Effect of Mg treatment on distribution of inclusions in Fe-O-Al-Mg melt

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This study aims to investigate the effect of Mg treatment on the homogenized distribution of inclusions. Deoxidized experiments with Al (0.05%Al) and Al-Mg (0.05%Al + 0.03%Mg) were carried out at 1873 K respectively and the degree of homogeneity in inclusion dispersion, area density, average size and inter-surface distance of inclusions were studied. The attractive capillary force acts on inclusions was analyzed by in-situ observation by confocal laser scanning microscopy and Kralchevsky-Paunov model. The results show that the proportion of inclusions with inter-surface distance at the range of 10–100 µm is up to 60% after Al-Mg deoxidized 1800 s. Compared with Al2O3 inclusion, the area density of MgAl2O4 inclusions is generally more homogeneous. The in-situ observed results indicate that the inclusions in the steel deoxidized by Al are easy to aggregate and small size Al2O3 inclusions tend to gather around large size Al2O3 inclusions, while the inclusions in the steel deoxidized by Al-Mg tend to distribute more homogeneously. Moreover, the calculated results suggest that the attractive capillary force is larger between inclusions with larger size. The attractive capillary force is larger when the value of smaller size inclusions R1 is gradually close to the value of larger size inclusions R2. The relationship between attractive capillary force and the degree of homogeneity in inclusion dispersion is discussed based on Kralchevsky-Paunov model.