Steel 81B45-A vs 81B45 QT34-38
Steel · 81B45 temper comparison
81B45-A and 81B45 QT34-38 are two conditions of the same steel grade, 81B45: A (solution annealed) versus QT34-38 (Q&T 34–38 HRC). The chemistry is identical, so every difference below comes from the condition. 81B45 QT34-38 is the stronger of the two: yield strength 1,060 MPa (154 ksi) against 400 MPa (58 ksi) for 81B45-A, about 165% more; tensile strength follows at 1,170 MPa (170 ksi) vs 640 MPa (92.8 ksi). In exchange, 81B45-A is the more ductile: elongation 22% versus 15% for 81B45 QT34-38, and 81B45 QT34-38 is harder (341 HB vs 187 HB). On the shop floor, 81B45-A machines more easily (good vs fair).
81B45-AChoose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
81B45 QT34-38Choose it when strength drives the design.
81B45-A vs 81B45 QT34-38: 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
Shear Strength
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
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 · Reduction in Area 50% · Compressive Strength 400 MPa58 ksi · Fracture Toughness (K_IC) 80 MPa·√m72.8 ksi·√in · Hardness, Rockwell B 90 HRB
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,416°C2,581 °F · Liquidus Temperature 1,470°C2,678 °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 470 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 250 J/g107 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) -0.61 V · Corrosion Resistance 12 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Same in both: Weldability 45 / 100 · Formability (cold) 50 / 100 · Brazeability / Solderability 60 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 30 MJ/kg12,898 BTU/lb · Embodied Carbon (primary production) 2.1 kg CO₂/kg · Embodied Water 60 L/kg7.2 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.
81B45-A vs 81B45 QT34-38 — frequently asked
Is 81B45 QT34-38 stronger than 81B45-A?
Yes. 81B45 QT34-38 has a typical yield strength of 1,060 MPa (154 ksi) against 400 MPa (58 ksi) for 81B45-A — about 165% more. Tensile strength is 1,170 MPa (170 ksi) vs 640 MPa (92.8 ksi).
Which condition does FabDigit quote by default, A or QT34-38?
A is the default 81B45 condition in the FabDigit quote flow. 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, 81B45-A or 81B45 QT34-38?
81B45-A. Its machinability rates good (58/100) against fair (38/100) for 81B45 QT34-38.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 81B45-A and 81B45 QT34-38 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.