Steel L3 QT-55 vs L3 QT-59
Steel · L3 temper comparison
L3 QT-55 and L3 QT-59 are two conditions of the same steel grade, L3: QT-55 (hardened & tempered 315–370 °C) versus QT-59 (hardened & tempered 205–260 °C). The chemistry is identical, so every difference below comes from the condition. L3 QT-59 is the stronger of the two: yield strength 1,850 MPa (268 ksi) against 1,650 MPa (239 ksi) for L3 QT-55, about 12% more; tensile strength follows at 2,100 MPa (305 ksi) vs 1,900 MPa (276 ksi). In exchange, L3 QT-55 is the more ductile: elongation 4% versus 2% for L3 QT-59, and L3 QT-59 is harder (680 HV vs 600 HV). L3 QT-55 runs hotter in service (260°C vs 200°C continuous).
L3 QT-55Choose it when the part is bent, formed or impact-loaded, or when the part sees heat.
L3 QT-59Choose it when strength drives the design.
L3 QT-55 vs L3 QT-59: 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
Compressive Strength
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 207 GPa30 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Shear Strength 480 MPa69.6 ksi · Hardness, Brinell 197 HB · Hardness, Rockwell B 92 HRB
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 1,470°C2,678 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 38 W/m·K22 BTU/hr·ft·°F · Specific Heat Capacity 460 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 11.5 µm/m·K6.4 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -30°C-22 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 8 % IACS · Electrical Resistivity 2.2×10⁻⁷ Ω·m8.66 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.62 V · Corrosion Resistance 12 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Same in both: Machinability Rating (AISI 1212 = 100 %) 60% · Weldability 15 / 100 · Formability (cold) 35 / 100 · Castability 25 / 100 · Brazeability / Solderability 45 / 100 · Polishability 75 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 34 MJ/kg14,617 BTU/lb · Embodied Carbon (primary production) 2.5 kg CO₂/kg · Embodied Water 70 L/kg8.4 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.
L3 QT-55 vs L3 QT-59 — frequently asked
Is L3 QT-59 stronger than L3 QT-55?
Yes. L3 QT-59 has a typical yield strength of 1,850 MPa (268 ksi) against 1,650 MPa (239 ksi) for L3 QT-55 — about 12% more. Tensile strength is 2,100 MPa (305 ksi) vs 1,900 MPa (276 ksi).
Which condition does FabDigit quote by default, QT-55 or QT-59?
ANN is the default L3 condition in the FabDigit quote flow (neither QT-55 nor QT-59). 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.
When should I choose L3 QT-55 over L3 QT-59?
Pick L3 QT-55 when the part is bent, formed or impact-loaded, or when the part sees heat. Pick L3 QT-59 when strength drives the design.
Ready to make it?
Upload a CAD file and FabDigit prices the part in L3 QT-55 and L3 QT-59 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.