Steel C2C +AC vs C2C +U
Steel · C2C temper comparison
C2C +AC and C2C +U are two conditions of the same steel grade, C2C: +AC (spheroidize annealed) versus +U (hot rolled). The chemistry is identical, so every difference below comes from the condition. C2C +U is the stronger of the two: yield strength 210 MPa (30.5 ksi) against 180 MPa (26.1 ksi) for C2C +AC, about 17% more; tensile strength follows at 320 MPa (46.4 ksi) vs 295 MPa (42.8 ksi). C2C +U is harder — 95 HB against 88 HB for C2C +AC — which matters for wear surfaces and threads. C2C +AC runs hotter in service (350°C vs 300°C continuous).
C2C +ACChoose it when the part sees heat.
C2C +UChoose it when strength drives the design, or when surface hardness matters.
C2C +AC vs C2C +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
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
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
Physical
Density and transition temperatures.
Same in both: Density 7.87 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,500°C2,732 °F · Liquidus Temperature 1,535°C2,795 °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 480 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 247 J/g106 BTU/lb · Min Service Temperature -50°C-58 °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) -0.61 V · Corrosion Resistance 10 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Formability (cold)
Same in both: Machinability Rating (AISI 1212 = 100 %) 48% · Weldability 96 / 100 · Brazeability / Solderability 75 / 100 · Polishability 45 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 26 MJ/kg11,178 BTU/lb · Embodied Carbon (primary production) 2.1 kg CO₂/kg · Embodied Water 40 L/kg4.8 gal/lb · Typical Recycled Content 25%
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.
C2C +AC vs C2C +U — frequently asked
Is C2C +U stronger than C2C +AC?
Yes. C2C +U has a typical yield strength of 210 MPa (30.5 ksi) against 180 MPa (26.1 ksi) for C2C +AC — about 17% more. Tensile strength is 320 MPa (46.4 ksi) vs 295 MPa (42.8 ksi).
Which condition does FabDigit quote by default, +AC or +U?
+U+C is the default C2C 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 C2C +AC over C2C +U?
Pick C2C +AC when the part sees heat. Pick C2C +U when strength drives the design, or when surface hardness matters.
Ready to make it?
Upload a CAD file and FabDigit prices the part in C2C +AC and C2C +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.