Rapid Prediction of MnS Precipitation During Slab Continuous Casting of Microalloyed Steel

During steel solidification, solute element segregation at dendrite boundaries intensifies the precipitation of MnS inclusions. The morphology, dimensions, and spatial distribution of these precipitates influence the high-temperature thermoplasticity of continuously cast slabs. Variations in the equilibrium partition coefficients (k_i) of different cooling phases in Q355 microalloyed steel were investigated using thermodynamic calculations. To obtain accurate parameters, the thermodynamic behavior of the continuous casting process was simulated using Marc finite element software for thermal history data at each node of the cooling process. A real-time constant cooling rate model was established, and four different rates were selected to verify the model. Model predictions and observations demonstrated strong agreement, with an error range of 2.2 to 5.2 pct. A method for calculating variable cooling rates was proposed. Based on the heat transfer model, a real-time variable cooling rate model was established and high-temperature confocal laser scanning microscopy (HT-CLSM) was used for observation of the solidification process. This prediction model can effectively characterize MnS precipitation and growth and the effects of casting speed and superheating on the particle size distribution of MnS inclusions. This study provides a rapid and accurate method for predicting MnS precipitation, helpful for optimizing the process of continuous casting.