Super-austenitic, 6 % molybdenum, open-die forgings
1.4529 ForgingsUNS N08926 / Alloy 926 / 25-6Mo / X1NiCrMoCuN25-20-7
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu, China. We forge 1.4529 (UNS N08926, Alloy 926) to customer drawings: seamless rolled rings, forged rings, flanges, shafts, round bars, discs, sleeves, bushings, tube sheets, blocks and nozzles, in unit weights from about 20 kg to 8,000 kg.
1.4529 is a 6 % molybdenum super-austenitic stainless steel. Its pitting resistance equivalent number (PREN) is about 45. The grade was developed from 904L by raising molybdenum from roughly 4.5 % to 6.5 % and adding nitrogen. It is specified where 316L and 904L no longer hold up: warm seawater, high-chloride process streams, flue gas desulphurisation, desalination, and phosphoric or sulphuric acid service.
Forgings are made to ASTM B564, ASTM B649 or EN 10222-5. They are solution annealed at 1100 to 1180 °C and water quenched. The grade is not age hardenable, so there is no ageing step. Every piece is ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388 and certified to EN 10204 3.1, or 3.2 with third-party witness. Send a drawing to sales@steelforgepieces.com for a quotation.
1 Designations and equivalents
1.4529 is sold under a number of names. Three standards systems and several mills each have their own designation for the same alloy. Everything in the table below describes the same material.
| System | Designation | Note |
|---|---|---|
| EN material number | 1.4529 | Also written W.-Nr. 1.4529 |
| EN name | X1NiCrMoCuN25-20-7 | Per EN 10088-3 |
| UNS | N08926 | Primary US equivalent |
| Trade names | Alloy 926, 25-6Mo, 6Mo, Cronifer 1925 hMo, Incoloy 25-6MO, 1925 hMo | Mill-specific brand names |
| JIS (near) | SUS 317J5L | Close, not identical |
| Close relatives | AL-6XN (N08367), 254 SMO (1.4547 / S31254) | Same 6 % Mo family, see clause 9 |
AL-6XN has almost the same analysis but no European material number, which limits its use in EU pressure equipment. If your specification calls for a European W.-Nr., 1.4529 is the grade to buy.
2 Chemical composition
Heat analysis for 1.4529 forgings in weight percent, to EN 10088-3 and ASTM B649. Each heat we forge is supplied with its own ladle analysis on the mill certificate.
| Element | C | Si | Mn | P | S | Cr | Mo | Ni | Cu | N | Fe |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | - | - | - | - | - | 19.0 | 6.0 | 24.0 | 0.50 | 0.15 | Bal. |
| Max | 0.020 | 0.50 | 1.00 | 0.030 | 0.010 | 21.0 | 7.0 | 26.0 | 1.50 | 0.25 |
Fe is the balance. Carbon is held to 0.020 % max to suppress chromium carbide precipitation. Nitrogen is a deliberate addition that stabilises austenite, raises strength and lifts PREN. Copper improves resistance to sulphuric and phosphoric acid.
Physical properties
| Property | Value |
|---|---|
| Density | about 8.1 g/cm³ (0.293 lb/in³) |
| Melting range | about 1320 to 1400 °C |
| Modulus of elasticity | about 195 GPa |
| Magnetic response | Non-magnetic in the solution annealed condition |
| Structure | Fully austenitic, no ferrite, no martensite |
3 Mechanical properties
Minimum room-temperature properties for 1.4529 forgings in the solution annealed and water quenched condition. Test specimens come from a prolongation representing the forging, heat treated with it.
| Property | Metric | Imperial | Basis |
|---|---|---|---|
| 0.2 % proof stress, Rp0.2 | 295 N/mm² min | 43 ksi min | Specified minimum |
| Tensile strength, Rm | 650 N/mm² min | 94 ksi min | Specified minimum |
| Elongation, A5 | 35 % min | 35 % min | Specified minimum |
| Hardness | 100 HRB max | 100 HRB max | Typical, not a specification requirement |
| Impact energy, KV at 20 °C | 100 J typical | 74 ft-lb typical | Tested on request |
Low-temperature Charpy testing at -46 °C, -101 °C or -196 °C, hot tensile testing and grain size determination can be added to the test plan. State the requirement on your enquiry so it is written into the forging route before production starts.
4 Corrosion resistance and PREN
PREN is the number that decides whether 1.4529 is the right grade for a given service. It is calculated as PREN = %Cr + 3.3 × %Mo + 16 × %N. At a mid-range analysis of 20 % Cr, 6.5 % Mo and 0.20 % N, 1.4529 reaches about 45.
- 316L25
- 904L / 1.453935
- 1.4529 / N0892645
- Inconel 62551
- Hastelloy C-27668
A PREN above roughly 40 is the usual threshold for ambient seawater service. 1.4529 clears it with margin at a fraction of the cost of a nickel-base alloy. That price gap is the main commercial reason the grade gets specified.
What 1.4529 resists
- Chloride pitting and crevice corrosion in seawater, brackish water and high-chloride process streams.
- Chloride stress corrosion cracking. The 24 to 26 % nickel gives far better resistance than 300-series grades, which typically crack above 60 °C in chlorides.
- Reducing acids. The copper addition helps in sulphuric acid at intermediate concentrations and in phosphoric acid.
- Intergranular attack. Carbon at 0.020 % max means sensitisation is not a practical concern in the annealed condition.
- Sour service. Listed in NACE MR0175 / ISO 15156, subject to the temperature, chloride and H2S partial-pressure limits in the standard.
5 1.4529 forged product forms and size envelope
All forms below are produced open-die, to your drawing, in 1.4529. Ring blanks are radial-axial rolled. Solid parts are cogged and upset under press. Machining allowance is agreed on the drawing, and we can also supply finish-machined parts with a dimensional report.
| Forged form | Typical size range | Unit weight |
|---|---|---|
| Seamless rolled rings | OD 300 to 3,000 mm, wall 30 to 400 mm, height 50 to 1,000 mm | 30 to 6,000 kg |
| Forged rings and retaining rings | OD 150 to 2,000 mm | 20 to 3,000 kg |
| Flanges (WN, SO, BL, LJ, orifice) | DN 15 to DN 2000, to ASME B16.5 / B16.47 / EN 1092-1 | 2 to 2,500 kg |
| Shafts, spindles, eccentric shafts | 60 to 800 mm dia, length to 6,000 mm | 30 to 8,000 kg |
| Round bars and billets | 50 to 800 mm dia, length to 6,000 mm | 20 to 8,000 kg |
| Discs, blanks and gear blanks | 100 to 2,500 mm dia, thickness 30 to 600 mm | 20 to 6,000 kg |
| Tube sheets | To 2,500 mm dia, thickness to 400 mm | To 6,000 kg |
| Sleeves and bushings | OD 100 to 1,500 mm | 20 to 2,000 kg |
| Hollow bars and forged tubes | OD 150 to 1,200 mm, length to 4,000 mm | 30 to 4,000 kg |
| Blocks, plates and rectangular forgings | To 1,500 x 800 x 600 mm | To 8,000 kg |
| Valve bodies, seat rings, stems, plugs | To drawing | 1 to 3,000 kg |
| Forged nozzles and manifolds | To drawing | 5 to 3,000 kg |
Indicative envelope for planning. Confirm your geometry, tolerance and weight on enquiry. Send the drawing and we will tell you within one working day whether it falls inside our press and ring mill capacity.
6 How we forge 1.4529
1.4529 is a difficult grade to forge. The high alloy content narrows the hot working window, and sigma and chi phase will precipitate if the finish temperature drops too far or the solution anneal is cut short. The route below is what keeps the corrosion performance intact.
- MeltingEAF with AOD or VOD refining. ESR remelt available where the specification or NDT class calls for it.
- Ingot and billet inspectionLadle analysis verified, ingot conditioned, surface defects ground out before heating.
- HeatingSoaked to 1150 to 1200 °C with a controlled ramp and hold to equalise through-section temperature.
- Open-die forgingCogged and upset on hydraulic press to reach the specified forging reduction ratio, typically 3:1 or better, and to break down the as-cast structure. Finish temperature is held above about 1000 °C, with reheats as required rather than forging cold.
- Ring rollingFor rings, radial-axial rolling to a near-net blank on the ring mill.
- Solution annealing1100 to 1180 °C, soaked to section, then rapid water quench. This dissolves intermetallics and restores PREN. There is no ageing step, since 1.4529 is not precipitation hardenable.
- Descaling and picklingScale removed, then the surface is pickled and passivated so the passive film reforms cleanly.
- Rough or finish machiningTo the agreed allowance, or fully finished to drawing with a dimensional report.
- Testing and NDTMechanical testing, PMI, ultrasonic and surface examination, as set out in clause 7.
- Marking, certification and packingHard-stamped or vibro-etched with heat number and part identity, certified to EN 10204 3.1 or 3.2, seaworthy packed.
7 Testing, NDT and certification
| Test | Standard | Scope |
|---|---|---|
| Chemical analysis | Spectrometric, per heat | Standard |
| Positive material identification | XRF or OES, per piece | Standard |
| Tensile and elongation | ASTM A370 / EN ISO 6892-1 | Standard |
| Hardness | ASTM E18 / EN ISO 6508 | Standard |
| Ultrasonic testing | EN 10228-3, SEP 1921, ASTM A388 | Standard, class to your specification |
| Liquid penetrant | ASTM E165 / EN ISO 3452 | On request |
| Intergranular corrosion | ASTM A262 Practice E, ASTM G28 | On request |
| Pitting corrosion | ASTM G48 Method A | On request |
| Charpy V-notch impact | ASTM A370 / EN ISO 148-1 | On request, including sub-zero |
| Grain size and micro | ASTM E112 | On request |
| Sour service compliance | NACE MR0175 / ISO 15156 | On request |
| Material certificate | EN 10204 3.1 standard, EN 10204 3.2 third-party | 3.2 witnessed by TUV, SGS, BV, LR or DNV |
8 Where 1.4529 forgings are used
1.4529 gets specified when the chloride level, temperature or acid concentration has already defeated 316L or 904L, but a full nickel-base alloy is not commercially justified. Typical forged applications by industry:
| Industry | Typical 1.4529 forged components |
|---|---|
| Seawater desalination | High-pressure pump shafts and casings, rolled rings, flanges, tube sheets for MSF and MED evaporators |
| Flue gas desulphurisation | Absorber nozzles, flanges, agitator shafts, sleeves in scrubber duty |
| Offshore oil and gas | Subsea and topside valve bodies, seat rings, stems, hydraulic and chemical-injection manifolds, wellhead components |
| Chemical process | Reactor and column flanges, heat exchanger tube sheets, pump and mixer shafts, phosphoric and sulphuric acid service parts |
| Pulp and paper | Bleach plant shafts, rolls, rings and flanges in chlorine dioxide service |
| Power generation | Condenser tube sheets, seawater cooling flanges, forged pipe and pipe fittings |
| Salt and crystallisation | Evaporator and crystalliser rings, discs, shafts and sleeves |
| Marine and shipbuilding | Seawater filtration housings, firewater system components, propulsion sleeves and bushings |
| Pharmaceutical and biochemistry | Vessel flanges, agitator shafts, forged discs for high-purity aggressive media |
9 1.4529 compared with 904L, 254 SMO and AL-6XN
These four grades are routinely cross-quoted against each other. In practice the differences that matter are molybdenum content, nickel content, and whether the grade carries a European material number.
| Grade | UNS | EN no. | Cr % | Ni % | Mo % | Cu % | N % | PREN |
|---|---|---|---|---|---|---|---|---|
| 316L | S31603 | 1.4404 | 16.5-18.5 | 10-13 | 2.0-2.5 | - | - | 25 |
| 904L | N08904 | 1.4539 | 19-23 | 23-28 | 4.0-5.0 | 1.0-2.0 | - | 35 |
| 254 SMO | S31254 | 1.4547 | 19.5-20.5 | 17.5-18.5 | 6.0-6.5 | 0.5-1.0 | 0.18-0.25 | 43 |
| 1.4529 | N08926 | 1.4529 | 19-21 | 24-26 | 6.0-7.0 | 0.5-1.5 | 0.15-0.25 | 45 |
| AL-6XN | N08367 | none | 20-22 | 23.5-25.5 | 6.0-7.0 | 0.75 max | 0.18-0.25 | 46 |
254 SMO is the leanest of the 6 % Mo grades on nickel. 1.4529 and AL-6XN carry more nickel for better stress corrosion cracking resistance. Only 1.4529 has a European material number, which makes it the default choice for PED and EN-coded pressure equipment. We forge all four.
10 Frequently asked questions about 1.4529
What is 1.4529 material?
1.4529, EN designation X1NiCrMoCuN25-20-7, is a super-austenitic stainless steel. It contains roughly 20 % chromium, 25 % nickel, 6.5 % molybdenum, 1 % copper and 0.2 % nitrogen, with carbon held to 0.020 % maximum. It was developed from 904L (1.4539) by raising the molybdenum content, which lifts its pitting resistance equivalent number to about 45. Jiangyin Jiangnan Metal Co., Ltd. supplies it as open-die forgings.
What is 1.4529 equivalent to?
1.4529 is equivalent to UNS N08926 in the American system. It is sold commercially as Alloy 926, 25-6Mo, Cronifer 1925 hMo, Incoloy 25-6MO and simply 6Mo. AL-6XN (UNS N08367) is a close relative with a very similar composition, but it has no European material number and is therefore harder to use in European pressure equipment. 254 SMO (1.4547 / UNS S31254) sits in the same 6 % molybdenum family but carries less nickel.
Is 1.4529 a stainless steel or a nickel alloy?
Metallurgically it is a stainless steel, a fully austenitic iron-based grade. Because its nickel content reaches 24 to 26 %, ASTM classifies it under nickel-alloy specifications such as ASTM B564 and ASTM B649 rather than the A182 stainless family. That is why it appears in the nickel alloy section of most supplier catalogues, including ours.
What is the PREN of 1.4529?
Using the standard formula PREN = %Cr + 3.3 x %Mo + 16 x %N and a mid-range composition of 20 % Cr, 6.5 % Mo and 0.20 % N, 1.4529 has a PREN of about 45. Depending on where the actual heat analysis falls in the specification range, published values run from 43 to 46. For comparison, 316L is around 25 and 904L around 35.
Can 1.4529 be hardened by heat treatment?
No. 1.4529 is a fully austenitic alloy and is not precipitation hardenable, so there is no ageing or quench-and-temper cycle. The only heat treatment applied to 1.4529 forgings is solution annealing at about 1100 to 1180 °C followed by rapid water quenching, which dissolves intermetallic phases and restores full corrosion resistance. Strength can only be raised by cold work, which is rarely used on forgings.
Which standards cover 1.4529 forgings?
ASTM B564 covers nickel-alloy forgings including UNS N08926, and ASTM B649 covers the bar and wrought product family. In Europe, EN 10088-3 covers bar and semi-finished product and EN 10222-5 covers forgings for pressure purposes. Ultrasonic testing is normally carried out to EN 10228-3, SEP 1921 or ASTM A388. The material is listed in NACE MR0175 / ISO 15156 for sour service subject to the stated limits.
What is the difference between 1.4529 and 904L?
1.4529 was developed directly from 904L (1.4539 / UNS N08904). The main change is molybdenum, which rises from about 4 to 5 % in 904L to 6 to 7 % in 1.4529, together with a nitrogen addition of 0.15 to 0.25 %. That lifts the PREN from roughly 35 to roughly 45 and gives markedly better resistance to chloride pitting and crevice corrosion in warm seawater. Both grades keep copper for reducing-acid service.
Is 1.4529 suitable for seawater and sour service?
Yes, within limits. With a PREN near 45, 1.4529 resists pitting and crevice corrosion in ambient and warm seawater far better than 316L or 904L, which is why it is used in desalination plants, seawater cooling, flue gas desulphurisation and offshore hydraulic and injection systems. It is also listed in NACE MR0175 / ISO 15156 for H2S-containing service, but the applicable temperature, chloride and partial-pressure limits must be checked against the standard for each project.
What size 1.4529 forgings can you produce?
Jiangyin Jiangnan Metal produces 1.4529 forgings from roughly 20 kg to 8,000 kg per piece. Typical envelopes are seamless rolled rings up to 3,000 mm outside diameter, forged discs and tube sheets up to 2,500 mm diameter, shafts and bars from 60 mm to 800 mm diameter in lengths to 6,000 mm, and flanges to DN 2000. Confirm the exact envelope for your drawing when you send an enquiry.
Who supplies 1.4529 forgings in China?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China that manufactures 1.4529 (UNS N08926) forged rings, seamless rolled rings, flanges, shafts, bars, discs, sleeves, bushings and tube sheets to customer drawings. Enquiries: sales@steelforgepieces.com, +86 189 2135 9659.
What certification do you supply with 1.4529 forgings?
Every 1.4529 forging is delivered with an EN 10204 3.1 mill certificate as standard, covering heat analysis, mechanical test results, heat treatment record and NDT report. EN 10204 3.2 certification counter-signed by a third-party inspection body such as TUV, SGS, BV, Lloyd's Register or DNV is available on request, as are intergranular corrosion testing to ASTM A262 Practice E and pitting testing to ASTM G48 Method A.
11 Request a quotation for 1.4529 forgings
Send a drawing or a dimension sketch and we will quote. To get a firm price and lead time in one round, include:
- Drawing or dimensions, and whether you want as-forged, rough-machined or finish-machined
- Quantity and target delivery date
- The governing specification, for example ASTM B564 UNS N08926, EN 10222-5 or a client spec
- Required NDT class (UT to EN 10228-3 class, or ASTM A388 acceptance)
- Certificate type: EN 10204 3.1, or 3.2 and which inspection body
- Any corrosion testing (ASTM A262 E, ASTM G48 A) or sub-zero impact requirement