Large diameter straight seam steel pipe is more and more welcomed by petroleum and natural gas, slurry transportation, steel structure engineering and other industries for its advantages of high pressure bearing capacity, low resistance, low temperature resistance, corrosion resistance, easy installation and maintenance.

Description of main production process of large diameter straight seam welded pipe:

1. Plate prospecting: After the steel plate used to manufacture large diameter submerged arc welded straight seam steel pipe enters the production line, the whole plate ultrasonic inspection is carried out first.

2. Milling: Double-sided milling of steel plate edges by milling machine to achieve the required width, parallelism and groove shape.

3. Pre-bending edge: Pre-bending edge with pre-bending machine, so that the edge of the plate has the required curvature.

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

5. Pre-welding: to make the formed straight seam welded steel pipe seam 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 the inside of the straight seam steel pipe.

7. External welding: Longitudinal multi-wire submerged arc welding is used to weld the outer side of longitudinal submerged arc welded steel pipe.

8. Ultrasound Inspection I: 100% Inspection of the inside and outside welds and the base metal on both sides of the welds of the longitudinal welded steel pipe.

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

10. Diameter enlargement: The whole length of submerged arc welded straight seam steel pipe is enlarged to improve the dimensional accuracy of steel pipe and the distribution of internal stress of steel pipe.

11. Hydraulic test: The expanded steel pipe is inspected one by one on the hydraulic test machine to ensure that the test pressure meets the standard requirements. The machine has the function of automatic recording and storage.

12. Chamfering: The qualified steel pipe will be processed to meet the required pipe end groove size.

13. Ultrasound Inspection II: Ultrasound Inspection is carried out one by one again to inspect the possible defects of longitudinal welded steel pipe after diameter expansion and hydraulic pressure.

14. X-ray inspection II: X-ray industrial television inspection and photography of weld seam of pipe end after diameter enlargement and hydraulic test.

15. Tube end magnetic particle inspection: this inspection is carried out to find the defect of the tube end.

16. Anti-corrosion and Coating: Qualified steel pipes are anticorrosive and coated according to user's requirements.