ASTM A387 Grade 21 Steel vs. R30155 Cobalt
Both ASTM A387 grade 21 steel and R30155 cobalt are iron alloys. They have a modest 35% of their average alloy composition in common, which, by itself, doesn't mean much. There are 30 material properties with values for both materials. Properties with values for just one material (4, 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 R30155 cobalt.
Metric UnitsUS Customary Units
Mechanical Properties
| Brinell Hardness | 150 to 180 | |
| 220 |
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 210 |
| Elongation at Break, % | 21 | |
| 34 |
| Fatigue Strength, MPa | 160 to 250 | |
| 310 |
| Poisson's Ratio | 0.29 | |
| 0.29 |
| Shear Modulus, GPa | 74 | |
| 81 |
| Shear Strength, MPa | 310 to 370 | |
| 570 |
| Tensile Strength: Ultimate (UTS), MPa | 500 to 590 | |
| 850 |
| Tensile Strength: Yield (Proof), MPa | 230 to 350 | |
| 390 |
Thermal Properties
| Latent Heat of Fusion, J/g | 260 | |
| 300 |
| Maximum Temperature: Mechanical, °C | 480 | |
| 1100 |
| Melting Completion (Liquidus), °C | 1470 | |
| 1470 |
| Melting Onset (Solidus), °C | 1430 | |
| 1420 |
| Specific Heat Capacity, J/kg-K | 470 | |
| 450 |
| Thermal Conductivity, W/m-K | 41 | |
| 12 |
| Thermal Expansion, µm/m-K | 13 | |
| 14 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 4.1 | |
| 80 |
| Density, g/cm3 | 7.9 | |
| 8.5 |
| Embodied Carbon, kg CO2/kg material | 1.8 | |
| 9.7 |
| Embodied Energy, MJ/kg | 23 | |
| 150 |
| Embodied Water, L/kg | 62 | |
| 300 |
Common Calculations
| PREN (Pitting Resistance) | 6.4 | |
| 37 |
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 84 to 110 | |
| 230 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 140 to 320 | |
| 370 |
| Stiffness to Weight: Axial, points | 13 | |
| 14 |
| Stiffness to Weight: Bending, points | 24 | |
| 23 |
| Strength to Weight: Axial, points | 18 to 21 | |
| 28 |
| Strength to Weight: Bending, points | 18 to 20 | |
| 24 |
| Thermal Diffusivity, mm2/s | 11 | |
| 3.2 |
| Thermal Shock Resistance, points | 14 to 17 | |
| 21 |
Alloy Composition
| Carbon (C), % | 0.050 to 0.15 | |
| 0.080 to 0.16 |
| Chromium (Cr), % | 2.8 to 3.3 | |
| 20 to 22.5 |
| Cobalt (Co), % | 0 | |
| 18.5 to 21 |
| Iron (Fe), % | 94.4 to 96 | |
| 24.3 to 36.2 |
| Manganese (Mn), % | 0.3 to 0.6 | |
| 1.0 to 2.0 |
| Molybdenum (Mo), % | 0.9 to 1.1 | |
| 2.5 to 3.5 |
| Nickel (Ni), % | 0 | |
| 19 to 21 |
| Niobium (Nb), % | 0 | |
| 0.75 to 1.3 |
| Nitrogen (N), % | 0 | |
| 0 to 0.2 |
| Phosphorus (P), % | 0 to 0.025 | |
| 0 to 0.040 |
| Silicon (Si), % | 0 to 0.5 | |
| 0 to 1.0 |
| Sulfur (S), % | 0 to 0.025 | |
| 0 to 0.030 |
| Tantalum (Ta), % | 0 | |
| 0.75 to 1.3 |
| Tungsten (W), % | 0 | |
| 2.0 to 3.0 |