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The behavior of non-metallic inclusions in LCAK(low carbon aluminum killed)steel produced by BOF(basic oxygen furnace)-LF(ladle furnace)refining-FTSC(flexible thin slab continuous caster)production route was investigated.The results showed that,LF refining for LCAK steel could decrease the wT[O] significantly,and the inclusions were modified by Ca treatment,which prevented nozzle clogging efficiently.However,owing to the unstable casting condition in the earlier stage of casting,a severe reoxidation occurred,accompanied with mold slag entrapment.The transformation of non-metallic inclusions during the steelmaking process was Al2O3→MgO-Al2O3 type inclusion→MgO-Al2O3-CaO type inclusion with a CaS ring,and the mechanism of the transformation was proposed and discussed via thermodynamic and kinetic analysis.Besides,to avoid CaS precipitation,the product of w2[Al]×w3[S] in steel should be less than 2.0×10-10 at 1873 K,which remands higher desulfurization ratio during LF refining.
The behavior of non-metallic inclusions in LCAK (low carbon aluminum killed) steel produced by BOF (basic oxygen furnace) -LF (ladle furnace) refining-FTSC (flexible thin slab continuous caster) production route was investigated. The results showed that, LF refining for LCAK steel could decrease the wT [O] significantly, and the inclusions were modified by Ca treatment, which prevented nozzle clogging efficiently. Still, due to the unstable casting condition in the earlier stage of casting, a severe reoxidation occurred, with mold slag entrapment. The transformation of non-metallic inclusions during the steelmaking process was Al2O3 → MgO-Al2O3 type inclusion → MgO-Al2O3-CaO type inclusion with a CaS ring, and the mechanism of the transformation was proposed and discussed via thermodynamic and kinetic analysis. Besides, to avoid CaS precipitation, the product of w2 [Al] × w3 [S] in steel should be less than 2.0 × 10-10 at 1873 K, which remands higher desulfurization ratio during LF refining.