The invention relates to a method for reducing a bubble defect of a slab Cr-containing steel grade
casting blank.
Argon gas in a
tundish is operated at a small flow rate, the
argon gas flow rate of astopper rod in the
tundish is less than or equal to 2.0 NL / min, and the
argon gas flow rate of an upper
nozzle is less than or equal to 2.0 NL / min; in the
casting process, the minimum single-flow steel passing is not less than 2.4 tons / min; when the slab width is less than or equal to 1500 mm, three-hole immersive
nozzle is used for
continuous casting, the inclination angle of the holes in both sides is at 15 degrees, and the
area ratio of vertical hole steel passing to the total steel passing is 5-18%; when the slab width is larger than 1500 mm and is small than or equal to 2200 mm, a two-hole immersive
nozzle without vertical holes are used for
continuous casting, and the inclination angle of the nozzle of water in the two holes are at 20 degrees; the superheat degree of
molten steel ofthe
tundish is not less than 12 DEG C; and the distance from the top edge of a
discharge hole of the immersive nozzle to the liquid level of the
molten steel in a crystallizer is 100-160 mm. Accordingto the method, the bubble defect generated by steel grades containing Cr more than or equal to 0.15% is avoided, and the defect of edge portion "peeling"-like formed by bubble
exposure rolling elongation in the
casting blank rolling process is eliminated. The product quality of the steel grade is improved.