Steel 45B-CD vs 45B-QT550
Steel · 45B temper comparison
45B-CD and 45B-QT550 are two conditions of the same steel grade, 45B: CD (cold drawn) versus QT550 (Q&T). The chemistry is identical, so every difference below comes from the condition. 45B-QT550 is the stronger of the two: yield strength 740 MPa (107 ksi) against 620 MPa (89.9 ksi) for 45B-CD, about 19% more; tensile strength follows at 900 MPa (131 ksi) vs 780 MPa (113 ksi). 45B-QT550 is the more ductile: elongation 14% versus 10% for 45B-CD, and 45B-QT550 is harder (269 HB vs 235 HB). 45B-QT550 runs hotter in service (400°C vs 300°C continuous). On the shop floor, 45B-CD machines more easily (good vs fair).
45B-CDChoose it when the part is machined in volume.
45B-QT550Choose it when strength drives the design, or when the part is bent, formed or impact-loaded.
45B-CD vs 45B-QT550: 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)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
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
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.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 46 W/m·K26.6 BTU/hr·ft·°F · Specific Heat Capacity 470 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 11.6 µm/m·K6.4 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -20°C-4 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.61 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 %)
Weldability
Formability (cold)
Same in both: Brazeability / Solderability 55 / 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.
45B-CD vs 45B-QT550 — frequently asked
Is 45B-QT550 stronger than 45B-CD?
Yes. 45B-QT550 has a typical yield strength of 740 MPa (107 ksi) against 620 MPa (89.9 ksi) for 45B-CD — about 19% more. Tensile strength is 900 MPa (131 ksi) vs 780 MPa (113 ksi).
Which condition does FabDigit quote by default, CD or QT550?
HR is the default 45B condition in the FabDigit quote flow (neither CD nor QT550). 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, 45B-CD or 45B-QT550?
45B-CD. Its machinability rates good (62/100) against fair (45/100) for 45B-QT550; for welding the order is 45B-QT550 first (fair, 40/100) then 45B-CD (fair, 35/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 45B-CD and 45B-QT550 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.