Steel T7-A vs T7-QT57
Steel · T7 temper comparison
T7-A and T7-QT57 are two conditions of the same steel grade, T7: A (solution annealed) versus QT57 (water quenched + 200–250 °C temper). The chemistry is identical, so every difference below comes from the condition. T7-QT57 is the stronger of the two: yield strength 1,650 MPa (239 ksi) against 400 MPa (58 ksi) for T7-A, about 4.1 times as much; tensile strength follows at 1,950 MPa (283 ksi) vs 660 MPa (95.7 ksi). In exchange, T7-A is the more ductile: elongation 22% versus 2% for T7-QT57, and T7-QT57 is harder (615 HB vs 183 HB). T7-A runs hotter in service (250°C vs 200°C continuous) and T7-A conducts heat better (48 W/m·K vs 42 W/m·K). On the shop floor, T7-A machines more easily (good vs not recommended) and T7-A welds better (poor vs not recommended).
T7-AChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
T7-QT57Choose it when strength drives the design.
T7-A vs T7-QT57: 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.
Elastic (Young's) Modulus
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Reduction in Area
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Vickers
Same in both: Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Hardness, Rockwell B 90 HRB
Physical
Density and transition temperatures.
Same in both: Density 7.83 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,420°C2,588 °F · Liquidus Temperature 1,480°C2,696 °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) 11.6 µm/m·K6.4 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) -0.6 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 70 / 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 45 L/kg5.4 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.
T7-A vs T7-QT57 — frequently asked
Is T7-QT57 stronger than T7-A?
Yes. T7-QT57 has a typical yield strength of 1,650 MPa (239 ksi) against 400 MPa (58 ksi) for T7-A — about 4.1 times as much. Tensile strength is 1,950 MPa (283 ksi) vs 660 MPa (95.7 ksi).
Which condition does FabDigit quote by default, A or QT57?
A is the default T7 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, T7-A or T7-QT57?
T7-A. Its machinability rates good (60/100) against not recommended (10/100) for T7-QT57; for welding the order is T7-A first (poor, 15/100) then T7-QT57 (not recommended, 5/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in T7-A and T7-QT57 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.