ASTM A387 Grade 21 Steel vs. R30008 Cobalt
ASTM A387 grade 21 steel belongs to the iron alloys classification, while R30008 cobalt belongs to the cobalt alloys. There are 23 material properties with values for both materials. Properties with values for just one material (9, in this case) are not shown.
For each property being compared, the top bar is ASTM A387 grade 21 steel and the bottom bar is R30008 cobalt.
Metric UnitsUS Customary Units
Mechanical Properties
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 210 |
| Elongation at Break, % | 21 | |
| 1.1 to 73 |
| Fatigue Strength, MPa | 160 to 250 | |
| 320 to 530 |
| Poisson's Ratio | 0.29 | |
| 0.29 |
| Shear Modulus, GPa | 74 | |
| 83 |
| Tensile Strength: Ultimate (UTS), MPa | 500 to 590 | |
| 950 to 1700 |
| Tensile Strength: Yield (Proof), MPa | 230 to 350 | |
| 500 to 1080 |
Thermal Properties
| Latent Heat of Fusion, J/g | 260 | |
| 320 |
| Melting Completion (Liquidus), °C | 1470 | |
| 1400 |
| Melting Onset (Solidus), °C | 1430 | |
| 1330 |
| Specific Heat Capacity, J/kg-K | 470 | |
| 450 |
| Thermal Expansion, µm/m-K | 13 | |
| 13 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 4.1 | |
| 95 |
| Density, g/cm3 | 7.9 | |
| 8.4 |
| Embodied Carbon, kg CO2/kg material | 1.8 | |
| 8.1 |
| Embodied Energy, MJ/kg | 23 | |
| 110 |
| Embodied Water, L/kg | 62 | |
| 400 |
Common Calculations
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 140 to 320 | |
| 590 to 2720 |
| Stiffness to Weight: Axial, points | 13 | |
| 14 |
| Stiffness to Weight: Bending, points | 24 | |
| 24 |
| Strength to Weight: Axial, points | 18 to 21 | |
| 31 to 56 |
| Strength to Weight: Bending, points | 18 to 20 | |
| 25 to 37 |
| Thermal Shock Resistance, points | 14 to 17 | |
| 25 to 44 |
Alloy Composition
| Boron (B), % | 0 | |
| 0 to 0.0010 |
| Carbon (C), % | 0.050 to 0.15 | |
| 0 to 0.15 |
| Chromium (Cr), % | 2.8 to 3.3 | |
| 18.5 to 21.5 |
| Cobalt (Co), % | 0 | |
| 39 to 42 |
| Iron (Fe), % | 94.4 to 96 | |
| 7.6 to 20 |
| Manganese (Mn), % | 0.3 to 0.6 | |
| 1.0 to 2.0 |
| Molybdenum (Mo), % | 0.9 to 1.1 | |
| 6.5 to 7.5 |
| Nickel (Ni), % | 0 | |
| 15 to 18 |
| Phosphorus (P), % | 0 to 0.025 | |
| 0 to 0.015 |
| Silicon (Si), % | 0 to 0.5 | |
| 0 to 1.2 |
| Sulfur (S), % | 0 to 0.025 | |
| 0 to 0.015 |