UNS S32550 pipe (Alloy 255, DIN 1.4507, F61) is a high-performance duplex stainless steel material. Due to its excellent mechanical properties and corrosion resistance, it is widely used in petrochemical, marine engineering, energy equipment and other fields.
ASTM A790 UNS S32550 Super Duplex Welded and seamless tube manufacturer, supplier
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Chemical Composition of F61
S32550 steel contains about 25% chromium, 6.5% nickel, 3% molybdenum and 0.2% nitrogen. The high chromium content provides basic corrosion resistance, the molybdenum element significantly improves the resistance to pitting and crevice corrosion, and the addition of nitrogen not only enhances strength, but also promotes the formation of austenite phase.
mechanical properties of 1.4507
The typical tensile strength of S32550 pipe after solid solution treatment can reach 800-1000MPa, the yield strength is ≥550MPa, and the elongation remains above 25%. Its strength is twice that of ordinary austenitic stainless steel, while maintaining good impact toughness.
Super duplex 255 pipe corrosion resistance
The corrosion resistance shows multi-dimensional advantages. In a medium-concentration sulfuric acid environment below 80°C, its corrosion rate is less than 0.1mm/year, in a simulated seawater environment containing 20000ppm chloride ions, the critical pitting temperature exceeds 60°C.
manufacturing process of UNS S32550
The hot forming temperature should be controlled in the range of 1050-1150℃, and the water cooling rate should be guaranteed to be ≥50℃/s to prevent the precipitation of σ phase. 22.8.3L welding material is recommended for welding, and the interlayer temperature is strictly limited to less than 150℃.
255 pipe Performance comparison with competing materials
Compared with 2205 duplex steel (S32205): S32550 has a higher PREN value (38-40), a 40% increase in chloride stress corrosion resistance, and significantly superior strength (tensile strength ≥750MPa vs. 620MPa).
Compared with austenitic stainless steel 316L: S32550 has a yield strength (≥550MPa) that is more than twice that of 316L, and a higher pitting temperature (CPT≥60℃), but slightly inferior cold formability, requiring preheating at 200℃ to reduce the work hardening rate.
Compared with nickel-based alloys: In seawater environments, the corrosion resistance of S32550 is comparable to that of 625 alloy, but the cost is only 1/3 of the latter, with outstanding cost performance.
