Steel 40MnB-IH vs 40MnB-QT
Steel · 40MnB temper comparison
40MnB-IH and 40MnB-QT are two conditions of the same steel grade, 40MnB: IH (induction hardened) versus QT (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. Both yield at about 850 MPa — the mechanical properties are the same, and the difference is in how the stock is processed and what it is certified to (induction hardened versus quenched and tempered). 40MnB-IH is harder — 560 HB against 300 HB for 40MnB-QT — which matters for wear surfaces and threads. 40MnB-QT runs hotter in service (400°C vs 180°C continuous). On the shop floor, 40MnB-QT machines more easily (fair vs poor), 40MnB-QT welds better (poor vs not recommended), and 40MnB-QT forms better (fair vs not recommended).
40MnB-IHChoose it when surface hardness matters.
40MnB-QTChoose it when the part sees heat, or when the part is machined in volume.
40MnB-IH vs 40MnB-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.
Elongation at Break
Reduction in Area
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
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 · Tensile Strength (Ultimate) 1,030 MPa149 ksi · Yield Strength (0.2% offset) 850 MPa123 ksi
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.
Thermal Conductivity
Max Service Temperature (continuous)
Same in both: 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 -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) -0.62 V · Corrosion Resistance 11 / 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 62 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 26 MJ/kg11,178 BTU/lb · Embodied Carbon (primary production) 2 kg CO₂/kg · Embodied Water 40 L/kg4.8 gal/lb · Typical Recycled Content 25%
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.
40MnB-IH vs 40MnB-QT — frequently asked
What is the difference between 40MnB-IH and 40MnB-QT?
40MnB-IH and 40MnB-QT are two conditions of the same steel grade, 40MnB: IH (induction hardened) versus QT (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. Both yield at about 850 MPa — the mechanical properties are the same, and the difference is in how the stock is processed and what it is certified to (induction hardened versus quenched and tempered).
Which condition does FabDigit quote by default, IH or QT?
QT is the default 40MnB 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, 40MnB-IH or 40MnB-QT?
40MnB-QT. Its machinability rates fair (52/100) against poor (15/100) for 40MnB-IH; for welding the order is 40MnB-QT first (poor, 32/100) then 40MnB-IH (not recommended, 8/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 40MnB-IH and 40MnB-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.