ASTM A312

USED FOR:

Seamless, welded, and heavily cold-worked austenitic stainless steel pipe intended for high-temperature and general corrosive service.

A312 governs stainless steel pipe specifically; it is the stainless counterpart to A106/A53 for carbon steel, covering pipe supplied in both seamless and welded construction under the same specification.

RELATED STANDARDS:

• Sibling specs: ASTM A358 covers electric-fusion-welded austenitic stainless pipe for corrosive or high-temperature service, typically used for larger diameters where A312’s welded route becomes less economical or where specific NDE/joint efficiency documentation is needed. ASTM A409 covers welded large-diameter stainless pipe for low-to-moderate pressure applications, more common in low-pressure ducting or process lines than pressure piping. ASTM A790 covers seamless and welded ferritic/austenitic (duplex) stainless steel pipe. Duplex stainless steel pipe is specified under ASTM A790 rather than ASTM A312.
• Design code that invokes it: ASME B31.3 (process piping) is the primary code referencing A312 for stainless steel pressure piping; ASME Section VIII and B31.1 also reference it where stainless pipe is required in pressure vessel or power piping contexts.
• Dimensional standard that pairs with it: ASME B36.19M (stainless steel pipe) defines the OD and wall thickness/schedule series for A312 pipe, distinct from B36.10M which covers carbon/alloy steel, this distinction is important since stainless schedules (5S, 10S, 40S, 80S) differ from standard carbon steel schedules.

GRADE / TYPE RANGE:
A312 covers a wide range of austenitic stainless steel grades including TP304/304L, TP316/316L, TP321, TP347 and other austenitic grades. Duplex stainless steel grades are covered by ASTM A790.

The “L” (low carbon) grades cap carbon content lower than their standard counterparts specifically to reduce sensitization risk during welding, at a modest trade-off in high-temperature strength,  this is the most common grade-selection decision engineers make on this spec.

TP316/316L adds molybdenum relative to TP304/304L, improving resistance to chloride pitting and general corrosion, making it the default choice in marine, offshore, and chloride-bearing process environments.

TP321 and TP347 are stabilized grades (titanium and niobium respectively) intended for elevated-temperature service where carbide precipitation and sensitization during long-term high-temperature exposure is a concern, these are typically specified above roughly 425°C (800°F) service where L-grades alone aren’t sufficient long-term.

Tensile and yield strength differences across the grades are relatively modest compared to the differences in corrosion resistance and high-temperature stability, so grade selection here is driven primarily by service environment and temperature rather than mechanical strength.

DESCRIPTION:
A312 covers seamless, welded, and heavily cold-worked austenitic stainless steel pipe. Welded pipe may be manufactured with or without filler metal as permitted by the specification. Nondestructive examination requirements are those specified by ASTM A312 and any additional project or code requirements.

Testing requirements include tensile testing, flattening or flange testing as applicable, hardness testing where required, hydrostatic or nondestructive electric testing, and supplementary intergranular corrosion testing only when specified by the purchaser. IGC testing is a notable feature not found in the carbon steel pipe specs, reflecting the sensitization concerns unique to austenitic stainless.

Heat treatment (solution annealing) is mandatory to develop the correct microstructure and corrosion resistance, and this is verified as part of the qualification. Marking requirements identify manufacturer, grade, heat number, and NDE method, with heat number traceability commonly required through to the pipe spool level in higher-integrity projects.

TYPICAL INDUSTRY USE:
Extensively used in oil & gas process piping (especially where corrosion resistance or chloride exposure is a concern), offshore and marine piping systems, chemical/petrochemical plants, food and pharmaceutical processing, and high-temperature piping in power and refining applications.

IMPORTANT NOTES:

• We often see confusion between A312 and A358 on larger-diameter welded stainless pipe, if the project spec calls for specific weld joint efficiency documentation or a defined NDE class (e.g., Class 1 vs Class 3 per A358), that’s usually a signal the intended standard is A358, not A312, even though both cover EFW stainless pipe.

• When required by the purchase specification, supplementary intergranular corrosion testing may be specified in accordance with the applicable ASTM A262 practice referenced by ASTM A312. We always confirm with the client whether IGC testing is required as a supplement, since it’s not universally mandatory across all grades and is easy to miss on a PO if the base spec is ordered without call-outs.

• A312 stainless grades are not inherently NACE MR0175/ISO 15156 qualified for sour service without specific hardness and, in some cases, additional PREN/pitting resistance verification,  for sour, chloride-bearing service we routinely cross-check the selected grade (and its condition, annealed vs. cold-worked) against NACE Part 3 requirements, since cold-worked high-strength stainless pipe can fail NACE hardness limits even though the base grade is otherwise acceptable.

• A common procurement mistake: ordering “A312 TP316” without specifying “L” or standard carbon content can lead to mill’s discretion on carbon level, which matters for welded fabrication and post-weld heat treatment planning, we recommend always specifying the exact grade suffix (L or standard) explicitly on the PO.

• Wall thickness tolerances and schedule availability differ meaningfully from carbon steel pipe (5S/10S schedules are thinner than standard carbon steel schedules), this is a frequent point of confusion during take-off and material transposition from a carbon steel base design to a stainless alternate.