X1CrNiMoCuN20-18-7
Super austenitic stainless steel with 6% molybdenum. Very high resistance to pitting and crevice corrosion in seawater, brine cooling circuits and chloride-bearing process water.
- Rp0.2 · MPa
- ≥ 300
- Rm · MPa
- 650–850
- TEMPERATURE
- −196 … +400 °C
- COST
Chemical composition
Mechanical properties
| STANDARD · CONDITION | Rp0.2 MPa | Rp1.0 MPa | Rm MPa | A % | KV J |
|---|---|---|---|---|---|
| EN 10088-2 · hot-rolled plate (P) | 300 | 340 | 650–850 | 40 | 60 |
| ASTM · S31254 | 310 | — | ≥ 655 | 35 | — |
Minimum Rp0.2 at elevated temperature
| EN · TEMPERATURE | 20 °C | 100 °C | 200 °C | 400 °C |
|---|---|---|---|---|
| Rp0.2 MPa | 300 | 230 | 190 | 160 |
EN 10028-7 / EN 10088 values; the minimum proof strength used in pressure equipment design.
Service temperature
Not used below −196 °C (EN). Upper limit 400 °C (752 °F): the maximum design temperature in ASME Section VIII Div. 1.
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
- DENSITY
- 8.0 kg/dm³
- MODULUS OF ELASTICITY (20 °C)
- 195 GPa
- THERMAL EXPANSION (20–100 °C)
- 16.5 × 10⁻⁶ /K
- THERMAL CONDUCTIVITY (20 °C)
- 14 W/m·K
- SPECIFIC HEAT (20 °C)
- 500 J/kg·K
- ELECTRICAL RESISTIVITY
- 0.85 µΩ·m
- MAGNETISM
- non-magnetic (solution annealed)
- CRITICAL PITTING TEMPERATURE, CPT (TYPICAL)
- 87 ± 3 °C
- HEAT TREATMENT
- Solution annealing 1175 ± 25 °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 highest seawater resistance among austenitic grades (CPT ≈ 87 °C)
- Austenitic structure: tough, suitable for cryogenic service
- Easier to form and weld than duplex
Weaknesses
- Very expensive and limited stock
- Molybdenum segregation in welds: a higher-alloyed filler wire is required
- Difficult to machine
Manufacturing and use
- ECONOMY
- Very high; about 4–5 times the price of 316L.
- MANUFACTURING METHODS
- Machining from plate and bar · Welded construction
- TYPICAL VALVE PARTS
- Seawater valve body · Disc · Stem
Source: EN 10088-2 / -3. Values compiled and verified by Emsal Vana; for binding values, refer to the current edition of the standard and the material certificate.