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Interpretation of welded pipe welding residual stress relief
Welding residual stress refers to the temperature difference inside the weldment caused by heating and cooling during welding, which leads to inconsistent deformation and internal stress. Welding residual stress causes deformation, cracking and other welding defects. Welding residual stress can break the weld, and also lead to unacceptable deformation of the workpiece, leading to structural brittle fracture, corrosion resistance and tensile residual stress, Reduce fatigue strength and stability limit.
How to control the residual stress of welding
Welding stress is inevitable. On the one hand, welding deformation will release some welding stress, on the other hand, it will exist in the form of residual stress, but welding components generally have residual stress and deformation.
The method of controlling welding residual stress
1.On the premise of ensuring the strength of the weldment, the stamping structure should be adopted to reduce the welding structure and the number of welds. The welds should not be too concentrated to avoid excessive heat input in local areas.
2.In order to prevent the superposition of welding residual stress and external load, the welding seam should be arranged outside the maximum working stress area, so as not to affect the bearing capacity of the component, and avoid too concentrated welding seam, so as to maintain good welding operability.
3.The reasonable joint mode and the method of reducing the local stiffness are adopted to make the weld shrink freely and reduce the stress concentration in the welded joint.
4.Adopt welding methods with concentrated energy density and less heat input, such as argon arc welding and ion arc welding, to reduce welding residual stress.
The generation process of welding residual stress is complex, and the disadvantages outweigh the advantages. Therefore, effective measures should be taken to reduce the welding residual stress. The common methods include shot peening, laser treatment, heat treatment, vibration treatment, cryogenic treatment, ultrasonic treatment, etc.
There are many methods to measure and eliminate the welding residual stress. Each has its advantages and disadvantages. It can choose the appropriate method according to its own needs, economic cost and operation difficulty.
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