Nosov Magnitogorsk State Technical University (Magnitogorsk, Russia)

A. S. Kuznetsova, Cand. Eng., Associate Prof., Engineering Center, allakuznetsova.mgtu@mail.ru
P. P. Poletskov, Dr. Eng., Prof., Dept. of Metal Processing Technology
N. V. Koptseva, Dr. Eng., Prof., Dept. of Casting Processes and Materials Science
Yu. Yu. Efimova, Cand. Eng., Associate Prof., Dept. of Casting Processes and Materials Science
D. Yu. Alekseev, Cand. Eng., Associate Prof., Engineering Center
A. E. Gulin, Cand. Eng., Associate Prof., Engineering Center

The paper presents the results of examination of the structure and properties of low-alloy steel, which is aimed on manufacturing coiled tubing for Arctic application, depending on different parameters of thermomechanical treatment. Based on the data about structural and phase transformations of overcooled austenite in steel, the temperature and speed processing indicators were selected and realized in the reversed hot rolling mill DUO-500, which is combined with the accelerated cooling system. These indicators meet the requirements of API Specification 5ST for the steel with ST80 strength class within the defined range (from 190 HV / 90 HRB to 240 HV / 99 HRB). The processing parameters, which ensure forming of fine-dispersed ferrite-bainite steel structure and thus achieving the highest level of tough and ductile properties at the preset strength level, were established.

The research was carried out in the Nosov Magnitogorsk State Technical University on the expense of the grant of Russian scientific fund No. 25-29-20085 dated 14.05.2025, as well as on the expense of remedies of the Ministry of Education and Science of the Chelyabinsk region (Agreement No. 30-2025-002767 dated 07.07.2025), https://rscf.ru/project/25-29-20085/.

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