Refractory nozzle for steel ladle tundish

The refractory nozzle is one of the important refractory materials in the tundish for continuous casting. It is mainly used for continuous casting of billets and plays the role of controlling the flow of molten steel. The nozzle must have excellent thermal shock resistance and corrosion resistance to ensure that the molten steel can flow into the mold evenly and stably through the nozzle, thereby ensuring the normal progress of continuous casting. At present, zirconia sizing nozzles are mainly used at home and abroad.

Ladle → tundish using long nozzle protection effect:

(1) Reduce the total oxygen content in the steel: the total oxygen content in the aluminum-killed steel billet is 20-25 ppm for long nozzles and 40-50 ppm for open casting. The decrease in total oxygen indicates that there is less Al2O3 in the slab. Sulfur print inspection indicated that 90% of the billet had no subcutaneous inclusions.

(2) The loss of acid-soluble aluminum in the steel is reduced: the loss of molten aluminum in the ladle → the tundish: for the plug rod ladle, the protection of the long nozzle is 0.0054%, and the open pouring is 0.0119%. For the sliding nozzle ladle, the protection of the long nozzle is 0.0018%, and the open pouring is 0.0196%. With long nozzle protection, 95% of the billet has no Al2O3 inclusions under the skin. There is less Al2O3 in molten steel, reducing the probability of nozzle blockage.

(3) Reduce Al2O3 content in tundish slag: Ladle → tundish uses a long nozzle, and Al2O3 in tundish slag is 20-25%. The Al2O3 of the mold slag is less than 10%; the Al2O3 of the tundish slag is 30-40% during open casting, and the Al2O3 of the mold slag is 10-20%. The Al2O3 in the slag is reduced, which improves the fluidity of the slag, which is beneficial to the uniform heat transfer of the mold and reduces the longitudinal crack and steel breakout.

(4) Improve the quality of cold-rolled sheet: ladle → tundish long nozzle protection pouring, cold-rolled strip-shaped defect waste produced by Al2O3 inclusions is reduced from 24% (open pouring) to 8.8% (protective pouring), and some even down to 0.8%.

However, the disadvantage of using a long nozzle is that the erosion of the impact point of the tundish is aggravated, and the slag under the ladle cannot be seen.