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Bearing capacity of thick wall Longigudinally Submerged Arc Welding steel pipe
Jan 29, 2019

Bearing capacity of thick wall Longigudinally Submerged Arc Welding steel pipe


The production process of large-diameter straight seam steel pipe is described as follows:


  1. Board inspection: after the steel plate used to make large-caliber submerged arc welding straight seam steel pipe enters the production line, ultrasonic inspection of the whole board surface shall be carried out first;


2. Edge milling: milling the two sides of the steel plate through the edge milling machine to achieve the required plate width, plate edge parallelism and groove shape;


3. Pre-bending edge: use the pre-bending machine to pre-bend the edge of the plate, so that the edge of the plate has the required curvature;


4, molding: in the JCO molding machine will be the first half of the pre-bending steel plate after several steps through the stamping, pressed into a "J" shape, and then the other half of the steel plate is also bent, pressed into a "C" shape, finally form an open "O" shape;


5. Pre-welding: the straight seam steel tube after forming is closed and used gas shielded welding (MAG) for continuous welding;


6. Internal welding: vertical multi-wire submerged arc welding (up to four wires) is adopted for welding on the inside of straight seam steel pipe;


7. External welding: vertical multi-wire submerged arc welding is adopted to conduct welding on the outside of straight seam submerged arc welding steel pipe;


8. Ultrasonic inspection I: 100% inspection of the inner and outer welds of straight welded pipes and the base metal on both sides of the welds


9. X ray inspection I: 100% X ray industrial TV inspection is carried out on the internal and external welding seams, and the image processing system is adopted to ensure the sensitivity of flaw detection;


10. Diameter enlargement: the full length of arc-welded straight steel pipe is enlarged to improve the dimensional accuracy of steel pipe and the distribution state of internal stress of steel pipe;


11. Water pressure test: the steel pipe after expanding is tested one by one on the water pressure test machine to ensure that the steel pipe meets the standard test pressure. The machine has the function of automatic recording and storage.


12. Chamfering: machining the pipe ends of the pipe after passing the inspection to reach the required size of the pipe ends;


13. Ultrasonic inspection II: ultrasonic inspection shall be carried out one by one to check the possible defects in the production of straight welded steel tubes after diameter enlargement and hydraulic pressure;


14. X-ray inspection II: X-ray industrial television inspection and tube end welding seam photographing shall be conducted on the steel tubes after diameter enlargement and water pressure test;


15. Magnetic particle inspection of pipe end: conduct this inspection to find defects of pipe end;


16. Anticorrosion and coating: qualified steel pipes shall be anticorrosion and coating according to user requirements