What Is A182 F316? Stainless Steel Flange

ASTM A182 F316 is an austenitic stainless steel forging specification for pipe flanges, fittings, and valve components. The “F316” designation indicates Grade 316 stainless steel (UNS S31600), which contains 2-3% molybdenum for enhanced corrosion resistance compared to Grade 304. F316 is the standard stainless steel flange material for chemical, pharmaceutical, and offshore piping systems.

Key Properties

Property	A182 F316	A182 F316L
UNS number	S31600	S31603
Chromium	16.0-18.0%	16.0-18.0%
Nickel	10.0-14.0%	10.0-14.0%
Molybdenum	2.0-3.0%	2.0-3.0%
Carbon (max.)	0.08%	0.030%
Yield strength (min.)	205 MPa (30 ksi)	170 MPa (25 ksi)
Tensile strength (min.)	515 MPa (75 ksi)	485 MPa (70 ksi)
ASME B16.5 group	1.7	1.10
Temperature range	-196degC to 538degC (-320degF to 1000degF)
Magnetic	Non-magnetic (austenitic)

F316 vs F316L

The “L” in F316L stands for low carbon. Reducing carbon from 0.08% to 0.030% max prevents chromium carbide precipitation (sensitization) during welding. Sensitization depletes chromium at grain boundaries, creating zones vulnerable to intergranular corrosion.

Feature	F316	F316L
Carbon	0.08% max	0.030% max
Weldability	Good (but risk of sensitization)	Excellent (no sensitization)
Strength	Higher	Lower (~15% less yield)
Post-weld heat treatment	Sometimes required	Rarely needed
Most common use	Non-welded or PWHT’d components	Welded piping (default choice)

Pro Tip

Most projects specify F316L (low carbon) as the default for all welded stainless steel piping. Dual-graded F316/F316L forgings—meeting both the F316 strength requirements and the F316L low-carbon limit—are widely available and eliminate the need to stock both grades.

When to Use A182 F316/F316L Flanges

F316/F316L flanges are specified for:

• Chemical plants: Acids, chlorides (superior to 304 in chloride environments due to Mo content)
• Offshore platforms: Seawater-exposed piping, process systems
• Pharmaceutical and food: Hygienic piping requiring corrosion resistance
• Cryogenic service: LNG piping (excellent toughness down to -196degC)
• High-temperature service: Up to 538degC continuous, though alloy steels may be more economical above 400degC

Common Mistake

Assuming F316 is immune to all corrosion. Grade 316 is susceptible to chloride stress corrosion cracking (SCC) at temperatures above ~60degC in chloride-bearing environments. For severe chloride service, duplex stainless steels (A182 F51) or nickel alloys (A182 F44, Alloy 625) are required.

Pressure Ratings

A182 F316L flanges have slightly lower pressure-temperature ratings than A105 carbon steel flanges due to lower yield strength:

Class	A105 (Grp 1.1) @ 100degF	A182 F316 (Grp 1.7) @ 100degF	A182 F316L (Grp 1.10) @ 100degF
150	285 psig	275 psig	230 psig
300	740 psig	720 psig	600 psig
600	1480 psig	1440 psig	1200 psig

The 17% pressure reduction for F316L (vs. A105) at Class 150 means you may need a higher class flange in stainless steel to achieve the same pressure capacity. Always verify the P/T rating for your specific material group.

Read the full guide to flanges