Hardened SAE-AISI A7 vs. Hardened SAE-AISI H21
Both hardened SAE-AISI A7 and hardened SAE-AISI H21 are iron alloys. Both are furnished in the hardened (H) condition. They have a moderately high 91% of their average alloy composition in common.
For each property being compared, the top bar is hardened SAE-AISI A7 and the bottom bar is hardened SAE-AISI H21.
Metric UnitsUS Customary Units
Mechanical Properties
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 200 |
| Poisson's Ratio | 0.29 | |
| 0.29 |
| Rockwell C Hardness | 66 | |
| 55 |
| Shear Modulus, GPa | 72 | |
| 76 |
| Tensile Strength: Ultimate (UTS), MPa | 2150 | |
| 1790 |
Thermal Properties
| Latent Heat of Fusion, J/g | 260 | |
| 250 |
| Melting Completion (Liquidus), °C | 1470 | |
| 1630 |
| Melting Onset (Solidus), °C | 1430 | |
| 1580 |
| Specific Heat Capacity, J/kg-K | 470 | |
| 440 |
| Thermal Conductivity, W/m-K | 37 | |
| 27 |
| Thermal Expansion, µm/m-K | 12 | |
| 11 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 10 | |
| 23 |
| Density, g/cm3 | 7.7 | |
| 8.5 |
| Embodied Carbon, kg CO2/kg material | 13 | |
| 4.5 |
| Embodied Energy, MJ/kg | 200 | |
| 68 |
| Embodied Water, L/kg | 100 | |
| 72 |
Common Calculations
| PREN (Pitting Resistance) | 11 | |
| 19 |
| Stiffness to Weight: Axial, points | 13 | |
| 13 |
| Stiffness to Weight: Bending, points | 25 | |
| 23 |
| Strength to Weight: Axial, points | 77 | |
| 58 |
| Strength to Weight: Bending, points | 48 | |
| 38 |
| Thermal Diffusivity, mm2/s | 10 | |
| 7.1 |
| Thermal Shock Resistance, points | 72 | |
| 59 |
Alloy Composition
| Carbon (C), % | 2.0 to 2.9 | |
| 0.28 to 0.36 |
| Chromium (Cr), % | 5.0 to 5.8 | |
| 3.0 to 3.8 |
| Copper (Cu), % | 0 to 0.25 | |
| 0 to 0.25 |
| Iron (Fe), % | 81.4 to 87.7 | |
| 87.6 to 93.8 |
| Manganese (Mn), % | 0 to 0.8 | |
| 0.15 to 0.4 |
| Molybdenum (Mo), % | 0.9 to 1.4 | |
| 0 |
| Nickel (Ni), % | 0 to 0.3 | |
| 0 to 0.3 |
| Phosphorus (P), % | 0 to 0.030 | |
| 0 to 0.030 |
| Silicon (Si), % | 0 to 0.5 | |
| 0.15 to 0.5 |
| Sulfur (S), % | 0 to 0.030 | |
| 0 to 0.030 |
| Tungsten (W), % | 0.5 to 1.5 | |
| 8.5 to 10 |
| Vanadium (V), % | 3.9 to 5.2 | |
| 0.3 to 0.6 |