A model and an algorithm for calculating the stress-strain state of a structure after its assembling and welding are presented in the paper. The model is based on the equations of non-stationary heat conduction and mechanical equilibrium, taking into account structural-phase transformations. It is implemented in the original software package BAZIS. The calculations of thermal fields and deformations were carried out in the BAZIS in relation to arc welding, surfacing and laser welding. The simulation accuracy was evaluated in comparison with experimental data and the simulation results in the widely used foreign CAE software complexes Simufact (Germany), SYSWeld (France).