Stainless Steel CF8A-AC (Spheroidize annealed)
Heat-treated state
ASTM CF8A · UNS J92600
Only for non-pressure, non-corrosive structural parts; carbides at grain boundaries make it unacceptable for ASTM A351 service.
Values for the AC condition
Other CF8A tempers and conditions
CF8A is listed in 4 conditions; see the grade overview at CF8A.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ACThis page Spheroidize annealed | Only for non-pressure, non-corrosive structural parts; carbides at grain boundaries make it unacceptable for ASTM A351 service. | 260 | 500 | 30 | 170 HB | 2.4 % IACS |
SADefault Solution annealed (≥1040 °C, water quenched), static sand/investment… | Standard supply condition for all ASTM A351 CF8A pressure castings; maximum corrosion resistance and toughness. | 275 | 550 | 50 | 155 HB | — |
Hot isostatically pressed then solution annealed | Use where internal microporosity must be eliminated for fatigue-critical or high-integrity radiographed castings. | 285 | 570 | 55 | 155 HB | 2.4 % IACS |
Centrifugally cast tube/ring, solution annealed | Choose for cylindrical pressure parts (pipe, valve liners) where centrifugal soundness raises strength and lowers porosity. | 300 | 585 | 45 | 160 HB | 2.4 % IACS |
What is CF8A-AC?
CF8A-AC is CF8A heat treated to AC — only for non-pressure, non-corrosive structural parts; carbides at grain boundaries make it unacceptable for ASTM A351 service. CF8A-AC has a yield strength of 260 MPa (37.7 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 84% of stainless steel grades. Elongation at break is 30% and the elastic modulus is 195 GPa (28.3 Msi). CF8A-AC has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,400°C (2,552 °F). SA is the default condition FabDigit quotes; AC is available on request or by drawing note.
Limitations
- Limited formability — 10/100, worse than 95% of stainless steel grades
- Low strength — 260 MPa (37.7 ksi), worse than 84% of stainless steel grades
- Hard to polish — 60/100, worse than 80% of stainless steel grades
- Needs corrosion protection — 50/100, worse than 78% of stainless steel grades
CF8A-AC properties
Typical room-temperature values for CF8A-AC; 22 are specific to this condition. Other listed values are CF8A reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
CF8A-AC has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical15
CF8A-AC has a yield strength of 260 MPa (37.7 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 84% of stainless steel grades. Elongation at break is 30% and the elastic modulus is 195 GPa (28.3 Msi).
Thermal6
CF8A-AC is rated for continuous service to 550°C (1,022 °F). It conducts heat at 16.2 W/m·K (9.36 BTU/hr·ft·°F), better than 64% of stainless steel grades. Thermal expansion is 17 µm/m·K (9.44 µin/in·°F).
Electrical3
CF8A-AC conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (50/100), worse than 78% of stainless steel grades.
Sustainability4
Producing a kilogram of CF8A-AC takes about 53 MJ of energy and emits 4.5 kg of CO₂ — less than 67% of stainless steel grades. Typical recycled content is 80%.
Manufacturability8
CF8A-AC's machinability is fair (35/100, better than 51% of stainless steel grades); weldability good (65/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with CF8A-AC
Is CF8A easy to machine?
Machine like 304: rigid setups, sharp positive-rake carbide, heavy positive feed to cut under the work-hardened skin, flood coolant, and expect abrasive casting scale on the first pass.
Can CF8A be welded?
Excellent weldability with GTAW/SMAW using E308/ER308 (or 308L for corrosive duty); the 5–20 % ferrite suppresses hot cracking, no preheat needed, keep interpass below ~150 °C.
Can CF8A be formed, bent or molded?
Sand or investment cast with generous risering — long freezing range and 2.2 % solidification shrinkage require good gating; solution anneal ≥1040 °C with water quench after casting/repair welding.
What surface finishes work on CF8A?
Passivate per ASTM A967 (nitric or citric) after machining; shot blast plus pickling removes casting scale, and electropolishing gives sanitary finishes though porosity limits mirror polish.
CF8A 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 | ≤ 0.08 | 0.06 |
| Mn | ≤ 1.5 | 1 |
| Si | ≤ 2 | 1.3 |
| P | ≤ 0.04 | 0.03 |
| S | ≤ 0.04 | 0.02 |
| Cr | 18 – 21 | 19.5 |
| Nibalanced toward the low side to raise ferrite and meet the higher CF8A strength | 8 – 11 | 9 |
| Moresidual, per A351 supplementary limits | ≤ 0.5 | 0.2 |
| Fe | balance | — |
CF8A-AC — frequently asked
What is CF8A-AC used for?
CF8A-AC is typically used for valve bodies, pump housings, pressure vessel fittings and general chemical service castings. In short: high-strength CF8 variant; 650 °C service capability; standard 19Cr-9Ni casting.
What is the yield strength of CF8A-AC?
CF8A-AC has a typical yield strength of 260 MPa (37.7 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 84% of stainless steel grades. Strength varies by condition: see the 4 listed tempers.
Is CF8A-AC easy to machine?
Not especially — machinability is rated fair (35/100, better than 51% of stainless steel grades). Machine like 304: rigid setups, sharp positive-rake carbide, heavy positive feed to cut under the work-hardened skin, flood coolant, and expect abrasive casting scale on the first pass.
Can CF8A-AC be welded?
Yes — weldability is rated good (65/100). Excellent weldability with GTAW/SMAW using E308/ER308 (or 308L for corrosive duty); the 5–20 % ferrite suppresses hot cracking, no preheat needed, keep interpass below ~150 °C.
What surface finishes work on CF8A-AC?
Passivate per ASTM A967 (nitric or citric) after machining; shot blast plus pickling removes casting scale, and electropolishing gives sanitary finishes though porosity limits mirror polish.
Can CF8A-AC be formed, bent or molded?
Sand or investment cast with generous risering — long freezing range and 2.2 % solidification shrinkage require good gating; solution anneal ≥1040 °C with water quench after casting/repair welding.
What is the maximum service temperature of CF8A-AC?
CF8A-AC is rated for continuous use to about 550°C (1,022 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between CF8A-SA and CF8A SA-CENT?
SA is the default condition — standard supply condition for all ASTM A351 CF8A pressure castings; maximum corrosion resistance and toughness. SA-CENT: choose for cylindrical pressure parts (pipe, valve liners) where centrifugal soundness raises strength and lowers porosity. Yield strength is 275 MPa in SA versus 300 MPa in SA-CENT.
Sources
- ASTM A351/A351M — Castings, Austenitic, for Pressure-Containing Parts — ASTM International (2018)
- ASTM A451/A451M — Centrifugally Cast Austenitic Steel Pipe for High-Temperature Service — ASTM International (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (Cast Stainless Steels) — ASM International (1990)
- Steel Castings Handbook, 6th ed. — Steel Founders' Society of America / ASM (1995)
- GB/T 12230 (ZG07Cr19Ni9) — SAC (2016)
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.