Manufacturing process of large diameter straight seam welded pipes

The manufacturing of large-diameter straight seam welded pipes is a very professional technical process that requires rigorous and complex technical procedures. From the inspection of the initial raw materials to the precision of the production process and the repeated inspection of the final sample steel pipe, all reflect the high quality requirements and strict control of the performance of the welded pipe products. The following is an introduction to the production process of this steel pipe.

1. Raw material inspection
Before making large-diameter straight seam welded pipes, the steel pipe materials used to make welded pipes need to be fully ultrasonically inspected after entering the production line to detect whether the quality of the steel pipe raw materials meets the standards.

2. Milling and pre-bending

After quality inspection, the steel plate is shaped by the milling machine, and the edges on both sides of the steel plate are cut to meet the shape, length, width, parallelism and other standards required by the straight seam steel pipe. The edge side of the steel plate is pre-bent by the pre-bending machine to make the steel plate reach the required bending degree.

3. Stamping and forming
The pre-bent steel plate is stamped using a JCO forming machine, and half of the pre-bent steel plate is repeatedly placed in the stamping operation. During the operation, it is bent into a "J" shape, and the other half of the steel plate is also bent into a "C" shape, and then an open O shape is formed, and the stamping and forming operation is completed.

4. Pre-welding
After completing the previous step, the formed straight seam steel pipe is seamed, and then the steel pipe is continuously welded using a gas shielded welding device.

Internal welding is to complete the welding process on the inside of the steel pipe using a longitudinal multi-wire submerged arc welding device. The same device as the previous step, this time the welding process is performed on the outside of the steel pipe.

5. Sound wave and radiographic inspection
After completing the above process, the steel pipe needs to be inspected using ultrasonic technology, and the gap of the steel pipe welding and the materials on both sides of the welding gap are fully inspected to check whether the process results meet the standards.

6. Radiographic inspection
This operation uses X-ray technology to inspect the steel pipe again, conduct technical surveys on the internal and external welding parts of the steel pipe, and use the X-ray image processing system to check the sensitivity and accuracy of the steel pipe flaw detection.

7. Diameter expansion
This operation improves the dimensional accuracy of the steel pipe itself by expanding the diameter of the steel pipe, and can also achieve the effect of further improving the distribution state of stress in the steel pipe.

8. Water pressure test
The expanded steel pipes are subjected to water pressure test one by one, and this measure makes the steel pipe reach the standard level.

9. Chamfering
After the previous operation, the qualified steel pipes are reprocessed on the pipe end side to meet the dimensional requirements of the pipe section groove.

10. Sound wave inspection
Perform a second ultrasonic inspection, and use ultrasonic inspection to inspect the steel pipes that have passed the above process one by one again, and use more rigorous measures to check whether there are loopholes in the steel pipe.

11. Radiographic and magnetic particle inspection
Perform a second X-ray inspection to check whether there are loopholes in the above measures. Use magnetic particles to inspect the pipe ends of the steel pipes to find out whether there are defects at the pipe ends.

12. Surface coating
The last step is to process the surface of the steel pipe that has passed the quality inspection, and carry out surface anti-corrosion treatment and technical coating according to customer requirements to complete the processing of the outer layer of the steel pipe.

The above is the complete production process of large-diameter straight seam welded pipes. The selection of steel pipes has high technical requirements. Therefore, when purchasing steel pipes, you should choose a regular manufacturer, so that the product quality is more guaranteed.

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