WELDING METHOD OF WELD JOINT

PURPOSE:To weld exactly and with high efficiency a large-sized and thick weld joint having scarcely a welding defect by putting a fixed strap against the inside of a groove varied in three dimensions, putting a strap of shape corresponding to the groove against the outside, and executing the welding. CONSTITUTION:A fixed backing strap 4 is placed and fixed to the inside of a weld joint 3 over the whole, and the first piece of a surface strap 5 of the corresponding shape is put against a welding start point 6, and held down by a pressing roller. Subsequently, a molten metal is poured into a groove part 8 by an electrogas arc welding method, etc., a weld zone is cooled by each water-cooled strap 4, 5, and welding is executed. An object to be welded is rotated at a speed being almost equal to a welding speed, and when welding of this first piece part has been ended, the second piece of the surface strap 5 is placed on, welding is executed in the same way, and welding is executed successively up to the final piece part. In order to control a welding position, a turning table, etc. are used.