Steel 30MnB5 +QT vs 30MnB5 QT-40-45HRC
Steel · 30MnB5 temper comparison
30MnB5 +QT and 30MnB5 QT-40-45HRC are two conditions of the same steel grade, 30MnB5: +QT (quenched and tempered) versus QT-40-45HRC. The chemistry is identical, so every difference below comes from the condition. 30MnB5 QT-40-45HRC is the stronger of the two: yield strength 1,250 MPa (181 ksi) against 900 MPa (131 ksi) for 30MnB5 +QT, about 39% more; tensile strength follows at 1,400 MPa (203 ksi) vs 1,100 MPa (160 ksi). In exchange, 30MnB5 +QT is the more ductile: elongation 12% versus 9% for 30MnB5 QT-40-45HRC, and 30MnB5 QT-40-45HRC is harder (400 HB vs 330 HB). 30MnB5 +QT runs hotter in service (300°C vs 200°C continuous). On the shop floor, 30MnB5 +QT machines more easily (fair vs poor).
30MnB5 +QTChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
30MnB5 QT-40-45HRCChoose it when strength drives the design.
30MnB5 +QT vs 30MnB5 QT-40-45HRC: 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
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell C
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 · Compressive Strength 950 MPa138 ksi · Shear Strength 660 MPa95.7 ksi · Fracture Toughness (K_IC) 75 MPa·√m68.3 ksi·√in
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,425°C2,597 °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 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 -20°C-4 °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) -0.65 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 %)
Same in both: Weldability 30 / 100 · Formability (cold) 35 / 100 · Brazeability / Solderability 50 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 25 MJ/kg10,748 BTU/lb · Embodied Carbon (primary production) 2 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.
30MnB5 +QT vs 30MnB5 QT-40-45HRC — frequently asked
Is 30MnB5 QT-40-45HRC stronger than 30MnB5 +QT?
Yes. 30MnB5 QT-40-45HRC has a typical yield strength of 1,250 MPa (181 ksi) against 900 MPa (131 ksi) for 30MnB5 +QT — about 39% more. Tensile strength is 1,400 MPa (203 ksi) vs 1,100 MPa (160 ksi).
Which condition does FabDigit quote by default, +QT or QT-40-45HRC?
+QT is the default 30MnB5 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, 30MnB5 +QT or 30MnB5 QT-40-45HRC?
30MnB5 +QT. Its machinability rates fair (40/100) against poor (25/100) for 30MnB5 QT-40-45HRC.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 30MnB5 +QT and 30MnB5 QT-40-45HRC 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.