ASTM A372 Grade H Class 55 vs. ASTM A372 Grade H Class 65
Both ASTM A372 grade H class 55 and ASTM A372 grade H class 65 are variants of the same material. They share alloy composition and many physical properties, but develop different mechanical properties as a result of different processing.
For each property being compared, the top bar is ASTM A372 grade H class 55 and the bottom bar is ASTM A372 grade H class 65.
Metric UnitsUS Customary Units
Mechanical Properties
| Brinell Hardness | 200 | |
| 250 |
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 190 |
| Elongation at Break, % | 22 | |
| 21 |
| Fatigue Strength, MPa | 310 | |
| 360 |
| Poisson's Ratio | 0.29 | |
| 0.29 |
| Shear Modulus, GPa | 73 | |
| 73 |
| Shear Strength, MPa | 410 | |
| 510 |
| Tensile Strength: Ultimate (UTS), MPa | 650 | |
| 810 |
| Tensile Strength: Yield (Proof), MPa | 430 | |
| 510 |
Thermal Properties
| Latent Heat of Fusion, J/g | 250 | |
| 250 |
| Maximum Temperature: Mechanical, °C | 410 | |
| 410 |
| 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 | 45 | |
| 45 |
| Thermal Expansion, µm/m-K | 13 | |
| 13 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 7.2 | |
| 7.2 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 8.3 | |
| 8.3 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 2.3 | |
| 2.3 |
| Density, g/cm3 | 7.8 | |
| 7.8 |
| Embodied Carbon, kg CO2/kg material | 1.5 | |
| 1.5 |
| Embodied Energy, MJ/kg | 20 | |
| 20 |
| Embodied Water, L/kg | 49 | |
| 49 |
Common Calculations
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 130 | |
| 150 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 500 | |
| 700 |
| Stiffness to Weight: Axial, points | 13 | |
| 13 |
| Stiffness to Weight: Bending, points | 24 | |
| 24 |
| Strength to Weight: Axial, points | 23 | |
| 29 |
| Strength to Weight: Bending, points | 21 | |
| 25 |
| Thermal Diffusivity, mm2/s | 12 | |
| 12 |
| Thermal Shock Resistance, points | 19 | |
| 24 |
Alloy Composition
| Carbon (C), % | 0.3 to 0.4 | |
| 0.3 to 0.4 |
| Chromium (Cr), % | 0.4 to 0.65 | |
| 0.4 to 0.65 |
| Iron (Fe), % | 97.3 to 98.3 | |
| 97.3 to 98.3 |
| Manganese (Mn), % | 0.75 to 1.1 | |
| 0.75 to 1.1 |
| Molybdenum (Mo), % | 0.15 to 0.25 | |
| 0.15 to 0.25 |
| Phosphorus (P), % | 0 to 0.015 | |
| 0 to 0.015 |
| Silicon (Si), % | 0.15 to 0.35 | |
| 0.15 to 0.35 |
| Sulfur (S), % | 0 to 0.010 | |
| 0 to 0.010 |