TorqBolt Inc. produces fully certified Duplex 2205 fasteners (UNS S32205 / UNS S31803 / EN 1.4462) engineered for extreme mechanical loading and severe chloride stress-corrosion environments. By uniting high-integrity hot forging and ultra-precise CNC machining under an ISO 9001:2015 and PED 2014/68/EU certified framework, we deliver the structural assurance essential for offshore platforms, subsea pipelines, chemical processing plants, and marine desalination units worldwide.
With our registered headquarters in Mumbai and primary manufacturing infrastructure situated in Rajkot, Gujarat, TorqBolt controls every facet of production—from the sourcing of European/reputed primary melt bars to controlled solution annealing (1040°C to 1100°C), rapid water quenching, continuous rolled threading, and stringent metallurgical verification. Every production batch is backed by EN 10204 Type 3.1 mill test certificates as standard, while Type 3.2 inspection witnessed by DNV, Lloyd's, ABS, or Bureau Veritas is readily accommodated for mission-critical engineering projects.
TorqBolt manufactures an exhaustive matrix of Duplex 2205 fastening components conforming to ASME, ASTM, DIN, ISO, and bespoke engineering drawings. Rolled threads are standard across high-pressure studs and bolts to preserve uncompromised fatigue strength.
All-thread, double-end, and tap-end stud bolts optimized for ASME B16.5 / B16.47 pressure piping and subsea riser flanges. Cold rolled threads guarantee superior fatigue resistance under high preloads.
Hot-forged and precision-machined standard and heavy hex head bolts. Ideal for marine structural bolting, valves, flowlines, and pumps requiring over twice the yield strength of 316 stainless.
Finished hex and heavy hex nuts manufactured to ASTM A194 Gr. 2205/F51 specifications. Heat-treated with hardness controls to pair seamlessly with studs, avoiding galling or thread stripping.
Through-hardened flat washers, Belleville disc springs, and spherical washers designed to maintain clamp load and protect joint surfaces in aggressive offshore seawater environments.
Duplex 2205 is a nitrogen-enhanced austenitic-ferritic stainless steel developed to combat standard pitting, crevice corrosion, and stress corrosion cracking (SCC) found in 300-series stainless steels. TorqBolt enforces strict compositional bounds across every production run.
| Grade / UNS | C (max) | Cr | Ni | Mo | N | Mn (max) | Si (max) | P (max) | S (max) | Min PREN* |
|---|---|---|---|---|---|---|---|---|---|---|
| UNS S31803 (Standard) | 0.030 | 21.0 - 23.0 | 4.50 - 6.50 | 2.50 - 3.50 | 0.08 - 0.20 | 2.00 | 1.00 | 0.030 | 0.020 | ≥ 31.0 |
| UNS S32205 (Restricted/TorqBolt) | 0.030 | 22.0 - 23.0 | 4.50 - 6.50 | 3.00 - 3.50 | 0.14 - 0.20 | 2.00 | 1.00 | 0.030 | 0.010 | ≥ 35.0 |
| EN 1.4462 (X2CrNiMoN22-5-3) | 0.030 | 21.0 - 23.0 | 4.50 - 6.50 | 2.50 - 3.50 | 0.10 - 0.22 | 2.00 | 1.00 | 0.035 | 0.015 | ≥ 32.5 |
| Mechanical Property | ASTM A479 / A276 Requirement | TorqBolt Production Standard | Significance in Bolted Joint Design |
|---|---|---|---|
| Tensile Strength, Rm (MPa / ksi) | ≥ 620 MPa (90 ksi) | 680 - 880 MPa (99 - 128 ksi) | High ultimate rupture resistance under hydrodynamic shocks |
| Yield Strength, Rp0.2 (MPa / ksi) | ≥ 450 MPa (65 ksi) | 480 - 580 MPa (70 - 84 ksi) | More than double 316L (220 MPa); enables fastener downsizing and weight reduction |
| Elongation, A5 (%) | ≥ 25 % | ≥ 28 % | Excellent structural ductility avoiding sudden brittle catastrophic shear |
| Impact Energy (Charpy V-Notch at -46°C) | Optional (Typically ≥ 40 J) | ≥ 80 J average (transverse) | Exceptional subsea arctic toughness; prevents low-temperature fracture |
| Hardness (Rockwell C / Brinell) | ≤ 28 HRC (271 HBW) | 24 - 28 HRC (250 - 271 HBW) | Mandatory compliance with NACE MR0175 for sulfide stress cracking (SSC) immunity |
| Austenite-Ferrite Balance (%) | 40% - 60% Ferrite | 45% - 55% Ferrite (ASTM E562) | Balanced microstructural dual-phase ensures optimal SCC and general corrosion ratio |
*PREN (Pitting Resistance Equivalent Number) = %Cr + 3.3(%Mo) + 16(%N). TorqBolt strictly enforces raw material selection ensuring a PREN value of 35 or higher for true marine reliability.
As global engineering projects transition toward extended 30-to-50-year design lives in harsher environments, the specification of Duplex 2205 bolting is undergoing massive structural shifts. Procurement directors and EPC leaders are navigating four key macro developments.
Because Duplex 2205 delivers over double the yield strength (450+ MPa) of standard austenitic stainless steels like AISI 316/316L (205–220 MPa), mechanical designers are actively downsizing joint diameters. In offshore floating production storage and offloading (FPSO) modules and subsea manifolds, switching from 316L or alloy steel to Duplex 2205 allows engineers to reduce bolt diameters (for instance, dropping from 1-1/2" bolts to 1-1/8" studs) while decreasing flange dimensions and overall topside weights by up to 35% without compromising safety margins.
Historically, the upfront price delta between duplex and standard austenitic hardware pushed buyers toward cheaper 316 fasteners. However, escalating offshore maintenance costs, downtime expenses exceeding $500,000 per day in deepwater assets, and premature joint failures caused by chloride-induced stress corrosion cracking (CSCC) have transformed procurement calculus. Duplex 2205 bolting yields negligible lifecycle replacement costs and zero stress-corrosion catastrophic risks under 100°C, proving exponentially cheaper over multi-decade lifecycles.
Mega-scale Sea Water Reverse Osmosis (SWRO) desalination facilities in the Middle East, North Africa, and Southern Europe are driving unprecedented surges in Duplex 2205 bolting consumption. High operating pressures (60 to 80 bar) paired with highly concentrated brine render 300-series stainless steel unusable. Simultaneously, the rapid scaling of offshore wind foundations and subsea substations requires long-term atmospheric splash-zone resistance where standard galvanizing fails within 5–10 years, cementing Duplex 2205 as the global structural standard.
The days of relying solely on generic mill test certificates are over. With digital supply chain auditing and automated AI quality gates, tier-1 EPC contractors mandate unassailable EN 10204 Type 3.1 or Type 3.2 documentation featuring raw melt provenance, Charpy V-notch impacts down to -46°C, ferrite micro-counting per ASTM E562, and non-destructive ASTM A923 intermetallic precipitation tests. TorqBolt’s comprehensive digital traceability protocols provide full audit compliance before fasteners ever dispatch.
Duplex stainless steels possess a tenacious chromium oxide passive film that, while providing phenomenal corrosion resistance, makes raw unlubricated threads susceptible to galling and cold welding during high-torque tightening. TorqBolt applies precision surface treatments engineered for optimal friction coefficients and long-term joint integrity.
We match each surface engineering technology to your operating media, installation torque specs, and operational temperature profiles.
Torque calculation for Duplex 2205 must account for higher bolt preloads compared to standard 316. To ensure zero field incidents during startup, TorqBolt technical service recommends:
Duplex stainless steels demand rigorous thermal and mechanical discipline. Improper hot forging or sub-optimal quench rates can induce devastating intermetallic phase precipitations (sigma phase σ, chi phase χ, and chromium nitrides Cr2N), causing brittle joint failures. TorqBolt’s integrated manufacturing route prevents these metallurgical anomalies.
Forging temperatures are strictly managed between 1150°C and 1000°C. Head forging is finished above 980°C to eliminate micro-cracking and grain boundary sensitization.
Every hot-worked batch undergoes full furnace solution annealing at 1040°C–1100°C followed by forced, rapid water quenching within seconds to freeze the ideal 50:50 phase matrix.
Threads up to M100 and 4" diameter are formed via cylindrical thread dies. Cold burnished thread roots provide unbroken grain flow and high compressive surface pre-stress.
Our in-house metallurgical testing checks micro-ferrite content per ASTM E562, Charpy impacts at -46°C, and intermetallic corrosion tests per ASTM A923 Method C.
100% XRF spectrometer alloy composition check
Hot or cold forming with controlled grain lines
1060°C soak + rapid water agitation quench
Cold working thread roots for fatigue strength
Ferrite volume & ASTM A923 phase test
Yield, tensile, elongation, impact at -46°C
EN 10204 3.1 or 3.2 third-party inspection
Duplex 2205 fasteners serve across critical industrial installations where high mechanical stresses converge with corrosive brine, wet H2S, or chlorinated chemical streams.
Subsea manifolds, risers, Christmas trees, topside piping, and high-pressure process flanges.
SWRO high-pressure booster pumps, membrane housings, piping headers, and brine recovery systems.
Sour service gas sweetening, hydrotreaters, heat exchangers, and distillation columns with wet H2S.
Propulsion shafts, rudder stocks, subsea hull fasteners, ballast piping, and offshore wind turbines.
Digesters, bleach washers, chlorine dioxide handling vessels, and liquor recovery piping systems.
Cargo tank hold-down bolts, chemical transport manifolds, valving hardware, and vent systems.
FGD scrubber towers, slurry pumps, dampeners, and ducting exposed to aggressive chloride condensates.
Turbine connections, reinjection wellhead bolting, and condensers exposed to hot corrosive steam.
To eliminate procurement revisions and ensure accurate engineering quotations, include these critical technical parameters with your RFQ submission.
Since 2010, TorqBolt Inc. has established an international reputation as a leading manufacturer of specialty, corrosion-resistant, and high-temperature alloy fasteners. Headquartered in Mumbai with advanced production and forging operations in Rajkot, India, TorqBolt delivers fully documented, PED-certified fastening systems to over 40 countries across Europe, the Americas, the Middle East, and Asia-Pacific.