Materials / Compare
Stainless 303 vs. Steel AISI 4340
Compare Stainless 303 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 | 275MPasourceOutokumpu typical (product P = hot rolled plate, transverse) | 1,035MPasourcetypical, transverse |
| Ultimate tensile strength | 585MPasourceOutokumpu typical | 1,140MPasourcetypical, transverse |
| Elongation at break | 35%sourceOutokumpu typical, A5 | 18%sourcetypical, transverse |
| Young's modulus (stiffness) | 200GPasourceat RT (Table 12) | 200GPasourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered) |
| Density | 7,900kg/m³sourceat RT | 7,840kg/m³sourcetypical |
| Strength to weight | 34.8kN·m/kg | 132kN·m/kg3.79x higher |
| Stiffness to weight | 25.3MN·m/kg | 25.5MN·m/kg |
| 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 | 5,032m/s | 5,049m/s |
| Thermal | ||
| Thermal conductivity | 15W/m·Ksourceat RT | 37.5W/m·Ksourcetypical |
| Thermal expansion | 16µm/m·Ksourcemean, 20–100 °C | 11.3µm/m·Ksourcemean, -18 to 93 °C |
| 100 mm part over a 50 °C swing | 80µm growth | 56.5µm growth42% less |
| Specific heat | 500J/kg·Ksourceat RT | 448J/kg·Ksourcetypical |
| Heats up and cools (diffusivity) | 3.8mm²/s | 10.7mm²/s2.81x faster |
| Thermal shock resistance | 902W/m | 11,678W/m12.9x more resistant |
| Max service temperature | 871°Csourcecontinuous, scaling limit | not sourced |
| Values for | 1.4305 / UNS S30300, Outokumpu typical values (hot rolled, solution annealed) from 'Steel Grades, Properties and Global Standards'; max service from Carpenter CarTech 303 datasheet | 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 303 stronger than Steel AISI 4340?
Steel AISI 4340 is stronger: its yield strength is 1,035 MPa against 275 MPa for Stainless 303 (3.76x).
Which is lighter, Stainless 303 or Steel AISI 4340?
Steel AISI 4340 is lighter: 7,840 kg/m³ against 7,900 kg/m³ for Stainless 303.
Which is stiffer, Stainless 303 or Steel AISI 4340?
Stainless 303 is stiffer: Young's modulus 200 GPa against 200 GPa for Steel AISI 4340, so the same part in Stainless 303 deflects less under the same load.
Which is lighter for the same job, Stainless 303 or Steel AISI 4340?
For the same stiffness or strength: Steel AISI 4340 is lighter for a strong rod or tie, strong beam, strong panel or plate.
| Part that must be | Stainless 303 | Steel AISI 4340 |
|---|---|---|
| Stiff rod or tie (tension) | about equal | about equal |
| Stiff beam (bending) | about equal | about equal |
| Stiff panel or plate | about equal | about equal |
| Strong rod or tie | 3.79x heavier | lighter |
| Strong beam | 2.44x heavier | lighter |
| Strong panel or plate | 1.95x 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 303 or Steel AISI 4340?
Steel AISI 4340 conducts heat better: 37.5 W/m·K against 15 W/m·K for Stainless 303.
Which expands less with temperature?
Steel AISI 4340 expands less: 11.3 µm/m·K against 16 µm/m·K for Stainless 303.