Steel 1139-HR vs 1139 QT-34-38HRC
Steel · 1139 temper comparison
1139-HR and 1139 QT-34-38HRC are two conditions of the same steel grade, 1139: HR (hot rolled) versus QT-34-38HRC. The chemistry is identical, so every difference below comes from the condition. 1139 QT-34-38HRC is the stronger of the two: yield strength 930 MPa (135 ksi) against 345 MPa (50 ksi) for 1139-HR, about 170% more; tensile strength follows at 1,120 MPa (162 ksi) vs 620 MPa (89.9 ksi). In exchange, 1139-HR is the more ductile: elongation 16% versus 12% for 1139 QT-34-38HRC, and 1139 QT-34-38HRC is harder (341 HB vs 179 HB). 1139-HR conducts heat better (50 W/m·K vs 44 W/m·K). On the shop floor, 1139-HR machines more easily (good vs fair) and 1139-HR welds better (30 vs 15 out of 100).
1139-HRChoose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
1139 QT-34-38HRCChoose it when strength drives the design.
1139-HR vs 1139 QT-34-38HRC: 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
Shear Strength
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Same in both: Elastic (Young's) Modulus 200 GPa29 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 140 GPa20.3 Msi · Poisson's Ratio 0.29
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 1,495°C2,723 °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 470 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 11.7 µm/m·K6.5 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -20°C-4 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.62 V · Corrosion Resistance 10 / 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: Brazeability / Solderability 55 / 100 · Polishability 40 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 25 MJ/kg10,748 BTU/lb · Embodied Carbon (primary production) 1.9 kg CO₂/kg · Embodied Water 45 L/kg5.4 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.
1139-HR vs 1139 QT-34-38HRC — frequently asked
Is 1139 QT-34-38HRC stronger than 1139-HR?
Yes. 1139 QT-34-38HRC has a typical yield strength of 930 MPa (135 ksi) against 345 MPa (50 ksi) for 1139-HR — about 170% more. Tensile strength is 1,120 MPa (162 ksi) vs 620 MPa (89.9 ksi).
Which condition does FabDigit quote by default, HR or QT-34-38HRC?
CD is the default 1139 condition in the FabDigit quote flow (neither HR nor QT-34-38HRC). 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, 1139-HR or 1139 QT-34-38HRC?
1139-HR. Its machinability rates good (68/100) against fair (46/100) for 1139 QT-34-38HRC; for welding the order is 1139-HR first (poor, 30/100) then 1139 QT-34-38HRC (poor, 15/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 1139-HR and 1139 QT-34-38HRC 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.