Duplex Steel UNS S31803 Round Bar

Duplex stainless steel has a two-phase microstructure of roughly equal parts ferrite and austenite. That balanced structure delivers the signature duplex combination of high strength and high corrosion resistance, a pairing that neither fully austenitic grades like 316 nor fully ferritic steels can match.

UNS S31803 is the original specification for 22% chromium duplex, universally called Duplex 2205 and designated F51 under ASTM A182. A ASTM A276 UNS S31803 round bar is a solid length of this alloy produced by hot rolling, forging, or cold finishing, used as machining stock for shafts, valve and pump components, fasteners, and fabrications operating in aggressive chloride environments.

The performance of the F51 round bar comes from its chemistry: about 22% chromium and 3% molybdenum for pitting resistance, 5% nickel for toughness, and controlled nitrogen that stabilises the austenite phase and boosts strength. The result is a Duplex Steel UNS S31803 bar with a minimum yield strength of 450 MPa, comparable to many carbon steels but with the corrosion resistance of a high-alloy stainless.

S31803 is the original 2205 specification, with a broader allowable composition range. S32205 is the modern, tightened version that mandates a higher minimum nitrogen (0.14 to 0.20%) and slightly narrower chromium and molybdenum bands, which improves weldability and corrosion consistency.

In practice most mills now produce material that meets both S31803 and S32205 at once, that is, dual-certified 2205 bar. Jade Alloys supplies dual-certified stock wherever possible, so a single heat covers whichever call-out your drawing carries. If your project specifically references S32205, see our Duplex UNS S32205 Round Bar page.

The table below gives the ASTM A276 composition limits for UNS S31803 (DIN 1.4462).

The low carbon (0.030% max) resists sensitization during welding, while the balanced chromium, molybdenum, and nitrogen chemistry produces the ferrite-austenite structure that defines the Duplex Steel UNS S31803 bar.

Typical minimums for solution-annealed S31803 round bar and F51 rod per ASTM A276 / A479.

The near-doubling of yield strength versus 316 lets designers reduce section thickness and weight, a major advantage for pressure vessels, subsea hardware, and structural components.

Both S31803 (F51) and the modern S32205 (F60) share the same Werkstoff number 1.4462 and the 2205 trade name. The difference lies in the tighter nitrogen and composition control of S32205.

We hold ready stock across every common form and finish. If your enquiry references a spec, UNS number, or Werkstoff number rather than a plain trade name, this list confirms we cover it.

Whether you need us as a Duplex UNS S31803 round bar manufacturer, a DIN 1.4462 bright bar supplier, or an ASTM A276 F51 hex bar exporter, a single enquiry covers stock, cutting, and certification.

We supply S31803 round bar across metric, imperial, and Japanese size systems.

Standard mill lengths run 1 to 6 metres, with cut to length available to reduce machining waste and freight cost on export orders.

DIN 1.4462 Flat Bar Sizes

ASME SB276 F51 Square Bar Weight Chart

Duplex UNS S31803 hexagon bar weights across flats.

Representative S31803 hollow bar stock (OD = outside diameter, ID = inside diameter). Full range spans 32 mm OD up to 275 mm OD.

Theoretical weights for solid S31803 round bar at a density of about 7.8 g/cm3. For any size not listed, use our metal weight calculator.

Indicative weights; confirm against certified material for billing

Surface Finish Codes

Supply Condition

We supply to ISO h-band and k-band tolerances to suit machining and slip-fit requirements.

Common ISO bands supplied: h8, h9, h10, h11, h12, h13, k9, k10, k11, k12. State the band on your enquiry and we will confirm feasibility for the chosen diameter and finish.

• Oil & gas: wellhead components, valve stems, pump shafts, subsea manifolds, and downhole tooling in sour and chloride service.
• Desalination and seawater: pump and valve internals, shafts, and fasteners in reverse-osmosis and MSF plants.
• Chemical and petrochemical: agitator shafts, reactor internals, and fasteners exposed to acids and chlorides.
• Marine and offshore: propeller shafts, rudders, deck hardware, and structural pins in splash-zone service.
• Pulp and paper: digester and bleaching-plant components resistant to chloride attack.
• Pressure vessels and structural: high-strength, corrosion-resistant components where reduced section weight matters.

Every UNS S31803 round bar is verified through destructive and non-destructive testing:

• Tensile, elongation, and reduction-of-area testing
• Chemical composition analysis
• Ferrite content verification for correct phase balance
• Pitting corrosion test (ASTM G48)
• Positive Material Identification (PMI)
• Eddy current test
• Radiographic and ultrasonic examination on request

Every consignment of S31803 round bar ships with:

• EN 10204 3.1 mill test certificates traceable to the heat number
• Chemical composition and mechanical test reports
• Ferrite content verification, critical for duplex phase balance
• PMI (Positive Material Identification) on request
• NACE MR0175 / ISO 15156 compliance statements for sour service
• Third-party inspection by Lloyd’s, BV, SGS, DNV, or TUV on request
• Testing through NABL-approved laboratories

Correct phase balance (typically 40 to 60% ferrite) and solution-anneal condition are essential to duplex performance, and our documentation confirms both. Explore our quality policy and certificates for more.

As a government-recognised export house, Jade Alloys ships Duplex UNS S31803 round bars worldwide with EN 10204 3.1 documentation, Certificate of Origin, and ISPM 15-compliant packing.