X1NiCrMoCu25-20-5 (EN 1.4539 / UNS N08904 / 904L) Open-Die Forgings
Seamless rolled rings, flanges, shafts, discs, bars, sleeves and tube sheets, forged to drawing by Jiangyin Jiangnan Metal Co., Ltd., Jiangsu, China.
X1NiCrMoCu25-20-5 is the EN 10088 designation for material number 1.4539. The same super-austenitic stainless steel is sold worldwide as 904L or UNS N08904. With about 20% chromium, 25% nickel, 4 to 5% molybdenum and 1.2 to 2.0% copper it reaches a pitting resistance equivalent number (PREN) of roughly 43, and it is one of the few stainless steels developed for sulphuric acid service. Jiangyin Jiangnan Metal Co., Ltd. forges this grade as open-die and seamless rolled-ring products for chemical plant, seawater, offshore, fertiliser and pulp and paper equipment.
Grade data summary
- EN name / number
- X1NiCrMoCu25-20-5 / 1.4539
- UNS / AISI
- N08904 / 904L
- Forging standards
- EN 10250-4, EN 10222-5, EN 10272, ASTM A182 F904L
- Structure
- Super-austenitic, non-magnetic, not hardenable by heat treatment
- PREN
- about 43
- Density
- 8.0 g/cm³
- E-modulus at 20 °C
- 195 GPa
- Supplier
- Jiangyin Jiangnan Metal Co., Ltd., Jiangyin, Jiangsu, China
1. Equivalent grades
The alloy carries a different name in almost every national standard. For forgings the governing specification matters more than the name, because an EN 10250-4 open-die forging and an ASTM A182 F904L flange are inspected to different acceptance rules even though the chemistry is practically the same.
| Standard or region | Designation |
|---|---|
| EN, Europe | X1NiCrMoCu25-20-5, material 1.4539 |
| UNS, USA | N08904 |
| AISI / ASTM | 904L; ASTM A182 F904L for forgings |
| JIS, Japan | SUS 904L |
| BS, United Kingdom | 904S13 |
| AFNOR, France | Z2NCDU25-20 |
| SS, Sweden | 2562 |
| KS, Korea | STS 317J5L |
| Trade names | Uranus B6, NAS 255 |
2. Chemical composition
| Element | C | Si | Mn | P | S | Cr | Ni | Mo | Cu | N | Fe |
|---|---|---|---|---|---|---|---|---|---|---|---|
| min | - | - | - | - | - | 19.00 | 24.00 | 4.00 | 1.20 | - | Balance |
| max | 0.020 | 0.70 | 2.00 | 0.030 | 0.010 | 21.00 | 26.00 | 5.00 | 2.00 | 0.15 |
3. Mechanical and physical properties
3.1 Forgings, solution annealed
| 0.2% proof stress Rp0.2 | Tensile strength Rm | Elongation A | Hardness |
|---|---|---|---|
| ≥ 220 N/mm² | ≥ 490 N/mm² | ≥ 35 % | ≤ 90 HRB |
3.2 Plate values for comparison
| Rp0.2 min | Rp1.0 min | Rm | A5 min | ISO-V impact, transverse |
|---|---|---|---|---|
| 220 N/mm² | 260 N/mm² | 530 to 720 N/mm² | 40 % | ≥ 60 J |
3.3 Physical properties at 20 °C
| Density | Modulus of elasticity | Specific heat | Thermal conductivity | Electrical resistivity |
|---|---|---|---|---|
| 8.0 kg/dm³ | 195 GPa | 0.45 J/(g·K) | 12 W/(m·K) | 1.00 Ω·mm²/m |
4. Corrosion resistance
Buyers choose this grade for its corrosion behaviour rather than its strength. The high nickel content holds off chloride stress corrosion cracking, molybdenum and nitrogen carry the pitting and crevice resistance, and the copper addition is what separates 1.4539 from other super-austenitics, since copper improves behaviour in reducing acids.
Sulphuric acid. The grade was developed for sulphuric acid duty. The British Stainless Steel Association states that it can be used across the whole concentration range up to 35 °C. Above that temperature the safe concentration band gets narrower, so published iso-corrosion curves should be checked for the real service condition instead of assuming the grade is suitable everywhere.
Phosphoric, acetic and other organic acids. Good resistance over a wide concentration range, which is why 1.4539 is a standard choice in wet-process phosphoric acid plant and fertiliser production.
Chlorides and seawater. A PREN near 43 puts pitting and crevice resistance well above 316L. In warm seawater the crevice geometry and the chlorination regime still decide service life, so the grade is normally specified for seawater pumps and ballast valves rather than for stagnant immersion with tight crevices.
Intergranular corrosion. The 0.020% carbon ceiling keeps the grade resistant to intergranular attack as delivered and after welding, tested to ASTM A262 Practice E.
Forged surfaces should be pickled and passivated after heat treatment to remove scale and any chromium-depleted layer.
5. Forging and heat treatment
The alloy is fully austenitic and work hardens quickly, so it needs more press power than 304 or 316 and a tight temperature window to keep intermetallic phases out of the structure.
| Stage | Practice |
|---|---|
| Melting | AOD refined. VIM, VAR or ESR remelt where the enquiry calls for it |
| Forging temperature | Heat to about 1150 to 1180 °C, finish above about 950 °C |
| Reheating | Return to the furnace rather than forge on below finish temperature |
| Solution annealing | About 1050 to 1150 °C, hold, then rapid cooling in water or air |
| Hardening | Not possible by heat treatment. Strength rises only through cold work |
| Welding | Gas-shielded, arc and resistance welding, matching or over-alloyed nickel-base filler |
| Descaling | Pickle and passivate after final heat treatment |
6. Product range and sizes
We make the following X1NiCrMoCu25-20-5 items to customer drawing or to standard dimensions.
| Product | Range |
|---|---|
| Seamless rolled rings | OD 300 to 4,000 mm, height up to 1,000 mm |
| Forged flanges, weld neck, slip on, blind, orifice, special | To ASME B16.5, B16.47 or to drawing |
| Forged shafts, eccentric shafts, spindles | Length up to 8,000 mm |
| Forged discs, blanks, tube sheets | Diameter up to 2,500 mm |
| Forged round and square bar | 60 to 800 mm |
| Sleeves, bushings, hollow bar, forged tubes | Trepanned or mandrel forged bore |
| Valve bodies, stems, seat rings, blocks | Near net or rough machined |
| Single piece weight | 20 kg to 30 t |
| Delivery condition | Solution annealed. Black, rough machined or finish machined |
See also our seamless rolled rings, open-die forged parts and the full list of stainless steel forging grades.
7. Applications by industry
| Industry | Forged components | Reason for the grade |
|---|---|---|
| Chemical processing | Reactor rings, flanges, agitator shafts, nozzles | Sulphuric, phosphoric and organic acid service |
| Fertiliser production | Rolled rings, tube sheets, pump shafts | Wet-process phosphoric acid duty |
| Seawater and desalination | Pump casings, impeller hubs, valve bodies | Chloride pitting and stress corrosion resistance |
| Marine and offshore | Ballast gate valves, subsea housings, manifolds | Warm seawater performance |
| Oil and gas | Wellhead and Christmas tree parts, down-hole equipment | Combined chloride and acid exposure |
| Pulp and paper | Bleach plant rolls, shafts, rings | Resistance to chloride bleaching chemicals |
| Flue gas desulphurisation | Scrubber flanges, discs, liners | Acidic condensate carrying chlorides |
| Pharmaceutical and food | Crystalliser parts, polished shafts | Cleanable surface, low contamination risk |
8. Testing and certification
Every X1NiCrMoCu25-20-5 forging leaves the works with a test record. The standard scope is spectrometer analysis with ladle and product figures, tensile and hardness testing after solution annealing, ultrasonic examination to EN 10228-3, SEP 1921 or ASTM A388 at the class stated on the order, and dye penetrant examination to ASTM E165 on machined surfaces where the order requires it. Intergranular corrosion testing to ASTM A262 Practice E and sub-zero impact testing are available on request.
Certificates are issued to EN 10204 3.1, or to EN 10204 3.2 countersigned by a third party such as TUV, SGS, BV, LRS or DNV. PED 2014/68/EU documentation and NACE MR0175 / ISO 15156 compliance statements can be supplied where the application calls for them.
9. Questions we are asked
What is X1NiCrMoCu25-20-5 equivalent to?
It is the EN 10088 name for material 1.4539. The same alloy is sold as UNS N08904, AISI 904L, ASTM A182 F904L in forgings, JIS SUS 904L, BS 904S13, AFNOR Z2NCDU25-20, SS 2562 and KS STS 317J5L. Trade names include Uranus B6 and NAS 255.
Is X1NiCrMoCu25-20-5 a stainless steel or a nickel alloy?
A super-austenitic stainless steel. At 24 to 26% nickel it sits at the top of the stainless family and comes close to nickel-iron alloys such as Incoloy 825 in behaviour, but iron is still the balance of the composition.
What is the PREN of 1.4539?
About 43, from roughly 20% chromium, 4.0 to 5.0% molybdenum and nitrogen up to 0.15%. That is above 316L and below 6% molybdenum super-austenitics such as 1.4547.
Can 904L forgings handle sulphuric acid?
The grade was developed for sulphuric acid service. The British Stainless Steel Association states it can be used across the whole concentration range up to 35 °C. Above that the safe concentration band narrows, so temperature, concentration and any contaminants should be checked against iso-corrosion data before the grade is fixed.
At what temperature is X1NiCrMoCu25-20-5 solution annealed?
About 1050 to 1150 °C followed by rapid cooling in water or air. Published windows differ a little by source and product form, from 1060 to 1140 °C in European data sheets to 1090 to 1175 °C in some North American references. The grade cannot be hardened by heat treatment.
Which standards apply to forgings in this grade?
EN 10250-4 for open-die forgings in stainless steel for general engineering, EN 10222-5 for steel forgings for pressure purposes in stainless steels, EN 10272 for stainless bars for pressure purposes, and ASTM A182 F904L for forged flanges, fittings, valves and parts for high-temperature or high-pressure service.
What is the maximum service temperature of 1.4539?
Around 400 °C on mechanical grounds according to EN based data. In practice the grade is bought for wet corrosion duty at low to moderate temperature, not for hot strength. For hot service a nickel alloy is the better route.
What is needed to quote X1NiCrMoCu25-20-5 forgings?
A drawing or the main dimensions, the quantity, the governing specification such as EN 10250-4, EN 10222-5 or ASTM A182 F904L, the delivery condition, the ultrasonic test class required, and whether the order needs EN 10204 3.1 or third party 3.2 certification. Jiangyin Jiangnan Metal Co., Ltd. can be reached on +86-189-2135-9659 or at sales@steelforgepieces.com.
Request a quotation for X1NiCrMoCu25-20-5 forgings
Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Tel: +86-189-2135-9659
Email: sales@steelforgepieces.com
Send a drawing or the dimensions and we will come back with a price, the forging route and a delivery date.
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Figures on this page are taken from EN 10088-2, EN 10028-7 and ASTM A182 F904L limit values and from published mill data sheets for 1.4539. They are given for guidance and are not a guarantee of properties in a particular application. Page last reviewed , Jiangyin Jiangnan Metal Co., Ltd.