Forming Technology of Submerged Arc Welded Straight Seam Steel Pipe

Straight seam steel pipe is a welded pipe whose weld seam is parallel to the longitudinal direction of the steel pipe. Usually divided into ERW pipe, LSAW pipe, metric electric welded steel pipe, electric welded thin-walled pipe, transformer cooling oil pipe, octg casing and so on. The production process of straight seam welded pipe is simple, the production efficiency is high, the cost is low, and the development is rapid.

According to the production process, straight seam steel pipes can be divided into high frequency straight seam steel pipes (ERW pipes) and submerged arc welded straight seam steel pipes (LSAW pipes). 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 most common forming process of submerged arc welding straight seam steel pipe.

Submerged arc welding process of straight seam steel pipe

1. Plate inspection: After the steel plate used to manufacture large-diameter submerged arc welded straight seam steel pipes enters the production line, the entire plate is firstly inspected by ultrasonic;

2. Edge milling: use the edge milling machine to perform double-sided milling on both edges of the steel plate to achieve the required plate width, plate edge parallelism and groove shape;

3. Pre-bending: Use a pre-bending machine to pre-bend the edge of the plate so that the edge of the plate has a curvature that meets the requirements;

4. Forming: On the JCO forming machine, half of the pre-bent steel plate is stamped multiple times. Press into a "J" shape, then bend the other half of the steel plate into a "C" shape, and finally form an open "O" shape

5. Pre-welding: make the formed straight seam welded steel pipe seam and use gas shielded welding (MAG) for continuous welding;

6. Internal welding: use tandem multi-wire submerged arc welding (up to four wires) to weld on the inside of the straight seam steel pipe;

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

8. Ultrasonic 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;

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

10. 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 improve the distribution of internal stress of the steel pipe;

11. Hydrostatic test: On the hydrostatic testing machine, inspect the expanded steel pipes one by one to ensure that the steel pipes meet the test pressure required by the standard. The machine has automatic recording and storage functions;

12. Chamfering: process the pipe end of the qualified steel pipe to reach the required pipe end bevel size;

13. Ultrasonic inspection Ⅱ: Conduct ultrasonic inspection one by one again to check possible defects of straight seam welded steel pipes after diameter expansion and hydraulic pressure;

14. X-ray inspection Ⅱ: Carry out X-ray industrial TV inspection and filming of pipe end welds on steel pipes after diameter expansion and hydrostatic test;

15. Tube end magnetic particle inspection: This inspection is carried out to find tube end defects;

16. Anti-corrosion and coating: The qualified steel pipes are anti-corrosion and coating according to user requirements.

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