Whether the welded steel pipe is well-shaped or not is related to the welding sequence

The welding sequence of steel pipes is to determine which part is welded first and which part is welded later in the structure of the welded steel pipe, that is, the welding sequence of each weld of the steel pipe.

First, the influence of the unreasonable welding sequence of steel pipes on welding quality:

(1) The welding sequence of steel pipes affects the stress and deformation of weldments. An unreasonable welding sequence of steel pipes will cause deformation of weldments or excessive internal stress, reduce the quality of steel pipes, and even cause the steel pipes to be scrapped.

(2) An unreasonable welding sequence of assembly and steel pipes will make it difficult to weld certain positions of steel pipes, or even impossible to weld, thereby reducing the strength or airtightness requirements of the welded structure of the steel pipes.

(3) If the welding sequence of steel pipes is not selected reasonably, the welds in contact with corrosive media will be subjected to heat after welding, resulting in intergranular corrosion and reducing the corrosion resistance of the weldments.

Second, the basic principles for selecting the welding sequence of steel pipes are as follows:

(1) From the perspective of assembly welding, the welding sequence of steel pipes should be considered on the premise of not causing difficulty in welding steel pipes.

(2) Consider the following from the perspective of reducing residual stress and steel pipe welding deformation:

a. Weld from the center of the steel pipe structure to the outside;

b. Weld from the direction of the thick plate to the direction of the thin plate;

c. Weld joints with large shrinkage first, then weld joints with small shrinkage;

d. Weld vertical welds first, then horizontal welds;

e. Parallel welds should be welded simultaneously and in the same direction as much as possible;

f. Weld short steel pipe welds first, then weld long steel pipe welds.