A study was made of the dependence of the viscosity characteristics of ShKh15 steel melts on the out-of-furnace treatment regimes. It was found that the main technological operations, such as deoxidation and scavenging of the metal with argon, have a noticeable effect on the viscosity of the melts. The viscous flow activation energies are calculated. It is shown that variations in the activation energy during out-of-furnace treatment correlate with viscosity variations.