PURPOSE: To cool the weld line surely over the entire line by injecting cooling water in the shapes of hollow circular cones to the inside surface of austenitic stainless steel pipes including the weld zone thereof from a spray nozzle disposed in the pipe near the butt weld zone of said pipes.
CONSTITUTION: A hollow circular cylindrical spray nozzle 23 is disposed in the above-described steel pipes 1, and the cooling water 3 supplied from a pump is injected in the shapes of hollow circular cones from the nozzle 23 to cool the inside surfaces of a butt-weld zone 2. More specifically, the weld zone 2 of the pipes 1 is welded under the same conditions of natural air cooling as in the prior art in the initial layer or up to the 2nd layer. For the 2nd or 3rd and secceeding layers after said layer, the weld zone is welded while the inside surface of the pipes is cooled with the cooling water 24 in the shapes of hollow circular cones injected from the nozzle 23. According to this method, positioning is facilitated, the entire line of the weld line is cooled surely and the amt. of the water to be used is decreased.
INDOU HIROSATO
OONO YUTAKA
