Laser hardening is a very flexible and useful process for surface treatment of medium carbon steels, capable of processing varied and complex geometries. In order to enlarge the range of industrial applications to which this process can be applied, a suitable model is necessary in order to reduce the setup time requested for the optimization of new components. The process model presented is based on the Arrhenius-like equation for estimation of the thermally induced process reaction time for microstructural transformations. By means of experiments, all unknown parameters in the equations have been determined, highlighting the accuracy and low computation time of the simulator.