The Forming Process of Straight Seam Welded Pipe

What is the forming process of a straight seam welded pipe? A straight seam welded pipe is manufactured by rolling hot-rolled or cold-rolled steel plates or strips into a tubular shape and then welding the seam longitudinally using specialized welding equipment. Regardless of the specific welding technique, the key steps in producing straight seam welded pipes remain largely the same.

Key Steps in Straight Seam Welded Pipe Production

1. Plate Inspection – Steel plates used for large-diameter submerged arc welded straight seam pipes undergo full-plate ultrasonic testing upon entering the production line.

2. Edge Milling – A milling machine processes both edges of the steel plate to achieve the required width, parallelism, and groove shape.

3. Pre-Bending – A pre-bending machine shapes the plate edges to the required curvature.

4. Forming (JCO Process) – The pre-bent steel plate is pressed into a "J" shape on one half, then the other half is bent into a "C" shape, finally forming an open "O" shape.

5. Pre-Welding – The formed straight seam welded pipe is aligned and continuously welded using gas metal arc welding (MAG).

6. Internal Welding – Submerged arc welding (with up to four wires) is applied to the inner side of the straight seam welded pipe.

7. External Welding – Multi-wire submerged arc welding is performed on the outer side of the pipe.

8. Ultrasonic Testing I – A 100% inspection of the weld seam and adjacent base metal is conducted.

9. X-Ray Inspection I – Industrial X-ray imaging ensures weld integrity, supported by an image processing system for enhanced sensitivity.

10. Expanding – The entire length of the straight seam welded pipe undergoes expansion to improve dimensional accuracy and optimize internal stress distribution.

11. Hydrostatic Testing – Each pipe is pressure-tested to meet standard requirements, with automatic recording and data storage.

12. Chamfering – The pipe ends are machined to achieve the required bevel dimensions.

13. Ultrasonic Testing II – Additional ultrasonic inspection checks for defects post-expansion and hydrostatic testing.

14. X-Ray Inspection II – Further X-ray examination and weld imaging ensure quality.

15. Magnetic Particle Inspection – Detects potential defects at pipe ends.

16. Anti-Corrosion & Coating – The final straight seam welded pipe is coated based on customer specifications.

By following these steps, manufacturers ensure high-quality straight seam welded pipes suitable for various industrial applications. Whether for oil, gas, or structural uses, the precision in forming and welding guarantees durability and performance.

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