ASTM A671 EFW Pipes & Tubes

ASTM A671 - Standard Specification for Electric Fusion Welded Steel Pipe for Atmospheric and Lower Temperatures

ASTM A671 is a standard developed by the American Society for Testing and Materials (ASTM International). This standard applies to steel pipes manufactured by the electric fusion welding (EFW) process, mainly used in pressure vessels, piping systems and other critical applications in normal and low temperature environments.

Scope of application:
Pressure pipes, storage tanks, etc. used for low or normal temperature services, commonly used in oil, gas, chemical and other industries.
The working temperature is usually not less than -50°F (-45°C), depending on the steel grade and impact test requirements.

Different grade categories (such as CL22) are divided according to manufacturing processes, inspection requirements and allowable stress levels, and have strict requirements on welding quality, non-destructive testing, etc.

Specifications and materials:
Outer diameter: ≥16 in.(406mm)

Wall thickness: ≥1/4 in.(6.4mm)

Material grades:
The standard includes several carbon steel and low alloy steel grades (such as CL15, CL16, CL20, CL22, etc.), and the number represents the minimum yield strength (unit: ksi, i.e. thousand pounds per square inch).

For example: CL20 means the minimum yield strength is 20 ksi (about 138 MPa).

A671 CC60 is a common carbon steel with specific carbon, silicon and manganese contents. A671 CC65 and CC70 are also common carbon steels, while A671 CD70 is a manganese silicon steel. The A671 standard also covers nickel steels, such as A671 CF66 and CF71.

Chemical composition:

ASTM A671 steel pipe is made of pressure vessel quality steel plate. Different grades have different chemical composition requirements, but usually include the following key elements control:

Carbon (C): affects strength and weldability, usually controlled in a lower range (such as ≤0.23%).
Manganese (Mn): improves strength and toughness, common range 0.79-1.3%.
Silicon (Si): used for deoxidation, usually 0.13-0.45%.
Sulfur (S) and phosphorus (P): strictly limited (≤0.035%) to avoid hot and cold brittleness.

Other alloying elements (such as Ni, Cr, Mo, V, etc.): some grades may be added to improve low temperature toughness.

Mechanical properties:

Steel pipes under ASTM A671 standard are usually made of carbon-manganese-silicon steel materials with good strength and toughness. For specific material grades, such as "GR.CC 60", "GR" stands for grade, "CC 60" indicates the type and strength grade of the material, and "60" may represent the yield strength of the material, which is approximately equivalent to 415 MPa‌.

The mechanical properties of ASTM A671 steel pipes depend on the grade (such as CC60, Gr.65) and the heat treatment category (such as CL22, CL32), mainly including:

Yield Strength (YS): Minimum requirement (such as ≥220 MPa or higher).
Tensile Strength (TS): Usually 415-555 MPa (such as CC60).
Elongation: ≥21% (measures the ductility of the material).
Impact toughness (some grades need to meet low-temperature impact tests, such as Charpy V-notch test at -45°C).

Manufacturing process:
The steel plate is formed into a round tube by J (Joggle)-C (Crimp)-O (Open)-E (Expand) multi-step forming.
The steel pipe is welded by electric fusion welding (EFW) process, and the welds are subject to 100% radiographic testing (RT) or other non-destructive testing (NDT) to ensure quality.
The welding process requires strict control of current, voltage, and welding speed to ensure weld quality.

Test requirements:
Hydrostatic test: Each steel pipe is subject to hydraulic pressure test.
Non-destructive testing (NDT): The welds are subject to radiographic or ultrasonic testing.
Impact test (optional): Depending on the temperature requirements, a Charpy V-notch impact test may be required.

Differences from other standards:
Similar standards such as ASTM A672 (for high-pressure and high-temperature electric fusion welded pipes), while ASTM A671 focuses more on low-temperature applications.
Unlike seamless pipe standards (such as ASTM A106), A671 is a welded pipe, but it is strictly tested to ensure strength.

Common application:
Cryogenic liquefied gas (LNG) pipelines
Petroleum refining equipment

Cryogenic pressure vessels in the chemical industry

Read more: SAW vs ERW and EFW Welded Steel Pipe or Carbon Steel EFW Pipe