At present, the advanced LSAW (submerged arc welding) steel pipe production processes mainly include JCOE forming and UOE forming. The following is a detailed introduction:

JCOE molding process

1. Plate probing: After the steel plate for manufacturing large-diameter LSAW Steel Pipes enters the production line, the entire plate is first subjected to ultrasonic inspection to detect whether there are defects inside the steel plate.

2. Edge milling: Double sided milling is performed on the two edges of the steel plate using an edge milling machine to achieve the required plate width, plate edge parallelism, and groove shape, preparing for subsequent welding and forming.

3. Pre bending edge: Use a pre bending machine to pre bend the edge of the board, making it have the required curvature for subsequent forming.

4. Forming: On the JCO forming machine, half of the pre bent steel plate is first subjected to multiple step stamping to press it into a "J" shape, and then the other half is similarly bent and pressed into a "C" shape, finally forming an open "O" shape.

5. Pre welding: The formed straight seam welded steel pipe is welded together and continuously welded using gas shielded welding (MAG) to preliminarily fix the steel pipe.

6. Internal welding: Longitudinal multi wire submerged arc welding (about four wires) is used to weld inside the straight seam steel pipe, forming high-quality internal welds.

7. External welding: Longitudinal multi wire submerged arc welding is performed on the exterior of the steel pipe to ensure the quality and strength of the weld seam together with the internal weld seam.

8. Ultrasonic testing: Conduct 100% ultrasonic testing on the internal and external welds and both sides of the base metal of the straight seam welded steel pipe to check for defects in the welds.

9. X-ray inspection: X-ray industrial television is used for 100% inspection of internal and external welds, and an image processing system is used to ensure the sensitivity of the inspection.

10. Diameter expansion: Expand the entire length of the straight seam steel pipe after submerged arc welding to improve the dimensional accuracy of the steel pipe and improve the internal stress distribution of the steel pipe.

11. Hydraulic test: Conduct root diameter test on the expanded steel pipe on the hydraulic testing machine to ensure that the steel pipe meets the standard requirements. The testing machine has automatic recording and storage functions.

12. Chamfering: Inspect and process the end of the steel pipe to achieve the required pipe end groove size.

UOE Forming Process

1. Plate probing: Similar to JCOE process, conduct full plate ultrasonic inspection on steel plates entering the production line.

2. Milling: The edge of the steel plate is machined by a milling machine to ensure that the width, parallelism, and groove shape of the plate meet the requirements.

3. Pre bending edge: Use a pre bending machine to pre bend the edges of the steel plate, so that the curvature of the plate edge meets the forming requirements.

4. Forming: The steel plate is first pre bent at the edge, then pressed into a U-shape by a U-shaped press, and then pressed into an O-shape by an O-shaped press to form a pipe blank.

5. Internal welding: The submerged arc welding process is used to weld inside the pipe blank, forming an internal weld seam.

6. External welding: Submerged arc welding is performed on the outside of the pipe blank to complete the welding of the external weld seam.

7. Mechanical cold expansion: By mechanically expanding the welded steel pipe, the dimensional accuracy and quality of the steel pipe are improved, and the stress distribution is improved.

8. Non destructive testing: including ultrasonic testing, X-ray testing, etc., comprehensively testing the welds and base materials of steel pipes to ensure the quality of steel pipes.

9. Hydrostatic test: Conduct a hydrostatic test on steel pipes to inspect their strength and sealing performance.

Both processes have their own characteristics. JCOE forming process has the advantages of strong process adaptability and low operating costs, and is currently one of the mainstream forming processes for LSAW steel pipe production. The steel pipes produced by UOE forming process have good quality and high production efficiency, but the operating costs are relatively high.

In addition to the JCOE and UOE forming processes mentioned earlier, there are other advanced production processes and related technological improvements for LSAW steel pipes, as follows:

HME molding process

Introduction: It is formed by the core rod rolling method according to "C-C-O", then welded, and finally subjected to processes such as cold expansion. This process has certain advantages in the production of steel pipes with specific specifications and requirements, and can produce high-quality LSAW steel pipes.

Features: By rolling and forming with a core rod, the internal quality and dimensional accuracy of the steel pipe are well controlled, which can effectively improve the internal structure and properties of the steel pipe, and enhance its strength and toughness. However, the equipment and technical requirements of this process are high, and the production efficiency is relatively low. It is usually used to produce special steel pipes with extremely high quality requirements.

Improvement of Welding Technology

Multi wire submerged arc welding technology: In the production of LSAW steel pipes, multi wire submerged arc welding technology has been widely used. This technology uses multiple welding wires for simultaneous welding, greatly improving welding speed and production efficiency, while also better controlling the shape and quality of the weld seam, making the penetration depth and width of the weld seam more uniform, and reducing the occurrence of welding defects.

Double wire hot wire TIG welding (tungsten inert gas welding) base welding technology: For some LSAW steel pipes with high requirements for the quality of the weld root, double wire hot wire TIG welding base welding technology will be used. This technology can provide better penetration and forming during root welding, reduce root defects, and improve the overall quality of the weld seam. Then, combined with submerged arc welding for filling and cover welding, high-quality welds can be achieved.

The Development of Quality Inspection Technology

Automated non-destructive testing technology: Advanced automated non-destructive testing equipment such as phased array ultrasonic testing, digital radiographic testing, etc. are used to comprehensively, quickly, and accurately detect the welds and base materials of steel pipes. These technologies can detect smaller defects, improve detection sensitivity and reliability, and enable automatic recording and analysis of detection data, facilitating quality traceability and management.

Online detection and quality control: Multiple online detection points are set up on the production line to monitor the size, shape, weld quality, and other parameters of steel pipes in real time. Once abnormal situations are found, adjustments or shutdowns are immediately carried out to ensure the stability and consistency of product quality. At the same time, by establishing a quality control system and feeding back detection data into the production process, optimization and adjustment of the production process can be achieved, continuously improving product quality.

Innovation in Materials and Anti corrosion Technology

Application of high-strength steel: With the continuous improvement of performance requirements for steel pipes in fields such as oil and gas transportation, the application of high-strength steel in LSAW steel pipe production is becoming increasingly widespread. For example, high-strength steels such as X80 and X100 have higher strength and toughness, can withstand higher pressure and harsh working environments, reduce the wall thickness and weight of steel pipes, lower costs, and improve transportation efficiency.

The development of anti-corrosion coating technology: In order to improve the corrosion resistance of LSAW steel pipes in different environments, various new anti-corrosion coating technologies are constantly emerging. Such as double-layer fusion bonded epoxy powder coating, polyethylene coating, polyurea coating, etc., these coatings have good adhesion, corrosion resistance, and wear resistance, which can effectively protect steel pipes from external environmental erosion and extend the service life of steel pipes.