Abstract
Continuously cast (CC) 0.1mass% C steels with or without P addition have been produced, and their microstructures have been characterized. The process to optimize the microstructure of the CC steels containing high impurities has been established through solidification and thermo-mechanical treatment. Although rapid solidification is effective in refining the γ grain structure and for dispersing the segregation of impurities finely, P addition changes the α grain structure dramatically and decreases the γ-grain size. Based on the mapped EPMA data for P and Mn, the local equilibrium calculation was made to discuss the γ grain growth behavior in the solidification path. Since phosphorus stabilizes the δ-ferrite and lowers the transformation temperature from δ to γ, the pinning effect of the δ-ferrite on the γ-grain boundary migration is expected in the temperature range of the rapid γ grain growth. The Mn segregation was also reduced with the P addition.
