Steel C8C +AC vs C8C +U
Steel · C8C temper comparison
C8C +AC and C8C +U are two conditions of the same steel grade, C8C: +AC (spheroidize annealed) versus +U (hot rolled). The chemistry is identical, so every difference below comes from the condition. C8C +U is the stronger of the two: yield strength 215 MPa (31.2 ksi) against 190 MPa (27.6 ksi) for C8C +AC, about 13% more; tensile strength follows at 340 MPa (49.3 ksi) vs 320 MPa (46.4 ksi). In exchange, C8C +AC is the more ductile: elongation 36% versus 32% for C8C +U, and C8C +U is harder (100 HB vs 95 HB).
C8C +ACChoose it when the part is bent, formed or impact-loaded.
C8C +UChoose it when strength drives the design.
C8C +AC vs C8C +U: 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
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
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,495°C2,723 °F · Liquidus Temperature 1,525°C2,777 °F
Thermal
How each material carries heat and how hot it can run.
Same in both: Thermal Conductivity 51 W/m·K29.5 BTU/hr·ft·°F · Specific Heat Capacity 470 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 12 µm/m·K6.7 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Max Service Temperature (continuous) 400°C752 °F · Min Service Temperature -20°C-4 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 11 % 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) -0.61 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 %)
Formability (cold)
Same in both: Weldability 96 / 100 · Castability 30 / 100 · Brazeability / Solderability 75 / 100 · Polishability 50 / 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.
C8C +AC vs C8C +U — frequently asked
Is C8C +U stronger than C8C +AC?
Yes. C8C +U has a typical yield strength of 215 MPa (31.2 ksi) against 190 MPa (27.6 ksi) for C8C +AC — about 13% more. Tensile strength is 340 MPa (49.3 ksi) vs 320 MPa (46.4 ksi).
Which condition does FabDigit quote by default, +AC or +U?
+U+C is the default C8C condition in the FabDigit quote flow (neither +AC nor +U). 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.
When should I choose C8C +AC over C8C +U?
Pick C8C +AC when the part is bent, formed or impact-loaded. Pick C8C +U when strength drives the design.
Ready to make it?
Upload a CAD file and FabDigit prices the part in C8C +AC and C8C +U 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.