ASTM A351 Grade CF8M
The ASTM molybdenum-bearing austenitic stainless casting grade; worldwide, the first material that comes to mind for stainless valve bodies. Its Cr and Ni ranges are wider than for wrought 316, and the cast structure contains some ferrite.
- Rp0.2 · MPa
- ≥ 205
- Rm · MPa
- ≥ 485
- TEMPERATURE
- −196 … +538 °C
- COST
Chemical composition
%, single values are maximums.
Mechanical properties
| STANDARD · CONDITION | Rp0.2 MPa | Rp1.0 MPa | Rm MPa | A % | KV J |
|---|---|---|---|---|---|
| ASTM A351 · CF8M | 205 | — | ≥ 485 | 30 | — |
Room temperature, solution annealed. Hardness typically 156–170 HB.
ASME B16.34 pressure-temperature ratings
| CLASS · bar | −29 … 38 °C | 100 °C | 200 °C | 300 °C | 400 °C | 500 °C |
|---|---|---|---|---|---|---|
| Class 150 | 19.0 | 16.2 | 13.7 | 10.2 | 6.5 | 2.8 |
| Class 300 | 49.6 | 42.2 | 35.7 | 31.6 | 29.4 | 28.2 |
| Class 600 | 99.3 | 84.4 | 71.3 | 63.2 | 58.9 | 56.5 |
| Class 900 | 148.9 | 126.6 | 107.0 | 94.9 | 88.3 | 84.7 |
| Class 1500 | 248.2 | 211.0 | 178.3 | 158.1 | 147.2 | 140.9 |
| Class 2500 | 413.7 | 351.6 | 297.2 | 263.5 | 245.3 | 235.0 |
Standard class, bar. Material group: CF8M/CF3M. Greyed values are outside the material's service range (−196 … +538 °C). Flanged-end ratings end at 538 °C.
Service temperature
This is the limit of the material itself. A valve's service temperature is usually set by the seal and seat materials; product pages give it for each seal option.
Physical properties and heat treatment
- HEAT TREATMENT
- Solution annealing ≥ 1040 °C, rapid cooling.
Media suitability GENERAL TREND
Emsal assessment. The final choice is made from corrosion tables, taking concentration, temperature, chloride content and flow velocity into account.
Strengths and weaknesses
Strengths
- The world standard for stainless valve bodies, available at every foundry
- The ferrite content prevents hot cracking in casting and welding
- Wide temperature range: from cryogenic to high temperatures
Weaknesses
- Risk of pitting in warm seawater
- Non-destructive testing may be required for casting defects
- Half the proof strength of duplex castings
Manufacturing and use
- ECONOMY
- Medium. The most economical molybdenum-bearing option for stainless cast bodies.
- MANUFACTURING METHODS
- Sand casting · Investment casting (lost wax)
- TYPICAL VALVE PARTS
- Body · Bonnet · Disc, ball
Source: ASTM A351. Values compiled and verified by Emsal Vana; for binding values, refer to the current edition of the standard and the material certificate.