SAE-AISI 8640 Steel vs. SAE-AISI 9255 Steel
Both SAE-AISI 8640 steel and SAE-AISI 9255 steel are iron alloys. Both are furnished in the annealed condition. They have a very high 98% of their average alloy composition in common.
For each property being compared, the top bar is SAE-AISI 8640 steel and the bottom bar is SAE-AISI 9255 steel.
Metric UnitsUS Customary Units
Mechanical Properties
| Brinell Hardness | 170 | |
| 200 |
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 190 |
| Elongation at Break, % | 23 | |
| 21 |
| Fatigue Strength, MPa | 270 | |
| 270 |
| Poisson's Ratio | 0.29 | |
| 0.29 |
| Shear Modulus, GPa | 73 | |
| 72 |
| Shear Strength, MPa | 360 | |
| 430 |
| Tensile Strength: Ultimate (UTS), MPa | 570 | |
| 680 |
| Tensile Strength: Yield (Proof), MPa | 380 | |
| 390 |
Thermal Properties
| Latent Heat of Fusion, J/g | 250 | |
| 280 |
| Maximum Temperature: Mechanical, °C | 410 | |
| 400 |
| Melting Completion (Liquidus), °C | 1460 | |
| 1430 |
| Melting Onset (Solidus), °C | 1420 | |
| 1390 |
| Specific Heat Capacity, J/kg-K | 470 | |
| 480 |
| Thermal Conductivity, W/m-K | 39 | |
| 46 |
| Thermal Expansion, µm/m-K | 13 | |
| 13 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 7.3 | |
| 7.4 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 8.4 | |
| 8.6 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 2.6 | |
| 2.0 |
| Density, g/cm3 | 7.8 | |
| 7.7 |
| Embodied Carbon, kg CO2/kg material | 1.5 | |
| 1.5 |
| Embodied Energy, MJ/kg | 20 | |
| 20 |
| Embodied Water, L/kg | 50 | |
| 46 |
Common Calculations
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 120 | |
| 120 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 380 | |
| 400 |
| Stiffness to Weight: Axial, points | 13 | |
| 13 |
| Stiffness to Weight: Bending, points | 24 | |
| 25 |
| Strength to Weight: Axial, points | 20 | |
| 24 |
| Strength to Weight: Bending, points | 20 | |
| 22 |
| Thermal Diffusivity, mm2/s | 10 | |
| 13 |
| Thermal Shock Resistance, points | 17 | |
| 21 |
Alloy Composition
| Carbon (C), % | 0.38 to 0.43 | |
| 0.51 to 0.59 |
| Chromium (Cr), % | 0.4 to 0.6 | |
| 0 |
| Iron (Fe), % | 96.6 to 97.8 | |
| 96.2 to 97 |
| Manganese (Mn), % | 0.75 to 1.0 | |
| 0.7 to 1.0 |
| Molybdenum (Mo), % | 0.15 to 0.25 | |
| 0 |
| Nickel (Ni), % | 0.4 to 0.7 | |
| 0 |
| Phosphorus (P), % | 0 to 0.035 | |
| 0 to 0.035 |
| Silicon (Si), % | 0.15 to 0.35 | |
| 1.8 to 2.2 |
| Sulfur (S), % | 0 to 0.040 | |
| 0 to 0.040 |