Super austenitic stainless steel, 6 % molybdenum
X1NiCrMoCuN25-20-7
Open-die forgings: seamless rolled rings, flanges, bars, discs, shafts and tube sheets
- EN 1.4529
- UNS N08926
- Alloy 926
- 25-6Mo
- 1925 hMo
- Incoloy 926
X1NiCrMoCuN25-20-7 is the EN designation for material number 1.4529, a 6 % molybdenum super austenitic stainless steel. It contains about 25 % nickel, 20 % chromium, 6 to 7 % molybdenum, 0.5 to 1.5 % copper and 0.15 to 0.25 % nitrogen, with carbon capped at 0.020 %. The alloy is identical to UNS N08926 and is traded as Alloy 926, 25-6Mo, 1925 hMo and Incoloy 926. Its pitting resistance equivalent number (PREN) is typically 43 to 47, above 904L and level with or ahead of 254 SMO and superduplex 2507.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China. We forge X1NiCrMoCuN25-20-7 to customer drawing as seamless rolled rings, flanges, round bars, discs, shafts, sleeves, bushings, tube sheets, nozzles and valve blanks. Material is melted by EAF plus AOD or VOD with optional ESR remelting, forged, solution annealed at 1150 to 1180 °C with a rapid quench, ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388, and released with an EN 10204 3.1 or 3.2 certificate.
For a quotation, send a drawing or dimensions to sales@steelforgepieces.com or call +86 189 2135 9659.
Designation, equivalents and governing standards
The same alloy is bought under six different names. Check which one your specification means before you place the order.
The grade is a super austenitic stainless steel. Iron is the balance, and EN 10088-1 lists it among the stainless steels. Because nickel sits near 25 %, it also falls inside the ASTM nickel, iron and chromium alloy specifications. North American buyers order it as UNS N08926 under ASTM B564 or B649, while European buyers order the identical material as 1.4529 under EN 10088-3. We supply to either route.
| System | Designation | Notes |
|---|---|---|
| EN name | X1NiCrMoCuN25-20-7 | Per EN 10088-1 |
| EN material number | 1.4529 | Werkstoffnummer |
| UNS | N08926 | Used in the ASTM B-series specifications |
| Trade names | Alloy 926, 25-6Mo, 1925 hMo, Incoloy 926, UR 926 | Producer brands of the same composition |
| Older DIN designation | X1NiCrMoCuN25-20-6 | Earlier form of the same material number |
| Product form | European | American |
|---|---|---|
| Designation and composition | EN 10088-1 | ASTM B564, B625, B649 |
| Bar and rod | EN 10088-3 | ASTM B649 |
| Forgings | EN 10222-5 (pressure purposes) | ASTM B564 |
| Plate, sheet, strip | EN 10088-2 | ASTM B625 |
| Seamless pipe and tube | EN 10216-5 | ASTM B677 |
| Welded pipe and tube | EN 10217-7 | ASTM B673, B674 |
| Sour service | NACE MR0175 / ISO 15156-3, qualification on request | |
| Pressure equipment | AD 2000-Merkblatt W2, VdTUV 502, PED 2014/68/EU 4.3 available | |
| Certification | EN 10204 3.1 standard, 3.2 with third-party witness | |
EN 10095 covers heat-resisting steels and does not apply to this grade. Where a specification quotes EN 10095 for 1.4529, ask the buyer to confirm before we release material.
Chemical composition
Molybdenum at 6 to 7 % and nitrogen at 0.15 to 0.25 % give the alloy its pitting and crevice resistance. Copper at 0.5 to 1.5 % is the main difference between 1.4529 and 254 SMO and improves behaviour in sulphuric and phosphoric acid. Carbon is held to 0.020 % maximum so that chromium carbides do not form at grain boundaries during cooling from the forging heat.
| C | Cr | Ni | Mo | Cu | N | Mn | Si | P | S | Fe |
|---|---|---|---|---|---|---|---|---|---|---|
| 0.020 max | 19.0–21.0 | 24.0–26.0 | 6.0–7.0 | 0.5–1.5 | 0.15–0.25 | 2.00 max | 0.50 max | 0.030 max | 0.010 max | Balance |
Composition limits published by Jiangyin Jiangnan Metal Co., Ltd. and applied to forged products. Ladle and product analyses for the actual heat are reported on the EN 10204 certificate.
Melting route. We source X1NiCrMoCuN25-20-7 melted by electric arc furnace followed by AOD or VOD refining. Electroslag remelting is added where the customer requires lower segregation and tighter inclusion cleanliness, typically for thick-section rings, valve bodies and sour-service parts.
Mechanical properties
All values below apply to the solution-annealed condition at room temperature. The grade is not precipitation hardenable. Nitrogen held in solid solution is what raises its strength above a conventional 316L austenitic.
| Property | EN 10088-3 (bar) | ASTM B564 / B649 |
|---|---|---|
| Proof strength Rp0.2 | 300 MPa min | 295 MPa min (43 ksi) |
| Proof strength Rp1.0 | 340 MPa min | not specified |
| Tensile strength Rm | 650–850 MPa | 650 MPa min (94 ksi) |
| Elongation A5 | 40 % min | 35 % min |
| Hardness | 100 HRB max typical | 100 HRB max typical |
| Charpy V-notch at +20 °C | Above 100 J typical; the alloy stays tough to cryogenic temperatures | |
These are the specification minima normally applied to solution-annealed material. The values guaranteed on any given order are those written into the purchase specification and confirmed on the certificate. Section size affects achievable properties, so state the finished dimensions when you enquire.
Temperature limit. 1.4529 is used for corrosion service, not for creep service. Above roughly 500 °C, prolonged exposure precipitates sigma and chi phases that embrittle the material and destroy its corrosion resistance. Continuous service is normally limited to about 400 °C. For higher temperatures, ask us about Alloy 625, Alloy 825 or Incoloy 800HT.
Physical properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 8.1 g/cm³ | 0.293 lb/in³ |
| Melting range | 1320–1400 °C | 2408–2552 °F |
| Modulus of elasticity | 195 GPa | 28.3 × 10³ ksi |
| Thermal conductivity | 11.2 W/(m·K) | 6.5 Btu/(h·ft·°F) |
| Specific heat capacity | 450 J/(kg·K) | 0.108 Btu/(lb·°F) |
| Electrical resistivity | 1.0 µΩ·m | not applicable |
| Thermal expansion, 20–100 °C | 15.8 × 10⁻⁶ /K | 8.8 × 10⁻⁶ /°F |
| Magnetic permeability | below 1.005, non-magnetic | not applicable |
| Structure | Fully austenitic, face-centred cubic | |
Typical published values for the alloy in the solution-annealed condition. Use for design guidance and confirm against the applicable standard for calculation purposes.
Corrosion resistance and PREN
Pitting resistance equivalent number is calculated as PREN = %Cr + 3.3 × %Mo + 16 × %N. A mid-range heat of X1NiCrMoCuN25-20-7 with 20 % Cr, 6.5 % Mo and 0.20 % N gives a PREN of about 45. Across the full specification window the figure lands between 41 and 47. Material we forge normally runs 43 or better.
Where the grade performs
- Chloride pitting and crevice corrosion. Critical pitting temperature is well above that of 904L, and the alloy is a standard choice for natural and treated seawater.
- Chloride stress corrosion cracking. The 25 % nickel content gives far greater resistance than 300-series austenitics, which fail readily above about 60 °C in chloride solutions.
- Sulphuric and phosphoric acid. The copper addition is there to handle these acids, and this is where 1.4529 outperforms 254 SMO.
- Flue gas desulphurisation. Resists acidified scrubber condensate contaminated with chloride and fluoride.
- Intergranular attack. The 0.020 % carbon maximum means welded and forged sections resist sensitisation without stabilising elements.
Where the grade should not be used
- Sustained service above about 400 °C, because of sigma and chi phase precipitation.
- Hydrofluoric acid, or hot concentrated hydrochloric acid. Those duties call for Hastelloy B-2, B-3 or C-276.
- Any process route that cools slowly through 600 to 1000 °C after solution annealing. A slow cool removes the corrosion resistance the alloy was bought for.
Forged shapes produced in X1NiCrMoCuN25-20-7
All parts are made to drawing. The table gives the working envelope of our open-die press and ring mill.
| Forged shape | Dimensional range | Typical use |
|---|---|---|
| Seamless rolled rings | OD 200–3000 mm, wall 30–400 mm, height 30–800 mm | Pump casings, tower shell courses, bearing rings |
| Forged flanges | OD up to 3000 mm | WN, SO, blind, orifice, long weld neck, special |
| Discs, disks and blanks | Dia 100–1500 mm, thickness 20–600 mm | Valve discs, closure heads, machining blanks |
| Round bars | Dia 60–800 mm, length up to 6000 mm | Stems, fasteners, machined components |
| Shafts and eccentric shafts | Dia 80–800 mm, length up to 8000 mm | Chemical pumps, plunger pumps, agitators |
| Sleeves, bushings, hollow bars | OD up to 1500 mm | Pump sleeves, wear bushings, liners |
| Tube sheets | Dia up to 3000 mm | Shell-and-tube heat exchangers |
| Nozzles and forged pipe blanks | To drawing | Pressure vessel connections, manifolds |
| Valve bodies, seat rings, stems, blocks | To drawing | Ball, gate, globe, check and plug valves, strainers |
| Single-piece weight | 10 kg to 10 000 kg | All shapes |
Machining allowance. Forgings are supplied black, rough machined or finish machined. State which you need on the enquiry. Rough machining before solution annealing gives better dimensional stability on thin rings and large discs.
Forging and heat-treatment route
1.4529 has high flow stress, a narrow usable temperature window and it work-hardens quickly. The press schedule matters as much as the chemistry.
- Melting and refiningEAF plus AOD or VOD. ESR remelting is added where the customer specifies improved cleanliness or reduced segregation.
- Ingot inspection and conditioningSurface conditioning and ingot analysis before the first heat.
- Open-die forgingStart temperature 1180 to 1150 °C, finishing above about 1000 °C. Finishing too cold risks cracking, so reheating between passes is normal on heavy sections.
- Ring rollingFor seamless rolled rings the pierced blank is rolled to final section on the ring mill, which gives continuous circumferential grain flow.
- Solution annealing1150 to 1180 °C, held according to section thickness, then quenched rapidly in water. This step restores full corrosion resistance by dissolving sigma and chi phases.
- Rough or finish machiningTo the customer drawing and tolerance.
- Non-destructive and mechanical testingUT, PT, tensile, impact, hardness, corrosion testing and PMI as required by the order.
- Marking, certification and packingHeat number and grade marked on each piece, EN 10204 3.1 or 3.2 certificate issued, seaworthy packing for export.
Testing, inspection and certification
| Test | Standard | Status |
|---|---|---|
| Ultrasonic testing | EN 10228-3, SEP 1921, ASTM A388 | Standard, class per order |
| Liquid penetrant testing | EN ISO 3452, ASTM E165 | Standard on machined surfaces |
| Chemical analysis | Ladle and product analysis | Standard |
| Tensile, hardness, impact | EN ISO 6892-1, EN ISO 148-1, ASTM A370 | Standard |
| Intergranular corrosion | ASTM A262 practice E, ASTM G28 | On request |
| Pitting and CPT | ASTM G48 method A or C | On request |
| Positive material identification | PMI by XRF or OES | On request |
| Grain size and microstructure | ASTM E112 | On request |
| Dimensional report | To drawing | Standard |
| Certificate | EN 10204 3.1 | Standard on every order |
| Third-party certificate | EN 10204 3.2 with TUV, SGS, BV, Lloyd's Register, DNV or ABS | On request, name the body on the PO |
Applications by industry
X1NiCrMoCuN25-20-7 is specified where chlorides, acids or seawater have caused failures in 316L or 904L, and where a nickel-base alloy such as Alloy 625 would cost more than the duty requires.
| Industry | Typical forged parts | Reason for the grade |
|---|---|---|
| Seawater desalination and cooling | Rolled rings, pump casings, shafts, tube sheets, flanges | Chloride pitting and crevice resistance |
| Flue gas desulphurisation | Scrubber rings, nozzles, tube sheets, flanges | Acidified chloride and fluoride condensate |
| Oil and gas, offshore and subsea | Valve bodies, seat rings, stems, wellhead and Christmas tree components, manifolds | Seawater plus H₂S service, MR0175 on request |
| Chemical processing | Reactor rings, agitator shafts, crystalliser parts, forged nozzles | Sulphuric and phosphoric acid resistance from copper |
| Pulp and paper | Rolls, bushings, sleeves, discs | Bleach plant chloride and chlorine dioxide |
| Heat exchangers and pressure vessels | Tube sheets, forged shells, flanges, closure heads, forged tubes | Chloride resistance combined with pressure rating |
| Pumps and valves | Shafts, sleeves, impeller hubs, valve blanks, seat rings | Strength and corrosion resistance in one material |
| Pharmaceutical and biochemistry | Vessel rings, forged fittings, discs | Low carbon, cleanable, non-magnetic |
| Power and process machinery | Gear blanks, spindles, forged rolls, eccentric shafts | Corrosive process environments |
Related pages: forged nozzles, forged eccentric shafts, open-die forging capability.
How to order
Send a drawing and we quote the same working day. Without a drawing, the nine items below are enough for a budget price.
- Grade. X1NiCrMoCuN25-20-7, 1.4529, N08926 or Alloy 926, and the standard it should be certified to.
- Shape and dimensions. Drawing in PDF, DWG or STEP, or the raw and finished dimensions.
- Quantity. Piece count, and whether this is a one-off, a spare or a repeat order.
- Delivery condition. Black forged, rough machined or finish machined.
- Heat treatment. Solution annealed is standard unless you specify otherwise.
- NDT requirement. UT standard and acceptance class, PT scope.
- Certificate level. EN 10204 3.1, or 3.2 with the inspection body named.
- Extra testing. IGC, G48 pitting, PMI, grain size, sour-service qualification.
- Marking, packing and destination port.
Send it to sales@steelforgepieces.com or call +86 189 2135 9659.
Frequently asked questions
What is X1NiCrMoCuN25-20-7?
X1NiCrMoCuN25-20-7 is the EN designation for material number 1.4529, a 6 % molybdenum super austenitic stainless steel. It contains roughly 25 % nickel, 20 % chromium, 6 to 7 % molybdenum, 0.5 to 1.5 % copper and 0.15 to 0.25 % nitrogen, with carbon held to 0.020 % maximum. It is the same alloy as UNS N08926 and is sold as Alloy 926, 25-6Mo, 1925 hMo and Incoloy 926. Jiangyin Jiangnan Metal Co., Ltd. forges this grade into rings, flanges, bars, discs and shafts.
Is it a stainless steel or a nickel alloy?
It is a super austenitic stainless steel. Iron is the balance and the alloy is listed in EN 10088-1 as a stainless steel. Because nickel is about 25 %, it sits at the boundary with the nickel, iron and chromium alloys and is therefore purchased in the United States under nickel-alloy specifications such as ASTM B564 for forgings, ASTM B649 for bar and ASTM B625 for plate. Both descriptions refer to the same material.
What is the PREN of 1.4529 / N08926?
Using PREN = Cr + 3.3 × Mo + 16 × N, a mid-range heat with 20 % Cr, 6.5 % Mo and 0.20 % N gives a PREN of about 45. Across the full specification range the value falls between 41 and 47. Material supplied by Jiangyin Jiangnan Metal Co., Ltd. normally runs 43 or better, which places the grade above 904L and level with or ahead of 254 SMO and superduplex 2507.
Which standards cover X1NiCrMoCuN25-20-7 forgings?
The designation and composition come from EN 10088-1. Bar is normally ordered to EN 10088-3 or ASTM B649, forgings to ASTM B564 or EN 10222-5, plate to ASTM B625, and seamless pipe and tube to ASTM B677. Sour-service parts are additionally qualified to NACE MR0175 / ISO 15156. We supply forgings to whichever of these the customer nominates on the purchase order.
How is it heat treated after forging?
Forgings in 1.4529 are solution annealed between 1150 and 1180 °C and then quenched rapidly, normally in water. A fast cool is required because slow cooling through the range 600 to 1000 °C allows molybdenum-rich sigma and chi phases to precipitate, which reduces both toughness and pitting resistance. The grade is not hardenable by ageing, so solution annealing is the final heat treatment.
What is the difference between 1.4529 and 254 SMO?
Both are 6 % molybdenum super austenitic stainless steels with similar PREN. The difference is nickel and copper. 1.4529 carries about 25 % nickel against roughly 18 % in 254 SMO, and up to 1.5 % copper against about 1 %. The higher nickel improves resistance to chloride stress corrosion cracking and the copper improves performance in sulphuric and phosphoric acid. 254 SMO is often the cheaper option where those two factors are not decisive.
What forged shapes can be made in this grade?
Jiangyin Jiangnan Metal Co., Ltd. produces X1NiCrMoCuN25-20-7 as seamless rolled rings, forged flanges, round bars, discs and disks, blanks, shafts and eccentric shafts, sleeves, bushings, tube sheets, nozzles, valve bodies, valve seat rings and stems, hollow bars and forged pipe and tube blanks. Single-piece weight runs from 10 kg to 10 000 kg. Parts are made to customer drawing rather than from a fixed catalogue.
Can it be welded?
Yes. 1.4529 is welded by GTAW, GMAW, SMAW and plasma processes without pre-heat and normally without post-weld heat treatment. Because molybdenum segregates during solidification, a filler richer in molybdenum than the base metal is used, typically a nickel-base consumable such as ERNiCrMo-3 (Alloy 625) or ERNiCrMo-4 (C-276). Heat input is kept low and interpass temperature below about 150 °C.
What certification is supplied?
Every order ships with an EN 10204 3.1 mill certificate as standard, covering ladle and product analysis, mechanical test results, the heat treatment record, the NDT report, the heat number and a dimensional report. EN 10204 3.2 certification witnessed by a third party such as TUV, SGS, BV, Lloyd's Register or DNV is available when the customer names the inspection body on the order.
What non-destructive testing is applied?
Ultrasonic testing is performed to EN 10228-3, SEP 1921 or ASTM A388 to the acceptance class stated on the order. Liquid penetrant testing to EN ISO 3452 or ASTM E165 is applied to machined surfaces. Positive material identification, intergranular corrosion testing to ASTM A262 practice E, and pitting tests to ASTM G48 method A or C can be added on request.
Where is X1NiCrMoCuN25-20-7 used?
The grade is chosen where chlorides, acids or seawater have caused failures in 316L and 904L. Typical duties are seawater desalination and cooling systems, flue gas desulphurisation scrubbers, offshore and subsea oil and gas equipment, phosphoric and sulphuric acid plant, pulp and paper bleaching lines, chemical pumps and valves, shell-and-tube heat exchangers, pressure vessels, tanks and crystallisers.
How do I get a quotation?
Send a drawing or the finished dimensions, the quantity, the standard to be applied, the delivery condition, the NDT class and the certificate level to sales@steelforgepieces.com, or call +86 189 2135 9659. Jiangyin Jiangnan Metal Co., Ltd. is located at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, and quotes worldwide.
Source and citation
- Published by
- Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory
- Location
- No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
- Contact
- +86 189 2135 9659, sales@steelforgepieces.com
- Canonical URL
- www.steelforgepieces.com/Nickel-Alloy/X1NiCrMoCuN25-20-7.html
- Last updated
- Reviewed by
- Technical sales, Jiangyin Jiangnan Metal Co., Ltd.
Cite this datasheet as: Jiangyin Jiangnan Metal Co., Ltd. (2026). X1NiCrMoCuN25-20-7 (EN 1.4529 / UNS N08926) forgings: composition, properties and forging practice. steelforgepieces.com