Electrometallurgy Today, 2025, №04

2025 №04 (05)

DOI of Article 10.37434/sem2025.04.06

2025 №04 (07)

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"Suchasna Elektrometallurgiya" (Electrometallurgy Today), 2025, #4, 37-42 pages

Segregation in a steel ingot and possibilities for its lowering

F.K. Biktagirov, K.B. Zlygoriev

E.O. Paton Electric Welding Institute of the NAS of Ukraine 11 Kazymyr Malevych Str., 03150, Kyiv, Ukraine. E-mail: biktagirfk@ukr.net

Abstract
The problem of chemical macroheterogeneity in steel ingots is considered, which is caused by redistribution (segregation) of elements dissolved in iron, between the solid and liquid phases during metal solidification. It is determined that carbon, sulphur and phosphorus are the most prone to segregation. Their accumulation leads to formation of the general and local forms of chemical macroheterogeneity. Two main hypotheses are considered as to the mechanism of formation of the axial (V-shaped) and off-center (A-shaped) defects of chemical heterogeneity and the role of the two-phase zone of their development. Increased content of healing additives in the defective zones creates a risk of premature failure or even breaking up of the product made from the ingot. Results of studying a roll from 70Kh3GNMF steel are given, which confirm that positive segregation is observed in a 48 ton ingot from which the roll was made, with exceeding the admissible carbon content in individual zones. Also noted is the manifestation of V-shaped and A-shaped defects, where sulphur content is 2...5 times higher. Traditional and modern technological means of preventing the macrosegregation are considered: reduction of impurities, multipouring, as well as hot-top pulsed magnetic oscillation (HPMO) and electroslag heating and stirring (ESHS). It is shown that forced convection of the melt inside the ingot promotes reducing the extent of the two-phase zone, homogenizing of the composition and potential lowering of chemical macroheterogeneity. The authors emphasize that application of the methods of external influence, in particular, ESHS method, allows not only eliminating the shrinkage defects, but also enhancing the chemical homogeneity of steel, and it is indicative of the good prospects for its application to improve the quality of the steel ingots. 22 Ref., 2 Tabl., 4 Fig.
Keywords: steel ingot, segregation, chemical macroheterogeneity, defects, external influence, metal heating and stirring

Received: 01.10.2025
Received in revised form: 11.12.2025
Accepted: 22.12.2025

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