Steel A231 QT-425 vs A231 QT-650
Steel · A231 temper comparison
A231 QT-425 and A231 QT-650 are two conditions of the same steel grade, A231: QT-425 (Q&T) versus QT-650 (Q&T). The chemistry is identical, so every difference below comes from the condition. A231 QT-425 is the stronger of the two: yield strength 1,430 MPa (207 ksi) against 940 MPa (136 ksi) for A231 QT-650, about 52% more; tensile strength follows at 1,550 MPa (225 ksi) vs 1,000 MPa (145 ksi). In exchange, A231 QT-650 is the more ductile: elongation 17% versus 10% for A231 QT-425, and A231 QT-425 is harder (418 HB vs 293 HB). A231 QT-650 runs hotter in service (400°C vs 320°C continuous). On the shop floor, A231 QT-650 machines more easily (fair vs poor).
A231 QT-425Choose it when strength drives the design.
A231 QT-650Choose it when the part is bent, formed or impact-loaded, or when the part sees heat.
A231 QT-425 vs A231 QT-650: 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
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 207 GPa30 Msi · Shear Modulus 79.3 GPa11.5 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29
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 475 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 12.2 µm/m·K6.8 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -40°C-40 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 7.5 % IACS · Electrical Resistivity 2.3×10⁻⁷ Ω·m9.06 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.6 V · Corrosion Resistance 14 / 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 35 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 34 MJ/kg14,617 BTU/lb · Embodied Carbon (primary production) 2.3 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.
A231 QT-425 vs A231 QT-650 — frequently asked
Is A231 QT-425 stronger than A231 QT-650?
Yes. A231 QT-425 has a typical yield strength of 1,430 MPa (207 ksi) against 940 MPa (136 ksi) for A231 QT-650 — about 52% more. Tensile strength is 1,550 MPa (225 ksi) vs 1,000 MPa (145 ksi).
Which condition does FabDigit quote by default, QT-425 or QT-650?
OT is the default A231 condition in the FabDigit quote flow (neither QT-425 nor QT-650). 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, A231 QT-425 or A231 QT-650?
A231 QT-650. Its machinability rates fair (40/100) against poor (22/100) for A231 QT-425.
Ready to make it?
Upload a CAD file and FabDigit prices the part in A231 QT-425 and A231 QT-650 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.