Steel 8640-CD vs 8640 Q&T
Steel · 8640 temper comparison
8640-CD and 8640 Q&T are two conditions of the same steel grade, 8640: CD (cold drawn) versus Q&T (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. 8640 Q&T is the stronger of the two: yield strength 1,000 MPa (145 ksi) against 760 MPa (110 ksi) for 8640-CD, about 32% more; tensile strength follows at 1,100 MPa (160 ksi) vs 895 MPa (130 ksi). 8640 Q&T is the more ductile: elongation 17% versus 14% for 8640-CD, and 8640 Q&T is harder (331 HB vs 255 HB). 8640 Q&T runs hotter in service (450°C vs 300°C continuous). On the shop floor, 8640-CD machines more easily (good vs fair).
8640-CDChoose it when the part is machined in volume.
8640 Q&TChoose it when strength drives the design, or when the part is bent, formed or impact-loaded.
8640-CD vs 8640 Q&T: 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)
Elongation at Break
Reduction in Area
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell C
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 205 GPa29.7 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,425°C2,597 °F · Liquidus Temperature 1,500°C2,732 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 45 W/m·K26 BTU/hr·ft·°F · Specific Heat Capacity 475 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 12.2 µm/m·K6.8 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Min Service Temperature -40°C-40 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 7.8 % IACS · Electrical Resistivity 2.2×10⁻⁷ Ω·m8.66 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.65 V · Corrosion Resistance 14 / 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: Brazeability / Solderability 55 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 25 MJ/kg10,748 BTU/lb · Embodied Carbon (primary production) 1.9 kg CO₂/kg · Embodied Water 45 L/kg5.4 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.
8640-CD vs 8640 Q&T — frequently asked
Is 8640 Q&T stronger than 8640-CD?
Yes. 8640 Q&T has a typical yield strength of 1,000 MPa (145 ksi) against 760 MPa (110 ksi) for 8640-CD — about 32% more. Tensile strength is 1,100 MPa (160 ksi) vs 895 MPa (130 ksi).
Which condition does FabDigit quote by default, CD or Q&T?
HR is the default 8640 condition in the FabDigit quote flow (neither CD nor Q&T). 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 is easier to machine, 8640-CD or 8640 Q&T?
8640-CD. Its machinability rates good (60/100) against fair (42/100) for 8640 Q&T; for welding the order is 8640-CD first (fair, 35/100) then 8640 Q&T (poor, 30/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 8640-CD and 8640 Q&T 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.