Study on the influence of non-normal casting on metallurgical behaviour of eight-strand tundish

Abstract

Non-normal casting usually refers to the casting process of tundish where one or more outlets are closed due to the shortage of molten steel supply, difficulty in billet production, equipment failure, sudden accidents and other unconventional problems, which are inevitable in industrial sites. The closure of the outlets will change the flow field of the tundish, which will affect the metallurgical effects such as temperature uniformity and inclusion removal rate, etc. However, the influence of closing various outlets is more controversial at present. In this paper, the influence of non-normal casting under the closures of various outlets on the metallurgical behaviour of an eight-strand tundish is investigated exhaustively by numerical simulation, and new evaluation method of the consistency among the strands based on similarity calculation is proposed. The results show that the abnormal closure of one outlet has little effect on the flow field of the tundish, and the evaluation parameters of the flow characteristics have slightly different from those of the normal casting scheme. Under the condition of abnormal closure of two outlets, the similarity between different strands for the scheme of closing symmetrical outlets is better than that for other schemes, the average residence time and peak time are also extended, and the removal rate of inclusions with the diameters of 5–90 μm increased from 85.95% of normal casting to about 89%. When the production rhythm adjustment needs to reduce the casting speed or selectively close two outlets, closing outlet 1 and outlet 8 is the optimal solution. The consistency among the strands is relatively good, as the average similarity between the outlets is increased from 0.679 under the scheme of reducing the casting speed to 0.736 now. And the low temperature zone is less, and the dead zone ratio is small, 7.85% at the critical velocity of 0.008 m/s. The removal rate of inclusions increased to 89.01%, especially up to 93.62% for large-size (≥50 μm) inclusions. The research results of various schemes for closing the outlets can provide scientific guidance for actual non-normal casting operations.