Stainless Steel CT15C-AC (Spheroidize annealed)
Heat-treated state
UNS N08151
Used for non-pressure, high-temperature furnace hardware where interdendritic carbides are acceptable and creep life matters more than room-temperature ductility.
Values for the AC condition
Other CT15C tempers and conditions
CT15C is listed in 3 conditions; see the grade overview at CT15C.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SADefault Solution annealed | Standard supply condition for pressure-containing castings to ASTM A351/A743; best ductility and corrosion resistance. | 240 | 490 | 30 | 170 HB | 1.7 % IACS |
ACThis page Spheroidize annealed | Used for non-pressure, high-temperature furnace hardware where interdendritic carbides are acceptable and creep life matters more than room-temperature ductility. | 255 | 470 | 18 | 180 HB | 1.7 % IACS |
Centrifugally cast, solution annealed | Choose for tubes, sleeves and rings where the denser, more directional centrifugal structure gives higher strength and better soundness than static castings. | 260 | 525 | 28 | 175 HB | 1.7 % IACS |
What is CT15C-AC?
CT15C-AC is CT15C heat treated to AC — used for non-pressure, high-temperature furnace hardware where interdendritic carbides are acceptable and creep life matters more than room-temperature ductility. CT15C-AC has a yield strength of 255 MPa (37 ksi) and a tensile strength of 470 MPa (68.2 ksi) — weaker than 87% of stainless steel grades. Elongation at break is 18% and the elastic modulus is 193 GPa (28 Msi). CT15C-AC has a density of 7.9 g/cm³ (0.285 lb/in³), heavier than 68% of stainless steel grades. It melts at 1,340°C (2,444 °F). SA is the default condition FabDigit quotes; AC is available on request or by drawing note.
Advantages
- High service temperature — 1,050°C (1,922 °F), better than 91% of stainless steel grades
Limitations
- Low electrical conductivity — 1.7 % IACS, worse than 98% of stainless steel grades
- Poor heat conductor — 12 W/m·K (6.93 BTU/hr·ft·°F), worse than 93% of stainless steel grades
- Limited formability — 12/100, worse than 93% of stainless steel grades
- Hard to polish — 55/100, worse than 89% of stainless steel grades
- High embodied carbon — 6 kg CO₂/kg, worse than 88% of stainless steel grades
CT15C-AC properties
Typical room-temperature values for CT15C-AC; 22 are specific to this condition. Other listed values are CT15C reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
CT15C-AC has a density of 7.9 g/cm³ (0.285 lb/in³), heavier than 68% of stainless steel grades. It melts at 1,340°C (2,444 °F).
Mechanical16
CT15C-AC has a yield strength of 255 MPa (37 ksi) and a tensile strength of 470 MPa (68.2 ksi) — weaker than 87% of stainless steel grades. Elongation at break is 18% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
CT15C-AC is rated for continuous service to 1,050°C (1,922 °F). It conducts heat at 12 W/m·K (6.93 BTU/hr·ft·°F), worse than 93% of stainless steel grades. Thermal expansion is 15 µm/m·K (8.33 µin/in·°F).
Electrical3
CT15C-AC conducts electricity at 1.7 % IACS, worse than 98% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (63/100), better than 53% of stainless steel grades.
Sustainability4
Producing a kilogram of CT15C-AC takes about 85 MJ of energy and emits 6 kg of CO₂ — more than 92% of stainless steel grades. Typical recycled content is 60%.
Manufacturability7
CT15C-AC's machinability is poor (26/100, worse than 84% of stainless steel grades); weldability fair (50/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with CT15C-AC
Is CT15C easy to machine?
Machine with rigid setups, sharp carbide or ceramic tooling, slow speeds and heavy positive feeds to cut under the work-hardened skin; flood coolant essential.
Can CT15C be welded?
GTAW/SMAW with Ni-base (ERNiCr-3 / ENiCrFe-type) or matching Nb-bearing filler, low heat input, no preheat needed; solution anneal after major repair welds on pressure castings.
Can CT15C be formed, bent or molded?
Supplied as static or centrifugal castings; feed heavy sections generously and control Si/Nb to avoid interdendritic shrinkage — cold forming is not applicable.
What surface finishes work on CT15C?
Sand/shot blast and pickle-passivate to restore the chromium oxide film; can be ground and polished, though the cast dendritic structure limits mirror finishes.
CT15C chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | 0.05 – 0.15 | 0.1 |
| Mn | 0.15 – 1.5 | 0.8 |
| Si | 0.5 – 1.5 | 1 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cr | 19 – 21 | 20 |
| Ni | 31 – 34 | 32.5 |
| Nbcolumbium, carbide stabilizer | 0.5 – 1.5 | 1 |
| Fe | balance | — |
CT15C-AC — frequently asked
What is CT15C-AC used for?
CT15C-AC is typically used for chemical process pumps, valves for mixed-acid service and pollution control equipment. In short: cast Alloy 825 equivalent; mixed acid resistance; service to 1000 °C.
What is the yield strength of CT15C-AC?
CT15C-AC has a typical yield strength of 255 MPa (37 ksi) and a tensile strength of 470 MPa (68.2 ksi) — weaker than 87% of stainless steel grades. Strength varies by condition: see the 3 listed tempers.
Is CT15C-AC easy to machine?
Not especially — machinability is rated poor (26/100, worse than 84% of stainless steel grades). Machine with rigid setups, sharp carbide or ceramic tooling, slow speeds and heavy positive feeds to cut under the work-hardened skin; flood coolant essential.
Can CT15C-AC be welded?
With care — weldability is rated fair (50/100). GTAW/SMAW with Ni-base (ERNiCr-3 / ENiCrFe-type) or matching Nb-bearing filler, low heat input, no preheat needed; solution anneal after major repair welds on pressure castings.
What surface finishes work on CT15C-AC?
Sand/shot blast and pickle-passivate to restore the chromium oxide film; can be ground and polished, though the cast dendritic structure limits mirror finishes.
Can CT15C-AC be formed, bent or molded?
Supplied as static or centrifugal castings; feed heavy sections generously and control Si/Nb to avoid interdendritic shrinkage — cold forming is not applicable.
What is the maximum service temperature of CT15C-AC?
CT15C-AC is rated for continuous use to about 1,050°C (1,922 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between CT15C-SA and CT15C CC-SA?
SA is the default condition — standard supply condition for pressure-containing castings to ASTM A351/A743; best ductility and corrosion resistance. CC-SA: choose for tubes, sleeves and rings where the denser, more directional centrifugal structure gives higher strength and better soundness than static castings. Yield strength is 240 MPa in SA versus 260 MPa in CC-SA.
Sources
- ASTM A351/A351M — Castings, Austenitic, for Pressure-Containing Parts — ASTM International (2018)
- ASTM A743/A743M — Castings, Iron-Chromium, Iron-Chromium-Nickel, Corrosion Resistant — ASTM International (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (heat- and corrosion-resistant castings) — ASM International (1990)
- ASM Handbook Vol.13B — Corrosion: Materials — ASM International (2005)
- UNS N08151 alloy designation data — SAE/ASTM Unified Numbering System (2019)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.