ASTM A387 Grade 91 Class 2 vs. ASTM A369 Grade FP91
Both ASTM A387 grade 91 class 2 and ASTM A369 grade FP91 are iron alloys. Both are furnished in the normalized and tempered condition. Their average alloy composition is basically identical.
For each property being compared, the top bar is ASTM A387 grade 91 class 2 and the bottom bar is ASTM A369 grade FP91.
Metric UnitsUS Customary Units
Mechanical Properties
| Brinell Hardness | 200 | |
| 200 |
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 190 |
| Elongation at Break, % | 20 | |
| 19 |
| Fatigue Strength, MPa | 330 | |
| 320 |
| Poisson's Ratio | 0.28 | |
| 0.28 |
| Shear Modulus, GPa | 75 | |
| 75 |
| Shear Strength, MPa | 420 | |
| 410 |
| Tensile Strength: Ultimate (UTS), MPa | 670 | |
| 670 |
| Tensile Strength: Yield (Proof), MPa | 470 | |
| 460 |
Thermal Properties
| Latent Heat of Fusion, J/g | 270 | |
| 270 |
| Maximum Temperature: Mechanical, °C | 600 | |
| 600 |
| Melting Completion (Liquidus), °C | 1460 | |
| 1460 |
| Melting Onset (Solidus), °C | 1420 | |
| 1420 |
| Specific Heat Capacity, J/kg-K | 470 | |
| 470 |
| Thermal Conductivity, W/m-K | 26 | |
| 26 |
| Thermal Expansion, µm/m-K | 13 | |
| 13 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 8.9 | |
| 8.9 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 10 | |
| 10 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 7.0 | |
| 7.0 |
| Density, g/cm3 | 7.8 | |
| 7.8 |
| Embodied Carbon, kg CO2/kg material | 2.6 | |
| 2.6 |
| Embodied Energy, MJ/kg | 37 | |
| 37 |
| Embodied Water, L/kg | 88 | |
| 88 |
Common Calculations
| PREN (Pitting Resistance) | 13 | |
| 13 |
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 120 | |
| 110 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 580 | |
| 560 |
| Stiffness to Weight: Axial, points | 14 | |
| 14 |
| Stiffness to Weight: Bending, points | 25 | |
| 25 |
| Strength to Weight: Axial, points | 24 | |
| 24 |
| Strength to Weight: Bending, points | 22 | |
| 22 |
| Thermal Diffusivity, mm2/s | 6.9 | |
| 6.9 |
| Thermal Shock Resistance, points | 19 | |
| 18 |
Alloy Composition
| Aluminum (Al), % | 0 to 0.020 | |
| 0 to 0.020 |
| Carbon (C), % | 0.080 to 0.12 | |
| 0.080 to 0.12 |
| Chromium (Cr), % | 8.0 to 9.5 | |
| 8.0 to 9.5 |
| Iron (Fe), % | 87.3 to 90.3 | |
| 87.3 to 90.3 |
| Manganese (Mn), % | 0.3 to 0.6 | |
| 0.3 to 0.6 |
| Molybdenum (Mo), % | 0.85 to 1.1 | |
| 0.85 to 1.1 |
| Nickel (Ni), % | 0 to 0.4 | |
| 0 to 0.4 |
| Niobium (Nb), % | 0.060 to 0.1 | |
| 0.060 to 0.1 |
| Nitrogen (N), % | 0.030 to 0.070 | |
| 0.030 to 0.070 |
| Phosphorus (P), % | 0 to 0.020 | |
| 0 to 0.025 |
| Silicon (Si), % | 0.2 to 0.5 | |
| 0.2 to 0.5 |
| Sulfur (S), % | 0 to 0.010 | |
| 0 to 0.025 |
| Titanium (Ti), % | 0 to 0.010 | |
| 0 to 0.010 |
| Vanadium (V), % | 0.18 to 0.25 | |
| 0.18 to 0.25 |
| Zirconium (Zr), % | 0 to 0.010 | |
| 0 to 0.010 |