METHOD AND DEVICE FOR HEATING FOR IMPROVING RESIDUAL STRESS IN WELDED JOINT PART OF PIPING

摘要

PURPOSE:To prevent generation of an intergranular stress corrosion crack owing to tensile stress by attaching plural inductor pieces which are made into halved construction and have different diameters to the outside circumference in the weld zone of pipes, conducting electricity thereto and adjusting freely the number and interval of the inductors thereby heating uniformly and inductively the weld heat affected zone. CONSTITUTION:The residual tensile stress in the weld zone 1 of a small-diameter pipe 1A and a large-diameter pipe 1B in piping of a nuclear power plant, etc. is improved to compressive stress to prevent generation of the intergranular stress corrosion cracking in the weld zone 1 by the high-temp. and high-pressure water passing through the inside. Inductor pieces 21, 22, 23, 24 meeting the diameters of the pipes 1A, 1B are formed respectively into halved shapes and are attached to mounting frames 41, 42 so as to enclose the outside circumferential part before and behind the weld zone for the above-mentioned purpose. High-frequency current is passed to said pieces to heat uniformly the parts before and behind the weld zone 1 including said zone by the resistance heat generated by the induction current. Since the inductor pieces can be attached to the mounting frames at the varied interval and number, the weld zone 1 and the heat affected zone thereof are uniformly heated by the simple control of the interval and number, by which the residual tensile stress is relieved and is changed to compressive stress.