Steel M62 QT64-66 vs M62 QT66-68
Steel · M62 temper comparison
M62 QT64-66 and M62 QT66-68 are two conditions of the same steel grade, M62: QT64-66 (Q&T 64–66 HRC) versus QT66-68 (Q&T 66–68 HRC). The chemistry is identical, so every difference below comes from the condition. M62 QT64-66 is the stronger of the two: tensile strength 2,300 MPa (334 ksi) against 2,100 MPa (305 ksi) for M62 QT66-68, about 10% more. M62 QT64-66 is the more ductile: elongation 0.5% versus 0.2% for M62 QT66-68, and M62 QT66-68 is harder (900 HV vs 830 HV).
M62 QT64-66Choose it when strength drives the design, or when the part is bent, formed or impact-loaded.
M62 QT64-66 vs M62 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
Tensile Strength (Ultimate)
Elongation at Break
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Hardness, Rockwell C
Hardness, Vickers
Same in both: Shear Modulus 85 GPa12.3 Msi · Bulk Modulus 168 GPa24.4 Msi · Poisson's Ratio 0.29 · Yield Strength (0.2% offset) 560 MPa81.2 ksi · Reduction in Area 20% · Hardness, Brinell 255 HB · Hardness, Rockwell B 102 HRB
Physical
Density and transition temperatures.
Same in both: Density 8.16 g/cm³0.29 lb/in³ · Melting Point (Solidus) 1,230°C2,246 °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) 10.8 µm/m·K6 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 3.1 % IACS · Electrical Resistivity 5.5×10⁻⁷ Ω·m21.7 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.45 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 %)
Weldability
Formability (cold)
Polishability
Same in both: Castability 25 / 100 · Brazeability / Solderability 55 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 78 MJ/kg33,534 BTU/lb · Embodied Carbon (primary production) 5.6 kg CO₂/kg · Embodied Water 90 L/kg10.8 gal/lb · Typical Recycled Content 30%
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.
M62 QT64-66 vs M62 QT66-68 — frequently asked
Is M62 QT64-66 stronger than M62 QT66-68?
Yes. M62 QT64-66 has a typical tensile strength of 2,300 MPa (334 ksi) against 2,100 MPa (305 ksi) for M62 QT66-68 — about 10% more.
Which condition does FabDigit quote by default, QT64-66 or QT66-68?
A is the default M62 condition in the FabDigit quote flow (neither QT64-66 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 M62 QT64-66 over M62 QT66-68?
Pick M62 QT64-66 when strength drives the design, or when the part is bent, formed or impact-loaded.
Ready to make it?
Upload a CAD file and FabDigit prices the part in M62 QT64-66 and M62 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.