Avtomaticheskaya Svarka (Automatic Welding), #9, 2019, pp. 14-25
Effect of cooling cycle of welding on structure-phase composition of 15Kh2NMFA steel
O.V. Makhnenko, V.A. Kostin, V.V. Zhukov, E.S. Kostenevich
E.O. Paton Electric Welding Institute of the NAS of Ukraine. 11 Kazimir Malevich Str., 03150, Kyiv, Ukraine.
In the recent years mathematical methods are widely used for prediction of microstructure phase composition of structural steels under thermal effect. Using mathematical modelling based on existing parametric regression equations there was carried out prediction of microstructure phase transformations in HAZ metal of base material (steel 15Kh2NMFA) of WWER-1000 reactor vessel in arc surfacing of protective corrosion resistant layer as well as performed comparative analysis of modelling results with obtained experimental data of dilatometric and metallographic analysis. The comparison of results ensures formation of bainite-martensite structure in HAZ metal of WWER-1000 reactor vessel, however value of content of martensite in calculation and experimental determination is significantly different. For calculation determination of content of structural constituents it is necessary to use the experimental CCT diagrams of austenite decay for characteristic welding/surfacing thermal cycles, which do not have long-term heating or holding at austenitizing temperature and cooling takes place with variable rate. CCT diagrams of undercooled austenite for typical cooling rates 3-5 °C and two maximum temperatures of thermal cycle, namely 1000 and 1350 °C were experimentally plotted for adequate evaluation of mictrostructure composition in HAZ of vessel steel 15Kh1NMFA in welding/surfacing. Obtained results can be used in calculation determination of residual stresses in WWER-1000 vessel body for grounding the extension of safe operation life. 32 Ref., 7 Tabl., 13 Fig.
WWER-1000 reactor vessel, steel 15Kh2NMFA, corrosion resistant surfacing, microstructure transformations, mathematical modelling, dilatometry
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