ASTM A387 Grade 21 Steel vs. R30605 Cobalt
ASTM A387 grade 21 steel belongs to the iron alloys classification, while R30605 cobalt belongs to the cobalt alloys. There are 25 material properties with values for both materials. Properties with values for just one material (7, 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 R30605 cobalt.
Metric UnitsUS Customary Units
Mechanical Properties
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 210 |
| Elongation at Break, % | 21 | |
| 34 |
| Fatigue Strength, MPa | 160 to 250 | |
| 260 to 590 |
| Poisson's Ratio | 0.29 | |
| 0.29 |
| Shear Modulus, GPa | 74 | |
| 81 |
| Tensile Strength: Ultimate (UTS), MPa | 500 to 590 | |
| 1130 to 1900 |
| Tensile Strength: Yield (Proof), MPa | 230 to 350 | |
| 470 to 1600 |
Thermal Properties
| Latent Heat of Fusion, J/g | 260 | |
| 290 |
| Melting Completion (Liquidus), °C | 1470 | |
| 1410 |
| Melting Onset (Solidus), °C | 1430 | |
| 1330 |
| Specific Heat Capacity, J/kg-K | 470 | |
| 410 |
| Thermal Conductivity, W/m-K | 41 | |
| 9.6 |
| Thermal Expansion, µm/m-K | 13 | |
| 12 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 7.6 | |
| 2.0 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 8.8 | |
| 1.8 |
Otherwise Unclassified Properties
| Density, g/cm3 | 7.9 | |
| 9.6 |
| Embodied Carbon, kg CO2/kg material | 1.8 | |
| 9.8 |
| Embodied Energy, MJ/kg | 23 | |
| 140 |
| Embodied Water, L/kg | 62 | |
| 450 |
Common Calculations
| Stiffness to Weight: Axial, points | 13 | |
| 12 |
| Stiffness to Weight: Bending, points | 24 | |
| 21 |
| Strength to Weight: Axial, points | 18 to 21 | |
| 33 to 55 |
| Strength to Weight: Bending, points | 18 to 20 | |
| 25 to 36 |
| Thermal Diffusivity, mm2/s | 11 | |
| 2.5 |
| Thermal Shock Resistance, points | 14 to 17 | |
| 31 to 52 |
Alloy Composition
| Carbon (C), % | 0.050 to 0.15 | |
| 0.050 to 0.15 |
| Chromium (Cr), % | 2.8 to 3.3 | |
| 19 to 21 |
| Cobalt (Co), % | 0 | |
| 46.4 to 57 |
| Iron (Fe), % | 94.4 to 96 | |
| 0 to 3.0 |
| Manganese (Mn), % | 0.3 to 0.6 | |
| 1.0 to 2.0 |
| Molybdenum (Mo), % | 0.9 to 1.1 | |
| 0 |
| Nickel (Ni), % | 0 | |
| 9.0 to 11 |
| Phosphorus (P), % | 0 to 0.025 | |
| 0 to 0.040 |
| Silicon (Si), % | 0 to 0.5 | |
| 0 to 0.4 |
| Sulfur (S), % | 0 to 0.025 | |
| 0 to 0.030 |
| Tungsten (W), % | 0 | |
| 14 to 16 |