Partial post-weld heat treatment method for butt joint of three-way main pipe

Abstract

The invention relates to a tee joint main pipe butt joint local post weld heat treatment method. A main heating device and an auxiliary heating device are adopted in the method for heating at the same time. Heating elements of the main heating device are equal in power and width and are symmetrically arranged at the two ends of a welding seam. A temperature control thermoelectric couple is arranged on the side, opposite to the side where a branch pipe is located, of the welding seam. Parameters are set through a heat treatment cycle curve according to the post weld heat treatment technology. Heating elements of the auxiliary heating device are arranged adjacent to the main pipe end of the main heating device. A temperature control thermoelectric couple is arranged in the position, opposite to a shoulder peak of a tee joint, on a main pipe of the end of the main heating device. In the heat treatment process, the constant temperature is the temperature + / -10 DEG C of a pipe at the end of the main heating device in an independent heating constant temperature stage, and temperature rise time, constant temperature time and the temperature drop speed are 90% to110% of corresponding parameters of the main heating device respectively. According to the method, a point with the highest temperature is effectively prevented from deviating from the welding seam, the circumferential temperature difference of the welding seam is reduced, and the technical requirement for joint post weld heat treatment is met.

Description

technical field [0001] The invention relates to a local post-weld heat treatment method for a three-way main pipe butt joint, which is particularly suitable for the local post-weld heat treatment of a three-way main pipe butt joint whose branch pipes have been connected with external pipelines. Background technique [0002] Post-weld heat treatment is a kind of heat treatment to eliminate the residual stress of the butt joint and improve the structure and performance of the butt joint. The general process is: install the thermocouple → arrange the heating device → set the heat treatment parameters → wrap the insulation cotton → perform heat treatment . [0003] The tee is an important connecting part of the piping system. When post-weld heat treatment is required after welding with external pipes at the service site, usually only partial post-weld heat treatment can be performed. One end of the butt joint is connected to the external pipe, and the other end is connected to ...

AI Technical Summary

Problems solved by technology

This rule-of-thumb method often results in the highest temperature point not being exactly on the weld

The excursion of the maximum temperature and the existence of the circumferential temperature difference deteriorate the temperature field of the post-weld heat treatment of the joint, increase the residual stress of the joint after heat treatment, and have an adverse effect on the service performance and life of the joint; when the maximum temperature of the deviation exceeds the material After the phase transition point, the material recrystallizes, causing serious damage to the performance of the joint, and even directly leading to the scrapping of the joint

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