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Primary and secondary heating control residual stress local heat treatment method

A technology of local heat treatment and residual stress, which is applied in the field of heat treatment, can solve problems such as stress corrosion cracking of welded joints, uneven microstructure of welded joints, and difficulty in eliminating welding residual stress, etc., so as to reduce labor intensity, easy operation, and reduce construction cycle effect

Active Publication Date: 2021-02-26
CHINA UNIV OF PETROLEUM (EAST CHINA)
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  • Claims
  • Application Information

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

Method used

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  • Primary and secondary heating control residual stress local heat treatment method
  • Primary and secondary heating control residual stress local heat treatment method
  • Primary and secondary heating control residual stress local heat treatment method

Examples

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Embodiment example 1

[0083] Such as Figure 1~3 , a super-large pressure vessel has a cylinder thickness of 50mm and a diameter of 40m. The reinforcing plate is a "circular" reinforcing plate with a thickness of 120mm and a diameter of about 4.2m. The width of the main heating belt is 600mm, the distance between the main and auxiliary heating belts is 400mm, the width of the auxiliary heating belt is 400mm, and the maximum temperature of the auxiliary heating is 500°C. Numerical simulation is carried out according to the heat treatment conditions and related inputs. Only the main heating method, that is, "bull's eye" heating, is used to obtain the stress cloud distribution after the heating is completed as follows: figure 2 shown. Depend on figure 2 It can be seen that a large compressive stress is generated on the top and bottom of the reinforcing plate, and the distance from the weld seam is about 600mm. On this basis, the local heat treatment method of primary and secondary cooperative he...

Embodiment example 2

[0085] Such as figure 1 , establish an axisymmetric model, the size of the closed weld of the cylinder is φ20000×50×92000, V-shaped groove, a total of 60 welds. The width of the main heating belt is 400mm, the distance between the main and auxiliary heating is 300mm, the width of the auxiliary heating belt is 300mm, and the holding temperature of the auxiliary heating is 300°C. Welding and heat treatment process analysis of body closing welds is carried out by using numerical simulation method. The local heat treatment method of primary and secondary heating is adopted. Output the axial and hoop stress distribution of the P1 path near the inner wall weld of the closing weld of the cylinder, as shown in the figure. Figure 4 (a) The ordinate indicates the axial stress along the P1 path of the inner wall of the closed weld of the cylinder, and the abscissa indicates 30mm from both sides of the weld; Figure 4 The ordinate in (b) represents the hoop stress along the P1 path of...

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Abstract

The invention relates to the technical field of heat treatment, and provides a local heat treatment method for primary and secondary heating to regulate residual stress. The main heating zone acts on the weld to adjust the microstructure and hardness of the weld to make the structure uniform and realize microscopic residual stress regulation; the secondary heating zone is applied to generate compressive stress on the inner surface of the weld at a distance from the weld to achieve Macroscopic compressive stress control. Avoiding the use of reinforcement plates, greatly reducing labor intensity and construction period; compared with traditional heat treatment methods, it greatly reduces the deformation near the weld and transfers the maximum deformation to the non-weld area; by applying secondary heating and strictly Controlling the time interval between main and auxiliary heating can realize structural improvement and greatly regulate welding residual stress; it can optimize the effect of local heat treatment, and produce small tensile stress or even compressive stress on the inner surface of the weld, which fundamentally solves the problem of large-scale equipment. The problem of leakage due to stress corrosion cracking at the weld.

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 ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D11/00C21D9/50C21D1/42
CPCC21D1/42C21D9/50C21D11/00Y02P10/25C21D2221/00
Inventor 蒋文春金强谷文斌涂善东
Owner CHINA UNIV OF PETROLEUM (EAST CHINA)