Stainless Steel SUS440C-A vs SUS440C-QT300
Stainless Steel · SUS440C temper comparison
SUS440C-A and SUS440C-QT300 are two conditions of the same stainless steel grade, SUS440C: A (solution annealed) versus QT300 (hardened + tempered 260–320 °C). The chemistry is identical, so every difference below comes from the condition. SUS440C-QT300 is the stronger of the two: yield strength 1,740 MPa (252 ksi) against 450 MPa (65.3 ksi) for SUS440C-A, about 3.9 times as much; tensile strength follows at 1,860 MPa (270 ksi) vs 760 MPa (110 ksi). In exchange, SUS440C-A is the more ductile: elongation 14% versus 3% for SUS440C-QT300, and SUS440C-QT300 is harder (56 HRC vs 22 HRC). SUS440C-A runs hotter in service (600°C vs 300°C continuous). On the shop floor, SUS440C-A machines more easily (fair vs not recommended).
SUS440C-AChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
SUS440C-QT300Choose it when strength drives the design.
SUS440C-A vs SUS440C-QT300: 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
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
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 · Reduction in Area 25% · Shear Strength 460 MPa66.7 ksi · Hardness, Brinell 240 HB · 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.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 24.2 W/m·K14 BTU/hr·ft·°F · 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.
Same in both: Electrical Conductivity 2.9 % IACS · Electrical Resistivity 6×10⁻⁷ Ω·m23.6 µΩ·in
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
Same in both: Machinability Rating (AISI 1212 = 100 %) 40% · Weldability 15 / 100 · Formability (cold) 20 / 100 · 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-QT300 — frequently asked
Is SUS440C-QT300 stronger than SUS440C-A?
Yes. SUS440C-QT300 has a typical yield strength of 1,740 MPa (252 ksi) against 450 MPa (65.3 ksi) for SUS440C-A — about 3.9 times as much. Tensile strength is 1,860 MPa (270 ksi) vs 760 MPa (110 ksi).
Which condition does FabDigit quote by default, A or QT300?
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-QT300?
SUS440C-A. Its machinability rates fair (35/100) against not recommended (10/100) for SUS440C-QT300.
Ready to make it?
Upload a CAD file and FabDigit prices the part in SUS440C-A and SUS440C-QT300 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.