Steel Pipe

Steel pipe processing and production

1. Cutting

Determine the way of splicing the steel pipe according to the actual size of the steel pipe layout expansion diagram, and lay out with the least splicing method. The layout and numbering should reserve welding shrinkage and processing allowance according to the process requirements. For the oblique steel pipe ends of the steel pipe tower, the inner and outer walls should be laid out and numbered according to the groove requirements.

2. Plate rolling

After the pre-bending test at both ends is qualified, the steel plate is hoisted into the CNC three-roll plate rolling machine. To prevent misalignment, the steel plate should be centered so that the longitudinal center line of the steel plate is strictly parallel to the roller axis. Then use progressive rolling. During the rolling process, the oxide scale that falls off the surface of the steel plate should be continuously swept away to avoid crushing the surface of the steel plate.

3. Rounding

First, round the two ends of the steel pipe. The out-of-roundness is in accordance with the quality inspection requirements. If it does not meet the requirements, it will be adjusted.

4. Welding

The longitudinal seam of the steel pipe is welded by semi-automatic submerged arc welding. Before welding, the longitudinal seam splicing and positioning welding should be carried out. The length of the positioning welding seam should be greater than 40mm, the spacing should be 500~600mm, and the thickness of the positioning welding seam should not exceed 2/3 of the designed weld. Attention should be paid to the plate edge misalignment and weld gap during welding.

5. Heat treatment

In order to ensure that the pipe body weld will not crack, the following measures will be taken for construction: welding is strictly carried out according to the requirements for thick plate welding; post-weld heat treatment is carried out, and the weld is treated with hydrogen removal by electric heating.

6. Anti-corrosion treatment

Anti-corrosion of the inner wall of the pipe: After the surface is cleaned and qualified, apply the PHA106 primer, a special anti-corrosion coating for steel pipes, and then apply the PHA106 topcoat twice. The thickness of the cured paint film is required to be 90-100um. The anti-corrosion of the outer wall of the pipe is divided into the following situations: A. Exposed pipelines: After the surface is cleaned and qualified, apply PHA106, a special anti-corrosion coating for steel pipes, twice, and then apply enhanced anti-ultraviolet PHA106 topcoat twice. The cured paint film is required to be no less than 100um. B. Buried pipelines: After the surface is cleaned and qualified, apply PHA106 primer, a special anti-corrosion coating for steel pipes, twice, and then apply PHA106 topcoat once. The thickness of the anti-corrosion layer is required to be no less than 150um.

7. Quality inspection

Includes non-destructive testing, dimensional inspection, appearance inspection, etc. Non-destructive testing usually uses ultrasonic testing, X-ray testing and other methods to ensure the internal quality of the weld. Dimensional inspection mainly measures the diameter, wall thickness, length, etc. of the steel pipe to ensure that it meets the design requirements. Appearance inspection is to check the defects on the surface of the steel pipe, such as cracks, scratches, pits, etc.