The construction of a geometric model and finite element approximation of the flange of a stationary power plant is presented. Modelling and meshing were held using Salome-Meca modules. The paper provides a brief description of the key commands in AsterStudy module for modeling this problem. A numerical calculation of the heat-stress state of the flange of a stationary power plant was performed using free Code Aster software. Distributions of temperature for four periods, flange deformation, displacements, and also equivalent von Mises stresses are given as a results of the study.