What are the welding methods and processes of small-diameter thick-walled welded pipes, and what are the precautions?

Welding method of small-diameter thick-wall welded pipe

First of all, clean the oil, paint, water, rust etc. on the welding port, then open the groove according to the wall thickness, and then the gap of the product is generally 1-1.5 times of the diameter of the electrode or welding wire. If the groove is accidentally opened, it can be kept smaller. Spot welding is at least three points, but four points is better. It should be half welded while half left when welding. The starting point should be higher than the bottom point by about one centimeter. If the wall of the welded pipe is thick, it should be layered in two layers, and the second layer can only be welded after the first layer has been finished.

Processing flow

Round tube billet → heating → perforation → three-roller cross-rolling, continuous rolling or extrusion → tube removal → sizing (or reduced diameter) → cooling → straightening → hydraulic test (or flaw detection) → marking

Height of Weld Seam

When the wall thickness ≤ 12.5mm, the residual height of the weld is ≤3.0mm; when the wall thickness of the welded pipe＞12.5mm, the residual height of the weld is ≤ 3.5mm.

Curvature

Welded pipes with a nominal outer diameter ≤ 168.3mm, It should be straight or the bending index specified according to the agreement between the supplier and the buyer;

For welded pipes with a nominal outer diameter＞168.3mm, the bend shall not exceed 0.2% of the total length of the welded pipe.

For a welded pipes wall thickness ＞4mm, the pipe end can be machined with grooves of 30 ° + 5 ° 0 °, rooting 1.6mm ± 0.8mm, and the pipe end slope is ≤ 5mm.