This paper deals with the use of mixte 3D F.E. to simulate heat treatment processes. A complete thermo-elasto-visco-plastic THEVP constitutive equation is chosen to cover a large domain of deformation (Colonna et al.), from purely viscoplastic at high temperature to elastic at the end of the heat treatment process, with non linear kinematic/isotropic hardening laws. A 3D mixte finite element (velocity/pressure) is used with the same interpolation for mechanical and thermal discretisation. This formulation is based on the mini-element formulation for linear and non linear cases, with stabilized element in order to satisfy the compatibility conditions (Arnold et al.).