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What are the measures to improve the fatigue strength of welded pipe welded structure,lsaw pipes,casing pipe distributor,carbon steel pipe distributor
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What are the measures to improve the fatigue strength of welded pipe welded structure

Date:2023-03-13View:29Tags:L80 tubing,hastelloy c276 pipe,pipe flange

The stress concentration points on the welded pipe welded joints and the structure reduce the source of stress concentration fatigue cracks, and the removal or reduction of stress concentration can improve the fatigue strength of the structure.

1.Adopt reasonable structure

The butt joint should be selected first, and the important structure should be changed into butt joint. The weld should avoid the corner. When the corner joint is used, the full penetration butt weld should be used, so that the internal force of the component can be transmitted smoothly and evenly, no additional stress is generated, the sudden change of the section can be reduced, and the eccentric load can be avoided. When the plate thickness or width difference is large, the smooth transition zone should be designed.

Do not set weld in the stress concentration area, do not set transverse weld on the main tension member, avoid three-way weld space intersection, if not, to ensure the internal and external quality of the weld, reduce the stress concentration at the weld toe, for the butt weld which can only be welded on one side, do not allow to place permanent backing plate, avoid intermittent welding, Because there is a high stress concentration at the beginning and end of each weld.

2.Correct weld shape and good internal and external weld quality

The weld reinforcement of butt joint should be small, and it is better not to leave reinforcement after welding. The T-joint should not use convex fillet weld, but concave fillet weld. The weld toe and base metal surface should be smooth transition, and the weld toe should be ground or argon arc remelted to reduce stress concentration.

There are different degrees of stress concentration in welding defects, such as cracks, incomplete penetration, undercut and so on, especially in thin plate welding defects, which have a great impact on fatigue strength. Therefore, in structural design, it is necessary to ensure that each weld is easy to weld, so as to reduce welding defects and remove excessive defects.

Adjustment of residual stress

The residual compressive stress or stress concentration on the surface of the component can improve the fatigue strength of the welded structure. By adjusting the local heating and welding sequence, it is beneficial to obtain the residual stress field to improve the fatigue strength. The residual compressive stress of the notched component is obtained by one-time pre overload tension.

Improve the structure and properties of the material

First of all, to improve the fatigue strength of base metal and weld metal, we should also consider the internal quality of the material. We should improve the metallurgical quality of the material, reduce the inclusions and refine the grain. Steel can improve the fatigue life. Heat treatment can obtain good microstructure, which can not only improve the strength, but also improve the plasticity and toughness. Secondly, the strength, plasticity and toughness should be reasonably matched, Strength is the ability to resist fracture, but high strength materials are sensitive to notch. Through plastic deformation, they can absorb deformation work, reduce peak value, redistribute high stress, slow down or even prevent crack propagation. Plasticity can ensure the full play of strength. Therefore, for high strength and ultra-high strength steels, improving plasticity and toughness will significantly improve fatigue resistance.