Abstract: The morphologies, quantities, sizes, and composition changes of inclusions in two heats of Q195L steel with different oxygen and sulfur contents (G85 and G86) were compared and analyzed for the samples of the converter end, the inlet and outlet of the argon station, the tundish, and the continuous casting slab. Combined with thermodynamic calculations and analysis of the compositions of steel and slag samples, the evolution law of inclusions was studied. The results indicate that the Q195L steel mainly contains Al₂O₃ inclusions, MnS inclusions, and Al₂O₃+MnS composite inclusions, which is consistent with the thermodynamic calculation results. The number density of Al₂O₃ inclusions with a diameter greater than 5 μm increases significantly from the converter end to the inlet of the argon station. This is because high-purity aluminum blocks are added for deoxidation during the converter tapping process. The oxygen content in steel mainly affects the content of large-size inclusions. The O element content in the tundish of G85 heat is higher than that of G86 heat, resulting in a significantly higher content of Al₂O₃ inclusions greater than 5 μm compared to G86 heat. The sulfur content in steel mainly affects the content of fine MnS inclusions. After the inlet of the argon station, the S element content in the molten steel of G85 heat is lower than that of G86 heat, resulting in the content of MnS inclusions greater than 0.2 μm lower than that of G86 heat. The research results provide a theoretical basis for the optimization of the low-cost clean steel platform technology.

Key words: low carbon steel, inclusion evolution, oxygen content, sulfur content