# X1NiCrMoCu25-20-5 (EN 1.4539 / UNS N08904 / 904L) Open-Die Forgings

Supplier: 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 | sales@steelforgepieces.com
Source page: https://www.steelforgepieces.com/Stainless-Steel/X1NiCrMoCu25-20-5.html
Last reviewed: 9 October 2026

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

| Item | Value |
|---|---|
| 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 |
| Modulus of elasticity at 20 C | 195 GPa |
| Supplier | Jiangyin Jiangnan Metal Co., Ltd., Jiangyin, Jiangsu, China |

## 1. Equivalent grades

| 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 |

For forgings the governing specification matters more than the name. 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.

## 2. Chemical composition, weight %, EN 10088-2

| 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 | Balance |

Where 1.4539 is ordered dual-certified to ASME SA-240 or ASTM A182 F904L, nitrogen is
normally held to 0.040 to 0.100% and sulphur may be accepted up to 0.030% under the
ASTM limit.

## 3. Mechanical and physical properties

Forgings, solution annealed, room temperature minimums to ASTM A182 F904L:

| 0.2% proof stress | Tensile strength | Elongation | Hardness |
|---|---|---|---|
| >= 220 N/mm2 | >= 490 N/mm2 | >= 35 % | <= 90 HRB |

Plate values to EN 10088-2 and EN 10028-7, up to 75 mm, for reference only. Plate
limits do not apply to forgings:

| 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 |

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 ohm.mm2/m |

## 4. Corrosion resistance

Sulphuric acid: the grade was developed for this duty. The British Stainless Steel
Association states it can be used across the whole concentration range up to 35 C.
Above that temperature the safe concentration band narrows, so iso-corrosion curves
should be checked against the real service condition.

Phosphoric, acetic and other organic acids: good resistance over a wide concentration
range, which is why the grade is standard 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, crevice geometry and 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 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

| Stage | Practice |
|---|---|
| Melting | AOD refined; VIM, VAR or ESR remelt on request |
| Forging temperature | Heat to about 1150 to 1180 C, finish above about 950 C |
| Reheating | Return to furnace rather than forge 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 by cold work |
| Welding | Gas-shielded, arc and resistance welding, matching or over-alloyed Ni-base filler |
| Descaling | Pickle and passivate after final heat treatment |

Slow cooling through roughly 650 to 950 C lets sigma and chi phases form in a 25%
nickel, 4 to 5% molybdenum alloy, and both toughness and corrosion resistance drop as
a result. Every ring, shaft and disc shipped in this grade is solution annealed and
rapidly cooled after forging.

## 6. Product range and sizes

| 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 | 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 |

## 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

Standard scope: 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 required. Intergranular corrosion testing to
ASTM A262 Practice E and sub-zero impact testing are available on request.

Certificates to EN 10204 3.1, or 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 available.

## 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 run
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. 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, the
delivery condition, the ultrasonic test class required, and whether the order needs
EN 10204 3.1 or third party 3.2 certification.

## Contact

Jiangyin Jiangnan Metal Co., Ltd.
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Tel +86-189-2135-9659
sales@steelforgepieces.com

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.