Microstructure of Cast Strip in 0.1 mass%C Steels Containing Phosphorus

Abstract

Cast strips of 0.1 mass%C steels with phosphorus contents ranging from 0.01 to 0.2 mass% have been produced by using a twin drum type continuous casting machine, and their microstructures have been characterized. Fine dendrite structure in the strips provides a fine dispersion of the segregated phosphorus regime. Phosphorus addition changes the α grain structure dramatically and decreases the γ grain size. The EPMA (Electron Probe Micro Analyzer) mapping and the diffusion analysis of phosphorus in the γ phase indicate the presence of a retained δ phase in the austenite temperature. The pinning effect of the δ-ferrite on the γ-grain growth must be kept in the temperature range of the rapid γ grain growth. The balance of strength and ductility for the cast strip is improved as the phosphorus content increases.