Quantitative Analysis of Contamination of Molten Steel in Tundish

Recently, high grade quality has been demanded for strips and surface-treated steel plates. Since non-metallic inclusions are the main cause of steel plate defects, the reduction of inclusion quantity is a very important problem for steelmaking. In particular, the cleanliness of molten steel in a tundish plays a crucial part in improving the quality of steel plate as well as in preventing immersion nozzle clogging. The tundish includes the functions of flotation and removal of inclusions, though, some contamination to the molten steel also occurs in the tundish. Therefore, it is necessary to make clear the cause of each pollutant and its level in order to produce super clean steels. In this study, the contamination causes of molten steel in the tundish and their influences were analyzed by continual metal sampling during operation with respect to the size, number and composition of the inclusions. The results are as follows: (1) Air oxidation of molten steel is the biggest factor of contamination. (2) The influence of air oxidation decreases and the pollutions of slag increases during continuous operations.