Chair of Thermal Physics, Automation and Furnaces Ecology, Nizhny Novgorod State Technical University, Russia:

V. A. Ulyanov, Doctor of Engineering Sciences, Professor

V. N. Gushchin, Doctor of Engineering Sciences, Professor

E-mail: taep@nntu.nnov.ru

The paper is devoted to study of lowering of possibility of crack forming in continuously cast billets due to organization of rational procedures for metal transfer to slab molds using free-flow pouring nozzles with shifted exit channels. Relation between possibility of crack forming (from one side) and heterogeneity of solidification front, thermal stresses in solidified crust and conditions of melt transfer in a mold (from other side) is established. It was revealed that usage of free-flow pouring nozzle of new design allowed to decrease substantially heterogeneity of solidification front, thermal stresses in crust and to increase qualitative parameters of cast metal. Obtained results testified that number of strips of thready pickling ability lowered and number surfacial cracks decreased by 2-3 times compared with direct casting and by 1.4-1.8 times compared with casting through free-flow pouring nozzle of conventional design (for billets 180x530 mm from 45 and U8 steels). As soon as small compressing stresses occurred on the surface of continuously cast billet at the initial stage of its forming in the case of usage of free-flow pouring nozzles, and it leads to strong billet buckling, melt transfer to a mold should be optimized additionally or mold temperature has to be diminished.

1. Elanskiy G. N. Razlivka i kristallizatsiya stali (Casting and crystal growth of steel). Moscow : Moscow State Evening Metallurgical Institute, 2010. 192 p.

2. Ulyanov V. A. et al. Vnepechnaya obrabotka i razlivka stali (Ladle treatment and steel casting). Nizhny Novgorod : Nizhny Novgorod State Technical University, 2008. 129 p.

3. Parshin V. M., Pavlov V. V., Gushchin V. N. et al. Glukhodonnyy pogruzhnoy stakan (Submerged nozzle with blind bottom). Patent RF, No. 2308353 MPK B22D 41/50. BI No. 29. 2007.

4. Gushchin V. N., Parshin V. M., Kuklev A. V. Stal – Steel in Translation. 2006. No. 12. pp. 21–23.

5. Gushchin V. N., Ulyanov V. A. Metody issledovaniya i razrabotka gradientnykh promyshlennykh tekhnologiy upravleniya teplomassoobmennymi protsessami pri razlivke i formirovanii nepreryvnolitykh i statsionarnykh zagotovok (Research methods and development of gradient industrial technologies of heat mass exchange processes control during casting and formation of continuously cast and stationary billets). Nizhny Novgorod : Nizhny Novgorod State Technical University, 2006. 141 p.