316
1.4401 · EN 10088 / AISI · 1.4401
316 is a stainless steel (Austenitic family) to EN 10088 / AISI (1.4401). It has a specified 0.2 % proof stress of 220 MPa and a typical tensile strength of about 520 MPa, with a uniform elongation of 40 %. For nonlinear FEA, a bilinear model uses E = 193 GPa up to yield and a tangent modulus of 756 MPa above it. Its austenitic structure gives excellent corrosion resistance, formability and cryogenic toughness, but it cannot be hardened by heat treatment.
Bilinear material model — nonlinear FEA
Uniform elongation εu = 40.0% · conservative analysis limit ½εu = 20.0%
Bilinear (BISO) approximation. Elastic modulus E up to the 0.2% proof stress R_p0.2, then a single tangent slope Eₜ to the ultimate tensile strength: Eₜ = (Rₘ − R_p0.2) / (εu − R_p0.2/E − 0.002), where εu is the uniform elongation and Rₘ is a typical (nominal) UTS within the specified band. The half-εu figure is a conservative strain limit for the analysis. Treat these as guidance for first-pass models; for critical work use a measured true stress–strain curve for the actual product and condition.
Ratings — engineering judgement
Weldabilitygood
Readily weldable by all common processes. Use 316L filler (low carbon) to avoid HAZ sensitisation. No preheat; keep interpass below 150 °C. Back-purge for pipe welding.
Formabilitygood
Excellent cold formability — deep drawing, bending, spinning all possible. Work hardens significantly, so more force is needed and spring-back is greater.
Machinabilitypoor
Difficult. Work hardens rapidly — avoid rubbing or dwelling. Sharp carbide tooling, positive rake, rigid setup, flood coolant. Noticeably worse than 304 due to the Mo.
Corrosion resistanceexcellent
Excellent general resistance. The Mo gives far better pitting and crevice resistance than 304, especially in chlorides — the 'marine grade'. Not immune to hot-chloride stress-corrosion cracking.
Hardenabilitynone
Cannot be hardened by heat treatment — the austenitic structure is stable. Strengthening only by cold work.
Toughnessexcellent
Outstanding at all temperatures including cryogenic. No ductile-to-brittle transition. Suitable down to −196 °C.
Expert notes
316 is what most people mean by 'marine grade stainless'. The 2–2.5% Mo is what makes it far more resistant to pitting and crevice corrosion than 304, particularly in chlorides.
The most common mistake: specifying 316 when 304 would do fine, because someone heard '316 is better'. It's better for chloride resistance — but harder to machine, more expensive, and no better than 304 in many environments. Match the grade to the actual corrosion challenge.
The second mistake: assuming 316 is immune to corrosion. It isn't — in warm chloride solutions (pools, coastal, under deposits) it will pit. If you need more, look at duplex (2205) or super-austenitic (254SMO).
For welding, always use 316L filler to avoid sensitisation — in fact specify 316L for the base metal too; the slight strength reduction is irrelevant in practice.
For bolted joints in 316: beware galling. Stainless-on-stainless threads seize aggressively — use anti-seize or silver-plated fasteners. A5-80 is the standard property class for austenitic stainless.
Physical properties
| Density | 7990 | kg/m³ |
| Elastic modulus | 193 | GPa |
| Shear modulus | 77 | GPa |
| Poisson's ratio | 0.30 | |
| Thermal expansion | 15.9 | ×10⁻⁶/°C |
| Thermal conductivity | 15 | W/(m·K) |
| Specific heat | 500 | J/(kg·K) |
| Electrical resistivity | 740 | nΩ·m |
Chemical composition (wt %)
Available forms
Equivalent grades
| Standard | Grade | Note |
|---|---|---|
| EN 10088 | X5CrNiMo17-12-2 / 1.4401 | |
| AISI | 316 | |
| BS 970 Pt 4 | 316S31 | |
| DIN 17440 | X5CrNiMo17-12-2 | |
| AFNOR | Z6CND17-12 | |
| JIS | SUS316 | |
| GB | 0Cr17Ni12Mo2 | |
| IS 6911 | 04Cr17Ni12Mo2 | Direct Indian equivalent, closely matching Cr-Ni-Mo composition. |
Historical designations
| Standard | Grade | Note |
|---|---|---|
| BS 970:1970 Pt 4 | 316S31 | British designation — still on older UK drawings. |
| AISI | Type 316 | The name most engineers use colloquially regardless of the actual standard. |
| Werkstoff Nr. | 1.4401 | German material number, common on EU documentation. |
Common applications
- Chemical and pharmaceutical processing equipment
- Marine hardware, boat fittings, propeller shafts
- Food and beverage processing equipment
- Architectural trim and handrails (external)
- Heat exchangers
- Surgical instruments and implants (316L)
- Fasteners for corrosive environments
- Desalination equipment
History
316 descends from the pioneering austenitic stainless work at Krupp (Strauss & Maurer, patented 1912). Molybdenum was added in the 1920s–30s to resist chloride pitting.
- 1912Strauss & Maurer at Krupp patent austenitic stainless steel (Nirosta)
- 1913Harry Brearley melts the first martensitic stainless steel in Sheffield
- 1930Molybdenum-bearing austenitic grades (precursors to 316) developed for chemical industry
- 1940316 in widespread industrial use in US chemical and petroleum plants
- 1965Gateway Arch, St. Louis completed using 316 stainless cladding