Abstract
In this paper, the effect of repair welding heat input on microstructure, residual stresses, and stress corrosion cracking (SCC) sensitivity were investigated by simulation and experiment. The results show that heat input influences the microstructure, residual stresses, and SCC behavior. With the increase of heat input, both the δ-ferrite in weld and the average grain width decrease slightly, while the austenite grain size in the heat affected zone (HAZ) is slightly increased. The predicted repair welding residual stresses by simulation have good agreement with that by X-ray diffraction (XRD). The transverse residual stresses in the weld and HAZ are gradually decreased as the increases of heat input. The higher heat input can enhance the tensile strength and elongation of repaired joint. When the heat input was increased by 33%, the SCC sensitivity index was decreased by more than 60%. The macroscopic cracks are easily generated in HAZ for the smaller heat input, leading to the smaller tensile strength and elongation. The larger heat input is recommended in the repair welding in 304 stainless steel.
Highlights
Repair welding is the most important means to repair the defects of aging pressure vessel and piping components, and is used for life extension [1]
Because of non-uniform heating and cooling during repair welding, the inhomogeneous plastic deformation and residual stresses are generated in the repair zone, which is the weakest area of the repaired structure [2]
The aim of this study is to study the effects of repair welding technology on microstructure, residual stresses, and stress corrosion cracking (SCC) behavior of repair welded joint, which will be of great significance for prolonging the service life of the repair welded equipment
Summary
Repair welding is the most important means to repair the defects of aging pressure vessel and piping components, and is used for life extension [1]. Because of non-uniform heating and cooling during repair welding, the inhomogeneous plastic deformation and residual stresses are generated in the repair zone, which is the weakest area of the repaired structure [2]. The effects of repair residual stresses on structure integrity are greater than that of initial weld residual stresses [8]. During corrosive environment, stress corrosion cracking (SCC) phenomena occur in the repaired zone. An improved understanding of the effect of repair welding on residual stresses and SCC behavior becomes critically important for performing structural integrity assessment of repaired equipment
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