The paper presents a model and an algorithm for calculating the operational properties of a metal and a structure after its assembly-welding. The model is based on the equations of non-stationary thermal conductivity and mechanical equilibrium, as well as the analysis of structural-phase transformations using thermokinetic diagrams. It is implemented in the original BAZIS software package. Validation of software was carried out when calculating thermal fields and deformations as applied to arc welding, arc deposition, and laser welding of standard joints.