What Is ASTM A240 Type 316 Stainless Steel Plate?

What ASTM A240 Type 316 Means

ASTM A240 is the specification issued by ASTM International that covers chromium and chromium-nickel stainless steel plate, sheet and strip for pressure vessels and for general applications. It sets the chemical composition and the tensile requirements for each grade, together with the permissible tolerances and the condition in which the material is delivered.

Type 316 is one of the grades listed in that specification. It is an austenitic stainless steel identified as UNS S31600, containing molybdenum as well as chromium and nickel, and it is supplied in the annealed and descaled condition for plate products.

Part of the designation	Meaning
ASTM A240	Plate, sheet and strip specification for pressure vessels and general applications
Type 316	Austenitic grade with 16-18% Cr, 10-14% Ni and 2-3% Mo, UNS S31600

Chemical Composition of ASTM A240 Type 316

Heat analysis limits for Type 316 plate are given below. Product analysis tolerances are slightly wider for some elements, as permitted by the specification.

Element	Limit, %
Carbon (C)	0.08 max
Manganese (Mn)	2.00 max
Silicon (Si)	0.75 max
Phosphorus (P)	0.045 max
Sulfur (S)	0.030 max
Chromium (Cr)	16.0 - 18.0
Nickel (Ni)	10.0 - 14.0
Molybdenum (Mo)	2.00 - 3.00
Nitrogen (N)	0.10 max

Molybdenum is the addition that separates 316 from the simpler 18-8 grades: it raises resistance to pitting and crevice corrosion, giving the grade the pitting resistance equivalent number of roughly 24 to 26 that makes it suitable for chloride-bearing service. Its lower-carbon companion, Type 316L, caps carbon at 0.03% for welded construction.

Mechanical Properties of ASTM A240 Type 316

Property	Requirement
Tensile strength	515 MPa (75 ksi) min
Yield strength, 0.2% offset	205 MPa (30 ksi) min
Elongation in 2 in. (50 mm)	40% min
Hardness, Rockwell B	95 HRB max

These are minimum values for the annealed condition. Thickness, rolling direction and secondary forming all influence the measured result, so each lot is released against its own mill test certificate.

Type 316 Versus Type 304

Property	Type 304	Type 316
Molybdenum	None	2.00 - 3.00%
Chloride pitting resistance	Moderate	Clearly better
Relative cost	Lower	Higher, reflecting nickel and molybdenum content
Typical duty	General indoor and mild outdoor service	Seawater, chemical and pharmaceutical environments

Both grades have the same austenitic structure and similar forming behaviour. The decision usually comes down to the chloride level and the operating temperature, because 304 is adequate in benign conditions while 316 pays for itself wherever pitting or crevice attack is a realistic risk.

Supply Condition, Identification and Applications

ASTM A240 Type 316 plate is normally supplied hot rolled and annealed with a No. 1 finish, or cold rolled to finishes such as 2B, No. 4 or bright annealed where a smoother surface is required. Plates can be supplied sheared, plasma cut or waterjet cut to a drawing.

Grade confirmation relies on the mill test certificate, the heat number marked on the plate and, before fabrication, positive material identification by X-ray fluorescence or optical emission spectroscopy.

Typical applications include:

Chemical processing vessels, tanks and reactor internals

Marine and offshore structures exposed to salt spray

Food, dairy and pharmaceutical processing equipment

Medical devices and surgical instruments

Architectural cladding and fittings in coastal or polluted atmospheres

Frequently Asked Questions

Q: What is the difference between ASTM A240 Type 316 and Type 316L?
Type 316 allows up to 0.08% carbon while Type 316L is capped at 0.03% carbon. The low-carbon version resists sensitisation after welding, while Type 316 offers slightly higher minimum strength.

Q: Does ASTM A240 cover plate only?
No. The specification covers plate, sheet and strip. Plate thicknesses are the heavy end of the range, with commercial plate commonly supplied from about 3 mm upward to 100 mm and beyond.

Q: Is Type 316 suitable for marine service?
It performs well in atmospheric marine exposure and in many chloride-bearing process streams. For continuously wetted or warm seawater, a higher alloyed stainless steel is usually selected.

Q: Does welded Type 316 plate need heat treatment?
Post-weld heat treatment is not normally required, but welds should be clean and properly finished. Where a component is heavily cold worked or must retain maximum corrosion resistance, solution annealing is used to restore the structure.

Q: How is the grade verified before fabrication?
By matching the mill test certificate and heat number on the plate, then confirming the alloy with positive material identification equipment before the material is cut.

Q: What affects the price of Type 316 plate?
Nickel and molybdenum content dominate the alloy cost, and thickness, width, surface finish, cutting route and order quantity then determine the delivered price of the finished plate.