Description of the main production process for large diameter straight seam welded pipes:

1. Plate inspection: Upon entering the production line, the steel plate used to manufacture large-diameter submerged arc welded straight seam steel pipes is first subjected to a full plate ultrasonic inspection.

2. Milled Edges: Double-sided milling of the steel plate edges using a milling machine to achieve the required width, parallelism of the edges, and bevel shape.

3. Pre-bent Edges: Utilize a pre-bending machine to pre-bend the panel edges, achieving the required curvature.

4. Forming: On the JCO forming machine, first, half of the pre-bent steel plate is pressed into a "J" shape through multiple progressive stamping steps. Then, the other half of the steel plate is bent in the same manner to form a "C" shape, ultimately creating an open "O" shape.

5. Pre-welding: Join the formed straight seam welded steel pipes and carry out continuous welding with gas shielded welding (MAG).

6. Internal Welding: Utilizing longitudinal multi-wire submerged arc welding (up to four wires) for welding inside straight seam steel pipes.

7. External Welding: Uses longitudinal multi-wire submerged arc welding on the outer side of straight seam submerged arc welded steel pipes.

8. Ultrasonic Inspection I: Inspect the inner and outer weld seams of straight seam steel pipes, as well as the base materials on both sides of the weld seams.

9. X-ray Inspection I: Conduct X-ray industrial TV inspection on internal and external weld seams, utilizing image processing systems to ensure detection sensitivity.

10. Expanding Diameter: Expand the full length of the埋弧焊直缝钢管 to enhance the dimensional accuracy of the pipe and improve the distribution of internal stresses within the pipe.

11. Hydrostatic Test: Each pipe is individually tested on a hydrostatic testing machine to ensure it reaches the standard required test pressure after expansion, featuring automatic recording and storage capabilities.

12. Deburring: Process the pipe ends of the qualified steel pipes to achieve the required bevel size.

13. Ultrasonic Inspection II: Conduct an ultrasonic inspection on each pipe again to check for any potential defects that may arise after expansion and hydrostatic testing in straight seam welded steel pipes.

14. X-ray Inspection II: Conduct X-ray industrial television inspection and take end weld radiographs on the steel pipes after expansion and hydrostatic testing.

15. Tube End Magnetic Particle Inspection: This inspection is conducted to detect defects at the tube end.

16. Corrosion Protection and Coating: After qualification, steel pipes are treated with corrosion protection and coating as per customer requirements.