Mathematical Modelling of Roll Cooling and Roll Surface Stress

Abstract

In a hot strip mill, the quality of the rolled products and the productivity of the mill depend on the efficiency of roll cooling to a great extent. To study the influence of the cooling system on roll performance, a good understanding of the thermal aspects of roll cooling is essential. Mathematical models to predict temperature development in the work roll and compute thermal strain induced at the roll surface during rolling were developed and applied to the upper work roll of the 1st stand of the finishing mill of HSM at Tata Steel. The models were used to predict temperatures and thermal stresses/strains in the roll under various cooling conditions, thus examining the efficiency of the existing roll cooling system and exploring the scope of optimizing it.

Theoretical and experimental investigation of thermal and oxidation behaviours of a high speed steel work roll during hot rolling

“…Perez et al [23] predicted the thermal response of a work roll using a mathematical model considering three different levels: independent cycle of the roll, rolling of a strip-rest, and a whole campaign. Strain-life of a work roll during hot rolling was calculated by Corral et al [24] by means of a hybrid, analytic-numerical model, and temperatures and thermal stress/strains in the roll under various cooling conditions was predicted by Saha et al [25] applying a mathematical model. In addition, thermal stress and temperature variations within work rolls in hot strip rolling have also been modelled by Fisher et al [26], Serajzadehet al [27,28], Benasciutti et al [29] and Na et al [30], respectively.…”

A harmonic one-dimensional element for non-linear thermo-mechanical analysis of axisymmetric structures under asymmetric loads: The case of hot strip rolling

“…Despite its industrial application could be limited in so far as the rolling process must be simulated accurately, a 2D model proved to be useful to predict with sufficient precision the temperature evolution and the thermomechanical stress and strain in the roll, which can be used to assess its fatigue damage and service life. [17][18][19][20][21][22][23][24][25][26][27][28][29] The semi-analytical approach based on the 1D harmonic finite element discussed in the previous sections can thus be used to improve the numerical solution of the 2D model already used in Benasciutti and colleagues. 25,26 The results of thermo-mechanical transient analysis obtained by the 1D harmonic model will be compared to those obtained in Benasciutti and colleagues 25,26,[35][36][37] by a 2D model.…”

“…The second category includes 2D, or sometimes 3D, approaches that model only the work roll (but not the strip) subjected to surface thermal and mechanical loadings, which approximate the actual rolling conditions. [17][18][19][20][21][22][23][24][25][26][27][28][29] These models (especially 2D) were proposed to allow a strong reduction in the computational cost, although at the expense of some simplification. Without claiming to represent the hot rolling process accurately, these models have shown the capability to predict with sufficient precision the temperature distribution, 19,22,30,31 the work roll thermal expansion 18 and the thermomechanical stresses and strains, which are used to assess the roll fatigue life.…”

“…Without claiming to represent the hot rolling process accurately, these models have shown the capability to predict with sufficient precision the temperature distribution, 19,22,30,31 the work roll thermal expansion 18 and the thermomechanical stresses and strains, which are used to assess the roll fatigue life. 23,[25][26][27][28] Thanks to a strong reduction in the computational cost, these 2D models allow simulating the thermo-mechanical transient even for a huge number of roll rotations, in order to have an accurate mapping of the stress-strain time evolution that is absolutely crucial to perform a thermal fatigue life assessment. In fact, even a 2D model (with or without the strip) works well to predict the work roll service life because thermal fatigue damage (e.g.…”

“…[32][33][34] In turn, it has also been observed that circumferential and radial stresses are almost proportional to the surface temperature gradient in the roll, which then plays an important role in the analysis. 23,[25][26][27][28] For thermal fatigue damage assessment, it is most important to simulate the work roll response over a long rolling period, so that the calculated stress and strain are fully representative of the stabilized cyclic material behaviour. All things considered thus make a 2D model of only the work roll (without the strip) particularly useful because of its very low computational cost.…”