Study On Distribution Law Of Welding Residual Stress Of Tubesheet Of Nuclear Steam Generator

Sealing, structural strength, stress corrosion capacity and other performance of nuclear steam generator will be weaken by the welding residual stresses, and the safe operation of nuclear steam generator will disappear, so it is very meaningful to study the distribution law of welding residual stresses of tubesheet.Research objectives of this paper are surfacing layer of tubesheet and welding joint area of tubesheet-tube. Material of tubesheet is SA508 Gr.3Cl.2, and material of surfacing layer is Inconel690. Welding technology of surfacing layer is strip electrode electroslag surfacing, and the technology of tubesheet-tube is TIG.Firstly, the analysis of thermal-stress coupling in welding stress of surfacing layer of tubesheet is established by ANSYS. Double-ellipsoid & Elliptic-cylinder heat source realizes the quasi-steady-temperature of nodes of surfacing layer. The maximum residual stresses are in the core of welding layer, and residual stresses of nodes on lines which are parallel to weld center line are bigger in the middle than both ends. Residual stresses of nodes on lines which are perpendicular to the weld center line decrease gradually with the increasing distance.Secondly, residual stresses of panels of tubesheet and surfacing layer are testsd by the method of hole-drilling technique. The maximum residual stresses are in the core, and residual stresses of the middle part of longitudinal lines are bigger than both ends. The comparation of results of FEM and experiments shows that two methods all conclude the same distribution law of welding residual stress of tubesheet which proves method of FEM is available in the welding simulation.Finally, apply the FEM to the residual stresses simulation of joint area of tubesheet-tube. Double-ellipsoid heat source realizes the quasi-steady-temperature of nodes of welded joint. The influence of welded joint is in limited areas, and the axial residual stress of inner and outter surface of tube is opposite. It is concluded that methods to reduce the residual stresses are to decrease the welding current and increase the welding speed.