The Paton Welding Journal, 2021, №10



2021 №10 (01)

DOI of Article 10.37434/tpwj2021.10.02

2021 №10 (03)

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The Paton Welding Journal, 2021, #10, 11-17 pages

Structural inhomogeneity in welded joints of heat-resistant steels of chromium-molybdenum-vanadium system with different chromium content

M.O. Nimko, V.Yu. Skulskyi, A.R. Gavryk, S.I. Moravetskyi and I.G. Osypenko

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

Abstract
Welded joints of dissimilar steels are widely used in different assemblies of the steam-water mixture loop in electric power plants. Difference in alloying by chromium and other carbide-forming elements results in carbon migration from the lower alloyed to the higher alloyed steel in such joints after tempering and in high-temperature service. Decarbonization in the HAZ near-weld zone of the lower alloyed steel can lead to formation of defects and subsequent failures. In this work we studied the influence of the type of 15Kh2M2FBS steel joint (single-pass, multipass), made using electrodes with 9 % Cr, on the nature of formation and development of structural inhomogeneity in the HAZ at high-temperature annealing. It is shown that depending on joint type, development of ferrite interlayer takes place in different zones of the HAZ: in the normalized zone and in the zone of intercritical temperatures АС1–АС3 at a distance from the fusion line at single-pass welding; and in the near-weld zone through the HAZ coarse-grained region at multipass welding. Proceeding from the features of decarbonizastion on the surfaces of butt joints and near the fusion line, a scheme was proposed, that allows explaining the nature of development of structural inhomogeneity in the multipass joint of dissimilar steels.
Keywords: carbon diffusion, dissimilar steel joints, heat-affected zone, decarbonized interlayer

Received: 22.07.2021
Accepted: 11.11.2021

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