National Research Center "Kurchatov Institute" – Prometey Central Scientific Research Institute of Structural Materials, St. Petersburg, Russia

E. I. Khlusova, Dr. Eng., Prof., Deputy Head of the Scientific and Production Complex, Head of Laboratory
O. V. Sych, Dr. Eng., Head of Sector, e-mail: npk3@crism.ru
A. V. Ilyin, Dr. Eng., Deputy General Director – Head of Scientific and Production Complex
S. V. Korotovskaya, Cand. Eng., Head of Sector
N. S. Novoskoltsev, Leading Engineer

Currently, in the Russian Federation, technologies have been developed and pilot-scale industrial production has been carried out at metallurgical plants to manufacture structural steels offering high cold resistance in thicknesses up to 80 mm, as well as guaranteed crack resistance in thicknesses up to 50 mm. However, for large-scale development of the Arctic region, steels with thicknesses of up to 150 mm are required. This work presents the structures of 80–150 mm thick plate produced from shipbuilding steels with a guaranteed yield strength ranging from 315 to 690 MPa by means of normalization, thermomechanical processing, and quenching from rolling heat followed by tempering. The study includes results on the determination of mechanical properties, critical temperatures for the transition to a brittle state, and crack resistance of 80–150 mm thick plate from shipbuilding steel grades. The fracture surfaces of specimens tested under impact bending at low temperatures were analyzed. Criteria are proposed for assessing the quality of thick plate, ensuring its reliability under low-temperature conditions. The research revealed that the formation of pronounced structural heterogeneity—primarily related to variations in austenite grain size and the presence of extended regions of bainite with a lath morphology exceeding 100 μm—is the main factor leading to increased anisotropy of mechanical properties, as well as reduced cold resistance and crack resistance in thick-plate lowcarbon shipbuilding steels, regardless of the alloying level (strength grade) or manufacturing process.

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