ASTM A387 Grade 21 Steel vs. ASTM A387 Grade 91 Class 2
Both ASTM A387 grade 21 steel and ASTM A387 grade 91 class 2 are iron alloys. They have a moderately high 94% 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 A387 grade 91 class 2.
Metric UnitsUS Customary Units
Mechanical Properties
| Brinell Hardness | 150 to 180 | |
| 200 |
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 190 |
| Elongation at Break, % | 21 | |
| 20 |
| Fatigue Strength, MPa | 160 to 250 | |
| 330 |
| Poisson's Ratio | 0.29 | |
| 0.28 |
| Shear Modulus, GPa | 74 | |
| 75 |
| Shear Strength, MPa | 310 to 370 | |
| 420 |
| Tensile Strength: Ultimate (UTS), MPa | 500 to 590 | |
| 670 |
| Tensile Strength: Yield (Proof), MPa | 230 to 350 | |
| 470 |
Thermal Properties
| Latent Heat of Fusion, J/g | 260 | |
| 270 |
| Maximum Temperature: Mechanical, °C | 480 | |
| 600 |
| 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 | |
| 26 |
| Thermal Expansion, µm/m-K | 13 | |
| 13 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 7.6 | |
| 8.9 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 8.8 | |
| 10 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 4.1 | |
| 7.0 |
| Density, g/cm3 | 7.9 | |
| 7.8 |
| Embodied Carbon, kg CO2/kg material | 1.8 | |
| 2.6 |
| Embodied Energy, MJ/kg | 23 | |
| 37 |
| Embodied Water, L/kg | 62 | |
| 88 |
Common Calculations
| PREN (Pitting Resistance) | 6.4 | |
| 13 |
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 84 to 110 | |
| 120 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 140 to 320 | |
| 580 |
| Stiffness to Weight: Axial, points | 13 | |
| 14 |
| Stiffness to Weight: Bending, points | 24 | |
| 25 |
| Strength to Weight: Axial, points | 18 to 21 | |
| 24 |
| Strength to Weight: Bending, points | 18 to 20 | |
| 22 |
| Thermal Diffusivity, mm2/s | 11 | |
| 6.9 |
| Thermal Shock Resistance, points | 14 to 17 | |
| 19 |
Alloy Composition
| Aluminum (Al), % | 0 | |
| 0 to 0.020 |
| Carbon (C), % | 0.050 to 0.15 | |
| 0.080 to 0.12 |
| Chromium (Cr), % | 2.8 to 3.3 | |
| 8.0 to 9.5 |
| Iron (Fe), % | 94.4 to 96 | |
| 87.3 to 90.3 |
| Manganese (Mn), % | 0.3 to 0.6 | |
| 0.3 to 0.6 |
| Molybdenum (Mo), % | 0.9 to 1.1 | |
| 0.85 to 1.1 |
| Nickel (Ni), % | 0 | |
| 0 to 0.4 |
| Niobium (Nb), % | 0 | |
| 0.060 to 0.1 |
| Nitrogen (N), % | 0 | |
| 0.030 to 0.070 |
| Phosphorus (P), % | 0 to 0.025 | |
| 0 to 0.020 |
| Silicon (Si), % | 0 to 0.5 | |
| 0.2 to 0.5 |
| Sulfur (S), % | 0 to 0.025 | |
| 0 to 0.010 |
| Titanium (Ti), % | 0 | |
| 0 to 0.010 |
| Vanadium (V), % | 0 | |
| 0.18 to 0.25 |
| Zirconium (Zr), % | 0 | |
| 0 to 0.010 |