LSAW steel pipes forming technology

LSAW (Longitudinal Submerged Arc Welded) steel pipes are a widely appreciated construction material known for their excellent performance and reliability. But how are they formed? The following are the key steps in the forming process.

Pre-bending
A pre-bending machine is used to bend the plate edges to the required curvature, preparing the steel plate for the subsequent forming steps.

Forming
The pre-bent steel plate undergoes a multi-step process on a JCO forming machine.

First, half of the plate is gradually pressed into a "J" shape through successive punches.

The other half is then bent similarly to form a "C" shape.

Finally, the two halves are combined to create an open "O" shape.

Pre-welding
The "O"-shaped steel pipe is joined and welded continuously along the longitudinal seam using gas-shielded arc welding (MAG).

Internal Welding
Longitudinal multi-wire submerged arc welding, utilizing up to four wires, is applied to weld the interior of the LSAW steel pipe.

External Welding
Similarly, longitudinal multi-wire submerged arc welding is performed on the pipe's exterior, ensuring a robust and uniform weld seam.

Ultrasonic Inspection
A 100% ultrasonic inspection is conducted on the internal and external welds, as well as the parent material on both sides of the weld, to detect any flaws.

X-ray Inspection
Internal and external welds undergo 100% X-ray industrial television inspection. An image processing system is used to ensure the flaw detection sensitivity meets stringent standards.

Diameter Expansion
The entire length of the LSAW steel pipe is expanded to improve dimensional accuracy and evenly distribute internal stress, enhancing the pipe's structural integrity.

Hydrostatic Testing
Each pipe is subjected to a hydrostatic pressure test using a specialized machine to verify its ability to withstand the required pressure standards. The machine automatically records and stores test results for traceability.