Effect of P Concentration on Precipitation of Iron-phosphide during the Formation of Center-segregation in Hyper-peritectic Steel Slab Cast

Among the internal defects of cast steel products, the center segregation deteriorates the ductility and fatigue strength of high strength steel. Therefore, exact understanding of formation mechanism of center segregation and development of the countermeasure technologies are necessary. Kurosawa et al. reported that iron-phosphide could be observed in the center-segregated region of high phosphorous and hyper-peritectic steel slabs. However, the precipitation mechanism of iron-phosphide has not been fully clarified. Therefore, in this study, in order to clarify the precipitation mechanism of iron-phosphide in the final solidification of CC slab, the melting behavior of the center segregation region of high phosphorous and hyper peritectic steel slab has been investigated by using high temperature observation equipment installed with the image furnace. Additionally, the enrichment of solute in the inter-dendritic region and the further enrichment of solute element during the final solidification was modelized by using micro and macro segregation model. In Fe–C–P ternary eutectic solidification system, the effect of phosphorous concentration on the precipitation mechanism of iron-phosphide during the formation of center segregation was discussed.