MOLD FLUX FOR CONTINUOUS-CASTING Ti-CONTAINING HYPO-PERITECTIC STEEL AND METHOD THEREFOR

摘要

A mold flux is used in continuous casting of Ti-containing hypo-peritectic steel so as to prevent longitudinal cracks from forming on a surface of a slab. The mold flux contains CaO, SiO2, an alkali metal oxide and a fluorine compound as major components. f(1), f(2) and f(3), which are calculated from the initial chemical composition, are (1.1−0.5×T) to (1.9−0.5×T), 0.05 to 0.40 and 0 to 0.40, respectively, if the Ti content of the molten steel (mass %) is T. The TiO2 content in the melting state during the casting is no more than 20 mass % and the ratio of the first peak height of perovskite to the first peak height of cuspidine in the mold flux film is no more than 1.0.

主权项

1. Mold flux for continuous-casting Ti-containing hypo-peritectic steel, wherein in continuous casting of Ti-containing hypo-peritectic steel,
the mold flux contains CaO, SiO2, an alkali metal oxide and a fluorine compound as major components, chemical composition of the mold flux before the mold flux is put into a mold satisfies the formulas (1), (2) and (3), a TiO2 content of the mold flux in a melting state during the casting is no more than 20 mass %, and a strength ratio of a film of the mold flux in a solidifying state after the casting is no more than 1.0:
1.1−0.5×T≦f(1)≦1.9−0.5×T   (1)0.05≦f(2)≦0.40   (2)0≦f(3)≦0.40   (3),wherein in the formulas (1) to 3),f(1=CaO)h/(SiO2)n   (A)f(2)=(CaF2)h/{(CaO)h+(SiO2)h+(CaF2)h}  (B)f(3)={(alkali metal fluoride)h}/{(CaO)h+(SiO2)h+(alkali metal fluoride)h)}  (C)wherein in the formulas (A) to (C),(CaO)h=WCaO−(CaF2)h×0.718   (D)(SiO2)h=WSiO2   (E)(CaF2)h=(WF−WLi2O×1.237−WNa2O×0.613−WK2O×0.406)×2.05   (F)(alkali metal fluoride)h=WLi2O×1.74+WNa2O×1.35+WK2O×1.23   (G)