Alloy 316L (UNS S31603)
Type 316 is a stainless-steel alloy characterized by its austenitic structure, consisting of chromium and nickel. It also incorporates molybdenum, which enhances its overall corrosion resistance and mechanical properties at high temperatures. While sharing similarities with type 304, type 316 exhibits greater strength at elevated temperatures and improved corrosion resistance, especially against sulphates, phosphates, salts, and reducing acids such as sulfuric, sulphurous, and phosphoric. Type 316L, on the other hand, is a variant with an even lower carbon content than type 316.
Data Tables
| Cr | Ni | Mo | Co | Nb (+Ta) | Ti | V | W | Cu | C | Mn | N | Si | P | S | Fe | Al | |
| Min | 16.50 | 10.00 | 2.00 | – | – | – | – | – | – | – | – | – | – | – | – | – | – |
| Max | 18.50 | 13.00 | 2.50 | – | – | – | – | – | – | 0.04 | 2.00 | 0.11 | 1.00 | 0.04 | 0.03 | Bal | – |
Mechanical Properties
| Bars up to and including 1 3/8” (35mm) diameter or section | Bars greater than 1 3/8” (35mm) diameter or section | |||
| 0.2% Proof Stress | 205 N/mm2 | 29.7ksi | 205 N/mm2 | 29.7ksi |
| Tensile Strength, min | 515 N/mm2 | 74.75ksi | 515 N/mm2 | 74.75ksi |
| Tensile strength, max | 700 N/mm2 | 101.5ksi | 700 N/mm2 | 101.5ksi |
| Elongation, 5.65√S0 and 4D | 35% | – | 20% | – |
| Reduction of Area | 40% | – | 40% | – |
| Hardness (Brinell) | <270 | – | <270 | – |
| Impact Strength (Room Temp) | Typically >88J | – | Typically >88J | – |
Physical Properties
| Density (Kg/m3) | 8000 |
| Magnetic Permeability (20°C) | <1.05 |
| Young’s Modulus (kN/mm2) | 193 |
| Specific Electrical Resistance, 20°C (µΩ-m) | 0.74 |
| Mean coefficient of thermal expansion, 20-100°C (m/m/°C) | 15.9 x 10-6 |
| Specific Heat, 20°C (J/kg.K) | 500 |
| Thermal conductivity, 20°C (W/m.K) | 16.3 |
Key Features
- Higher resistance to pitting corrosion and crevice corrosion in seawater than Alloy 304 stainless steel.
- Pitting Resistance Equivalent number (PREN) of 25 compared with 19 for Alloy 304.
- Excellent ductility and impact strength at both ambient and sub-zero temperatures
- Low carbon version of Alloy 316 thereby immune from grain boundary sensitisation.
- Excellent forming and welding characteristics.
- Non-magnetic except after significant welding or cold working
Applications
- Process industry equipment in chemical containers, transport units, heat exchangers and organic & fatty acid production.
- Marine and shipbuilding piping, pumps, valves, fittings and marine architecture.
- Oil & Gas industry piping, valves, pumps, heat exchangers.
- Mining industry for woven screens