Novolipetsk Metallurgical Plant (Lipetsk, Russia):

V. A. Pimenov, Cand. Eng., Senior Researcher, Chief Specialist, e-mail: pimenov_va@nlmk.com
D. A. Kovalev, Cand. Eng., Acting Director of Directorate for Development of NewTechnologies, e-mail: kovalev_da@nlmk.com

Lipetsk State Technical University (Lipetsk, Russia):

A. K. Pogodaev, Dr. Eng., Prof., First Vice-Rector

The analysis of regularities of heat transfer in the finishing group of a wide-strip hot rolling mill is carried out and mathematical models are proposed to describe thermal processes in various zones of the inter-stand spacings. A significant difference in conditions of heat transfer in the middle, most extended zones of the inter-stand spacing of the finishing group was revealed, which consists in the presence of a large amount of water vapor between the stands and absorption of thermal radiation from the strip by steam. A mathematical model of absorption of radiation from a strip by water vapor is proposed, which complements the models of convective and radiant heat transfer of the strip in the spacing. The difference lies in the determination of the reduced emissivity of the medium/strip system, taking into account the absorption capacity of the vapor, depending on the temperature and partial pressure. Using an extended model of strip cooling in the spacing, a numerical simulation of the rolling process was carried out for the conditions of a 2000 wide-strip mill with various strip cooling schemes. It is shown that the prediction of strip temperatures at the exit of the finishing group without taking into account the absorption of radiation can have an error of up to 25 °C or more, which will negatively affect the prediction accuracy of the structure and mechanical properties of rolled products. It is noted that the detailing of the description of thermal processes in the finishing group makes it possible to reduce uncertainty and increase the adequacy of mathematical models when controlling the mill. The proposed model is included in the integrated model of the 2000 mill finishing group and is used when adjusting the strip cooling modes, which provided a significant reduction in the yield of inappropriate products by the “ripple” defect.

The numerical implementation of the model was carried out by M. N. Oreshina, Cand. Phys.-Math. and M. R. Dabas, Master (Lipetsk State Technical University).

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