Straight seam steel pipes can be divided into high-frequency straight seam steel pipes and submerged arc welded straight seam steel pipes according to the production steps. Submerged arc welding straight seam steel pipes are divided into UOE, RBE, JCOE steel pipes, etc. according to their different forming methods. The following describes the most common high-frequency straight seam steel pipe and submerged arc welding straight seam steel pipe forming process.

Submerged arc welding procedure

1. Plate exploration: After the steel plate used to manufacture the large-diameter submerged arc welded straight seam steel pipe enters the production line, first conduct a full plate ultrasonic inspection;

2. Edge milling: Both sides of the steel plate are milled on both sides by the edge milling machine to achieve the required plate width, plate edge parallelism and groove shape;

3. Pre-bending: Pre-bending the edge of the board with a pre-bending machine, so that the board has a curvature that meets the requirements;

4. Forming: On the JCO forming machine, first half of the pre-bent steel plate is pressed by multiple steps and pressed into a "J" shape, and then the other half of the steel plate is also bent into a "C" shape, and finally an opening is formed "O" shape

5. Pre-welding: the formed straight seam welded steel pipe is joined and continuous welding is performed by gas shielded welding (MAG);

6. Inner welding: vertical longitudinal multi-wire submerged arc welding (up to four wires) is used for welding inside the straight seam steel pipe;

7. External welding: longitudinal multi-wire submerged arc welding is used to weld the outside of the straight seam submerged arc welded steel pipe;

8. Ultrasonic inspection Ⅰ: 100% inspection of the internal and external welds of the straight welded steel pipe and the base metal on both sides of the weld;

9. X-ray inspection I: 100% X-ray industrial TV inspection of the internal and external welds, using an image processing system to ensure the sensitivity of flaw detection;

10. Enlarging diameter: Enlarging the full length of the submerged arc welded straight seam steel pipe to improve the dimensional accuracy of the steel pipe and improve the distribution of stress in the steel pipe

11.Hydraulic pressure test: The expanded steel pipe is inspected one by one on the hydraulic pressure testing machine to ensure that the steel pipe meets the test pressure required by the standard.

12. Chamfering: processing the pipe ends after passing the inspection to achieve the required pipe end groove size;

13. Ultrasonic inspection II: Conduct ultrasonic inspection one by one again to check the defects that may occur after the expansion of the longitudinal welded steel pipe and water pressure;

14. X-ray inspection II: X-ray industrial TV inspection and filming of pipe end welds on steel pipes after expansion and hydrostatic test;

15. Tube end magnetic particle inspection: carry out this inspection to find tube end defects;

16. Anti-corrosion and coating: The qualified steel pipe shall be anti-corrosion and coating according to user requirements.