Common Knowledge of Straight-Seam Steel Pipe Manufacturing in Nanning

Release date:

2018-07-03

Author:

Source:

Category:

Company News

Based on the manufacturing process, straight-seam steel pipes are classified into high-frequency welded straight-seam steel pipes and submerged-arc welded straight-seam steel pipes. Submerged-arc welded straight-seam steel pipes, in turn, are further divided—according to their forming methods—into UOE, RBE, JCOE, and other types. The following section outlines the forming processes for the two most common types: high-frequency welded straight-seam steel pipes and submerged-arc welded straight-seam steel pipes.

Straight-seam steel pipes can be classified, according to their manufacturing process, into high-frequency welded straight-seam steel pipes and submerged-arc welded straight-seam steel pipes. Submerged-arc welded straight-seam steel pipes, in turn, are further categorized—based on their forming methods—into UOE, RBE, JCOE, and other types. The following sections describe the forming processes most commonly used for high-frequency welded and submerged-arc welded straight-seam steel pipes.
　　Submerged Arc Welding Procedure
　　1. Plate Inspection: After the steel plates used to manufacture large-diameter submerged-arc welded straight-seam steel pipes enter the production line, they first undergo full‑plate ultrasonic testing.
　　2. Edge Milling: The edges of the steel plate are milled on both sides using an edge milling machine to achieve the specified plate width, edge parallelism, and groove profile.
　　3. Pre-bending of edges: Use a pre-bending machine to pre-bend the plate edges, ensuring they achieve the required curvature.
　　4. Forming: On the JCO forming machine, the pre‑bent steel plate is first subjected to multiple incremental stamping operations on one half, shaping it into a “J” profile; the other half of the plate is then similarly bent and formed into a “C” shape, ultimately resulting in an open “O”‑shaped cross‑section.
　　5. Pre-welding: Join the seams of the formed straight-seam welded steel pipe and perform continuous welding using gas-shielded arc welding (MAG).
　　6. Internal Welding: Longitudinal multi-wire submerged arc welding (up to four wires) is used to weld the inner surface of the straight-seam steel pipe.
　　7. External Welding: Longitudinal multi-wire submerged arc welding is used to weld the outer surface of straight-seam submerged-arc welded steel pipes.
　　8. Ultrasonic Testing I: Conduct 100% inspection of both the internal and external welds of straight-seam welded steel pipes, as well as the base metal on either side of the weld.
　　9. X-ray Inspection I: Perform 100% X-ray industrial television inspection on both internal and external welds, utilizing an image-processing system to ensure flaw-detection sensitivity.
　　10. Sizing: The entire length of the submerged-arc-welded straight-seam steel pipe is subjected to sizing to enhance dimensional accuracy and improve the distribution of internal stresses.
　　11. Hydrostatic Testing: Each expanded‑diameter steel pipe is individually tested on a hydrostatic testing machine to ensure it withstands the specified test pressure in accordance with the relevant standards. The machine features automatic recording and data storage capabilities.
　　12. Chamfering: The steel pipes that have passed inspection are processed at their ends to achieve the specified bevel dimensions.
　　13. Ultrasonic Testing II: Conduct ultrasonic testing on each pipe individually to detect any defects that may have developed in the straight-seam welded steel pipes following diameter expansion and hydrostatic pressure testing.
　　14. X-ray Inspection II: Perform industrial television X-ray inspection and radiographic testing of the weld seams at the pipe ends on steel pipes after diameter expansion and hydrostatic pressure testing.
　　15. Magnetic Particle Inspection of Pipe Ends: This inspection is performed to detect defects at the pipe ends.
　　16. Corrosion Protection and Coating: After passing inspection, the steel pipes shall undergo corrosion protection and coating in accordance with the customer’s requirements.