ASTM A671 Electric Fusion Welded Steel Pipe for Lower Temperatures

ASTM A671 electric-fusion-welded steel pipe is manufactured from pressure-vessel-quality carbon or alloy steel plate with filler metal added during welding. It is designed primarily for high-pressure piping systems operating at atmospheric and lower temperatures.

The ASTM A671 grade identifies the pressure vessel plate used for pipe manufacture, while the class number defines the required pipe heat treatment, radiographic examination, and pressure testing condition. Common carbon steel grades include CB60, CB65, CB70, CC60, CC65, and CC70. For lower-temperature pressure piping, the fine-grain CC series manufactured from ASTM A516/A516M plate is frequently specified.

ASTM A671 nominally covers pipe with an outside diameter of 400 mm or larger and wall thickness of 6 mm or greater. Other dimensions may also be supplied when all applicable requirements of the specification are satisfied.

Specifications

Main Features

Grade and Class Are Defined Separately

ASTM A671 does not use the grade alone to define the finished pipe condition.

For example:

ASTM A671 CC60 Class 22

CC60 identifies pipe manufactured from ASTM A516/A516M Grade 60 fine-grain killed carbon steel plate.

Class 22 means:

• Pipe is stress relieved after welding.

• Welds are radiographically examined.

• Pipe is pressure tested.

This grade-plus-class identification is important when specifying pipe for pressure systems because two pipes of the same grade can have different heat-treatment and inspection conditions.

Controlled Large-Diameter Geometry

ASTM A671 establishes dimensional limits appropriate for fabricated pressure pipe:

• Outside diameter tolerance: ±0.5%

• Maximum out-of-roundness: 1%

• Alignment deviation: maximum 3 mm over 3 m

• Minimum wall thickness: not more than 0.3 mm below nominal thickness

• Unmachined length tolerance: -0 / +13 mm

These controls are particularly important for large-diameter field welding, flange alignment, spool fabrication, and circumferential joint preparation.

Defined Weld and Pressure-Test Classes

ASTM A671 provides multiple manufacturing classes so inspection can be matched to project requirements.

Additional precipitation-heat-treatment classes are available for applicable alloy grades.

Our Advantages

1. How Can the Correct ASTM A671 Class Be Confirmed Before Production?

A common procurement risk is specifying only “ASTM A671 CC60” without defining the required class. The grade alone identifies the base plate but does not completely define heat treatment, radiography, or pressure testing.

Before production, the material description can therefore be confirmed in a complete format such as:

ASTM A671/A671M CC60 Class 22

The manufacturing route can then be matched directly to the order:

Pressure vessel plate → forming → EFW welding → stress relieving → radiographic examination → pressure testing → dimensional inspection.

This reduces ambiguity between the purchase order, production route, inspection plan, and material documentation.

2. How Is Weld Integrity Controlled for Pressure Service?

For projects requiring verified weld examination, Classes 11/12, 21/22, 31/32, 41/42, and 51/52 include radiographic examination requirements according to ASTM A671.

Where the corresponding pressure-tested class is ordered, each production batch can also be documented with applicable pressure-test records.

Available inspection documentation can include:

• Material heat number traceability

• Plate material certificates

• Welding procedure identification

• Radiographic examination records

• Pressure-test records

• Mechanical test reports

• Dimensional inspection reports

• Final material inspection certificate

Supplementary NDT or impact testing can be incorporated when required by the project specification.

3. How Are Large-Diameter Pipes Controlled for Site Fit-Up?

Large EFW pipe requires more than nominal OD and wall thickness control. Ovality and longitudinal alignment directly affect circumferential field weld preparation.

Finished pipes are therefore checked against ASTM A671 dimensional limits including:

• OD: ±0.5%

• Out-of-roundness: ≤1%

• Alignment: ≤3 mm over 3 m

• Minimum wall thickness: no more than 0.3 mm below nominal thickness

For fabrication projects, additional dimensional inspection points such as end diameter, end squareness, bevel geometry, circumference, and pipe length can be included in the inspection plan.

Execution Standards

ASTM, EN, JIS, GOST, and GB grades should not be treated as automatically interchangeable. Substitution should be confirmed against chemical composition, mechanical strength, impact-test temperature, welding process, heat treatment, inspection requirements, and applicable pressure design code.

Application

LNG Terminal Low-Temperature Natural Gas Transfer Header

ASTM A671 CC60 or CC65 EFW pipe can be specified for large-diameter low-temperature natural gas transfer headers at LNG handling facilities when the selected grade, class, impact-test requirements, design temperature, and applicable piping code are verified by the project engineer.

For this application, Class 22 or Class 32 is commonly considered where post-weld heat treatment or normalization, radiographic weld examination, and pressure testing are required by the project specification.

The exact material selection must be based on the minimum design metal temperature and required Charpy impact performance rather than pipe strength alone.

Chemical Composition

The following values show representative ASTM plate chemistry requirements used to manufacture five common ASTM A671 carbon steel pipe grades.

Values are based on heat analysis. Carbon limits shown below apply to A515 plate up to 25 mm thick and A516 plate up to 12.5 mm thick. Carbon limits increase for certain greater plate thicknesses; therefore, the applicable plate thickness must always be checked against the corresponding ASTM A515/A515M or ASTM A516/A516M requirement.

Mechanical Properties

The ASTM A671 pipe grade derives its base-metal strength level from the corresponding pressure-vessel plate specification.