Seamless pipe, welded pipe, and spiral welded pipe are the three most common types. They may appear similar in appearance, but the differences are profound in essence, with the core distinction indeed stemming from manufacturing processes.
Comparison Table：
| Feature Dimension | Seamless Steel Pipe | Longitudinally Welded Pipe | Spiral Welded Pipe |
|---|---|---|---|
| Manufacturing Process | Solid billet piercing and rolling, no weld seam. | Steel plate/sheet is curved and welded along a longitudinal straight seam. | Steel strip is coiled at a spiral angle, forming a continuous helical weld seam. |
| Core Advantages | Uniform wall thickness, high pressure-bearing capacity, isotropic mechanical properties. | High production efficiency, relatively low cost, high dimensional accuracy. | Extreme diameter flexibility, can produce large-diameter pipes from narrower strip, relatively uniform pressure distribution. |
| Main Disadvantages | High cost, limited production specifications (diameter & length), difficult to produce very thin walls. | Contains a long straight weld seam, which is a potential weak point. | Longest total weld length, significant residual stresses, relatively lower dimensional accuracy. |
| Typical Applications | High-pressure, high-temperature, high-reliability scenarios: boiler tubes, hydraulic cylinder barrels, geological drill pipes, petrochemical cracking tubes, high-precision mechanical components. | Medium/low-pressure fluid transport, structural support: construction scaffolding, water/gas supply pipes, mechanical structures, automotive drive shafts. | Large-diameter transport pipelines & structural tubes: municipal drainage, stormwater pipes, wind turbine towers, piling pipes, long-distance low-pressure fluid transport (e.g., water, slurry). |
| Cost | Highest | Lower | Medium (cost-advantageous for large diameters) |
1. Seamless Pipe: No Weld, Uniform Performance
What Is a Seamless Pipe?
A seamless pipe is manufactured without any welding seam along the pipe body. It is produced by piercing a solid round steel billet, forming a hollow tube that is further processed into the required size.
Seamless Pipe Manufacturing Process
The most common seamless pipe manufacturing methods include:
* Hot Rolling / Hot Extrusion (Main Process)
- Round steel billet heating
- Piercing (Mannesmann piercing process or rotary piercing)
- Rolling and elongation
- Sizing or reducing
- Cooling, straightening, cutting, and inspection
This process is highly efficient and suitable for producing large-diameter and thick-wall seamless steel pipes.
* Cold Drawing / Cold Rolling
- Hot-rolled seamless pipe as raw material
- Pickling and lubrication
- Cold drawing or cold rolling through dies
- Heat treatment to remove internal stress
Cold-finished seamless pipes offer higher dimensional accuracy and smoother surface finish, commonly used for precision applications.
Advantages of Seamless Steel Pipe
Limitations of Seamless Steel Pipes
No weld seam, resulting in uniform mechanical properties
Excellent pressure resistance
Suitable for high-temperature and high-pressure environments
Reliable performance in critical applications
Higher production cost
Lower material utilization
Limited maximum diameter and length compared with welded pipe
Typical Applications of Seamless Pipes
Oil and gas pipelines, boiler tubes, hydraulic cylinders, mechanical structures, power plants, and chemical processing systems.
2. Welded Pipe: High Efficiency and Cost Advantage
What Is a Welded Pipe?
A welded pipe is produced by forming steel plate or steel strip into a tubular shape and then welding the seam along the pipe’s longitudinal axis, creating a straight weld.
Welded Pipe Manufacturing Process
Longitudinal Submerged Arc Welded Pipe (LSAW)
Plate forming by JCOE or UOE process
Internal and external submerged arc welding
Mechanical expansion after welding
LSAW welded pipe is suitable for large diameter and thick wall pipelines with high strength requirements.
High-Frequency Welded Pipe (ERW / HFW)
Continuous forming from steel strip
High-frequency current heats the edges
Pressure welding without filler metal
This process offers high production speed, low cost, and stable quality, making ERW welded pipe one of the most widely used steel pipes.
Advantages of Welded Steel Pipe
High production efficiency
Lower cost compared with seamless pipe
Good dimensional accuracy and surface quality
Flexible diameter production by changing plate width
Limitations of Welded Steel Pipe
Presence of a longitudinal weld seam
Welding quality must be strictly controlled
Diameter limited by plate width and forming equipment
Typical Applications of welded pipe
Structural steel pipe, scaffolding, furniture, low-pressure fluid transmission, oil and gas transmission pipelines, offshore structures, wind power towers.
3. Spiral Welded Pipe: Flexible Solution for Large Diameters
What Is a Spiral Welded Pipe?
A spiral welded pipe is formed by winding steel strip at a specific helix angle and welding along the spiral seam, creating a continuous helical weld around the pipe body.
Spiral Welded Pipe Manufacturing Process
Spiral forming from steel strip
Internal and external submerged arc welding
Fixed-length cutting, weld inspection, hydrostatic testing
Optional pipe expansion
By adjusting the spiral angle, the same strip width can be used to manufacture different pipe diameters, offering excellent flexibility.
Advantages of Spiral Welded Pipe
High material utilization
Suitable for medium to large diameter pipes
Flexible production with lower equipment investment
Weld seam distributes stress more evenly around the pipe
Limitations of Spiral Welded Pipe
Longer weld seam than straight welded pipe
Dimensional accuracy and roundness slightly lower
More complex residual stress distribution
Typical Application of SSAW Pipe
Water transmission, gas pipelines, piling pipes, structural supports, large-diameter low-pressure pipelines, and some onshore oil and gas projects.
Tips for how to choose steel pipes
Pursuing the highest performance and reliability without considering cost? → Choose seamless steel pipe.
For general pressure conveying or structural purposes requiring standard dimensions and cost-effectiveness? → Choose straight seam welded pipe.
For pipelines requiring extra large diameters (>1 meter) for drainage, ventilation, foundation piles, or low-pressure conveyance, spiral welded pipes are the optimal choice.
Post time: Jan-30-2026