What Is ASTM A312? Stainless Steel Pipe

ASTM A312 is the standard specification for seamless, welded, and heavily cold-worked austenitic stainless steel pipe. It covers the workhorse grades used in chemical plants, food processing, pharmaceutical, and oil and gas applications: TP304, TP304L, TP316, TP316L, TP321, and TP347, among others.

Austenitic stainless steels offer excellent corrosion resistance, good high-temperature properties, and cryogenic toughness, all without the need for post-weld heat treatment in most cases.

Common ASTM A312 Grades

Grade	Cr (%)	Ni (%)	Mo (%)	C (max %)	Key Feature
TP304	18-20	8-11	-	0.08	Standard austenitic grade
TP304L	18-20	8-12	-	0.035	Low carbon (weld corrosion resistance)
TP316	16-18	10-14	2-3	0.08	Mo addition for pitting resistance
TP316L	16-18	10-14	2-3	0.035	Low carbon + Mo
TP321	17-19	9-12	-	0.08	Ti-stabilized (sensitization resistance)
TP347	17-19	9-13	-	0.08	Nb-stabilized (sensitization resistance)
TP310S	24-26	19-22	-	0.08	High-temp oxidation resistance

Mechanical Properties

Grade	Yield Strength (min)	Tensile Strength (min)	Elongation (min)
TP304/304L	170/170 MPa	485/485 MPa	35%
TP316/316L	170/170 MPa	485/485 MPa	35%
TP321	205 MPa	515 MPa	35%
TP347	205 MPa	515 MPa	35%
TP310S	205 MPa	515 MPa	35%

Manufacturing Options

ASTM A312 covers three manufacturing methods:

• Seamless: Produced from a solid round or hollow billet by hot working and cold finishing
• Straight-seam welded: Formed from plate/strip, welded by TIG, plasma, or laser, with or without filler metal
• Heavily cold-worked: Cold-reduced to achieve final dimensions (enhanced surface finish and tolerances)

Welded pipe under ASTM A312 must have the weld area solution-annealed (at 1040°C minimum for 304/316) and all pipes must pass a hydrostatic test or eddy current test.

Applications

• Chemical and petrochemical process piping
• Food and beverage processing lines
• Pharmaceutical manufacturing piping
• Cryogenic piping (LNG, nitrogen, oxygen)
• Desalination plants
• Heat exchanger shell-side piping

Pro Tip

Always specify the “L” grade (304L or 316L) when the pipe will be welded and exposed to corrosive media. The low-carbon content (0.035% max) prevents chromium carbide precipitation at grain boundaries (sensitization), which causes intergranular corrosion in the heat-affected zone. Dual-certified 304/304L and 316/316L pipe meets both specifications.

ASTM A312 vs A358 vs A778

Specification	Method	Use
A312	Seamless and welded (auto-welded)	Standard process piping
A358	EFW (electric fusion welded from plate)	Large-diameter, high-pressure
A778	Welded, unannealed	Low-pressure, non-critical

For choosing between 304 and 316, see 304 vs 316 stainless steel pipe.

Read the full guide to pipe types