Main production process of large-diameter straight seam welded pipe:
1. Plate probing: After the steel plate used to manufacture large-diameter submerged arc welded straight seam steel pipes enters the production line, it is first subjected to full plate ultrasonic inspection;
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, plate edge parallelism, and groove shape;
3. Pre bending edge: Use a pre bending machine to pre bend the edge of the board to achieve the required curvature;
4. Forming: On the JCO forming machine, first press half of the pre bent steel plate into a "J" shape through multiple steps of stamping, and then bend the other half of the steel plate into a "C" shape to form an open "O" shape
5. Pre welding: The formed straight seam welded steel pipe is welded together and continuously welded using gas shielded welding (MAG);
6. Internal welding: longitudinal multi wire submerged arc welding (up to four wires) is used to weld on the inner side of the straight seam steel pipe;
7. External welding: longitudinal multi wire submerged arc welding is used to weld on the outer side of the straight seam submerged arc welded steel pipe;
8. Ultrasonic Inspection I: Conduct a 100% inspection of the internal and external welds of the straight seam welded steel pipe, as well as the base materials on both sides of the weld;
9. X-ray Inspection I: Conduct 100% X-ray industrial television inspection on internal and external welds, using an image processing system to ensure the sensitivity of the inspection;
10. Diameter expansion: Expand the entire length of the submerged arc welded straight seam steel pipe to improve the dimensional accuracy of the steel pipe and improve the distribution of internal stress in the steel pipe;
11. Hydrostatic test: The expanded steel pipes are inspected one by one on a hydraulic testing machine to ensure that they meet the standard test pressure requirements. The machine has automatic recording and storage functions;
12. Chamfering: Process the qualified steel pipes at the pipe ends to achieve the required pipe end groove size;
13. Ultrasonic Inspection II: Perform ultrasonic inspection on each straight seam welded steel pipe again to check for possible defects that may occur after diameter expansion and water pressure;
14. X-ray Inspection II: Conduct X-ray industrial television inspection and tube end weld photography on steel pipes after expansion and hydrostatic testing;
15. Magnetic particle inspection of pipe ends: This inspection is conducted to discover defects in the pipe ends;
16. Anti corrosion and coating: Qualified steel pipes shall be anti-corrosion and coated according to user requirements.