Steel SNC631-A vs SNC631-QT
Steel · SNC631 temper comparison
SNC631-A and SNC631-QT are two conditions of the same steel grade, SNC631: A (solution annealed) versus QT (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. SNC631-QT is the stronger of the two: yield strength 750 MPa (109 ksi) against 400 MPa (58 ksi) for SNC631-A, about 88% more; tensile strength follows at 900 MPa (131 ksi) vs 630 MPa (91.4 ksi). In exchange, SNC631-A is the more ductile: elongation 26% versus 20% for SNC631-QT, and SNC631-QT is harder (269 HB vs 190 HB). On the shop floor, SNC631-A welds better (45 vs 35 out of 100).
SNC631-AChoose it when the part is bent, formed or impact-loaded, or when it will be welded.
SNC631-QTChoose it when strength drives the design.
SNC631-A vs SNC631-QT: 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
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 760 MPa110 ksi · Shear Strength 560 MPa81.2 ksi · Fracture Toughness (K_IC) 95 MPa·√m86.5 ksi·√in · Hardness, Rockwell C 27 HRC · Hardness, Vickers 283 HV
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,425°C2,597 °F · Liquidus Temperature 1,495°C2,723 °F
Thermal
How each material carries heat and how hot it can run.
Same in both: Thermal Conductivity 38 W/m·K22 BTU/hr·ft·°F · Specific Heat Capacity 470 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 12 µm/m·K6.7 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Max Service Temperature (continuous) 400°C752 °F · Min Service Temperature -60°C-76 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 7.2 % IACS · Electrical Resistivity 2.4×10⁻⁷ Ω·m9.45 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.61 V · Corrosion Resistance 13 / 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: Castability 25 / 100 · Brazeability / Solderability 55 / 100 · Polishability 65 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 32 MJ/kg13,758 BTU/lb · Embodied Carbon (primary production) 2.4 kg CO₂/kg · Embodied Water 65 L/kg7.8 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.
SNC631-A vs SNC631-QT — frequently asked
Is SNC631-QT stronger than SNC631-A?
Yes. SNC631-QT has a typical yield strength of 750 MPa (109 ksi) against 400 MPa (58 ksi) for SNC631-A — about 88% more. Tensile strength is 900 MPa (131 ksi) vs 630 MPa (91.4 ksi).
Which condition does FabDigit quote by default, A or QT?
QT is the default SNC631 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, SNC631-A or SNC631-QT?
SNC631-A, by a small margin. Both rate good for machinability — 62/100 against 55/100 for SNC631-QT; for welding the order is SNC631-A first (fair, 45/100) then SNC631-QT (fair, 35/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in SNC631-A and SNC631-QT 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.