Steel 1078 QT-45 vs 1078 QT-58
Steel · 1078 temper comparison
1078 QT-45 and 1078 QT-58 are two conditions of the same steel grade, 1078: QT-45 (Q&T 42-47 HRC) versus QT-58 (Q&T 56-62 HRC). The chemistry is identical, so every difference below comes from the condition. 1078 QT-58 is the stronger of the two: yield strength 1,700 MPa (247 ksi) against 1,280 MPa (186 ksi) for 1078 QT-45, about 33% more; tensile strength follows at 2,000 MPa (290 ksi) vs 1,450 MPa (210 ksi). In exchange, 1078 QT-45 is the more ductile: elongation 8% versus 2% for 1078 QT-58. 1078 QT-45 runs hotter in service (350°C vs 180°C continuous). On the shop floor, 1078 QT-45 machines more easily (poor vs not recommended) and 1078 QT-45 welds better (poor vs not recommended).
1078 QT-45Choose it when the part is bent, formed or impact-loaded, or when the part sees heat.
1078 QT-58Choose it when strength drives the design.
1078 QT-45 vs 1078 QT-58: 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)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
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 · Compressive Strength 400 MPa58 ksi · Shear Strength 415 MPa60.2 ksi · Hardness, Brinell 200 HB · Hardness, Rockwell B 93 HRB
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,400°C2,552 °F · Liquidus Temperature 1,475°C2,687 °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) 11.3 µm/m·K6.3 µin/in·°F · Latent Heat of Fusion 247 J/g106 BTU/lb · Min Service Temperature -20°C-4 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 9.5 % IACS · Electrical Resistivity 1.8×10⁻⁷ Ω·m7.09 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.61 V · Corrosion Resistance 8 / 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 60 / 100 · Polishability 65 / 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 60 L/kg7.2 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.
1078 QT-45 vs 1078 QT-58 — frequently asked
Is 1078 QT-58 stronger than 1078 QT-45?
Yes. 1078 QT-58 has a typical yield strength of 1,700 MPa (247 ksi) against 1,280 MPa (186 ksi) for 1078 QT-45 — about 33% more. Tensile strength is 2,000 MPa (290 ksi) vs 1,450 MPa (210 ksi).
Which condition does FabDigit quote by default, QT-45 or QT-58?
HR is the default 1078 condition in the FabDigit quote flow (neither QT-45 nor QT-58). 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, 1078 QT-45 or 1078 QT-58?
1078 QT-45. Its machinability rates poor (22/100) against not recommended (10/100) for 1078 QT-58; for welding the order is 1078 QT-45 first (poor, 20/100) then 1078 QT-58 (not recommended, 8/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 1078 QT-45 and 1078 QT-58 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.