Abstract: A joint method includes a groove formation step of removing part of a first projection and part of the second projection to form a groove region between the first projection and the second projection, a first welding step of joining a first member and a second member to each other by butt welding, and a second welding step of filling the groove region by buildup welding. The groove formation step forms a first inclined surface in the first projection facing the groove region to be gradually distant from a joint position joined with the second projection so as to be closer to an outer surface of the first projection, and forms a second inclined surface in the second projection facing the groove region to be gradually distant from the joint position joined with the first projection so as to be closer to an outer surface of the second projection.

Abstract: Irradiation with a laser beam is performed along a welding bead, while the laser beam is aimed, as an irradiation point of the laser beam, at a contact point between a deck plate and a U-rib that is contained in a non-welded portion of a root part, from a side of the welding bead of the root part. Thereby, it is possible to remove a crack beginning at the non-welded portion of the root part generated at a joining portion between the deck plate and the U-rib of a steel floor slab, by the irradiation with the laser beam.

Abstract: A joint method includes a groove formation step of removing part of a first projection and part of the second projection to form a groove region between the first projection and the second projection, a first welding step of joining a first member and a second member to each other by butt welding, and a second welding step of filling the groove region by buildup welding. The groove formation step forms a first inclined surface in the first projection facing the groove region to be gradually distant from a joint position joined with the second projection so as to be closer to an outer surface of the first projection, and forms a second inclined surface in the second projection facing the groove region to be gradually distant from the joint position joined with the first projection so as to be closer to an outer surface of the second projection.

Abstract: A metal-resin joining method of joining a metal member to a composite material member including a fiber reinforced plastic composite material includes an applying step of applying a first adhesive that is a thermosetting adhesive to a first region between the metal member and the composite material member, and applying a second adhesive that is a thermosetting adhesive to a second region between the metal member and the composite material member, a provisional bonding step of irradiating a first irradiation region of the metal member opposed to the first region with a laser light, and heating and curing the first adhesive to provisionally bond the metal member and the composite material member together, and a main bonding step of curing the second adhesive after the provisional bonding step to bond the metal member and the composite material member together.

Abstract: Two welding wires whose current values are individually variable are placed along a groove of steel plates, and two operations are repeated, the first operation including: passing substantially the same current through both welding wires; generating a cathode spot in front of a molten pool by one welding wire's arc on a welding-direction forward side; and cleaning the steel plates' surfaces by the arc, and the second operation including: passing a pulse current having a higher value than that of the welding wire through the other welding wire, so that a cathode spot is generated in the molten pool by each welding wire's arc to newly form a molten pool; and advancing both welding wires in the welding direction to move the cathode spot to the newly-formed molten pool, and at the same time performing welding within an area where oxides on the steel plates' surfaces are removed.

Abstract: A crack repair method includes a build-up welding step of performing build-up welding on a portion of an existing steel structure where a crack is generated while feeding a filler wire, and a laser beam piercing welding step of performing piercing welding using a laser beam on a filler material build-up portion caused by the build-up welding in the build-up welding step and the crack. The crack can be melted and repaired without lowering a toughness value regardless of an operation condition.

Abstract: Provided is a crack repair method of melting and eliminating a crack generated in a steel material, the method including holding a tab plate in surface contact with the steel material in which the crack is generated, thereafter continuously irradiating the tab plate to a first end portion of the crack in the steel material with a laser beam, and subsequently continuously irradiating the crack with the laser beam along the crack to a second end portion of the crack to melt and eliminate the crack. Consequently, when eliminating the crack generated in a constituent member of an existing structure or a constituent member such as a machine component, the crack can be eliminated without forming a through hole in the constituent member.

Abstract: A laser welding repair device includes a laser oscillator, a laser head that condenses laser light from the laser oscillator to irradiate a repair portion, a temperature sensor that detects a temperature distribution of a steel material irradiated with the laser light, and a control unit. The control unit sets a spot diameter of the laser light to be less than 3 mm, moves the laser head and enlarges a heat input area to check for a crack in the heat input area, the heat input area being formed by irradiating the steel material with the laser light, and controls the laser head to irradiate a region where a temperature detected by the temperature sensor is equal to or less than a mechanical melting temperature of the steel material. Where a welding is performed in a flat position, the crack can be easily and reliably erased without causing burn through.

Abstract: A welding method wherein the root gap aperture displacement is measured before welding begins, and a welding material having a Mn/S ratio and a Mn/Si ratio compatible with the measured root gap aperture displacement is selected from gas-shielded arc welding materials. Gas-shielded arc welding is then performed using the selected welding material.

Abstract: A welding method wherein the root gap aperture displacement is measured before welding begins, and a welding material having a Mn/S ratio and a Mn/Si ratio compatible with the measured root gap aperture displacement is selected from gas-shielded arc welding materials. Gas-shielded arc welding is then performed using the selected welding material.

Abstract: A method of forming stiffened plate by welding a plurality of stiffener materials and a steel plate, so that closed cross-sectional structures are secured onto a surface of the steel plate. The stiffener materials are joined to the steel plate as a result of edge portions of the stiffener materials which are in contact with the steel plate by being laser welded at a predetermined welding speed as a result of a laser having a predetermined output being irradiated from a predetermined direction thereon from the external side of the closed cross-sectional structures. Accordingly, it is possible to achieve an improvement in the weld quality when welding stiffener materials onto a steel plate, and to achieve an improvement in fatigue strength.

Abstract: A method of forming stiffened plate by welding a plurality of stiffener materials and a steel plate, so that closed cross-sectional structures are secured onto a surface of the steel plate. The stiffener materials are joined to the steel plate as a result of edge portions of the stiffener materials which are in contact with the steel plate by being laser welded at a predetermined welding speed as a result of a laser having a predetermined output being irradiated from a predetermined direction thereon from the external side of the closed cross-sectional structures. Accordingly, it is possible to achieve an improvement in the weld quality when welding stiffener materials onto a steel plate, and to achieve an improvement in fatigue strength.

Abstract: An end face (20) of one (10a) of two adjacent thick steel plates (10a, 10b) intended to construct a corner joint of a bridge column is formed into a beveled end face (22). Laser beam welding is applied to a root portion (24) of the beveled end face, and arc welding is applied to bevels (26, 28) thereof so that grooves defined by the bevels (26, 28) are filled with weld metal (40).

Abstract: A stiffened plate is formed by welding a plurality of stiffener materials which, together with a steel plate, form closed cross-sectional structures onto a surface of the steel plate. The stiffener materials are joined to the steel plate as a result of edge portions of the stiffener materials which are in contact with the steel plate by being laser welded at a predetermined welding speed as a result of a laser having a predetermined output being irradiated from a predetermined direction thereon from the external side of the closed cross-sectional structures. Accordingly, it is possible to achieve an improvement in the weld quality when welding stiffener materials onto a steel plate, and to achieve an improvement in fatigue strength.

Abstract: An end face (20) of one (10a) of two adjacent thick steel plates (10a, 10b) intended to construct a corner joint of a bridge column is formed into a beveled end face (22). Laser beam welding is applied to a root portion (24) of the beveled end face, and arc welding is applied to bevels (26, 28) thereof so that grooves defined by the bevels (26, 28) are filled with weld metal (40).

Abstract: A stiffened plate obtained by welding one or a plurality of stiffening materials (20) onto the surface of a steel plate (10), the stiffened plate in which a single-bevel or single-J groove (24) is formed in an end (22) of the stiffening material, which contacts the steel plate; and a root portion (26) of the single-bevel or single-J groove is subjected to laser beam welding, and a splay portion (28) to arc welding.