This thesis investigates and models the austenite to ferrite transformation in the hot rolling of two different dual phase steels. The investigation has been carried out in a deformation dilatometer as well as a 4-stand pilot rolling mill. Three different modelling approaches were employed to give different aspects of information and for different applications. Macroscopic kinetics model base on JMAK rate form gives simple overall kinetics information and indicates the appropriate process window as a function of temperature on the Run Out Table and the degree of deformation in the nonrecrystallisation region. Thermodynamics model show the effect of chemical composition on critical temperatures and therefore on the processing temperature window. Phase field yields the microstructure evolution in details, namely, ferrite grain size distribution and phase fraction as well as the diffusion profile in the remaining austenite. It supports the information for the finding of significant amount of retained austenite and the strong carbon gradient found by field emission electron microprobe.
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