theory for the formation of SG is thus supported and discussed in this paper.
