To provide a welding method for a double tube structure capable of welding without shutting voids between an inner tube and outer tube.
In the welding method for the double tube structure having voids 20/21 between the inner tube 1 and outer tube 2, the inner tube 1 is welded with a laser beam 6 from the inside of the inner tube 1 or from a gap 22a behind a groove part 22 of the outer tube 2 whose groove has been machined. Thereafter, a ring-like filler metal 8 is inserted into the groove part 22 of the outer tube 2, and the ring-like filler metal 8 is molten with a TIG welding while making flow an inert gas into voids 20/21 between the outside of the inner tube 1 welded and the outer tube 2. By this way, a multi-layer TIG welding is executed using a welding wire 10 after executing a primary layer welding for the groove part 22 of the outer tube 2 without embeding voids 20/21 between the inner tube 1 and outer tube 2.
ISHIDE TAKASHI
MEGA MASAHIKO
HASHIMOTO YOSHIO
KAWAI YUKIHIRO
