Steel SKH57 QT62-64 vs SKH57 QT66-68
Steel · SKH57 temper comparison
SKH57 QT62-64 and SKH57 QT66-68 are two conditions of the same steel grade, SKH57: QT62-64 (hardened & tempered to 62–64 HRC) versus QT66-68 (hardened & tempered to 66–68 HRC). The chemistry is identical, so every difference below comes from the condition. Both yield at about 540 MPa — the mechanical properties are the same, and the difference is in how the stock is processed and what it is certified to (hardened & tempered to 62–64 HRC versus hardened & tempered to 66–68 HRC). SKH57 QT66-68 is harder — 67 HRC against 63 HRC for SKH57 QT62-64 — which matters for wear surfaces and threads. SKH57 QT66-68 runs hotter in service (600°C vs 550°C continuous).
SKH57 QT66-68Choose it when surface hardness matters, or when the part sees heat.
SKH57 QT62-64 vs SKH57 QT66-68: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all steel grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all steel grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Compressive Strength
Fracture Toughness (K_IC)
Hardness, Rockwell C
Hardness, Vickers
Same in both: Shear Modulus 86 GPa12.5 Msi · Bulk Modulus 165 GPa23.9 Msi · Poisson's Ratio 0.29 · Tensile Strength (Ultimate) 880 MPa128 ksi · Yield Strength (0.2% offset) 540 MPa78.3 ksi · Elongation at Break 10% · Hardness, Brinell 265 HB
Physical
Density and transition temperatures.
Same in both: Density 8.3 g/cm³0.3 lb/in³ · Melting Point (Solidus) 1,260°C2,300 °F · Liquidus Temperature 1,400°C2,552 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 19 W/m·K11 BTU/hr·ft·°F · Specific Heat Capacity 420 J/kg·K0.1 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 10.2 µm/m·K5.7 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -60°C-76 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 2.9 % IACS · Electrical Resistivity 6×10⁻⁷ Ω·m23.6 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.55 V · Corrosion Resistance 20 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Same in both: Weldability 12 / 100 · Formability (cold) 8 / 100 · Castability 20 / 100 · Brazeability / Solderability 55 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 60 MJ/kg25,795 BTU/lb · Embodied Carbon (primary production) 4.5 kg CO₂/kg · Embodied Water 90 L/kg10.8 gal/lb · Typical Recycled Content 35%
Strength versus weight
Yield strength against density for every steel grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
SKH57 QT62-64 vs SKH57 QT66-68 — frequently asked
What is the difference between SKH57 QT62-64 and SKH57 QT66-68?
SKH57 QT62-64 and SKH57 QT66-68 are two conditions of the same steel grade, SKH57: QT62-64 (hardened & tempered to 62–64 HRC) versus QT66-68 (hardened & tempered to 66–68 HRC). The chemistry is identical, so every difference below comes from the condition. Both yield at about 540 MPa — the mechanical properties are the same, and the difference is in how the stock is processed and what it is certified to (hardened & tempered to 62–64 HRC versus hardened & tempered to 66–68 HRC).
Which condition does FabDigit quote by default, QT62-64 or QT66-68?
ANN is the default SKH57 condition in the FabDigit quote flow (neither QT62-64 nor QT66-68). The other condition is available on request or by drawing note — specify it in the material field or the part notes and the quote is priced for it.
When should I choose SKH57 QT62-64 over SKH57 QT66-68?
Pick SKH57 QT66-68 when surface hardness matters, or when the part sees heat.
Ready to make it?
Upload a CAD file and FabDigit prices the part in SKH57 QT62-64 and SKH57 QT66-68 side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.