Electrometallurgy Today, 2022, №01



2022 №01 (02)

DOI of Article 10.37434/sem2022.01.03

2022 №01 (04)

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Electrometallurgy Today (Sovremennaya Elektrometallurgiya), 2022, #1, 24-33 pages

Formation of the zone of joining the layers in a composite ingot, surfaced by the electroslag process with liquid metal, for power turbine rotors

G.O. Polishko, G.P. Stovpchenko, V.A. Kostin, A.Yu. Tunik, L.O. Lisova, L.B. Medovar

E.O. Paton Electric Welding Institute of the NAS of Ukraine. 11 Kazymyr Malevych Str., Kyiv, 03150, Ukraine. E-mail: office@paton.kiev.ua

Abstract
The paper describes the possibilities for application of ESP with liquid metal for producing round steel ingots dissimilar along their height (length) with a minimized zone of mixing of different steels by regulated pouring of liquid metal of the specified chemical composition into the current-conducting mould. The extent, composition and structure of the thus formed transition zone were studied. Thermodynamic analysis of phase stability diagrams for Fe‒C‒Cr subsystem was used as the base to determine the heat treatment mode to avoid formation of critical defects in the metal structure of the joint of a composite ingot from 38KhN3MFA and 12Kh13 steels. It was established that in the steel joint zone formation of a structure with an acceptable hardness level is ensured at up to 0.9 °C/s cooling rate in the electroslag process with liquid metal that guarantees absence of the risk of cold cracking or fracture. Metallographic studies of the microstructure in the joint zone of composite ingot samples after heat treatments (HT1 and HT2) showed that in both the cases this zone has the structure of fine lamellar tempered martensite with a more uniform grain size that that without heat treatment. Ref. 13, Table 1, Fig. 12.
Keywords: electroslag process with liquid metal (ESP LM); composite ingot; joint zone; thermokinetic diagrams; heat treatment; microhardness; grain size

Received 17.01.2022

References

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