Abstract: An electron beam welding method capable of restoring toughness even when high heat input welding is performed. The electron beam welding method comprises: forming a first weld bead (3) so as to include a groove (2) provided at the butt portions of two base materials (1), and forming a second weld bead (4) and a third weld bead (5) having a narrower width than the first weld bead (3), at predetermined positions displaced from the groove (2) and centered symmetrically about the butt portions so as to include a portion of the first weld bead (3), using a lower heat input than that used during formation of the first weld bead (3).

Abstract: An object is to provide a heat transfer tube support structure capable of preventing deterioration of the reliability and the durability of a heat transfer tube. In a steam generator (heat exchanger) having a lower barrel (vessel), heat transfer tubes disposed in the lower barrel, and tube support plates disposed in the lower barrel and having heat transfer tube insertion holes opened in a thickness direction, support portions for supporting the heat transfer tubes are formed to the intermediate portions of the inner surfaces of the heat transfer tube insertion holes in the axial direction of the heat transfer tube insertion holes, and the regions between the support portions and the respective open ends of the heat transfer tube insertion holes are formed of inclined surfaces inclining in a radial direction outwardly in the heat transfer tube insertion holes toward the open ends, respectively.

Abstract: An electron beam welding method capable of restoring toughness even when high heat input welding is performed. The electron beam welding method comprises: forming a first weld bead (3) so as to include a groove (2) provided at the butt portions of two base materials (1), and forming a second weld bead (4) and a third weld bead (5) having a narrower width than the first weld bead (3), at predetermined positions displaced from the groove (2) and centered symmetrically about the butt portions so as to include a portion of the first weld bead (3), using a lower heat input than that used during formation of the first weld bead (3).

Abstract: An object is to provide a heat transfer tube support structure capable of preventing deterioration of the reliability and the durability of a heat transfer tube. In a steam generator (heat exchanger) having a lower barrel (vessel), heat transfer tubes disposed in the lower barrel, and tube support plates disposed in the lower barrel and having heat transfer tube insertion holes opened in a thickness direction, support portions for supporting the heat transfer tubes are formed to the intermediate portions of the inner surfaces of the heat transfer tube insertion holes in the axial direction of the heat transfer tube insertion holes, and the regions between the support portions and the respective open ends of the heat transfer tube insertion holes are formed of inclined surfaces inclining in a radial direction outwardly in the heat transfer tube insertion holes toward the open ends, respectively.