Materials / Compare
Plastic Nylon PA6 vs. Steel AISI 4340
Compare Plastic Nylon PA6 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 | 90MPasourcetypical, dry | 1,035MPasourcetypical, transverse |
| Ultimate tensile strength | not sourced | 1,140MPasourcetypical, transverse |
| Elongation at break | 10%sourcenominal strain at break, dry | 18%sourcetypical, transverse |
| Young's modulus (stiffness) | 3.5GPasourcetypical, dry | 200GPasourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered) |
| Density | 1,130kg/m³sourcetypical6.94x lighter | 7,840kg/m³sourcetypical |
| Strength to weight | 79.6kN·m/kg | 132kN·m/kg1.66x higher |
| Stiffness to weight | 3.1MN·m/kg | 25.5MN·m/kg8.23x higher |
| Poisson's ratio | 0.4sourcebase material: unfilled polyamide (PA), conditioned, maker design-guide family value (Covestro Table 3-1) | 0.32sourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered) |
| Shear modulus | 1.25GPa | 75.7GPa60.6x stiffer in shear |
| Bulk modulus | 5.83GPa | 185GPa |
| Speed of sound | 1,760m/s | 5,049m/s |
| Thermal | ||
| Thermal conductivity | 0.33W/m·Ksourcetypical | 37.5W/m·Ksourcetypical114x more heat through a fin |
| Thermal expansion | 102µm/m·Ksourcelongitudinal, 23-55 °C | 11.3µm/m·Ksourcemean, -18 to 93 °C |
| 100 mm part over a 50 °C swing | 510µm growth | 56.5µm growth9.03x less |
| Specific heat | 1,700J/kg·Ksourcetypical | 448J/kg·Ksourcetypical |
| Heats up and cools (diffusivity) | 0.172mm²/s | 10.7mm²/s62.1x faster |
| Thermal shock resistance | 49.9W/m | 11,678W/m234x more resistant |
| Melting point | 220°CsourceDSC | not sourced |
| Max service temperature | 87°CsourceIEC 60216 temperature index, 20000 h | not sourced |
| Values for | BASF Ultramid B3S (PA6, unreinforced injection-moulding grade), Product Information 02/2026, dry values (ISO methods) | 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 Plastic Nylon PA6 stronger than Steel AISI 4340?
Steel AISI 4340 is stronger: its yield strength is 1,035 MPa against 90 MPa for Plastic Nylon PA6 (11.5x).
Which is lighter, Plastic Nylon PA6 or Steel AISI 4340?
Plastic Nylon PA6 is lighter: 1,130 kg/m³ against 7,840 kg/m³ for Steel AISI 4340.
Which is stiffer, Plastic Nylon PA6 or Steel AISI 4340?
Steel AISI 4340 is stiffer: Young's modulus 200 GPa against 3.5 GPa for Plastic Nylon PA6, so the same part in Steel AISI 4340 deflects less under the same load.
Which is lighter for the same job, Plastic Nylon PA6 or Steel AISI 4340?
For the same stiffness or strength: Plastic Nylon PA6 is lighter for a stiff panel or plate, strong beam, strong panel or plate; Steel AISI 4340 is lighter for a stiff rod or tie (tension), stiff beam (bending), strong rod or tie.
| Part that must be | Plastic Nylon PA6 | Steel AISI 4340 |
|---|---|---|
| Stiff rod or tie (tension) | 8.23x heavier | lighter |
| Stiff beam (bending) | 9% heavier | lighter |
| Stiff panel or plate | lighter | 1.8x heavier |
| Strong rod or tie | 1.66x heavier | lighter |
| Strong beam | lighter | 36% heavier |
| Strong panel or plate | lighter | 2.05x heavier |
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, Plastic Nylon PA6 or Steel AISI 4340?
Steel AISI 4340 conducts heat better: 37.5 W/m·K against 0.33 W/m·K for Plastic Nylon PA6.
Which expands less with temperature?
Steel AISI 4340 expands less: 11.3 µm/m·K against 102 µm/m·K for Plastic Nylon PA6.