A/SA312 Pipe Specifications

ASTM A312 / ASME SA312 is a standard specification for seamless, straight-seam welded, and heavily cold-worked welded austenitic stainless steel pipe. It is one of the most widely used stainless steel pipe specifications across industrial, chemical, and process industries.

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    • Grades TP304/L & TP316/L
    • Seamless & EFW
    • NPS ¼” to 24” OD
    • Schedules 10 through 80S

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Manufacturing Forms

  • Seamless (SMLS) — Extruded without a weld seam; highest integrity, used in critical service
  • Welded (EFW) — Straight seam welded; more economical, suitable for most general service
  • Heavily Cold-Worked Welded — Welded then cold-worked to enhance mechanical properties

Key Characteristics

All grades under A312 are austenitic, meaning they have a face-centered cubic crystal structure achieved through high chromium and nickel content. This delivers:

  • Excellent corrosion resistance across a wide range of environments
  • Non-magnetic in the annealed condition
  • No hardening by heat treatment — only by cold working
  • Good toughness at cryogenic temperatures — does not become brittle at low temps unlike carbon or alloy steels
  • Good oxidation resistance at elevated temperatures

Common Grades

The grade system follows the 300-series stainless steel designations:

Grade Common Name Key Alloying Notable Properties
TP304 18-8 SS 18% Cr, 8% Ni General purpose workhorse; most widely used
TP304L Low Carbon 304 18% Cr, 8% Ni, low C Better weld corrosion resistance; avoids sensitization
TP316 Moly SS 16% Cr, 10% Ni, 2% Mo Superior chloride and pitting resistance
TP316L Low Carbon 316 16% Cr, 10% Ni, 2% Mo, low C Best combination of corrosion resistance and weldability
TP317/317L High Moly Higher Mo content Aggressive acid and chloride environments
TP321 Titanium Stabilized Ti addition Stabilized against sensitization; high-temp service
TP347 Niobium Stabilized Nb addition Stabilized grade; preferred in high-temp applications
TP309/310 High Heat Higher Cr & Ni Extreme high-temperature oxidation resistance

304/304L and 316/316L account for the vast majority of A312 usage in practice.

Primary Applications & Industries

  • Chemical & Petrochemical Processing The dominant use. Process piping handling acids, caustics, solvents, and corrosive process streams where carbon steel would rapidly corrode. 316/316L is favored where chlorides or sulfuric/phosphoric acids are present.
  • Pharmaceutical & Biotechnology High-purity piping systems for process water, purified water (PW), water for injection (WFI), and product transfer lines. Requires smooth internal finish (often electropolished) to prevent bacterial harborage and ensure cleanability.
  • Food & Beverage Processing Piping for dairy, brewing, beverage, and food production where hygiene, cleanability, and corrosion resistance are mandatory. 304 and 316L are the standard materials.
  • Power Generation Condensate, feedwater, and auxiliary piping in nuclear and conventional power plants. SA312 designation is used in ASME-code nuclear and fossil fuel plant construction.
  • Pulp & Paper Industry Handling of bleaching chemicals (chlorine dioxide, caustic), black liquor, and other aggressive process streams that would destroy carbon steel rapidly.
  • Cryogenic Service Storage and transfer of liquefied gases — LNG, liquid nitrogen, liquid oxygen, liquid argon. Austenitic stainless retains excellent toughness and ductility down to cryogenic temperatures (-425°F / -254°C), unlike carbon steels which become brittle.
  • Oil & Gas / Offshore Topside process piping on offshore platforms, particularly in seawater-exposed environments. 316L is preferred due to its superior resistance to chloride pitting from seawater.
  • Semiconductor & Electronics Manufacturing Ultra-high-purity gas and chemical distribution systems. Requires electropolished internal surfaces and stringent cleanliness standards.
  • Water Treatment Seawater desalination, high-purity water systems, and wastewater treatment where corrosion resistance is needed.
  • Architecture & Construction Exposed structural and decorative piping in buildings, bridges, and facades where aesthetics and corrosion resistance are both required.

Tensile Requirements

GRADE
304		 GRADE
304L		 GRADE
316		 GRADE
316L
Tensile Strength, minimum PSI 75,000 70,000 75,000 70,000
Yield Strength, minimum PSI 30,000 25,000 30,000 25,000

Chemical Requirements

Grade UNS # Content % by weight
Carbon Manganese Phosphorus Sulfur Silicon Chromium Nickel Molybdenum
TP304 S30400 0.08 2.00 0.045 0.030 1.00 18 – 20 8 – 11 x
TP304L S30403 0.035 2.00 0.045 0.030 1.00 18 – 20 8 – 13 x
TP316 S31600 0.08 2.00 0.045 0.030 1.00 16 – 18 10 – 14 2 – 3
TP316L S31603 0.035 2.00 0.045 0.030 1.00 16 – 18 10 – 14 2 – 3

Permitted Variations in Wall Thickness

Tolerance, % from Nominal
NPS Designator Over Under
⅛ to 2½ incl., all t/D ratios 20.0 12.5
3 to 18 incl., t/D up to 5% incl. 22.5 12.5
3 to 18 incl., t/D > 5% incl. 15.0 12.5
20 and larger, welded, all t/D ratios 17.5 12.5
20 and larger, seamless, t/D up to 5% incl. 22.5 12.5
20 and larger, seamless, t/D > 5% 15.0 12.5

where:

t = Nominal Wall Thickness

D = Ordered Outside Diameter
  • Exception for welded pipe: the weld area shall not be limited by the “Over” tolerance

 

Heat Treatment

All pipe shall be furnished in the heat-treated condition

Heat treat temperature for 304/L and 316/L is 1900 deg F (1040 deg C) minimum and then quenched in water or rapidly cooled.

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* This information is provided for quick references. Always consult applicable ASME, ASTM and Manufacture’s standards.