# 904L Forgings, UNS N08904 / EN 1.4539, to ASTM A182 F904L

**Manufacturer:** Jiangyin Jiangnan Metal Co., Ltd. — open-die forging factory
**Address:** No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
**Tel:** 0086-189-2135-9659 | **Email:** sales@steelforgepieces.com
**Page:** https://www.steelforgepieces.com/Stainless-Steel/904L.html
**Updated:** 29 September 2026

## Summary

904L (UNS N08904, EN 1.4539, X1NiCrMoCu25-20-5) is a non-stabilised low carbon high alloy austenitic stainless steel of roughly 20 % Cr, 25 % Ni, 4.5 % Mo and 1.5 % Cu. Copper gives resistance to reducing acids, sulphuric acid above all; nickel and molybdenum give resistance to chloride pitting, crevice corrosion and stress corrosion cracking. Jiangyin Jiangnan Metal Co., Ltd. forges 904L to ASTM A182 F904L as seamless rolled rings, flanges, discs, shafts, sleeves, bushings, tube sheets and shapes to drawing, with ultrasonic testing to ASTM A388, EN 10228-3 or SEP 1921 and certificates to EN 10204 3.1 or 3.2.

## Key data

| Item | Value |
|---|---|
| UNS number | N08904 |
| EN number | 1.4539 |
| EN name | X1NiCrMoCu25-20-5 |
| Forging specification | ASTM A182 / A182M F904L |
| Tensile strength, min | 490 MPa (71 ksi) |
| Yield strength 0.2 %, min | 215 MPa (31 ksi) |
| Elongation in 2 in., min | 35 % |
| Solution treatment | 1050–1150 °C (1920–2100 °F), liquid quench below 260 °C |
| Pitting resistance equivalent | about 35 |
| Certification | EN 10204 3.1 or 3.2 |

## Chemical composition (ASTM A182 F904L, weight %, balance Fe)

| Element | Limit | Typical heat |
|---|---|---|
| C | 0.02 max | 0.015 |
| Mn | 2.00 max | 1.5 |
| Si | 1.00 max | 0.4 |
| P | 0.04 max | 0.025 |
| S | 0.03 max | 0.001 |
| Cr | 19.00–23.00 | 20.0 |
| Ni | 23.00–28.00 | 25.0 |
| Mo | 4.00–5.00 | 4.5 |
| Cu | 1.00–2.00 | 1.5 |

Flat product specifications quote slightly wider P and S limits, so datasheets differ. For forgings the A182 F904L limits govern. Nitrogen typically runs around 0.10 %. Free machining additions such as lead or selenium are not permitted under A182.

## Mechanical properties, solution annealed

| Property | Metric | Imperial |
|---|---|---|
| Tensile strength, min | 490 MPa | 71 ksi |
| Yield strength 0.2 % offset, min | 215 MPa | 31 ksi |
| Elongation in 2 in., min | 35 % | 35 % |
| Reduction of area | not specified in A182 | — |
| Hardness | not specified in A182; 220 HBW max often ordered | — |

## Physical properties, annealed

| Property | Value |
|---|---|
| Density | 7.95 g/cm³ |
| Modulus of elasticity | 190 GPa |
| Thermal expansion | 15.8 µm/m·°C |
| Thermal conductivity | 11.5 W/m·K |
| Specific heat 0–100 °C | 450 J/kg·K |
| Electrical resistivity | 9.52 µΩ·cm |
| Magnetic response | non-magnetic in all conditions |

## Equivalent designations

| System | Designation |
|---|---|
| ASTM / AISI | 904L; forgings F904L |
| UNS | N08904 |
| EN number | 1.4539 |
| EN name | X1NiCrMoCu25-20-5 |
| France | Z2 NCDU 25-20 |
| United Kingdom | 904S13 |
| Sweden | SS 2562 |
| Trade names | URANUS B6, NAS 255, FO 25-20 U |

## Forging route and heat treatment

Billets are hot worked between about 950 and 1150 °C; working below 950 °C is avoided because the alloy becomes crack sensitive. ASTM A182 requires forgings to be cooled below 538 °C (1000 °F) after hot working, then solution treated at 1050–1150 °C (1920–2100 °F) and liquid quenched to below 260 °C (500 °F). Mill datasheets give the wider range 1090–1175 °C with rapid cooling. 904L cannot be hardened by thermal treatment.

Melting is by electric furnace with degassing and refining, by vacuum furnace, or by either followed by vacuum arc or electroslag consumable remelting. A182 limits products to 4540 kg (10 000 lb) each, above which austenitic forgings go to ASTM A965, and prohibits machining flanges, elbows, return bends and tees directly from bar stock.

## Corrosion behaviour and service limits

904L was developed for sulphuric acid and also performs in phosphoric and acetic acid, chloride bearing process water and warm seawater. Solution treatment after cold work is advised where stress corrosion cracking is a risk. It should not be used above about 550 °C because of sigma phase precipitation; ASME Boiler and Pressure Vessel Code design stress values run to 371 °C. Toughness holds into cryogenic service. In aggressive nitric acid it is weaker than molybdenum free grades such as 304L and 310L.

Welding is possible by all standard processes with matching filler such as ER385 to AWS A5.9. The alloy solidifies fully austenitic and is sensitive to hot c