What A671 and A672 Are — and Why LSAW Mills Care
ASTM A671 and A672 cover electric-fusion-welded (EFW) pipe made from pressure-vessel-quality plate, with filler metal added (submerged-arc welding in practice — the LSAW process). The two specifications differ only in design temperature: A671 for atmospheric-temperature service (roughly −20 °F to +90 °F ambient duty) and A672 for high-pressure service at moderate temperatures (down to −20 °F and up to 650 °F, per the plate data). Nominally 16 in OD and larger, wall up to 3 in (75 mm) — the natural ASTM home for large LSAW pipe beyond ERW’s reach.
The Two-Part Designation: Grade + Class
A672/A671 designations look cryptic but are perfectly systematic: the grade letter+number names the plate steel (number ≈ minimum tensile in ksi), the class encodes heat treatment and inspection. Example: A672 Gr B60 Cl22 = A515 Gr 60 plate, stress-relieved, radiographed full weld length, hydro tested — the single most common LSAW supply condition.
| Grade | Plate Spec | Steel Type |
|---|---|---|
| A45 / A50 / A55 | ASTM A285 | Plain carbon, low/intermediate tensile |
| B55 / B60 / B65 / B70 | ASTM A515 | Killed carbon, moderate-temperature |
| C55 / C60 / C65 / C70 | ASTM A516 | Killed, fine-grain, improved toughness |
| D70 / D80 | ASTM A537 Cl.1 / Cl.2 | Mn-Si, normalized or Q&T |
| E55 / E60 | ASTM A442 | Carbon, impact-tested |
| H75 / H80 | ASTM A302 | Mn-Mo, normalized |
| J80 / J90 / J100 | ASTM A533 Cl.1/2/3 | Mn-Mo, Q&T |
| L65 / L70 / L75 | ASTM A204 | Mo alloy |
The Class Matrix: First Digit = Heat Treatment, Second = Inspection
| Class | Heat Treatment on Pipe | Radiography (Section 9) | Pressure Test (8.3) |
|---|---|---|---|
| 10 / 11 / 12 / 13 | None (as-welded) | — / RT / RT / — | — / — / Hydro / Hydro |
| 20 / 21 / 22 / 23 | Stress relieved | — / RT / RT / — | — / — / Hydro / Hydro |
| 30 / 31 / 32 / 33 | Normalized | — / RT / RT / — | — / — / Hydro / Hydro |
| 40 / 41 / 42 / 43 | Normalized & tempered | — / RT / RT / — | — / — / Hydro / Hydro |
| 50 / 51 / 52 / 53 | Quenched & tempered | — / RT / RT / — | — / — / Hydro / Hydro |
Choosing the class is choosing your cost and your weld confidence: higher first digit buys heat treatment (better toughness, lower residual stress, higher joint factor), the second digit buys inspection intensity. Most projects land on CL22 (stress-relieved + RT + hydro) or CL32 (normalized).
Test and Certification Requirements That Surprise First-Time Buyers
- Weld-metal chemistry is analyzed from the deposited weld every 500 ft of weld — not just the plate heat.
- One tension test per lot plus a transverse guided-weld bend test (two specimens) per lot — the weld itself must bend.
- Full-length radiography of the weld where the class requires it (second digit 1 or 2).
- Heat treatment performed on the finished pipe (furnace stress relief or normalizing), with records on the certificate.
- Plate certificates (A515/A516/A537…) trace alongside the pipe certificate — two document layers, both EN 10204 3.1-able.
Writing the PO: “A672 Gr C60 Cl22, EFW (LSAW with filler), OD ≥ 16 in, wall per class, full-length RT, stress relieved, hydro per 8.3, certificates EN 10204 3.1 for pipe and plate.” Grade letter (A–N) and class number answer the two questions every inspector asks: what plate, and what was done to it?
A671 or A672 — Which One?
If the line carries pressurized process fluid at elevated temperature, or the design code routes through ASME B31.3 Chapter II temperature tables, A672 is the specification. If the pipe is large-diameter structural/ambient duty — piling caissons, outfall, penstock ambient sections — A671 does the same metallurgy at a lower documentation tier. Both share the plate-family and class logic above, so a mill qualified for A672 B60 Cl22 typically quotes A671 equivalents immediately.
Frequently Asked Questions
Why can’t I just order A516 plate quality as ERW pipe?
ERW (no filler) is a different ASTM family. Once filler metal and PVQ plate enter — as all large LSAW does — A671/A672 are the correct specifications, with their class system defining what was done to the weld.
What is the joint factor of a class 22 weld?
Stress-relieved classes carry a weld joint factor of 0.90 (as-welded 0.85; normalized and better classes 1.00). The design code applies this factor to wall calculation — one more reason the class belongs in the inquiry.
Is the plate heat traceable to my pipe?
Yes — plate heat numbers run through the MTC package, and weld-deposit chemistry is re-analyzed during production. Ask for plate + pipe certificates linked by pipe number.
Which grade for low-temperature toughness?
The C family (A516 fine-grain killed) improves on B (A515); below A516’s comfortable range, move to A537 D-family or discuss alloy plates. Charpy requirements come from the plate spec and project spec combined.
CREATEEL supplies A671/A672 EFW (LSAW) pipe from C55 to C70 and beyond, classes per design, with plate + pipe dual traceability and third-party inspection.
Standards & references: ASTM A671/A672 · ASTM A515/A516
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