ASTM A387 Grade 21 Steel vs. ASTM A372 Grade K Steel
Both ASTM A387 grade 21 steel and ASTM A372 grade K steel are iron alloys. They have a very high 97% of their average alloy composition in common.
For each property being compared, the top bar is ASTM A387 grade 21 steel and the bottom bar is ASTM A372 grade K steel.
Metric UnitsUS Customary Units
Mechanical Properties
| Brinell Hardness | 150 to 180 | |
| 230 |
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 190 |
| Elongation at Break, % | 21 | |
| 23 |
| Fatigue Strength, MPa | 160 to 250 | |
| 440 |
| Poisson's Ratio | 0.29 | |
| 0.29 |
| Shear Modulus, GPa | 74 | |
| 73 |
| Shear Strength, MPa | 310 to 370 | |
| 490 |
| Tensile Strength: Ultimate (UTS), MPa | 500 to 590 | |
| 780 |
| Tensile Strength: Yield (Proof), MPa | 230 to 350 | |
| 620 |
Thermal Properties
| Latent Heat of Fusion, J/g | 260 | |
| 250 |
| Maximum Temperature: Mechanical, °C | 480 | |
| 440 |
| Melting Completion (Liquidus), °C | 1470 | |
| 1460 |
| Melting Onset (Solidus), °C | 1430 | |
| 1420 |
| Specific Heat Capacity, J/kg-K | 470 | |
| 470 |
| Thermal Conductivity, W/m-K | 41 | |
| 48 |
| Thermal Expansion, µm/m-K | 13 | |
| 13 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 7.6 | |
| 7.8 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 8.8 | |
| 8.9 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 4.1 | |
| 4.4 |
| Density, g/cm3 | 7.9 | |
| 7.9 |
| Embodied Carbon, kg CO2/kg material | 1.8 | |
| 1.8 |
| Embodied Energy, MJ/kg | 23 | |
| 24 |
| Embodied Water, L/kg | 62 | |
| 57 |
Common Calculations
| PREN (Pitting Resistance) | 6.4 | |
| 2.7 |
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 84 to 110 | |
| 160 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 140 to 320 | |
| 1010 |
| Stiffness to Weight: Axial, points | 13 | |
| 13 |
| Stiffness to Weight: Bending, points | 24 | |
| 24 |
| Strength to Weight: Axial, points | 18 to 21 | |
| 27 |
| Strength to Weight: Bending, points | 18 to 20 | |
| 24 |
| Thermal Diffusivity, mm2/s | 11 | |
| 13 |
| Thermal Shock Resistance, points | 14 to 17 | |
| 23 |
Alloy Composition
| Carbon (C), % | 0.050 to 0.15 | |
| 0 to 0.18 |
| Chromium (Cr), % | 2.8 to 3.3 | |
| 1.0 to 1.8 |
| Iron (Fe), % | 94.4 to 96 | |
| 93.4 to 96.6 |
| Manganese (Mn), % | 0.3 to 0.6 | |
| 0.1 to 0.4 |
| Molybdenum (Mo), % | 0.9 to 1.1 | |
| 0.2 to 0.6 |
| Nickel (Ni), % | 0 | |
| 2.0 to 3.3 |
| Phosphorus (P), % | 0 to 0.025 | |
| 0 to 0.015 |
| Silicon (Si), % | 0 to 0.5 | |
| 0.15 to 0.35 |
| Sulfur (S), % | 0 to 0.025 | |
| 0 to 0.010 |