Stainless Steel 316 and 316L


Grade 316 is the standard molybdenum-bearing grade, second inoverall volume production to 304 amongst the austenitic stainless steels. The molybdenum gives 316 better overall corrosion resistant properties than Grade 304, particularly higher resistance to pitting and crevice corrosion in chloride environments.

Grade 316L, the low carbon version of 316 and has very high immunity from sensitization (grain boundary carbide precipitation). It is extensivly used in the oil and gas and chemical industries for its cost effective corrosion resistance and ease of fabrication. There is commonly no appreciable price difference between 316 and 316L stainless steel. The austenitic structure also gives these grades excellent toughness, even down to cryogenic temperatures. Compared to chromium-nickel austenitic stainless steels, 316L stainless steel offers higher creep, stress to rupture and tensile strength at elevated temperatures.

These alloys may be considered for a wide variety of applications where one or more properties are important.

chemical;physical mechanical properties stainless steel

Specifications:

UNS S31600 / S31603

Standards:

ASTM/ASME: UNS S31600 / S31603
EURONORM: X1 CrNiMo 17 12 2 / X3 CrNiMo 17 12 2
AFNOR: Z 6 CND 17-11 / Z 2 CND 17-12
DIN: 1.4401 / 1.4404

Corrosion Resistance:

Generally more resistant than 304 in range of atmospheric environments and many corrosive media due to the increased chromium
and molybdenum content.
Subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 122°F (50°C).
Considered resistant to potable water with up to about 1000mg/L chlorides at ambient temperatures, reducing to about 500mg/L at
140°F (60°C).
Usually regarded as the “marine grade stainless steel” – but is not resistant to warm sea water.


Heat Resistance:

Good oxidation resistance in intermittent service to 1600°F (870°C) and in continuous service to 1700°F (925°C)
Grade 316L is more resistant to carbide precipitation.

Welding Characteristics:

Excellent weldability by all standard fusion methods, both with and without filler metals.
Heavy welded sections in Grade 316 require post-weld annealing for maximum corrosion resistance, this is not required for grade 316L.


Heat Treatment:

Annealing temperature range is 1900 to 2100°F (1038 to 1149°C).
Cannot be hardened by heat treatment.
Special consideration is needed to compensate for a higher coefficient of thermal expansion to avoid warping and distortion.


Processing – Hot Forming:

Most producers recommend a maximum forging temperature between 2100°F and 2300°F
Do not forge below 1700°F (927°C) Best
Corrosion resistance is obtained if the forgings are given a final anneal.


Processing – Cold Forming:

316/316L types being extremely tough and ductile, can be readily cold worked such as roll form, swaging, cold heading, deep drawing,
bent, etc., without difficulty
Severely cold formed parts should be annealed to remove stresses.


Machineability:

Type 316/316L is somewhat more difficult to machine than Type 304 because of its toughness.
316/316L machines with chip characteristics that are tough and strong.
Chip breakers and curlers are advised.
As large a tool as possible and great amounts of cutting fluid should be used.
Heavy positive feeds at low speeds should be considered since 316/316L work hardens rapidly.