I. What is a welded steel pipe?

Welded steel pipe, also known as welded pipe, refers to steel pipe with a seam on its surface, produced by bending and forming steel strips or steel plates into circular, square, or other shapes and then welding them together. It is a type of pipe widely used in modern industry and construction. Compared to seamless steel pipe, its main advantages include a relatively simple manufacturing process, high production efficiency, lower costs, and a wide variety of specifications and types.

II. Main Types of Carbon Steel Welded Pipe

1. ERW (Electric Resistance Welded) Steel Pipes

Features:

• Manufactured using high-frequency electric resistance welding (ERW)
• Straight weld seams and smooth surfaces
• High dimensional accuracy
• High production efficiency
• Relatively low cost

Common Sizes:

• Primarily small to medium diameters
• Common: 1/2“ to 24”

Main Applications:

• Water supply pipelines
• Natural gas transmission
• Building structures
• Scaffolding
• Fire protection piping
• Machinery manufacturing

Common Standards:

• ASTM A53
• ASTM A500
• EN 10219
• API 5L

2. SSAW Spiral Welded Steel Pipe

Features:

• Uses a spiral forming submerged arc welding process
• The weld seam is spiral-shaped
• Capable of producing large-diameter steel pipes
• High raw material utilization
• Suitable for long-distance transportation

Common Specifications:

• Primarily large diameters
• Common: 219 mm – 3500 mm

Main Applications:

• Oil and gas transportation
• Piling projects
• Water supply and drainage projects
• Offshore engineering
• Bridge structures

Common Standards:

• API 5L
• ASTM A252
• GB/T 9711

3. LSAW Longitudinal Submerged Arc Welded Steel Pipe (LSAW Steel Pipe)

Features:

• Manufactured by forming steel plates and then performing submerged arc welding
• The weld is a longitudinal seam
• High strength
• High pressure-bearing capacity
• Suitable for thick-walled, large-diameter steel pipes

Common Sizes:

• Medium to large diameters
• Common: 406 mm to 1422 mm

Main Applications:

• High-pressure oil and gas transmission
• Subsea pipelines
• Power engineering
• Large-scale structural engineering

Common Standards:

• API 5L
• ASTM A671
• ASTM A672

4. DSAW Double-Sided Submerged Arc Welded Steel Pipe (DSAW Pipe)

Features:

• Double-sided submerged arc welding on both inner and outer surfaces
• High-quality welds
• Excellent weld strength
• Suitable for high-pressure environments

DSAW typically includes:

• LSAW (Longitudinal Submerged Arc Welding)
• SSAW (Spiral Submerged Arc Welding)

Main Applications:

• Long-distance transmission pipelines
• Oil and gas engineering
• High-pressure fluid conveyance

5. Comparison of Different Types of Welded Steel Pipes

Type	Weld Seam Type	Main Features	Suitable Applications
ERW	Straight Seam	High dimensional accuracy, low cost	Construction, fluid transportation
SSAW	Spiral Weld Seam	Large diameter, cost-effective	Water transmission, piling, oil & gas
LSAW	Longitudinal Submerged Arc Weld	High strength, thick wall	High-pressure oil & gas transmission
DSAW	Double Submerged Arc Weld	High welding quality	Long-distance pipelines

III. Common Materials for Welded Steel Pipes

Material Grade	Chinese Name	Features	Main Applications
Q195	Low Carbon Steel	Low strength, good plasticity, easy to form	General structure, low-pressure piping, guardrails
Q235B	Mild Carbon Structural Steel	Most widely used, cost-effective, good weldability	Construction structures, scaffolding, low-pressure pipelines
Q355B	Low Alloy High Strength Steel	High strength, strong load-bearing capacity	Bridges, steel structures, mechanical engineering
ASTM A53 Gr.B	American Standard Carbon Steel Pipe	Stable performance, wide application range	Water, gas, oil transmission and structural use
ASTM A106 Gr.B	High Temperature Carbon Steel	Good high-temperature resistance	High-temperature fluid transport, industrial pipelines
API 5L Gr.B	Pipeline Steel	Balanced strength and toughness, good pressure resistance	Oil and gas long-distance pipelines
API 5L X42 / X52 / X60	High Grade Pipeline Steel	Higher strength grades, suitable for high-pressure conditions	High-pressure oil & gas transmission, long-distance pipelines
EN S235JR	European Structural Steel	General structural steel	Construction and general engineering structures
EN S355JR	High Strength European Steel	Higher strength and good toughness	Heavy structures, bridge engineering
ST37 / ST52	German Standard Steel	Stable overall performance	Mechanical structures, industrial pipelines

IV. Welded Steel Pipe Specifications and Parameters Table

Item	Specification Range	Description
Product Type	ERW / SSAW / LSAW / DSAW	Different welding processes
Outside Diameter (OD)	21.3 mm – 3500 mm	From small diameter to extra large diameter available
Wall Thickness (WT)	1.2 mm – 40 mm+	Customized according to pressure rating and application
Length	5.8 m / 6 m / 11.8 m / 12 m / Customized	Standard lengths or as per customer requirements
Steel Grade (Material)	Q195 / Q235 / Q355 / ASTM A53 / API 5L etc.	Common carbon steel and pipeline steel grades
Production Standard	ASTM / API 5L / EN / GB / DIN	Complies with international standards
Surface Treatment	Black / Anti-rust oil / Galvanized / 3PE / FBE	Different anti-corrosion options for various environments
End Finish	Plain end / Beveled / Threaded / Flanged	For welding or connection purposes
Manufacturing Process	ERW (High Frequency Welding) / SAW (Submerged Arc Welding)	Selected based on diameter and application
Inspection Standard	UT / RT / Hydrostatic Test	Non-destructive testing and pressure testing
Certification	ISO / CE / API 5L / SGS	International quality certifications

V. Production Process for Welded Steel Pipes

1. ERW (Electric Resistance Welding) Steel Pipe Production Process

Steel coil uncoiling → Leveling → Slitting → Forming → High-frequency welding → Internal and external deburring → Cooling → Sizing → In-line non-destructive testing (UT) → Cutting to length → Hydrostatic testing → End finishing → Final inspection → Packaging

2. SSAW (Spiral Submerged Arc Welding) Steel Pipe Production Process

Steel strip uncoiling → Leveling → Spiral forming → Internal and external submerged arc welding → Internal and external weld finishing → Ultrasonic testing (UT) → Radiographic testing (RT) → Hydrostatic testing → Expanding → Corrosion protection treatment → End processing → Final inspection → Packaging

3. LSAW (Linear Submerged Arc Welding) Steel Pipe Production Process

Steel plate inspection → Cutting → Edge milling → JCOE/UOE forming → Pre-bending → Internal and external submerged arc welding → Weld correction → Expanding → Heat treatment → Non-destructive testing (UT/RT) → Hydrostatic testing → End machining → Corrosion protection → Final inspection → Packaging

4. DSAW Double-sided Submerged Arc Welded Steel Pipe Process Flow

Steel Plate Cutting → Forming → Internal and External Submerged Arc Welding → Weld Bead Trimming → Ultrasonic Testing (UT) → Radiographic Testing (RT) → Hydrostatic Testing → Expanding → Corrosion Protection → End Machining → Final Inspection → Packaging

VI. Main Applications of Welded Carbon Steel Pipe

1. Construction & Structural Use

Common Applications:

• Steel-frame buildings
• Steel frames
• Scaffolding
• Guardrails and fencing
• Sports venue structures
• Factory building structures

Why Use Welded Steel Pipes?

• Low cost, suitable for high-volume applications
• Sufficient strength to meet structural requirements
• Easy to process (cutting, welding, drilling)

Common Types:

• ERW Steel Pipe
• Q235 / Q355 Grade

2. Fluid Transportation Engineering (Water / Gas / Fluid Transportation)

Common Applications:

• Drinking water supply pipelines
• Industrial circulating water systems
• Air compression pipelines
• Low-pressure gas transmission
• Drainage and sewage systems

Key Requirements:

• Good sealing performance
• Smooth inner walls
• Moderate pressure
• Corrosion protection is critical

Common Types:

• ERW Steel Pipe (Low-to-medium pressure)
• SSAW Steel Pipe (Large-Diameter Water Transmission)
• Galvanized Steel Pipe / Corrosion-Resistant Steel Pipe

3. Oil and Gas Pipeline

Common Applications:

• Long-distance oil pipelines
• Natural gas transmission
• Urban gas distribution networks
• Oilfield gathering and transportation systems

Engineering Characteristics:

• High pressure
• Long-distance transmission
• Extremely high safety requirements
• Must comply with international standards (API 5L)

Common Types:

• LSAW Steel Pipe (High-Pressure Trunk Lines)
• SSAW Steel Pipe (Medium- and Low-Pressure or Large-Diameter)
• API 5L X42 / X52 / X60 / X70

4. Piling & Foundation Engineering

Common Applications:

• Bridge pile foundations
• Port and wharf pile pipes
• Offshore platform foundations
• Deep foundation engineering for buildings

Key Requirements:

• Compressive strength
• Impact resistance
• Ability to withstand soil pressure
• Capability to handle large diameters

Common Types:

• SSAW Spiral Steel Pipe
• Large-diameter thick-walled steel pipes

5. Machinery & Equipment

Common Applications:

• Structural components for machinery and equipment
• Conveying equipment
• Industrial brackets
• Agricultural machinery
• Fitness equipment

Features:

• High dimensional accuracy requirements
• High surface quality requirements
• Easy to machine

Common Types:

• ERW Steel Pipe
• Small-diameter precision welded pipe

6. Municipal Engineering

Common Applications:

• Urban water supply systems
• Drainage systems
• Heating networks
• Underground utility tunnels

Features:

• Long service life
• High corrosion resistance requirements
• Easy installation and maintenance

Common Types:

• SSAW (large-diameter water transmission)
• ERW (branch networks)
• Corrosion-resistant steel pipes (3PE / FBE)

7. Marine & Special Projects

Common Applications:

• Subsea pipelines
• Seawater conveyance
• Offshore platform structures
• Salt fog environment engineering

Characteristics:

• Highly corrosive environments
• High corrosion protection requirements
• High structural safety standards

Common Types:

• LSAW / DSAW
• 3PE coated steel pipes

VII. Why Choose a Chinese Welded Steel Pipe Supplier?

1. Cost Advantage

China boasts a complete steel industry chain with low raw material and manufacturing costs, resulting in more competitive overall prices that are ideal for bulk purchases and engineering projects.

2. High-Volume Production Capacity

With mature ERW, SSAW, and LSAW production lines, we can reliably supply large-diameter pipes and fulfill high-volume orders to meet the demands of large-scale engineering projects.

3. Extensive Export Experience

With a long history of exporting to global markets, we are well-versed in international standards such as ASTM, API, and EN, as well as export procedures, ensuring efficient communication and delivery.

4. Fast Delivery

We maintain ample inventory of standard specifications and operate a mature production system, enabling short lead times and making us well-suited for urgent projects.

5. Custom Processing Capabilities

We support customization of outer diameter, wall thickness, and length, and provide processing services such as cutting, chamfering, galvanizing, and 3PE anti-corrosion coating.

6. International Certification Support

We can provide certifications including ISO, API 5L, CE, and SGS to meet international engineering and bidding requirements.

VIII. Quality Inspection Standards for Welded Steel Pipes

Inspection Item	Inspection Standard / Method	Purpose	Description
Visual Inspection	Visual check	Check surface defects	Detect cracks, dents, scratches, rust, etc.
Dimensional Inspection	Caliper / Micrometer / Diameter gauge	Ensure dimensional accuracy	OD, wall thickness, length, ovality
Chemical Composition Analysis	Spectrometer	Verify material composition	Ensure compliance with Q235 / API 5L etc.
Mechanical Properties Test	Tensile test / Impact test	Test strength and toughness	Tensile strength, yield strength, elongation
Hydrostatic Test	High-pressure water test	Check pressure resistance	Ensure no leakage or deformation
Ultrasonic Testing (UT)	Ultrasonic Testing	Detect internal defects	Check internal weld defects such as cracks or pores
Radiographic Testing (RT)	Radiographic Testing	Weld quality inspection	Used for high-standard pipeline projects
Eddy Current Testing (ET)	Eddy Current Testing	Surface defect detection	Commonly used for online ERW pipe inspection
Weld Inspection	UT / RT / Visual inspection	Ensure welding quality	Focus on weld seam integrity
Coating Inspection	Thickness gauge / Adhesion test	Check anti-corrosion performance	For coatings such as 3PE / FBE
End Inspection	Visual + measuring tools	Ensure connection accuracy	Plain ends, beveled ends, threaded quality
Third-Party Inspection	SGS / BV / TPI	International quality certification	Customer-designated third-party inspection

IX. FAQ

Q1: What types of welded steel pipes can Chinese suppliers provide?

Chinese suppliers can produce a full range of welded steel pipes, including ERW (Electric Resistance Welded), SSAW (Spiral Submerged Arc Welded), LSAW (Longitudinal Submerged Arc Welded), and DSAW pipes. These cover small-diameter structural pipes to large-diameter oil and gas transmission pipes. This wide product range allows buyers to source different pipe types from a single supplier, reducing procurement complexity.

Q2: Why are Chinese welded steel pipes cost-competitive?

The main reason is the complete industrial chain in China, from steel production to pipe manufacturing and coating. Large-scale production, automated equipment, and efficient logistics also reduce unit costs. For buyers, this means lower overall project cost without necessarily compromising on international standards like API or ASTM.

Q3: Can China welded steel pipe suppliers meet international standards?

Yes. Most professional suppliers can produce pipes according to ASTM, API 5L, EN, and ISO standards. Many factories also hold certifications such as ISO 9001, API 5L monogram license, and third-party inspection reports (SGS or BV), which are widely accepted in global engineering projects.

Q4: What industries commonly use welded steel pipes from China?

Chinese welded steel pipes are widely used in construction, water supply systems, oil and gas pipelines, piling projects, shipbuilding, and industrial machinery. SSAW pipes are often used for large-diameter water and piling projects, while LSAW pipes are preferred for high-pressure oil and gas pipelines.

Q5: How do Chinese suppliers ensure product quality?

Quality control typically includes raw material inspection, dimensional checks, chemical composition testing, mechanical property testing, hydrostatic testing, and non-destructive testing (UT/RT). Many suppliers also allow third-party inspections before shipment to ensure compliance with project requirements.

Q6: What should buyers prepare before ordering from a Chinese supplier?

Buyers should clearly define pipe specifications such as outer diameter, wall thickness, steel grade, standard, length, and coating requirements. It is also important to confirm application conditions (pressure, temperature, environment) to ensure the supplier recommends the correct pipe type and grade for the project.