Direct steel sheet production from solid pig iron

Abstract

In order to investigate the process feasibility of direct steel sheet production from solid pig iron, three different composition of white cast iron strip were made by centrifugal casting machine and H2O/H2 gaseous decarburization reaction of white cast iron strip were investigated under temperature of 975oC and 1100oC respectively. Clear interface between decarburized zone and unreacted cementite core were observed in all cases and reaction was much faster at higher temperature. From microstructural point of view, decarburization of hypo eutectic white cast iron(3.89wt%C) at 1100oC was reasonable condition and at this case 1mm strip was fully covered with decarburized zone within 20minutes. Diffusion of carbon through decarburized austenite was determined as rate controlling step of gaseous decarburization based on parabolic relation between decarburization time and reaction fraction. From carbon diffusion model, average carbon diffusion coefficient at the decarburized zone was calculated as 1.89？10-7(cm2/s) at 975oC and 8.66？10-7(cm2/s) at 1100oC for 3.89wt%C white cast iron and 1.81？10-7(cm2/s) at 975oC and 7.76？10-7(cm2/s) at 1100oC for 4.35wt%C white cast iron respectively. Columnar carbon concentration profile after decarburization was estimated and confirmed by EDS analysis. Finally, homogenization and secondary decarburization at lower temperature was studied in order to obtain ferrite ？ martensite multilayered structure.