Abstract: An upper plate is arranged on the top surface of a lower vertical plate to form a T-type joint, and a penetration promoter is applied on the surface of the upper plate of the T-type joint. Subsequently, when performing non-consumable electrode arc welding, a penetration width w of a molten pool on the side of the vertical plate after penetrating through the back side of the vertical plate is formed equal to or greater than the vertical plate thickness if a lower vertical plate thickness is the same thickness as an upper plate thickness or thinner than the upper plate thickness, and the penetration width of the molten pool is formed equal to or greater than the upper plate thickness if the lower vertical plate thickness is thicker than the upper plate thickness, thereby forming a penetration shape having a desired welding metal part.

Abstract: The present invention has an object to reduce residual stress in a tensile direction of a weld on the inner side in contact with reactor water of austenitic stainless steel piping, and to change the residual stress into compressive stress, to reduce stress corrosive cracking. The present invention provides a welding process for stainless steel piping of laminating two types of welding wire made of different materials in a groove of austenitic stainless steel piping, including at least one of a first layer penetration welding step of performing a predetermined back bead width on the back side of the groove bottom and a tack welding step, a first lamination welding step of lamination welding of austenitic stainless steel wire from the bottom to the top of the groove, and a second lamination welding step of lamination welding of nickel-base alloy wire to a final layer at the top of the groove.

Abstract: A submerged laser beam irradiation equipment provides a high quality submerged laser beam processing of a submerged workpiece using only a small amount of a gas. The submerged laser beam irradiation equipment has: a focus lens for focusing a laser beam; a mirror tube which houses the lens; a first nozzle operating to cover the front end of the mirror tube in an irradiating direction of the laser beam; a skirt portion provided at the front end of the first nozzle for preventing water intrusion thereinto; and a shutter mechanism operable to open and close and provided between said skirt portion and said mirror tube for preventing water intrusion into said mirror tube.

Abstract: Disclosed is a highly reliable weld repairing method to repair a crack defect in structures and apparatus inside pressure vessels of nuclear reactors, while preventing generation of new crack defects in the structures and apparatus during the repairing. These structures and apparatus are made of any of stainless steel and Ni-base alloys, and are irradiated with high energy corpuscular ray during operating period of the reactor. The repairing method includes the steps of eliminating a region of the structure or the apparatus including a portion having the crack defect, and executing spot welding at a surface of the region continuously or interruptedly in a manner so as to form a first welded layer in a manner that each of the spot welded spots is half-overlapped with adjacent welded spots. Additionally, welding for forming at least a second layer, on the first welded layer, so that the at least a second layer is not deeper than a weld penetration thickness of the first welded layer can be performed.