Steel C20C +AC vs C20C-CH
Steel · C20C temper comparison
C20C +AC and C20C-CH are two conditions of the same steel grade, C20C: +AC (spheroidize annealed) versus CH (carburized and hardened). The chemistry is identical, so every difference below comes from the condition. C20C-CH is the stronger of the two: yield strength 400 MPa (58 ksi) against 250 MPa (36.3 ksi) for C20C +AC, about 60% more; tensile strength follows at 600 MPa (87 ksi) vs 400 MPa (58 ksi). In exchange, C20C +AC is the more ductile: elongation 33% versus 13% for C20C-CH, and C20C-CH is harder (200 HB vs 112 HB). C20C +AC runs hotter in service (350°C vs 180°C continuous). On the shop floor, C20C +AC machines more easily (fair vs poor) and C20C +AC welds better (excellent vs poor).
C20C +ACChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
C20C-CHChoose it when strength drives the design.
C20C +AC vs C20C-CH: 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
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 205 GPa29.7 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Compressive Strength 390 MPa56.6 ksi · Shear Strength 330 MPa47.9 ksi · Fracture Toughness (K_IC) 105 MPa·√m95.6 ksi·√in
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,460°C2,660 °F · Liquidus Temperature 1,518°C2,764 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 51.9 W/m·K30 BTU/hr·ft·°F · Specific Heat Capacity 486 J/kg·K0.12 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 11.7 µm/m·K6.5 µin/in·°F · Latent Heat of Fusion 247 J/g106 BTU/lb · Min Service Temperature -20°C-4 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 10.8 % IACS · Electrical Resistivity 1.6×10⁻⁷ Ω·m6.3 µΩ·in
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 75 / 100 · Polishability 45 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 25 MJ/kg10,748 BTU/lb · Embodied Carbon (primary production) 2 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.
C20C +AC vs C20C-CH — frequently asked
Is C20C-CH stronger than C20C +AC?
Yes. C20C-CH has a typical yield strength of 400 MPa (58 ksi) against 250 MPa (36.3 ksi) for C20C +AC — about 60% more. Tensile strength is 600 MPa (87 ksi) vs 400 MPa (58 ksi).
Which condition does FabDigit quote by default, +AC or CH?
+U+C is the default C20C condition in the FabDigit quote flow (neither +AC nor CH). 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, C20C +AC or C20C-CH?
C20C +AC. Its machinability rates fair (53/100) against poor (15/100) for C20C-CH; for welding the order is C20C +AC first (excellent, 95/100) then C20C-CH (poor, 30/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in C20C +AC and C20C-CH 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.