2021 №10 (01) DOI of Article
2021 №10 (03)

Automatic Welding 2021 #10
Avtomaticheskaya Svarka (Automatic Welding), #10, 2021, pp. 12-18

Structural inhomogeneity in welded joints of heat-resistant steels of chromium-molybdenum-vanadium

M.O. Nimko, V.Y. Skulskyi, A.R. Gavrik, S.I. Moravetskyi, I.G. Osipenko
E.O. Paton Electric Welding Institute of the NAS of Ukraine. 11 Kazymyr Malevych Str., 03150, Kyiv, Ukraine. E-mail: office@paton.kiev.ua

Welded joints of dissimilar steels are widely used in different assemblies of the steam-water mixture loop in electric power plants. The difference in alloying by chromium and other carbide-forming elements results in carbon migration from the lower alloyed to higher alloyed steel in such joints after tempering and in high-temperature service. Decarbonization in the HAZ near-weld zone can lead to formation of defects and subsequent failures. In this work we studied the infl uence 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 inhomogneneity in the multipass joint of dissimilar steels. 17 Ref., 11 Fig.
Keywords: carbon diffusion, dissimilar steel joints, heat-affected zone, decarbonized interlayer

Received: 22.07.2021


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