Industrial details of LSAW straight seam double-sided submerged arc welded steel pipe commonly used in industry

Introduction to LSAW straight seam double-sided submerged arc welded steel pipe: LSAW straight seam double-sided submerged arc welded steel pipe is a steel pipe with the weld parallel to the longitudinal direction of the steel pipe. It is usually divided into metric electric welded steel pipe, electric welded thin-walled pipe, transformer cooling oil pipe, etc. The production process of straight seam welded steel pipe is simple, the production efficiency is high, the cost is low, and the development is relatively fast. The strength of spiral welded steel pipe is generally higher than that of straight seam welded steel pipe. It can produce welded steel pipes with larger diameters with narrower billets, and welded steel pipes with different diameters can be produced with billets of the same width. However, compared with straight seam steel pipes of the same length, the weld length increases by 30~100%, and the production speed is lower.

Straight seam steel pipes can be divided into high-frequency straight seam steel pipes and submerged arc welded straight seam steel pipes according to the production process. Submerged arc welded straight seam steel pipes are divided into UOE, RBE, JCOE steel pipes, etc. according to their different forming methods. The following introduces the common forming processes of high-frequency straight seam steel pipes and submerged arc welding straight seam steel pipes.

Submerged arc welding process of LSAW straight seam double-sided submerged arc welded steel pipe

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

2. Edge milling: The two edges of the steel plate are double-sided milled by the edge milling machine to achieve the required plate width, plate edge parallelism, and groove shape;

3. Pre-bending edge: The plate edge is pre-bent by the pre-bending machine so that the plate edge has the required curvature;

4. Forming: On the JCO forming machine, the first half of the pre-bent steel plate is pressed into a "J" shape through multiple-step punching, and then the other half of the steel plate is bent in the same way and pressed into a "C" shape to form an open "O" shape

5. Pre-welding: The formed straight seam welded steel pipe is seamed and continuously welded by gas-shielded welding (MAG);

6. Internal welding: The inner side of the straight seam steel pipe is welded by longitudinal multi-wire submerged arc welding (can be four wires);

7. External welding: longitudinal multi-wire submerged arc welding is used to weld on the outside of the straight seam submerged arc welded steel pipe;

8. Ultrasonic inspection I: 100% inspection of the internal and external welds of the straight seam welded steel pipe and the parent materials on both sides of the weld;

9. X-ray inspection I: 100% X-ray industrial television inspection of the internal and external welds, using an image processing system to ensure the sensitivity of flaw detection;

10. Diameter expansion: The diameter of the submerged arc welded straight seam steel pipe is expanded over the entire length to improve the dimensional accuracy of the steel pipe and improve the distribution of stress inside the steel pipe;

11. Water pressure test: The expanded steel pipes are inspected one by one on a water pressure testing machine to ensure that the steel pipes meet the test pressure required by the standard. The machine has automatic recording and storage functions;

12. Chamfering: The steel pipes that have passed the inspection are processed at the pipe end to achieve the required pipe end groove size;

13. Ultrasonic inspection II: Ultrasonic inspection is performed again on each pipe to check for possible defects in the straight seam welded steel pipe after diameter expansion and water pressure;

14. X-ray inspection II: X-ray industrial television inspection and pipe end weld filming are performed on steel pipes after expansion and water pressure test;

15. Magnetic particle inspection of pipe ends: This inspection is performed to find defects on pipe ends;

16. Anti-corrosion and coating: After passing the test, the qualified steel pipes are subjected to anti-corrosion and coating according to user requirements.