Steel C40-CD vs C40 +QT
Steel · C40 temper comparison
C40-CD and C40 +QT are two conditions of the same steel grade, C40: CD (cold drawn) versus +QT (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. C40-CD is the stronger of the two: yield strength 530 MPa (76.9 ksi) against 500 MPa (72.5 ksi) for C40 +QT, about 6% more. In exchange, C40 +QT is the more ductile: elongation 18% versus 12% for C40-CD, and C40 +QT is harder (215 HB vs 180 HB). On the shop floor, C40-CD machines more easily (good vs fair).
C40-CDChoose it when strength drives the design, or when the part is machined in volume.
C40 +QTChoose it when the part is bent, formed or impact-loaded.
C40-CD vs C40 +QT: 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
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
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 · Compressive Strength 375 MPa54.4 ksi
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,420°C2,588 °F · Liquidus Temperature 1,495°C2,723 °F
Thermal
How each material carries heat and how hot it can run.
Same in both: Thermal Conductivity 50 W/m·K28.9 BTU/hr·ft·°F · Specific Heat Capacity 486 J/kg·K0.12 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 11.3 µm/m·K6.3 µin/in·°F · Latent Heat of Fusion 247 J/g106 BTU/lb · Max Service Temperature (continuous) 400°C752 °F · Min Service Temperature -20°C-4 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 10 % IACS · Electrical Resistivity 1.7×10⁻⁷ Ω·m6.69 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.62 V · Corrosion Resistance 10 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Formability (cold)
Same in both: Weldability 40 / 100 · Castability 45 / 100 · Brazeability / Solderability 65 / 100 · Polishability 55 / 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 40 L/kg4.8 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.
C40-CD vs C40 +QT — frequently asked
Is C40-CD stronger than C40 +QT?
Yes. C40-CD has a typical yield strength of 530 MPa (76.9 ksi) against 500 MPa (72.5 ksi) for C40 +QT — about 6% more. Tensile strength is 620 MPa (89.9 ksi) vs 720 MPa (104 ksi).
Which condition does FabDigit quote by default, CD or +QT?
+N is the default C40 condition in the FabDigit quote flow (neither CD nor +QT). 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, C40-CD or C40 +QT?
C40-CD. Its machinability rates good (60/100) against fair (48/100) for C40 +QT.
Ready to make it?
Upload a CAD file and FabDigit prices the part in C40-CD and C40 +QT 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.