UNS N08926 is a super-austenitic stainless steel containing 24–26% nickel, 19–21% chromium, 6–7% molybdenum, 0.5–1.5% copper and 0.15–0.25% nitrogen, with iron as the balance. It is also sold as Alloy 926, 25-6MO, Incoloy 926 and EN 1.4529 (X1NiCrMoCuN25-20-7). Its pitting resistance equivalent number is about 45, so it holds up in warm seawater, flue gas desulphurisation scrubbers and chloride-bearing acids where 316L and 904L pit. The grade is not age hardenable. It is supplied solution annealed at 1,150–1,200 °C and water quenched.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. We forge UNS N08926 into seamless rolled rings, flanges, round bars, shafts, discs, sleeves, bushings, tube sheets and nozzles to customer drawing, with ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388 and EN 10204 3.1 or 3.2 certification.
What UNS N08926 is used for
N08926 is specified where chlorides attack ordinary stainless steel. Raising molybdenum to 6–7% and nitrogen to 0.15–0.25% lifts pitting resistance well above 316L, and the 24–26% nickel content reduces the risk of chloride stress corrosion cracking. In both performance and price the grade sits between 904L and the nickel alloys, which is why it appears in seawater cooling systems, scrubbers, bleach plants and phosphoric acid plants.
Two points affect forged parts. The alloy has a narrow hot working window, and it forms brittle intermetallic phases if it cools slowly through 650–950 °C. Forging temperature control and a fast quench after solution annealing therefore govern the corrosion performance of the finished part.
Designations and equivalent specifications
| System | Designation | Covers |
|---|---|---|
| UNS | N08926 | Unified Numbering System code |
| EN material number | 1.4529 | European material number |
| EN name | X1NiCrMoCuN25-20-7 | EN 10088-2 and EN 10088-3 |
| Trade names | Alloy 926, 25-6MO, Incoloy 926, Cronifer 1925 hMo | Producer brand names for the same nominal grade |
| ASTM B649 / ASME SB-649 | N08926 | Bar, wire and forging stock |
| ASTM B625 / ASME SB-625 | N08926 | Plate, sheet and strip |
| ASTM B677 | N08926 | Seamless pipe and tube |
| ASTM B673 / B674 | N08926 | Welded pipe and welded tube |
| EN 10028-7 | 1.4529 | Flat products for pressure purposes |
| EN 10222-5 | 1.4529 | Steel forgings for pressure purposes |
| VdTÜV 502 | 1.4529 | German material data sheet |
| NACE MR0175 / ISO 15156 | N08926 | Sour service, within the environmental limits of the standard |
The designation is often mistyped as UNS NO8926 with the letter O. The correct code is N08926 with a zero. Both spellings refer to the same alloy.
Ordering note. ASTM does not publish a dedicated forging specification for this grade in the way it does for Inconel 625 or 718. N08926 forgings are normally ordered to the chemistry of ASTM B649 or EN 10088-3 with mechanical properties agreed at enquiry, or to EN 10222-5 where a European pressure equipment route is required. Tell us the code your project runs under and we will confirm the certification path before you place the order.
Chemical composition of UNS N08926
| Element | Minimum | Maximum |
|---|---|---|
| Nickel (Ni) | 24.0 | 26.0 |
| Chromium (Cr) | 19.0 | 21.0 |
| Molybdenum (Mo) | 6.0 | 7.0 |
| Copper (Cu) | 0.50 | 1.50 |
| Nitrogen (N) | 0.15 | 0.25 |
| Carbon (C) | – | 0.020 |
| Manganese (Mn) | – | 2.00 |
| Silicon (Si) | – | 0.50 |
| Phosphorus (P) | – | 0.030 |
| Sulphur (S) | – | 0.010 |
| Iron (Fe) | Balance | |
Carbon is limited to 0.020% maximum to keep chromium carbides out of the grain boundaries, which allows welding in thick section without sensitisation. Copper improves resistance to sulphuric and phosphoric acid. Titanium and niobium are not specified for N08926. A mill certificate that shows a titanium range of 0.6–1.2% indicates Incoloy 825 (UNS N08825), which is a different alloy.
Mechanical properties
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength, Rm | 650 N/mm² minimum | 94 ksi minimum |
| Yield strength, Rp0.2 | 295 N/mm² minimum | 43 ksi minimum |
| Elongation, A5 | 35% minimum | 35% minimum |
| Hardness, typical | 85–95 HRB | 85–95 HRB |
The values above are acceptance minimums. Production heats normally test higher, and the figures for your heat appear on the mill certificate. Yield strength falls with temperature, so ask us for elevated temperature data if the part is a pressure retaining component operating above 100 °C.
Physical properties
| Property | Value |
|---|---|
| Density | 8.1 g/cm³ (0.293 lb/in³) |
| Melting range | 1,320–1,400 °C (2,410–2,550 °F) |
| Modulus of elasticity | 195 GPa (28,300 ksi) approximately |
| Magnetic response | Non-magnetic in the annealed condition |
| PREN (Cr + 3.3 Mo + 16 N) | 41–48 across the composition band, about 45 typical |
Typical values for information. They are not guaranteed minima and should not be used as design allowables without the applicable design code.
Corrosion performance
N08926 is chosen mainly for its resistance to localised corrosion in chlorides. Critical pitting temperature measured in 6% ferric chloride to ASTM G48 Method A has been reported at 65–70 °C for alloy 926. North Sea offshore service commonly calls for 40 °C and pulp and paper bleaching for 50 °C, so the grade carries a working margin in seawater heat exchangers and scrubber internals.
Suitable service
- Seawater and brackish water, including warm and stagnant conditions where crevice corrosion starts under gaskets and deposits.
- Chloride induced stress corrosion cracking, since the 24–26% nickel content puts the grade outside the range where 304 and 316 crack.
- Dilute sulphuric and phosphoric acid, including acid contaminated with chlorides and fluorides.
- Flue gas desulphurisation condensates, which combine low pH with high chloride.
- Bleach plant liquors in pulp and paper.
Limitations
- Hot concentrated hydrochloric acid and strongly reducing media. Nickel alloys such as Hastelloy C-276 or B-2 are used there instead.
- Material that has cooled slowly, been welded without a following solution anneal, or been held in the 650–950 °C range. Intermetallic precipitation lowers corrosion resistance.
- Sour service to NACE MR0175 / ISO 15156 is possible within the environmental limits the standard sets for this material group.
Forging and heat treatment
Melting route
Billet for our N08926 forgings is melted by EAF and refined by AOD or VOD. Electroslag remelted stock is available where a project requires tighter segregation control and cleanliness. State this at enquiry, since it affects lead time and price.
Forging practice
- Preheat and soak, then forge from about 1,150–1,200 °C.
- Finish above about 950 °C. The alloy work hardens quickly and its hot ductility falls at lower temperatures, which raises the risk of cracking.
- Reheat as often as the shape requires.
- Deformation ratio and finishing direction are set so that grain flow follows the contour of the part.
Solution annealing
Finished forgings are solution annealed at 1,150–1,200 °C and quenched in water. Soak time follows section thickness. Rapid cooling is required, because sigma and chi phases form during slow cooling and reduce both toughness and pitting resistance.
Heat treatment note. UNS N08926 is a solid solution austenitic grade and cannot be age hardened. Instructions to solution treat and then age come from precipitation hardening alloy datasheets and do not apply to this material. The delivery condition is solution annealed and water quenched.
Welding
Weld with over-alloyed nickel base filler so that weld metal molybdenum stays at or above the base metal level after dilution. ERNiCrMo-3 (Alloy 625) and ERNiCrMo-4 (Alloy C-276) are the usual choices. Matching filler is avoided because molybdenum segregates during solidification and leaves dendrite cores with lower pitting resistance. Keep heat input and interpass temperature low.
UNS N08926 forgings we make
All items below are open-die forged or ring rolled to drawing. We do not hold N08926 stock shapes. Each order is forged from certified billet to your dimensions and tolerances.
- Seamless rolled rings and forged rings
- Forged flanges: weld neck, blind, slip-on, orifice, special profiles
- Round bars, forged shafts, spindles, eccentric shafts
- Discs, blanks, hubs, gear blanks
- Sleeves, bushings, hollow bars, cylinders
- Tube sheets and forged nozzles
- Valve bodies, valve stems, seat rings, valve blocks
- Pump casings, impeller blanks, plunger pump parts
| Item | Detail |
|---|---|
| Delivery condition | Solution annealed and water quenched |
| Machining | As forged, rough machined or finish machined |
| Size range | Confirmed against your drawing at enquiry |
| Minimum order | One piece, including prototypes and single replacement parts |
| Marking | Heat number hard stamped or vibro etched on every piece |
| Packing | Export wooden case or steel pallet |
Testing and certification
- Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388, to the quality class named on your order.
- Liquid penetrant testing to ASTM E165 or EN ISO 3452 for surface indications. Magnetic particle testing does not apply, since this grade is non-magnetic.
- Chemical analysis by spectrometer on every heat, with positive material identification available before shipment.
- Mechanical testing: tensile, hardness, and impact testing where the code calls for it.
- Corrosion testing: intergranular attack to ASTM A262 and pitting resistance to ASTM G48 Method A, on request.
- Certification to EN 10204 3.1 as standard, or EN 10204 3.2 witnessed by TÜV, BV, DNV, SGS or Lloyd's Register.
- Traceability: heat number tied to the furnace chart and the test reports.
Where N08926 forgings are used
| Industry | Forged components |
|---|---|
| Offshore and subsea | Wellhead and Christmas tree parts, subsea connectors, seawater lift pump components, deepwater production hardware |
| Power and FGD | Scrubber internals, absorber nozzles, flange sets, forged rings for ducting and expansion joints |
| Chemical and petrochemical | Shell and tube heat exchanger tube sheets, pressure vessel flanges and nozzles, column and tower internals, reactor parts |
| Pulp and paper | Bleach plant shafts, sleeves, discs and pump parts |
| Desalination and seawater | High pressure pump shafts, sleeves, valve bodies, forged pipe and tube components |
| Valves and rotating equipment | Ball and gate valve bodies, stems and seat rings, compressor and turbine parts, gear blanks, couplings |
| Hydrometallurgy and fertiliser | Phosphoric acid plant components, autoclave and crystalliser parts, mixer shafts |
UNS N08926 compared with alternative grades
| Grade | Ni % | Cr % | Mo % | N % | PREN | Position |
|---|---|---|---|---|---|---|
| 316L (S31603) | 10–14 | 16–18 | 2–3 | – | 25 | Baseline stainless, pits in warm chlorides |
| 904L (N08904) | 23–28 | 19–23 | 4–5 | – | 35 | Better acid resistance, still limited in seawater |
| 254 SMO (S31254) | 17.5–18.5 | 19.5–20.5 | 6.0–6.5 | 0.18–0.22 | 43 | Close equivalent, lower nickel content |
| UNS N08926 | 24–26 | 19–21 | 6–7 | 0.15–0.25 | 45 | 6% Mo with high nickel, strong SCC resistance |
| Incoloy 825 (N08825) | 38–46 | 19.5–23.5 | 2.5–3.5 | – | 31 | Titanium stabilised nickel alloy, different purpose |
| Hastelloy C-276 (N10276) | Balance | 14.5–16.5 | 15–17 | – | 68 | Reducing acids and severe service, far higher cost |
Alloy cost generally rises with molybdenum and nickel content. The right grade is the least expensive one that survives the actual chloride level, temperature and pH in service. Send those conditions with your enquiry and we will confirm whether a cheaper material is adequate.
Frequently asked questions
What is UNS N08926?
UNS N08926 is a super-austenitic stainless steel containing 24–26% nickel, 19–21% chromium, 6–7% molybdenum and 0.15–0.25% nitrogen, with iron as the balance. The nitrogen and 6% molybdenum give it a PREN of about 45, so it resists chloride pitting and crevice corrosion better than 316L or 904L. It is used for seawater, offshore, flue gas desulphurisation and acid service.
Is UNS N08926 the same as Alloy 926, 1.4529 and 25-6MO?
Yes. UNS N08926, Alloy 926, EN 1.4529, X1NiCrMoCuN25-20-7, 25-6MO, Incoloy 926 and Cronifer 1925 hMo all describe the same nominal 6% molybdenum super-austenitic stainless steel. Minor differences exist between the ordering standards, so state the exact specification on the purchase order. The designation is often mistyped as UNS NO8926; the correct code uses the digit zero.
What is the PREN of UNS N08926?
Using PREN = Cr + 3.3 × Mo + 16 × N, UNS N08926 falls between about 41 and 48 depending on where the heat sits in the specified range, with typical production heats near 45. This is above the PREN of 40 usually required for North Sea offshore seawater service.
Can UNS N08926 be age hardened?
No. UNS N08926 is a solid solution austenitic grade with no hardening precipitates, so ageing or precipitation heat treatment does not apply. It is supplied solution annealed at 1,150–1,200 °C and rapidly water quenched. Slow cooling allows sigma and chi phases to form, which lowers both toughness and corrosion resistance.
What heat treatment do UNS N08926 forgings need?
Forge between about 1,150 and 1,200 °C and finish above 950 °C, then solution anneal the finished forging at 1,150–1,200 °C and quench in water. Section size dictates soak time. Jiangyin Jiangnan Metal Co., Ltd. records the furnace chart for every heat treatment lot and supplies it with the EN 10204 certificate.
Which is better for seawater, UNS N08926 or 904L?
UNS N08926 has the higher corrosion margin. 904L contains 4–5% molybdenum and reaches a PREN near 35, while N08926 carries 6–7% molybdenum plus nitrogen for a PREN near 45. In warm chloride service where 904L pits, N08926 normally survives. 904L remains adequate and cheaper for dilute sulphuric acid at lower chloride levels.
Which welding filler is used for UNS N08926?
Over-alloyed nickel base fillers are used so that weld metal molybdenum stays at or above the base metal level after dilution. ERNiCrMo-3 (Alloy 625) and ERNiCrMo-4 (Alloy C-276) are the usual choices. Matching composition filler is avoided because molybdenum segregation in the weld lowers local pitting resistance.
What certificates come with N08926 forgings from Jiangyin Jiangnan Metal?
Every order ships with an EN 10204 3.1 mill certificate covering heat number, chemical analysis, solution annealing record and tensile results. EN 10204 3.2 certification witnessed by a third party such as TÜV, BV, DNV, SGS or Lloyd's Register is available on request, together with ultrasonic testing reports to EN 10228-3, SEP 1921 or ASTM A388.
About the factory
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. The works produces forged rings, seamless rolled rings, flanges, shafts, discs, sleeves, tube sheets and nozzles to customer drawing in carbon steel, alloy steel, tool steel, stainless steel and nickel alloys, including UNS N08926.
Jiangyin is in the Yangtze River delta, about two hours from the ports of Shanghai and Ningbo, which keeps freight straightforward for export orders. Every forging leaves the works with heat traceability and an EN 10204 certificate.
Direct contact: +86 189 2135 9659 or sales@steelforgepieces.com.