Steel 1.2842-QT300 vs 1.2842-SR
Steel · 1.2842 temper comparison
1.2842-QT300 and 1.2842-SR are two conditions of the same steel grade, 1.2842: QT300 (Q&T 300 °C) versus SR (stress relieved). The chemistry is identical, so every difference below comes from the condition. 1.2842-QT300 is the stronger of the two: yield strength 1,620 MPa (235 ksi) against 420 MPa (60.9 ksi) for 1.2842-SR, about 3.9 times as much; tensile strength follows at 1,900 MPa (276 ksi) vs 700 MPa (102 ksi). In exchange, 1.2842-SR is the more ductile: elongation 16% versus 3% for 1.2842-QT300, and 1.2842-QT300 is harder (560 HB vs 215 HB). 1.2842-SR runs hotter in service (400°C vs 250°C continuous). On the shop floor, 1.2842-SR machines more easily (fair vs not recommended) and 1.2842-SR welds better (poor vs not recommended).
1.2842-QT300Choose it when strength drives the design.
1.2842-SRChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
1.2842-QT300 vs 1.2842-SR: 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.
Elastic (Young's) Modulus
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Reduction in Area
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell C
Hardness, Vickers
Same in both: Shear Modulus 81 GPa11.7 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Hardness, Rockwell B 95 HRB
Physical
Density and transition temperatures.
Same in both: Density 7.8 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) 12.5 µm/m·K6.9 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -30°C-22 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.6 V
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 40 / 100 · Polishability 65 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 34 MJ/kg14,617 BTU/lb · Embodied Carbon (primary production) 2.4 kg CO₂/kg · Embodied Water 65 L/kg7.8 gal/lb · Typical Recycled Content 35%
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.
1.2842-QT300 vs 1.2842-SR — frequently asked
Is 1.2842-QT300 stronger than 1.2842-SR?
Yes. 1.2842-QT300 has a typical yield strength of 1,620 MPa (235 ksi) against 420 MPa (60.9 ksi) for 1.2842-SR — about 3.9 times as much. Tensile strength is 1,900 MPa (276 ksi) vs 700 MPa (102 ksi).
Which condition does FabDigit quote by default, QT300 or SR?
Annealed is the default 1.2842 condition in the FabDigit quote flow (neither QT300 nor SR). 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, 1.2842-QT300 or 1.2842-SR?
1.2842-SR. Its machinability rates fair (45/100) against not recommended (12/100) for 1.2842-QT300; for welding the order is 1.2842-SR first (poor, 20/100) then 1.2842-QT300 (not recommended, 5/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 1.2842-QT300 and 1.2842-SR 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.