The invention relates to continuous-
casting protection
slag for CAS treated ship plate structural steel. The protection
slag is composed of, by weight, 30 percent to 39 percent of CaO, 24 percent to 33 percent of SiO2, six percent to 13 percent of Na2O, five percent to 9.5 percent of F, 0.9 percent to 1.9 percent of optimized
elemental carbon, three percent to six percent of Al2O3, three percent to eight percent of MgO, 0.7 percent to 1.6 percent of Li2O, and 3.0 percent to 5.0 percent of Fe2O3. The
viscosity of the
slag is controlled between 0.07 Pa S and 0.08 Pa S. According to the physical properties of the continuous-
casting protection slag, the
melting point is 1020 DEG C to 1090 DEG C, the
viscosity is 0.07 Pa S and 0.08 Pa S (1300 DEG C), CaO / SiO2 is 1.1 to 1.3, and H2O is smaller than or equal to 0.5 percent. According to the slag, the
melting point of the slag can be reduced, the
alkalinity can be improved, the unit consumption of the protection slag can be improved, the
viscosity of the protection slag can be reduced, and therefore in the
continuous casting process, the melting speed and the flowing-in speed are stably and dynamically balanced, and therefore
lubrication of a primary blank shell of an inner plate blank of a crystallizer is ensured, and the aim of stable and smooth production of the CAS treated ship plate steel is achieved.