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.

Generally speaking, there are several key points to form a beautiful and firm pattern.

There are many factors that affect the straight seam high frequency welded steel pipe, and these factors interact. Only by mastering the quality control points of the straight seam high frequency welded steel pipe can we better adjust them.

Hot expanded is a processing method for steel pipes. It is to process small-diameter steel pipes into large-diameter steel pipes with relatively low density but strong shrinkage. After the pipes undergo thermal expansion technology, the residual stress (internal stress) can be effectively eliminated, and the The mechanical properties of the steel pipe are improved to prepare for the subsequent process.

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.

The types of welded joints include butt joint, T-joint, lap joint and corner joint. The welded joints are mainly selected according to the welding structure, weld thickness, weld strength requirements and construction conditions.

The beginning of the weld refers to the weld at the beginning of welding, and the reinforcement of this part is easy to increase. This is because the temperature of the weldment is low at the beginning of welding, and the temperature cannot rise rapidly after arc striking, so the penetration is shallow and the reinforcement is large. In order to avoid this situation, the electric arc can be slightly lengthened after arc striking for preheating, and the arc can be properly lowered for normal welding.

Preheating refers to heating the workpiece to be welded to room temperature before or during welding. According to the application standard of materials, several preheating temperature levels are usually required in the current specification.

At present, in the oil and natural gas industry, straight seam high-frequency welded steel pipes are widely used in long-distance pipelines, oil well casings and other fields.

Large-diameter LSAW steel pipe are widely used in natural gas, petroleum, chemical and other fields. Generally, they refer to LSAW steel pipe with an outer diameter of more than 500mm. The common product models are: Φ325×8-20, Φ426×8-30, Φ450×8-40 , Φ508×8-40, etc.