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ERW Carbon Steel Boiler Pipes

OD Range :

21.3 – 508 mm (21.3, 26.9, 33.7, 48.3, 60.3, 76.1, 89, 114.3, 168.3, 219.1, 273, 323.9, 355.6, 406, 508)

WT Range :

2.5 – 16 mm

Length :

6 – 12m

Tolerance :

Outer diameter ±1%, wall thickness ±10%

Material :

20#、Q235、A106 Gr.B、ASTM A53 Gr.B

Standard :

GB/T 3091-2008, ASTM A53, ASTM A106, EN 10219

Surface :

Black paint, hot-dip galvanizing, rust-inhibiting paint

Application :

Boilers, steam pipes, hot water pipes, industrial pressure pipelines

Introduction :

ERW carbon steel boiler tubes are electrically resistance welded steel pipes, featuring high strength, good pressure resistance, and precise dimensions. They are widely used in industrial boilers and high-pressure steam piping systems.

I. Overview of Resistance Welded Carbon Steel Boiler Tubes

Resistance welded carbon steel boiler tubes are a type of carbon steel tubing produced through a resistance welding process. They are characterized by strong welds, precise dimensions, and excellent pressure resistance.
These tubes are widely used in boilers, steam pipes, hot water pipes, and industrial pressure piping systems, and are suitable for medium-to-low pressure to high-pressure applications.

Characteristics of Resistance Welded Carbon Steel Boiler Tubes:

Utilulates advanced resistance welding technology, resulting in strong and reliable welds.
High pipe diameter accuracy and uniform dimensions, making installation easy.
Possesses excellent pressure resistance, suitable for medium, low, and high-pressure boilers.
Available in 20#, Q235, and ASTM standard steel grades, ensuring stable performance.
Surface can be treated with anti-rust paint or hot-dip galvanizing for strong corrosion resistance.
Weldable and bendable, with excellent processing performance.
Cost-effective, suitable for industrial boilers and steam piping systems.

II. Introduction to Electric Resistance Welding (ERW) Process — ERW Carbon Steel Boiler Tubes

Electric Resistance Welding (ERW) is a process that welds steel strips or plates into tubes using resistance heating and pressure. This process is the core method for producing electric resistance welded carbon steel boiler tubes, and its principles and characteristics are as follows:

1. Principle

A steel strip is rolled into a tubular blank, and resistance heat is generated at the contact points of the two edges under the action of high-frequency current.
Under the pressure of the pressure rollers, the contact surfaces of the steel strip melt and weld together, forming a strong weld seam.
The weld strength is close to that of the base material, ensuring the safe use of the pipe in high-pressure steam and hot water environments.

2. Process Characteristics

High-speed production: Compared with traditional welded pipe processes, ERW (Electric Resistance Welding) allows for continuous and rapid production, resulting in high efficiency.
High dimensional accuracy: Through shaping and straightening, the pipe has good roundness, straightness, and uniform wall thickness, facilitating installation.
Reliable weld seam: The welding is uniform, with no slag inclusions or cracks inside, meeting the safety requirements for boiler tubes and industrial pipelines.
Cost-effective: It does not require high-temperature piercing or complex processing, making it more economical than seamless pipe production.

3. Application Advantages

ERW carbon steel boiler tubes can withstand medium, low, and high-pressure conditions and are widely used in boilers, steam pipes, hot water pipes, and industrial pressure piping systems.
They are compatible with conventional carbon steel materials such as 20#, Q235, and A53 steel grades, and exhibit stable mechanical properties.
The manufacturing process is easy to control, facilitating non-destructive testing and hydrostatic testing, ensuring the reliability of each pipe.

III. Chemical Composition and Mechanical Properties of Resistance Welded Carbon Steel Boiler Tubes

1. Chemical Composition Table

Steel Grade / Standard	C (Carbon)	Mn (Manganese)	Si (Silicon)	P (Phosphorus)	S (Sulfur)
20# / GB/T 3091	0.17–0.24	0.35–0.65	≤0.35	≤0.035	≤0.035
Q235 / GB/T 3091	0.12–0.20	0.30–0.70	≤0.50	≤0.045	≤0.045
ASTM A53 Gr.B	0.25 max	0.29–1.06	0.10–0.35	0.035 max	0.035 max
ASTM A106 Gr.B	0.30 max	0.29–1.06	0.10–0.35	0.035 max	0.035 max

2. Mechanical Properties Table

Steel Grade / Standard	Tensile Strength (MPa)	Yield Strength (MPa)	Elongation (%)	Impact Toughness KV (J)	Hardness HB
20# / GB/T 3091	375–500	235	≥26	≥27	120–170
Q235 / GB/T 3091	370–500	235	≥26	≥27	120–170
ASTM A53 Gr.B	415–540	≥205	≥30	≥27	130–180
ASTM A106 Gr.B	415–540	≥205	≥30	≥27	130–180

IV. Application Fields of Resistance Welded Carbon Steel Boiler Tubes

1. Boiler Systems

Low-pressure, medium-pressure, and high-pressure steam boilers
Hot water boiler piping
Industrial boiler auxiliary pipelines

2. Industrial Piping Systems

Steam pipelines in chemical plants, pharmaceutical plants, and food processing plants
Hot water and hot oil circulation systems
Pressure piping and process piping for fluid transport

3. Energy and Heating Systems

Steam transportation in power plants and combined heat and power systems
District heating and thermal networks
Industrial steam heating and heat exchange equipment

4. Other Industrial Uses

Pressure pipelines in metallurgy, papermaking, textile, and light industry sectors
Medium and low-pressure liquid transportation pipelines
Heat transfer systems in industrial plants

V. Selection Recommendations for Resistance Welded Carbon Steel Boiler Tubes

1. Select the steel grade based on working pressure and temperature

Low-pressure boilers: 20# or Q235 carbon steel is sufficient.
Medium and high-pressure boilers: ASTM A53 Gr.B, ASTM A106 Gr.B, or corresponding high-strength steel grades.
High-temperature steam conditions: It is recommended to choose heat-treated or low-alloy steel materials to improve high-temperature resistance.

2. Select specifications based on pipe diameter and wall thickness

Outer diameter range: 21.3–508 mm
Wall thickness range: 2.5–16 mm
When selecting wall thickness, consider the design pressure, medium type, and installation environment to ensure a safety margin.

3. Select the surface treatment based on the installation environment:

Indoor dry environment: Black paint anti-rust treatment is optional.
Outdoor or humid environment: Hot-dip galvanizing or anti-rust oil treatment is recommended.

4. Select the pipe type based on welding and processing requirements:

ERW pipes are suitable for welding, bending, and processing into various piping systems.
Pay attention to bending radius specifications to avoid excessive stress on the wall thickness leading to cracking.

5. Inspection and quality requirements:

When purchasing, confirm whether chemical composition, mechanical properties, non-destructive testing, and hydrostatic test reports are provided.
Ensure that the pipe quality meets standards such as GB/T 3091, ASTM A53, and ASTM A106.

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Specifications and dimensions table for resistance welded carbon steel boiler tubes

Inch	Outer Diameter OD (mm)	Wall Thickness WT (mm)	Theoretical Weight (kg/m)	Tolerance
1/2″	21.3	2.0, 2.5, 3.0, 3.5, 4.0	1.30, 1.60, 1.90, 2.20, 2.50	±1% OD, ±10% WT
3/4″	26.9	2.0, 2.5, 3.0, 3.5, 4.0, 4.5	1.70, 2.10, 2.50, 2.90, 3.30, 3.70	±1% OD, ±10% WT
1″	33.7	2.5, 3.0, 3.5, 4.0, 4.5, 5.0	2.60, 3.10, 3.60, 4.10, 4.60, 5.10	±1% OD, ±10% WT
1 1/2″	48.3	3.0, 4.0, 5.0, 6.0, 7.0, 8.0	4.20, 5.50, 6.80, 8.10, 9.40, 10.70	±1% OD, ±10% WT
2″	60.3	3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0	5.20, 6.90, 8.60, 10.30, 12.00, 13.70, 15.40	±1% OD, ±10% WT
2 1/2″	76.1	4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0	8.10, 10.10, 12.10, 14.10, 16.10, 18.10, 20.10	±1% OD, ±10% WT
3″	89.0	4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0	9.50, 11.80, 14.10, 16.40, 18.70, 21.00, 23.30, 25.60	±1% OD, ±10% WT
4″	114.3	4.0–16.0 (increment 1 mm)	13.70–52.10	±1% OD, ±10% WT
6″	168.3	6.0–16.0	26.40–68.40	±1% OD, ±10% WT
8″	219.1	6.0–16.0 (increment 1 mm)	34.30–87.50	±1% OD, ±10% WT
10″	273.0	8.0–16.0	52.40–97.50	±1% OD, ±10% WT
12″	323.9	8.0–16.0	62.40–117.50	±1% OD, ±10% WT
14″	355.6	10.0–16.0	75.20–131.50	±1% OD, ±10% WT
16″	406.0	10.0–16.0	85.00–147.50	±1% OD, ±10% WT
20″	508.0	10.0–16.0	105.00–187.50	±1% OD, ±10% WT

Standards for resistance welded carbon steel boiler tubes

Standard Category	Standard Number	Applicable Scope / Description
Domestic Standard (GB)	GB/T 3091-2008	Steel pipes for thermal pipelines, suitable for pressure boilers, hot water, steam pipelines, and industrial piping. Specifies dimensions, appearance, wall thickness, mechanical properties, chemical composition, etc.
Domestic Standard (GB)	GB/T 6728-2002	Seamless and welded steel pipes for boilers and high-pressure vessels; provides reference for dimensions, tolerances, and mechanical properties.
International Standard (ASTM)	ASTM A53 / A53M	Standard carbon and alloy steel pipes, suitable for boiler pipes, steam, water, and gas transmission; includes ERW (Electric Resistance Welded) pipes.
International Standard (ASTM)	ASTM A106 / A106M	Seamless carbon steel pipes for high-temperature boilers; also suitable for ERW carbon steel pipes in medium- to high-temperature service. Specifies chemical composition, mechanical properties, and dimensional tolerances.
International Standard (EN / ISO)	EN 10219	Welded carbon steel pipes in square, rectangular, and round shapes for structural use; applicable to industrial boilers and pressure piping systems; covers welding and mechanical property requirements.

Instructions

1. GB/T 3091 is the main national standard for ERW carbon steel boiler tubes in China, covering pressure ratings, dimensional tolerances, chemical composition, and mechanical properties.
2. ASTM A53/A106 are commonly used international standards, suitable for export or international projects.
3. EN 10219 standard is mainly used for welded structural tubes, but can also be referenced in the boiler and pressure piping industry.
4. When selecting a standard, it should be determined based on the working pressure, temperature, medium, and project requirements.

Electric Resistance Welding (ERW) Carbon Steel Boiler Tube Production Process:

Raw Material Preparation → Plate Leveling/Coiling → Forming and Rolling → High-Frequency Electric Resistance Welding (ERW) → Weld Seam Shaping and Correction → Tube Straightening → Cutting to Length → Surface Treatment (Black Paint/Anti-rust Oil/Hot-dip Galvanizing) → Inspection (Chemical Composition, Mechanical Properties, Non-destructive Testing, Hydrostatic Testing) → Packaging and Shipment

Process Overview

1. Raw Material Preparation: Select carbon steel strips or plates that meet the standards, such as 20#, Q235, or ASTM standards.
2. Leveling/Coil Slitting: The steel coil is leveled or cut into strips suitable for pipe forming.
3. Forming and Rolling: The steel strip is rolled into a round pipe blank using a forming machine.
4. High-Frequency Resistance Welding (ERW): A high-frequency current is applied to the weld seam of the pipe blank, and pressure is applied to form a strong weld.
5. Weld Seam Shaping and Correction: Ensure the weld seam is flat and uniform, and the weld strength is close to that of the base material.
6. Pipe Straightening: A straightening machine corrects the roundness, straightness, and wall thickness to ensure dimensional accuracy.
7. Cutting to Length: The pipes are cut to the required length according to customer specifications, typically 6–12 meters.
8. Surface Treatment: Anti-rust oil, black paint, or hot-dip galvanizing is applied to improve corrosion resistance.
9. Inspection: Chemical composition analysis, mechanical performance testing, non-destructive testing, and hydrostatic testing are performed to ensure reliable quality.
10. Packaging and Shipment: The pipes are bundled, film-wrapped, or packaged in wooden crates for easy transportation and storage.

Testing standards for resistance welded carbon steel boiler tubes

Inspection Item	Test Method	Purpose / Requirement
Chemical Composition	Spectral analysis / Chemical analysis	Ensure carbon, manganese, silicon, phosphorus, sulfur, and other elements meet the standard (e.g., 20#, Q235, ASTM A53/A106)
Visual Inspection	Visual check / Dimensional measurement	Verify pipe surface is smooth, welds are uniform, and free of cracks, porosity, folds, dents, or other defects
Dimensions & Tolerances	Vernier caliper / OD gauge / Wall thickness gauge	Ensure outer diameter, wall thickness, length, roundness, and straightness meet standard requirements (OD ±1%, wall thickness ±10%)
Mechanical Properties	Tensile testing machine	Test tensile strength, yield strength, and elongation to ensure the steel can withstand boiler and steam pipe pressure
Impact Toughness	Charpy impact test (KV)	Test low-temperature impact toughness to ensure pipes are not brittle under operating temperatures
Nondestructive Testing (NDT)	Ultrasonic testing (UT) / Radiographic testing (RT)	Detect internal and weld defects, such as slag inclusions, porosity, or cracks
Hydrostatic Test	Hydraulic testing	Simulate working pressure to ensure pipe pressure resistance and prevent leakage
Hardness Test	Brinell hardness (HB)	Measure material hardness to reflect strength and wear resistance
Surface Anti-Corrosion Inspection	Visual check / Coating thickness measurement	Verify uniformity and adhesion of anti-rust oil, black paint, or hot-dip galvanizing layer

Instructions

Domestic standards are primarily based on GB/T 3091-2008, while international projects may refer to ASTM A53 / A106.
Testing items cover chemical composition, mechanical properties, dimensions, weld quality, and pressure resistance, ensuring the safety and reliability of the pipes.
All pipes are typically supplied with an inspection report upon delivery, including chemical composition, mechanical properties, non-destructive testing, and hydrostatic test results.
Depending on project requirements, specialized tests such as high-temperature performance testing and anticorrosion coating thickness testing can be added during the purchasing process.

Common FAQs for Selecting ERW Carbon Steel Boiler Tubes

Q1: How to select the appropriate steel grade based on boiler pressure and temperature?

A:
For low-pressure boilers, 20# or Q235 carbon steel is usually sufficient; for medium and high-pressure boilers or steam pipelines, high-strength carbon steel such as ASTM A53 Gr.B or ASTM A106 Gr.B is recommended. High-temperature steam environments require heat-resistant, low-alloy steel to ensure safe operation of the pipes at working temperatures.

Q2: How to choose the outer diameter and wall thickness?

A:
The outer diameter should be determined based on the design pipe diameter and flow rate; the wall thickness needs to be selected based on the pipeline design pressure, medium temperature, and safety factor. The typical wall thickness range for ERW boiler tubes is 2.5–16 mm. Refer to standard pressure tables or consult the manufacturer’s technical department for selection.

Q3: What are the differences between ERW welded pipes and seamless pipes, and which one is more suitable?

A:
ERW welded pipes have strong welds, high dimensional accuracy, and are cost-effective, making them suitable for low-pressure and general high-pressure boiler systems; seamless pipes have higher pressure resistance, but are more expensive and have longer delivery times. The choice depends on the pressure rating and budget.

Q4: How to choose the pipe length and surface treatment?

A:
The standard length is 6–12 meters, and it can be customized according to construction requirements; for surface treatment, black paint is suitable for dry indoor environments, while hot-dip galvanizing or anti-rust oil treatment is recommended for outdoor or humid environments to prevent corrosion and extend service life.

Q5: What precautions should be taken during installation?

A:
Pipe ends should be cut neatly and cleaned before welding; bending pipes should follow the specified bending radius to avoid excessive stress on the pipe wall; a hydrostatic test can be performed after installation to confirm the sealing of the pipeline system.

Q6: How to confirm the reliability of the pipe quality?

A:
When purchasing, you should check the test report, including chemical composition, mechanical properties, non-destructive testing, and hydrostatic test results. Ensure that the pipes meet the requirements of standards such as GB/T 3091 and ASTM A53/A106, and that the welds are uniform, without cracks, holes, or inclusions.