Steel SUM43-IH vs SUM43 QT-255HB
Steel · SUM43 temper comparison
SUM43-IH and SUM43 QT-255HB are two conditions of the same steel grade, SUM43: IH (induction hardened) versus QT-255HB (Q&T ~248–302 HB). The chemistry is identical, so every difference below comes from the condition. SUM43 QT-255HB is the stronger of the two: yield strength 750 MPa (109 ksi) against 640 MPa (92.8 ksi) for SUM43-IH, about 17% more; tensile strength follows at 900 MPa (131 ksi) vs 760 MPa (110 ksi). SUM43 QT-255HB is the more ductile: elongation 14% versus 10% for SUM43-IH, and SUM43-IH is harder (560 HB vs 262 HB). SUM43 QT-255HB runs hotter in service (400°C vs 200°C continuous) and SUM43 QT-255HB conducts electricity better (9.5 % IACS vs 8.5 % IACS). On the shop floor, SUM43 QT-255HB machines more easily (good vs poor) and SUM43 QT-255HB welds better (poor vs not recommended).
SUM43 QT-255HBChoose it when strength drives the design, or when the part is bent, formed or impact-loaded.
SUM43-IH vs SUM43 QT-255HB: 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)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
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 · Hardness, Rockwell B 95 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.
Thermal Conductivity
Max Service Temperature (continuous)
Same in both: Specific Heat Capacity 480 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 11.5 µm/m·K6.4 µin/in·°F · Latent Heat of Fusion 260 J/g112 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) -0.6 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 40 L/kg4.8 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.
SUM43-IH vs SUM43 QT-255HB — frequently asked
Is SUM43 QT-255HB stronger than SUM43-IH?
Yes. SUM43 QT-255HB has a typical yield strength of 750 MPa (109 ksi) against 640 MPa (92.8 ksi) for SUM43-IH — about 17% more. Tensile strength is 900 MPa (131 ksi) vs 760 MPa (110 ksi).
Which condition does FabDigit quote by default, IH or QT-255HB?
CD is the default SUM43 condition in the FabDigit quote flow (neither IH nor QT-255HB). 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, SUM43-IH or SUM43 QT-255HB?
SUM43 QT-255HB. Its machinability rates good (65/100) against poor (20/100) for SUM43-IH; for welding the order is SUM43 QT-255HB first (poor, 20/100) then SUM43-IH (not recommended, 10/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in SUM43-IH and SUM43 QT-255HB 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.