ASTM A387 Grade 21 Steel vs. R30003 Cobalt
ASTM A387 grade 21 steel belongs to the iron alloys classification, while R30003 cobalt belongs to the cobalt alloys. They have a modest 20% of their average alloy composition in common, which, by itself, doesn't mean much. There are 27 material properties with values for both materials. Properties with values for just one material (5, 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 R30003 cobalt.
Metric UnitsUS Customary Units
Mechanical Properties
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 210 |
| Elongation at Break, % | 21 | |
| 10 to 73 |
| Fatigue Strength, MPa | 160 to 250 | |
| 320 to 560 |
| Poisson's Ratio | 0.29 | |
| 0.29 |
| Shear Modulus, GPa | 74 | |
| 83 |
| Tensile Strength: Ultimate (UTS), MPa | 500 to 590 | |
| 970 to 1720 |
| Tensile Strength: Yield (Proof), MPa | 230 to 350 | |
| 510 to 1090 |
Thermal Properties
| Latent Heat of Fusion, J/g | 260 | |
| 310 |
| Melting Completion (Liquidus), °C | 1470 | |
| 1400 |
| Melting Onset (Solidus), °C | 1430 | |
| 1440 |
| Specific Heat Capacity, J/kg-K | 470 | |
| 450 |
| Thermal Conductivity, W/m-K | 41 | |
| 13 |
| Thermal Expansion, µm/m-K | 13 | |
| 13 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 7.6 | |
| 2.0 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 8.8 | |
| 2.1 |
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 | |
| 8.0 |
| Embodied Energy, MJ/kg | 23 | |
| 110 |
| Embodied Water, L/kg | 62 | |
| 400 |
Common Calculations
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 140 to 320 | |
| 600 to 2790 |
| Stiffness to Weight: Axial, points | 13 | |
| 14 |
| Stiffness to Weight: Bending, points | 24 | |
| 24 |
| Strength to Weight: Axial, points | 18 to 21 | |
| 32 to 57 |
| Strength to Weight: Bending, points | 18 to 20 | |
| 26 to 38 |
| Thermal Diffusivity, mm2/s | 11 | |
| 3.3 |
| Thermal Shock Resistance, points | 14 to 17 | |
| 26 to 45 |
Alloy Composition
| Boron (B), % | 0 | |
| 0 to 0.1 |
| Carbon (C), % | 0.050 to 0.15 | |
| 0 to 0.15 |
| Chromium (Cr), % | 2.8 to 3.3 | |
| 19 to 21 |
| Cobalt (Co), % | 0 | |
| 39 to 41 |
| Iron (Fe), % | 94.4 to 96 | |
| 10 to 20.5 |
| Manganese (Mn), % | 0.3 to 0.6 | |
| 1.5 to 2.5 |
| Molybdenum (Mo), % | 0.9 to 1.1 | |
| 6.0 to 8.0 |
| Nickel (Ni), % | 0 | |
| 14 to 16 |
| 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 |