| 摘要 |
PURPOSE:To reduce stress cracking and corrosion fatigue due to welding by cooling a weld zone formed by welding inner and outer pipes and its vicinities from the inside and outside and by heating the inner pipe from the inside by induction heating to provide a temp. difference to each of the pipes. CONSTITUTION:The tip of an outer pipe 2 covering an inner pipe 1 is welded to the pipe 1, a heating coil 5 is put in the pipe 1, and a part of the pipe 1 close to the resulting weld zone 3 is heated from the inside. At the same time, a coolant is allowed to flow through the pipe 1 in a direction (b), and it is blown on the surfaces of the weld zone 3 and its vicinities from a direction (a) to provide a temp. difference to each of the pipes. The induction heating is then stopped, and the cooling from the inside and outside is continued to produce residual stress. Thus, the resistance of the double-walled pipe to stress corrosion cracking and corrosion fatigue is considerably improved. |
