Understanding Carbon Steel Pipe Grades — A53, A106, A671, A672

Introduction

Carbon steel pipes are the backbone of industrial piping systems worldwide. However, not all carbon steel pipes are the same — different ASTM standards cover different manufacturing methods, service conditions, and quality levels.

The four most important carbon steel pipe standards are ASTM A53, ASTM A106, ASTM A671, and ASTM A672. Understanding the differences between these grades is essential for proper material specification and safe piping system design.

ASTM A53 — The General Purpose Standard

ASTM A53 covers welded and seamless black and hot-dipped galvanized steel pipes for general applications.

Manufacturing Types:

•Type F: Furnace-butt welded, continuous welded

•Type E: Electric-Resistance Welded (ERW)

•Type S: Seamless

Grades:

•Grade A: Minimum tensile 330 MPa, yield 205 MPa

•Grade B: Minimum tensile 415 MPa, yield 240 MPa

Applications: General structural, water wells, air lines, steam lines (low pressure), fencing, scaffolding, general mechanical & pressure applications.

Key Feature: Available in both black and galvanized finish. Grade B is the most commonly specified.

ASTM A106 — The High-Temperature Standard

ASTM A106 covers seamless carbon steel pipe for high-temperature service.

Manufacturing: Seamless ONLY (no welded option)

Grades:

•Grade A: Tensile 330 MPa min, Yield 205 MPa min

•Grade B: Tensile 415 MPa min, Yield 240 MPa min (most common)

•Grade C: Tensile 485 MPa min, Yield 275 MPa min (highest strength)

Applications: High-temperature boiler tubes, process piping in refineries, steam lines, heat exchangers, superheater tubes, and any application where temperatures exceed ordinary levels.

Key Feature: Specifically designed and tested for elevated temperature service. Every pipe is hydrostatic tested. Most widely used specification for process piping in oil & gas and petrochemical industries.

ASTM A671 — EFW for Atmospheric Temperature

ASTM A671 covers electric fusion welded (EFW) steel pipes for atmospheric and lower temperature service.

Manufacturing: Electric Fusion Welded (double submerged arc welded / DSAW)

Classification System:

•First letter(s): Radiographic examination class (C = 100% radiography, E = spot radiography)

•Number: Plate specification (e.g., 60 = A516 Gr 60, 65 = A516 Gr 65)

•Examples: CC60, CC65, CC70, CE55, CE60

Applications: Power plants, refineries, low-temperature pressure piping, atmospheric service, and large-diameter pipeline applications.

Key Feature: Made from pressure vessel quality steel plates (A516 series) rolled and welded. Available in large diameters (16" to 72") that are not economically feasible as seamless.

ASTM A672 — EFW for High-Pressure Service

ASTM A672 covers electric fusion welded steel pipe for high-pressure service at moderate temperatures.

Manufacturing: Electric Fusion Welded (DSAW)

Classification System: Same as A671 (CC60, CC65, CC70, etc.)

Key Difference from A671: A672 has MORE STRINGENT requirements:

•Additional pressure testing requirements

•Stricter NDE (Non-Destructive Examination) requirements

•Higher design factors for pressure calculations

•Mandatory supplementary examination

Applications: High-pressure steam lines, high-pressure process piping, main steam piping in power plants, critical pressure service applications.

Key Feature: When A671 isn't enough — use A672 for higher-pressure and more critical applications using the same EFW manufacturing process.

Comparison Summary

Feature	A53	A106	A671	A672
Type	Seamless + Welded	Seamless Only	EFW	EFW
Temperature	Normal	High	Low/Atmospheric	Moderate
Pressure	Low/Medium	High	Medium	High
Sizes	1/8" - 26"	1/4" - 26"	16" - 72"	16" - 72"
Galvanized	Available	No	No	No
Primary Use	General	Process Piping	Power Plants	High-P Steam

Starlight Tubes manufactures pipes per all four standards. Contact us for detailed specifications, sizes, and pricing.

Frequently Asked Questions

Q.What is the difference between ASTM A53 and ASTM A106 pipe?

ASTM A53 covers both welded and seamless pipes for general applications and is available in galvanized finish. ASTM A106 covers seamless pipes only, specifically designed for high-temperature service in refineries and power plants. A106 has stricter chemistry and testing requirements for elevated temperature performance.

Q.What does CC65 mean in ASTM A671/A672?

In ASTM A671/A672, the 'C' prefix indicates 100% radiographic examination of weld seams, and '65' refers to the plate material (A516 Grade 65). So CC65 means an EFW pipe made from A516 Gr.65 plate with 100% radiographic inspection of all welds.