Origin of heat transfer anomaly and solidifying shell deformation of peritectic steels in continuous casting

The effect of carbon content of steel melt on the heat transfer in a continuous casting mold was investigated in a laboratory scale mold by simultaneous measurements of the heat flux during solidification of the melt and shrinkage of the resulting shell during solidification and cooling. For peritectic medium carbon steels, the heat flux on the mold surface was subject to an anomalous decrease, since the surface roughness of the shell was substantial, providing an air gap at the shell/mold interface. For ultra low carbon steels, however, the heat flux was large in spite of the fact that surface roughness was also significant. For peritectic medium carbon steels, the deformation of the shell caused by the shrinkage due to δ/γ transformation during and just after solidification is responsible for the formation of the surface roughness, resulting in the heat transfer anomaly. On the contrary, the surface roughness for ultra low carbon steels is formed later on the shell after solidification during cooling, and hence it does not decrease the heat flux at the initial stage of solidification.