Steel SKH59 QT64-66 vs SKH59 QT68-70
Steel · SKH59 temper comparison
SKH59 QT64-66 and SKH59 QT68-70 are two conditions of the same steel grade, SKH59: QT64-66 (hardened & tempered, 64–66 HRC) versus QT68-70 (hardened & tempered, 68–70 HRC). The chemistry is identical, so every difference below comes from the condition. SKH59 QT68-70 is the stronger of the two: yield strength 2,000 MPa (290 ksi) against 600 MPa (87 ksi) for SKH59 QT64-66, about 3.3 times as much; tensile strength follows at 2,100 MPa (305 ksi) vs 900 MPa (131 ksi). SKH59 QT68-70 is harder — 69 HRC against 65 HRC for SKH59 QT64-66 — which matters for wear surfaces and threads. SKH59 QT64-66 conducts electricity better (2.9 % IACS vs 2.6 % IACS). On the shop floor, SKH59 QT64-66 welds better (poor vs not recommended).
SKH59 QT64-66Choose it when it will be welded.
SKH59 QT68-70Choose it when strength drives the design, or when surface hardness matters.
SKH59 QT64-66 vs SKH59 QT68-70: 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.
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Reduction in Area
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Rockwell C
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 230 GPa33.4 Msi · Shear Modulus 86 GPa12.5 Msi · Bulk Modulus 170 GPa24.7 Msi · Poisson's Ratio 0.28 · Elongation at Break 0% · Hardness, Brinell 255 HB · Hardness, Rockwell B 101 HRB
Physical
Density and transition temperatures.
Same in both: Density 7.98 g/cm³0.29 lb/in³ · Melting Point (Solidus) 1,290°C2,354 °F · Liquidus Temperature 1,430°C2,606 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Max Service Temperature (continuous)
Same in both: Specific Heat Capacity 420 J/kg·K0.1 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 10.6 µm/m·K5.9 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -50°C-58 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.6 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Same in both: Castability 25 / 100 · Brazeability / Solderability 60 / 100 · Polishability 80 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 55 MJ/kg23,646 BTU/lb · Embodied Carbon (primary production) 4.2 kg CO₂/kg · Embodied Water 120 L/kg14.4 gal/lb · Typical Recycled Content 25%
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.
SKH59 QT64-66 vs SKH59 QT68-70 — frequently asked
Is SKH59 QT68-70 stronger than SKH59 QT64-66?
Yes. SKH59 QT68-70 has a typical yield strength of 2,000 MPa (290 ksi) against 600 MPa (87 ksi) for SKH59 QT64-66 — about 3.3 times as much. Tensile strength is 2,100 MPa (305 ksi) vs 900 MPa (131 ksi).
Which condition does FabDigit quote by default, QT64-66 or QT68-70?
ANN is the default SKH59 condition in the FabDigit quote flow (neither QT64-66 nor QT68-70). 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.
Which welds better, SKH59 QT64-66 or SKH59 QT68-70?
SKH59 QT64-66. Its weldability rates poor (15/100) against not recommended (5/100) for SKH59 QT68-70.
Ready to make it?
Upload a CAD file and FabDigit prices the part in SKH59 QT64-66 and SKH59 QT68-70 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.