X2CrNiMnMoNbN25-18-5-4 Forgings, 1.4565 / Alloy 24 / UNS S34565
Forged rings, seamless rolled rings, flanges, shafts, discs, sleeves, tube sheets and bars, open-die forged to drawing by Jiangyin Jiangnan Metal Co., Ltd.
X2CrNiMnMoNbN25-18-5-4 is the SEW 400 name of a nitrogen and molybdenum alloyed super-austenitic stainless steel, carried elsewhere as material number 1.4565, as Alloy 24 and as UNS S34565. The structure is fully austenitic, stabilised with a small niobium addition. Proof strength is roughly double that of 316L, and resistance to pitting, crevice attack and chloride stress corrosion cracking sits in the 6Mo class. Normal duty is seawater systems, flue-gas desulphurisation, desalination and chloride-bearing chemical plant.
Jiangyin Jiangnan Metal forges this grade to drawing at Jiangyin, Jiangsu, China. Enquiries to sales@steelforgepieces.com or +86 189 2135 9659.
Designations and standards
The grade runs under several names, and that is where most ordering mistakes start. SEW 400 calls it X2CrNiMnMoNbN25-18-5-4 and ties it to material number 1.4565 and UNS S34565. EN 10088 lists the same material number as X2CrNiMnMoN25-18-6-5, with a higher manganese band and no niobium in the name. State the governing document on the purchase order and we certify against that document.
| System | Designation | Scope |
|---|---|---|
| SEW 400 (Germany) | X2CrNiMnMoNbN25-18-5-4 | Stainless steels for rolled and forged products |
| Werkstoff number | 1.4565 | European material number |
| EN 10088-1 / -2 / -3 | X2CrNiMnMoN25-18-6-5 (1.4565) | Plate, strip, bar, rod, sections |
| UNS (USA) | S34565 | Plate, bar, forgings |
| Trade names | Alloy 24, 4565 S, P512 | Mill brand designations |
| Pressure approval | VdTÜV 509 | Pressure duty, about −196 °C to 400 °C |
Chemical composition
The analysis below is the SEW 400 specification. Balance iron. The EN 10088 version of 1.4565 is published with Mn 5.00 to 7.00 % and Cr 24.0 to 26.0 %, so a heat can satisfy one document and fall outside the other. Check which one your inspector will audit against.
| C | Si | Mn | P | S | Cr | Ni | Mo | N | Nb | Fe |
|---|---|---|---|---|---|---|---|---|---|---|
| ≤ 0.030 | ≤ 1.00 | 3.50–6.50 | ≤ 0.030 | ≤ 0.015 | 23.0–26.0 | 16.0–19.0 | 3.50–5.00 | 0.30–0.60 | ≤ 0.15 | Balance |
Copper is not an alloying element in this grade. Pitting and crevice resistance come from the chromium, molybdenum and nitrogen combination. Where sulphuric acid service calls for copper, the grades to look at are Alloy 31, Alloy 825 or Alloy 926, all of which we also forge.
Pitting resistance equivalent
PREN for nitrogen-bearing austenitics is normally taken as %Cr + 3.3 x %Mo + 16 x %N. Chromium, molybdenum and nitrogen all sit in wide bands here, so the figure that counts is the one worked out from the ladle analysis on your certificate, not a catalogue number. Every certificate we issue shows the full heat analysis.
Mechanical properties
Values apply to the solution-annealed condition at room temperature. Section size, test direction and sampling position all move the result on heavy forgings, so acceptance values belong in the order, not in a datasheet.
| Property | Value |
|---|---|
| 0.2 % proof strength Rp0.2 | ≥ 420 MPa |
| Tensile strength Rm | 800–950 MPa |
| Elongation A5 | ≥ 35 % longitudinal, 30 % transverse reported |
| Impact energy ISO-V at +20 °C | about 120–130 J longitudinal, 90 J transverse |
| Hardness | ≤ 230 HB |
| Modulus of elasticity | about 190 kN/mm² |
| Temperature | 100 °C | 200 °C | 300 °C | 400 °C | 500 °C |
|---|---|---|---|---|---|
| Rp0.2 min, MPa | 350 | 270 | 240 | 210 | 210 |
Physical properties
| Density | Specific heat | Thermal conductivity | Electrical resistivity | Magnetic behaviour |
|---|---|---|---|---|
| 8.0 g/cm³ | 450 J/kg·K | 12 W/m·K | 0.92 Ω·mm²/m | Non-magnetic, fully austenitic |
Forging and heat treatment
Forging runs from about 1150 °C down to a finish temperature near 950 °C, cooled in air, then solution annealed at 1170 to 1120 °C and water quenched. High nitrogen and manganese make the steel stiffer under the hammer than 316L and the working window is narrow, so we plan reheats rather than push one heat too far. Finishing below the stated range risks precipitation that costs corrosion performance, which is the usual reason a part passes tensile testing and still fails a corrosion test.
Melting routes are AOD or VOD refining, or vacuum induction melting, with electroslag or vacuum arc remelting where cleanliness and segregation control are specified. We quote either route. For thick-section seawater and FGD parts the remelted route usually earns its price difference.
Corrosion behaviour
Alloy 24 resists localised corrosion, meaning pitting and crevice attack, and holds up against chloride stress corrosion cracking. Carbon capped at 0.03 % plus the niobium addition keeps intergranular corrosion in check. It is used in seawater and in a range of acids and alkalis, and is sold as an alternative to duplex grades, Alloy 31 and some nickel alloys. Treat it as a wet-corrosion material to roughly 400 °C. It is not a heat-resisting grade; for furnace and high-temperature oxidising duty the usual choice is a Cr-Ni-Si steel such as X15CrNiSi20-12 (1.4828).
Typical applications
Seawater and marine systems
Forged pump casings and shafts, gate valve bodies and stems for seawater ballast systems, flanges and tube sheets for seawater-cooled exchangers.
Flue-gas desulphurisation
Seamless rolled rings, shafts and nozzles for FGD plant in power stations and on large sea-going vessels, where chloride-rich condensate eats lesser grades.
Desalination
Forged discs, sleeves, bushings and tube sheets for desalination trains and high-chloride brine handling.
Chemical and petrochemical
Valve bodies, seat rings, valve blocks, reactor and mixer parts, process piping forgings, acid cleaning and pickling equipment.
Pulp, paper and bleaching
Rings, spindles, rolls and bars for bleaching plant and chloride-bearing process liquors.
Food, pharmaceutical, heat exchangers
Flanges, manifolds and exchanger parts where cleanability and chloride resistance are both required.
Product forms and testing
We supply this grade as open-die forgings and seamless rolled rings: forged rings, rolled rings, flanges, round bars, discs, shafts and stepped shafts, eccentric shafts, crankshafts, sleeves, bushings, tube sheets, forged tubes and pipes, nozzles, blocks, gear blanks and parts machined to drawing. Sizes follow your drawing; we hold no fixed size list in this grade.
Ultrasonic testing is done to EN 10228-3, SEP 1921 or ASTM A388 at the acceptance class you nominate. Certificates are issued to EN 10204 3.1, or 3.2 with a third-party inspectorate such as BV, SGS, TUV, DNV or Lloyd's. Intergranular corrosion testing, permeability measurement, PMI, elevated-temperature tensiles and low-temperature impact testing can be added to the inspection and test plan.
Questions buyers ask
What is X2CrNiMnMoNbN25-18-5-4 equivalent to?
W.Nr. 1.4565, UNS S34565 and Alloy 24. EN 10088 lists the same material number as X2CrNiMnMoN25-18-6-5 with a different manganese and chromium band, so name the standard on the order instead of assuming the two are interchangeable on paper.
Is the grade magnetic?
No. The structure is fully austenitic and solution-annealed material is non-magnetic in service. Heavy cold work lifts permeability a little. If a maximum permeability value matters, write it into the order as a test.
Does it contain copper for sulphuric acid duty?
No. Copper is not specified in this grade, and its corrosion performance rests on chromium, molybdenum and nitrogen. For copper-bearing acid service, look at Alloy 31, Alloy 825 or Alloy 926.
How is it welded?
Weldability is good. A nickel-base filler is normally used to control dilution and keep corrosion resistance in the weld metal; filler 2.4609 is one published recommendation for 1.4565. Procedures should be qualified for the joint and thickness in hand.
What is the largest piece you can forge?
Geometry decides that, not a single weight limit. Send the drawing, or the ring dimensions as OD, ID and height, and we confirm feasibility, forged weight and lead time against press and ring-mill capacity before quoting.
How do I get a price?
Email the drawing or dimensions with quantity, governing standard, heat-treatment condition, NDT class and certificate level to sales@steelforgepieces.com, or call +86 189 2135 9659. Quotations normally go back within one working day.
Request a quotation
Send the drawing or finished dimensions of the X2CrNiMnMoNbN25-18-5-4 part you need, ring, flange, shaft, disc, sleeve, tube sheet or bar, with quantity, standard and certificate requirement. We quote price, forged weight and delivery.
Related grades we forge
Buyers comparing this grade also price Nitronic 50, Alloy 31, Incoloy 926, Incoloy 825, Alloy 59 and Hastelloy C-276 for chloride and acid duty. All are available as open-die forgings from the same works.
Data on this page is taken from published European mill and stockist datasheets for 1.4565 / Alloy 24 / UNS S34565 and from the SEW 400 listing for X2CrNiMnMoNbN25-18-5-4. It is given for guidance and is not a warranty of properties. Contractual values are the ones stated on the order and on the EN 10204 certificate supplied with the goods. Reviewed October 2026.