What ASTM A312 Covers
ASTM A312 governs austenitic stainless steel pipe used where ordinary carbon steel would corrode or scale. The specification defines chemistry, mechanical properties, dimensions, tolerances, and the testing that qualifies each pipe for pressure service. It applies to three product routes: seamless pipe, welded pipe made from a single plate or coil with a longitudinal seam, and heavily cold-worked welded pipe.
The pipe sizes run from NPS 1/8 up through NPS 30, in wall schedules from the thin 5S and 10S through standard, extra-strong, and double-extra-strong walls. Material is normally supplied in the solution-annealed condition, which restores full corrosion resistance after forming and welding.
A312 pipe is the backbone of process piping in chemical and acid plants, petrochemical units, oil and gas facilities, and high-temperature headers. For the stock itself, see our stainless steel pipe range, part of the wider industrial pipe program.
Grades Covered by ASTM A312
The specification lists a family of austenitic grades. Selection follows the service: temperature, the corrodent, and the chloride load. The table below summarizes the common A312 grades Nandini Steel stocks and the metallurgy that separates them.
| A312 Grade | UNS | Family | Key metallurgy | Typical service |
|---|---|---|---|---|
| TP304 | S30400 | Austenitic SS | 18Cr-8Ni, PREN ~18 | General fabrication, non-chloride service |
| TP304L | S30403 | Austenitic SS | C ≤ 0.03%, resists sensitization | Welded assemblies, no post-weld anneal |
| TP316 | S31600 | Austenitic SS | 2–3% Mo, PREN ~24 | Chloride and acid exposure |
| TP316L | S31603 | Austenitic SS | Low carbon + Mo | Welded pharma, food, chemical lines |
| TP321 | S32100 | Austenitic SS | Titanium stabilized | Elevated-temperature, weld-decay resistance |
| TP347 | S34700 | Austenitic SS | Niobium stabilized | High-temperature headers, exhaust |
| TP310S | S31008 | Austenitic SS | 25Cr-20Ni, high-temp scaling resistance | Furnace and heat-treatment service |
| 904L | N08904 | Super-austenitic SS | ~25Ni, ~4.5Mo, ~1.5Cu, PREN ~34 | Sulfuric acid, high-chloride duty |
For full grade pages, see 304, 316, 316L, 321, 347, 310S and 904L super-austenitic. When chlorides are present, step up: review 304 vs 316 and 304L vs 316L before committing a grade.
Seamless vs Welded A312 Pipe
Both product forms meet the same chemistry and pressure requirements, so the choice is usually commercial and dimensional rather than metallurgical. Seamless pipe has no weld seam and is often preferred for small bore, high-pressure, or cyclic service. Welded pipe is economical in larger diameters and thinner walls, and when made to A312 it carries full nondestructive examination of the seam.
| Attribute | Seamless A312 | Welded A312 |
|---|---|---|
| Longitudinal seam | None | Single welded seam, 100% examined |
| Typical size advantage | Small to medium bore, heavy wall | Larger diameter, thinner wall |
| Weld-joint efficiency | Not applicable | Per ASME code, seam factor applies |
| Pressure requirements | Identical chemistry and mechanicals | Identical chemistry and mechanicals |
Corrosion and High-Temperature Behavior
Austenitic A312 pipe is chosen for two reasons: corrosion resistance and strength at temperature. The chromium builds a passive oxide film, and molybdenum in the 316 and 904L grades raises resistance to pitting corrosion in chloride environments. The orderable guide to that ranking is the pitting resistance equivalent number (PREN): 304 (~18) is below 316 (~24), which is well below 904L (~34).
All austenitic grades remain susceptible to chloride stress-corrosion cracking, so hot concentrated chlorides may call for 904L or a duplex alternative rather than 316. For sour-gas duty, specify material against NACE MR0175 / ISO 15156 on the purchase order.
Avoiding Sensitization in Welded Lines
When austenitic stainless is held between 425 and 815 degrees C, chromium carbides can precipitate at grain boundaries and strip the adjacent metal of corrosion protection. This sensitization drives intergranular attack and weld decay. Two routes prevent it: specify a low-carbon L grade (C ≤ 0.03%, as in TP304L or TP316L), or use a titanium or niobium stabilized grade (TP321, TP347). Our guide to preventing sensitization and the ASTM A262 intergranular test cover verification. For procedure detail, see how to weld 316 and how to weld 304.
Testing and Certification
A312 requires each length to pass a hydrostatic test, or a nondestructive electric test as permitted, before shipment. Welded pipe gets seam examination, and the mill verifies chemistry and mechanical properties against the grade. Every order from Nandini Steel ships with an EN 10204 3.1 or 3.2 mill test certificate giving heat number, chemistry, and mechanical results for full traceability. See MTC, NDT and PMI testing and the EN 10204 certificate standard for what each document records.
| Requirement | ASTM A312 provision |
|---|---|
| Pressure test | Hydrostatic test, or approved nondestructive electric test |
| Weld examination | Seam NDE on welded and heavily cold-worked pipe |
| Heat treatment | Solution annealed and quenched, verified |
| Chemistry and mechanicals | Per grade, reported on the mill test certificate |
| Documentation | EN 10204 3.1 / 3.2 MTC with every order |
Related Standards for a Complete System
A piping system rarely uses pipe alone. A312 pipe mates with buttweld fittings to ASTM A403, dimensioned to ASME B16.9, and with flanges and forged components to ASTM A182 and ASME B16.5. Where the service turns to elevated-temperature chrome-moly duty instead of stainless, the companion seamless pipe spec is ASTM A335. Flat-product chemistry and finishes for the same grades are governed by ASTM A480.
Applications
A312 stainless pipe serves chemical processing, petrochemical, and oil and gas plants, along with high-temperature and pressure vessel and boiler circuits. For help matching a grade to a corrodent, use the stainless grade selection guide.
FAQ
What grades does ASTM A312 cover?
What is the difference between seamless and welded A312 pipe?
Does ASTM A312 require a hydrostatic test?
Which A312 grade resists chloride pitting best?
How do I prevent weld decay in A312 pipe?
Request a Quote
Nandini Steel holds ASTM A312 stainless pipe ex-stock for immediate dispatch, with an EN 10204 3.1/3.2 mill test certificate on every order. Send your grade, size, schedule, and quantity to reachus@nandinisteel.com or WhatsApp +91 99202 09184 for live pricing.