Thermal Simulation of MnS Evolution in Solidification of a Low-Carbon Alloy Steel Bloom

Abstract

The continuous casting process of a newly developed low-carbon alloy steel is simulated using a thermal simulation method to investigate the evolution of MnS inclusion. The results indicate that MnS mainly appears as aggregated small-sized spherical shapes (type I MnS) in the chill zone of the bloom, while in columnar zone, it tends to form strip-like or irregular morphologies (type II MnS), and no type III MnS is observed. The size of MnS increases from the surface to the center of the samples, with the maximum equivalent diameter increasing from 1.2 to 6.0 μm. A model, considering the effects of solute redistribution and cooling rate, is established to calculate the precipitation and growth of MnS in continuous casting bloom, which is achieved by coupling theoretical calculations with the discrete solidification units. The calculated results demonstrate that sulfur segregation is the controlling factor for the precipitation and growth of MnS, which are well consistent with experiments. This work suggests that enhancing the cooling rate in the secondary cooling zone or improving homogenization of this new low-carbon alloy steel bloom can effectively reduce the growth rate of MnS and mitigate the formation of type II MnS.