Materials / Compare
Steel AISI 4340 vs. Steel A992
Compare Steel AISI 4340 vs. Steel A992 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 | 385MPasourcetypical: mean of 20,295 A992 flange mill-test coupons (1998 SSPC survey), as reported by AISC |
| Ultimate tensile strength | 1,140MPasourcetypical, transverse | 505MPasourcetypical: mean of 20,295 A992 flange mill-test coupons (1998 SSPC survey) |
| Elongation at break | 18%sourcetypical, transverse | not sourced |
| Young's modulus (stiffness) | 200GPasourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered) | 200GPasourcedesign value (AISC 360-16) |
| Density | 7,840kg/m³sourcetypical | 7,850kg/m³sourcenominal (constructional data) |
| Strength to weight | 132kN·m/kg2.69x higher | 49kN·m/kg |
| Stiffness to weight | 25.5MN·m/kg | 25.5MN·m/kg |
| Poisson's ratio | 0.32sourceMIL-HDBK-5J design value (AISI 4340, quenched and tempered) | 0.3sourcedesign value (AISC 360-16 Commentary) |
| Shear modulus | 75.7GPa | 76.9GPa2% stiffer in shear |
| Bulk modulus | 185GPa | 167GPa |
| Speed of sound | 5,049m/s | 5,048m/s |
| Thermal | ||
| Thermal conductivity | 37.5W/m·Ksourcetypical | 48W/m·Ksourcenominal at 20 °C |
| Thermal expansion | 11.3µm/m·Ksourcemean, -18 to 93 °C | 12µm/m·Ksourcenominal (constructional data, no temperature range stated) |
| 100 mm part over a 50 °C swing | 56.5µm growth6% less | 60µm growth |
| Specific heat | 448J/kg·Ksourcetypical | 460–480J/kg·Ksourcebase material: EN S275JR unalloyed structural steel (the EN counterpart of A36), typical, 50/100 °C |
| Heats up and cools (diffusivity) | 10.7mm²/s | 13mm²/s22% faster |
| Thermal shock resistance | 11,678W/m2.17x more resistant | 5,390W/m |
| Values for | Carpenter (Latrobe) Lescalloy 4340 VAC-ARC datasheet; mechanical row for 1100 °F temper; physical properties grade-level | ASTM A992 W-shapes; Fy/Fu specified minimums from AISC publications (AISC 360-16 Commentary; Modern Steel Construction); elastic constants AISC 360; physical constants from the bauforumstahl structural-steel EPD, which names A992 among covered product standards. |
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 Steel A992?
Steel AISI 4340 is stronger: its yield strength is 1,035 MPa against 385 MPa for Steel A992 (2.69x).
Which is lighter, Steel AISI 4340 or Steel A992?
Steel AISI 4340 is lighter: 7,840 kg/m³ against 7,850 kg/m³ for Steel A992.
Which is stiffer, Steel AISI 4340 or Steel A992?
Steel A992 is stiffer: Young's modulus 200 GPa against 200 GPa for Steel AISI 4340, so the same part in Steel A992 deflects less under the same load.
Which is lighter for the same job, Steel AISI 4340 or Steel A992?
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 | Steel AISI 4340 | Steel A992 |
|---|---|---|
| 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 | lighter | 2.69x heavier |
| Strong beam | lighter | 1.94x heavier |
| Strong panel or plate | lighter | 1.64x 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, Steel AISI 4340 or Steel A992?
Steel A992 conducts heat better: 48 W/m·K against 37.5 W/m·K for Steel AISI 4340.
Which expands less with temperature?
Steel AISI 4340 expands less: 11.3 µm/m·K against 12 µm/m·K for Steel A992.