Local heat treatment method for primary and secondary heating, regulating and controlling residual stress

Abstract

The invention relates to the technical field of heat treatment, and provides a local heat treatment method for primary and secondary heating, regulating and controlling residual stress. The local heattreatment method comprises the steps that a primary heating belt is applied to a welding line, the welding line microstructure and hardness are regulated and controlled, so that the structure is uniform, and microcosmic residual stress is regulated and controlled; and a secondary heating belt is applied at the distance from the welding line, compression stress is generated on the inner surface ofthe welding line, and macroscopic compression stress is regulated and controlled. No rib plates are used for deformation, and the maximum deformation is transferred to a non-welding line area; by applying the secondary heating and strictly controlling primary and secondary heating time interval, the welding residual stress can be greatly regulated and controlled while the structure is improved; and the local heat treatment effect can reach the optimal, lesser tensile stress and even pressure stress is generated on the inner surface of the welding line, and the problem of leakage due to the fact that corrosion and cracking are generated at welding lines of large equipment is fundamentally solved.

Description

technical field [0001] The invention relates to the technical field of heat treatment, in particular to a local heat treatment method for primary and secondary heating to regulate residual stress. Background technique [0002] As an important technology for major equipment manufacturing and safety, heat treatment is also a major problem. In petrochemical, nuclear power and other fields, pressure vessels, as key core equipment, are the main places to realize heat and mass transfer chemical reactions, and their in-service safety is of great significance. At present, my country's pressure vessels are constantly developing in the direction of large diameter, ultra-thickness, and ultra-length in terms of size, and the size continues to break through world records. The stress corrosion cracking (SCC) problem of welded joints has become the main reason for the failure of petrochemical and nuclear power equipment. [0003] Due to the limitation of the volume of the heat treatment ...

AI Technical Summary

Problems solved by technology

The main contradictions at present are: First, the microstructure of the welded joint is not uniform, and there are microscopic defects inside, such as element segregation or metal compounds (such as carbide and δ phase), which generate microscopic stress concentration and provide a driving force for intergranular stress corrosion cracking Second, local heat treatment is difficult to eliminate welding residual stress, and it is even more difficult to generate compressive stress on the inner surface of welded joints, which cannot solve the problem of stress corrosion cracking of welded joints

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