SAE-AISI 4340M Steel vs. ASTM A387 Grade 91 Class 2
Both SAE-AISI 4340M steel and ASTM A387 grade 91 class 2 are iron alloys. They have a moderately high 91% of their average alloy composition in common. There are 32 material properties with values for both materials. Properties with values for just one material (3, in this case) are not shown.
For each property being compared, the top bar is SAE-AISI 4340M steel and the bottom bar is ASTM A387 grade 91 class 2.
Metric UnitsUS Customary Units
Mechanical Properties
| Brinell Hardness | 710 | |
| 200 |
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 190 |
| Elongation at Break, % | 6.0 | |
| 20 |
| Fatigue Strength, MPa | 690 | |
| 330 |
| Poisson's Ratio | 0.29 | |
| 0.28 |
| Shear Modulus, GPa | 72 | |
| 75 |
| Shear Strength, MPa | 1360 | |
| 420 |
| Tensile Strength: Ultimate (UTS), MPa | 2340 | |
| 670 |
| Tensile Strength: Yield (Proof), MPa | 1240 | |
| 470 |
Thermal Properties
| Latent Heat of Fusion, J/g | 280 | |
| 270 |
| Maximum Temperature: Mechanical, °C | 430 | |
| 600 |
| Melting Completion (Liquidus), °C | 1440 | |
| 1460 |
| Melting Onset (Solidus), °C | 1400 | |
| 1420 |
| Specific Heat Capacity, J/kg-K | 480 | |
| 470 |
| Thermal Conductivity, W/m-K | 38 | |
| 26 |
| Thermal Expansion, µm/m-K | 13 | |
| 13 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 7.8 | |
| 8.9 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 9.1 | |
| 10 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 3.9 | |
| 7.0 |
| Density, g/cm3 | 7.8 | |
| 7.8 |
| Embodied Carbon, kg CO2/kg material | 1.9 | |
| 2.6 |
| Embodied Energy, MJ/kg | 26 | |
| 37 |
| Embodied Water, L/kg | 55 | |
| 88 |
Common Calculations
| PREN (Pitting Resistance) | 2.2 | |
| 13 |
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 120 | |
| 120 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 4120 | |
| 580 |
| Stiffness to Weight: Axial, points | 13 | |
| 14 |
| Stiffness to Weight: Bending, points | 25 | |
| 25 |
| Strength to Weight: Axial, points | 84 | |
| 24 |
| Strength to Weight: Bending, points | 51 | |
| 22 |
| Thermal Diffusivity, mm2/s | 10 | |
| 6.9 |
| Thermal Shock Resistance, points | 70 | |
| 19 |
Alloy Composition
| Aluminum (Al), % | 0 | |
| 0 to 0.020 |
| Carbon (C), % | 0.38 to 0.43 | |
| 0.080 to 0.12 |
| Chromium (Cr), % | 0.7 to 1.0 | |
| 8.0 to 9.5 |
| Iron (Fe), % | 93.3 to 94.8 | |
| 87.3 to 90.3 |
| Manganese (Mn), % | 0.65 to 0.9 | |
| 0.3 to 0.6 |
| Molybdenum (Mo), % | 0.35 to 0.45 | |
| 0.85 to 1.1 |
| Nickel (Ni), % | 1.7 to 2.0 | |
| 0 to 0.4 |
| Niobium (Nb), % | 0 | |
| 0.060 to 0.1 |
| Nitrogen (N), % | 0 | |
| 0.030 to 0.070 |
| Phosphorus (P), % | 0 to 0.012 | |
| 0 to 0.020 |
| Silicon (Si), % | 1.5 to 1.8 | |
| 0.2 to 0.5 |
| Sulfur (S), % | 0 to 0.012 | |
| 0 to 0.010 |
| Titanium (Ti), % | 0 | |
| 0 to 0.010 |
| Vanadium (V), % | 0.050 to 0.1 | |
| 0.18 to 0.25 |
| Zirconium (Zr), % | 0 | |
| 0 to 0.010 |