Steel SK3 Q&T 42-46 HRC vs SK3 Q&T 55-58 HRC
Steel · SK3 temper comparison
SK3 Q&T 42-46 HRC and SK3 Q&T 55-58 HRC are two conditions of the same steel grade, SK3: Q&T 42-46 HRC (tempered ~500 °C) versus Q&T 55-58 HRC (tempered ~300 °C). The chemistry is identical, so every difference below comes from the condition. SK3 Q&T 55-58 HRC is the stronger of the two: yield strength 1,650 MPa (239 ksi) against 1,250 MPa (181 ksi) for SK3 Q&T 42-46 HRC, about 32% more; tensile strength follows at 1,900 MPa (276 ksi) vs 1,400 MPa (203 ksi). In exchange, SK3 Q&T 42-46 HRC is the more ductile: elongation 9% versus 4% for SK3 Q&T 55-58 HRC, and SK3 Q&T 55-58 HRC is harder (590 HB vs 415 HB). SK3 Q&T 42-46 HRC runs hotter in service (400°C vs 250°C continuous). On the shop floor, SK3 Q&T 42-46 HRC machines more easily (poor vs not recommended).
SK3 Q&T 42-46 HRCChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
SK3 Q&T 55-58 HRCChoose it when strength drives the design.
SK3 Q&T 42-46 HRC vs SK3 Q&T 55-58 HRC: 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.
SK3 Q&T 42-46 HRCSK3 Q&T 55-58 HRC
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)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Vickers
Same in both: Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Hardness, Rockwell B 92 HRB
Physical
Density and transition temperatures.
Same in both: Density 7.83 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,400°C2,552 °F · Liquidus Temperature 1,460°C2,660 °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) 11.5 µm/m·K6.4 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) -0.6 V · Corrosion Resistance 9 / 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 50 / 100 · Polishability 70 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 27 MJ/kg11,608 BTU/lb · Embodied Carbon (primary production) 2.1 kg CO₂/kg · Embodied Water 60 L/kg7.2 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.
SK3 Q&T 42-46 HRC vs SK3 Q&T 55-58 HRC — frequently asked
Is SK3 Q&T 55-58 HRC stronger than SK3 Q&T 42-46 HRC?
Yes. SK3 Q&T 55-58 HRC has a typical yield strength of 1,650 MPa (239 ksi) against 1,250 MPa (181 ksi) for SK3 Q&T 42-46 HRC — about 32% more. Tensile strength is 1,900 MPa (276 ksi) vs 1,400 MPa (203 ksi).
Which condition does FabDigit quote by default, Q&T 42-46 HRC or Q&T 55-58 HRC?
Annealed is the default SK3 condition in the FabDigit quote flow (neither Q&T 42-46 HRC nor Q&T 55-58 HRC). 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, SK3 Q&T 42-46 HRC or SK3 Q&T 55-58 HRC?
SK3 Q&T 42-46 HRC. Its machinability rates poor (18/100) against not recommended (8/100) for SK3 Q&T 55-58 HRC.
Ready to make it?
Upload a CAD file and FabDigit prices the part in SK3 Q&T 42-46 HRC and SK3 Q&T 55-58 HRC 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.