PURPOSE: To prevent the low temperature crack during the welding by preheating the groove surface before the welding and keeping the preheated condition, and heating the weld zone under the prescribed condition before the weld zone is cooled, and keeping the heated condition in a method where the ferritic heat resistant steel is arc welded to obtain the weld metal with the Cr equivalent calculated by the prescribed formula being in the prescribed range.
CONSTITUTION: The ferritic heat resistant steel is arc welded to provide the weld metal whose Cr equivalent obtained by the formula is 4-13. The groove surface is preheated at 150-300°C before the welding, and the temperature between each welding pass is kept at 150-300°C. After the welding is completed, and before the weld zone is cooled below 300°C, the weld zone is heated at 150-300°C and this condition is kept for ≥10 minutes and ≤2 hours per 25mm of the base metal thickness. The reliability of the weld zone can be greatly improved in applying the high Cr ferritic heat resistant steel of high strength to the energy plant of high temperature and high efficiency. Each term in the formula indicates the weight % of each element of the weld metal.
TANAKA TAKASHI
OKITA SHIGERU
YURIOKA NOBUTAKA
