Materials / Compare
Stainless 304 vs. Steel AISI 4340
Compare Stainless 304 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 | 241MPasourcetypical, annealed, 70 °F (21 °C) | 1,035MPasourcetypical, transverse |
| Ultimate tensile strength | 586MPasourcetypical, annealed, 70 °F (21 °C) | 1,140MPasourcetypical, transverse |
| Elongation at break | 55%sourcetypical, annealed, in 2 in. (50.8 mm) | 18%sourcetypical, transverse |
| Young's modulus (stiffness) | 193GPasourcetypical, in tension | 200GPasourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered) |
| Density | 8,030kg/m³sourcetypical | 7,840kg/m³sourcetypical |
| Strength to weight | 30kN·m/kg | 132kN·m/kg4.4x higher |
| Stiffness to weight | 24MN·m/kg | 25.5MN·m/kg6% higher |
| Poisson's ratio | 0.3sourcedesign value (structural stainless steels) | 0.32sourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered) |
| Shear modulus | 74.2GPa | 75.7GPa2% stiffer in shear |
| Bulk modulus | 161GPa | 185GPa |
| Speed of sound | 4,903m/s | 5,049m/s |
| Thermal | ||
| Thermal conductivity | 16.2W/m·Ksourceat 100 °C | 37.5W/m·Ksourcetypical |
| Thermal expansion | 16.9µm/m·Ksourcemean, 0–100 °C | 11.3µm/m·Ksourcemean, -18 to 93 °C |
| 100 mm part over a 50 °C swing | 84.5µm growth | 56.5µm growth50% less |
| Specific heat | 500J/kg·Ksourcemean, 0–100 °C | 448J/kg·Ksourcetypical |
| Heats up and cools (diffusivity) | 4.03mm²/s | 10.7mm²/s2.64x faster |
| Thermal shock resistance | 838W/m | 11,678W/m13.9x more resistant |
| Melting point | 1,399–1,454°Csourcemelting range | not sourced |
| Max service temperature | 899°Csourcecontinuous, oxidation (scaling) limit in air | not sourced |
| Values for | Type 304, annealed flat-rolled (Cleveland-Cliffs 304/304L Product Data Bulletin, May 2021); 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 304 stronger than Steel AISI 4340?
Steel AISI 4340 is stronger: its yield strength is 1,035 MPa against 241 MPa for Stainless 304 (4.29x).
Which is lighter, Stainless 304 or Steel AISI 4340?
Steel AISI 4340 is lighter: 7,840 kg/m³ against 8,030 kg/m³ for Stainless 304.
Which is stiffer, Stainless 304 or Steel AISI 4340?
Steel AISI 4340 is stiffer: Young's modulus 200 GPa against 193 GPa for Stainless 304, so the same part in Steel AISI 4340 deflects less under the same load.
Which is lighter for the same job, Stainless 304 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 304 | Steel AISI 4340 |
|---|---|---|
| Stiff rod or tie (tension) | 6% heavier | lighter |
| Stiff beam (bending) | 4% heavier | lighter |
| Stiff panel or plate | 4% heavier | lighter |
| Strong rod or tie | 4.4x heavier | lighter |
| Strong beam | 2.71x heavier | lighter |
| Strong panel or plate | 2.12x 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 304 or Steel AISI 4340?
Steel AISI 4340 conducts heat better: 37.5 W/m·K against 16.2 W/m·K for Stainless 304.
Which expands less with temperature?
Steel AISI 4340 expands less: 11.3 µm/m·K against 16.9 µm/m·K for Stainless 304.