In-depth Analysis of Two Forming Technologies for LSAW
Date:2025-11-12
Core Differences :
JCOE: Employs a progressive, multi-point bending forming method. Its name derives from the forming process (J-Forming, C-Forming, O-Forming, Expanding).
UCOE: Employs an integral, one-step stamping forming method. Its name also derives from the forming process (U-Forming, C-Forming, O-Forming, Expanding).
I. Detailed Explanation of the JCOE Manufacturing Method
The JCOE process is currently the most widely used and technologically mature LSAW pipe manufacturing process globally.
Process Flow:
Steel Plate Pretreatment and Milling: The steel plate is inspected for flaws and leveled. Then, its two edges are milled to ensure subsequent welding quality.
Pre-bending: Before forming, the two long edges of the steel plate are bent using a mold to form the required arc curvature. This step is crucial and effectively prevents defects such as "straight edges" or "banana shapes" from appearing in the formed straight seam pipe.
J-forming: The pre-bent steel plate is placed on a JCOE forming machine. Supported by a series of lower dies and pressed by an upper die, the plate undergoes multiple, small-step progressive bending processes starting from one end, forming a semi-circular arc resembling a "J" shape in the middle.
C-forming: The J-shaped steel plate is flipped 180° and processed from the other side using the same progressive bending method, transforming it from a "J" shape into a "C" shape (more like an open ring).
O-forming: Pressure continues to be applied to the C-shaped steel plate, gradually closing its opening to ultimately form a closed circular (O-shaped) tube. At this point, a suitable gap is left at the joint of the tube, preparing for subsequent welding.
Internal and External Welding: At the joint of the tube, internal welding is performed first, followed by external welding, both using multi-wire submerged arc welding technology to ensure deep, high-quality, and high-strength welds.
Diameter Expansion (E): This is the finishing touch of the entire process. A large expanding machine is used, with an expanding head containing multiple fan-shaped modules inserted into the pipe body. The expansion proceeds sequentially from both ends of the steel pipe towards the center, causing overall plastic deformation of the pipe.
Functions:
Eliminates residual stress from the steel pipe forming and welding process.
Adjusts roundness to extremely high precision, resulting in more uniform dimensions.
Performs "non-destructive testing" of welds; any minute defects may be exposed under the expanding stress.
Increases the overall yield strength of the steel pipe.
II. Detailed Explanation of the UCOE Manufacturing Method
The UCOE process can be seen as an evolution and simplification of JCOE. Its core lies in using the mature O-forming technology of the UOE process, but it is suitable for medium-scale production.
Process Flow:
Steel Plate Pretreatment and Milling: Same as JCOE.
U-forming: This is the most fundamental difference from JCOE. UCOE uses a large U-shaped upper and lower die, pressing the entire flat plate directly into a "U" shape through one or very few powerful stampings. This is a one-piece, rapid forming process.
C-forming: The U-shaped steel plate is moved to the next station, where a C-shaped upper die is used for another high-pressure press, pressing the U-shape into a more circular "C" shape.
O-forming: This step is exactly the same as the O-forming in the UOE process. The C-shaped tube blank is fed into an O-forming machine consisting of two semi-circular dies. The dies close, and the tube blank is pressed into a closed circular (O-shaped) tube in one pass under immense pressure.
Internal and external welding and diameter expansion: Subsequent welding and diameter expansion processes are basically the same as the JCOE process.
Situations where JCOE is chosen:
Diverse product specifications, requiring frequent production changes.
Production of large-diameter, thick-walled, high-grade pipeline pipes, with particular emphasis on residual stress control and dimensional accuracy.
Investment budgets prioritize long-term flexibility and overall benefits.
Situations where UCOE is chosen:
Single product specification, requiring long-term, stable, and large-volume production (e.g., concentrated production of millions of meters of steel pipe of the same specification for a specific pipeline project).
Possessing strong financial resources, it can afford the high costs of mold making.
Its technology is inherited from the mature UOE process, which is extremely efficient in specific high-volume production scenarios.
