METHOD FOR RELIEVING RESIDUAL STRESS IN CIRCUMFERENTIAL WELD ZONE

摘要

PURPOSE:To relieve residual stress in a circumferential weld zone by locally expanding or contracting a part which is away from the weld zone in the axial direction to increase or decrease the diameter. CONSTITUTION:When a branch tube 7 is welded to the drum 8 of a heat exchanger, a heating coil 3 is placed around the drum 8 at a position which is away from the circumferential weld zone 2 by a length L represented by 0.54 (Rt)1/2 or 2t (where R is the diameter of the drum, and t is the thickness of the wall of the drum). High frequency current is supplied to the coil 3 from a high frequency heater through a connecting conductor 6 to expand the part of the drum 8 covered with the coil 3. By the expansion, local bending action is caused at parts close to the edges of the coil 3, so residual stress in the weld zone 2 is relieved.