PURPOSE: To efficiently form an excellent bead while generation of defects of blow hole being correctly suppressed.
CONSTITUTION: A welding electrode 8 of TIG method is arranged on the down- hill position by setting the electrode arrangement angle between 20-80 degrees, while a welding electrode 10 of MIG method is arranged on the down-hill position by setting the electrode arrangement angle between 5-20 degrees. The initial circumferential layer welding is executed by using the welding electrode 8 of TIG method for the boundary part 4 of the tube end insertion of a double tube 3, and the second and subsequent build-up welding are continuously executed to the tube surface part by using the welding electrode 8 of TIG method and the welding electrode 10 of MIG method.
TOSHIMA SADAO
HORII YUKIHIKO
