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The reaction between [Al] in molten steel and (SiO₂) in the liquid slag layer was one of the restrictive factors in the quality control for high Al-TRIP steel continuous casting. In this work, the composition and property variations of two slags during a slag-steel reaction were analyzed. Accordingly, the crystalline morphologies of slag were discussed and the solid layer lubrication performance was evaluated by Jackson &#945; factors. In addition, a simple kinetics equilibrium model was established to analyze the factors which affected SiO₂ consumption. The results reflected that slag-steel reacted rapidly in the first 20 minutes, resulting in the variation of viscosity and the melting temperature of slags. The slag-steel reaction also affected the crystal morphology significantly. Slag was precipitated as crystals with a higher melting temperature, a higher Jackson &#945; factor, and a rougher boundary with the consumption of SiO₂ and the generation of Al₂O₃. In other words, although generated Al₂O₃ acted as a network modifier to decrease the viscosity of the liquid slag layer adjacent slab shell, the consumption of SiO₂ led to the deterioration of the lubrication performance in the solid slag layer adjacent copper, which was detrimental to the quality control for high Al-TRIP steel. Finally, a kinetics equilibrium model indicated that it is possible to reduce a slag-steel reaction by adjusting factors, such as the diffusion coefficient k, <inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mi>c</mi> <mrow> <msub> <mrow> <mi>SiO</mi> </mrow> <mn>2</mn> </msub> </mrow> </msub> </mrow> </semantics> </math> </inline-formula>, <inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mi>&#961;</mi> <mi>f</mi> </msub> </mrow> </semantics> </math> </inline-formula> and <inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi>f</mi> </msub> </mrow> </semantics> </math> </inline-formula>, during the actual continuous casting process.