National University of Science and Technology “MISiS” (Moscow, Russia)

V. A. Dub, Cand. Eng., Leading Expert, the Chair of Physical Chemistry

RF State Research Centre JSC SPA “CNIITMASH” (Moscow, Russia)
S. V. Novikov, Cand. Eng., Scientific Researcher, Electric Melting Lab.
I. A. Shchepkin, Dr. Eng., Leading Scientific Researcher, Electric Melting Lab.

Ural State Federal University n. a. the 1st RF President B. N. Eltsin (Ekaterinburg, Russia)
O. Yu. Kornienko, Cand. Eng., Associate Prof., the Chair of Heat Treatment and Metal Physics, o.j.kornienko@urfu.ru

A. P. Kulikov, V. A. Tsarev, V. A. Novikov and D. S. Tolstykh participated in this research.

The ways of increase of the power engineering products resource for large-size critical components made of steel 15Kh2NMFA are described in terms of radiation and thermal brittleness criteria due to the content restriction of harmful and impurity elements, primarily phosphorus, sulfur and hydrogen. The steelmaking process for this steel grade includes smelting of liquid semiproduct in the electric arc furnace DSP-120, secondary refining process and ladle-vacuum treatment. The main technological task in melting of this semiproduct is obtaining of a final phosphorus content not more than 0.003% using deep dephosphorization process. For this purpose solid carburizers in the charge, such as pig iron and coke, are replaced by pulverized carbon-containing materials, blowing-in with oxygen or adding to slag during oxidizing period. In order to organize the process of deep desulfurization simultaneously with the removal of hydrogen, it is necessary to obtain the optimal slag composition in the required amount and high deoxidation of the metal before ladle vacuum treatment. Deep bulk deoxidation was carried out immediately during discharge of liquid semiproduct out of the electric arc furnace. Regulated content of the following elements was obtained as a result of usage of these methods: phosphorus 0.003–0.004%, sulfur 0.001–0.002%, hydrogen 0.8–1.1 ppm, oxygen activity 3–5 ppm.

The study was financially supported by Ministry of Education and Science of the Russian Federation within the scope of accomplishment of the Federal Targeted Program “Investigations and innovations on priority development directions of the RF scientific–technological complex for 2014–2020 (application code “2015–14–579–0173–366”). Agreement of subsidizing No. 14.578.21.0114 dated October 27. 2015. Unique identifier of applied scientific researches and experimental development (PNIER) — RFMEFI57815X0114.

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