Materials / Compare
Iron vs. Stainless 304
Compare Iron vs. Stainless 304 strength, stiffness, weight and thermal properties.
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|---|---|---|
| Mechanical | ||
| Yield strength | 186MPasourcetypical (0.2% YS), hot rolled + SRA/recrystallization anneal | 241MPasourcetypical, annealed, 70 °F (21 °C) |
| Ultimate tensile strength | 290MPasourcetypical, SRA/recrystallization anneal | 586MPasourcetypical, annealed, 70 °F (21 °C) |
| Elongation at break | 38%sourcetypical, gauge 4D0 | 55%sourcetypical, annealed, in 2 in. (50.8 mm) |
| Young's modulus (stiffness) | 207GPasourcetypical, after SRA/recrystallization anneal | 193GPasourcetypical, in tension |
| Density | 7,860kg/m³sourcetypical | 8,030kg/m³sourcetypical |
| Strength to weight | 23.7kN·m/kg | 30kN·m/kg27% higher |
| Stiffness to weight | 26.3MN·m/kg10% higher | 24MN·m/kg |
| Poisson's ratio | 0.282sourceNIST critically evaluated best value (polycrystalline iron) | 0.3sourcedesign value (structural stainless steels) |
| Shear modulus | 80.7GPa9% stiffer in shear | 74.2GPa |
| Bulk modulus | 158GPa | 161GPa |
| Speed of sound | 5,132m/s | 4,903m/s |
| Thermal | ||
| Thermal conductivity | 73.2W/m·Ksourcetypical at 20 °C | 16.2W/m·Ksourceat 100 °C |
| Thermal expansion | 13.7µm/m·Ksourcemean, 20-399 °C | 16.9µm/m·Ksourcemean, 0–100 °C |
| 100 mm part over a 50 °C swing | 68.5µm growth23% less | 84.5µm growth |
| Specific heat | 450J/kg·Ksourcetypical | 500J/kg·Ksourcemean, 0–100 °C |
| Heats up and cools (diffusivity) | 20.7mm²/s5.13x faster | 4.03mm²/s |
| Thermal shock resistance | 3,447W/m4.11x more resistant | 838W/m |
| Melting point | 1,532°Csourcetypical | 1,399–1,454°Csourcemelting range |
| Max service temperature | not sourced | 899°Csourcecontinuous, oxidation (scaling) limit in air |
| Values for | Cleveland-Cliffs / AK Steel ARMCO Pure Iron Product Data Bulletin (07/2022): Table 1 typical physical properties, Table 2 typical mechanical properties after SRA/recrystallization anneal. | 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 |
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 Iron stronger than Stainless 304?
Stainless 304 is stronger: its yield strength is 241 MPa against 186 MPa for Iron (30%).
Which is lighter, Iron or Stainless 304?
Iron is lighter: 7,860 kg/m³ against 8,030 kg/m³ for Stainless 304.
Which is stiffer, Iron or Stainless 304?
Iron is stiffer: Young's modulus 207 GPa against 193 GPa for Stainless 304, so the same part in Iron deflects less under the same load.
Which is lighter for the same job, Iron or Stainless 304?
For the same stiffness or strength: Iron is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate; Stainless 304 is lighter for a strong rod or tie, strong beam, strong panel or plate.
| Part that must be | Iron | Stainless 304 |
|---|---|---|
| Stiff rod or tie (tension) | lighter | 10% heavier |
| Stiff beam (bending) | lighter | 6% heavier |
| Stiff panel or plate | lighter | 5% heavier |
| Strong rod or tie | 27% heavier | lighter |
| Strong beam | 16% heavier | lighter |
| Strong panel or plate | 11% 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, Iron or Stainless 304?
Iron conducts heat better: 73.2 W/m·K against 16.2 W/m·K for Stainless 304.
Which expands less with temperature?
Iron expands less: 13.7 µm/m·K against 16.9 µm/m·K for Stainless 304.