Welding residual stress is an important problem in the field of welding engineering research. In the engineering application involving welding, we should pay attention to the influence of residual stress. For example, in the field of civil engineering, for the welding connection of steel structure, the residual stress has an impact on the fatigue performance and stable bearing capacity of the structure.

The first to bear the brunt are the welding parameters. Welding parameters are one of the important factors affecting the shape and performance of submerged arc welding seam. Welding parameters include welding current, voltage, welding speed, etc. If the welding parameters are incorrect, it will cause poor weld shape, and even weld cracks and other problems.

Our main products are high-frequency straight seam welded steel pipes and double-sided submerged arc welded steel pipes, etc., which are widely used in medium and low pressure fluid transmission pipelines such as oil, natural gas, water, steam, gas, etc., as well as structural steel pipes for piling, bridges, and buildings.

Generally, the welding part needs to go through the process of heating melting metallurgical reaction solidification crystallization solid phase transformation joint formation, which can also be summarized as the following three interrelated processes.

In the welding process, due to some high temperature heating and rapid cooling, thermal strain and compressive plastic strain will occur in the weld and near weld area of base metal, resulting in internal stress and deformation of components. The common welding deformation includes longitudinal deformation, tortuous deformation and distorted deformation. In actual production, these welding deformation usually do not appear alone, They come together and influence each other.

Incomplete penetration during welding refers to the defects caused by the base metal not melting and the weld metal not entering into the root of the joint. According to the welding method of the weldment, it can be divided into incomplete penetration at the root and incomplete penetration in the middle. The liquid weld metal does not enter into the root blunt edge. The one-sided welding of V-shaped or U-shaped groove is incomplete penetration at the root and the liquid metal does not enter into the middle blunt edge, In double V-groove or double U-groove, double side welding is incomplete in the middle.

There are many kinds of cracks in the welding process. According to the nature of the cracks, they can be divided into the following five categories

One of the factors that determine the chemical composition and performance of welded pipe's weld metal is the welding process performance and chemical metallurgical performance of flux.

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.