HEAT TREATMENT OF FUSION WELDED PART OF MAIN PIPE AND BRANCHED PIPE

摘要

PURPOSE:To effectively improve the residual stress of the fusion welded part of a main pipe and a branched pipe by increasing a magnetic field generated by a high- frequency heating coil for the main pipe at its weakened part with a high frequency heating coil for the the branched pipe to uniformly heat the welded part. CONSTITUTION:In a method of heat treating the fusion welded part of main pipe 1 and branched pipe 2 with high frequency heating coils while feeding a cooling medium to the inside of the welded part, a weakened part of a magnetic field generated by high frequency heating coil 3 for main pipe 1 is increased to a degree equal to that of other part with a magnetic field generated by high-frequency heating coil 3b for branched pipe 2. As a result, the welded part is uniformly heated to effectively improve the tensile residual stress of the inside of the welded part.