Effect of MgO Content in Refining Slag on Dissolution of Inclusions

The effect of MgO content in refining slag on the dissolution behavior of Al 2 O 3 and SiO 2 inclusions in Al‐killed and Si‐Mn‐killed steels is investigated. The dissolution process is observed using high‐temperature confocal scanning laser microscopy. The dissolution time of Al 2 O 3 inclusions decreases and their dissolution rate increases with the addition of MgO in the Al 2 O 3 ‐CaO‐MgO‐10%SiO 2 refining slag. Specifically, when the MgO content increases from 0 to 8%, the dissolution rate of Al 2 O 3 inclusions with a size of ≈400 μm increases from 7.48 × 10 −13 m 3 s −1 to 1.35 × 10 −12 m 3 s −1 . Similarly, for SiO 2 inclusions in SiO 2 ‐CaO‐MgO‐5%Al 2 O 3 refining slag, the dissolution time decreases and the dissolution rate increases with increasing MgO content. When the MgO content increases from 0 to 15%, the dissolution rate of SiO 2 inclusions with a size of ≈400 μm increases from 1.27 × 10 −12 m 3 s −1 to 3.64 × 10 −12 m 3 s −1 . The inclusion capacity (Zh) and dimensionless dissolution rate (Ry) are used to predict the dissolution behavior of inclusions in refining slag. It is predicted that for Al 2 O 3 ‐CaO‐MgO‐10%SiO 2 refining slag, an MgO content below 8% is more favorable for the dissolution of Al 2 O 3 inclusions. For SiO 2 ‐CaO‐MgO‐5%Al 2 O 3 refining slag, an MgO content below 15% is beneficial for the dissolution of SiO 2 inclusions.