Volgograd State Technical University, Volgograd, Russia
L. V. Palatkina, Cand. Eng., Associate Prof., Dept. of Technology of Materials, e-mail: lv.palatkina@yandex.ru
V. V. Galagan, Master's Student, Dept. of Technology of Materials, e-mail: galaghan@list.ru
M. V. Matasova, Master's Student, Dept. of Technology of Materials, e-mail: matasova.mary2016@mail.ru

Volzhsky Pipe Plant, Volzhsky, Russia
M. Yu. Chubukov, Cand. Eng., Deputy Head of the Central Plant Laboratory, e-mail: chubukovmu@vtz.ru

Based on computer simulation, a pseudobinary diagram was constructed for steel 26KhGMF, in accordance with which (based on the results of recent publications devoted to in situ observations of the peritectic reaction and peritectic transformation), the phase-structural mechanisms of its crystallization were refined. It has been established that during solidification of a continuously cast billet Ø260 mm from 26KhGMF steel, a zone structure of dendritic crystals (typical for continuous casting) is formed in its volume, while electromagnetic mixing (EMM) of
the melt ensures the almost complete absence of physical inhomogeneity in the thermal center. Based on a qualitative analysis of the microchemical inhomogeneity of the distribution of silicon, an appearance appears, which manifests itself during EMF of the melt, the effect of increasing the solidification rate is enhanced in dendritic crystals on the effect of peritectic transformation of the uneven supply of elements (over the cross section of austenite layers of different input), which occurs when solid-phase transformations occur. It is also shown that the dendrites of the environment are manifested by external manifestations of color, which characterize microsegregation zones with a different presence of silicon in them. To clarify the nature of the formation of shells, it was suggested that their crystallization nature is due to the presence of excitedly active impurities in the melt, which have an increased sensitivity according to Gibbs. A developed analysis showed the presence of a sufficient amount of a substance, which showed that the concentration of highly active impurities (As, Sb, Sn, Pb, Zn and Bi) is more than 0.02 %, which can lead to the formation of silicon shells during electromagnetic ignition of the melt. Fused EMF micro-induced volume discontinuities in "dendrite" and "interbranch" are inherited by the finished product (and sulfide stress corrosion cracking resistance of casing pipes to sulfide stress corrosion cracking) zones.

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