SAE-AISI 8740 Steel vs. ASTM A387 Grade 21 Steel
Both SAE-AISI 8740 steel and ASTM A387 grade 21 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 (1, in this case) are not shown.
For each property being compared, the top bar is SAE-AISI 8740 steel and the bottom bar is ASTM A387 grade 21 steel.
Metric UnitsUS Customary Units
Mechanical Properties
| Brinell Hardness | 170 to 200 | |
| 150 to 180 |
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 190 |
| Elongation at Break, % | 11 to 23 | |
| 21 |
| Fatigue Strength, MPa | 270 to 350 | |
| 160 to 250 |
| Poisson's Ratio | 0.29 | |
| 0.29 |
| Shear Modulus, GPa | 73 | |
| 74 |
| Shear Strength, MPa | 370 to 400 | |
| 310 to 370 |
| Tensile Strength: Ultimate (UTS), MPa | 580 to 670 | |
| 500 to 590 |
| Tensile Strength: Yield (Proof), MPa | 380 to 570 | |
| 230 to 350 |
Thermal Properties
| Latent Heat of Fusion, J/g | 250 | |
| 260 |
| Maximum Temperature: Mechanical, °C | 410 | |
| 480 |
| Melting Completion (Liquidus), °C | 1460 | |
| 1470 |
| Melting Onset (Solidus), °C | 1420 | |
| 1430 |
| Specific Heat Capacity, J/kg-K | 470 | |
| 470 |
| Thermal Conductivity, W/m-K | 39 | |
| 41 |
| Thermal Expansion, µm/m-K | 13 | |
| 13 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 7.3 | |
| 7.6 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 8.4 | |
| 8.8 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 2.6 | |
| 4.1 |
| Density, g/cm3 | 7.8 | |
| 7.9 |
| Embodied Carbon, kg CO2/kg material | 1.5 | |
| 1.8 |
| Embodied Energy, MJ/kg | 20 | |
| 23 |
| Embodied Water, L/kg | 50 | |
| 62 |
Common Calculations
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 71 to 120 | |
| 84 to 110 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 390 to 850 | |
| 140 to 320 |
| Stiffness to Weight: Axial, points | 13 | |
| 13 |
| Stiffness to Weight: Bending, points | 24 | |
| 24 |
| Strength to Weight: Axial, points | 20 to 24 | |
| 18 to 21 |
| Strength to Weight: Bending, points | 20 to 22 | |
| 18 to 20 |
| Thermal Diffusivity, mm2/s | 10 | |
| 11 |
| Thermal Shock Resistance, points | 17 to 20 | |
| 14 to 17 |
Alloy Composition
| Carbon (C), % | 0.38 to 0.43 | |
| 0.050 to 0.15 |
| Chromium (Cr), % | 0.4 to 0.6 | |
| 2.8 to 3.3 |
| Iron (Fe), % | 96.5 to 97.7 | |
| 94.4 to 96 |
| Manganese (Mn), % | 0.75 to 1.0 | |
| 0.3 to 0.6 |
| Molybdenum (Mo), % | 0.2 to 0.3 | |
| 0.9 to 1.1 |
| Nickel (Ni), % | 0.4 to 0.7 | |
| 0 |
| Phosphorus (P), % | 0 to 0.035 | |
| 0 to 0.025 |
| Silicon (Si), % | 0.15 to 0.35 | |
| 0 to 0.5 |
| Sulfur (S), % | 0 to 0.040 | |
| 0 to 0.025 |