Stainless Steel SUS440C-A vs SUS440C-QT540
Stainless Steel · SUS440C temper comparison
SUS440C-A and SUS440C-QT540 are two conditions of the same stainless steel grade, SUS440C: A (solution annealed) versus QT540 (hardened + tempered 540–600 °C). The chemistry is identical, so every difference below comes from the condition. SUS440C-QT540 is the stronger of the two: yield strength 1,550 MPa (225 ksi) against 450 MPa (65.3 ksi) for SUS440C-A, about 3.4 times as much; tensile strength follows at 1,700 MPa (247 ksi) vs 760 MPa (110 ksi). In exchange, SUS440C-A is the more ductile: elongation 14% versus 5% for SUS440C-QT540, and SUS440C-QT540 is harder (512 HB vs 240 HB). SUS440C-A runs hotter in service (600°C vs 480°C continuous). On the shop floor, SUS440C-A machines more easily (fair vs not recommended) and SUS440C-A welds better (poor vs not recommended).
SUS440C-AChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
SUS440C-QT540Choose it when strength drives the design.
SUS440C-A vs SUS440C-QT540: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all stainless 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 stainless 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)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell C
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 200 GPa29 Msi · Shear Modulus 78 GPa11.3 Msi · Bulk Modulus 166 GPa24.1 Msi · Poisson's Ratio 0.28 · Hardness, Rockwell B 99 HRB
Physical
Density and transition temperatures.
Same in both: Density 7.68 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,370°C2,498 °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 460 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 10.2 µm/m·K5.7 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Min Service Temperature -70°C-94 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.25 V
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 85 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 53 MJ/kg22,786 BTU/lb · Embodied Carbon (primary production) 5 kg CO₂/kg · Embodied Water 220 L/kg26.4 gal/lb · Typical Recycled Content 45%
Strength versus weight
Yield strength against density for every stainless steel grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
SUS440C-A vs SUS440C-QT540 — frequently asked
Is SUS440C-QT540 stronger than SUS440C-A?
Yes. SUS440C-QT540 has a typical yield strength of 1,550 MPa (225 ksi) against 450 MPa (65.3 ksi) for SUS440C-A — about 3.4 times as much. Tensile strength is 1,700 MPa (247 ksi) vs 760 MPa (110 ksi).
Which condition does FabDigit quote by default, A or QT540?
A is the default SUS440C 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, SUS440C-A or SUS440C-QT540?
SUS440C-A. Its machinability rates fair (35/100) against not recommended (12/100) for SUS440C-QT540; for welding the order is SUS440C-A first (poor, 15/100) then SUS440C-QT540 (not recommended, 5/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in SUS440C-A and SUS440C-QT540 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.