Influences of long nozzle pouring position on tundish service life and molten steel quality

As the key equipment in the continuous casting process, the tundish is used to steadily supply molten steel, homogenize the composition and temperature of molten steel, and remove inclusions. Its flow control devices are susceptible to erosion and melting loss induced by scouring of high-temperature molten steel, which further alters the flow field of molten steel. Numerical simulation combined with industrial trials are adopted as research approaches. The service cycle of the tundish is divided into the effective period of flow control devices (0-40 h) and the complete failure period of flow control devices (40 h to tundish shutdown). The influence laws of different pouring point positions on the molten steel flow field inside the tundish at each stage are systematically analyzed, and their effects on molten steel quality and tundish service life are investigated. The obtained results indicate that during the effective period of flow control devices, stable and uniform molten steel flow field can be effectively maintained when the pouring point is arranged at the center of the impact zone. Under this condition, the volume fraction of dead zone reaches the minimum value of 20.17%, and the erosion rate of the impact zone is the lowest at 6.05 mm/h. After the complete melting loss of flow control devices, the distribution of flow field can be optimized when the pouring point is moved backward by 30 mm. The area of vortex region inside the tundish is minimized, the volume fraction of dead zone is reduced to 22.02%, and the erosion rate is decreased by 16.86% compared with the central pouring scheme. Verified by industrial trials, the composite pouring scheme (central pouring is applied during the effective period of flow control devices, and the pouring point of the long nozzle is moved backward by 30 mm in the failure stage) can extend the service life of the tundish to 80.97 h. Meanwhile, the differences in element contents of molten steel among each strand are smaller than those under other pouring modes.