The main production process of large diameter straight seam welded pipe

Longitudinal welded pipes are formed by bending steel plates or steel strips and then welding them. According to the weld form, it is divided into straight seam welded pipe and spiral welded pipe(ssaw steel pipe). According to the purpose, it is divided into general welded pipe, galvanized welded pipe, oxygen-blowing welded pipe, wire casing, metric welded pipe, roller pipe, deep well pump pipe, automobile pipe, transformer pipe, electric welded thin-walled pipe, electric welded special-shaped pipe and spiral welded pipe.

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

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

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 by multiple stepping and pressing, and then the other half of the steel plate is also bent and pressed into a "C" shape to form an open "O" shape

5. Pre-welding: Join the formed longitudinally welded steel pipe and use gas shielded welding (MAG) for continuous welding;

6. Internal welding: use longitudinal multi-wire submerged arc welding (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 television 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. Hydrostatic test: The expanded steel pipe is inspected one by one on the hydrostatic 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 end of the qualified steel pipe to reach the required pipe end groove size;

13. Ultrasonic inspection Ⅱ: Ultrasonic inspection is carried out 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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