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

1. Plate probe: after the steel plate used to manufacture large diameter Submerged arc welding straight seam steel pipe enters the production line, the full plate ultrasonic inspection shall be carried out first;

2. Edge milling: Double sided milling is performed on the two edges of the steel plate using an edge milling machine to achieve the required plate width, edge parallelism, and groove shape;

3. Pre bending edge: Use a pre bending machine to pre bend the edge of the plate, so that the edge has the required curvature;

4. Forming: On the JCO molding machine, first half of the pre bent steel plate is stamped multiple times to form a "J" shape, then the other half of the steel plate is also bent to form a "C" shape, and finally an open "O" shape is formed

5. Pre welding: Make the formed straight seam welded steel pipe joint and use gas shielded welding (MAG) for continuous welding;

6. Internal welding: longitudinal multi wire Submerged arc welding (up to four wires) is used to weld inside the straight seam steel pipe;

7. External welding: longitudinal multi wire Submerged arc welding is used to weld outside the longitudinal Submerged arc welding steel pipe;

8. Ultrasonic Inspection I: Conduct 100% inspection on the inner and outer welds of straight welded steel pipes and the base metal on both sides of the welds;

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

10. Expanding: expand the full length of Submerged arc welding straight seam steel pipe to improve the dimensional accuracy of steel pipe and improve the distribution of stress in steel pipe;

11. Hydrostatic test: Inspect the expanded steel pipes one by one on a hydraulic testing machine to ensure that they meet the required test pressure. The machine has automatic recording and storage functions;

12. Chamfering: Process the qualified steel pipe at the pipe end to meet the required pipe end groove size;

13. Ultrasonic Inspection II: Conduct ultrasonic inspection one by one again to inspect the defects that may occur in longitudinally welded steel pipes after expansion and water pressure;

14. X-ray Inspection II: Conduct X-ray industrial television inspection and take photos of pipe end welds on steel pipes after expansion and hydraulic testing;

15. Pipe end magnetic particle inspection: Conduct this inspection to discover pipe end defects;

16. Corrosion prevention and coating: Qualified steel pipes shall be subjected to corrosion prevention and coating according to user requirements.