1. Plate inspection: After the steel plate used for manufacturing large-diameter submerged arc welded straight seam steel pipe enters the production line, ultrasonic inspection shall be conducted on the whole plate;
2. Edge milling: milling the two edges of the steel plate on both sides with an edge milling machine to achieve the required plate width, plate edge parallelism and groove shape;
3. Pre-bending: pre-bending the edge of the plate with a pre-bending machine to make the edge of the plate have the required curvature;
4. Forming: First, on the JCO forming machine, half of the pre-bent steel plate is pressed into a J-shape through multiple processes, and then the other half of the steel plate is also pressed into a C-shape, and finally an open O-shape is formed.
5. Pre-welding: seam welding and continuous welding of the formed straight seam welded steel pipe by gas shielded welding (MAG);
6. Internal welding: longitudinal multi-wire submerged arc welding (up to four wires) is adopted for the inside of the straight seam welded steel pipe;
7. External welding: longitudinal multi-wire submerged arc welding is adopted to weld on the outer side of longitudinal submerged arc welded steel pipe;
8. Ultrasonic flaw detection 1: carry out 100% flaw detection on the inner and outer welds of the straight welded steel pipe and the parent metal on both sides of the weld;
9.X-ray flaw detection 1: 100% X-ray industrial television flaw detection is carried out for both internal and external welds, and an image processing system is adopted to ensure the flaw detection sensitivity;
10. expanding: expanding the full length of submerged arc welded straight seam steel pipe to improve the dimensional accuracy of steel pipe and improve the internal stress distribution of steel pipe;
1 1. Hydrostatic test: The expanded steel pipes are inspected one by one on the hydrostatic testing machine, which has the function of automatic recording and storage.
12. Chamfering: processing qualified steel pipes into required pipe end groove size;
13. Ultrasonic inspection II: Ultrasonic inspection shall be carried out again one by one to check the possible defects of straight welded steel pipes after flaring and water pressure;
14.X-ray inspection II: X-ray industrial television inspection and filming of pipe end weld after expanding and hydrostatic test;
15. Magnetic particle inspection of pipe end: this inspection is to find the defects of pipe end;
16. Anti-corrosion coating: qualified steel pipes shall be coated with anti-corrosion coating according to user's requirements.