Quick Answer
CF8M is the cast equivalent of 316 stainless steel, specified in ASTM A351 (pressure parts) and A743/A744 (general and corrosion-resistant service). It contains 18–21% chromium, 9–12% nickel and 2–3% molybdenum. Buyers choose it for valve and pump components, fittings and food or chemical machinery that need 316-level chloride resistance in a cast shape. If your drawing says “316 casting”, the correct callout is CF8M.
Chemical Composition (ASTM A351 CF8M)
| Element | Range |
|---|---|
| Carbon | ≤ 0.08% |
| Chromium | 18.0–21.0% |
| Nickel | 9.0–12.0% |
| Molybdenum | 2.0–3.0% |
| Manganese | ≤ 1.50% |
| Silicon | ≤ 1.50% |
| Phosphorus / Sulfur | ≤ 0.040% each |
Mechanical Properties
| Property | Minimum |
|---|---|
| Tensile strength | 485 MPa (70 ksi) |
| Yield strength | 205 MPa (30 ksi) |
| Elongation in 50 mm | 30% |
CF8M is supplied solution annealed — heated to dissolve carbides, then rapidly quenched. Skipping or botching this treatment leaves chromium carbides at grain boundaries and destroys corrosion resistance, which is why the heat-treatment certificate matters as much as the chemistry certificate.
CF8M vs Wrought 316: Three Differences Buyers Notice
- Slight magnetism. Cast CF8M contains 5–20% ferrite by design (it prevents hot tearing during solidification). A magnet sticks weakly. Wrought 316 is fully austenitic and non-magnetic. This surprises QC teams inspecting their first casting shipment — it is normal.
- Chemistry windows differ slightly. Cast grades allow more silicon for fluidity. Corrosion performance stays equivalent to wrought 316 in most media.
- Properties are direction-free. Castings have no rolling direction, useful for complex parts loaded in several directions.
Common Applications
- Valve bodies, bonnets, discs and trim for chemical and marine service
- Pump casings and impellers handling brine or aggressive media
- Food, dairy and pharmaceutical machinery parts cleaned with chlorinated agents
- Instrument housings and fittings on offshore platforms
At YCUMETAL, CF8M is one of the most-poured grades in our silica sol investment casting line, which delivers the near-net shapes and smooth surfaces that reduce machining on wetted valve internals. Dimensional and material verification runs through our standard quality assurance process.
Variants and When to Step Up
| Grade | Change vs CF8M | Use when |
|---|---|---|
| CF3M | Carbon ≤ 0.03% | Welded assemblies; avoids sensitization without re-annealing |
| CF8 | No molybdenum (cast 304) | No chlorides; save 10–20% cost |
| CD4MCu / duplex | Duplex structure, higher strength | Severe chloride pitting plus abrasion |
| CN7M (Alloy 20) | Higher Ni, Cu addition | Sulfuric acid service |
FAQ
Is CF8M exactly the same as 316?
Functionally equivalent, not chemically identical. CF8M is the casting grade engineered for pourability; 316 is the wrought grade. Corrosion behavior in service is comparable.
CF8M or CF3M for a fabrication that will be welded?
CF3M. Its low carbon prevents carbide precipitation in the heat-affected zone, so you keep corrosion resistance without post-weld solution annealing.
What certificates should I require?
Chemical analysis per heat, mechanical test results, and confirmation of solution annealing. For pressure parts, add the NDT reports your code requires.