ON MODELING PROCESSES IN CONTINUOUS CASTING MOLD

The work focuses on modeling of processes occurring in the mold with a new patented cooling system in continuous casting machine, in particular, at temperature drop in metal of the stock and in the wall along the height of the mold, on which quality of the resulting billet depends. In the review, works are referred in which slag- forming mixtures (SFM) are investigated that affect heat flow from stock metal to the mold. Foreign authors put emphasis on “soft” cooling of the mold by selection of the SFM. Improvement in process of stock metal cooling in the mold is primarily aimed at improving quality of slab surface, increasing resistance of the mold and increasing productivity of machine, which, according to several authors, can be achieved by mathematical modeling of the process. The problem of mold cooling depends directly on convective motion of liquid steel in the mold, which is considered in a number of works of foreign authors. Use of the principle of heat pipes operation in cooling system of the machine mold, in particular, using porous material with water and air operating medium, as well as the question of liquid droplets evaporation on nanostructured super-hydrophilic surfaces, draws attention of researchers. Cooling of the mold at metal casting speeds of more than 7  m/min, accompanied by an increase in heat flux density, is an urgent task and is considered by a number of authors. Interrelation of the main parameters of the process is determined using Rayleigh dimension theory. Temperature gradient in metal of the mold wall is determined as the main parameter, depending on casting speed (time of stock metal forming in the mold), properties of poured metal (heat capacity, heat conductivity), thermal conductivity of the mold wall, and temperature drop in molded metal. Exponents for similarity criteria are determined taking into account available experimental data on dependence of heat flux density on accepted speed of steel casting, steel parameters. The ratio ∆t_c  /t_c (where ∆t_c is an average temperature difference across the wall thickness, tc is an average value of a wall temperature) for the mold with the existing and the new (patented) cooling system allows us to determine temperature difference in metal of the billet, which in two compared cooling systems of the mold comprises ∆t_м1  =  450  °С and ∆t_м2  =  231  °С, and the ratio – ∆t_м1/Δt_{м 2} is 1,95  times. Decrease in metal temperature drop ∆t_м2 indicates more “soft” cooling of the mold with a new cooling system.

1. Design of the sleeve mold. Danieli Centro Met. 8 th European Continuous Casting Conference, 23 – 26 June 2014. Austria, Graz, 2014, pp. 60–62.

2. Kim S.Y., Choi Y.S., Hwang J.Y., Lee S.H. Mold heat transfer behavior at hing casting speed over 7 m/minute in the CEM, POSCO. Iron Steel Technology. 2016, vol. 13, no. 7, pp. 47–56.

3. Raudensky M., Tseng A.A., Horsky J., Kominek J. Recent developments of water and mist spray cooling in continuous casting of steels. Metallurgical Research Technology. 2016, vol. 113, no.  5, pp.  509.

4. Singh V., Das S.K. Thermofluid mathematical modeling of steel slab caster: progress in 21 st. century. ISIJ International. 2016, vol.  56, no. 9, pp. 1509–1518.

5. Hanao M., Kawamoto M., Yamanaka A. Influence of mold flux on initial solidification of hypo-peritectic steel in a continuous casting mold. Tetsu-to Hagane = Journal of the Iron and Steel Institute of Japan. 2014, vol. 100, no. 4, pp. 581–590.

6. Kania H., Nowacki K., Lis T. Impact of the density of the mould powder on thickness of the layer of liquid slag in the continuous caster mould. Metalurgija. 2013, vol. 52, no. 2, pp. 204–206.

7. Furumai K., Miki Y. Molten steel flow control technology for decreasing slab defects. JFE Giho. 2016, no. 38, pp. 36–41.

8. Kratzsch Ch., Timmel K., Eckert S., Schwarze R. URANS simulation of continuous casting mold flow: Assessment of revised turbulence models. Steel Research International. 2015, vol. 87, no. 4, pp.  400–410.

9. Sengupta J., Yavuz M. Metin. Nozzle design for ArcelorMittal Dofasco’s no. 1 continuous caster for minimizing sliver defects. Iron and Steel Technology. 2011, no. 7, pp. 39–47.

10. Lee P.В., Ramirez-Lopez P.E., Mills K.C. etс. Review: the “butterfly effect” in continuous casting. Ironmaking and Steelmaking. 2012, vol. 39, no. 4, pp. 244–253.

11. Tingzhen Ming, Yong Tao. Improvement of heat transfer in a pipe filled with porous material. In: The 15th International Conference on Heat Transfer (IYNC-15). 10–15 August, 2014. Japan, Kyoto, 2014, pp. 89–91.

12. Jorge Padilla, Van P. Carey. Experimental study of phase transition on nanostructured superhydrophilic surfaces. In: 15th International Conference on Heat Transfer (IYNC-15). 10–15 August, 2014. Japan, Kyoto, 2014, pp. 102–104.

13. Vdovin K.N., Larina T.P., Yachikov I.M., Pozin A.E. Mathematical modeling of slab solidification in a continuous casting mold. Izvestiya VUZov. Chernaya metallurgiya = Izvestiya. Ferrous Metal lurgy. 2011, no. 2, pp. 38–41. (In Russ.).

14. Makurov S.L., Smirnov A.N., Epishev M.V., Shlemko S.V. The study and optimization of technological properties of slag-forming mixtures for steel high-speed continuous casting. Izvestiya VUZov. Chernaya metallurgiya = Izvestiya. Ferrous Metallurgy. 2010, no.  12, pp. 13–16. (In Russ.).

15. Stulov V.V. Fizicheskoe modelirovanie okhlazhdeniya vysokotemperaturnoi tekhniki (v metallurgii) [Physical modeling of cooling of high-temperature equipment (in metallurgy)]. Komsomolsk-on-Amur: IMiM DVO RAN, 2012, 142 p. (In Russ.).

16. Stulov V.V. Analysis of similarity of physical processes during simulation of cooling of machine crystallizers. Journal of Machi­ nery Manufacture and Reliability. 2012, vol. 41, no. 1, pp. 6

17. Stulov V.V. Simulation of steel cooling in crystallization tanks. Journal of Machinery Manufacture and Reliability. 2011, vol. 40, no. 1, pp. 59–62.

18. Stulov V.V. Simulation of heat transfer on cooling molds. Journal of Machinery Manufacture and Reliability. 2011, vol. 40, no. 4, pp.  366–371.

19. Stulov V.V., Odinokov V.I., Ogloblin G.V. etc. Physical simulation of continuously cast deformed steel billet production process. Izvestiya VUZov. Chernaya metallurgiya = Izvestiya. Ferrous Metallurgy. 2009, no. 8, pp. 41–46. (In Russ.).

20. Hanao M., Kawamoto M., Yamanaka A. Influence of mold flux on initial solidification of hypo – peritectic steel in a continuous casting mold. Tetsu–to-Hagane = Journal of the Iron and Steel Institute of Japan. 2014, vol. 100, no. 4, pp. 581–590.

21. Stulov V.V. Sposob okhlazhdeniya kristallizatora [Method of the mold cooling]. Patent no. 2601713 RF. Byulleten’ izobretenii. 2016, no. 10. (In Russ.).

22. Stulov V.V. Cooling of a mold at preforming cylindrical continuous cast steel billets. Journal of Machinery Manufacture and Reliability. 2017, vol. 46, no. 1, pp. 57–62.

23. Migai V.K. Modelirovanie teploobmennogo energeticheskogo oborudovaniya [Modeling of heat-exchange of power equipment]. Leningrad: Energoatomizdat, 1987, 254 p. (In Russ.).

24. Bulanov L.V., Korzunin L.G., Parfenov E.P. etc. Mashiny nepreryvnogo lit’ya zagotovok. Teoriya i raschet [Machines for continuous casting of blanks. Theory and calculation]. Shalaev G.A. ed. Ekaterinburg: Ural’skii tsentr PR i reklamy, 2003, 320 p. (In Russ.).