In-situ fast method of eliminating residual stress in welded joint of small-diameter pipe

Abstract

The invention relates to the technical field of life extension treatment of welded structures, in particular to a method for quickly eliminating the residual stress of welded joints of small-diameter pipelines. Specifically, the temperature difference deformation treatment is used to rapidly heat the compressive stress area on both sides of the small diameter pipe joint girth weld, resulting in a temperature difference between the heating area and the weld; the process is: 1) The heating area is symmetrically distributed around the weld, leaving The distance between the annular seam is 20mm-40mm; the heating width is 10-30mm; 2) Heating rapidly, so that the temperature difference between the heating zone and the annular seam reaches 150°C-550°C; then it can be cooled naturally. The invention can reduce the tensile stress of welded joints by 80% to 100%. The invention can not only eliminate most of the stress, but even completely eliminate the hazard of SCC, and has the characteristics of simple construction, high efficiency, fast speed, short time and low energy consumption. , especially suitable for on-site promotion and application.

Description

technical field [0001] The invention relates to the technical field of life extension treatment of welded structures, in particular to a method for quickly eliminating the residual stress of welded joints of small-diameter pipelines. technical background [0002] In petrochemical, metallurgical and other industries, small-diameter pipes (φ<300mm) play an important role in transportation pipeline systems. Due to the combined effect of the corrosion of the transported substances in the pipeline and the residual tensile stress in the welded joints of the pipelines, accidents such as running, leaking, dripping, leaking, etc., or even complete cracks often occur at the welded joints of the pipelines. The phenomenon of cracking caused by the action of corrosive medium and tensile stress is called stress corrosion cracking, or SCC for short. Due to the difficulty of completely eliminating the welding residual stress of small-diameter pipes, this phenomenon has been plagued by c...

AI Technical Summary

Problems solved by technology

Due to the difficulty of completely eliminating the welding residual stress of small-diameter pipes, this phenomenon has been plagued by chemical, metallurgical and other industries, which has potential safety hazards and caused great waste and loss. Therefore, it is necessary to solve the SCC problem of pipe joints

[0003] Traditional local heat treatment generally uses electric heating tape to wrap around the material for heating, and the stress can be reduced by creep, which can reduce the stress level to about two-thirds of the yield point of the material, but the cooling speed should not be too fast and the holding time should be longer. There is still a high residual stress, so the hazards of SCC cannot be completely eliminated

Moreover, the traditional local heat treatment has a fatal weakness, that is, low treatment efficiency and high energy consumption, which are not suitable for on-site promotion and application.