Cooling pattern on the run-out table of a hot rolling mill for an HSLA steel: a finite element analysis

The cooling process of a hot rolled strip on the run-out table (ROT) mainly determines the microstructure and mechanical properties of the final product; therefore, a method of investigation that helps companies follow the optimum cooling scenario is a profound issue. This paper develops a 2D finite element model based on industrial data that predicts the cooling pattern of hot rolled strips, with the potential to be formulated for steel grades dealing with complex boundary conditions, flexible to be applied for any cooling table. Meanwhile, this model investigates the thermal behavior of strips facing different heat transfer mechanisms in the full-scale ROT of Mobarakeh Steel Company (MSC). Moreover, coiling temperature (CT) and cooling pattern are validated through experimental data obtained from the Evraz hot rolling mill. Regarding the simulation of various header configurations, each four-header bottom bank, upper laminar, and water curtain headers deliver 10 \(^\circ{\rm C} /{\text{s}}\) ${}^{\circ }\mathrm{C}/\text{s}$ , 10.66 \(\mathrm{^\circ{\rm C} }/{\text{s}}\) ${}^{\circ }\mathrm{C}/\text{s}$ , and 7.85 \(\mathrm{^\circ{\rm C} }/{\text{s}}\) ${}^{\circ }\mathrm{C}/\text{s}$ of cooling rate, respectively. The simulations also predict the heat flux in the impingement, parallel, and air-cooling zones to be in the range of 4000–12,000, 500–2500, and 80–400 \(({\text{w}}/{{\text{m}}}^{2}{\text{K}})\) $(\text{w}/{\text{m}}^2\text{K})$ on the top surface, and 21,000–5400, 700–4200, and 380–170 \(({\text{w}}/{{\text{m}}}^{2}{\text{K}})\) $(\text{w}/{\text{m}}^2\text{K})$ on the bottom surface, respectively. According to the temperature-dependent attitude of steel properties, the effect of strip’s thermo-physical properties on the heat transfer along ROT was examined, illustrating the significant impact of specific heat on cooling, which leads to the endorsement of the functionality of early cooling compared to delayed and distributed strategies for the investigated HSLA (high-strength low-alloy) steel.