Influence of Electropulsing Pretreatment on Solid-State Graphitization of Spherical Graphite Iron

The solid-state graphitization process of spherical graphite iron after electropulsing pretreatment was observed in-situ by using a high-temperature confocal scanning laser microscope (HTCSLM). The influence of electropulsing pretreatment on the decomposition of cementite and the formation of graphite during the solid-state graphitization was studied. The result indicates that the electropulsing pretreatment can accelerate the decomposition of cementite, and make more neonatal graphite in small size be formed near the cementite. The neonatal graphite nucleates and grows chiefly at the temperature range of 800 to 850°C, and the average growth rate of neonatal graphite is 0.034 μm2/s during the heating process. For the spherical graphite iron after normal and electropulsing pretreatment, the decomposition rate of cementite during the heating process is 0.16 and 0.24 μm2/s, respectively. Analysis shows that the electropulsing pretreatment promotes the dislocation accumulation near the cementite, consequently, the decomposition of cementite and the formation of neonatal graphite is accelerated during the solid-state graphitization.