A model for high carbon steel phase transformation and cooling behavior on run-out table of hot strip mill

A model was developed considering non-symmetric cooling in the thickness direction of strip on a run-out table of hot strip mill. In order to solve the one-dimensional transient heat transfer equation, including the heat evolved from phase transformation, a finite element method coupled with thermodynamic and kinetic analyses were employed. The heat capacity of each phase and the heat evolution due to phase transformation were obtained by thermodynamic analysis of the Fe-C-Mn system using a sublattice model. The phase transformation kinetics of high carbon steels was derived using continuous cooling experiments and thermodynamic analysis. By applying an inverse method, the hat transfer coefficients of the strips on the run-our table were determined from actual mill data under various cooling conditions. Using the developed model, the temperature-time variations of high carbon steels on the run-out table were calculated. The results calculated were in good agreement with the actual mill data. In addition, the quantitative phase evolution during cooling on the run-out table could also be predicted by the model. From this analysis, it was possible to design an optimum cooling pattern on the run-out table ensuring a desirable microstructure: of high carbon steel and a stable cooling operation.