I. Standard Overview
ASTM A672 is an international standard from the American Society of Engineers (ASTM) applicable to electrofusion welded (EFW) steel pipes for high-pressure pipelines.
This standard covers pipelines carrying high-pressure fluids such as water, steam, oil, and natural gas. Pipe grades range from Grade A to Grade F, selectable based on pipeline pressure and strength requirements.
ASTM A672 EFW pipes are characterized by high weld strength, good pressure resistance, and uniform wall thickness, making them the ideal choice for large-diameter, high-pressure pipeline projects.
II. Grade Classification
ASTM A672 steel pipes are classified into grades based on steel strength and pressure resistance:
| Level | English Grade | Features / Applicable Pressure Range |
|---|---|---|
| 1 | Grade A | Low-pressure service, suitable for water and steam transport |
| 2 | Grade B | Medium–low pressure pipelines, suitable for general industrial fluids |
| 3 | Grade C | Medium-pressure pipelines, higher pressure-bearing capacity |
| 4 | Grade D | High-pressure pipelines, suitable for oil and gas transport |
| 5 | Grade E | High or ultra-high-pressure service |
| 6 | Grade F | Ultra-high-pressure pipelines or extreme conditions, highest weld requirements |
III. ASTM A672 High-Pressure Electrofusion Welded Steel Pipes: Material and Mechanical Properties
i. Material Chemical Composition
| Grade | C ≤ % | Mn ≤ % | P ≤ % | S ≤ % | Si ≤ % |
| A | 0.28 | 1.20 | 0.035 | 0.035 | 0.15 |
| B | 0.30 | 1.25 | 0.035 | 0.035 | 0.15 |
| C | 0.32 | 1.30 | 0.035 | 0.035 | 0.20 |
| D | 0.34 | 1.35 | 0.035 | 0.035 | 0.20 |
| E | 0.36 | 1.40 | 0.035 | 0.035 | 0.20 |
| F | 0.38 | 1.45 | 0.035 | 0.035 | 0.25 |
Note: Chemical composition affects the strength, weldability, and low-temperature toughness of the pipe. Higher grades have slightly higher carbon content, resulting in higher yield and tensile strength.
ii. Mechanical properties
| Grade | Yield Strength (MPa, Min) | Tensile Strength (MPa, Min) | Elongation (%) (Min) |
|---|---|---|---|
| A | 240 | 400 | 25 |
| B | 250 | 410 | 25 |
| C | 260 | 420 | 23 |
| D | 270 | 430 | 23 |
| E | 280 | 440 | 22 |
| F | 290 | 450 | 20 |
Explanation:
Yield strength determines whether the pipe will undergo permanent deformation under working pressure.
Tensile strength ensures the pipe will not break under extreme operating conditions.
Elongation ensures the pipe has a certain degree of ductility, improving its impact resistance.
IV. ASTM A672 Specification and Dimension Table for Electrofusion Welded (EFW) Steel Pipes for High Pressure Applications
| NPS(inch) | OD(mm) | WT(mm) | Theoretical weight kg/m |
| 2 | 60.3 | 3.0–7.1 | 4.0–9.5 |
| 3 | 88.9 | 3.2–8.6 | 6.5–13.0 |
| 4 | 114.3 | 3.5–9.5 | 9.5–18.0 |
| 6 | 168.3 | 4.0–12.7 | 15.5–30.0 |
| 8 | 219.1 | 4.5–15.9 | 22.5–42.5 |
| 10 | 273.0 | 5.0–19.1 | 31.0–58.0 |
| 12 | 323.9 | 5.5–22.2 | 40.0–76.0 |
| 14 | 355.6 | 6.0–25.4 | 50.0–95.0 |
| 16 | 406.4 | 6.5–28.6 | 62.0–115.0 |
| 18 | 457.2 | 7.0–31.8 | 76.0–140.0 |
| 20 | 508.0 | 7.5–34.9 | 90.0–165.0 |
| 24 | 609.6 | 8.0–41.3 | 120.0–220.0 |
| 30 | 762.0 | 9.0–50.8 | 180.0–320.0 |
V. Production Process
Hot-rolled steel plate/strip → Rolled into cylinders → Electrofusion welding (EFW) → Cooling and shaping → Dimensional verification → Surface treatment → Inspection and acceptance
VI. ASTM A672 Testing Standards for Electrofusion Welded (EFW) Steel Pipes for High Pressure Use
| Inspection Item | Method / Standard | Acceptance Criteria / Parameters |
|---|---|---|
| Chemical Composition | Spectral Analysis / Chemical Analysis | C ≤ 0.28–0.38% (Grade A–F), Mn ≤ 1.2–1.45%, P ≤ 0.035%, S ≤ 0.035%, Si ≤ 0.15–0.25% |
| Yield Strength | Tensile Test | Grade A: ≥ 240 MPa, Grade B: ≥ 250 MPa, Grade C: ≥ 260 MPa, Grade D: ≥ 270 MPa, Grade E: ≥ 280 MPa, Grade F: ≥ 290 MPa |
| Tensile Strength | Tensile Test | Grade A: 400–540 MPa, Grade B: 410–550 MPa, Grade C: 420–560 MPa, Grade D: 430–570 MPa, Grade E: 440–580 MPa, Grade F: 450–590 MPa |
| Elongation | Tensile Test | Grade A / B: ≥ 25%, Grade C / D: ≥ 23%, Grade E: ≥ 22%, Grade F: ≥ 20% |
| Weld Quality | Ultrasonic Testing (UT) / Magnetic Particle Testing (MT) | Continuous welds, no cracks, porosity, or lack of fusion defects |
| Dimensions & Tolerances | OD, Wall Thickness, Length Measurement | OD deviation ±1%, WT deviation ±12.5%, Length tolerance ±12 mm |
| Ovality & End Form | Measuring Tools / Instruments | Ovality ≤ 1%, End form (PE / BE) meets construction requirements |
| Appearance & Coating | Visual Inspection / Thickness Measurement | Smooth surface, no cracks, pits, or peeling; coating thickness ≥ 50 μm (Hot-Dip Galvanized) |
VII. Application Areas of ASTM A672 High-Voltage Electrofusion Welded Steel Pipes
| Application Area | Typical Service Condition | Description |
|---|---|---|
| High-Pressure Steam Pipelines | High-temperature, high-pressure steam transport | Used in power plants, industrial boilers, and thermal networks; requires steel pipes with high pressure, high temperature resistance, and long-term stability |
| High-Pressure Water Networks | Pump stations, urban water supply pipelines | Transports high-pressure water, suitable for long-distance or high-flow scenarios |
| Long-Distance Oil & Gas Pipelines | Crude oil and natural gas transport | High requirements for pipe pressure rating and weld strength; EFW pipes meet medium- to high-pressure transport needs |
| Industrial High-Pressure Fluid Pipelines | Chemical plants, process piping | Transports various liquids and gases, ensuring safe high-pressure operation |
| High-Pressure Station Pipelines | Pressure regulation stations, pump stations | Short-distance pressurized operation, ensures safe and reliable equipment connections |
VIII. Selection and Procurement Recommendations
| Selection Key Points | Recommendations / Parameter Notes |
|---|---|
| Grade Selection | Low to medium pressure → Grade A/B; High to ultra-high pressure → Grade D/E/F. Higher grade means higher pressure-bearing capacity |
| Pipe Type Selection | EFW: preferred for small to medium diameters, high-pressure, high weld strength; LSAW / SSAW: suitable for large diameters, long-distance pipelines |
| Wall Thickness Selection | Choose based on fluid pressure and pipeline length |
| Pipe Diameter Selection | Small diameter (≤6″) → EFW; Large diameter (>6″) → LSAW/SSAW |
| Anti-Corrosion Selection | Indoor → light corrosion protection; Outdoor or humid/high-temperature → FBE, epoxy, or hot-dip galvanizing |
| Procurement Notes | Verify material certificate (MTC), dimensions, weld quality; avoid overgrading or neglecting corrosion protection |
| Quick Selection Mnemonic | Determine grade by pressure → determine pipe type by length → select corrosion protection by environment → ensure all inspections pass |