Nosov Magnitogorsk State Technical University (Magnitogorsk, Russia):

M. V. Chukin, Dr. Eng., Prof., Head of the Chair of Material Processing Technology, First Vice-Rector on Science and Innovations, e-mail: m.chukin@mail.ru
P. P. Poletskov, Dr. Eng., Prof., the Chair of Material Processing Technology, e-mail: pavel_poletskov@mail.ru
O. A. Nikitenko, Cand. Eng., Research Assistant, e-mail: olganikitenko@list.ru
D. G. Nabatchikov, Cand. Eng., Research Assistant, e-mail: nabat4ikov@mail.ru

The work has been conducted with participation of S. V. Denisov, P. A. Stekanov, E. V. Braichev, N. V. Koptseva, Yu. Yu. Efimova, M. S. Gushchina, A. S. Ishimov, M. S. Zherebtsov, D. M. Chukin.

The results of investigations of microstructure and properties of heavy plates made of cold-resistant pipe steel are presented. The series of laboratorial melting experiments on low-carbon steel has been undertaken in the conditions of “Termodeform-MGTU” researching complex with variation of content of alloying elements. Physical simulation of controlled rolling with accelerated cooling according to different procedures has been conducted during this work. Mechanical testing of rolled products have been conducted according to the standard techniques with determination of strength and cold resistance (amount of tough component in the fracture of samples for drop weight tear testing (DWTT) at the temperature –55 °С. The complex of metallograhic investigations has been undertaken in the Centre of collective use (TsKP) of the Scientific and research institute of Nanosteels at Nosov Magnitogorsk State Technical University. Rolled microstructure has been investigated by the methods of optical and scanning electron microscopy. It was revealed that forming of the mixture containing acicular ferrite, polygonal (polyhedral) ferrite and quasi-polygonal ferrite is the optimal way with relation to providing of high cold resistance (> 90 % of tough component in the fracture of samples for DWTT). It was noted that presence in microstructure of essential part of bainite with different morphology forming along the boundaries of large austenite grains leads to deterioration of the properties of rolled material during drop weight tear testing.

The study was financially supported by Ministry of Education and Science of the Russian Federation within the scope of accomplishment of multiple-purpose project on creation of modern high-tech production with the participation of higher education institution (Contract 03.G25.31.0235).

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