What is the manufacturing method of structural steel pipe

Manufacturing method of structural steel pipe:
1. Plate probe: after the steel plate used to manufacture large-diameter submerged arc welded straight seam steel pipe enters the production line, first carry out full plate ultrasonic inspection;
2. Edge milling: two sides of the steel plate are milled by the edge milling machine to achieve the required plate width, plate edge parallelism and groove shape;
3. Pre bending: pre bending the plate edge with pre bending machine to make the plate edge have the required curvature;
4. Forming: on JCO molding machine, first press half of the pre bent steel plate into "J" shape after several steps of stamping, then bend the other half of the steel plate into "C" shape, and finally form the "O" shape of the opening;
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 of LSAW steel pipe;
8. Ultrasonic inspection I: conduct 100% inspection on the internal and external welds of straight welded steel pipe and the base metal on both sides of the weld;
9. X-ray inspection I: 100% X-ray industrial television inspection shall be conducted for internal and external welds, and image processing system shall be adopted to ensure the sensitivity of flaw detection;
10. Expanding: the full length of submerged arc welded straight seam steel pipe shall be expanded to improve the size accuracy of steel pipe and improve the distribution of internal stress of steel pipe;
11. Hydrostatic test: the expanded steel pipes shall be inspected one by one on the hydrostatic test machine to ensure that the steel pipes meet the test pressure required by the standard. The machine has the function of automatic recording and storage;
12. Chamfering: the qualified steel pipe shall be processed at the pipe end to meet the required pipe end groove size;
13. Ultrasonic inspection II: carry out ultrasonic inspection one by one again to check the possible defects of straight seam welded steel pipe after expanding and water pressure;
14. X-ray inspection II: carry out X-ray industrial television inspection and pipe end weld film for the steel pipe after expanding and hydrostatic test;
15. MT for pipe end: conduct this inspection to find defects at pipe end;