Met. litʹe Ukr., 2019, Tom 27, №10-12, P.47-55
L.V. Opryshko, Head of the Department for Materials Science, Expertise and Technologies for the Production of Tubes and Products from Ferrous and Non-Ferrous Metals and Alloys, Head of the Laboratory for Materials Science and Technologies for the Production of Tubes and Products for Thermal and Nuclear Power Engineering, e-mail: firstname.lastname@example.org
T.V. Golovniak, Head of the Sector for Expert Studies of Metal Products from Ferrous and Non-ferrous Metals and Alloys, e-mail: tatyana. email@example.com
State Enterprise “Ya.Ye. Osada Scientific Research Tube Institute” (State Enterprise “SRTI”), Dnipro, Ukraine
The article presents results of comprehensive studies of qualitative indicators of metal of the hot-rolled tube billets
manufactured by PJSC "Dneprovsky Iron & Steel Integrated Works" from continuously cast ingots of ‘20’ steel grade taken
from 2 heats of oxygen-converter smelting. The studies were performed according to current standards and methods. The
results of these studies have made it possible to assess ability of the production technology used at this enterprise to produce
high-quality tube billets for the manufacture of boiler tubes designed for steam boilers and pipelines operating at high and
supercritical steam parameters. It has been established, that the current steelmaking and casting technology used at the
Works does not fully ensure the manufacture of boiler tube billets in accordance with requirements of regulatory documents
and requires further study and improvement. Axial segregation and a light band (contour) were revealed in the macrostructure
of metal of the tube billets the degree of development of which exceeded the established norms, as well as unacceptable
edge point pollution. It was established that presence of the edge point pollution along with non-metallic inclusions in the
billet metal exceeding the established norms result in formation of unacceptable laminations in locations of the contaminants
expanded by rolling the tube metal.
Metal macrostructure of the hot-rolled tube billets under study features presence of cast structure residues negatively
affecting formation of the proper microstructure of metal of the boiler tubes manufactured from these billets and, accordingly,
the tube service properties. The necessity of increasing norms of sampling from hot-rolled continuously cast tube billets
manufactured by PJSC "Dneprovsky Iron & Steel Integrated Works" as well as the necessity of introducing requirements to
the degree of development of the cast structure residues observed in the metal macrostructure of these billets previously not
used in regulatory documents were shown.
The obtained study results are of great scientific and practical value. They have served as a basis for development of a
modern Technical Specification for hot-rolled carbon steel boiler tube billets manufactured by PJSC "Dneprovsky Iron & Steel
Integrated Works" as well as for working out and implementation of measures to improve the technology of production of
boiler tube billets at this enterprise taking into account requirements of the developed Technical Specification. This will allow
PJSC "Dneprovsky Iron & Steel Integrated Works" to produce competitive high-quality tube billets and reduce shortage of the
carbon steel tube billets in Ukraine.
Keywords: Continuously cast billet, boiler tube billet, macrostructure, axial segregation, point edge pollution, residues of cast structure, heat resistance, processing plasticity.
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