Heat treatment is the most common method to modify the mechanical properties in steel automotive workpieces, through heating and cooling processes. Depending of the heat treatment or stage we can have different values of heat transfer coefficient (HTC). For the thermometallurgical calculations, the most important boundary condition is the HTC, which can be obtained by a trial-and-error approach, inverse mathematical techniques, or computational fluid dynamics.

In this paper the application of computational fluid dynamics (CFD) in the calculation of the HTC values for natural convection phenomena was used. These measurements were obtained in austenitizing stage, annealing, normalizing and quenching processes, the specimen was a structural steel channel beam. The simulation was developed in Ansys Fluent. The incompressible-ideal gas model was used for the buoyancy effect generated by the internal heat source in the flow field. The two-equation k-ω based SST (Shear Stress Transport) turbulence model was used to mould the turbulent stresses in the Reynolds-Average Navier-Stokes equations (RANS).

The results demonstrated that CFD simulation is a powerful tool to calculate HTC in transitory states. The feasibility and precision of CFD calculations in each external fluid condition was demonstrated. A good correlation between the gotten results and similar previous works in the literature was confirmed.