PARAMETER IDENTIFICATION AND OPTIMAL CONTROL OF HEAT TRANSFER IN COOLING LINE OF HOT STRIP ROLLING MILL
Keywords:
modeling, hot rolled steel, heat transfer, steel, cooling line, control, run-out tableAbstract
The numerical simulation of mechanical properties of hot-rolled products is of major significance for material characterization as well as material development. The basis for this is the knowledge of the material-specific phase transformations and of the initial microstructure originating from the deformation steps before entering into the cooling line. Additionally, the technological conditions on the run-out table (ROT) are essentially for transformation kinetics.
In order to simulate these processes, the plant-specific heat transfer coefficient has to be identified. To this end, steel samples with thermocouples inside are transported with defined velocities through the cooling line of the continuous pilot plant at the Institute of Metal Forming in Freiberg. Furthermore, the material and its movement must be taken into account as characteristics of the ROT. Here, the amount and distribution of the cooling medium, the streaming situation in the segments, the nozzle geometry, and the impact pressure of the cooling medium on the surface of the rolled material are the most important influencing parameters.
This paper describes the possibilities for determining and simulating the heat transfer in the cooling line under realistic industrial conditions. In addition, it discusses optimal control strategies for the cooling line to achieve a desired temperature and phase distribution on the run-out table. The results contribute to new technology and material developments at the pilot plant, which are also suitable for the transfer to industry.
References
2. Honlinger, M.: Prozesssimulation fiir instationare Abkiihlvorgange bei der beschleunigten Kiihlung von Grobblechen mit laminarem Wasservorhang; Dissertation, TU Clausthal, Institut fur Energieverfahren- stechnik und Brennstofftechnik, 1995.
3. Graf, M.; Kawalla, R.: Deformation behaviour and mechanical properties of oxide scales during hot metal forming processes, Proceedings ICTP 2011, Aachen, 2011.
4. Viscorova, R.: Untersuchung des WUrmeubergangs bei der Spritzwasserkuhlung unter Berucksichtigung des Einflusses der Verzunderung, Dissertation, Institut fur Metallurgie, TU Clausthal, 2007.
5. Puschmann, F.: Experimentelle Untersuchung der Spraykuhlung zur Qualitatsverbesserung durch definierte Einstellung des Warmeubergangs, Ph.D. thesis, Otto von Guericke UniversitUt Magdeburg, Juli 2003, http://diglib.uni-magdeburg.de/Dissertationen/2003/frapusc hmann.htm.
6. Sun, C.G.; Han, H. N.; Lee, J. K.; Jin, Y. S.; Hwang, S. M.: A finite element model for the prediction of thermal and metallurgical behaviour of strip on run-out-table in hot rolling, ISIJ International 42 (2002), No. 4, pp. 392-400.
7. Hashimoto, T.; Yoshioka, Y.; Ohtsuka, T.: Model predictive control for hot strip mill cooling system, Control Applications (CCA), 2010, IEEE International Conference on, pp. 646-651.
8. Alifanov, O. M.: Inverse Heat Transfer Problems, Springer, Berlin, Heidelberg 1994.
9. Troltzsch, F.: Optimal Control of Partial Differential Equations: Theory, Methods and Applications, American Mathematical Society, 2010.
10. Hamed, M. S.: Evaluation of heat transfer coefficients in water spray quenching systems, 20th ASM Heat Treating Society Conference Proceedings, 9-12 October 2000, St. Louis, MOO, ASM International, 2000, pp. 785-790.
11. Totten, G. E.; Bates, C. E.; Clinton, N. A.: Handbook of quenchants and quenching technology, p.239, ASM International, Materials Park, Ohio (1993).
12. Kim, H. K.; Oh, S. I.: Evaluation of heat transfer coefficient during heat treatment by inverse analysis, Journal of Materials Processing Technology 112 (2001), pp. 157-165.
13. Rosch, A.; Troltzsch, F.: An optimal control problem arising from the identification of nonlinear heat transfer law, Archives of Control Science, 1 (XXXVII) (1992), pp. 183-195.
14. Landl, G.; Engl, H. W.; Chen, J.; Zeman, K.: Optimal strategies for the cooling of steel strips in hot strip mills, Inverse Problems in Engineering, 2, Issue 2 (1995), pp. 103-118.
15. W. Bleck; D. Hmberg; U. Prahl; P. Suwanpinij; N. Togobytska: Optimal control of a cooling line for production of hot rolled dual phase steel, Steel Resarch International, first published online, 24.02.2014
