Super Duplex Stainless Steels (including UNS S32750 / 2507, UNS S32760 / Zeron® 100, UNS S32550 / Ferralium® 255, UNS S32707 Hyper Duplex, and UNS S32950) represent the apex of dual-phase austenitic-ferritic metallurgical design. Formulated with 25%–27% chromium, 6%–8% nickel, 3.5%–5% molybdenum, high nitrogen (0.20%–0.50%), and synergistic additions of tungsten and copper, Super Duplex alloys deliver a Pitting Resistance Equivalent Number (PREN) consistently exceeding 42 (and up to PREN 50 for hyper duplex). Exhibiting exceptional minimum yield strengths exceeding 550 MPa (approx. 80 ksi)—nearly triple that of annealed austenitic 316L—Super Duplex Stainless Steels offer near-total immunity to chloride stress corrosion cracking (SCC), extreme resistance to crevice corrosion in hot chlorinated seawater, and high mechanical fatigue resistance. These premium metallurgical properties make Super Duplex bolts, heavy hex studs, nuts, socket screws, and custom precision-machined fasteners the standard engineering requirement for critical subsea oil & gas Christmas trees, riser bolting, high-pressure desalination reverse-osmosis pumps, flue-gas desulfurization (FGD) scrubbers, marine defense platforms, and severe chemical processing environments.
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