As-Cast Grain Refinement of H13 Steel by Cerium Sulfide Formed During Solidification

The cerium sulfide (Ce–S) formed during solidification is used as the heterogeneous nucleation core to refine the as-cast grains. A mathematical model is established to predict the formation of Ce–S, and the main conclusions are as follows. The as-cast grain size is affected by the number, size and type of Ce–S. Increasing the number density of Ce–S significantly reduces the as-cast grain size. As the proportion of cerium monosulfide (CeS) in the Ce–S composition increases, the percentage of Ce–S particles within the size range of 1 to 3 μm also experiences an elevation. These Ce–S are effective nucleation cores, promoting grain refinement. Ce oxide (Ce–O), Ce oxysulfide (Ce–O–S) and manganese sulfide (MnS) are not conducive to grain refinement. Although it is not completely possible to avoid the formation of Ce–O and Ce–O–S, their formation mass can be reduced by decreasing the O content. The formation of MnS can be avoided by reducing the contents of O and S and increasing the Ce content. The refinement of as-cast grains is primarily attributed to Ce–S formed during solidification, particularly CeS. Their formation mass is correlated with the contents of Ce, O and S. Using 0.02 mass pct Ce ensures maximum formation mass of Ce–S during solidification, and the contents of O and S are accordingly controlled as T.S=0.006-1.5×T.O(0.0001≤T.O≤0.002)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$T.S = 0.006 - 1.5 \times T.O \, (0.0001 \le T.O \le 0.002)$$\end{document}.