Stainless Steel 415-QT780 vs 415-QT900
Stainless Steel · 415 temper comparison
415-QT780 and 415-QT900 are two conditions of the same stainless steel grade, 415: QT780 (quenched and double tempered, Rm 780–980 MPa) versus QT900 (quenched and tempered, Rm 900–1100 MPa). The chemistry is identical, so every difference below comes from the condition. 415-QT900 is the stronger of the two: yield strength 870 MPa (126 ksi) against 700 MPa (102 ksi) for 415-QT780, about 24% more; tensile strength follows at 980 MPa (142 ksi) vs 850 MPa (123 ksi). In exchange, 415-QT780 is the more ductile: elongation 18% versus 15% for 415-QT900, and 415-QT900 is harder (300 HB vs 260 HB). 415-QT780 runs hotter in service (450°C vs 400°C continuous).
415-QT780Choose it when the part is bent, formed or impact-loaded, or when the part sees heat.
415-QT900Choose it when strength drives the design.
415-QT780 vs 415-QT900: 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
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 200 GPa29 Msi · Shear Modulus 77 GPa11.2 Msi · Bulk Modulus 165 GPa23.9 Msi · Poisson's Ratio 0.3 · Compressive Strength 700 MPa102 ksi · Shear Strength 520 MPa75.4 ksi
Physical
Density and transition temperatures.
Same in both: Density 7.7 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,400°C2,552 °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 25 W/m·K14.4 BTU/hr·ft·°F · Specific Heat Capacity 430 J/kg·K0.1 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 10.5 µm/m·K5.8 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Min Service Temperature -100°C-148 °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).
Same in both: Galvanic Potential (seawater, vs SCE) -0.3 V · Corrosion Resistance 48 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Formability (cold)
Same in both: Weldability 72 / 100 · Castability 70 / 100 · Brazeability / Solderability 40 / 100 · Polishability 65 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 53 MJ/kg22,786 BTU/lb · Embodied Carbon (primary production) 4.5 kg CO₂/kg · Embodied Water 140 L/kg16.8 gal/lb · Typical Recycled Content 50%
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.
415-QT780 vs 415-QT900 — frequently asked
Is 415-QT900 stronger than 415-QT780?
Yes. 415-QT900 has a typical yield strength of 870 MPa (126 ksi) against 700 MPa (102 ksi) for 415-QT780 — about 24% more. Tensile strength is 980 MPa (142 ksi) vs 850 MPa (123 ksi).
Which condition does FabDigit quote by default, QT780 or QT900?
QT780 is the default 415 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, 415-QT780 or 415-QT900?
415-QT780. Its machinability rates fair (40/100) against poor (32/100) for 415-QT900.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 415-QT780 and 415-QT900 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.