Stainless Steel 304C15-AC vs 304C15-ST
Stainless Steel · 304C15 temper comparison
304C15-AC and 304C15-ST are two conditions of the same stainless steel grade, 304C15: AC (spheroidize annealed) versus ST (solution annealed). The chemistry is identical, so every difference below comes from the condition. Both yield at about 245 MPa — the mechanical properties are the same, and the difference is in how the stock is processed and what it is certified to (spheroidize annealed versus solution annealed). 304C15-ST is the more ductile: elongation 55% versus 32% for 304C15-AC, and 304C15-AC is harder (155 HB vs 140 HB). 304C15-ST runs hotter in service (760°C vs 425°C continuous).
304C15-STChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
304C15-AC vs 304C15-ST: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all stainless 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 stainless 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
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Same in both: Elastic (Young's) Modulus 193 GPa28 Msi · Shear Modulus 75 GPa10.9 Msi · Bulk Modulus 145 GPa21 Msi · Poisson's Ratio 0.3 · Compressive Strength 250 MPa36.3 ksi · Shear Strength 350 MPa50.8 ksi · Fatigue Strength (Endurance Limit) 220 MPa31.9 ksi · Fracture Toughness (K_IC) 200 MPa·√m182 ksi·√in
Physical
Density and transition temperatures.
Same in both: Density 7.75 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,400°C2,552 °F · Liquidus Temperature 1,450°C2,642 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 16.2 W/m·K9.4 BTU/hr·ft·°F · Specific Heat Capacity 500 J/kg·K0.12 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 17.3 µm/m·K9.6 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Min Service Temperature -196°C-321 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 2.4 % IACS · Electrical Resistivity 7.2×10⁻⁷ Ω·m28.3 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.08 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Same in both: Weldability 85 / 100 · Formability (cold) 25 / 100 · Castability 72 / 100 · Brazeability / Solderability 55 / 100 · Polishability 62 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 53 MJ/kg22,786 BTU/lb · Embodied Carbon (primary production) 4.2 kg CO₂/kg · Embodied Water 200 L/kg24 gal/lb · Typical Recycled Content 70%
Strength versus weight
Yield strength against density for every stainless steel grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
304C15-AC vs 304C15-ST — frequently asked
What is the difference between 304C15-AC and 304C15-ST?
304C15-AC and 304C15-ST are two conditions of the same stainless steel grade, 304C15: AC (spheroidize annealed) versus ST (solution annealed). The chemistry is identical, so every difference below comes from the condition. Both yield at about 245 MPa — the mechanical properties are the same, and the difference is in how the stock is processed and what it is certified to (spheroidize annealed versus solution annealed).
Which condition does FabDigit quote by default, AC or ST?
ST is the default 304C15 condition in the FabDigit quote flow. 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 304C15-AC over 304C15-ST?
Pick 304C15-ST when the part is bent, formed or impact-loaded, or when the part sees heat.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 304C15-AC and 304C15-ST 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.