Steel L7-HR vs L7 QT-50-52HRC
Steel · L7 temper comparison
L7-HR and L7 QT-50-52HRC are two conditions of the same steel grade, L7: HR (hot rolled) versus QT-50-52HRC (oil quenched and tempered to 50–52 HRC). The chemistry is identical, so every difference below comes from the condition. L7 QT-50-52HRC is the stronger of the two: yield strength 1,550 MPa (225 ksi) against 520 MPa (75.4 ksi) for L7-HR, about 198% more; tensile strength follows at 1,750 MPa (254 ksi) vs 950 MPa (138 ksi). In exchange, L7-HR is the more ductile: elongation 15% versus 6% for L7 QT-50-52HRC, and L7-HR is harder (260 HB vs 195 HB). L7 QT-50-52HRC runs hotter in service (330°C vs 200°C continuous). On the shop floor, L7-HR machines more easily (33 vs 15 out of 100).
L7-HRChoose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
L7 QT-50-52HRCChoose it when strength drives the design, or when the part sees heat.
L7-HR vs L7 QT-50-52HRC: 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
Shear Strength
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
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
Physical
Density and transition temperatures.
Same in both: Density 7.84 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.
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) 12 µm/m·K6.7 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -60°C-76 °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
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Same in both: Castability 20 / 100 · Brazeability / Solderability 45 / 100 · Polishability 70 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 33 MJ/kg14,187 BTU/lb · Embodied Carbon (primary production) 2.4 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.
L7-HR vs L7 QT-50-52HRC — frequently asked
Is L7 QT-50-52HRC stronger than L7-HR?
Yes. L7 QT-50-52HRC has a typical yield strength of 1,550 MPa (225 ksi) against 520 MPa (75.4 ksi) for L7-HR — about 198% more. Tensile strength is 1,750 MPa (254 ksi) vs 950 MPa (138 ksi).
Which condition does FabDigit quote by default, HR or QT-50-52HRC?
ANN is the default L7 condition in the FabDigit quote flow (neither HR nor QT-50-52HRC). 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, L7-HR or L7 QT-50-52HRC?
L7-HR, by a small margin. Both rate poor for machinability — 33/100 against 15/100 for L7 QT-50-52HRC; for welding the order is L7 QT-50-52HRC first (poor, 15/100) then L7-HR (not recommended, 10/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in L7-HR and L7 QT-50-52HRC 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.