Steel 718 Prehard vs 718 Q&T-40
Steel · 718 temper comparison
718 Prehard and 718 Q&T-40 are two conditions of the same steel grade, 718: Prehard (pre-hardened) versus Q&T-40 (Q&T 38–44 HRC). The chemistry is identical, so every difference below comes from the condition. 718 Q&T-40 is the stronger of the two: yield strength 1,150 MPa (167 ksi) against 880 MPa (128 ksi) for 718 Prehard, about 31% more; tensile strength follows at 1,350 MPa (196 ksi) vs 1,030 MPa (149 ksi). In exchange, 718 Prehard is the more ductile: elongation 14% versus 10% for 718 Q&T-40, and 718 Q&T-40 is harder (390 HB vs 310 HB). 718 Prehard runs hotter in service (400°C vs 350°C continuous). On the shop floor, 718 Prehard machines more easily (good vs fair) and 718 Prehard welds better (fair vs poor).
718 PrehardChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
718 Q&T-40Choose it when strength drives the design.
718 Prehard vs 718 Q&T-40: 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
Hardness, Rockwell C
Hardness, Vickers
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
Physical
Density and transition temperatures.
Same in both: Density 7.8 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 460 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 12.6 µm/m·K7 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -20°C-4 °F
Electrical
Conductivity and insulation.
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Corrosion Resistance 15 / 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 40 / 100 · Polishability 80 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 32 MJ/kg13,758 BTU/lb · Embodied Carbon (primary production) 2.3 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.
718 Prehard vs 718 Q&T-40 — frequently asked
Is 718 Q&T-40 stronger than 718 Prehard?
Yes. 718 Q&T-40 has a typical yield strength of 1,150 MPa (167 ksi) against 880 MPa (128 ksi) for 718 Prehard — about 31% more. Tensile strength is 1,350 MPa (196 ksi) vs 1,030 MPa (149 ksi).
Which condition does FabDigit quote by default, Prehard or Q&T-40?
Prehard is the default 718 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, 718 Prehard or 718 Q&T-40?
718 Prehard. Its machinability rates good (55/100) against fair (35/100) for 718 Q&T-40; for welding the order is 718 Prehard first (fair, 45/100) then 718 Q&T-40 (poor, 25/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 718 Prehard and 718 Q&T-40 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.