Materials / Compare
Stainless 316 vs. Steel AISI 4340
Compare Stainless 316 vs. Steel AISI 4340 strength, stiffness, weight and thermal properties.
| Try it on a partA bracket to run stress or thermal on, free in your browser | Open in LessCAD | Open in LessCAD |
|---|---|---|
| Mechanical | ||
| Yield strength | 265MPasourcetypical (representative), annealed 1.0 mm sheet | 1,035MPasourcetypical, transverse |
| Ultimate tensile strength | 583MPasourcetypical (representative), annealed 1.0 mm sheet | 1,140MPasourcetypical, transverse |
| Elongation at break | 61%sourcetypical (representative), annealed, in 2 in. (51 mm) | 18%sourcetypical, transverse |
| Young's modulus (stiffness) | 200GPasourcetypical, in tension | 200GPasourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered) |
| Density | 8,027kg/m³sourcetypical | 7,840kg/m³sourcetypical |
| Strength to weight | 33kN·m/kg | 132kN·m/kg4x higher |
| Stiffness to weight | 24.9MN·m/kg | 25.5MN·m/kg2% higher |
| Poisson's ratio | 0.3sourcedesign value (structural stainless steels) | 0.32sourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered) |
| Shear modulus | 76.9GPa2% stiffer in shear | 75.7GPa |
| Bulk modulus | 167GPa | 185GPa |
| Speed of sound | 4,992m/s | 5,049m/s |
| Thermal | ||
| Thermal conductivity | 14.6W/m·Ksource20–100 °C | 37.5W/m·Ksourcetypical |
| Thermal expansion | 16.5µm/m·Ksourcemean, 20–100 °C | 11.3µm/m·Ksourcemean, -18 to 93 °C |
| 100 mm part over a 50 °C swing | 82.5µm growth | 56.5µm growth46% less |
| Specific heat | 450J/kg·Ksourceat 20 °C | 448J/kg·Ksourcetypical |
| Heats up and cools (diffusivity) | 4.04mm²/s | 10.7mm²/s2.64x faster |
| Thermal shock resistance | 821W/m | 11,678W/m14.2x more resistant |
| Melting point | 1,390–1,440°Csourcemelting range | not sourced |
| Max service temperature | 871–899°Csourceoxidation (scaling) limit in air | not sourced |
| Values for | ATI 316 (UNS S31600), annealed 1.0 mm sheet, ATI technical data sheet (2012); Poisson's ratio from the Nickel Institute/SCI structural stainless design manual | Carpenter (Latrobe) Lescalloy 4340 VAC-ARC datasheet; mechanical row for 1100 °F temper; physical properties grade-level |
Every value links to the document that states it. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Questions
Is Stainless 316 stronger than Steel AISI 4340?
Steel AISI 4340 is stronger: its yield strength is 1,035 MPa against 265 MPa for Stainless 316 (3.91x).
Which is lighter, Stainless 316 or Steel AISI 4340?
Steel AISI 4340 is lighter: 7,840 kg/m³ against 8,027 kg/m³ for Stainless 316.
Which is stiffer, Stainless 316 or Steel AISI 4340?
Stainless 316 is stiffer: Young's modulus 200 GPa against 200 GPa for Steel AISI 4340, so the same part in Stainless 316 deflects less under the same load.
Which is lighter for the same job, Stainless 316 or Steel AISI 4340?
For the same stiffness or strength: Steel AISI 4340 is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.
| Part that must be | Stainless 316 | Steel AISI 4340 |
|---|---|---|
| Stiff rod or tie (tension) | 2% heavier | lighter |
| Stiff beam (bending) | 2% heavier | lighter |
| Stiff panel or plate | 2% heavier | lighter |
| Strong rod or tie | 4x heavier | lighter |
| Strong beam | 2.54x heavier | lighter |
| Strong panel or plate | 2.02x heavier | lighter |
For the same stiffness or strength, mass scales with density over stiffness (or strength) raised to a power set by how the part is loaded: 1 for a rod in tension, 1/2 for a beam in bending, 1/3 for a panel (the standard material-selection indices).
Which conducts heat better, Stainless 316 or Steel AISI 4340?
Steel AISI 4340 conducts heat better: 37.5 W/m·K against 14.6 W/m·K for Stainless 316.
Which expands less with temperature?
Steel AISI 4340 expands less: 11.3 µm/m·K against 16.5 µm/m·K for Stainless 316.