Effect of thermal cycle of welding and reheating on structural-constitutional changes of low-alloyed <i>Cr</i>-<i>Ni</i>-<i>Mo</i>-<i>V</i> steel

Abstract

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 - fluctuation, 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.

Keywords

• 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
• свариваемость
• низколегированная сталь
• зона термического влияния
• погонная энергия сварки
• термический цикл сварки
• металлографическое исследование
• крупнозернистая структура зтв
• выпадение фаз по границам зерен
• термическая обработка
• дисперсионное твердение
• трещины при термической обработке