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Summary straight seam steel pipes can be divided into erw steel pipes and lsaw steel pipes according to the production process. Submerged arc welded straight seam steel pipes are further divided into UOE, RBE, JCOE steel pipes according to their different molding methods. The following describes the most common molding processes for high-frequency straight seam steel tubes and submerged arc welded straight seam steel tubes.

Submerged arc welding process
1. Panel inspection: After the steel plate used to manufacture the large-diameter submerged arc welded straight seam steel pipe enters the production line, the whole board ultrasonic inspection is first carried out;
2. Milling edge: double-sided milling the two edges of the steel plate by the edge milling machine to achieve the required plate width, edge parallelism and groove shape;
3. Pre-bend: use the pre-bending machine to pre-bend the edge of the board so that the edge of the board has the required curvature;
4. Molding: On the JCO molding machine, half of the pre-bent steel plate is first stepped and pressed into a “J” shape, and 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: joints of straight seam welded steel pipes after forming and continuous welding by gas shielded welding (MAG);
6. Internal welding: welding by longitudinal multi-wire submerged arc welding (up to four wires) on the inside of a straight seam steel pipe;
7. External welding: welding by longitudinal multi-wire submerged arc welding on the outside of straight seam submerged arc welded steel pipe;
8. Ultrasonic inspection I: 100% inspection of the inner and outer welds of straight seam welded steel pipes and the base metal on both sides of the weld;
9. X-ray inspection I: 100% X-ray industrial TV inspection of internal and external welds, using image processing system to ensure the sensitivity of flaw detection;
10. Expanding diameter: Expanding 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 steel pipe after diameter expansion is tested on the hydraulic testing machine to ensure that the steel pipe meets the test pressure required by the standard. The machine has automatic recording and storage functions;
12. Chamfering: The steel pipe after passing the inspection shall be processed at the end of the pipe to achieve the required pipe end groove size;
13. Ultrasonic inspection II: Ultrasonic inspection is carried out again and again to check for defects that may occur after straightening and water pressure of straight seam welded steel pipes;
14. X-ray inspection II: X-ray industrial TV inspection and tube end weld filming of the steel pipe after the expansion and hydrostatic test;
15. Tube-end magnetic particle inspection: Perform this inspection to find tube end defects; 16. Anti-corrosion and coating: The qualified steel tube is preserved and coated according to user requirements.