Thick-walled straight seam welded pipe, submerge arc welding process

1. Plate Inspection: After the steel plate used for manufacturing large-diameter electric resistance welded straight seam steel pipes enters the production line, it undergoes full-panel ultrasonic testing.

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

3. Pre-bent Edges: Utilize a pre-bending machine to bend the sheet edges to achieve the required curvature.

4. Forming: On the JCO forming machine, first, half of the pre-bent steel plate is progressively stamped multiple times to form a "J" shape. Then, the other half of the steel plate is similarly bent to form a "C" shape, ultimately creating an open "O" shape.

5. Pre-welding: Join the formed thick-walled straight seam welded pipes and conduct continuous welding using gas shielded welding (MAG).

6. Internal Welding: Employed longitudinal multi-wire submerged arc welding (*up to four wires) for welding on the inner side of straight seam steel pipes.

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

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

9. X-ray Inspection I: Industrial television X-ray inspection of internal and external weld seams.