Effect of MgO on Crystallization Behavior of CaO–SiO2–Al2O3 Inclusions in Si–Mn Deoxidized Steel During Solidification Stage

To avoid coarse crystallization of CaO–SiO₂–Al₂O₃ inclusions during the solidification stage of continuous casting process, the effect of MgO on crystallization behavior of these inclusions is investigated. The single hot thermocouple technology experiment results show that the low melting point CaO–SiO₂–Al₂O₃ inclusions do not easily crystallize during the solidification stage. However, with increasing the MgO content from 4.5 to 15.7 wt pct, the initial crystallization temperature of inclusions increases from 1376 K to 1431 K (1103 °C to 1158 °C) and the crystallization ratio increases from 35.45 to 100 pct. The crystallization ability of the inclusions can be predicted by the initial crystallization potential and the viscosity at the melting point. With increasing the MgO content from 0 to 15.7 wt pct, the initial crystallization potential of the inclusions increases from 0.28 to 0.87 and the viscosity of the inclusions at the melting point decreases from 4.47 to 0.56 Pa s. The higher the initial crystallization potential and the lower the viscosity near the melting point, the easier the crystallization of the inclusions occurs. Al₂O₃ mainly acts as the network former and participates in the construction of the network structure. With the increase of MgO content, the crystallization ability of inclusions increases gradually, which is mainly related to the increase of melt structure depolymerization.