2205 Duplex Stainless Steel Forgings UNS S31803 and S32205 · ASTM A182 F51 and F60 · EN 1.4462

Buyers reach this alloy under at least six names. They describe one material family, and the differences lie in specification range and product form rather than in the alloy itself. SAF 2205 is a trademark held by Alleima, formerly Sandvik Materials Technology. Where a drawing calls for SAF 2205, the material supplied is the equivalent UNS S31803 or S32205 chemistry, certified to whichever ASTM or EN specification the order names.

S31803 or S32205, which to order

When duplex steels were first standardised, the specification was written as S31803. Several mills consistently produced toward the upper end of that range to maximise corrosion performance, helped by refining practice that allowed nitrogen to be added deliberately instead of being left as a background element. The gap between bottom of range and top of range material can amount to several PREN points, and S32205 was introduced to capture the top of range material. S32205 fully meets S31803, so F60 material can be dual certified as F51, while S31803 material cannot be certified as S32205. Unless a project specification states otherwise, ordering to S32205 chemistry with an F51 dual certificate costs nothing in flexibility.

The three highlighted values are where S32205 is tighter than S31803, and they are the three elements that drive PREN. Melting is carried out in our own steel plant by EAF with ladle furnace and VOD refining, with ESR remelting available where the order or the specification calls for it.

Separately solution annealed and quenched test pieces normally return 0.2 percent proof strength at or above 450 MPa, 1.0 percent proof strength at or above 500 MPa, tensile strength between 660 and 860 MPa and hardness no higher than 270 HBW, which sits clear of the A182 minima. Heavy forged sections are judged on prolongation test pieces cut to represent the actual section, not on thin section published data.

The expansion coefficient sits closer to carbon steel than to austenitic stainless steel. That matters in tube sheets, heat exchangers and bolted joints where duplex components mate with carbon steel, because differential growth in service and residual stress after welding are both lower than with an austenitic equivalent.

Pitting and crevice corrosion

The critical pitting temperature of 2205 falls in the region of 35 °C, and crevice corrosion resistance is well ahead of the 316L types. Where the duty calls for a PREN above 40, such as hot seawater or higher chloride concentrations, the next step up is A182 F53, super duplex S32750 or A182 F55, super duplex S32760.

Stress corrosion cracking

Austenitic grades of the 304L and 316L type become susceptible to chloride stress corrosion cracking above roughly 60 °C. Duplex grades are far less prone to it, and 2205 resists chloride stress corrosion cracking to around 150 °C. This is the most common single reason for replacing 316L with 2205 in brackish water and chloride bearing process duty.

Intergranular attack, erosion and fatigue

The composition is balanced so that austenite reforms quickly in the weld heat affected zone, which keeps corrosion resistance and toughness there close to those of the parent metal, and welded joints pass ASTM A262 Practice E testing. The combination of hardness and corrosion resistance also gives good erosion corrosion behaviour in sand bearing or high velocity media. In rotary bending fatigue in 3 percent sodium chloride at 40 °C, unnotched 2205 withstood 430 MPa against 260 MPa for 316L at 2 × 10⁷ cycles, which is a practical argument for duplex in rotating shafts handling corrosive fluids.

Sour service

In accordance with NACE MR0175, solution annealed and cold worked UNS S31803 is accepted up to 232 °C, 450 °F, provided the hydrogen sulphide partial pressure does not exceed 0.02 bar, 0.3 psi, proof strength is not above 1100 MPa and hardness is not above 36 HRC. Project specifications frequently impose tighter hardness caps than this. Confirm the governing edition of NACE MR0175 or ISO 15156 with the enquiry and certificates are issued against it.

Quench rate decides the result on heavy sections. Duplex 2205 tolerates slow cooling from the annealing temperature poorly, because intermetallic phases precipitate and both toughness and corrosion resistance fall away. Charge size is therefore set by quench tank capacity rather than by furnace capacity, and any section thickness beyond what can be quenched reliably is raised at quotation stage rather than after forging.

For machining, speed should carry the reduction while feeds are cut only slightly and with care. Rigid setups, sharp coated carbide tooling and positive, uninterrupted cuts matter more with duplex than with austenitic grades because of the work hardening tendency.

Chloride and hydrogen sulphide resistance put 2205 into refinery service and into process solutions contaminated with chlorides. It suits heat exchangers cooled with brackish or chloride bearing water particularly well, and it handles dilute sulphuric acid and organic acids such as acetic acid and acid mixtures. Its strength makes it a substitute for austenitic steels in heavily loaded structures, which is usually where the life cycle cost case is won.

Forgings in this grade ship into oil and gas work, covering wellhead and christmas tree components, subsea and deepwater production hardware, downhole parts for moderately corrosive sour gas wells and manifolds. In chemical and petrochemical plant they go into flanges, valves, fittings, couplings, reactor parts and crystalliser components. Marine and desalination users take seawater piping parts, pump and compressor components and shipbuilding items. Pulp and paper mills use them in digesters, liquor tanks, paper machine rolls and shafts. Power generation orders cover turbine and gear components, generator and nitrogen generator parts and industrial air compressors. Heat transfer equipment accounts for tube sheets, separator internals and exchanger shells.

Each order is forged under a traceable heat number and released against an EN 10204 3.1 certificate, or EN 10204 3.2 with third party witness. The works holds approvals from CCS, BV, DNV, LR and NK, and accepts inspection by the buyer or a nominated independent inspector.

Ultrasonic examination follows EN 10228-3, SEP 1921 or ASTM A388 at the acceptance class named on the order. Available on request: ferrite content by metallographic count or Feritscope, intermetallic phase screening to ASTM A923, pitting corrosion testing to ASTM G48 Method A, positive material identification, low temperature Charpy sets, hardness mapping against sour service hardness caps, and compliance statements to NACE MR0175 or ISO 15156.

Is SAF 2205 the same as UNS S31803 and S32205?

SAF 2205 is a trademark held by Alleima, formerly Sandvik Materials Technology, for a 22 percent chromium duplex ferritic-austenitic stainless steel. The generic equivalents are UNS S31803 and the tighter UNS S32205, along with EN 1.4462, X2CrNiMoN22-5-3 and JIS SUS 329J3L. S32205 can be dual certified as S31803, but not the other way round.

What is the difference between A182 F51 and A182 F60?

F51 is the A182 forging grade for S31803 and F60 is the grade for S32205. Same alloy family, different compositional range. F60 carries higher minimum chromium, molybdenum and nitrogen, so its guaranteed PREN is higher. The mechanical minima are identical at 620 MPa tensile, 450 MPa yield and 25 percent elongation.

How much stronger is 2205 than 316L?

Roughly twice the yield strength. 2205 guarantees 450 MPa minimum 0.2 percent proof stress in the solution annealed condition, which often allows a thinner section. That is part of why duplex can win on installed cost even at a higher price per kilogram.

Can 2205 duplex be used above 300 °C?

No. Prolonged exposure above about 280 to 300 °C precipitates brittle micro-constituents and degrades impact strength, and below about −50 °C the material passes through a ductile to brittle transition. Design inside that window, or move to an austenitic grade or a nickel alloy. Embrittlement caused by service exposure can sometimes be reversed by a full solution anneal.

Does 2205 need post-weld heat treatment?

Preheat and post-weld heat treatment are normally unnecessary. Use ER2209 or E2209 consumables, keep heat input between 0.5 and 2.5 kJ/mm and interpass temperature below 150 °C. Avoid autogenous welding without filler, since it leaves excess ferrite. Adding nitrogen to the shielding gas helps austenite reform in the weld metal.

What information is needed for a quotation?

A drawing or outline dimensions, quantity, the specification to be certified against, heat treatment condition, NDT requirements and acceptance class, and any supplementary testing such as Charpy temperature, ASTM A923 or ASTM G48. Lead time depends on section size, whether suitable billet is already melted and the extent of third party inspection, and it is confirmed together with the price.

Related grades we forge

• A182 F53, super duplex S32750
• A182 F55, super duplex S32760
• A182 F61
• A182 F44, S31254
• 904L
• Sanicro 28
• Incoloy 825
• Inconel 625

Reference documents for the data on this page: ASTM A182 / A182M grades F51 and F60, ASTM A479, EN 10088-3 for the 1.4462 designation, published mill data for the 22Cr duplex grade, and NACE MR0175 for sour service limits. Figures are given for guidance. The governing document is always the specification named on the purchase order.

Request a quotation for 2205 duplex forgings

Send a drawing, or simply the outline dimensions, quantity, specification and test requirements. You receive price, lead time and the proposed forging and heat treatment route.

Jiangyin Jiangnan Metal Co., Ltd., open-die forging works
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Telephone +86 189 2135 9659
Email sales@steelforgepieces.com