Steel SKH51 QT 58-60 HRC vs SKH51 QT 64-66 HRC
Steel · SKH51 temper comparison
SKH51 QT 58-60 HRC and SKH51 QT 64-66 HRC are two conditions of the same steel grade, SKH51: QT 58-60 HRC (hardened & tempered to 58–60 HRC) versus QT 64-66 HRC (hardened & tempered to 64–66 HRC). The chemistry is identical, so every difference below comes from the condition. SKH51 QT 64-66 HRC is the stronger of the two: yield strength 2,000 MPa (290 ksi) against 550 MPa (79.8 ksi) for SKH51 QT 58-60 HRC, about 3.6 times as much. In exchange, SKH51 QT 58-60 HRC is the more ductile: elongation 1% versus 0.5% for SKH51 QT 64-66 HRC, and SKH51 QT 64-66 HRC is harder (65 HRC vs 59 HRC). SKH51 QT 64-66 HRC runs hotter in service (580°C vs 500°C continuous) and SKH51 QT 58-60 HRC conducts heat better (22 W/m·K vs 19 W/m·K). On the shop floor, SKH51 QT 58-60 HRC welds better (poor vs not recommended).
SKH51 QT 58-60 HRCChoose it when the part is bent, formed or impact-loaded, or when it will be welded.
SKH51 QT 64-66 HRCChoose it when strength drives the design, or when the part sees heat.
SKH51 QT 58-60 HRC vs SKH51 QT 64-66 HRC: 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.
SKH51 QT 58-60 HRCSKH51 QT 64-66 HRC
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
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: Shear Modulus 84 GPa12.2 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.28 · Hardness, Brinell 240 HB · Hardness, Rockwell B 99 HRB
Physical
Density and transition temperatures.
Same in both: Density 8.16 g/cm³0.29 lb/in³ · Melting Point (Solidus) 1,370°C2,498 °F · Liquidus Temperature 1,450°C2,642 °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) 11 µm/m·K6.1 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -60°C-76 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Corrosion Resistance 16 / 100
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 55 / 100 · Polishability 70 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 45 MJ/kg19,347 BTU/lb · Embodied Carbon (primary production) 3.2 kg CO₂/kg · Embodied Water 70 L/kg8.4 gal/lb · Typical Recycled Content 45%
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.
SKH51 QT 58-60 HRC vs SKH51 QT 64-66 HRC — frequently asked
Is SKH51 QT 64-66 HRC stronger than SKH51 QT 58-60 HRC?
Yes. SKH51 QT 64-66 HRC has a typical yield strength of 2,000 MPa (290 ksi) against 550 MPa (79.8 ksi) for SKH51 QT 58-60 HRC — about 3.6 times as much. Tensile strength is 2,200 MPa (319 ksi) vs 2,100 MPa (305 ksi).
Which condition does FabDigit quote by default, QT 58-60 HRC or QT 64-66 HRC?
Annealed is the default SKH51 condition in the FabDigit quote flow (neither QT 58-60 HRC nor QT 64-66 HRC). 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, SKH51 QT 58-60 HRC or SKH51 QT 64-66 HRC?
SKH51 QT 58-60 HRC. Its weldability rates poor (20/100) against not recommended (8/100) for SKH51 QT 64-66 HRC.
Ready to make it?
Upload a CAD file and FabDigit prices the part in SKH51 QT 58-60 HRC and SKH51 QT 64-66 HRC 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.