X2CrNiMoN25-7-4
Super duplex stainless steel: 25% Cr, 4% Mo, high nitrogen. Combines high strength with very high corrosion resistance in warm seawater, brine and aggressive chloride environments.
- Rp0.2 · MPa
- ≥ 530
- Rm · MPa
- ≥ 730
- TEMPERATURE
- ≤ +300 °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) | 530 | — | ≥ 730 | 20 | 60 |
| EN 10088-3 · bar, t ≤ 160 mm | 530 | — | 730–930 | 25 | — |
| ASTM A240 · S32750 | 550 | — | ≥ 795 | 15 | — |
Room temperature, solution annealed.
Minimum Rp0.2 at elevated temperature
| EN · TEMPERATURE | 20 °C | 100 °C | 200 °C |
|---|---|---|---|
| Rp0.2 MPa | 530 | 450 | 400 |
EN 10028-7 / EN 10088 values; the minimum proof strength used in pressure equipment design.
Service temperature
The duplex structure is not used for long periods above ~300 °C (475 °C embrittlement). Toughness drops at low temperature because of the ferrite.
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
- 7.8 kg/dm³
- MODULUS OF ELASTICITY (20 °C)
- 200 GPa
- THERMAL EXPANSION (20–100 °C)
- 13.0 × 10⁻⁶ /K
- THERMAL CONDUCTIVITY (20 °C)
- 15 W/m·K
- SPECIFIC HEAT (20 °C)
- 500 J/kg·K
- ELECTRICAL RESISTIVITY
- 0.80 µΩ·m
- MAGNETISM
- magnetic
- CRITICAL PITTING TEMPERATURE, CPT (TYPICAL)
- 84 ± 2 °C
- HEAT TREATMENT
- Solution annealing 1080 ± 40 °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 most resistant steel class in seawater (CPT ≈ 84 °C)
- Proof strength ≥ 530 MPa: thin walls at high pressure
- Resistant to erosion and cavitation
Weaknesses
- Risk of sigma phase: heat treatment and welding need strict control
- Limited above ~300 °C and at low temperature
- Expensive, difficult to machine
Manufacturing and use
- ECONOMY
- High; about 30–50% more expensive than 2205.
- MANUFACTURING METHODS
- Machining from bar and forging · Cast counterpart 1.4469 (5A)
- TYPICAL VALVE PARTS
- Seawater valve body · Stem · Disc · Bolt
Used in 2 Emsal products
- 001Wafer check valveBody · Disc
- 005Short pattern swing check valveDisc
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.