SS 316 / 316L: properties, composition, uses and standards
SS 316 / 316L is a molybdenum-bearing austenitic stainless steel, chosen for chloride-bearing process fluids, marine air and pharmaceutical service. UNS S31603, W.Nr 1.4404, PREN ≈ 24, density 8 g/cm³.
What is SS 316 / 316L?
SS 316 / 316L is a molybdenum-bearing austenitic stainless steel. Engineers choose it for chloride-bearing process fluids, marine air and pharmaceutical service. It is also known as AISI 316L, UNS S31603, W.Nr 1.4404, Marine-grade stainless.
- UNS
- S31603 (316L) · S31600 (316)
- W.Nr
- 1.4404 · 1.4401
- EN
- X2CrNiMo17-12-2
- JIS
- SUS 316L
- BS
- 316S11
- Density
- 8 g/cm³
- Melting range
- 1375 – 1400 °C
- Magnetic
- Non-magnetic annealed
- PREN (approx.)
- ≈ 24
Chemical composition and what each element does
| Element | Weight % |
|---|---|
| Chromium | 16.0 – 18.0 |
| Nickel | 10.0 – 14.0 |
| Molybdenum | 2.00 – 3.00 |
| Carbon | 0.030 max |
| Manganese | 2.00 max |
| Silicon | 0.75 max |
| Nitrogen | 0.10 max |
| Phosphorus | 0.045 max |
| Sulphur | 0.030 max |
| Iron | Balance |
Per ASTM A240 for UNS S31603.
2–3% molybdenum is what lets 316L survive coastal air, brackish water and mild chlorides where 304 pits.
16–18% chromium forms the passive film.
Extra nickel balances the molybdenum and keeps the steel austenitic.
0.030% carbon max keeps welds free of sensitisation.
SS 316 / 316L at a glance
See the SS 316 / 316L product page for every form we supply and its standard.
Mechanical properties
| Property | Value |
|---|---|
| Tensile strength | 485 MPa · 70 ksi |
| Yield strength 0.2% | 170 MPa · 25 ksi |
| Elongation | 40% |
| Hardness | 217 HB max |
Annealed plate & sheet (316L), minimum values. Values for pipe, bar and forgings differ slightly — see the product standard.
Where SS 316 / 316L is used
- Chemical & process. Piping and vessels handling mild acids and chlorides. Industry →
- Pharmaceutical. Process vessels and hygienic piping. Industry →
- Marine & coastal. Deck fittings and structures exposed to salt air. Industry →
- Food processing. Brine, sauces and salted products. Industry →
- Oil & gas utilities. Instrument tubing and utility lines. Industry →
- Water treatment. Filtration and dosing systems. Industry →
Welding 316L
The matching filler is ER316L (AWS A5.9). ER309LMo for dissimilar joints.
Keep heat input moderate and interpass temperature low, clean joints thoroughly, and pickle or passivate after welding where the service is corrosive.
SS 316 / 316L compared with similar grades
| Grade | PREN | Choose it for |
|---|---|---|
| SS 316 / 316L | ≈ 24 | Chloride-bearing process fluids, marine air and pharmaceutical service |
| SS 304 | ≈ 18 | General corrosion resistance, food, water and architectural work |
| SS 904L | ≈ 35 | Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water |
| Duplex 2205 | ≈ 35 | Strength with chloride resistance at a stainless-steel budget |
SS 316 / 316L standards by product
Buying SS 316 / 316L: what to specify
- The product standard and the UNS or designation — for example ASTM A240 UNS S31603.
- Size, thickness or schedule, and quantity in pieces and kg or metres.
- Heat-treatment condition where the standard offers a choice.
- Certificate: EN 10204 3.1 as standard, 3.2 if a third party must witness.