Volgograd State Technical University (Volgograd, Russia):

M. Yu. Chubukov, Post-graduate
D. V. Rutskiy, Cand. Eng., Associate Prof.
N. A. Zyuban, Dr. Eng., Prof., Head of the Chair “Technology of Materials”, e-mail: tecmat@vstu.ru

Peter the Great St. Petersburg Polytechnical University (St. Petersburg, Russia):
S. V. Ryaboshuk, Assistant

The results of a study of the specific features of the influence of the chemical composition of steels on the hot plasticity of a solidcast continuous-cast ingot for the production of seamless pipes are presented. Complex modeling was carried out, which consisted in thermo-mechanical modeling (Gleeble 3800) of the behavior of the solidifying cortical layer of continuous-cast ingot during continuous casting and the study of the thermo-time nature of the separation of phase components during solidification of continuous-cast ingot with different chemical composition. As a result of thermo-mechanical modeling, it was established that all steels have a region of reduced plasticity in the temperature range of 800–1000 °C. The minimum level of hot plasticity for all steels is noted at a temperature of 900 °C. The level of strength characteristics according to the results of physical modeling of the behavior of a solid crust of continuous-cast ingot from steels with various doping schemes in the entire investigated range (700-1300 °C) differs towards higher values of temporal resistance and yield strength for low carbon steels with additives micro-alloying elements. According to the results of comparing the results of modeling - the thermo-mechanical modeling and the thermal nature of the separation of phase components – it was established that a decrease in plasticity in the range of 800–1000 °C is associated with the release of complex nitride and carbonitride phases. In particular, when considering the obtained dependences in detail, for steels without microalloying, an increase in the mass fraction of aluminum nitrides is noted, and for steels with microalloying, an increase in the mass fraction of complex carbide and carbonitride phases based on niobium is noted along with a decrease in the relative narrowing values. In addition, in steels, micro-niobium, there is a tendency to increase the level of strength characteristics. The most optimal level of strength and plastic characteristics is noted for steel with the lowest carbon content and a complex of micro-alloying elements.
The study was financially supported by the Russian Foundation for Basic Research. Project № 18-08-00050.

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