HomeKnowledgeInstallations & materialsProduction process of large diameter straight seam welded pipe

Production process of large diameter straight seam welded pipe

The steel pipe is mainly divided into a seamless steel pipe and a welded steel pipe, and the welded pipe is formed by bending a steel plate or a steel strip and then welded.

According to the weld form, it is divided into straight welded pipe and spiral welded pipe. According to the purpose, it is divided into general welded pipe, galvanized welded pipe, blown oxygen welded pipe, wire casing, metric welded pipe, idler pipe, deep well pump pipe, automobile pipe, transformer pipe, electric welding thin wall pipe, electric welding special pipe and spiral welded pipe.

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The main production process description of large diameter straight seam welded pipe:

1. Stencil

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, parallelism of the edge of the plate and the shape of the groove.

3. Pre-bending

Pre-bending the edge of the board with a pre-bending machine to make the edge of the board meet the required curvature; 4. Forming: First, half of the pre-bent steel plate is stepped and pressed on the JCO molding machine. In the shape of “J”, the other half of the steel plate is also bent, pressed into a “C” shape, and finally formed an open “O” shape;

5. Pre-welding

the straight seam welded steel pipe after forming is welded and continuously welded by gas shielded welding (MAG).

6. Internal welding

Welding by longitudinal multi-wire submerged arc welding (up to four wire) on the inside of straight seam steel pipe; 7. External welding: using longitudinal multi-wire submerged arc welding on the outside of straight seam submerged arc welded steel pipe welding;

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

On the hydraulic test machine, the steel pipe after the diameter expansion is tested one by one 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 pipe end 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

Carry out this inspection to find the tube end defect;

16. Anti-corrosion and coating

The qualified steel pipe is anti-corrosion and coating according to user requirements.

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