Steel 36MnB4 +QT vs 36MnB4 QT-12.9
Steel · 36MnB4 temper comparison
36MnB4 +QT and 36MnB4 QT-12.9 are two conditions of the same steel grade, 36MnB4: +QT (quenched and tempered) versus QT-12.9 (Q&T to property class 12.9). The chemistry is identical, so every difference below comes from the condition. 36MnB4 QT-12.9 is the stronger of the two: yield strength 1,140 MPa (165 ksi) against 980 MPa (142 ksi) for 36MnB4 +QT, about 16% more; tensile strength follows at 1,280 MPa (186 ksi) vs 1,200 MPa (174 ksi). In exchange, 36MnB4 +QT is the more ductile: elongation 11% versus 9% for 36MnB4 QT-12.9, and 36MnB4 QT-12.9 is harder (385 HB vs 355 HB). 36MnB4 +QT runs hotter in service (350°C vs 300°C continuous).
36MnB4 +QTChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
36MnB4 QT-12.9Choose it when strength drives the design.
36MnB4 +QT vs 36MnB4 QT-12.9: 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, 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 · Hardness, Rockwell B 91 HRB
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.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 44 W/m·K25.4 BTU/hr·ft·°F · Specific Heat Capacity 470 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 12.3 µm/m·K6.8 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -30°C-22 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 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) -0.62 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 %)
Weldability
Formability (cold)
Same in both: Brazeability / Solderability 45 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 24 MJ/kg10,318 BTU/lb · Embodied Carbon (primary production) 1.9 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.
36MnB4 +QT vs 36MnB4 QT-12.9 — frequently asked
Is 36MnB4 QT-12.9 stronger than 36MnB4 +QT?
Yes. 36MnB4 QT-12.9 has a typical yield strength of 1,140 MPa (165 ksi) against 980 MPa (142 ksi) for 36MnB4 +QT — about 16% more. Tensile strength is 1,280 MPa (186 ksi) vs 1,200 MPa (174 ksi).
Which condition does FabDigit quote by default, +QT or QT-12.9?
+AC+C is the default 36MnB4 condition in the FabDigit quote flow (neither +QT nor QT-12.9). 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, 36MnB4 +QT or 36MnB4 QT-12.9?
36MnB4 +QT. Its machinability rates fair (38/100) against poor (30/100) for 36MnB4 QT-12.9; for welding the order is 36MnB4 +QT first (poor, 20/100) then 36MnB4 QT-12.9 (poor, 15/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 36MnB4 +QT and 36MnB4 QT-12.9 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.