Production technology of straight seam welded pipe

 　　Straight seam welded pipes, steel pipes made of hot-rolled or cold-rolled steel plates or steel strip coils welded on welding equipment, are all called straight seam welded pipes. (The name is given because the welds of the steel pipe are in a straight line).

　　Straight seam steel pipe is a steel pipe whose weld seam is parallel to the longitudinal direction of the steel pipe. Straight seam steel pipes can be divided into high-frequency straight seam steel pipes (ERW tube) and submerged arc welded straight seam steel pipes (LSAW tube) according to the production process. Straight seam welded pipe has simple production process, high production efficiency, low cost and rapid development.

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

　　1. Plate inspection: After the steel plate used to manufacture the large-diameter submerged arc welded straight seam steel pipe enters the production line, the full plate ultrasonic inspection is first carried out;

　　2. Edge milling: double-sided milling of the two edges of the steel plate by a milling machine to achieve the required plate width, plate edge parallelism and bevel shape;

　　3. Pre-bending: Use a pre-bending machine to pre-bend the edge of the board so that the edge of the board has a curvature that meets the requirements;

　　4. Forming: On the JCO forming machine, first half of the pre-bent steel plate is pressed into a "J" shape through multiple stepping steps, 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: Join the formed longitudinally welded steel pipes and use gas shielded welding (MAG) for continuous welding;

　　6. Internal welding: use longitudinal multi-wire submerged arc welding (up to four wires) to weld on the inner side of the straight seam steel pipe;

　　7. External welding: use longitudinal multi-wire submerged arc welding to weld on the outside of the longitudinal submerged arc welded steel pipe;

　　8. Ultrasonic inspection I: 100% inspection of the inner and outer welds of the longitudinally welded steel pipe and the base materials on both sides of the weld;

　　9. X-ray inspection I: 100% X-ray industrial TV inspection of the inner and outer welds, using an image processing system to ensure the sensitivity of flaw detection;

　　10. Diameter expansion: expand the total length of the submerged arc welded straight seam steel pipe to improve the dimensional accuracy of the steel pipe and improve the distribution of the internal stress of the steel pipe;

　　11. Hydraulic test: The expanded steel pipes are inspected one by one 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: Process the pipe ends of the steel pipes that have passed the inspection to meet the required pipe end groove size;

　　13. Ultrasonic inspection Ⅱ: Perform ultrasonic inspection again one by one to check the possible defects of the longitudinally welded steel pipe after the diameter expansion and water pressure;

　　14. X-ray inspection Ⅱ: X-ray industrial television inspection and pipe end weld filming of the steel pipe after the expansion and hydraulic test;

　　15. Tube end magnetic particle inspection: carry out this inspection to find tube end defects;

　　16. Anti-corrosion and coating: Qualified steel pipes are anti-corrosion and coating according to user requirements.

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