Steel 1.2738 Prehard vs 1.2738 Q&T
Steel · 1.2738 temper comparison
1.2738 Prehard and 1.2738 Q&T are two conditions of the same steel grade, 1.2738: Prehard (pre-hardened) versus Q&T (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. 1.2738 Q&T is the stronger of the two: yield strength 1,200 MPa (174 ksi) against 860 MPa (125 ksi) for 1.2738 Prehard, about 40% more; tensile strength follows at 1,400 MPa (203 ksi) vs 1,000 MPa (145 ksi). In exchange, 1.2738 Prehard is the more ductile: elongation 14% versus 10% for 1.2738 Q&T, and 1.2738 Q&T is harder (400 HB vs 305 HB). 1.2738 Prehard runs hotter in service (400°C vs 350°C continuous). On the shop floor, 1.2738 Prehard machines more easily (good vs poor) and 1.2738 Prehard welds better (fair vs poor).
1.2738 PrehardChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
1.2738 Q&TChoose it when strength drives the design.
1.2738 Prehard vs 1.2738 Q&T: 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 205 GPa29.7 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Compressive Strength 880 MPa128 ksi · Shear Strength 620 MPa89.9 ksi · Fracture Toughness (K_IC) 90 MPa·√m81.9 ksi·√in
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.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 33 W/m·K19.1 BTU/hr·ft·°F · Specific Heat Capacity 460 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 12.4 µm/m·K6.9 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Min Service Temperature -20°C-4 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 7 % IACS · Electrical Resistivity 2.5×10⁻⁷ Ω·m9.84 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.6 V · Corrosion Resistance 12 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Same in both: Formability (cold) 30 / 100 · Brazeability / Solderability 40 / 100 · Polishability 78 / 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.
1.2738 Prehard vs 1.2738 Q&T — frequently asked
Is 1.2738 Q&T stronger than 1.2738 Prehard?
Yes. 1.2738 Q&T has a typical yield strength of 1,200 MPa (174 ksi) against 860 MPa (125 ksi) for 1.2738 Prehard — about 40% more. Tensile strength is 1,400 MPa (203 ksi) vs 1,000 MPa (145 ksi).
Which condition does FabDigit quote by default, Prehard or Q&T?
Annealed is the default 1.2738 condition in the FabDigit quote flow (neither Prehard nor Q&T). 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, 1.2738 Prehard or 1.2738 Q&T?
1.2738 Prehard. Its machinability rates good (55/100) against poor (30/100) for 1.2738 Q&T; for welding the order is 1.2738 Prehard first (fair, 50/100) then 1.2738 Q&T (poor, 25/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 1.2738 Prehard and 1.2738 Q&T 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.