What is CF3 Stainless Steel?
CF3 is an ultra-low-carbon austenitic stainless steel casting grade defined by ASTM A351. It serves as the cast equivalent of wrought AISI 304L stainless steel.
What makes CF3 stand out among casting alloys is its exceptional combination of excellent castability and weldability—the former enables reliable production of complex shapes, while the latter eliminates the need for post-weld heat treatment.
What Does “CF3” Mean?
CF3 is an engineering designation, not a chemical name. Here’s what the three characters stand for:
- C denotes the alloy is designed for corrosion service, making it suitable for oxidizing and atmospheric environments.
- F places it in the austenitic region of the Fe-Cr-Ni phase diagram, where the structure ensures good toughness and ductility.
- 3 limits the carbon content to 0.03% maximum, a level low enough to prevent chromium carbide precipitation during welding.
Chemical Composition & Material Properties of CF3
The chemical composition of CF3 is carefully controlled to achieve a balance between corrosion resistance, weldability, and mechanical strength. The maximum carbon content of 0.03% distinguishes CF3 from higher-carbon cast stainless steels and significantly reduces the risk of chromium carbide precipitation during welding.
Chemical Composition
| Element | Content (%) |
| Chromium (Cr) | 17.0 – 21.0% |
| Nickel (Ni) | 8.0 – 12.0% |
| Carbon (C) | ≤ 0.03% |
| Manganese (Mn) | ≤ 1.5% |
| Silicon (Si) | ≤1.5% |
| Phosphorus (P) | ≤ 0.04% |
| Sulfur (S) | ≤ 0.04% |
| Iron (Fe) | Balance |
Material Properties
| Properties | Value |
| Tensile Strength (min) | ≥ 485 MPa (70 ksi) |
| Yield Strength (min) | ≥ 205 MPa (30 ksi) |
| Elongation (min) | ≥ 35% |
| Hardness (Brinell) | 140 – 196 HB |
| Melting Range | 1420 – 1450 °C |
| Density | ~7.8 g/cm³ |
These properties make CF3 suitable for pressure-containing components, fluid handling equipment, and other applications where both corrosion resistance and structural reliability are required.
CF3 Equivalent Material
Although designation systems vary between countries, CF3 is recognized internationally and has equivalent grades in several major standards. Understanding these equivalents helps engineers and buyers identify compatible materials when working with international drawings or specifications.
| Standard | Material Equivalent |
| ASTM (Cast) | A351 CF3 |
| UNS | J92500 |
| Wrought Equivalent | AISI 304L |
| DIN (Germany) | 1.4309 (GX2CrNi19-11) |
| JIS (Japan) | SCS19A |
| BS (British) | 304C12 |
Because CF3 is the casting counterpart of 304L rather than the same material, engineers should consider differences in manufacturing method when selecting materials for new designs or replacement parts.
CF3 vs 304L vs CF8 vs CF3M
Material selection often depends on the operating environment, fabrication method, and manufacturing cost. While these stainless steels belong to the same family, each offers distinct advantages.
CF3 vs 304L
Chemically, CF3 and 304L are nearly identical—both Cr-Ni alloys with carbon capped at 0.03%.The difference lies in processing: 304L is wrought, while CF3 is cast.
For complex geometries, CF3 delivers the same corrosion resistance in a near-net-shape casting—saving you extensive machining time and material waste compared to wrought 304L.
CF3 vs CF8
Both are cast grades—the cast equivalents of 304L and 304—differing only in carbon: 0.03% for CF3, 0.08% for CF8.
The higher carbon in CF8 can form chromium carbides during welding of cast parts, risking corrosion unless post-weld heat treatment is applied.
With CF3, you can weld and put it into service without the extra furnace cycle—avoiding the cost and delay.
CF3 vs CF3M
Both are low-carbon cast grades—304L and 316L in casting form. The difference is molybdenum: CF3M has 2–3% Mo for pitting resistance against chlorides; CF3 has none.
In chloride-free environments, CF3 performs well at a lower material cost, so we recommend it when chlorides are not a concern—and CF3M when they are.
Why Choose CF3 for Your Custom Cast Parts
CF3 has become one of the most widely used stainless steel casting alloys because it offers an excellent balance between performance and manufacturability. Its corrosion resistance is suitable for water treatment, food processing, pharmaceutical equipment, and many general industrial services, while the ultra-low carbon content improves weldability and helps maintain corrosion resistance after fabrication.
From a foundry’s perspective, CF3 also performs exceptionally well during casting. The molten alloy exhibits good fluidity, allowing it to reproduce complex geometries with consistent dimensional accuracy. Whether manufactured by investment casting or sand casting, CF3 can produce reliable components with relatively little machining compared with parts fabricated from wrought stainless steel.
The choice between investment casting and sand casting depends largely on the size, complexity, and production volume of the component. Investment casting is generally preferred for precision parts with intricate details or tighter dimensional tolerances, while sand casting offers a more economical solution for larger components. Because CF3 performs well in both processes, manufacturers have greater flexibility to optimize production without changing the material specification.
Typical Custom CF3 Cast Parts We Manufacture
Thanks to its balanced properties, CF3 is widely specified across three main application sectors:
Valve & Fitting Components
- Valve bodies, bonnets, flanges, and pipe fittings for water, steam, and mild chemical service, where weldability and pressure integrity are essential.
- These parts are typically produced by investment casting for tight dimensional control and smooth sealing surfaces.
Pump & Impeller Parts
- Pump casings, impellers, and diffusers in clean liquid handling, food processing, and pharmaceutical systems, where corrosion resistance and smooth surface finish matter.
- Investment casting is the go-to choice for impellers with complex hydraulic profiles, while sand casting handles larger pump casings where size and strength outweigh surface finish requirements.
General Industrial Castings
- Manifolds, brackets, housings, and structural components that need the castability and weldability of CF3 without requiring the elevated corrosion resistance of molybdenum grades.
- Sand casting offers a cost-effective solution for these larger, less intricate parts.
At YTD Casting, we match the manufacturing method—whether silica sol investment casting or sand casting—to your specific geometry, production volume, and tolerance requirements.
How We Ensure the Quality of Your Custom CF3 Castings
Performance requires control at every step—whether investment-cast or sand-cast. Here’s how we ensure every CF3 casting meets your quality requirements.
Composition Verification
We test each melt with an optical emission spectrometer before pouring, confirming Cr, Ni, and carbon (≤0.03%) stay within ASTM A351 limits—weldability starts with chemistry.
Solution Treatment
Every CF3 casting is heated to 1040°C minimum and water-quenched, dissolving carbides and restoring full corrosion resistance—whether thin investment shell or heavy sand casting.
Ferrite Monitoring
We hold delta ferrite at 5–20%—enough to prevent hot tearing, low enough to preserve toughness and corrosion performance.
NDT Inspection
Radiography (RT) catches internal porosity and cracks; penetrant testing (PT) finds surface defects. Every casting, every time.
Conclusion
CF3 combines the corrosion resistance of 304L with the manufacturing advantages of stainless steel casting, making it an ideal material for valves, pumps, pipe fittings, and numerous industrial applications.
At YTD Casting, we combine proven foundry expertise, strict quality control, and flexible manufacturing processes to deliver reliable CF3 castings that meet demanding industrial requirements. Contact our engineering team to discuss your next CF3 casting project.
