HEAT TREATMENT METHOD FOR BRANCH PIPE WELDED PORTION, AND BRANCH PIPE SEAT STRUCTURE

摘要

PROBLEM TO BE SOLVED: To provide a heat treatment method which enables an alleviation of tensile residual stress caused by welding or processing of a pipe.

SOLUTION: In a heat treatment method in which a small bore pipe having a diameter of not larger than 200 mm and a thickness of not larger than 15 mm is welded to a large bore pipe using a joining joint, heating is made near a welding portion after welding the small bore pipe to the joining joint, and then pipe inner surfaces are cooled with a refrigerant, the distance between a heating area and the large bore pipe is not smaller than 70 mm.

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