I. What Is Welded Steel Pipe?
Welded steel pipe is a type of steel pipe manufactured by forming steel plates or steel strips and then joining the seams using welding processes.
It is widely used in oil and natural gas transportation, building structures, and various industrial piping systems. Characterized by high production efficiency, a wide range of specifications, and relatively low costs, it is one of the most commonly used types of steel pipe in modern industry.
II. Types of Welded Steel Pipes
1. ERW Welded Steel Pipe
ERW (Electric Resistance Welded Pipe) is manufactured by heating the edges of steel strips with high-frequency current and welding them under pressure.
Features:
- Suitable for small- and medium-diameter steel pipes
- Good surface quality and high dimensional accuracy
- High production efficiency and relatively low cost
Common Applications:
- Building structures, fluid conveyance, machinery manufacturing, etc.
2. SSAW Spiral Welded Steel Pipe
SSAW (Spiral Submerged Arc Welded Pipe) is produced by coiling steel strips into a spiral shape and then performing submerged arc welding.
Features:
- Capable of producing large-diameter steel pipes
- Relatively low cost
- Suitable for long-distance transportation
Common Applications:
- Oil and gas pipelines, water conservancy projects, bridge pile pipes, etc.
3. LSAW Longitudinal Submerged Arc Welded Pipe
LSAW (Longitudinal Submerged Arc Welded Pipe) involves forming steel plates and then performing longitudinal submerged arc welding.
Features:
- High strength and excellent pressure-bearing capacity
- Suitable for thick-walled, large-diameter pipes
- Consistent quality and high reliability
Common Applications:
- High-pressure oil and gas pipelines, subsea pipelines, critical engineering structures
III. Specifications and Parameters of Welded Steel Pipes
| Item |
Specification Range |
Description |
| Outside Diameter (OD) |
10 mm – 3000 mm |
ERW is mainly used for small and medium diameters, while SSAW/LSAW can reach large and extra-large diameters |
| Wall Thickness (WT) |
1 mm – 60 mm |
Varies depending on pressure rating and application requirements |
| Length |
3 m – 12 m (or customized) |
Standard fixed lengths or cut to project requirements |
| Steel Grade |
Q235, Q355, API 5L Gr.B, X42–X80 |
Used for different strength and pressure requirements |
| Welding Type |
ERW / SSAW / LSAW |
Three main welding processes |
| Surface Treatment |
Black pipe / Galvanized / Anti-corrosion coating |
Optional coatings such as 3PE, FBE, etc. |
| Standards |
ASTM A53, API 5L, EN 10219, GB/T 3091 |
Common international and domestic standards |
| End Type |
Plain end / Beveled / Threaded / Flanged |
Customized according to connection method |
| Working Pressure |
Low pressure – High pressure |
Depends on material grade and wall thickness design |
IV. Applications of Welded Steel Pipes
Welded steel pipes are widely used across various industries; however, since different projects have varying requirements for pressure, strength, diameter, and corrosion resistance, the selection of pipes also varies accordingly.
1. Oil and Gas Transportation
Recommended Types: SSAW / LSAW
Applications:
- Long-distance oil and gas pipelines
- High-pressure transmission pipelines
- Subsea or complex terrain transportation
Selection Recommendations:
- Medium-to-low pressure, long distances → SSAW spiral welded steel pipes
- High pressure, high-grade projects → LSAW long-seam submerged arc welded steel pipes
- Common Standards: API 5L (X42–X80)
2. Structural Engineering
Recommended Types: ERW / LSAW
Applications:
- Steel structure bracing
- Frame structures
- Bridge and industrial building structures
Selection Recommendations:
- Small to medium-sized structures → ERW welded steel pipes (cost-effective, easy to process)
- Large load-bearing structures → LSAW (higher strength)
3. Water Supply, Drainage, and Municipal Engineering
Recommended Types: ERW / SSAW
Applications:
- Urban water supply networks
- Drainage systems
- Wastewater treatment projects
Selection Recommendations:
- Standard municipal water supply → ERW (high cost-effectiveness)
- Large-diameter water transmission pipelines → SSAW (low cost, suitable for large diameters)
4. Petrochemical and Chemical Piping
Recommended Types: LSAW / ERW (depending on pressure)
Applications:
- Transportation of chemical media
- High-temperature fluid piping within plants
Selection Recommendations:
- Low to medium pressure → ERW
- High pressure/highly corrosive environments → LSAW + anti-corrosion coating (3PE/FBE)
5. Pile and Foundation Engineering
Recommended Type: SSAW
Applications:
- Bridge pile pipes
- Seaport wharf pile foundations
- High-rise building foundations
Selection Recommendations:
- Large diameter, low cost → SSAW spiral steel pipes
- Major projects → LSAW (higher load-bearing capacity)
6. Mechanical Manufacturing and Industrial Equipment
Recommended Type: ERW
Applications:
- Mechanical structural components
- Equipment brackets
- Conveyor systems
Selection Recommendations:
- General mechanical applications → ERW (high precision, easy to machine)
V. Welded Steel Pipe Standards
| Standard |
Country/Region |
Main Application |
Features |
| ASTM A53 |
United States |
General fluid transport, structural use |
Widely used, suitable for both ERW and seamless pipes |
| ASTM A500 |
United States |
Structural steel tubing |
High strength, commonly used for structural square and rectangular tubes |
| API 5L |
International (Oil & Gas Industry) |
Oil and natural gas transmission |
High-standard line pipe for high-pressure applications |
| EN 10219 |
Europe |
Cold-formed structural steel tubes |
Used for building and structural engineering |
| EN 10217 |
Europe |
Pressure purpose pipes |
Focus on weld quality and pressure performance |
| GB/T 3091 |
China |
Low-pressure fluid transportation |
Commonly used in water supply and municipal engineering |
| GB/T 9711 |
China |
Oil and gas pipelines |
Equivalent to API 5L, used for energy transportation |
VI. Production Process for Welded Steel Pipes
1. ERW Welded Steel Pipe Production Process
Steel coil uncoiling → Edge trimming → High-frequency forming → High-frequency resistance welding → Internal and external deburring → Heat treatment of welds → Sizing and straightening → Non-destructive testing → Hydrostatic testing → Cutting to length → End finishing → Corrosion protection → Final inspection → Packaging and warehousing
2. SSAW Spiral Welded Steel Pipe Production Process
Steel strip uncoiling → Leveling → Spiral forming → Submerged arc welding (inner weld) → Submerged arc welding (outer weld) → Weld cleaning → Non-destructive testing → Hydrostatic testing → Cutting to length → End finishing → Corrosion protection → Final inspection → Packaging and storage
3. LSAW Longitudinal Submerged Arc Welded Steel Pipe Production Process
Steel plate leveling → Edge milling → UOE/JCOE forming → Pre-bending → Longitudinal submerged arc welding → Internal and external weld bead cleaning → Weld heat treatment (optional) → Non-destructive testing → Hydrostatic testing → Sizing and straightening → Cutting to length → End finishing → Corrosion protection → Final inspection → Packaging and storage
VII. FAQ
1. What is the difference between welded steel pipes and seamless steel pipes? How should one choose between them?
Welded steel pipes are formed by rolling steel plates or strips into a tube and then welding them together, whereas seamless steel pipes are made by piercing a solid steel billet, resulting in a pipe with no weld seams.
Recommendations:
- If used for high-pressure, high-temperature, or critical pressure-bearing systems (such as boilers or deep-well oil and gas applications) → Prioritize seamless steel pipes
- If used for building structures, low- to medium-pressure fluid conveyance, or municipal engineering → Welded steel pipes are more economical and practical
2. What are the differences between ERW, SSAW, and LSAW welded steel pipes?
The main differences lie in their welding processes and applicable scenarios:
- ERW (Resistance Welded Pipe): Small diameter, high precision, suitable for structural applications and low-pressure fluids.
- SSAW (Spiral Welded Pipe): Large diameter, low cost, suitable for long-distance transportation.
- LSAW (Straight Seam Submerged Arc Welded Pipe): High strength, large diameter, specifically for high-pressure pipelines.
Selection Recommendations:
- Small diameter → ERW
- Large diameter, low cost → SSAW
- High-pressure long-distance pipelines → LSAW
3. Which industries are suitable for welded steel pipes?
Welded steel pipes have a wide range of applications, mainly including:
- Oil and natural gas transportation
- Municipal water supply and drainage systems
- Building structures (factories, bridges, steel structures)
- Industrial piping systems
- Power and energy engineering
4. How to judge the quality of welded steel pipes? What are the key indicators?
Judging the quality of welded steel pipes mainly involves the following aspects:
- Weld quality (uniformity, absence of cracks)
- Dimensional accuracy (outer diameter, wall thickness deviation)
- Mechanical properties (tensile strength, yield strength)
- Non-destructive testing (UT/RT testing)
- Pressure testing (hydraulic pressure test)
High-quality steel pipes typically pass API, ASTM, or EN standard certifications.
5. Can welded steel pipes undergo anti-corrosion treatment? What are the methods?
Yes, and it is very important in engineering projects, especially in underground or marine environments.
Common anti-corrosion methods include:
- Hot-dip galvanizing
- Epoxy coating
- 3PE (3-layer polyethylene) anti-corrosion layer
- Black painting protection
Selection recommendations:
- Indoor/General environments → Black pipe or light anti-corrosion
- Underground pipelines → 3PE anti-corrosion
- Highly corrosive environments → Heavy-duty anti-corrosion system
6. How to Select the Right Welded Steel Pipe Specifications for Your Project?
When selecting pipes, you typically need to consider four key parameters:
- Outer Diameter (OD)
- Wall Thickness (WT)
- Length
- Operating Pressure and Media Type
Simple Rules:
- Higher pressure → Larger wall thickness
- Higher flow rate → Larger outer diameter
- Stronger corrosiveness → Higher corrosion resistance
It is recommended to provide operating parameters (pressure, media, temperature) before purchasing so that the manufacturer can recommend the most suitable solution.
