Steel C45Pb-A vs C45Pb-QT
Steel · C45Pb temper comparison
C45Pb-A and C45Pb-QT are two conditions of the same steel grade, C45Pb: A (solution annealed) versus QT (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. C45Pb-QT is the stronger of the two: yield strength 550 MPa (79.8 ksi) against 320 MPa (46.4 ksi) for C45Pb-A, about 72% more; tensile strength follows at 760 MPa (110 ksi) vs 580 MPa (84.1 ksi). In exchange, C45Pb-A is the more ductile: elongation 20% versus 15% for C45Pb-QT, and C45Pb-QT is harder (225 HB vs 180 HB). On the shop floor, C45Pb-A machines more easily (very good vs good).
C45Pb-AChoose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
C45Pb-QTChoose it when strength drives the design.
C45Pb-A vs C45Pb-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
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Same in both: Elastic (Young's) Modulus 210 GPa30.5 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Reduction in Area 45% · Compressive Strength 550 MPa79.8 ksi · Shear Strength 430 MPa62.4 ksi · Hardness, Vickers 215 HV
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 1,490°C2,714 °F
Thermal
How each material carries heat and how hot it can run.
Same in both: Thermal Conductivity 48 W/m·K27.7 BTU/hr·ft·°F · Specific Heat Capacity 475 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 11.8 µm/m·K6.6 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Max Service Temperature (continuous) 300°C572 °F · Min Service Temperature -20°C-4 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 10.7 % IACS · Electrical Resistivity 1.6×10⁻⁷ Ω·m6.3 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.65 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 25 / 100 · Castability 45 / 100 · Brazeability / Solderability 40 / 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 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.
C45Pb-A vs C45Pb-QT — frequently asked
Is C45Pb-QT stronger than C45Pb-A?
Yes. C45Pb-QT has a typical yield strength of 550 MPa (79.8 ksi) against 320 MPa (46.4 ksi) for C45Pb-A — about 72% more. Tensile strength is 760 MPa (110 ksi) vs 580 MPa (84.1 ksi).
Which condition does FabDigit quote by default, A or QT?
CD is the default C45Pb condition in the FabDigit quote flow (neither A 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, C45Pb-A or C45Pb-QT?
C45Pb-A. Its machinability rates very good (72/100) against good (62/100) for C45Pb-QT.
Ready to make it?
Upload a CAD file and FabDigit prices the part in C45Pb-A and C45Pb-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.