Materials / Compare
Steel AISI 4340 vs. Plastic UHMWPE
Compare Steel AISI 4340 vs. Plastic UHMWPE 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 | 1,035MPasourcetypical, transverse | 20MPasourcetypical, tensile stress at yield ISO 527, 50 mm/min |
| Ultimate tensile strength | 1,140MPasourcetypical, transverse | 43MPasourcetypical, tensile stress at break ISO 527, 50 mm/min |
| Elongation at break | 18%sourcetypical, transverse | 465%sourcetypical, nominal elongation at break ISO 527 |
| Young's modulus (stiffness) | 200GPasourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered) | 0.66GPasourcetypical, tensile modulus ISO 527, 1 mm/min |
| Density | 7,840kg/m³sourcetypical | 930kg/m³sourcetypical8.43x lighter |
| Strength to weight | 132kN·m/kg6.14x higher | 21.5kN·m/kg |
| Stiffness to weight | 25.5MN·m/kg35.9x higher | 0.71MN·m/kg |
| Poisson's ratio | 0.32sourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered) | not sourced |
| Shear modulus | 75.7GPa | not sourced |
| Bulk modulus | 185GPa | not sourced |
| Speed of sound | 5,049m/s | 842m/s |
| Thermal | ||
| Thermal conductivity | 37.5W/m·Ksourcetypical | 0.4W/m·Ksourcetypical, unfilled (narrative value, generic Celanese UHMWPE) |
| Thermal expansion | 11.3µm/m·Ksourcemean, -18 to 93 °C | 200µm/m·Ksourcetypical, 20 to 100 °C (generic Celanese UHMWPE) |
| 100 mm part over a 50 °C swing | 56.5µm growth17.7x less | 1,000µm growth |
| Specific heat | 448J/kg·Ksourcetypical | not sourced |
| Heats up and cools (diffusivity) | 10.7mm²/s | not sourced |
| Thermal shock resistance | 11,678W/m | not sourced |
| Melting point | not sourced | 130–138°CsourceDSC 10 K/min |
| Max service temperature | not sourced | 80°Csourcerecommended max constant operating temperature |
| Values for | Carpenter (Latrobe) Lescalloy 4340 VAC-ARC datasheet; mechanical row for 1100 °F temper; physical properties grade-level | Celanese GUR 4120 (avg. molecular weight 4.7x10^6 g/mol), typical values on compression-molded specimens; CTE and thermal conductivity from Celanese's generic UHMWPE guide (grade not named) |
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 Steel AISI 4340 stronger than Plastic UHMWPE?
Steel AISI 4340 is stronger: its yield strength is 1,035 MPa against 20 MPa for Plastic UHMWPE (51.8x).
Which is lighter, Steel AISI 4340 or Plastic UHMWPE?
Plastic UHMWPE is lighter: 930 kg/m³ against 7,840 kg/m³ for Steel AISI 4340.
Which is stiffer, Steel AISI 4340 or Plastic UHMWPE?
Steel AISI 4340 is stiffer: Young's modulus 200 GPa against 0.66 GPa for Plastic UHMWPE, so the same part in Steel AISI 4340 deflects less under the same load.
Which is lighter for the same job, Steel AISI 4340 or Plastic UHMWPE?
For the same stiffness or strength: Steel AISI 4340 is lighter for a stiff rod or tie (tension), stiff beam (bending), strong rod or tie, strong beam; Plastic UHMWPE is lighter for a stiff panel or plate, strong panel or plate.
| Part that must be | Steel AISI 4340 | Plastic UHMWPE |
|---|---|---|
| Stiff rod or tie (tension) | lighter | 35.9x heavier |
| Stiff beam (bending) | lighter | 2.06x heavier |
| Stiff panel or plate | 26% heavier | lighter |
| Strong rod or tie | lighter | 6.14x heavier |
| Strong beam | lighter | 1.65x heavier |
| Strong panel or plate | 17% 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, Steel AISI 4340 or Plastic UHMWPE?
Steel AISI 4340 conducts heat better: 37.5 W/m·K against 0.4 W/m·K for Plastic UHMWPE.
Which expands less with temperature?
Steel AISI 4340 expands less: 11.3 µm/m·K against 200 µm/m·K for Plastic UHMWPE.