Peter the Great St. Petersburg Polytechnic University (St. Petersburg, Russia):

A. A. Kazakov, Dr. Eng., Prof., e-mail: kazakov@thixomet.ru
E. I. Kazakova, Leading Engineer
A. A. Kur, Cand. Eng.

Continuous cast slabs obtained on curvilinear casting machine have an asymmetric macrostructure with reference to their wide faces. This asymmetry is associated with a different coefficient of heat transfer when feeding water from above and from below to wide faces with a small and large radius, respectively. In such complex asymmetric thermo-physical and hydrodynamic conditions of solidification, a centerline segregation of the slab is formed. Slab centerline segregation may be narrow or wide dependent upon the development of the above-mentioned processes. To reveal the slab centerline segregation, the samples were etched with a 15 % aqueous solution of ammonium persulphate for 10–30 minutes. The images of the slab centerline segregation structure and their evaluation were obtained using the Thixomet Pro image analyzer. A wide segregation zone in a slab always leads to a high class of centerline segregation in the plate at any volume fraction of segregation spots in the slab central zone. In the absence of a wide slab centerline segregation, the class of plate centerline segregation is linearly increased with an increase of the volume fraction of segregation spots in the narrow slab centerline segregation.

1. Sladkoshteev V. T., Potanin R. V., Suladze O. N., Rutes V. S., Continuous Casting of Steel on Radial Installations. Metallurgiya. Moscow. 1974.
2. Moshkunov V. V., Stolyarov A. M., Influence of soft reduction on a macrostructure continu-ously cast slab from tube steel. Vestnik of Nosov Magnitogorsk State Technical University. 2012. No. 4. pp. 45–47.
3. Yang X. G., Xu Q. T., Wu C. L., Chen Y. S., Experimental study of the continuous casting slab solidification microstructure by the dendrite etching method. IOP Conf. Series: Materials Science and Engineering. 2017. Vol. 283. DOI: 10.1088/1757-899X/283/1/012017.
4. Efimov V.A., Casting and crystallization of steel. Metallurgiya. Moskow. 1976. 522 p.
5. Mayer F., Wu M., Ludwig A. On the Formation of Centreline Segregation in Continuous Slab Casting of Steel due to Bulging and/or Feeding. Steel Research Int. 2010. Vol. 81. No. 8. pp. 660–667. DOI: 10.1002/srin.201000122
6. Mayer F., Wu M., Ludwig A. Study of Centerline Macrosegregation in Steel Continuous Casting with a Two-Phase Volume Averaging Approach. Modeling of Casting Welding and Advanced Solidification Processes. 2009. Warrendale. Pa. pp. 279-286.
7. Réger M., Ver B., Józsa R. Control of Centerline Segregation in Slab Casting. Acta Polytechnica Hungarica. 2014. Vol. 11. No. 4.
8. Miyazaki M., Isobe K., Murao T. Formation Mechanism and Modeling of Centerline Segregation. Nippon Steel Technical Report. Aug. 2013. No. 104.
9. Furtmueller C., del Re L. Control Issues in Continuous Casting of Steel. 17^th IFAC World Congress (IFAC’08), Seoul, Korea, July 6–11, 2008. Vol. 41. Iss. 2. pp. 700–705. DOI: 10.3182/20080706-5-KR-1001.00118
10. Sengupta J., Thomas B. G., Wells M. A. The Use of Water Cooling during the Continuous Casting of Steel and Aluminum Alloys. Metallurgical and Materials Transactions: A. 2005 (Jan.). Vol. 36. Iss. 1. pp. 187–204.

11. Kazakov A. A. Kiselev D. V. Industrial Application of Thixomet. Metallography, Microstructure, and Analysis. 2016. DOI: 10.1007/s13632-016-0289-6. 
12. Kazakov A. A., Chigintsev L. S., Kazakova E. I., Ryaboshuk S. V., Markov S. I. Technique for estimation of segregation strip of sheet rolled metal. Chernye metally. 2009. No. 12. pp. 17–22.