What is the difference between ASTM A671 and ASTM A672?
1. Fundamental Standard Definitions
ASTM A671:
Standard for Electric-Fusion-Welded Steel Pipe for Atmospheric and Lower Temperature Service (EFW pipe). Designed for cryogenic fluid transmission (-196°C to +50°C), such as LNG/liquid nitrogen. Mandatory post-weld heat treatment and -45°C Charpy impact toughness (e.g., ≥27J for CL22 grade). Complements A252 GR3 (structural piles with yield ≥310MPa) in application scope.
ASTM A672:
Standard for Electric-Fusion-Welded Steel Pipe for High-Pressure Service at Moderate Temperatures (EFW+HT pipe). Applicable to high-pressure systems (-29°C to +343°C), including steam/chemical pipelines. All pipes require heat treatment ("HT" suffix) for dimensional stability under pressure.
2. Key Technical Contrasts
A671 Prioritizes Low-Temperature Toughness:
Chemical control (C≤0.25%, P≤0.035%, S≤0.035%) and normalized microstructure ensure crack resistance at -196°C (LNG conditions). Uses 3LPE anti-corrosion coating (upgraded from the 3PE discussed for A252 GR3).
A672 Focuses on High-Temperature Strength:
Creep resistance design for steam pipelines (e.g., 540°C/8.5MPa). Relies on alloy linings (e.g., Inconel) instead of external coatings.
3. Divergent Applications
A671 Dominates Cryogenic Scenarios:
LNG terminals (e.g., Jiangsu Rudong LNG project) and liquid nitrogen tanks, where A252 GR3 piles would fail due to brittle fracture.
A672 Serves High-Pressure Systems:
Power plant steam lines (e.g., Three Gorges Dam) and chemical reactors, differing fundamentally from A252's structural pile use.
yield strength of ASTM A671
| Grades | Yield Strength (N/mm2) | Tensile Properties (N/mm2) | Elongation (%) | Welding point tensile strength (N/mm2) |
|---|---|---|---|---|
| -/A45 | -/165 | -/310~450 | -/30 | -/310~450 |
| -/A50 | -/185 | -/345~485 | -/28 | -/345~485 |
| CA55 / A55 | 205 | 380~515 | 27 | 380~515 |
| -/B55 | -/205 | -/380~515 | -/27 | -/380~515 |
| CB60 / B60 | 220 | 415~550 | 25 | 415~550 |
| CB65 / B65 | 240 | 450~585 | 23 | 450~585 |
| CB70 / C70 | 260 | 485~620 | 21 | 485~620 |
| -/C55 | -/205 | -/380~515 | -/27 | -/380~515 |
| CC60/ C60 | 220 | 415~550 | 25 | 415~550 |
| CC65 / C65 | 240 | 450~585 | 23 | 450~585 |
| CC70 / C70 | 260 | 485~620 | 21 | 485~620 |
A671 EFW Pipe Specification
| Type | ASTM A671 Gr. CC60/ CC65/ CC70 LSAW / SAW / EFW Pipe | |
| Executive Standard | API SPEC 5L,GB/T 9711.1,GB/T 9711.2,GB/T 9711.3,SY/T5037 | |
| ASTM A671 | Standard Specification for Electric-Fusion-Welded Steel Pipe for Atmospheric and Lower Temperatures | |
| ASTM A672 | Standard Specification for Electric-Fusion-Welded Steel Pipe for High-Pressure Service at Moderate Temperatures | |
| Class Designation | Class 10, 11, 12, 13, 20, 21, 22, 23, 30, 31, 32, 33, 34, 40, 41, 42, 43, 50, 51, 52, 53, 60, 61, 62, 63, 70, 71, 72, 73. | |
| Size | Outer Diameter | 12-64 inch |
| Wall Thickness | 2-60mm SCH10, SCH20, SCH30, STD, SCH40, SCH60, XS, SCH80, SCH100, SCH120, SCH140, SCH160, XXS |
|
| Length | Single random length/Double random length 5m-14m,5.8m,6m,10m-12m,12m or as customer's actual request | |
| Ends | Plain end/Beveled,protected by plastic caps on both ends, cut quare,grooved,threaded and coupling,etc | |
| Surface Treatment | Bare,Painting black,varnished,galvanized,anti-corrosion PE PP/EP/FBE coating |
|
Core Advantages of A671 welded pipe
Extreme Low-Temperature Toughness
By meeting the mandatory requirement of a Charpy impact energy ≥27J at -45℃ (CL22 grade), it addresses the risk of brittle fracture in media such as LNG (-162℃) and liquid nitrogen (-196℃).
Strictly Controlled Chemical Composition: Phosphorus and sulfur content (P≤0.035%, S≤0.035%) suppresses the tendency for low-temperature brittleness.
High-Pressure Sealing Reliability
100% Non-Destructive Testing of Welds (RT/UT Full Coverage) eliminates defects such as cracks and lack of fusion.
Hydrostatic Testing Reaches 2.5 Times the Design Pressure (e.g., design pressure 10MPa → test pressure 25MPa) to ensure absolute sealing under cryogenic conditions.
Process Assurance Mechanism
Electrofusion Welding (EFW) combined with forced post-weld heat treatment (normalizing/quenching + tempering) eliminates residual stress and improves dimensional stability under low-temperature conditions.
Applications of A671 Electric Fusion Welded (efw) Steel Pipe
LNG Industry Chain Core Pipelines
Receiving Terminal Transportation System (e.g., Rudong Project, Jiangsu):
→ Utilizes A671 CL22 steel pipe + 3LPE anti-corrosion layer for safe LNG transportation at -162℃.
Floating Storage and Regasification Unit (FSRU):
→ Ship-to-shore connection pipes rely on the high toughness of A671 steel to resist wave impact.
Cryogenic Medium Storage and Transportation
Liquid Nitrogen Storage Tank Piping Network (-196℃):
→ A671 CL13 normalized steel pipe to avoid cryogenic phase transformation failure.
Cryogenic Chemical Systems
Equipped with nickel-based alloy linings (e.g., Inconel) to resist strong corrosion from liquid oxygen/liquid hydrogen.
