LASW Production Process

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

1. Plate exploration: After the steel plate used to manufacture the large-diameter submerged arc welded straight seam steel pipe enters the production line, first conduct a full plate ultrasonic inspection;
2. Edge milling: Both sides of the steel plate are milled on both sides by the edge milling machine to achieve the required plate width, plate edge parallelism and groove shape;
3. Pre-bending: Pre-bending machine is used to pre-bend the board edge, so that the board edge has a curvature that meets the requirements;
4. Forming: On the JCO forming machine, first half of the pre-bent steel plate is pressed by multiple steps and pressed into a "J" shape, and then the other half of the steel plate is also bent and pressed into a "C" shape, and finally an opening is formed "O" shape
5. Pre-welding: joint the formed straight seam welded steel pipe and use gas shielded welding (MAG) for continuous welding;
6. Internal welding: longitudinal multi-wire submerged arc welding (up to four wires) can be used to weld inside the straight seam steel pipe;
7. External welding: longitudinal multi-wire submerged arc welding is used to weld on the outside of the straight seam submerged arc welded steel pipe;
8. Ultrasonic inspection Ⅰ: 100% inspection of the internal and external welds of the straight welded steel pipe and the base metal on both sides of the weld;
9. X-ray inspection Ⅰ: 100% X-ray industrial TV inspection of the internal and external welds, using an image processing system to ensure the sensitivity of flaw detection;
10. Enlarging diameter: Enlarging the full length of the submerged arc welded straight seam steel pipe to improve the dimensional accuracy of the steel pipe and improve the distribution of stress in the steel pipe;
11. Hydraulic test: The expanded steel pipes are inspected one by one on a hydraulic testing machine to ensure that the steel pipes meet the test pressure required by the standard. The machine has automatic recording and storage functions;
12. Chamfer: Process the pipe end after passing the inspection to the required pipe end groove size;
13. Ultrasonic inspection Ⅱ: Conduct ultrasonic inspection one by one again to check the defects that may occur after the expansion of the longitudinal welded steel pipe and water pressure;
14. X-ray inspection II: X-ray industrial TV inspection and filming of pipe end welds on steel pipes after expansion and hydrostatic test;
15. Tube end magnetic particle inspection: conduct this inspection to find tube end defects;
16. Anti-corrosion and coating: qualified steel pipes shall be anti-corrosion and coated according to user requirements.