ASTM A672 Electric Fusion Welded (EFW) Pipe

Basic Overview

A standard specification for electric-fusion-welded steel pipe manufactured with filler metal added, fabricated from pressure vessel quality plates. ASTM A672 is specifically designed for high-pressure service at moderate temperatures, making it essential for power generation, petrochemical, and industrial process applications .

Name Explanation

Key Features of ASTM A672 EFW Pipe

Key Terminology: Grade vs. Class

Understanding the distinction between Grade and Class is critical for ASTM A672:

Grade Designations & Plate Sources

The "Grade" in ASTM A672 corresponds to specific pressure vessel plate specifications :

Note: Grade numbers indicate approximate minimum tensile strength in ksi (e.g., B60 = 60,000 psi minimum tensile strength) .

Class Designations – Complete Reference Table

The "Class" determines heat treatment, radiographic examination, and pressure testing requirements. The class numbering system follows a logical pattern where the first digit indicates heat treatment type, and the second digit indicates inspection level :

Note 1: Selection of materials should be made with attention to temperature of service. For guidance, consult Specification A20/A20M .
Note 2: The class numbering logic: First digit (10-50) = heat treatment type; Second digit (0,1,2,3) = inspection level (0=none, 1=RT only, 2=RT + hydrotest, 3=hydrotest only).

Chemical Composition (Typical for Common Grades)

Source:

Mechanical Properties (Base Metal)

Source:

Note: Welding point tensile strength must meet or exceed the minimum tensile strength of the base metal grade .

Manufacturing Process

ASTM A672 EFW pipes are manufactured using the following process :

Plate Preparation: Pressure vessel quality steel plates are selected based on the required grade (A515, A516, A285, A537, etc.).

Forming: Plates are formed into cylindrical shape using Three Roll Bending or similar technology.

Welding: Longitudinal seam is welded using Submerged Arc Welding (SAW) process with added filler metal – this distinguishes EFW from ERW (which uses no filler metal). Double-sided welding (DSAW) ensures seam integrity .

Mechanical Expanding: Pipe may be expanded to achieve precise dimensional tolerances.

Heat Treatment: Applied according to the specified Class (stress relieving, normalizing, quenching & tempering) .

NDT & Testing: Radiographic examination on full length of each weld , hydrostatic testing as required by Class.

Finishing: End preparation (plain, beveled), coating application as specified .

Comparison Table: ASTM A672 vs. ASTM A671

These companion standards share the same manufacturing approach but serve different temperature ranges:

Testing & Inspection Requirements

Depending on the Class selected, ASTM A672 pipes undergo :

Common Applications

ASTM A672 EFW pipes are widely used in :

Typical Size Availability

Class Selection Guidelines

Selecting the appropriate Class depends on service requirements :

Advantages of ASTM A672 EFW Pipe

Important Selection Notes

1. Grade Selection by Temperature

A-grades (A285): Lower strength, general service

B-grades (A515): Preferred for moderate temperature service – specifically designed for elevated temperature applications

C-grades (A516): Fine grain, improved toughness – good balance of properties

Higher number = higher strength (60, 65, 70 indicate approximate tensile strength in ksi)

2. Class Selection Logic

The class numbering system makes selection straightforward :

First digit = heat treatment: 10 (as-welded), 20 (stress relieved), 30 (normalized), 40 (normalized & tempered), 50 (quenched & tempered)

Second digit = inspection: 0 (none), 1 (RT only), 2 (RT + hydrotest), 3 (hydrotest only)

Most common selections for moderate temperature service:

Class 12: As-welded, fully inspected – for general service

Class 22: Stress relieved, fully inspected – standard for many moderate-temperature applications

Class 32: Normalized, fully inspected – when grain refinement is needed

Class 42: Normalized and tempered, fully inspected – for enhanced elevated-temperature properties

3. Temperature Limitations

ASTM A672 is specifically for moderate temperature service (typically 200-350°C / 400-660°F)

For atmospheric and lower temperature service (<0°C), specify ASTM A671 instead

For very high temperatures (>400°C), consider alloy steel specifications

4. Code Compliance

ASME Code: Often adopted as SA-672 for Boiler and Pressure Vessel Code applications

Consult applicable construction codes (ASME B31.1 Power Piping, B31.3 Process Piping) for acceptance and design factors

5. Quality Assurance

Mill Test Certificate: EN 10204 3.1 or 3.2 typically required for critical applications

Ensure all required testing (RT, hydrotest) per specified Class is documented

Request Mill's Inspection Report from the production batch for project design verification

Final Takeaway: ASTM A672 EFW Pipe is the standard specification for large-diameter, electric-fusion-welded steel pipe fabricated from pressure vessel quality plates for high-pressure service at moderate temperatures. It is distinguished by its Grade (indicating the plate material, e.g., B70 from A515 Gr.70 for elevated temperature service) and Class (indicating heat treatment and inspection level, e.g., Class 22 for stress-relieved with radiography and hydrotest). This pipe is essential for power generation, geothermal, petrochemical, and industrial process applications requiring large diameters, thick walls, and reliable elevated-temperature performance. The most common specification for moderate-temperature, high-pressure service is ASTM A672 B70 Class 22 .