Inclusion control study in high aluminum steel

In order to reduce the negative effect of gross Al-rich inclusions on high aluminum steel, both thermodynamic calculations and designed deoxidization experiments were performed in condition of different silicon and aluminum deoxidization sequences. Thermodynamic calculations demonstrated that the complex inclusions with low melting point (harmless inclusions) are more favorable to be formed in condition that the melt was deoxidized using ferrosilicon first and then pure aluminum (Si/Al deoxidization) than that deoxidized using pure aluminum first and then ferrosilicon (Al/Si deoxidization). Al-rich inclusion decreases 83% from Al/Si deoxidization to Si/Al deoxidization. The experimental results showed that the total quantity of inclusions decreases by 24% and the proportion of harmless inclusions is doubled when comparing Si/Al deoxidization with Al/Si deoxidization. The morphology of complex inclusion tends to be spherical, and the mean size is less than 5 μm in condition of Si/Al deoxidization. The formation mechanism of harmless inclusions was discussed, and it is believed that the inclusions can be controlled reasonably in high aluminum steel using Si/Al deoxidization.