FORMATION OF TEMPERATURE FIELDS AND THERMAL STRESSES ARISING DURING SOLIDIFICATION OF CYLINDRICAL CONTINUOUSLY CAST STEEL BILLETS

The article presents investigation results of the effect of inhomogeneity of boundary conditions on the intensity of metal cooling in the process of continuous casting of cylindrical billets from corrosionresistant steels. It is assumed that the boundary conditions are nonuniform along the billet perimeter. In the longitudinal direction, the cooling intensity is assumed to be constant within the cooled sector of the billet. During the research it was believed that there are flows of thermal energy between the cooling sectors. A comparative analysis of temperature gradients and resulting thermal stresses in the solidified billet at different cooling intensities realized in the secondary cooling zone was carried out The values of thermal stresses are compared with the maximum permissible for each grade of steel in order to find those cooling conditions in which the thermal stresses do not exceed the permissible values. Based on the results obtained, conclusions are drawn about the effect of cooling intensity on the occurrence of external and internal defects in the resulting cylindrical continuous cast billets. The authors have also made the conclusions about the effect of inhomogeneity of the boundary conditions on the formation of temperature fields in a solidified cylindrical continuously cast billet. The results of the conducted studies are presented in a graphic form and their detailed analysis is carried out. To calculate the temperature fields in the solidifying billet, a specially developed mathematical model was used, based on the equation of nonstationary heat conductivity. For the calculation of thermal stresses, known mathematical formulas have been used that allow calculating the values of thermal stresses arising between cooling zones in the solidifying billet during the continuous casting of steel. The obtained data are of high practical importance, since they can be used to develop rational cooling regimes, in which excess permissible thermal stresses will not be observed. This, as a consequence, will reduce the number of internal and external defects arising in the solidifying continuously cast billet.

1. Evteev D.P., Kolybalov I.N. Nepreryvnoe lit’e stali [Continuous casting of steel]. Moscow: Metallurgiya, 1984, pp. 131–135. (In Russ.).

2. Kan Yu.E. Process control of cast billets production. In: Nepreryvnaya razlivka stali [Continuous casting]. Moscow: Metallurgiya, 1989, pp. 9–16. (In Russ.).

3. A studу of the continuous casting of steel. Brussels: International Iron and Steel Institute, 1977. (Russ.ed.: Lean J.B. Issledovanie nepreryvnoi razlivki stali. Moscow: Metallurgiya, 1989, pp. 9–16).

4. Samoilovich Yu.A., Timoshpol’skii V.I., Trusova I.A., Filippov V.V. Stal’noi slitok: v 3-kh t. T. 2. Zatverdevanie i okhlazhdenie [Steel ingot: in 3 vols. Vol. 2. Solidification and cooling]. Minsk: Bel. navuka, 2000, 637 p. (In Russ.).

5. Malinochka Ya.N., Moiseeva L.A., Esaulova T.V. Some defects in continuously cast slabs and metal quality improvement. Stal’, 1987, no. 10, pp. 27–30. (In Russ.).

6. Mishchenko I.O. Upravlenie urovnem defektov poverkhnosti i makrostruktury nepreryvno-litykh slyabov MNLZ: avtoref. dis... kand. tekh. nauk. [Management of defects level of surface and macrostructure of cast slabs: Extended Abstract of Cand. Sci. Diss.]. Moscow: MISiS, 2006, 25 p. (In Russ.).

7. Krayushkin N.A., Kuznetsova N.P. Investigation of thermal conditions of round billets of high-quality steel solidification for semicontinuous casting. Izvestiya VUZov. Chernaya metallurgiya = Izvestiya. Ferrous Metallurgy. 2012, no. 7, pp. 45–48. (In Russ.).

8. Kuznetsova N.P., Nikitin D.A. Comparative analysis of the process of semicontinuous casting of steel in Russia and Europe. In: 66-e dni nauki NITU “MISiS” [66th Scientific Days in NUST MISIS]. Moscow: MISiS, pp. 287–294. (In Russ.).

9. Emel’yanov V.A. Teplovaya rabota mashin nepreryvnogo lit’ya zagotovok: Uchebnoe posobie [Thermal operation of continuous casting machines: Textbook]. Moscow: Metallurgiya, 1988, 142 p. (In Russ.).

10. Skvortsov A.A., Akimenko A.D., Ul’yanov V.A. Vliyanie vneshnikh vozdeistvii na protsess formirovaniya slitkov [Influence of external influences on the formation of ingots]. Moscow: Metallurgiya, 1991, 216  p.

11. Dozhdikov V.I. Teplofizicheskie zakonomernosti formirovaniya nepreryvnogo slitka i sovershenstvovanie sistem ego okhlazhdeniya: avtoref. diss...doktora tekhn. nauk [Thermophysical regularities in the formation of a continuous ingot and the improvement of its cooling systems: ExtendedAbstract of Dr. Tech. Sci. Diss.]. Moscow: 1995, 46 p. (In Russ.).

12. Kuznetsova N.P., Krayushkin N.A. Research of thermal modes of solidification in semi-continuous casting of round steel ingots for the production ofseamlesstubes. Izvestiya VUZov. Chernaya metallurgiya = Izvestiya. Ferrous Metallurgy. 2014, no. 3, pp. 34–38. (In Russ.).

13. Ierusalimov I.P., Sukovatin I.V. Investigation of dynamics of strand movement in caster. Stal’. 2003, no. 4, pp. 26–29. (In Russ.).

14. Zhuravlev V.A., Kolodkin V.M. CAD technology of metallurgical processes of crystallization. Liteinoe proizvodstvo. 1986, no. 4, pp.  27–28. (In Russ.).

15. Gusovskii V.L., Lifshits A.E. Metodiki rascheta nagrevatel’nykh i termicheskikh pechei: uchebno-spravochnoe izdanie [Methods for calculating the heating and heat treatment furnaces: Educational and reference book]. Moscow: Teplotekhnik, 2004, 400 p. (In Russ.).

16. Temlyantseva M.V, Oskolkova T.N. Treshchinoobrazovanie v protsessakh nagreva i okhlazhdeniya stalei i splavov [Cracking in heating and cooling processes of steels and alloys]. Moscow: Flinta: Nauka, 2005, 195 p. (In Russ.).

17. Krasnokutskii P.G., Krivandin V.A., Bezrukov V.I., Ol’yak V.D. Thermal stresses in a high-speed jet of metal heating. Kuznechnoshtampovochnoe proizvodstvo. 1983, no. 11, pp. 25–27. (In Russ.).

18. Mirsalimov V.M., Emel’yanov V.A. Napryazhennoe sostoyanie i kachestvo nepreryvnogo slitka [Stress state and quality of continuous ingot]. Moscow: Metallurgiya, 1990, 151 p. (In Russ.).

19. Taits N.Yu. Tekhnologiya nagreva stali [Technology of steel heating]. Moscow: Metallurgizdat, 1962, 567 p. (In Russ.).

20. Krasnokutskii P.G., Krivandin V.A., Ol’yak V.D., Bezrukov V.I. Determination of permissible intensity of metal heating. Izvestiya VUZov. Chernaya metallurgiya = Izvestiya. Ferrous Metallurgy. 1984, no. 7, pp. 115–119. (In Russ.).