The work objective is to study the impact of the thermal welding cycle (TWC) and reheating on the metal embrittlement kinetics of the heat affected zone (HAZ) of 15H2NMFA-VRV steel joint welds. The problem of the technological strength improvement of the welded joints of the nuclear power plant equipment is solved. A comprehensive study, in which various types of analysis – fluctua-tion, metallographic, electron-microscopic, X-ray and chemical – are used, is carried out for this. In addition, HAZ metal simulation is used, as well as non-destructive and destructive testing of welded joints. The effect of the basic parameters of TWC and heat treatment on the embrittlement kinetics of HAZ metal is determined. It is shown that the high heat input under the electroslag welding is the main cause of the direct borders softening of the coarse grains (0-1) through allocating sulfide film forms. Further development of the dispersion hardening under reheating (softening) stimulates the relative weakening and borders destruction.
weldability, low-alloyed steel, heat affected zone (HAZ), rate of heat input, thermal welding cycle, metallographic test, coarse-grained structure of HAZ, grain boundary precipitation, thermal treatment, dispersion hardening, reheat cracking.
Для изготовления оборудования и трубопроводов атомных энергетических установок используют термически упрочняемые стали перлитного класса различных систем легирования:
— Ni-Mn-Mo (533 cl1, 20MnMoNi55, 10ГН2МФА),
— Cr-Mo-V (15Х2МФА),
— Cr-Ni-Mo (508 cl2),
— Cr-Ni-Mo-V (15Х2НМФА) [1, 2].
С целью повышения эксплуатационной надежности сварных соединений рекомендуют использовать чистые стали, выплавленные вакуумно-индукционным методом [1], а также на чистой шихте и дополнительно подвергнутые электрошлаковому переплаву (ЭШП) [2, 3] или внепечному рафинированию и вакуумированию (ВРВ) [4, 5].
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