Numerical understanding of MnS precipitation influence on solute micro-segregation during solidification

To illuminate the effects of MnS precipitation on solute micro-segregation, a coupled model of micro-segregation and MnS precipitation was built by the finite-difference method (FDM). Sulfur-bearing steel system with contents of S at 0–0.1 wt.% and C at 0–0.8 wt.% was used to analyze the influence of MnS precipitation on solidification behavior. The results show that MnS precipitation begin to affect solidus temperature and zero strength temperature (ZST) when the content of S and C reaches 0.001 wt.% and 0.085%, respectively. The micro-segregation of Mn and S are suppressed by MnS precipitation. The micro-segregation ratio of sulfur drops from 45.80 to 20.30, from 2.29 to 1.90 for manganese. At the same time, MnS precipitation makes the solidification finish about 10 °C in advance, resulting in the intensified micro-segregation of C, Si, and P. Besides, MnS precipitation also affectes the inter-dendritic distribution of solutes during solidification.