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Rust removal technology and forming technology of straight seam steel pipe

Views: 1     Author: Site Editor     Publish Time: 2022-04-21      Origin: Site

Straight seam steel pipe derusting technology:

In the process of anti-corrosion construction of oil and gas pipelines, the surface treatment of straight seam steel pipe is a key factor determining the service life of pipeline anti-corrosion. According to research by research institutes, the life of the anti-corrosion layer depends on factors such as the type of coating, coating, and construction environment. For the requirements of the surface of the straight seam steel pipe, the surface treatment method of the straight seam steel pipe is continuously improved. The methods of removing the embroidery of the straight seam steel pipe mainly include the following:


1. Cleaning: Use solvents and emulsions to clean the steel surface to remove oil, grease, dust, lubricants, and similar organic substances, but it cannot remove rust, oxide scale, or welding flux, etc. on the steel surface.

2. Pickling: Generally, two methods of chemical and electrolytic pickling are used for pickling. Pipeline anti-corrosion only uses chemical pickling, which can remove oxide scale, rust, and old coatings. Sometimes it can be used as a reprocessing after sandblasting and rust removal. Although chemical cleaning can achieve the cleanliness and roughness of the surface, its anchor pattern is shallow, and it is easy to cause pollution to the surrounding environment.

3. Tool rust removal: mainly use tools such as wire brushes to polish the steel surface, which can remove loose oxide scale, rust, welding slag, etc. The rust removal of hand tools can reach the Sa2 level, and the rust removal of power tools can reach the Sa3 level. If the steel surface adheres to a firm scale of iron oxide, the rust removal effect of the tool is not ideal, and the anchor pattern depth required for anti-corrosion construction cannot be achieved.

Fourth, jet derusting: jet derusting is driven by a high-power motor to drive the jet blades to rotate at a high speed so that abrasives such as steel shot, steel grit, iron wire segments, and minerals are sprayed on the surface of the straight seam steel pipe under the powerful centrifugal force of the motor. Not only oxides, rust, and dirt, but also the required uniform roughness can be achieved under the action of abrasive impact and friction.


After spraying and removing rust, it can not only expand the physical adsorption on the surface of the pipe but also enhance the mechanical adhesion between the anti-corrosion layer and the surface of the pipe. Therefore, jet rust removal is an ideal rust removal method for pipeline corrosion protection. Generally speaking, shot blasting is mainly used for inner surface treatment of pipes, and shot blasting is mainly used for outer surface treatment of straight seam steel pipes.


Introduction of forming technology of straight seam steel pipe:


1. Pre-bending: use a pre-bending machine to pre-bend the edge of the board, so that the edge of the board has the required curvature;

2. Forming: On the JCO forming machine, firstly, half of the pre-bent steel plate is pressed into a "J" shape after multiple step stamping, and then the other half of the steel plate is also bent into a "C" shape, and then an opening is formed. "O" shape.

3. Pre-welding: Make the formed straight seam welded steel pipe joint and use gas shielded welding (MAG) for continuous welding.

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

5. External welding: The longitudinal multi-wire submerged arc welding is used for welding on the outside of the straight seam submerged arc welded steel pipe.

6. Wave inspection I: 100% inspection of the inner and outer welds of the straight seam welded steel pipe and the base metal on both sides of the weld.

7. X-ray inspection Ⅰ: 100% X-ray industrial TV inspection is performed on the internal and external welds, and an image processing system is used to ensure the sensitivity of flaw detection.

8. Diameter expansion: Expand the full length of the submerged arc welded straight seam steel pipe to improve the dimensional accuracy of the steel pipe and the distribution of the internal stress of the steel pipe.

9. Hydraulic test: The expanded steel pipe is tested 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.