The effects of Se, CaCO₃and CaO addition on the first stage graphization of malleable iron were evaluated. The results obtained in this work were as follows. 1. Many gas bubbles were found in the white cast iron under Se, CaCO₃addition. 2. Nodular graphite were formed by annealing of the white cast iron with remained gas bubbles. 3. When specimens were annealed, bubbles provided the nucleation sites that were needed in graphite precipitation, so the nucleation rate of graphite was increased. 4. The remained gas bubbles and defects were more effective for the graphitization than metallic compounds.