Production process of LSAW steel pipe

Date:2024-05-21Tags:LSAW steel pipe, API5CT, steel pipe, JCOE Pipe, UOE Pipe

LSAW steel pipe (Longitudinally Submerged ArcWelding) is a professional term for straight seam submerged arc welded steel pipe, also known as straight seam submerged arc welded pipe, which is a kind of steel pipe. It uses a single medium-thick plate as raw material, presses (rolls) the steel plate into a tube in a mold or forming machine, and then uses double-sided buried fox welding and enlarging the diameter for production. Submerged arc welding (including submerged arc surfacing and electroslag surfacing, etc.) is a method in which the arc burns under the flux layer for welding. Its inherent advantages include stable welding quality, high welding productivity, no arc light, and little smoke and dust. It has become the main welding method in the production of many important steel structures.

LSAW steel pipe

What are the advantages of LSAW steel pipe?

LSAW steel pipe has a longitudinal weld, and both the inner and outer welds are welded by one submerged arc welding. After the overall mechanical diameter expansion treatment, the internal stress of the steel pipe is small and evenly distributed, which can effectively prevent stress corrosion cracking, has high dimensional accuracy and facilitates on-site welding construction. Its finished product specifications range is wide, the toughness, plasticity, uniformity and density of the weld are good, and it has the advantages of large pipe diameter, thick pipe wall, high pressure resistance, low temperature resistance and strong corrosion resistance. Therefore, it is widely used in fields such as petroleum, natural gas and water conservancy projects. Especially when constructing high-strength, high-quality long-distance oil and gas pipelines, most of the steel pipes required are large-diameter thick-walled straight seam submerged arc welded pipes.


Applications and Classification of LSAW pipe

According to API 5CT standards, among large-scale oil and gas transmission pipelines, straight seam submerged arc welded pipes are the only designated applicable pipe type when passing through Class 1 and Class 2 areas such as alpine zones, seabed, and densely populated urban areas. At the same time, according to different forming methods, LSAW steel pipes can be divided into several types such as UOE steel pipes, JCOE steel pipes and HME steel pipes.



LSAW pipe manufacturing process can be divided into UOE process and JCOE process

UOE Pipe Manufacturing Process

UOE is a formingprocessing method used for production of large diameter longitudinally welded pipe.

Three Main Forming Steps of UOE Pipe Forming Process Are As Following:

First, steel plate pre-bending

Second, U forming

Third, O forming

Each step is completed by adopting dedicated forming press in sequence to deform the steel plate into a circular pipe.

 

JCOE Pipe Manufacturing Process

JCOE is a kind of forming process to produce large diameter longitudinally submerged arc welded (LSAW) steel pipe. JCOE process includes the following steps: pre-welding, forming, and cold expanding after welding according to "J-C-O-E".

In JCOE pipe manufacturing process, steel sheet / plate need to be cut to the needed size first and then fed through a series of rollers to be formed into a J shape. Second, trim the edges of the plate to be straight and parallel for welding. Next, through additional steps on the forming machine, forming the plate into a C shape , with some incremental corrections for ovality and straightness. Finally, expand the plate to form the final O shaped pipe blank.



Some detailed production processes of  LSAW pipe

It should be noted that specific steel pipe specifications, materials, production processes, etc. may vary depending on the manufacturer and application area. When selecting and using LSAW steel pipes, evaluation and selection should be based on actual needs and relevant standards. The following are some detailed production processes of LSAW steel pipes:

1.Raw materials entering the factory: Check the specifications, materials, furnace batch numbers, etc. of the purchased steel plates with the quality assurance documents and review the quality assurance documents. Steel plates that do not meet the procurement technical requirements will be rejected.

2.Raw material re-inspection: Sampling the purchased steel plates for chemical composition analysis and physical and chemical property tests (tensile, bending, fracture toughness, etc. tests).

3. Welding process qualification: Develop a welding procedure specification (EWPS) based on the material and thickness of the steel pipe, and implement a welding procedure qualification (PQR) based on the EWPS. In this case, at least two PQRs should be completed, one of which is manual welding (SMAW) for verification. Welding quality and weld repair of manual welding seams; the other is submerged arc welding (SAW) to verify the welding quality of submerged arc welding seams. After all test items are assessed as qualified, the correct feasibility of the welding procedure specification (WPS) will be confirmed based on the welding procedure qualification report (PQR).

4. Cutting and edge milling: CNC flame cutting cuts the material, removes the melt and spatter on the cutting edge, and uses mechanical processing on the surrounding edges of the steel plate to achieve the required plate width, plate edge parallelism and groove shape. , prepare for welding. The maximum allowable deviation in the diagonal dimension of the final steel plate is 0.5mm.

5 .Pre-bending: Use a pre-bending machine to pre-bend the edge of the plate so that the edge of the plate has a required curvature, making the steel pipe look more dimensional and accurate after forming.

6. J-C-0 forming: Using the "JCO" forming method, the steel plate enters the forming position from the road, the steel plate is fixed, and through the relative movement of the upper and lower molds, it is formed in a shape-C shape-0 shape. During the forming process, The steel plate deforms evenly and has small residual stress. The material is discharged after forming to ensure delivery of steel pipes with large straight seams.

7. External welding: Use longitudinal multi-wire submerged arc welding to weld on the outside of the longitudinal submerged arc welded steel pipe.

8. Ultrasonic inspection 1: 100% inspection of the internal and external 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 television inspection of internal and external welds, using an image processing system to ensure the sensitivity of flaw detection.

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

11. Hydraulic pressure test: The expanded steel pipes are inspected one by one on a hydraulic 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: Process the pipe end of the steel pipe that has passed the inspection to achieve the required pipe end bevel size.

13. Ultrasonic inspection II: Carry out ultrasonic inspection one by one again to check possible defects of the straight seam welded steel pipe after diameter expansion and hydraulic pressure test.

14. X-ray inspection II: Carry out X-ray on the steel pipe after diameter expansion and hydraulic pressure test Industrial TV inspection and pipe end weld photography.

15. Pipe end magnetic particle inspection: This inspection is performed to detect pipe end defects.

16. Anti-corrosion and coating: Qualified steel pipes will be anti-corrosion and coated according to user requirements.


BAOWI Steel——Excellent quality, professional manufacturing. We are committed to providing high-quality LSAW steel pipes, strictly following international standards to ensure that each steel pipe has excellent strength, corrosion resistance and precise dimensions. Choosing BAOWI Steel means choosing a reliable partner to provide solid protection for your oil and gas transportation, water conservancy projects and various infrastructure projects. BAOWI Steel helps the global steel industry to create a better future!

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