Peritectic transformation during cooling of iron-carbon alloy

Peritectic transformation behavior during cooling of iron-carbon alloys is simulated by a numerical analysis. The peritectic transformation, δ+L=γ, is divided into δ-γ transformation at δ/γ interface and L-γ solidification at γ/L interface, and proceeds by the following two mechanisms: (1) carbon diffusion from liquid (referred to as L) through austenite (γ) into δ-ferrite (δ) and (2) precipitation of austenite from δ-ferrite and crystallization of it from liquid due to cooling. Approximately 80% of the austenite formed during the peritectic transformation is the products of δ-y transformation, which may cause the generation of tensile stress in the solidification shell of cast steels due to the difference in density between δ-ferrite and austenite The amount of the δ-γ transformation is largest, when the initial carbon content is 0.17 mass%. However, when the transformation in a well-developed dendrite network structure is focused on, the carbon content for the maximum amount of the δ-γ transformation decreases to 0.14–0.16 mass%, which corresponds to the carbon content at which surface cracking of continuously cast slabs is reported to be most frequent