Hardened SAE-AISI M3 Class 2 vs. Hardened SAE-AISI M4
Both hardened SAE-AISI M3 class 2 and hardened SAE-AISI M4 are iron alloys. Both are furnished in the hardened (H) condition. Their average alloy composition is basically identical.
For each property being compared, the top bar is hardened SAE-AISI M3 class 2 and the bottom bar is hardened SAE-AISI M4.
Metric UnitsUS Customary Units
Mechanical Properties
| Elastic (Young's, Tensile) Modulus, GPa | 200 | |
| 200 |
| Poisson's Ratio | 0.29 | |
| 0.29 |
| Rockwell C Hardness | 68 | |
| 66 |
| Shear Modulus, GPa | 77 | |
| 76 |
| Tensile Strength: Ultimate (UTS), MPa | 2210 | |
| 2150 |
Thermal Properties
| Latent Heat of Fusion, J/g | 260 | |
| 260 |
| Melting Completion (Liquidus), °C | 1620 | |
| 1610 |
| Melting Onset (Solidus), °C | 1570 | |
| 1560 |
| Specific Heat Capacity, J/kg-K | 440 | |
| 440 |
| Thermal Conductivity, W/m-K | 26 | |
| 25 |
| Thermal Expansion, µm/m-K | 12 | |
| 12 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 25 | |
| 25 |
| Density, g/cm3 | 8.3 | |
| 8.3 |
| Embodied Carbon, kg CO2/kg material | 12 | |
| 14 |
| Embodied Energy, MJ/kg | 180 | |
| 210 |
| Embodied Water, L/kg | 110 | |
| 110 |
Common Calculations
| PREN (Pitting Resistance) | 33 | |
| 30 |
| Stiffness to Weight: Axial, points | 13 | |
| 13 |
| Stiffness to Weight: Bending, points | 23 | |
| 23 |
| Strength to Weight: Axial, points | 74 | |
| 72 |
| Strength to Weight: Bending, points | 45 | |
| 45 |
| Thermal Diffusivity, mm2/s | 7.2 | |
| 6.9 |
| Thermal Shock Resistance, points | 69 | |
| 68 |
Alloy Composition
| Carbon (C), % | 1.2 to 1.3 | |
| 1.3 to 1.4 |
| Chromium (Cr), % | 3.8 to 4.5 | |
| 3.8 to 4.8 |
| Copper (Cu), % | 0 to 0.25 | |
| 0 to 0.25 |
| Iron (Fe), % | 75.8 to 82.3 | |
| 75.9 to 81.4 |
| Manganese (Mn), % | 0.15 to 0.4 | |
| 0.15 to 0.4 |
| Molybdenum (Mo), % | 4.8 to 6.5 | |
| 4.3 to 5.5 |
| Nickel (Ni), % | 0 to 0.3 | |
| 0 to 0.3 |
| Phosphorus (P), % | 0 to 0.030 | |
| 0 to 0.030 |
| Silicon (Si), % | 0.2 to 0.45 | |
| 0.2 to 0.45 |
| Sulfur (S), % | 0 to 0.030 | |
| 0 to 0.030 |
| Tungsten (W), % | 5.0 to 6.8 | |
| 5.3 to 6.5 |
| Vanadium (V), % | 2.8 to 3.8 | |
| 3.8 to 4.5 |