Kinetics of MnS Inclusions Generation in Steel - Nucleation, Growth and Maturation

In this research, a complete MnS growth model for nucleation, solidification growth, and maturation was developed to accurately predict the size of MnS in steel. Three cooling rates (0.5 K/s, 1.5 K/s, and 5 K/s) were applied to the model. And used high-temperature confocal experiments to ensure the samples were cooled at three different rates. The results show that the MnS sizes of the samples are 4.84 µm, 2.15 µm, and 1.43 µm, under three different cooling rates. The model calculations for the MnS sizes under three cooling rates were 5.24 µm, 3.02 µm, and 1.66 µm, respectively. The calculations were consistent with the experiments, validating the accuracy of the model. During the calculation process, it was discovered that the growth size of MnS is at the nm level during the nucleation area and maturation area. The size change of MnS in the solidification stage was in the µm level. Simultaneously, the impact of different cooling rates on the solidification microstructure of steel was observed through high-temperature confocal experiments. The results show that the microstructure of the samples were the same for three cooling rates. The organisational transformation process: L → L + γ → γ → γ → γ → γ → γ + P.