SAE-AISI 4340M Steel vs. SAE-AISI 8645 Steel
Both SAE-AISI 4340M steel and SAE-AISI 8645 steel are iron alloys. They have a very high 97% of their average alloy composition in common. There are 31 material properties with values for both materials. Properties with values for just one material (4, in this case) are not shown.
For each property being compared, the top bar is SAE-AISI 4340M steel and the bottom bar is SAE-AISI 8645 steel.
Metric UnitsUS Customary Units
Mechanical Properties
| Brinell Hardness | 710 | |
| 180 to 200 |
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 190 |
| Elongation at Break, % | 6.0 | |
| 12 to 23 |
| Fatigue Strength, MPa | 690 | |
| 280 to 350 |
| Poisson's Ratio | 0.29 | |
| 0.29 |
| Shear Modulus, GPa | 72 | |
| 73 |
| Shear Strength, MPa | 1360 | |
| 380 to 400 |
| Tensile Strength: Ultimate (UTS), MPa | 2340 | |
| 600 to 670 |
| Tensile Strength: Yield (Proof), MPa | 1240 | |
| 390 to 560 |
Thermal Properties
| Latent Heat of Fusion, J/g | 280 | |
| 250 |
| Maximum Temperature: Mechanical, °C | 430 | |
| 410 |
| 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 | |
| 39 |
| Thermal Expansion, µm/m-K | 13 | |
| 13 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 7.8 | |
| 7.3 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 9.1 | |
| 8.4 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 3.9 | |
| 2.6 |
| Density, g/cm3 | 7.8 | |
| 7.8 |
| Embodied Carbon, kg CO2/kg material | 1.9 | |
| 1.5 |
| Embodied Energy, MJ/kg | 26 | |
| 20 |
| Embodied Water, L/kg | 55 | |
| 50 |
Common Calculations
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 120 | |
| 77 to 120 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 4120 | |
| 420 to 840 |
| Stiffness to Weight: Axial, points | 13 | |
| 13 |
| Stiffness to Weight: Bending, points | 25 | |
| 24 |
| Strength to Weight: Axial, points | 84 | |
| 21 to 24 |
| Strength to Weight: Bending, points | 51 | |
| 20 to 22 |
| Thermal Diffusivity, mm2/s | 10 | |
| 10 |
| Thermal Shock Resistance, points | 70 | |
| 18 to 20 |
Alloy Composition
| Carbon (C), % | 0.38 to 0.43 | |
| 0.43 to 0.48 |
| Chromium (Cr), % | 0.7 to 1.0 | |
| 0.4 to 0.6 |
| Iron (Fe), % | 93.3 to 94.8 | |
| 96.5 to 97.7 |
| Manganese (Mn), % | 0.65 to 0.9 | |
| 0.75 to 1.0 |
| Molybdenum (Mo), % | 0.35 to 0.45 | |
| 0.15 to 0.25 |
| Nickel (Ni), % | 1.7 to 2.0 | |
| 0.4 to 0.7 |
| Phosphorus (P), % | 0 to 0.012 | |
| 0 to 0.035 |
| Silicon (Si), % | 1.5 to 1.8 | |
| 0.15 to 0.35 |
| Sulfur (S), % | 0 to 0.012 | |
| 0 to 0.040 |
| Vanadium (V), % | 0.050 to 0.1 | |
| 0 |