Finite element analysis of effect of layers on residual stress and deformation in butt-welded ultra-thick tube-sheet

Butt-welding residual stress and deformation of 390 mm 20MnMoNb ultra-thick plates for manufacturing the tube sheet of a large scale EO (Ethylene Oxide) reactor were simulated by using finite element program ABAQUS. The effect of layers on the residual stress and deformation was discussed. The welding grove was double U-shaped which were welded alternatively by flipping over the tube sheet. Moreover, in order to avoid the excessive deformation of the tube-sheet, two 4500 kN loads were applied on both ends of the tube-sheet. The results showd that angular deformation occurred in the tube-sheet. A large tensile residual stress was generated in the weld seam, the heat affected the zone near the surfaces of the tube-sheet, and compressive residual stress was generated in the weld root. As the layers increased, the deformation increased, however the stress decreased (which wass not significant). The result proves that it is not an effective method to decrease the residual stress by increasing the layer number for such ultra-thick plates.