Numerical Modelling of Heat Treatment : Fluid Flow-Thermal-Metallurgical-Mechanical Couplings

Numerical simulation is today a necessary tool in order to better optimize heat treatments as far as microstructures, mechanical properties and residual stresses and distortions are concerned. These simulations need the modelling of the material behaviour, and the « process » modelling (heating, cooling…) as well as to take into account the couplings between the different phenomena. Today, one key issue remains the prediction of the heat transfer between the solid and its environment. Thus, in that study, we will focus on the development of a numerical model that couples fluid flow, thermal, metallurgical and mechanical calculations and its experimental validation. Two cases are chosen : on one hand the modelling of high pressure gas quenching and on the other hand the modelling of the heating process in a furnace. First the numerical model is presented. Then, the validation experiments are described. On one hand, original gas quenching experiments have been performed by measuring in-situ gas velocities (by Particle Image Velocimetry), temperatures and deformations (by contour’s detection method with CCD camera). On the other hand, a specific experimental device has been set up in order to measure in-situ the temperature evolutions and the bending of a steel tube during heterogeneous heating in a furnace. From the simulated results, the respective effects of the thermal gradients and the phase transformations on the deformations of the steel pieces during heating and during quenching are analysed. It will be shown also that the simulated results agree fairly well with the measurements.