1. What is EN 10297 X1CrNiMoCuN20-18-7?
Answer:
EN 10297 X1CrNiMoCuN20-18-7 is a super duplex stainless steel seamless tube standardized under EN 10297, combining austenitic and ferritic microstructures for extreme performance.
Key Composition: 20% Cr, 18% Ni, 7% Mo, 0.5% Cu, and nitrogen (N) for strength stabilization.
Equivalent Grades: UNS S32707 (Zeron 100), DIN 1.4501.
Key Feature: Exceptional PREN >45, offering unmatched resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC) in chloride/sulfide environments.
2. What are the mechanical properties?
Answer (solution-annealed condition):
Tensile Strength: 800–1000 MPa (higher than standard duplex grades)
Yield Strength (0.2% offset): ≥550 MPa
Elongation: ≥25%
Hardness: 290–350 HB
Note: The duplex structure provides twice the yield strength of 316L while maintaining toughness.
3. How does it compare to standard duplex grades like 2205 (X2CrNiMoN22-5-3)?
Answer:
Alloy Superiority: Higher Mo (7% vs. 3%) and Ni (18% vs. 5%) enable use in hot concentrated chlorides (e.g., seawater at >60°C).
Cost: Premium pricing due to alloy content, but lifespan in harsh environments justifies investment.
Welding Complexity: Requires stricter heat control to avoid intermetallic phase formation.
4. What are critical fabrication guidelines?
Answer:
Welding: Use TIG with ERNiCrMo-10 or ER2594 filler. Keep interpass temperature <100°C.
Machining: High strength demands ceramic or carbide tools with low feed rates.
Heat Treatment: Solution anneal at 1020–1100°C followed by water quenching to avoid σ-phase.
5. Where is this grade primarily used?
Answer:
Oil & Gas: Subsea pipelines, Christmas trees (resists H₂S/CO₂ at high pressures).
Chemical Processing: Reactors for hydrochloric acid and sulfuric acid mixtures.
Desalination: High-pressure RO membranes and brine heaters.
Nuclear: Coolant systems in aggressive media.
