1.4410 super duplex forgings X2CrNiMoN25-7-4 / UNS S32750 / ASTM A182 F53 / 2507. Forged to drawing in Jiangyin, China.

Description and selection

1.4410 is the European material number for X2CrNiMoN25-7-4, an austenitic-ferritic (duplex) stainless steel listed in EN 10088-1. Its chromium, molybdenum and nitrogen contents give a pitting resistance equivalent number above 40, which places it in the super duplex class rather than the standard duplex class of 1.4462 (2205).

Two conditions usually decide the grade. The first is warm chloride service: seawater, produced water, brine and bleach-bearing process streams, where 316L and often 2205 suffer pitting or crevice attack. The second is strength. A minimum proof strength of 530 MPa is about double the value for an austenitic 316L, so flanges, valve bodies and pressure parts can be made in lighter and thinner sections for the same duty.

1.4410 is not a high-temperature grade. Duplex structures embrittle above and below the service window. Continuous service is therefore normally limited to about 300 °C, and the grade is not used below about −50 °C. The temperature diagram further down shows the safe ranges and the ranges that must be avoided.

Equivalent grades and cross-references

1.4410, S32750, F53 and 2507 all describe the same 25Cr-7Ni-4Mo-N alloy. They are not interchangeable as specifications, because each standard sets its own composition window, testing and acceptance limits. A mill or forge quoting one designation can normally certify to the others.

Cross-references are nominal. Where a project specification names one standard, forgings should be melted, heat treated, tested and certified to that standard.

The closest commercial alternative is 1.4501 / S32760 (F55, Zeron 100), which contains copper and tungsten. The ASTM version of this page is A182-F53 forgings. The standard duplex grade one class below is A182-F51 (2205 / 1.4462).

Chemical composition

Buyers normally cite either EN 10088-3 (as 1.4410) or ASTM A182 (as F53). The two differ in three places. ASTM caps manganese and silicon more tightly, allows molybdenum up to 5.0 %, and limits copper. EN allows nitrogen up to 0.35 %.

Nominal composition: 25 Cr, 7 Ni, 4 Mo, 0.28 N. ASME assigns F53 to P-No. 10H.

Mechanical properties

The values below are the specified minima in the solution annealed and quenched condition. Production forgings normally test above them, but acceptance is against the specification rather than against typical values.

The lower requirement for heavy sections allows for slower quenching through the core. It is the main reason to declare the true section thickness when ordering heavy open-die forgings.

Impact toughness

Charpy V-notch testing is not a base requirement of A182 for F53, but offshore and subsea purchase specifications almost always add it. Testing at −46 °C is the usual requirement, with acceptance stated as a minimum average of 45 J over three specimens and no single value below 35 J. State the test temperature, specimen orientation and acceptance values in the enquiry, because they affect the forging and quenching route.

Physical properties

Duplex steels sit between ferritic and austenitic grades in physical behaviour. Thermal conductivity is higher and thermal expansion lower than 316L, so duplex weldments distort less. This is useful on large fabricated assemblies.

The ferrite phase makes 1.4410 magnetic. A magnet sticking to a duplex forging is normal and is not evidence of contamination or of the wrong grade.

Corrosion resistance and PREN

The pitting resistance equivalent number is the standard first check for chloride pitting:

PREN = %Cr + 3.3 × %Mo + 16 × %N

At the nominal composition of 25 Cr, 4.0 Mo and 0.28 N this gives 25.0 + 13.2 + 4.48 = 42.7. The super duplex class is conventionally defined as PREN of at least 40, and mills supplying offshore work normally target 41 to 43. PREN is calculated from composition, so the value for a particular heat can be taken from the mill certificate. Ask for it where the project sets a minimum.

Corrosion performance

• Pitting and crevice corrosion. Suitable for warm, aerated seawater, where 316L (PREN about 24) and 2205 (PREN about 35) are at risk. The critical pitting temperature is well above that of the austenitic grades.
• Chloride stress corrosion cracking. The ferrite phase blocks crack propagation, giving far better resistance than 304 or 316 in hot chloride.
• Acids. Good resistance to dilute sulphuric and organic acids and to caustic. Better than 904L in sulphuric acid contaminated with chlorides.
• Erosion and cavitation. The hardness and strength suit pump and valve internals in sand-bearing produced water.

Corrosion performance depends on microstructure as well as on chemistry. Intermetallic phases formed during slow cooling reduce pitting resistance in material that still passes the composition check. The heat treatment and quench route described below therefore matters as much as the ladle analysis.

Forging and heat treatment

Super duplex has a narrow hot-working window and two temperature ranges that must not be held. The manufacturing route follows from this.

Forging practice

• Soak the ingot or billet uniformly. Minimum soaking temperature is about 1050 °C, so that the core reaches working temperature before the surface overheats.
• Work between 1230 °C and 1025 °C. Above roughly 1230 °C the ferrite fraction rises sharply and hot ductility falls. Below about 1000 °C the alloy work-hardens and cracks.
• Reheat rather than continue working. Duplex has low hot strength and a narrow window, so heavy open-die work is taken in several heats.
• Do not air cool from forging heat. Every forging is solution annealed after the last blow.

Solution annealing and quench

Heat to 1040 to 1120 °C, hold until the section has equalised, then water quench. ASTM A182 requires solution treatment at not less than 1025 °C followed by liquid quenching, with cooling below 260 °C. Heavy sections have to reach the quench tank without delay. In practice this is what limits the maximum section a forge can certify to super duplex acceptance criteria.

Machining and cold work

1.4410 is difficult to machine. Compared with 316/316L, cutting speeds have to be reduced by roughly half with coated carbide tooling, while feeds are reduced only slightly. Light feeds cause work-hardening and rubbing. Rigid setups, sharp cutting edges and generous coolant are necessary. Severe or complex cold forming calls for an intermediate solution anneal, and duplex grades need a more generous bend radius than austenitic grades. After heat treatment, pickling and passivation restore the surface oxide and the full corrosion resistance.

Comparison with 2205, 2760, 904L and 316L

The usual question is whether the step up from 2205 is justified. The table sets out the figures that decide it.

Rp0.2 values are EN 10088-3 minima for solution annealed product. PREN is calculated from nominal composition. The figure for 1.4501 uses the tungsten-modified formula.

Selection notes

• Moving from 2205 to 1.4410 is normal where chlorides exceed roughly 1 000 ppm above 40 °C, where the duty is seawater or produced water, where NACE or ISO 15156 service requires PREN above 40, or where strength governs section size.
• 1.4410 or 1.4501. Mechanically and in most chloride media the two are equivalent. The copper and tungsten in 1.4501 are preferred by some specifications for acid-bearing and severe seawater service. In practice the project specification or the approved vendor list decides, not the metallurgy.
• 904L or a nickel alloy remains the better choice where service is above 300 °C, below −50 °C, or dominated by strong reducing acids rather than by chlorides. Duplex grades are not suited to those conditions.

1.4410 forgings produced

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory. Parts are made to customer drawing or specification rather than from a catalogue. The forms below are produced in 1.4410.

Dimensions, single-piece weight and delivery condition (black forged, rough machined or finish machined) are quoted against your drawing. Send the drawing, the governing specification and the required testing with the enquiry.

Related pages: forged products overview, forged valve stems and valve parts, and the full stainless steel grade index.

Melting, testing and certification

Super duplex is sensitive to the process route, so the route is set out here rather than left implied.

Melting

Material is melted by EAF plus VOD, with ESR remelting available where the specification or the section size calls for it. Nitrogen control at the melt stage matters more in this grade than in most stainless steels. Nitrogen is both a strengthening element and, at 16 times its weight fraction, the largest single term in PREN.

Non-destructive and destructive testing

• Ultrasonic examination to EN 10228-4, SEP 1921 or ASTM A388, to the acceptance class stated in your order. EN 10228-4 is the part written for austenitic and austenitic-ferritic stainless forgings. EN 10228-3 covers ferritic and martensitic steels and does not apply to 1.4410.
• Liquid penetrant examination of machined surfaces where specified.
• Tensile and hardness testing on test material representing the heat and the heat-treatment lot.
• Charpy V-notch impact testing, commonly at −46 °C for offshore and subsea work.
• Ferrite content by metallographic point count to ASTM E562. Purchase specifications commonly require 35 to 55 % ferrite for forgings.
• Detrimental intermetallic phase detection to ASTM A923, using Method A metallographic screening, Method B impact testing or Method C ferric chloride corrosion testing.
• Pitting corrosion testing to ASTM G48 Method A, commonly specified at 50 °C for 24 h with no pitting at 20x magnification and weight loss within the project limit.
• Positive material identification on finished parts where required.

Documentation

Forgings are supplied with an inspection certificate to EN 10204 Type 3.1, or Type 3.2 countersigned by a third-party inspection body such as BV, SGS, TUV, DNV or Lloyd's Register where your order requires it. Certificates report the heat analysis, mechanical results, heat-treatment records and the non-destructive and corrosion testing called for by the order. Ask for the calculated PREN of the heat to be printed on the certificate where the project sets a minimum.

Applications

• Offshore oil and gas. Wellhead and christmas-tree components, manifold blocks, subsea housings, riser and flowline flanges, produced-water and seawater-injection piping parts.
• Valves and pumps. Bodies, bonnets, seat rings, stems, discs and shafts for ball, gate, globe, check and plug valves in chloride duty.
• Desalination. High-pressure pump parts, energy-recovery components, reverse osmosis piping and vessel forgings in concentrated brine.
• Chemical and petrochemical plant. Heat-exchanger tube sheets, pressure-vessel nozzles, agitator shafts, chemical tanker cargo system parts.
• Pulp and paper. Digester and liquor-tank components, bleach-plant equipment.
• Power and flue-gas desulphurisation. Absorber internals, cooling-water and service-water systems.
• Marine and structural. Propeller and pump shafts, tie bars, seawater fire-fighting and ballast systems.

Frequently asked questions

Supplier and contact

Related grades

• A182-F53
• A182-F55 / 1.4501
• A182-F51 / 2205
• A182-F44 / 254 SMO
• A182-F61
• 904L
• Sanicro 28
• Alloy 24
• 17-4PH
• Inconel 625

Technical data on this page is compiled from EN 10088-1, EN 10088-3, EN 10250-4, EN 10222-5 and ASTM A182/A182M, together with published mill datasheets for UNS S32750. Values are given for guidance. The governing specification named in your purchase order takes precedence. Page last reviewed 22 September 2026 by Jiangyin Jiangnan Metal Co., Ltd.