Spiral Welded Pipes: A Comprehensive Analysis of Production Processes, Technical Specifications, and Future Development Prospects
Date: 2025/4/23
Category: Metallurgical encyclopedia terms
Views: 64
A spiral welded pipe is a type of pipe where the weld seam is distributed in a spiral pattern relative to the pipe’s axis. It is manufactured by helically winding a strip of low-carbon structural steel or low-alloy structural steel at a specific spiral angle (called the forming angle) to form a pipe blank, followed by welding the seam. This process allows the production of large-diameter pipes using relatively narrow steel strips. Spiral welded pipes are primarily used as transmission pipelines, pipe piles, and structural pipes. Their specifications are denoted by outer diameter × wall thickness, with product ranges spanning outer diameters of 300–3660 mm and wall thicknesses of 3.2–25.4 mm.
Characteristics of Spiral Welded Pipe Production:
A single-width steel strip can produce pipes of various outer diameters.
The pipes exhibit excellent straightness and precise dimensions. The internal and external spiral welds enhance rigidity, eliminating the need for post-welding sizing or straightening.
Facilitates mechanized, automated, and continuous production.
Compared to equipment of similar scale, the production setup is compact, requires less space and investment, and enables rapid construction.
Compared to straight-seam welded pipes of the same size, spiral welded pipes have longer weld seam per unit length, resulting in lower production efficiency.
Production Process:
The raw materials for spiral welded pipes include steel strips and plates. If the thicknesses of spiral welded pipe is above 19mm, steel plates are used.
Strip-based production: To ensure continuous feeding during butt welding of successive coil ends, a loop accumulator or a "flying welding car" is used. The flying welding car completes the entire material preparation process (from uncoiling to butt welding) while moving along a track. When the tail of the current coil is clamped by the rear gripper of the butt welder, the car moves forward at a speed synchronized with the forming-pre-welding machine. After welding, the rear gripper releases, and the car returns to its original position.
Plate-based production: Individual steel plates are first butt-welded into strips offline, then fed into the production line and connected via the flying welding car.
Butt welding is performed using submerged arc welding (SAW) on the inner surface of the pipe. Any incomplete penetration is repaired via external welding after forming and pre-welding. The spiral seam is then internally and externally welded.
Before entering the forming machine, the edges of the strip/plate are pre-bent to a specific curvature based on the pipe diameter, wall thickness, and forming angle. This ensures uniform deformation curvature between the edges and the central region, preventing the "bamboo node" defect (protruding weld seams). After pre-bending, the material undergoes spiral forming and pre-welding. To enhance productivity, one forming-pre-welding line is often paired with multiple internal/external main welding lines, improving weld quality and output.
Pre-welding: Typically employs faster welding methods such as shielded gas arc welding or high-frequency resistance welding for full-length welding.
Main welding: Utilizes multi-electrode submerged arc welding.
Key Development Trends:
As pipeline operating pressures increase, service conditions become harsher, and the demand for extended pipeline lifespans grows, the primary development directions for spiral welded pipes include:
(1)Producing large-diameter, thick-walled pipes to enhance pressure resistance.
(2)Designing new pipe structures, such as double-layer spiral welded pipes. These use steel strips half the wall thickness of a single-layer pipe, offering higher strength and avoiding brittle fracture.
(3)Developing new steel grades and advancing smelting technologies. Controlled rolling and post-rolling heat treatment processes are widely adopted to improve pipe strength, toughness, and weldability.
(4)Expanding coated pipe production. For example, applying anti-corrosion coatings to the inner wall extends service life, improves smoothness, reduces fluid friction resistance, minimizes wax/scale buildup, and lowers maintenance costs.
