Type 316 Annealed Stainless Steel Plate: Properties and Uses

What Is Type 316 Annealed Stainless Steel Plate?

Type 316 is an austenitic stainless steel designated UNS S31600 (EN 1.4401, JIS SUS316, GB 06Cr17Ni12Mo2) whose defining feature is the addition of 2.0-3.0% molybdenum to the 18-8 chromium-nickel base. In flat-product form it is supplied as plate under ASTM A240/A240M, with a thickness range that starts at 4.76 mm (3/16 in) and extends beyond 100 mm for pressure-vessel and structural service; material below 4.76 mm is classified as sheet or strip. The word "annealed" describes the standard mill delivery condition: the plate is solution-treated at 1010-1120°C, held long enough to dissolve chromium carbides, then rapidly cooled, normally by water quenching. The result is a soft, ductile, uniformly austenitic microstructure that is easy to machine, bend, stamp and weld, with hardness around 79 HRB and elongation at break of roughly 50%.

Chemical Composition and Mechanical Properties

Typical composition ranges for 316 plate (ASTM A240, weight %):

Element	C	Mn	P	S	Si	Cr	Ni	Mo
316 (S31600)	≤0.08	≤2.00	≤0.045	≤0.030	≤0.75	16.0-18.0	10.0-14.0	2.00-3.00
316L (S31603)	≤0.03	≤2.00	≤0.045	≤0.030	≤0.75	16.0-18.0	10.0-14.0	2.00-3.00

Minimum mechanical properties of annealed plate per ASTM A240:

Property	316 (S31600)	316L (S31603)
Tensile strength, Rm	515 MPa (75 ksi)	485 MPa (70 ksi)
Yield strength, Rp0.2	205 MPa (30 ksi)	170 MPa (25 ksi)
Elongation in 50 mm	40%	40%
Hardness	HRB ≤95	HRB ≤95

Why the Annealed Condition Matters

Annealing is not optional cosmetic treatment; it defines the plate's serviceability. A correctly annealed 316 plate has all chromium held in solid solution, which is what restores and maintains the protective chromium oxide film after hot rolling. Annealed plate delivers:

Low hardness (about 170-200 HV in the bright-annealed form) for trouble-free stamping, deep drawing, bending and sawing without cracking.

Consistent ductility and toughness across the plate, including at sub-zero temperatures down to -200°C for cryogenic service.

Freedom from residual rolling stress, so laser-cut and machined blanks stay dimensionally stable.

A uniform 2B matte or optional BA bright surface free of scale and rolling defects, easy to passivate and clean to food or pharmaceutical hygiene requirements.

Applications

Because of the molybdenum addition, 316 annealed plate is the default choice where chlorides, seawater, or process acids are present:

Marine and coastal structures: boat fittings, dock equipment, offshore platform components and coastal architectural cladding exposed to salt spray.

Chemical and petrochemical processing: storage tanks, reaction vessels, heat exchangers and piping systems handling acids, alkalis and salt solutions.

Food, beverage and pharmaceutical production: processing tanks, brewing equipment and clean-room panels that must tolerate caustic and chlorine-based sanitizers.

Heat transfer and power: boiler components, condensers and high-temperature process equipment operating continuously up to about 800°C in air.

316 or 316L: Which Plate Should You Specify?

Both grades share the same chromium, nickel and molybdenum ranges. The difference is carbon: 316L is limited to 0.03% maximum, which prevents chromium carbide precipitation (sensitization) at the grain boundaries during welding of thick sections. Practical guidance:

Specify 316L when the plate will be welded in sections above roughly 6 mm, or when post-weld annealing is not practical.

Specify 316 when higher elevated-temperature strength is needed, provided welded joints are solution-annealed afterwards.

For laser or plasma-cut blanks used below 400°C without welding, the two grades are often interchangeable in practice, but 316L remains the safer default.

Common Misconceptions

"Annealed 316 is soft and weak." Annealing optimizes ductility and toughness while tensile strength stays above 515 MPa; it is not a reduction in quality.

"316 is completely non-magnetic." The annealed condition is essentially non-magnetic, but cold work from bending or cutting can induce slight magnetism.

"316 is immune to seawater." It resists pitting far better than 304, but stagnant, oxygen-depleted seawater can still cause crevice corrosion; 6% Mo super-austenitics or duplex grades are specified for permanent immersion.

"All 316 plates are the same." Mill certificate, heat number, thickness tolerance and surface finish differ by supplier; buyers should verify the certificate against ASTM A240.

"Brighter surface means better quality." 2B and BA are finishing options, not corrosion ratings; pickling and passivation matter more than gloss.

FAQ

Is annealed 316 plate magnetic?

In the fully annealed condition it is essentially non-magnetic or only weakly magnetic. Cold working, such as heavy bending or edge rolling, can transform some austenite to martensite and produce measurable magnetism.

What is the difference between 316 and 316L plate?

Only the maximum carbon content differs: 0.08% for 316 versus 0.03% for 316L. The lower carbon of 316L avoids sensitization during welding, preserving corrosion resistance in the heat-affected zone without post-weld annealing.

What thickness range is considered plate?

Under ASTM A240/A480, plate normally starts at 4.76 mm (3/16 in) and goes up in thickness; coil and strip below this are classified as sheet or strip and follow their own dimensional tolerances.

Which surface finishes are available on 316 plate?

Common finishes are No.1 (hot rolled, annealed and pickled, for pressure vessels), 2B (cold rolled, bright matte), 2D (dull matte), BA (bright annealed) and No.4 (ground brushed) for architectural and food-contact surfaces.

Can 316 plate be used at high temperature?

Yes, it resists scaling in air up to about 870°C continuous service and retains useful strength to 800°C, which is why it appears in heat exchangers and boiler internals. Above 425°C, carbide precipitation is possible and 316H or stabilized grades should be evaluated.

How should 316 plate be purchased to avoid rejects?

Request the mill certificate (EN 10204 3.1), confirm the standard edition (ASTM A240 latest revision), specify thickness tolerance, surface finish and edge condition, and state the intended service environment so the supplier can confirm whether 316, 316L or a duplex grade is appropriate.