Steel SCr420-CH vs SCr420-QT
Steel · SCr420 temper comparison
SCr420-CH and SCr420-QT are two conditions of the same steel grade, SCr420: CH (carburized and hardened) versus QT (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. SCr420-CH is the stronger of the two: yield strength 850 MPa (123 ksi) against 700 MPa (102 ksi) for SCr420-QT, about 21% more; tensile strength follows at 1,100 MPa (160 ksi) vs 900 MPa (131 ksi). In exchange, SCr420-QT is the more ductile: elongation 17% versus 11% for SCr420-CH, and SCr420-QT is harder (275 HB vs 170 HB). SCr420-QT runs hotter in service (350°C vs 180°C continuous). On the shop floor, SCr420-QT machines more easily (fair vs not recommended) and SCr420-QT welds better (good vs not recommended).
SCr420-CHChoose it when strength drives the design.
SCr420-QTChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
SCr420-CH vs SCr420-QT: 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
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 · Hardness, Rockwell B 87 HRB
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,425°C2,597 °F · Liquidus Temperature 1,500°C2,732 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 44 W/m·K25.4 BTU/hr·ft·°F · Specific Heat Capacity 470 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 12.2 µm/m·K6.8 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -40°C-40 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 7.8 % 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) -0.61 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
Same in both: Formability (cold) 62 / 100 · Castability 30 / 100 · Brazeability / Solderability 55 / 100 · Polishability 60 / 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 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.
SCr420-CH vs SCr420-QT — frequently asked
Is SCr420-CH stronger than SCr420-QT?
Yes. SCr420-CH has a typical yield strength of 850 MPa (123 ksi) against 700 MPa (102 ksi) for SCr420-QT — about 21% more. Tensile strength is 1,100 MPa (160 ksi) vs 900 MPa (131 ksi).
Which condition does FabDigit quote by default, CH or QT?
A is the default SCr420 condition in the FabDigit quote flow (neither CH nor QT). 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, SCr420-CH or SCr420-QT?
SCr420-QT. Its machinability rates fair (44/100) against not recommended (10/100) for SCr420-CH; for welding the order is SCr420-QT first (good, 55/100) then SCr420-CH (not recommended, 10/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in SCr420-CH and SCr420-QT 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.