Abstract Hot deformation and cooling together with the chemical composition define the final mechanical properties of the steel product. In order to control and optimize the desired properties, quantitative models are needed. In this article we present our phase transformation model, which has been fitted to experimental continuous cooling data and coupled to our own heat conduction computer simulation software. The fitting of the model to experimental data enables accurate modeling. The coupled heat transfer and conduction models allow the simulation of non-uniform cooling rates and temperature distribution. The development of our own software enables full control and easy linking of the models in order to use them in modeling and optimizing cooling procedures. The presented phase transformation model also provides information on the onset and kinetics, which can be used in more detailed microstructure models. The transformation model can also be introduced in other simulation softwares as a subroutine.